# Accurate subwoofer levels



## Doctor X

Hi all,

I know that subwoofer levels, much like salt, is subject to taste, but who around these parts with ample woofage calibrate to 72-73 dB's flat with their main speakers in addition to running a flat room response ? 

I thought I would start a topic to get an idea of how many people around this forum set their systems up the way I've described. I mean, this is the ideal, isn't it ? For movie reproduction at least ? If we go by the books, a flat frequency response is needed and a flat calibration is required to achieve what was established in the mixing studio. Oh, and course, the required headroom and low distortion to achieve 121 dB peaks if all speakers are set to small.

I've set my system up in this way and I've found that if I run most of my bass intensive movies at anything less than -10 (calibrated flat ie 72-73 dB's with 75 dB level matched main speakers) with flat room response down to 16 hz) that I get no pressure sensation or sense that there is any real air movement. I can't feel anything at all unless I start to approach reference. 

Is this the way it's supposed to be for accurate reproduction ? I like to think that I have ample woofage and that my equipment is in no way a limiting factor so this discussion is then based purely on what our preconceived notions of what accuracy means. 

What are your thoughts ? 

Do you run your system this way ? Do you care for accurate reproduction ? Does it mean anything at all ? 

These are the questions I'm asking and I would like to know what you guys think. 

Thanks.

Best,
Vaugnan


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## tonyvdb

The Recommendations are to have your system set up to achieve 105db peaks from the mains and 115db peaks from a sub.
This means that at Reference level you should have set your system to 75db from the mains and 10db higher from the sub at 85db.


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## Doctor X

115 dB peaks if speakers are set to large. If set to small, that requirement increases as the bass is then redirected to the subwoofer. Subwoofer must then reproduce all the bass in each main channel as well as the LFE track.

This number is reflected in the 121 dB figure I posted above.

Regards,


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## tonyvdb

That is not correct, The standard recommendation and works very well if done properly is to set your crossover on the mains at 80hz and let the sub do all the rest below in essence this is a so called "small" setting. 
How are you setting your levels the only proper way to do this is sending pink noise to your speakers and using a db meter You cant measure peaks properly as this varries from movie to movie this is why you set your sub to 85db and your mains to 75db. newer receivers have built in room correction and setup sequences using a supplied mic but it is always good to dubble check these levels after it has finished because they usually dont get the sub level correct.


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## Doctor X

tonyvdb said:


> That is not correct, The standard recommendation and works very well if done properly is to set your crossover on the mains at 80hz and let the sub do all the rest below in essence this is a so called "small" setting.


I'm not sure what you are disagreeing with. What I am saying is that the redirected bass from each main channel amounts to a 6 dB value that, when combined with the LFE tracks requirement of 115 dB peaks (when speakers are set to large), equates to a 121 dB peak from the subwoofer. 



> How are you setting your levels the only proper way to do this is sending pink noise to your speakers and using a db meter


Yes, I understand that. All main speakers are set to 75 dB's with the subwoofer set to 72-73 dB's, all main speakers set to small, 90 hz crossover. I am using an SPL meter and pink noise from my AVR to set my levels. 



> You cant measure peaks properly as this varries from movie to movie this is why you set your sub to 85db and your mains to 75db.


What does your first statement have to do with the second ? 

Concerning levels, there is no need to up the bass 10 dB's over the mains. The LFE track is _preset_ (or, more accurately, the LF decoder) to play back dynamic peaks 10 dB's over and above the mains if the speakers are set to large as all main channels are full bandwidth. 

Speakers set to small are then alleviated with that burden and the bass information is then sent to the subwoofer which some will see as an additional burden. 

This information does not escape into the ether but is an additional burden; the subwoofer then must reproduce the bass in each main channel as well as the information in the LFE track. 

This discussion is being sidetracked by semantics. I simply want to know if people here are setting up their systems the way I described in my opening post and their opinions based on that configuration.

Regards,


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## thxgoon

I think you are correct that all levels should be set to 75db including the sub. The LFE track has an extra 10db of headroom for dynamic peaks but should still be set at 75 db. Out of curiosity, why do you set it to 72db?

Personally I have mine set about 3db hot and have eq'd the system to be as flat as possible. I like the sound but agree there is nothing really tactile until you get above -10db or so. This is probably the way it should be as the movies are mixed to be played at '0'. :bigsmile:


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## Doctor X

thxgoon said:


> I think you are correct that all levels should be set to 75db including the sub. The LFE track has an extra 10db of headroom for dynamic peaks but should still be set at 75 db.


I'm not saying that the levels should not be set to 75 dB's. What I am simply _trying_ to get across is that the _dynamic peaks_ (ie LFE track has 10 dB's greater headroom as you alluded to) are heightened when all the bass is redirected to the subwoofer. The requirements are no longer 115 dB bass peaks when speakers are set to small. 



> Out of curiosity, why do you set it to 72db?


Because any C-weighting SPL meter reads low at low frequencies. I use the Radio Shack SPL meter. Thus a 72-73 dB reading would equate to a 75 dB reading at the listening position.

Regards,


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## Ricci

When you calibrate your speakers to 75db the SW is also supposed to be set at 75db, but most seem to kick it up a notch. I've been running mine 5db hot (calibrated to 80db roughly). I think that is about average. If you set it at the same level it is usually underwhelming at low to moderate volumes.

It would help if we knew what subs were being used by each person also. If you have a smaller sub you may not want to boost it's level up above the mains because it may not be able to handle the peaks when you are listening at a loud level.


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## Doctor X

Ricci said:


> When you calibrate your speakers to 75db the SW is also supposed to be set at 75db, but most seem to kick it up a notch.


But it's not "supposed to" be set at that level. A 75 dB level using test tones will yield a higher level using any C-weighted device. 

Which is fine. I mean, it's personal preference, since then you would have a 2 maybe 2.5 dB's level increase above flat. Which, again, is perfectly fine but I'm talking about a proper flat calibration.

If we go by the books and want an accurate translation of what was recorded then equal levels and a flat room response is required. At least according to SMPTE requirements.

What this thread is about, what I'm trying to ask is, do people run their systems this way here and what do people have to say about a proper accurate setup. Many people will bump up the subwoofer level in addition to have a peaky room curve. 

We've all been there, I'm sure on that, but for those that want a faithful reproduction of the soundtrack it's hardly a step in the right direction, IMO.



> I've been running mine 5db hot (calibrated to 80db roughly). I think that is about average. If you set it at the same level it is usually underwhelming at low to moderate volumes.


If it's 80 dB's then it's closer to 6.5-7 dB's hot. That's fine. Then if you calibrate levels and use 0 for reference, you would achieve theatrical levels in the bass range at -7 to -8 MV. This also depends on your room curve. 

Regards,


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## thxgoon

Vaughan100 said:


> But it's not "supposed to" be set at that level. A 75 dB level using test tones will yield a higher level using any C-weighted device.
> 
> Which is fine. I mean, it's personal preference, since then you would have a 2 maybe 2.5 dB's level increase above flat. Which, again, is perfectly fine but I'm talking about a proper flat calibration.
> 
> If we go by the books and want an accurate translation of what was recorded then equal levels and a flat room response is required. At least according to SMPTE requirements.
> 
> What this thread is about, what I'm trying to ask is, do people run their systems this way here and what do people have to say about a proper accurate setup. Many people will bump up the subwoofer level in addition to have a peaky room curve.
> 
> We've all been there, I'm sure on that, but for those that want a faithful reproduction of the soundtrack it's hardly a step in the right direction, IMO.


I think most just set their subs to the 75db mark neglecting the sensitivity of the meter and adjust from there. I know I always have. It depends so much on room placement and interactions that it's pretty much impossibls to achieve a ruler flat response for most people. Additionally, I've never been in or know of a movie theater (besides one) which can achieve the low frequencies we all try to achieve at theatrical levels for all listeners. The fact is, a great many of our home theaters out perform any commercial venue.

That said, I think responses on this post so far have been in reference to your question in that most prefer a slightly greater amount of bass. As Ricci said this is probably because we rarely listen at reference and our hearing is less sensitive to bass at lower volumes. I personally don't think the sought after ruler flat response exists... there are just too many variables and others besides frequency response.


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## DougMac

I have an SVS PB-12 NSD. Using an SPL meter and test tones, I set it flat to the mains (75db mains, 75 db sub).

I experience the same situation as the OP, as I understand him. At low listening levels, the sub output may seem a little low. When I turn up to "movie listening level", things start to get interesting. If I crank the volume, the sub really shines!

Most of the time I don't bother adjusting for low level listening. My remote has a convenient sub toggle that allows me to increase/decrease sub volume. On occasion, I might bump up +3db. I will also adjust for variances in source.

I'm not **** about accuracy, but I find I prefer the sound when things are pretty close to flat. We're not big action movie fans, so reproduction of booms and crashes isn't high on our priority list.

Everything is about to change. The sub is currently in our great room, which has cathedral ceilings. They come next Thursday to install carpet in our dedicated HT, which is 16wx18dx9h. I'm sure the PB-12 will be able to approach reference levels in its new home. I can't wait!

Doug


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## Doctor X

thxgoon said:


> That said, I think responses on this post so far have been in reference to your question in that most prefer a slightly greater amount of bass.


Fair enough. I would expect many to up the bass levels as most don't watch their movies at reference levels, and, of course, our ears lack of sensitivity to low frequencies. 

But to recreate the feeling that the mixing engineer had in his studio and, indeed, to capture the directors vision, as it were, is to adhere to tight tolerances, does it not ?

The question then becomes, why have standards at all for movie reproduction ? And I know most don't follow that train of thought for numerous reasons, but I was wondering if there are those that *do* run their systems the way I described. 

Because I've tried it and I'm not sure if I like it. Perhaps in time, but right now, on the films I've tried, it actually sounds lifeless.

Regards,


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## thxgoon

Ya I hear ya. My first system I had I did everything possible to achieve perfect response and acoustics. It sounded great, but was pretty dull and never impressed my friends. That has changed now:bigsmile::bigsmile:

I thought of another reason we all probably end up cranking our subs. When we set levels with a meter we usually use some form of noise which is a spectrum of frequencies playing simultaneously. If there happens to be a room related peak in response, this peak is what the meter will read and consequently what we will set our sub to. That bumps all of the other frequencies down much below where they belong and the sub sounds too quiet.

Agreed that to feel what they had in the studio you need to adhere to some standards to get there. But IMHO, those standard will only get you about 90% of the way to great sound. Even taking the exact same system and just changing the wall it is on can have a big impact on the sound. Other things like room acoustics have a large impact on the sound even no change in the requency response. Sonic nirvana is so illusive!


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## Doctor X

I'm in complete agreement with you. 

Regards,


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## Ricci

How do you set your levels Vaughan? Does Cweighting only affect the bass range?

I'm not one to really stress too much about details. There will never be a flat frequency response in room, especially not at more than one position. Also most movie theaters have sound systems that aren't that great. The Engineers that score the film are not guaranteed to have an incredible dynamic and flat sound system, with a great room either. I'm sure that some do, but not all.


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## Doctor X

Ricci said:


> How do you set your levels Vaughan? Does Cweighting only affect the bass range?


I set each main speaker to 75 dB's with the Radioshack SPL meter. C-weighting does affect the bass range. The Radioshack meter is accurate enough to level match speakers but when used in the subwoofer range, it's not, hence the reason why many use a sound card calibration curve to offset this inaccuracy when testing a full band response.



> I'm not one to really stress too much about details.


Therein lies the difference between us. I do. 



> There will never be a flat frequency response in room, especially not at more than one position.


Granted. 



> Also most movie theaters have sound systems that aren't that great. The Engineers that score the film are not guaranteed to have an incredible dynamic and flat sound system, with a great room either.


This may or may not be true. I'm sure that most studio's worth their salt are fitted with systems with more than sufficient levels of dynamics and clean output to offset the acoustic treatment required to achieve the correct RT60 levels and to attain the level of absorption in the low bass range.

Cheers,
Vaughan


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## thxgoon

Vaughan100 said:


> This may or may not be true. I'm sure that most studio's worth their salt are fitted with systems with more than sufficient levels of dynamics and clean output to offset the acoustic treatment required to achieve the correct RT60 levels and to attain the level of absorption in the low bass range.


Oooooo, wouldn't that be nice to have at home :daydream:


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## Doctor X

Yep, would be nice to have that power. I think I'm more than sufficient in terms of low bass extension (solid to 16 hz) and overall power in the bass range. I have dual MFW-15's. I am not using both of them at the moment as the one amp is faulty. So unfortunately my review has been put on hold.

I suppose I could leak a pic of mine setup in the lounge for now (  ) :


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## thewire

Is that the beginning of Star Wars EP2 in that pic? Looks like a great setup, sorry to hear about your subs problem.

I am somewhat confuzzed here. A subwoofer plays at 115dB max here on a film. Right then. For this reference then I will use an example in Transformers on HD-DVD which seems to be the most practical example I have. A peek in War Of The Worlds DTS is higher but for all intensive purposes, this 
movie has a good amount of bass also so I will use that as an example. First off, I am trying to figure out how to play reference level. For this lets disregard flatest response, best looking waterfall, spaciousness, correct settings, all that good important stuff. If they work, great, but my question is about SPL and accurate levels. :whistling: 

I read about all this peeks and I want to know what this has to do with a calibration and response. If for example someone has a calibrated system setup identical to mine but with larger, lower sounding subs are they going to have the "true reference level" of 115dB peeks and I will not? Without all that lower extention than this would account for in my system being more like a 105dB peek or lower? If I setup my subwoofers using AVIA 2 for example to 89dB in my front row and 85dB in the back row, then play the movie (scene of transformer flying over the lady) I get like a 108dB peek with sub location being most optimized for a flat response. If I did this the other way with them on each mid-wall location, it might be a little higher since the lower output appears to go up, but I don't think it is going to be 115dB. Adjusting the volume level higher on the subwoofers seems to do very little to the measured peek. So I am thinking that to measure a peek in a movie with C-Weighting there might be some added amount for correction, but I don't recall or know what this amount would be. If you know, please fill me in. To get a 116dB peek in this scene, I have to go to quite some extremes. I have to raise the level on my subs from the 12:00 to 3:00 position AND I have to co-locate each on the front walls corners. :surrender:

There is no volume adjustment to be made on my source, an XA2 DVD player since this is maxed out at zero. How does one determine the correct measurement of a peek in a movie and is there a way to determine if it is accurate to the level of a reference level setting? Is exploding conccrete, flying robots, not supposed to be a max level comming from a subwoofer in this circumstance? Is it just because my subwoofers are lacking?


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## Doctor X

thewire said:


> Is that the beginning of Star Wars EP2 in that pic? Looks like a great setup, sorry to hear about your subs problem.


Yep, the famous Star Wars Episode 2 starship flyby. Even to this day, it is a fantastic bass demo. Yeah, I'm sorry about the bum amp too, but what I'm getting from a single MFW-15 is easily in the 2.5-3 times clean output territory compared to a single SVS PB10-ISD (which I owned for several months). 



> I read about all this peeks and I want to know what this has to do with a calibration and response. If for example someone has a calibrated system setup identical to mine but with larger, lower sounding subs are they going to have the "true reference level" of 115dB peeks and I will not?


It's all about clean headroom and low extension (and distortion). If you calibrate your subwoofer properly and have sufficient headroom you should hit 115 dB's maximum with a flat room curve (speakers set to *large*). 

With a given subwoofer you may achieve reference level down to 40 hz when set properly. But not down to 20 hz as cone excursion requirements quadruple with every halving of frequency. To be able to hit 115 dB's in the LFE track down to 20 hz at the listening position (if the content requires it) is no mean feat.

That isn't to say that there will be content like this but it's good to have a subwoofer that could momentarily handle peak output demands very low in frequency to maintain low distortion.



> Without all that lower extention than this would account for in my system being more like a 105dB peek or lower?


For all I know your system might achieve 105 dB peaks within it's respective bandwidth but not all the way down in the frequency range. Even hitting 115 dB peaks at 40 hz is not easy if your listening position is at least 3-4 meters from the subwoofers. This calls for a 5-7 dB loss (note inverse square low doesn't apply here ).



> If I setup my subwoofers using AVIA 2 for example to 89dB in my front row and 85dB in the back row, then play the movie (scene of transformer flying over the lady) I get like a 108dB peek with sub location being most optimized for a flat response.


Don't you get phase errors setting up your system this way ? You could still achieve some level of co-location even if both subwoofers are set up at the same level but spaced apart. You just won't get the full benefit up to the 1/4 wavelength distance that mostly will affect the crossover range. 



> If I did this the other way with them on each mid-wall location, it might be a little higher since the lower output appears to go up, but I don't think it is going to be 115dB.


What subwoofers do you have ? Have you tried putting both subwoofers on top or side by side and calibrate to the same exact level to ensure that voltage gain from both are identical ? Otherwise one subwoofer might bottom before the other and the benefits of greater clean output have been negated.



> Adjusting the volume level higher on the subwoofers seems to do very little to the measured peek.


Keep in mind that it is possible that your subwoofers are compressing at these levels which might explain why your SPL meter doesn't read higher. 



> So I am thinking that to measure a peek in a movie with C-Weighting there might be some added amount for correction, but I don't recall or know what this amount would be.


Correction on the SPL meter varies with frequency. At 20 hz I think it's around 7.5 dB's. It's difficult to correct for a full bandwidth signal containing many frequencies. 



> If you know, please fill me in.


I could help you for single frequencies but an AC signal does not contain only single band frequencies hence it wouldn't be useful to apply it.



> To get a 116dB peek in this scene, I have to go to quite some extremes. I have to raise the level on my subs from the 12:00 to 3:00 position AND I have to co-locate each on the front walls corners.


How is your system set up ? Speakers set to large ? Small ? Crossover setting ? 



> There is no volume adjustment to be made on my source, an XA2 DVD player since this is maxed out at zero. How does one determine the correct measurement of a peek in a movie and is there a way to determine if it is accurate to the level of a reference level setting?


I'm sure Ilkka can be of more assistance here.  One would need to measure this . 



> Is exploding conccrete, flying robots, not supposed to be a max level comming from a subwoofer in this circumstance? Is it just because my subwoofers are lacking?


It could be that your subwoofers are compressing. For example, in LOTR Return of the King, Frodo is about to drop the ring into fires of Mount Doom. Soon after this, we get to hear and feel his heartbeat. There is a lot of high energy 20 hz content here. It continues for the duration of the scene and even gets a little higher towards the last heartbeat. 

If a subwoofer can't reproduce that high level 20 hz content then it will simply taper off the response and go into compression mode, excessive port noise or worse, distort pretty badly. This is just an example. If signal peaks require a given output and you can't achieve that output then you will get compression.

Pulse is another great example of a movie with below 20 hz content at very high levels. The actual recorded level is high. Chances are, you might not even get to experience all the bass in that particular scene. 

A ****** film no doubt, but for bass, it's one of the best I know of.

Cheers,
Vaughan


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## Ricci

Just because you are listening at the REF level setting on your system, whatever that may be, does not mean that the engineers had the levels close to 0db at any time during the particular scene. Just because there's an explosion or other loud event doesn't mean that it's going to use all of the available headroom. There may be an even bigger event later on that is intended to be even more impressive. Reference level is supposed to let you listen at the overall volume level that the sound engineer intended. It does not mean that you should be getting 115db peaks necessarily. You should have the capability of it if the soundtrack has been supplied with it.

Vaughan,
Most SPL meters, or mics roll-off in the bass and will read lower than the actual level. The C-weighting will make the meter roll off the bass a bit. These 2 kind of cancel each other out. the C weight will cause you to be about 2 db hotter at 40-50hz than you think you are, but your meter or mic will counteract this to some extent. I use the CM-140 and it is supposed to be down about 1db at 50hz and almost 2db by 40hz. So in reality I'm probably 1 db, or less hotter than the meter says. Hence me being about 5 to 6db hot when calibrated to 80db (75db for the mains). Wait a minute...it seems that they would compound each other after thinking about it...hmmm.

Is there any standard for the tones used in processors & recievers for setting levels? They are pink noise, but what frequencies are present in them? SW tone especially?


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## tonyvdb

Ricci said:


> Is there any standard for the tones used in processors & recievers for setting levels? They are pink noise, but what frequencies are present in them? SW tone especially?


My understanding is that pink noise is full frequency 20-20,000Hz, White noise on the other hand is much less at about 400-12,000Hz


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## Doctor X

Ricci said:


> Just because you are listening at the REF level setting on your system, whatever that may be, does not mean that the engineers had the levels close to 0db at any time during the particular scene. Just because there's an explosion or other loud event doesn't mean that it's going to use all of the available headroom.


I agree.



> Reference level is supposed to let you listen at the overall volume level that the sound engineer intended. It does not mean that you should be getting 115db peaks necessarily.


Again I am in agreement with you.



> You should have the capability of it if the soundtrack has been supplied with it.


No disagreements here.

Regards,


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## thewire

Great replies and very helpful. This has had to be one of the most confussing things for me. My speakers are set to small and they are THX12 SUB's by Crystal Audio and Video. I have a DIY center channel subwoofer that I didn't mention being used in the experement but it had done nothing more than even out a null a couple Hz wide and about 10dB low. It bottoms out really quick and made no difference to the SPL when I tried that at no matter what level of setting. Switching the speakers to large adds +5dB signal to the subwoofer output and eleminates all crossover noise, in which I would probobly be using my BFD at this time if I were to do so. Extention on mains are good to 30Hz.


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## thewire

Almost forgot. Yes they were stacked on eachother with a subudude between them. I have tried all areas of placement. I tried also on each side of the left and right speakers and have had similar results in SPL. If I recall correctly, the results were about the same, but I had more difficulty getting them in phase. Without using a test CD and measuring each manually with REW, or using another device, I cannot check the integration to the mains, but it looked fine when I was able to test using my reciever when I had one.


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## Ricci

tonyvdb said:


> My understanding is that pink noise is full frequency 20-20,000Hz, White noise on the other hand is much less at about 400-12,000Hz


Ohh boy. 

So if this is the case then the sub will be putting out 20hz up through the crossover (80hz) plus some higher freq's at a rolled off level. Wouldn't your subs response have an impact on the meter reading? Let's say that you have 2 different subs in the same exact location in the same room, but one is extended down well below 20hz and the other rolls off rapidly from 30hz. Wouldn't this cause the 2nd sub to be calibrated a bit louder in the upper bass because the lower freq's output were missing and thus not contributing to the 75db level at the meter? 

Then there's the impact of the C weighting and SPL meter inaccuracy at the low end, which may cause you to be 3db or more hotter than is apparent with your sub level, as Vaughan alluded to earlier.


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## Doctor X

tonyvdb said:


> My understanding is that pink noise is full frequency 20-20,000Hz, White noise on the other hand is much less at about 400-12,000Hz


The subwoofer test tone has most of it's energy centered in-between 40-80 hz. Pink noise used for setting speaker levels is much higher up the frequency scale as it's not a full bandwidth signal. 

Regards,


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## tonyvdb

Vaughan100 said:


> The subwoofer test tone has most of it's energy centered in-between 40-80 hz. Pink noise used for setting speaker levels is much higher up the frequency scale as it's not a full bandwidth signal.
> 
> Regards,


Pink noise is 20-20,000Hz and is the industry standard for testing levels in all speakers ranges including subs. Your crossover will determine what the cut off is for the pink noise frequencies that are sent to your speakers or subwoofer.
I have an external pink noise generator made my Audio control and it sounds no different when passed through the receiver to the sub you still only hear what the sub is capable of outputting (usually below 80Hz if that is where you have the crossover set to).


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## thxgoon

Ricci said:


> Ohh boy.
> 
> So if this is the case then the sub will be putting out 20hz up through the crossover (80hz) plus some higher freq's at a rolled off level. Wouldn't your subs response have an impact on the meter reading? Let's say that you have 2 different subs in the same exact location in the same room, but one is extended down well below 20hz and the other rolls off rapidly from 30hz. Wouldn't this cause the 2nd sub to be calibrated a bit louder in the upper bass because the lower freq's output were missing and thus not contributing to the 75db level at the meter?
> 
> Then there's the impact of the C weighting and SPL meter inaccuracy at the low end, which may cause you to be 3db or more hotter than is apparent with your sub level, as Vaughan alluded to earlier.


Yes and no. The SPL meter is going to register the loudest sound it is receiving, whatever frequency that would happen to be. So depending on your room response, listening position and sub the measurement could change.


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## Doctor X

thxgoon said:


> Pink noise is 20-20,000Hz and is the industry standard for testing levels in all speakers ranges including subs.


If I set my speakers to large (capable down to, let's say, 40 hz) and play the test tones from my AVR are you telling me that I should be hearing bass down to the cut off of my speaker ? Because that simply isn't the case.

The subwoofer warble tone has predominant energy in the 40-80 hz region. 



> Your crossover will determine what the cut off is for the pink noise frequencies that are sent to your speakers or subwoofer.


Even if all main speakers are set to large (hence no crossover) the test tone frequencies are more like from 300 hz and up. Nothing resembling lower bass. Unless I'm completely overlooking something or perhaps I'm just dense today, I don't agree with you. 

Convince me.

Regards,


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## tonyvdb

Vaughan100 said:


> Even if all main speakers are set to large (hence no crossover) the test tone frequencies are more like from 300 hz and up. Nothing resembling lower bass. Unless I'm completely overlooking something or perhaps I'm just dense today, I don't agree with you.
> 
> Convince me.
> 
> Regards,


Its simply that your receiver is not using pink noise it is simply a test noise signal nothing more good for hearing if your levels are good but not really for setting accurate EQ levels if your trying to set a flat frequency response. If you use real pink noise you will hear the difference immediately. There are many DVDs and Test CDs that have pink noise test tracks. Avia or Digital video essentials setup DVDs are good ones to have for this purpose.


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## thxgoon

Vaughan100 - I don't think I was the one to mention the pink noise standard, but you got me looking around. 

According to Wikipidia (which isn't the end all be all) 

_"Pink noise or 1/f noise is a signal or process with a frequency spectrum such that the power spectral density is proportional to the reciprocal of the frequency. Pink Noise has an equal amount of energy per octave. The name arises from being intermediate between white noise (1/f0) and red noise (1/f2, more commonly known as Brownian noise). Within the scientific literature the term 1/f noise is used a little more loosely to refer to any noise with a power spectral density of the form,"_









So, by this definition the lowest frequencies would actually have the greatest intensity and the meter should register the 20hz tone. Now of course I'm all confused. Pink noise is created to approximate the human response to inensity vs frequency. Does the SPL meter as well or does it read flat? Must look more into this......:scratch:


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## thxgoon

Google is awesome... here is a graph plotting the different response of A and C weighting.










To quote Rane.com

_"A-weighting (not official but commonly written as dBA) The A-curve is a wide bandpass filter centered at 2.5 kHz, with ~20 dB attenuation at 100 Hz, and ~10 dB attenuation at 20 kHz, therefore it tends to heavily roll-off the low end, with a more modest effect on high frequencies. It is the inverse of the 30-phon (or 30 dB-SPL) equal-loudness curve of Fletcher-Munson"

"C-weighting (not official but commonly written as dBC) The C-curve is "flat," but with limited bandwidth, with -3 dB corners of 31.5 Hz and 8 kHz, respectively."_

So it appears that the SPL meter set to C weighting will be most sensitive to frequencies of about 40-50 hz with true pink noise.


----------



## thewire

My XA2 and DVE are so busted. I caught them red handed. 89dB went to 79dB today then stopped sending a signal to the subs all together. I put in a movie and the subwoofers played fine. I will try updating my XA2 firmware. :scratch:


----------



## Doctor X

tonyvdb said:


> Its simply that your receiver is not using pink noise it is simply a test noise signal nothing more good for hearing if your levels are good but not really for setting accurate EQ levels if your trying to set a flat frequency response.


I know that, that's why I asked for clarification. I thought that the poster assumed the test tones used was the actual pink noise itself which it is not. 



> If you use real pink noise you will hear the difference immediately. There are many DVDs and Test CDs that have pink noise test tracks. Avia or Digital video essentials setup DVDs are good ones to have for this purpose.


I have Video Essentials but, truth be told, I've never used it for calibrating the audio side of my system. I have heard a wide range of opinions concerning the test tone accuracy in the average AVR. I've found the consensus to be that the tones in the AVR _are_ accurate enough for calibrating an audio system.

Regards,


----------



## Ricci

This has turned into a good discussion:bigsmile:. 

I'm assuming that there is no standard for test tones built into reciever's or pre/pro's:rolleyesno:? Is it just white noise usually then, if not pink? The subwoofer tone out of my Outlaw has a lot of energy lower than 40hz-80hz. I can tell because at an 80db level I can see the cone (ported 18") moving a bit which it would not do with 40 or even 30hz signals at that level. 

I think I'm going to turn down my SW level 2 or 3db, to get closer to a true +5db hot. Think I'll use the Avia disc this time.


----------



## tonyvdb

Ricci said:


> I think I'm going to turn down my SW level 2 or 3db, to get closer to a true +5db hot. Think I'll use the Avia disc this time.


It is a known fact that the Avia DVD test pink noise is 10db to low so you will need to raise your levels to 85db in order to achieve 75db. This was corrected in the latest BluRay version. If you have the Digital video essentials DVD that has the proper levels.


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## Doctor X

> I'm assuming that there is no standard for test tones built into reciever's or pre/pro's? Is it just white noise usually then, if not pink? The subwoofer tone out of my Outlaw has a lot of energy lower than 40hz-80hz.


Sure, but like I said, I _believe_ that the subwoofer test tone has most of it's energy predominantly in the 40-80 hz frequency range. I think I'm correct on this. Now that isn't to say that there might be some low level signal at 30 hz, or ****, maybe even slightly below that (doubtful) but most of it is not centered there.

Regards,


----------



## tonyvdb

This is why receivers that have Audyssey don't use the test tones to do its setup it uses a full frequency sweep (sounds like a "woop") to get its levels.


----------



## tcarcio

tonyvdb said:


> It is a known fact that the Avia DVD test pink noise is 10db to low so you will need to raise your levels to 85db in order to achieve 75db. This was corrected in the latest BluRay version. If you have the Digital video essentials DVD that has the proper levels.


I am missing something. How can the pink noise be 10db too low when it is the meter that measures the sound. Don't you just adjust the speaker level to get 75db. ?


----------



## tonyvdb

tcarcio said:


> I am missing something. How can the pink noise be 10db too low when it is the meter that measures the sound. Don't you just adjust the speaker level to get 75db. ?


I understand how confusing this sounds it confuses me all the time,
To get 75db using Avia you would have to turn up your receiver higher than it is supposed to be so to compensate you need to set your levels so that the db readings are at 85db on your meter then when your receiver is at 0db on the volume scale you have the proper "reference" level. If you were to set it like normal using Avia your levels would be to low at 65db.


----------



## Doctor X

tcarcio said:


> I am missing something. How can the pink noise be 10db too low when it is the meter that measures the sound. Don't you just adjust the speaker level to get 75db. ?


The meter reads the sound pressure fluctuations but the signals are recorded low. It's like the tones in your AVR are recorded at -30 dB's below full scale; full scale representing maximum peaks. So setting the tones to a 75 dB level means that you then have -30 dB of dynamic peaks which may or may not be used at any given moment. 

But if this untapped dynamic range is suddenly utilized then it helps to have the headroom necessary to achieve it with low distortion. The full bandwidth of each main channel is from 20 hz to 20 kHz (or is it from 5 hz ? ) but the maximum peak demands are 105 dB's. I find this interesting because some waterfall charts I've seen have info extending well below 20 hz in some main channels unless it was a glitch in the mixing chain.

THX receivers have their test tones recorded higher if I'm not mistaken to 85 dB's. I may be wrong on that so if anyone can confirm this then please correct me. But still, this pretty much amounts to the same value; the tones are recorded at -20 dB's below full scale which means that the peak levels will still be 105 dB's (maximum) within the playback chain if the mixer decides to max out the channels full dynamic range.

Regards,


----------



## thxgoon

Vaughan100 said:


> THX receivers have their test tones recorded higher if I'm not mistaken to 85 dB's. I may be wrong on that so if anyone can confirm this then please correct me.


My THX receiver is intended to be set to 75db and I think this is the case for all of them. It may depend on the make but would mention it in the manual.



> It is a known fact that the Avia DVD test pink noise is 10db to low so you will need to raise your levels to 85db in order to achieve 75db


I bet this is a predominant source of the confusion...

As far as energies at different frequencies, if the source is indeed pink noise the most powerful frequency will be the lowest one the subwoofer can achieve. If I get time later I'll use REW to take a spectro of some noise from my receiver and from a test disk.


----------



## tcarcio

tonyvdb said:


> I understand how confusing this sounds it confuses me all the time,
> To get 75db using Avia you would have to turn up your receiver higher than it is supposed to be so to compensate you need to set your levels so that the db readings are at 85db on your meter then when your receiver is at 0db on the volume scale you have the proper "reference" level. If you were to set it like normal using Avia your levels would be to low at 65db.


Got it.:T Thanks for explaining .


----------



## Ricci

thxgoon said:


> As far as energies at different frequencies, if the source is indeed pink noise the most powerful frequency will be the lowest one the subwoofer can achieve. If I get time later I'll use REW to take a spectro of some noise from my receiver and from a test disk.


That'd be great! 

Tony,
Thanks for the Avia reminder:T. 

So what level is everyone running their subs at?


----------



## tonyvdb

Ricci said:


> That'd be great!
> 
> 
> So what level is everyone running their subs at?


I run my PB 13 Ultra at 85db using my Galaxy 140 meter. My room is fairly large at 15x35' and acoustically fairly dead so I need it run a little hot.


----------



## Doctor X

tonyvdb said:


> I run my PB 13 Ultra at 85db using my Galaxy 140 meter.


I was contemplating buying the Galaxy 140 meter as I have the Radio Shack model but I found that it's basically just as accurate as the RS meter as a C-weighting device reading pink noise. However the 140 tracks _very well_ at low frequencies and this is where the RS meter fails miserably. 

Regards,


----------



## bobgpsr

IIRC for some posts 4 years back on a big forum, that AVIA was OK and that with DVE you needed to calibrate +10 dB hotter. Something about the frequency spectra of the bass pink noise used. I'd have to dig for the technically authoritative post that put this matter to rest. At that time a lot of users were unhappy with the bass levels resulting from using DVE when they exactly followed the directions. Did not seem to be a problem with AVIA. This was with the standard definition calibration DVDs. I've used the AVIA SD DVD and am happy with the results.

I did buy DVE in the HD DVD format and seemed to have a hard time getting enough bass drive. Of course I needed to get an external +15 dB bass boost from the analog outputs of a HD-XA2 which did not do (as many players and AVRs do not on the analog multichannel connection) the +10 dB LFE channel boost. Add + 5 dB more for the 80 Hz bass management re-direction from setting the mains to small. I did the +15 dB boost at the SVS PC Ultra input level control when using multichannel connection and then went back and had the AVR re-calibrate the audio levels when using a digital S/PDIF connection. The AVR's (Yamaha RX-V2500) cal reduced the bass level appropriately to the PCU when using anything other than the multichannel analog connection.

Oh, and the HD-XA2 had to have PCM selected for the S/PDIF audio output in order to have anywhere close to correct bass management on the multichannel analog outputs (kinda a XA2 bug).


----------



## Mike P.

> I was contemplating buying the Galaxy 140 meter as I have the Radio Shack model but I found that it's basically just as accurate as the RS meter as a C-weighting device reading pink noise. However the 140 tracks very well at low frequencies and this is where the RS meter fails miserably.


There is a correction file for the RS meter. Have you used it?


----------



## thewire

bobgpsr, I have found after using AVIA to calibrate levels that the reading in DVE was 89dB instead of 79dB. I discovered this after a couple weeks when I recovered the disc from a player I left it in and forgot about. I had rented the AVIA 2 disk on Netflix. I then did some very very slight messing around with REW and matching each of my subwoofers and it went back to 79dB. If I move a volume level on any of my subwoofers a fraction of a mm the level changes so I cannot be sure, but I think somehow that DVE may have gone to 79dB again somehow because the level in the XA2 detected the validity of the LFE track and made the appropriate -10dB adjustment. As far as the XA2 not boosting the level itself for the subwoofer, this I think is correct. When I used one subwoofer I had to raise the volume level to max to get a 75dB pink noise in DVE. When I had used my AVR it was pretty simple to get a 85dB target or higher with the max volume level. My AVR however did not have the ability of needing the additional +5dB boost, so I had to boost that on the subwoofer. Made me look bad in the REW forum. Right now I have each subwoofer set to near 85dB in REW but they are at the approximate same position as before at 12:00 and my soundcard was calibrated for 85dB. I have to lie to the REW SPL meter or post graphs that look like an 89 target to get it setup correctly. Total it should be somewhat close to 79dB in DVE because each subwoofer adds enough gain to make up for the additional +5dB boost needed. As far as how my DVE went from 89dB to 79dB and then also stopped sending a signal, I may never know what caused that. Maybe AVIA and DVE use similar HD-DVD flags and it got confussed. Regardless my THX optimizer is the same level as the AVIA 2 disc so I can always check that. The THX optimizer which I had on hand was 89dB after calibration with AVIA 2 and is now also 79dB in DVE, so I know its good. It got pretty complex IMO.


----------



## Doctor X

Well, I got my replacement amplifier today, opened the box and to my disappointment, the side of the plate amp is really bent. I won't be able to get a snug fit because of this. Oh well, yet another two week wait as I get another amp.  This is a bit frustrating. The packaging was great but the amp looked like it was B-stock.

Anyways, after getting the second subwoofer up and running, calibrated to the same level and equalized flat or as close to flat using the SMS-1 (using the latest software update), most of my sliders are at their lowest settings. I have boosted the 15 hz slider to maximum and the 50 hz slider by a couple dB's.

Even still, I find that if I want to feel bass, I need to watch at and around the -5 mark once calibrated to a 73 dB (needle hovering around 72-74) to match a 75 dB average reading. If this is what accuracy is supposed to be like then I really don't think I'm a fan of accurate levels.

To be fair, the levels itself are not necessarily the major reason why I'm not thrilled by the results. I think what is even more important is that my room curve (according to SMS-1) is relatively flat. I had to take a number of sliders from 20 hz up to 40 hz and turn them all the way down to get a flat curve.

Just shows how much my room was boosting output in the deep bass regions. Perhaps I need a house curve. But then is a house curve accurate ? Then we start this whole discussion over again. Many people swear that a flat response is the holy grail. Acoustician's like Ethan Winer (alright, not technically an acoustician but an acoustical expert) recommends it and a number of highly respected people within the industry.

This is interesting because I'm struggling to come to terms with all of this. In my mind I want satisfying deep bass and the most accurate reproduction. But when setting up my system this way there is no real "wow" factor unless I am approaching reference level.

I blame this more on the room curve than the subwoofer level. If I choose to not EQ my response and set the levels to the 73-74 then I get a lot of the really deep visceral bass that I am only getting at insanely high levels using my MV but then my room curve looks absolutely horrible.

Perhaps this discussion should veer more towards what an accurate room curve is supposed to be, whether flat is the ideal or if that also just subjective opinion. I'm not sure anymore.

Regards,


----------



## thxgoon

Vaughan100 - Any chance of posting an REW graph of your room? This might help with determining whether you are really getting the correct levels. IIRC the SMS1 had some issues putting out a flat response down low. I'll see if I can find the info.


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## Doctor X

thxgoon said:


> Any chance of posting an REW graph of your room? This might help with determining whether you are really getting the correct levels. IIRC the SMS1 had some issues putting out a flat response down low. I'll see if I can find the info.


The SMS-1 had a problem with the older software. The latest firmware update greatly improves the deep bass response apparently. Then again I'm not sure if the SMS-1 is all that accurate to begin with. For all I know it's probably useless with it's 1/3 octave smoothing. 

As far as I'm aware, the most accurate room optimizer at present is the 8033 anti-mode. Far more accurate than the SMS-1 with double the filters. John compared it against the BFD and the results are very close.

I haven't plotted a room curve using REW because I don't have the necessary cables yet and my sound card sucks. I'm using an integrated sound card that is very dated. One thing that I do find strange is that when looking at the SMS-1 plot, my response below 20 hz is way down. 

The MFW-15 is tuned to 19.5 hz. In room, I should be seeing response to 15 hz at least, but I'm not seeing it. Even with two of them, the response falls off like a cliff below 20 hz. 

Regards,


----------



## Doctor X

I tried to test a single MFW-15 for kicks today, I used The Incredibles chapter (I think chapter 18) where the missiles are close to destroying the jet with kids on board. The sudden impact was not causing any real air movement; I felt no bass in this scene. 

I turned my MV to -5 and could not feel any bass. This is with a subwoofer level of 73-74 dB, average 75 dB's. I then took my subwoofer level and bumped it up 5 dB's and I still couldn't feel any bass. The cone was barely moving on one of the most demanding scenes in the film and I struggled to get the cone to move much further even though it was hardly moving.

Perhaps I've done something wrong. But in the SMS-1 readings, my 20 hz-40 hz sliders are literally turned down but the response shows a relatively flat reading from 15 hz to 80 hz. I have increased my 15 hz slider to maximum. Yes, I know the negatives of boosting but in this case it shouldn't have any effect at all. 

At close to reference, the cone doesn't seem like it's doing anything. 

I thought to myself : "I can't be reaching a compression state, I mean, the cone is hardly moving and I've already cut output from 20 hz-40 hz down almost completely so I should have skyscraper levels of headroom", but I didn't get anything from the scene.

I've heard the same scene play on a puny Jamo sub250 (8" cone) that I've calibrated for clients and there is far greater felt impact.

Laws of physics are most definitely on my side. I have a 15" cone with around an 1" of linear displacement and a port cross-sectional area equivalent to a 6" vent more or less. So it puzzles me why I can't feel any bass even when I push the levels higher and higher. 

I need to do more testing and the testing part is starting to get difficult as I have a neighbor that lives right next door to me and she is an elderly women. This is a very frustrating time for me. 

Regards,


----------



## Mike P.

Sounds like fun. Personally i would check the phase on the subs and then eliminate the SMS-1 from the chain. Trouble shooting is all about the process of elimination. You're right about the laws of physics when comparing a 15 inch sub to a 8 inch sub, unless you have a severe room interaction issue.


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## Doctor X

I have checked phase. If both subwoofers are in phase the crossover region is flatter but I get some cancellation from 30-40 hz but not major. If I set the phase to 180 then there is a huge depression up to the crossover point but slightly more bass down low. 

So I left it set at 0. Keep in mind that I've disabled the second MFW-15 as I need to know what is going on output-wise. According to testing, the MFW-15 measured a couple dB's shy of an SVS PB13-Ultra down to 20 hz so I should be getting pretty good output.

The SMS-1 has sliders that can cut or boost. You can boost frequencies up to 6 dB's or cut up to 12 (I think, I'm going off memory here). I have cut 20 hz by the maximum amount, I've almost completely cut 30 hz and 40 hz sliders. All this just to get a flat response according to the SMS-1 graph. 

I need to do some more testing to confirm maximum output at low frequencies. Perhaps it's test tone time.  I'll burn tones from 15 hz to 40 hz. Since I've gotten these MFW-15's, I've yet to feel any bass from them, but keep in mind, again, that as soon as I received them, I've had both plugged into the SMS-1 where I've drastically cut the deep bass levels which might explain why there is extremely low cone excursion.

The issue is that when I increased my MV I couldn't get the cone to move any further and it wasn't moving that far to begin with.

Regards,


----------



## Mike P.

The test tones is a good idea. You should be able to verify the accuracy of the SMS-1 by measuring the output of the tones with your SPL meter, with the proper correction file applied. Any major discrepancies will tell you there's a problem somewhere.

On the issue of phase, I verified 2 subs onetime to have the same phase according to the amplifier controls. The problem ended up being one sub was wired wrong and the subs were working against each other. Since then I always verify the cones are moving in the same direction. It would have saved me a lot of grief had I done that originally. Just a heads up.


----------



## Doctor X

Mike P. said:


> You should be able to verify the accuracy of the SMS-1 by measuring the output of the tones with your SPL meter, with the proper correction file applied. Any major discrepancies will tell you there's a problem somewhere.


Yes, I am going to do this. Unfortunately I can't do this right now. Truth be told, I'm probably going to sell the SMS-1 and get the 8033 anti-mode. 



> On the issue of phase, I verified 2 subs onetime to have the same phase according to the amplifier controls. The problem ended up being one sub was wired wrong and the subs were working against each other.


Both subwoofers are positioned besides each main speaker about 4.5 meters apart. The subwoofers are positioned 3 meters away from my seat. My approach to calibrating dual subwoofers is pretty easy. Turn one subwoofer on only and set the gain levels to where you achieve a 70 dB level at the seats. Turn subwoofer off, turn second subwoofer on. Set the gain levels where you arrive at the same 70 dB output level. Turn both on and the overall level is around 73-74 dB's. 

You can then season to taste. If you don't achieve at least a 3 dB increase then mess around with the phase controls until you do.  The funny thing with the SMS-1 is that I just calibrated for a flat response yesterday but I plugged it in for measuring a few minutes ago and the graph has completely changed. 

Weird.



> Since then I always verify the cones are moving in the same direction. It would have saved me a lot of grief had I done that originally. Just a heads up.


Thanks for the heads up. 

Regards,


----------



## thxgoon

If the cone isn't moving too much on The Incredibles at those levels the SMS is doing is job in keeping the bass out of the signal. Personally, I think that sounds like your problem


----------



## Doctor X

But then if I increase my master volume it makes almost no difference whatsoever. I tried increasing the volume bit by bit until I reached reference and I still couldn't feel any bass.

Something really weird is happening. To make matters even more weird, I tried eq'ing my response an hour ago and the response curve was completely different compared to when I first started with it. Tommorrow the response curve will be completely different even in the same spot.

Weird I say. 

Regards,


----------



## thxgoon

That is weird. Does your receiver have a subwoofer limiter built in? Check to make sure that is not engaged. I'd start by taking things out of the signal chain one by one until you've found your problem, then build it back up to the way you like it.


----------



## Doctor X

Probably my biggest issue of all is that I'm not in a position to trouble shoot properly as I have a neighbor that is pretty upset with me already. ****, how do you think I found out that my MV had no effect on low frequency output ? 

Any testing at all requires high output levels as that is what I feel the underlying issue is. So I'm in a weird position. If I bypass the SMS-1 entirely then I will have + 12 dB's at 20 hz-40 hz which is obviously a major level increase. But that doesn't explain why when I increase the MV to improve the felt impact it doesn't happen. Unless the SMS-1 is doing something which it shouldn't be doing. Not sure what that is but it could be a problem.

I have dual MFW-15's which puts me in a "better-than-SVS PB13-Ultra" league in terms of output. So although I've cut the low frequencies down to achieve a flat response I still shouldn't be reaching a compression state where the output doesn't increase as my MV does. If anything, I should be getting more headroom and low distortion given the EQ cuts.

In any case, I have a Yamaha RXV-450 AV receiver. It's an old, old AV receiver partnered with a top flight Jamo Concert 800 speaker package.  What a combination I have. Not sure if there is a limiter engaged but DRC is turned off.

Regards,


----------



## tcarcio

I know this probably is something you checked but are you useing the same preset in the sms-1. When I first got mine I didn't save the preset after EQing and it automatically defaults to preset 4 and I EQed 1. When I turned the sms on again it was in the default preset and was totally different.


----------



## tonyvdb

Vaughan100 said:


> I have dual MFW-15's which puts me in a "better-than-SVS PB13-Ultra" league in terms of output.


Hmmmmm, Im not sure about that but I do agree that you do or at least should have very noticeable output thats for sure. Have you played around with your phase controls on the subs? you may be canceling each sub out if your phase is not correct.


----------



## thxgoon

2 things seem odd to me.

1 is that you have to bottom out the eq from 20-40 hz to achieve a flat response. That would require some insane room gains. Possible, but I think not probable. 2, that the bass doesn't get any more intense when you raise the volume. So either you're out of power, or something in the chain is either maxed out or limiting for some reason.


----------



## Doctor X

tonyvdb said:


> Hmmmmm, Im not sure about that but I do agree that you do or at least should have very noticeable output thats for sure.


One MFW-15 measured 3 dB's less clean output compared to the PB13-Ultra down to 20 hz according to testing done by Craigsub. It was only 1 dB short of the PB13-Ultra from 20 hz-63 hz average. This is not a weak subwoofer. Two MFW-15's should give lower distortion and higher output (up to an 6 dB maximum) especially if co-located. 



> Have you played around with your phase controls on the subs? you may be canceling each sub out if your phase is not correct.


For testing purposes, I've decided to keep one subwoofer on. It is in phase.

The problem is that I am not experiencing what this subwoofer is capable of. Yet.

Regards,


----------



## Doctor X

thxgoon said:


> 2 things seem odd to me. 1 is that you have to bottom out the eq from 20-40 hz to achieve a flat response. That would require some insane room gains. Possible, but I think not probable.


I thought the very same thing ! I did EQ my response again last night and I found that from 30 hz up to 50 that there was a major depression. So I'm wondering how reliable the SMS-1 is. I increased the sliders from -12 to -6 (30 hz) and from 40 hz (-12 to -3). This was required to flatten the response _this time_.

It _appears_ I have a lot of room gain down to 20 hz (whether the graph is reliable on this or not is another matter) and so I left the response as it was with a -12 dB cut (maximum). That might change. How common is it to have a 12 dB cut at 20 hz ? My room is 3000 cubic feet with openings to a kitchen. 



> 2, that the bass doesn't get any more intense when you raise the volume. So either you're out of power, or something in the chain is either maxed out or limiting for some reason.


Those are potential problems. I need to find out why but I'm not able to because of my "other" problems. 

Regards,


----------



## Doctor X

tcarcio said:


> I know this probably is something you checked but are you useing the same preset in the sms-1. When I first got mine I didn't save the preset after EQing and it automatically defaults to preset 4 and I EQed 1. When I turned the sms on again it was in the default preset and was totally different.


I always save my results and I do keep the SMS-1 on all the time.

Regards,


----------



## Ricci

Have you taken the SMS1 out of the chain and tried it like that? 

By all accounts the MFW15 is a good performer and should be able to rock out a movie impressively. I can tell you that I recently watched The Incredibles and there is some hefty bass in that movie. At -10 from reference a single MFW should be getting a good work-out. I doubt that a single MFW15 will even handle that movie at reference in most rooms in all seriousness. Reference is a LOT of bass.

A couple things I noticed. The SMS1 rolls off the lowend. The MFW15 starts rolling off below 18hz and probably has a highpass somwhere. On top of this you are cutting 12db at 20hz and also at 40hz? Something is not right. Do you have a suck-out around 30hz and you are trying to match the levels above and below to that? Can you post a screen shot of the SMS1 calibration? perhaps one wit your settings applied and one without?

Dumb question. Were the SW levels set before adjusting the SMS1 EQ?


----------



## Doctor X

Ricci said:


> At -10 from reference a single MFW should be getting a good work-out. I doubt that a single MFW15 will even handle that movie at reference in most rooms in all seriousness. Reference is a LOT of bass.


I have no doubt that reference is a lot of bass. But the one MFW-15 was calibrated flat with the main speakers. This is a relatively big subwoofer with a 15" long throw woofer with a port area equivalent to 6" or so. But it's not as if the subwoofer was bottoming, cone excursion was minimal and any increase in my MV did not change that.



> A couple things I noticed. The SMS1 rolls off the lowend.


The SMS-1 does not roll off the low-end provided you get the latest firmware update. 



> The MFW15 starts rolling off below 18hz and probably has a highpass somwhere. On top of this you are cutting 12db at 20hz and also at 40hz?


I had three filters cut 12 dB's each at 20 hz 30 hz, 40 hz. This was required for me to have a flat low end but that doesn't seem right either. 



> Do you have a suck-out around 30hz and you are trying to match the levels above and below to that?


No, but I did have a major null in-between 50-65 hz. 



> Can you post a screen shot of the SMS1 calibration? perhaps one wit your settings applied and one without?


Excellent idea. All talk and no screenshot.  I'll do this as soon as I can.



> Were the SW levels set before adjusting the SMS1 EQ?


No. I calibrated the subwoofer levels after I adjusted the SMS-1.

Thanks.

Regards,


----------



## Synthsayer

I did not read all of the postings here but it seems there are many theories and opinions as to what the proper sub settings should be. Here is mine:
From my experience of almost 20 years of using subwoofers for HT, I have found many things come into play; room construction i.e. walls and flooring, apartment or house, carpeting or not, symetrical room shape, and many others.
With subs it can be like chasing your tail trying to get a nice setting in some rooms. I avoid the use of the words 'right' or 'correct' on purpose. Theatre systems are set up to achieve a certain frequency response at a specific volume level which is not always possible in the home environment. First of all many people have neighbors that would prefer not to hear movies thundering through aprtment or duplex walls. I can't tell you the number of times I have had neghbors come pounding on my door or start banging on the walls or ceiling. Ughh... Thus, I have to find a good overall sound level with reasonable sub settings that allows me to enjoy a movie without disturbing my neighbors.
I have found that sub amps with built-in EQ, or crossovers with built-in EQ -the Audio Control Richter Scale that comes with calibration mic. and a bridged Hafler Dh500 is what I started with in the 80's and is still made- will help you get a nice sound from your subs. Also try to find one with phase adjustment. I am using the O-Audio 500W BASH plate amp and single 12" Infinity driver.
I can get relatively flat response down to around 28Hz. But as some previous posts stated that left the system with plenty of low end rumble but no real punch. I finally played around with EQ settings to account for room modes around 30-40HZ EQ'd down by about 6-7db. This left the rumble that seems to come out of nowhere at the right times and lots of punch and definition when the soundtrack kicks in.
Also remember that the human ear does not hear with a flat response. I also use acoustical absorption panels on front and side walls. The Fletcher-Munsen Curve or Equal-Loudness Contour that defines how humans actually hear what frequencies and how loud they are percieved. http://en.wikipedia.org/wiki/Fletcher–Munson_curves I have played drums since I was 7 years old and been in rock bands since I was 15. Cymbals at close proximity will have a profound affect on the hearing. After some shows my ears would ring for weeks. I had to give it up and now wear headphone monitors when playing but that is all another story.
My main point is that regardless of the alleged correct or right settings, or what you measure with SPL meters, in the end all that goes out the window and it will come down to tuning the sub to integrate with the room and your personal taste.


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## pnutbutter81

Like many posts have said, listen to your ears and adjust accordingly. This is geared towards any bedroom full of the usual furnishings for a college student. My experiences have led me to using this method, fine tuning by ear, using a galaxy cm-140 spl meter, rives audio test cd2, and running through this procedure anytime I've changed my furniture layout . I first begin by placing my sub as close to the exact ear listening position I will be in, because I am almost always the only person using and watching. Then I crawl around the room in the space I can place the sub, with spl meter in upright position, marking with coins where I get the "best sound" or highest spl reading using slow weighted c response. Then I set the sub, facing toward my listening position closest to that spot with the speaker cone. Next, I use a test cd (rives test cd 2) ,set to the crossover point preferred to check for phase, and run a test tone at that or around 60-80hz. While incrementally moving the phase from 0-180 degrees, i have the spl meter in my listening position, again set to slow c response, and find the setting where I get the highest spl reading and leave this. Next, Since I have a sunfire true subwoofer signature eq, I run it's automatic eq with it's supplied mic set in my listening position, and vouch it does a pretty good job, instead of running through setting a flat tone with test tones from rives test cd. Next, I proceed to turning off the sub, and running audyssey eq with all the other speakers through my onkyo 805 receiver, with supplied audyssey mic in listening position(s). After letting it calculate, I save, turn on the sub, recheck for accurate speaker distance, and use the reciever's pink noise to also reaffirm the speaker levels (with sub on) with spl meter in listening position, set to c weighted slow response, and level every speaker but the sub to around 80-85db (neighbors don't mind), and have the sub around 90-95db. I'm one step away from the end! Then a I run a familiar cd with lots of bass guitar at low levels from 40-80hz (primus, pork soda cd), and just use the sub gain knob to further integrate while going back and forth to my listening position. Again, crossover frequencies for your speakers to your sub can differ depending on yours. I use to think my main speakers could hold 50-60hz well with past test cd playing, but recently set them to 80hz cutoff and set the sub to 80hz low pass cutoff, and it made a huge difference and obviously took even more of a load off the other speakers while sending the rest to the sub, which is it's purpose after all. That is a general outline without going into too much details I could include, and should work well with the recievers of today with automatic eq setups.


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## Synthsayer

I checked out the Sunfire True Sub Web Site and it looks very impressive. I really like the idea of the various EQ settings and built in test mic. I bet it rocks.
I tried to find some pricing info but will have to contact dealers I guess. I can't afford it right now anyway.:sad:
It sounds like you have a very nice system and found a nice method for setting it up. Mine is a bit more convoluted.
I place a studio condensor mic. on a boom stand in the listening position and run it into a Tascam TM-D1000 digital mixing board on an XP Pro system running Nuendo3 recording software with Waves Diamond Edition .VST plu-ins. All mixer EQ set flat. This goes through a fibre digital converter into the EMU1212 Sound Card on the Digital Audio Workstation PC. I then connect audio output of my Acer laptop running Vista to spare inputs on my Harmon-Kardon AVR 154. I use WinISD BETA on laptop to generate a slow sweep from at 10HZ-10kHz. I know the approximate response of the studio mic (cheapy but decent MXL 990 from musician's friend) and it is fairly flat from 30Hz-20kHz according to manufacturer http://www.mxlmics.com/condenser_mic/900_Series/MXL990/mxl990.htm . I record the sweep tone onto an audio track using the recording software at increasing levels until it is just beyond what my normal listening level would be. This gives the sweep tone frequencies running through the sub and as fr. increases, out of the front center and rear satelites. I then use a frequency analyzer plug-in and play back the tone to see where the peaks and dips are and look for possible phase problems.:explode: 
Like I said, it is a really convoluted ( Rube Goldberg ) process but it seems to give a fair indication of the system response overall. I make most of my speakers except the small rear and center units. 
O-Audio sub amp is actually running a leftover Infinity 1230W Reference Series Auto Sub in 1.7 ft. cu. sealed cabinet that is weighed down with a leftover power amp that weighs about 40 pounds and on spikes. I compared the driver response plots to many other high end units costing ten times as much and even though it has an f3 of 42Hz. I get reasonable flat response measured down to 30HZ. I had the driver in a ported cabinet that was supposed to be flat to 30 Hz but liked the sound of the sealed system better. The front main speakers are HiVi Research 8" woofers and Scanspeak Revelator Series D2905 1" tweeters w response from45Hz-30kHz. Crossover in Harmon-Kardon is set to 80Hz and is 12db per ocatave and I bypass the internal one on the sub amp to avoid phase issues. I may experiment with changing this. 
The system sounds okay but I miss my old powerhouse stereo system.:sad: I used a Superphon SP100 Signature series pre-amp going into Behringer CX-2300 crossover and a Ramsa P1200 running EV DH1012 compression drivers mounted on HR9040 horns; BGW 250 driving JBL short-throw bass bins (popular concert cabs for many years); and QSC-RMX 1450 running the sub. It had a total of over 2000 watts into 8 ohms and could make your pants legs move with the air pressure. It was crystal clear at the highest levels. Those things could get loud.:jump: 
I switched to the lower power system so it would take up less space and give me 5.1 surround and remote control flexibility features. I am fairly happy with the system even though it is far from perfect.


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## bobgpsr

> Like I said, it is a really convoluted ( Rube Goldberg ) process but it seems to give a fair indication of the system response overall. I make most of my speakers except the small rear and center units.


Wow that is involved. I'm impressed.

But I personally find that REW with a calibration mike (LinearX M31) plus a RS SPL meter is fairly simple to use. I also use TrueRTA with my cal mike to look at various speaker responses in detail.


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## Synthsayer

Thanks B,
I will check those out when I have some time later today. I am sure there are much, much simpler ways to analyze the system but I am kind of stuck using what I have for the moment. When I can afford to, I will get some different test gear. I would really like to have something to more accurately measure the response of my DIY speakers that I build. I'm pretty happy with what I have right now, but I am sure I will have new ideas to modify the system in the future.
Thanks again.
Have a nice day.
Synthsayer


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## Blueeyedfrog

In answer to the original question, do we like the sound of house curve / flat responses?

My answer is no.

I have previously had a 12" sub driven by a 240watt plate amp tuned to 20hz and now have 2 x 18"ers tuned to 15hz powered by an EP2500 which gives 750 watts per channel (at 4 ohm load).

In both cases I prefer the un-EQed sound, basically for the massive room gain peaks - as soon as I flatten eveything out, I get less shaking, and so it's less exciting for me. I should note that for the 2 x 18" subs, in order to get a flat room response, I have to add a whopping -12db filter at about the 40hz mark.

Re the flat response - the way I figure it, let's assume I'm running the EP2500 at full power (750watts/channel) and that you need twice the power for every increase in 3db gain. If I have to knock 12 db gain off around 40hz to get a flat response, that would work out to about 47watts of power being supplied in the 40hz region (47 x 2 x 2 x 2 x 2 = 750) - no wonder I'm not getting much happening!

I should note that I only use my subs for home theatre and not music. I doubt that you would want massive peaks in the bass when listening to music. However, for me, subwoofers in home theatres are all about feeling the action so for my taste - more, anywhere (at any frequency), seems better.

Also, I have just started to play around with my new setup so I may change my mind in a few months but for now, that's my 2 cents worth.:daydream:


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## Doctor X

Thanks for contributing Blueeyedfrog. Don't you find that when you watch a movie that has a musical score (99.99% of the time) that it sounds bass heavy if you don't EQ ? Do you have bass traps in your room ?

Regards,


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## thewire

Watts don't mean much. I run my four subwoofers using only 180W. 180W X 4 = 720W so all of my subwoofers combined do not run on as many as one of your subs. I would almost be afraid to put that much power in my little HT. The first time I sat a sub in my bare concrete room (before it was built) and played a wal-mart 25$ subwoofer in my plywood box with one of my amps my ears were ringing for about 20 minutes. I think you would have fun with room treatments. It doesn't sound the same as equalization.


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## tonyvdb

I also dont like the sound of a "flat" system, I like to add some lows and highs to it My EQ usually has a bit more boosted in the 20-40Hz range and again in the 12-15kHz range.


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## Synthsayer

thewire said:


> I think you would have fun with room treatments. It doesn't sound the same as equalization.


Room treatment can do a lot to improve the sound of any home theatre or listening environment. It does not have to cost much either. I used 3" wedge and pyramid foam, glued it to 2'X4' sections of 1/8" Masonite board, then experimented with placement until I was satisfied with the results.
It was well worth the trouble.


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## thxgoon

tonyvdb said:


> I also dont like the sound of a "flat" system, I like to add some lows and highs to it My EQ usually has a bit more boosted in the 20-40Hz range and again in the 12-15kHz range.


Ditto.


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## Blueeyedfrog

I have only had my current setup for a couple of weeks and haven't really had a chance to fully explore its performance - so I haven't even been paying attention to movie music soundtracks. But I will now that you mention it.

I may try changing the seating position. With my 12" I remember I got huge pressure sensation if I changed the seating closer to the rear wall - again, not recommended for music listening I think, but it may be fun for movies...

No bass traps on my room but I understand they are only effective to around 80hz (from memory). I have the worst listening environment ever (maybe I should start a contest?) - concrete floors, walls, ceiling, L shape with one flimsy floor-to-ceiling IKEA shelving as part of a wall to the listening area. No door to the area so reduced possibility to pressurise the room. No carpet, just thin curtain-like material on the floor. Yes, depressing :no:

I think that because I'm in a concrete bunker, and so lack tactile vibration (compared to a wooden house), this is a factor as to why I prefer the non-flat room response...

Interesting people boost the 20-40hz zone.


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## atledreier

I'm on a concrete floor as well, and I get lots of tactile response. Don't need a moving floor for that, dude.


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## thewire

Blueeyedfrog said:


> No bass traps on my room but I understand they are only effective to around 80hz (from memory).


Not necessarily. You might treat lower and espicially if you are improving any sound leaks in your room.

Here is an animation of my latest room treatments. The calc file was not always loaded and sometimes a subwoofer was off. Sorry about that. The mic did not move during the treatments proccess. The subwoofers and mic were moved for the first, second, and last frame. Not a perfect animation but watch bellow 80Hz. This is some pink and a very small amount of Roxul being stuffed in corners above my tile ceiling. Nothing fancy or expensive.

http://farm4.static.flickr.com/3199/2738110984_151a2d281e_o.gif


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## Guest

what an awesome thread. The first post exactly describes what I am seeing now that I have spent the past month or so calibrating and charting my system. One thing I am thinking is that I need to untrain my ears from all of those years listening to rear and LFE channels which were set too loud.

The B&K test tones are done at -12.5db, so I read 83 for speakers and 80 for the sub before it really starts to rumble too much and make me uncomfortable. I would start popping drywall nails out if I went to 0db, usually listen at -30 if the wife is with me or -22 if it's just me.

jp


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## Doctor X

It has been a long while but I needed to respond and let everyone know that I sorted out my problem. Now I consider myself to be a technical person understanding how things work. I kept on reaching a compression state with my subwoofers and I had no technical reason as to the _why_.

I connected both MFW-15's up and calibrated to the 73-74 dB's, pulled out a couple of films and again, compression seemed to hit in badly as I increased my MV past -3. In other words, the bass simply stopped getting any louder. But even worse than that, I couldn't really feel any bass on most of the bassy scenes I tried.

This should be impossible. Now consider that my gain control at the back of both subwoofers are very, very low. That shouldn't make any difference because the subwoofer level and gain control together form the effective "volume". I was wrong ! It made a major, major difference increasing my gain control and dialing back my sub level.

I disconnected my one subwoofer and turned up the gain knob to 40% and then dialed back my subwoofer level and the SMS-1 volume control. No compression at very high levels and I can feel all the bass now ! 

I am pretty amazed that it has taken me so long to figure this out. I mean, increasing the gain control shouldn't be making any differences when I have calibrated using the subwoofer level. The overall level will still be the same regardless but not in my case ! I tried several scenes from Matrix Revolution and I am blown away with the tactile feeling that I now have. 

Not because I have increased my overall level over and above what I had. No, the level is still hovering around 73-74 dB's. But now I can feel this concussive force; an effect I simply did not have before this day. I'm so happy now that I am going to go through my entire collection because as far as I am concerned, this is the first time that I'm experiencing my subwoofers abilities.

So to those more technical, why is it that the gain control had such a major influence. The difference was absolutely major. How can this be ? It's like the gain control was the limiting factor in providing me the power I needed to sail through the peaks; the moments where you really need headroom.

I've spoken to Mark Seaton who, before on several occasions couldn't explain why my bass was so extremely anemic. I mean, if you EQ flat and have a subwoofer as powerful as the MFW-15 then it stands to reason that you should have far greater headroom due to my cutting of several peaks in the response curve.

I bet he didn't think about the gain messing up my dynamics. Anyways, I'm just happy this is sorted out. Still have absolutely no clue as to what happened.

Cheers !

Regards,


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## Doctor X

My opinion on "accurate subwoofer levels" have changed altogether. It appears that my initial impression had been hampered. Playing Cloverfield at -8 from reference calibrated flat (and eq'ed flat) with the mains is an awesome experience now. 

Watching all my favorites demo scenes is an experience. And this is just with one of my MFW-15's enabled ! I haven't even hooked up the second one. I really can't imagine asking for more. If I had to disable my SMS-1 and play the same scenes with the massive 6-8 dB peaks at the low frequencies I'm not sure it would necessarily be a good thing. 

All I know is that I now have massive headroom and I'm pretty sure my distortion levels are very low.

I'm happy. 

Regards,


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## Ricci

Your gain structure can indeed play a big role. You have the gain in your reciever volume, the SW level relative to that and the actual gain on the MFW. The MFW will have a point where the input is overloaded from too much voltage and also there will be a certain amount of voltage needed to get the full power from the amp, which also depends on the gain setting. If you have low voltage from the reciever and the gain on the MFW is set low this could produce the low volumes that you experienced. In my situation I have the preamp volume, plus the SW out volume, plus the EQ volume, plus the amp volume. If any of those is out of wack is can result in a clipped signal before it get to the amp, or less than maximum performance from the sw. Usually there is a very broad range where everything fits together nicely though.


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## Doctor X

Ricci said:


> If you have low voltage from the reciever and the gain on the MFW is set low this could produce the low volumes that you experienced. In my situation I have the preamp volume, plus the SW out volume, plus the EQ volume, plus the amp volume.


If I never had the SMS-1, I don't think I would have been able to dial back the sub level to the required SPL for calibration. 

My SMS-1 gain is set very low, only to 8 instead of 15 (what it was before) because I had to increase the gain on the subwoofer from less than 20% to over 40% or thereabout to make the changes. 

In some subwoofer installs, the receivers put out such a high voltage signal that turning the gain on the subwoofer as low as it can go is about the only way to get reasonable SPL calibrations. Which is why it's nice to have the SMS-1 in the chain for additional control.


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## Doctor X

Ricci said:


> If you have low voltage from the reciever and the gain on the MFW is set low this could produce the low volumes that you experienced.


That makes complete sense Ricci but the overall SPL level was still the same for calibration. But playing program material was a completely different story. Putting on FOTR is amazing. When the Balrog approaches the walls flex and the pressure sensations are out of this world.

Regards,


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## Doctor X

I couldn't believe how much my walls were shaking with FOTR "The bridge" scene even at -14 from reference. This entire time nothing was really happening and it's all because of the gain being set too low. Thing is, I would never have suspected this before as my target calibration SPL was accurate.

Would I expect to see any gains over and above 40% for gain ? I mean, before I had the gain set to below 20% to reach the same SPL level. I do have two subwoofers so that would mean that my gain levels would need to be set lower to maintain the same SPL level. Would I run into any problems again or should it be fine ?

Regards,


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## Guest

I experienced something similar when I started using the bypass input on my sub - now I control the LFE level through the preamp instead of the knobs on the back of the sub and it is much more impactful.


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## Doctor X

I think I might sell the second MFW-15 now. I mean, there simply is no need. Calibrating flat and Eq'ing flat has it's advantages, like huge headroom increases. I don't think I will run out of steam running my system this way at reference.

Regards,


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## Synthsayer

The Wire-Steven,
Did you say that your subs are stacked in an earlier posting? I would not recommend this. The reflected frequencies from the floor will be different from each driver. If space allows you may want to try placing both side by side, cabinet to cabinet and away from sidewalls.


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## Synthsayer

Blueeyedfrog,
I think a worst room contest would be humorous and helpful. I always thought I had the worst room. Now I know others feel the same. It will drive you nuts with setting up your home theater system, especially the sub. My room is similar in that it does not have doors nor parallel walls of equal length. If I stand in one part of the room, I hear one dominant frequency, standing in another part, the same thing. The speaker that worked the best is an old, old, Electr-Voice Aristocrat Corner horn that has a really flimsy baffle board and no place to mount plate sub amp.
As I have said in other threads, I use the O-Audio 500W BASH sub amp with Harman Kardon AVR 154. Sub amp has a very nice EQ and low boost, plus variable phase. This helps the user to integrate the sub very well even in the worst of rooms.
If you have the Thiele-Small info of your sub and even better, the woofers in your front and rear speakers you can use several free programs to model their approx response. One of these is Jeff Bagby's Woofer Box and Circuit Designer http://audio.claub.net/software/jbagby.html#WBC the other is WinISD Beta from LinearTeam http://www.linearteam.dk/default.aspx?pageid=isdonline Both of these will give you the phase per given frequency. I just started working with Woofer Box and Circuit designer but was able to see exactly howthe Paramtric EQ and Crossover settings affected the sub. This gave me a reasonable starting point as well as the info from WinIsd Beta that showed both the woofers in the fronts and the sub driver had a phase plot of about 43 degrees at 80Hz.
I still had too much of a room mode around 40 Hz and quickly adjusted EQ and variable Q to clear it up.
For people that say subwoofer frequencies are omni-directional, don't believe it for a minute when it comes to an irregularly shaped room.


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## thewire

Synthsayer said:


> The Wire-Steven,
> Did you say that your subs are stacked in an earlier posting? I would not recommend this. The reflected frequencies from the floor will be different from each driver. If space allows you may want to try placing both side by side, cabinet to cabinet and away from sidewalls.


That's interesting. I wonder if this is the problem I hear when stacking them. There is no absorption on my floor. What happens when I stack them in the corners together (that was just an experiment with the front) was not very clear with audible testing, but they did in fact measure very different as you point out. I found that having two stacked in my front left corner, and two stacked in the back right corner had some good LFE, but I had trouble with the high frequencies of the sub woofers. I had written it off as a problem with transients as one side of the room would seem to have a different speed and distance to the higher sounds. It very well could be related to the floor. For some reason I had smoother response at the seats on the other side of the room closest to the subs when they were stacked. My four sub woofers are currently sitting on my stage in a horizontal position/ horizontal array. I'm not sure what effect having them raised would have on the response as it only seemed to effect the 50Hz - 180Hz area, with some variance in the ringing down low. I think I have enough absorption in my stage but I have thought about adding some heavy material over it. I will have to test that sometime but with REW but listening test are good. The ports are only inches away from my front wall, but I have had zero problems. I still have more room treatments in the plans, and in fact I had the same problem with the door slamming around since adding some newer treatments, similar to when I had them stacked, only it was a sound that subsonic doing it I discovered. I had to rig up an extra set of weatherstripping on the door. There are two strips that if I use the door needs to be pulled very hard before turning the door knob, so those two are reserved for the movies with lots of bass.


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## Thunderheader

Hello,

I'll just give my .02 as to what I have my subs set to. I originally had a PB12-NSD which was great, the I bought a 13Ultra....massive improvement! I then bought a second 13Ultra. With the NSD and single Ultra I found that the sub calibrated to 72-73db on the RS meter was not nearly enough for my tastes and what I think the movie should sound like. A movie for example like Transformers with an Ultra, in a 110sq ft room should pound but it does not. when calibrated to 72-73db but sounds much more alive when calibrated to approximately 8db higher. Now with my dual Ultras (collectively set to 83-84db taking into consideration the lower reading on the RS meter) it sounds quite good. 

So TonyVb I agree with you, the LFE set higher than the mains sounds substantially better.


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## Blueeyedfrog

Thanks for the tips Synthsayer (only took me three months to get around to reading them). I think worse room response competition is a great idea. How about a prize for the best corrected/eq'ed room?

Anyway, I've since shifted houses and guess what? I'm now in another bl**dy L-shaped room (replete with hole in the wall to outer corridor). I'm cursed :explode:


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## Ian M

Hello people. I still need a few more posts to hit 5 so another 2 cents worth here:

I find that a flat frequency response is very much a desirable thing for listening to good music recordings. IMO a pair of big stereo speakers is much better than a pair of satellites and a monaural sub due to loss of LF stereo positioning. A good demonstration of left and right bass is on the Telarc Tchaikovsky Nutcracker Soundtrack CD (Mackerras LSO) which has contrived cannon shots left then right which sound like they are spread somewhat around the 40 Hz mark. The directional effect would be lost with a single mono sub.

For movies mono subs are fine, but I see the discussion of flat reponse a bit silly since all of the LF detail on the recording is contrived anyway. I see no need to strive for super flat subwoofer response as it will in most cases be ruined by room effects which are in some cases impossible to correct even with a multi-band subwoofer equaliser. I have toyed with the idea of building a dual driver (push-pull) bandpass sub having a slight RISE in output with diminishing frequencies in the pass band. So long as it crossed over reasonably well to the other speakers (say around 80 Hz or so), a gradual rise down to say 25 or so Hz could be very desirable. I have modelled a pair of 18 inch JBL drivers with WinISD and it looked very interesting indeed as a HT sub. Group delay considerations (almost as bad as ported) and a rollercoaster cone excurson curve had me do something else with the drivers, but food for thought.


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## atledreier

If you build a subwoofer with very little distortion (harmonics), and lopass it at 80Hz with mains taking over, and do a good transition, I'd say you have ears like an wolf if you can localize the subwoofer. It's not the <80 you localize it's the higher frequency distortion.


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## Ian M

Pure 80 Hz has a wavelength of about 4.3 metres and is localised if your stereo speakers are more than that far apart. At 4.3 metres or less the speakers mutually couple for a 6dB gain (assuming same input power, same signal to each) and localisation is lost. Without coupling (ie higher physical spacing) the gain is only 3dB as expected by the doubling of input power. I agree that the harmonics would be more localised as the wavelengths are smaller by the multiple, but I have not heard these from my system with pure sine sweeps from a function generator. The coupling effect is interesting and can be demonstrated when testing for in-room frequency response. You can see a different picture below and above the spacing threshhold (say your speakers are 3 metres apart - thats about 115 Hz) when one channel is removed. With two channels driven you see 6dB more SPL below 115 Hz, but only 3 dB more SPL above 115 Hz. Drive one channel only and you should see no change across 115 Hz.

The coupling effect is not demonstrated in cases like the Telarc recording mentioned above as the cannon shots are reproduced by different speakers at different times and so they actually sound quite weak (which seems apt since they are mouse-sized cannons after all... ha ha... that's a joke). Just for fun I tried it on my bi-amped system with the mids and tweeters switched off. The bass crosses over at 150 Hz 24dB/octave (Linkwitz Riley active) and the very deep sounds (predominantly I guesstimate around 40 Hz or maybe even lower) were easily identified as emanating from the left then right speakers.


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## Ricci

If you are using a 150hz xover you will have plenty of localizable content still coming from the speakers because the x over is not a brick wall, 150hz is localizable, and the fundamental bass content is not going to be a pure sine wave. It will be a complex signal comprised of many freq's including much higher freq's.


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## Ian M

I use a 24dB/octave Linkwitz Riley active crossover circuit which is of course not a "brick wall" filter but is steep and already -6dB at the crossover frequency. The closest thing I have to a brick wall filter is a 36dB/octave turntable rumble filter with fc = 17 Hz designed to limit the 0.5 Hz cone movement caused by warped 33 LPs. No I do NOT listen to LPs! I built the rumble filter into a Crest power amp to control excessive LF excursion in a couple of junk subs that I built with Peerless XLS 12 inch drivers. Very poor subs. High excursion means nothing in small drivers (imagine a 2 inch piston moving 10 inches and you may see where I am coming from) but I digress.

Bass frequencies even of random pink noise have a smooth shape similar to a sine wave but of a rollercoaster-like appearance and this can be seen on a scope if you have a suitabe source. I uploaded something to YouTube last year which kind of shows it. Its an early test-run of a pseudo-random rumble noise card that I scratch-built from the circuit diagram provided in the long-expired Universal Sensurround patent: 



 Ignore the bottom digital trace as irrelevant to this discussion.

Power amp output to load resistors shows no upper harmonics in the output on a scope – just the fundamental. Harmonics are caused by non-linear components on top of the linear component (input component) caused by the speaker transducers themselves which is audible from poorly implemented and/or cheap bass drivers. Push-pull bass drivers such as those I am using (old Jamo Concert VII) provide even order harmonic cancellation as the non-linear components (self-induced components) in each driver mutually cancel. That leaves odd order harmonics - the first of which (for a 40 Hz fundamental) is the third harmonic at 120 Hz which is well above the subwoofer range and very much identifiable as such. I hear fundamental frequencies (around 40 Hz on that Telarc CD) with left and right localisation and can't hear a third harmonic. Any second harmonic has cancelled.

Quoting from rcw in the ESP forum:

“Even order distortion is caused by the cone moving asymmetrically from its center position and in cheap subwoofers the drivers are often given asymmetric coil overhang designed to radiate the lower bass frequencies as the second harmonic, thus giving the illusion of real bass output. Another cause of second harmonic is when the cone is offset due to the d.c. offset effect. Overall the even order harmonics are main ones heard in subwoofers as the third harmonic of 20Hz. is 60Hz. nearly out of subwoofer range, although cheap drivers with no shorting rings produce a lot of third harmonic due to flux modulation, and this also tends to thicken the bass.”

Hey I don't want to be controversial as a newbie here with no established basis of credability, but it seems to me that there is much confusion and discussion by people listinging to harmonic facsimilies of the source material bass content without realising it. There is talk about software EQ attempts and calibration with inexpensive subwoofer equalisers which overlooks the matter of speaker-induced harmonics which are read by SPL meters without being identified as such. A good SPL meter will be sensitive to 10 Hz but cost hundreds or even thousands of dollars. My own one is allegedly sensitive to 20 Hz and cost a bit more than the standard cheap ones but most - like the ones available in retail outlets - are supposedly sensitive down to only 31 Hz, so if you think you are measuring say 20 Hz (or even 30 and maybe even 40 Hz) with a cheap meter and even compensating for its roll-off in sensitivity, chances are that you are in fact also reading the 40 and 60 Hz second and third harmonics. To then go away and have a computer tell you to twiddle at 20 Hz is misguided.

And apart from that, even using the C scale (industrial noise level scale said to be most suitable for low frequencies) on a properly calibrated SPL meter will not necessarily match your own hearing response or tastes.

I just use a 1/3rd octave 8 band constant Q subwoofer equaliser and manually tune the bands by ear from the seating position with a function generator connected to the equaliser input - a 5 minute set and forget job. Much better than a CD of discrete tones which often have frequencies spaced either side of a specific-frequency room mode (null) where you sit, or quick sweeps off a CD in a predefined direction giving you little chance to react and make adjustments. A function generator is good as you can turn the frequencies up and down at will by twisting a knob back and forth as you adjust each frequency band of the equaliser directly. This leaves computers and spreadsheets etc. out of the equation. I find SPL meters useful for one thing only in HT and that is putting a "number" on a max SPL test which is hardly "useful" really.

Addendum: I realise that there are sponsorship issues here and if I have gone too far, please ask me to moderate rather than booting me as I think I can help people a lot here and have plenty more to offer. I am 46 years old and have been doing the HiFi DIY thing for about 30 years.


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## bone215

I have found in my room and my system that first I set my sub to 75db based on a 60 hz tone and match it to a 75 db 1000 hz tone. I then plot out the response using a cd with warble tones. I then use the parametric eq to get rid of the biggest peak. Then I run Pioneer mcaac. I have three settings for the three main seats. Once I get it all set up, I will tweak the sub level up just a tiny bit based on listening to three good songs and some scenes with lots of base in movies. Works for me.:whistling:


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## Fabricator

Ricci said:


> Your gain structure can indeed play a big role. You have the gain in your reciever volume, the SW level relative to that and the actual gain on the MFW. The MFW will have a point where the input is overloaded from too much voltage and also there will be a certain amount of voltage needed to get the full power from the amp, which also depends on the gain setting. If you have low voltage from the reciever and the gain on the MFW is set low this could produce the low volumes that you experienced. In my situation I have the preamp volume, plus the SW out volume, plus the EQ volume, plus the amp volume. If any of those is out of wack is can result in a clipped signal before it get to the amp, or less than maximum performance from the sw. Usually there is a very broad range where everything fits together nicely though.


i am having this exact problem right now.


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## GregBe

bone215 said:


> I have found in my room and my system that first I set my sub to 75db based on a 60 hz tone and match it to a 75 db 1000 hz tone. I then plot out the response using a cd with warble tones. I then use the parametric eq to get rid of the biggest peak. Then I run Pioneer mcaac. I have three settings for the three main seats. Once I get it all set up, I will tweak the sub level up just a tiny bit based on listening to three good songs and some scenes with lots of base in movies. Works for me.:whistling:


Unless of course you have a big peak or null at either 60hz or 1000hz, but it looks like you plot out a response and it works for you. I am intrigued though and might try that.


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## Home Theater Guy

Vaughan100 said:


> Because any C-weighting SPL meter reads low at low frequencies. I use the Radio Shack SPL meter. Thus a 72-73 dB reading would equate to a 75 dB reading at the listening position.


Receivers are DESIGNED to be measured with a C-weighted SPL meter, slow response. That's 75 db, each channel including the sub, C-weighted. Keep it simple. You may be over-thinking this one.

As for the Radio Shack SPL meter, it is accurate enough in the range that we use to set levels. When I compare the levels on the Radio Shack meter to my Gold-Line DSP30 (Slow, C-weighted), the levels are the same.

I hope this helps.


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## GregBe

Home Theater Guy said:


> Receivers are DESIGNED to be measured with a C-weighted SPL meter, slow response. That's 75 db, each channel including the sub, C-weighted. Keep it simple. You may be over-thinking this one.
> 
> As for the Radio Shack SPL meter, it is accurate enough in the range that we use to set levels. When I compare the levels on the Radio Shack meter to my Gold-Line DSP30 (Slow, C-weighted), the levels are the same.
> 
> I hope this helps.


I am not sure I agree with you on this one. Gary Kuo, one of the Avia designers, said to get a truly accurate subwoofer reading, the meter should read 2-3 dB below what you are getting from your speakers because of the innacuracies. Ed Mullen from SVS recently emailed me the same thing about sub measurment using receivers test tones.


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## Home Theater Guy

tonyvdb said:


> Pink noise is 20-20,000Hz and is the industry standard for testing levels in all speakers ranges including subs. Your crossover will determine what the cut off is for the pink noise frequencies that are sent to your speakers or subwoofer.


The pink noise used for setting main channel levels on a receiver is narrowband centered in the 500-2kHz region to improve measurement accuracy. It does not cover the full frequency range. This is because the 500-2kHz region is not as susceptible to influences of the room as full-spectrum pink noise would be. Wideband 20-20kHz pink noise is used for equalizing, not setting levels in consumer equipment.

Because of the low frequency nature of subwoofers, 40-80Hz narrowband pink noise is used to set the subwoofer level. This frequency range is much more sensitive to room influences, so you need to take several measurements over the seats and check the results with at least a 1/12th octave RTA (using wideband pink noise through the center channel) if one is available. If an RTA is not available, try to get an average over all the seats and select a level that sounds like the best balance.


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## Home Theater Guy

GregBe said:


> I am not sure I agree with you on this one. Gary Kuo, one of the Avia designers, said to get a truly accurate subwoofer reading, the meter should read 2-3 dB below what you are getting from your speakers because of the innacuracies. Ed Mullen from SVS recently emailed me the same thing about sub measurment using receivers test tones.


Did they mean inaccuracies in the Radio Shack meter, SPL meters in general, or the Avia test disc?

THX recommends 75dB, C-weighted, slow response, in all channels including the subwoofer. The narrowband pink noise on receivers (at least on THX receivers) takes into account the response of a C-weighted SPL meter. Check the PMI/Gold-Line 5.1 audio toolkit DVD, they also recommend 75dB.

Now, you still need to actually listen to the system and measure the frequency response to make sure that 75dB is the right setting. Experiment with subwoofer(s) and seating placement, then set the level that gives the best balance among all the seats. If you equalize the system, be sure to set the levels again afterwards.


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## GregBe

They were referring to the innacuracies of the SPL meter, not the disc/receiver tones. In the end, matching the sub to the speakers exactly is what most people prefer, because at less than reference levels, the sub 2 dB too hot might be preferred. I don't know for sure, but I think most people just recommend matching up the speakers to the sub, because it is more simple for most people to understand.


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## Home Theater Guy

GregBe said:


> They were referring to the innacuracies of the SPL meter, not the disc/receiver tones. In the end, matching the sub to the speakers exactly is what most people prefer, because at less than reference levels, the sub 2 dB too hot might be preferred. I don't know for sure, but I think most people just recommend matching up the speakers to the sub, because it is more simple for most people to understand.


Although I have not personally used the Avia test disc, I just checked the manual for the Avia Pro Audio test disc online. It looks like there are four separate subwoofer test tones on the disc, depending on which crossover point you want to use. They recommend using an unweighted (i.e. "flat") sound level meter on the lowest crossover point subwoofer test signal (called the "Low subwoofer-balance signal" in the manual); not because of inaccuracies in SPL meters, but because the test signal was designed for an unweighted SPL meter. The manual states that the C-weighting mode, which is suitable for all the other signals on the disc, will read incorrectly on this particular test signal. Perhaps Gary Kuo did cite SPL meter inaccuracies as the reason for using a different level setting; I'm am only referring to what was written in the disc manual. That being said, if the instructions on the disc specify to use a reading other than 75dBC, follow them. The test signals I personally use are intended to be set to 75dBC.

As for matching the speakers to the sub, I'm not quite sure what you mean. The main purpose of using the test signals is to match the levels not only between the individual main channels, but between the mains and the sub as well. It is very difficult to match the mains to the sub by ear, given the different test signals for each and the wildly varying bass content on CDs and DVDs. Using an SPL meter with the proper test signals gets you there much faster, and much more easily.

The secondary purpose (but for me just as important) of using the test signals is to properly set the reference level of the soundtrack, or at least to know where that reference level is. In a properly calibrated home theater, I can set the volume to say, -10dB and I know what kind of loudness to expect from that setting. You can only get there by using an SPL meter to set your levels.


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## GregBe

Home Theater Guy said:


> As for matching the speakers to the sub, I'm not quite sure what you mean. The main purpose of using the test signals is to match the levels not only between the individual main channels, but between the mains and the sub as well. It is very difficult to match the mains to the sub by ear, given the different test signals for each and the wildly varying bass content on CDs and DVDs. Using an SPL meter with the proper test signals gets you there much faster, and much more easily.
> 
> The secondary purpose (but for me just as important) of using the test signals is to properly set the reference level of the soundtrack, or at least to know where that reference level is. In a properly calibrated home theater, I can set the volume to say, -10dB and I know what kind of loudness to expect from that setting. You can only get there by using an SPL meter to set your levels.


Sorry if I was confusing earlier. I agree with all of this, and am doing just that. Maybe things have changed, but I just know what I have read many times over many years. You may very well be right, but just recently, I got a response from Ed Mullen of SVS with some help with setting up my sub. I won't bore you with the whole email, but here is the relevant part

"Calibrate the subwoofer flat/even with the speakers. If your speakers are calibrated to 75 dB, then calibrate the subwoofer to 73 dB (C/Slow on the meter). This is because the meter reads about 2 dB low on the subwoofer test tone."

Ed knows more about subwoofers and callibrating them than I will ever hope know, so I think I will take his advice.

Greg


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## SteveCallas

Wish I would have caught this one sooner. 

The reason why calibrating flat seems fine at near reference and not so impressive at lower levels is because our sensitivity to subwoofer frequencies begins to flatten out around and above 100db. While the intended playback may have assumed a flat calibration, it also assumed that you would ALWAYS listen at reference levels. If you aren't always listening at reference levels, then calibrating flat goes out the door, as your sensitivity to subwoofer frequencies has now decreased.

Does this mean you need to change the subwoofer level for every movie you watch? Of course not. If you are anything like me, you know what sweet spot you tend to listen to movies at, and for me it's -15 to -10. Go ahead and calibrate your subwoofer flat with test tones (I'm with Home Theater Guy on this one, I don't aim for 72-73db on my meter, I get 75db), then start watching a movie in your sweet spot master volume range. Adjust the subwoofer level to preference - the boost will likely coincide with how far below reference level you are listening. In my system I run the subwoofers 3.5db hot.

Make sense?

As for test tones from a processor, they should always be wide bandwidth pink noise - I have to imagine the pink noise sent to the sub is the same as the pink noise sent to the speakers. This can be easily tested, just run a main channel pre out to the subwoofer amplifier and try a test tone. Vice versa, run the subwoofer pre out to a main channel input. Should sound the same as it did before in both cases.


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## Home Theater Guy

SteveCallas said:


> The reason why calibrating flat seems fine at near reference and not so impressive at lower levels is because our sensitivity to subwoofer frequencies begins to flatten out around and above 100db. While the intended playback may have assumed a flat calibration, it also assumed that you would ALWAYS listen at reference levels. If you aren't always listening at reference levels, then calibrating flat goes out the door, as your sensitivity to subwoofer frequencies has now decreased.
> 
> Does this mean you need to change the subwoofer level for every movie you watch? Of course not. If you are anything like me, you know what sweet spot you tend to listen to movies at, and for me it's -15 to -10. Go ahead and calibrate your subwoofer flat with test tones (I'm with Home Theater Guy on this one, I don't aim for 72-73db on my meter, I get 75db), then start watching a movie in your sweet spot master volume range. Adjust the subwoofer level to preference - the boost will likely coincide with how far below reference level you are listening. In my system I run the subwoofers 3.5db hot.


I absolutely agree with you on this point. But it should be noted that the tendency with adjusting the subwoofer to preference is that most folks, who may not be used to the way good bass is supposed to sound, adjust the subwoofer to a level that's way too loud. I would recommend first calibrating the sub to the 75dBC reference, living with it for a few weeks, and then decide if the level should be increased. Doing this will allow your ears time to "recalibrate" themselves.

Many receivers now incorporate some form of volume-dependent equalization, such as the THX Loudness Plus technology and Audyssey Dynamic EQ. I don't have much listening time with the Audyssey version, but the THX Loudness Plus does a very good job of maintaining the spectral balance and surround ambience at volumes less than reference. If your receiver has either one of these modes, they can make things a lot simpler and more enjoyable.



SteveCallas said:


> As for test tones from a processor, they should always be wide bandwidth pink noise - I have to imagine the pink noise sent to the sub is the same as the pink noise sent to the speakers. This can be easily tested, just run a main channel pre out to the subwoofer amplifier and try a test tone. Vice versa, run the subwoofer pre out to a main channel input. Should sound the same as it did before in both cases.


I just now hooked up an Onkyo TSXR706 receiver directly to a Gold-Line DSP30 real-time analyzer, first to a main channel pre-out, then to the subwoofer pre-out, and cycled through the test tones. The test tones are narrowband pink noise, frequency specific to the channel you are measuring, the same frequencies outlined in my earlier post. The main channels and subwoofer do not use the same test tones.


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## SteveCallas

Thanks for testing.


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