# SMS-1 Question



## Doctor X

I have a question regarding the SMS-1 that I was hoping someone could help me answer.

I have two presets, one is my own equalized setting and the other is the unaltered, raw response. I would like to calibrate both presets to the same level ie I want 73-74 dB when using pink noise to set my subwoofer flat with my mains on both presets.

How would I do this ? Because as soon as I eq my response I find that I must reduce the output by a couple dB's which inadvertently affects my raw unaltered response because then I need to increase the level to match the 73-74 dB level.

I just would like to compare apples to apples in terms of output level for both presets. Help would be appreciated.

Thanks.


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## brucek

> I have two presets, one is my own equalized setting and the other is the unaltered, raw response. I would like to calibrate both presets to the same level ie I want 73-74 dB when using pink noise to set my subwoofer flat with my mains on both presets.
> .


I don't quite understand how you can have a preset that is the raw response unaltered, but I know little to nothing about the SMS, so I probably just don't understand something it does.

Anyway, your idea is not too practical. Subwoofer pink noise is usually band limited from 30Hz to 80Hz. If the raw measure had a high peak in that area, the energy provided by the peak would result in a lower calibration than is reasonable. This is the reason for equalization, so you can have smooth response across the subwoofer band.

brucek


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## Doctor X

There are six presets with my SMS-1. Preset 6 is the default "raw" response. So I can go back and forth between the normal uneq'ed response and the altered eq'ed response "preset 5".

I just want to be able to calibrate both presets so that I can switch between the two and maintain an accurate comparison (in terms of level).

--Regards,


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## Doctor X

*But you won't get an accurate comparison in terms of level regardless, except at the one point at which you match them. That's the whole point of EQ, after all.*

That's the thing. In order for there to be fair comparison, I need to level calibrate both presets to the same level.

Here are some new graphs I worked on today. Before I post the graphs, just a bit of information. I had to position my subwoofer about half a meter out from the corner. Setting on AVR is small, 80 hz crossover. Crossover disabled on the SMS-1.

Software version 2.1. 15 hz subsonic limiter and a 6 dB slope used. Unfortunately I don't have the luxury to place the subwoofer where I would like but I have to work with what I've got I guess.

This is my unequalized graph (I have maintained the same settings as before in the menu :










This is my equalized graph :










This graph is equalized except I closed the door directly behind me :










Then, what I did was I took my unequalized graph and calibrated so that my subwoofer was producing 73 to 74 dB's using pink noise on AVR. This gave me a level setting on the Velodyne as 37.

Due to input distortion that might be a problem with the SMS-1 (according to Home Theater Shack) I took my sub level and increased it to -10 (it's lowest setting).

This is the uneq'ed graph but calibrated flat in term of level :










I think I may have increased the graph levels slightly (about 81-82 dB's more or less)

And finally, my eq'ed graph (preset 5) calibrated using pink noise on AVR. In order for me to reach 73-74 dB's, the SMS-1 volume level of 15 was perfect.










Listening to music, I find that bass sounds a fuller than before and sounds great on some music but boomy on others (more so than it was before). It sounds full but then on some music it almost sounds overly boomy.

Movies suffer from the same problem as before. In the dojo sequence in the Matrix, Neo falls down hard on the mat. This has 20 hz material in it.

Unequalized, I can clearly perceive a greater depth to the low frequencies. Neo falls down hard several times within the sequence and there is deep bass there. In this mode, the hits had power and depth.

The equalized results were again, really disappointing. It's almost as if the results from the graphs do not reflect what I'm hearing/feeling. I increased bass across the range of frequencies. I should be getting increased perceived level of bass but it's the complete opposite. I get audibly less impact, or extension on the same scenes.

Why on earth would this be ?

I'm really not sure why this is but I might not be doing something right (which is definitely a possibility). I suspect that the subsonic limiter is kicking in more than it should on the SMS-1.

Thoughts, suggestions would be most welcome.

--Regards,


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## brucek

> Why on earth would this be ?


Usually when someone prefers their unequalized response it's a result of the peaks that are present before EQ that gives the impression of impact at those 'single notes'. If after listening to the unequalized response for a while, then dial down the EQ until you like the sound.

If you're concerned about the SMS not representing a true response in its graphs, then measure the system with REW.



> Due to input distortion that might be a problem with the SMS-1 (according to Home Theater Shack) I took my sub level and increased it to -10 (it's lowest setting).


Yeah, I might not get too aggressive with that. You're trading overall dynamic range and S/N ratio for possible momentary frequency dependant distortion at very high levels...... :huh:

brucek


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## Doctor X

*Usually when someone prefers their unequalized response it's a result of the peaks that are present before EQ that gives the impression of impact at those 'single notes'.*

That's the thing, Brucek. I had quite a few dips and nulls before I eq'ed. I basically raised the levels a lot inbetween 50-80 hz to solve that issue. I also raised output at 25-40 hz or so a little bit too so the end result is that I should be getting more deep bass output and not less.

But I seem to be getting less perceived deep bass. I popped in Revenge of the Sith, Chapter 3, and when that star destroyer flies past the screen, with uneq'ed response, the flyby was powerful and deep. With eq'ed response, that deep powerful flyby was just meh. 

I don't understand why this is. The only thing I can think of is the subsonic filter being overly aggressive on the SMS-1. I don't know.

--Regards,

If after listening to the unequalized response for a while, then dial down the EQ until you like the sound.

*Yeah, I might not get too aggressive with that. You're trading overall dynamic range and S/N ratio for possible momentary frequency dependant distortion at very high levels......*

What would you advise me to do ?


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## brucek

> What would you advise me to do ?


You've lowered the sub output trim on your receiver to its lowest setting. You're hoping to compensate for that by turning up your subwoofer amplifier. That's fine for the louder levels, but what about the softest levels that are now lost in the noise when they come from the receiver and so the SMS ADC doesn't have any signal to work with. That definition is lost.

If we assume Ilkka's graph of the SMS is valid for all SMS's - and I can't imagine it is - It would appear that at moderate input levels the SMS is great. So, if you have a 'normal' level feeding the SMS, then normal levels down to the softest levels pass through and are digitized properly and all is well. Only at the highest input levels would there appear to be any distortion. The highest test levels Ilkka used in that test was 1.5 voltRMS. Believe me, most consumer receivers are lucky to output anything above 1 voltRMS at full volume. Do you operate your system at full volume?

brucek


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## Doctor X

So are you saying that I should decrease my sub gain volume and increase the sub level in my AVR to get the flat 73-74 dB's ? Or to decrease the SMS-1 volume and increase the level in my AVR to reach the same level ?

In order for me to reach the 81-82 dB level on the graph I simply increased my master volume to -9 (from -80 to +10). I obviously used the same -9 MV on both presets. Based on this, with MV at -9, with preset 5 which is my custom EQ, I increased the levels of the large dips and had to increase slightly, the levels at 20 hz straight through to around 50 hz.

As you can see from the graphs, the levels inbetween 50 to 80 hz have been increased considerably. That at least _should_ be giving me far greater bass punch.

Would increasing my sub level (in AVR) to get the same level 73-74 dB make that much of a difference and if I were to re-eq, should I first increase the sub level in AVR and perhaps lower the SMS-1 main volume or just decrease the gain on the sub (which is approaching about 30% or so).

Thanks !

--Regards,


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## brucek

You're making this far more complicated than it is. 

Bypass the SMS, zero all your receiver trims, run your receiver test tones and _balance_ all your speaker and sub levels with the trims.

Turn on the SMS and equalize the sub.

Once equalized adjust the sub amp to rebalance the sub to the other speaker levels.

brucek


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## Doctor X

*Bypass the SMS, zero all your receiver trims, run your receiver test tones and balance all your speaker and sub levels with the trims.*

Alright. I understand that. 

*Turn on the SMS and equalize the sub.*

But as soon as I turn on the SMS-1, it too has it's own volume control. If I use volume 15 which is what I am currently using, then I have to calibrate using all three variables. I need to do a balancing act between the sub level in the AVR, the SMS-1 volume control and the gain control on the sub.

This can be confusing.

*Once equalized adjust the sub amp to rebalance the sub to the other speaker levels.*

But then how do I compare results using two different presets ? In order for me to do this, I have to increase the volume on the SMS-1 a lot (for unaltered response) to match the mains (using the same sub level in the AVR) compared to the EQ'ed result in which case I must lower the SMS-1 a lot and maintain the same sub level in the AVR.

I can save results for both presets so that they have achieve the 73-74 dB output using the pink noise in my AVR. That is the goal. To get an apples to apples comparison, otherwise how would I compare results ?

It seems complicated but I'm not sure that it's not supposed to be complicated. 

Thanks.

--Regards,


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## brucek

> If I use volume 15 which is what I am currently using, then I have to calibrate using all three variables


Don't use volume 15 (whatever that is). Use a level that is basically *unity gain* and equalize. Then touch up with the sub amp volume.



> But then how do I compare results using two different presets ?


Bypass the SMS if you want to hear it unequalized - it must have a bypass button. If you used a unity gain on the equalized preset then the overall volume will be about the same between the two.

brucek


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## Doctor X

What does unity gain mean ? 

--Regards,


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## Doctor X

*If you used a unity gain on the equalized preset then the overall volume will be about the same between the two.*

I'm not sure I understand. I can bypass the SMS-1 completely by using preset 6 but then the overall levels using pink noise are far lower than normal (using identical SMS-1 volume levels). To calibrate both presets to equal levels require different SMS-1 volume levels.

Remember that I have to juggle between all three variables to arrive at the level of 73-74 dB's. 

--Regards,


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## brucek

> What does unity gain mean ?


It means 1:1 ratio between input and output. If I feed a volt in, I get a volt out.

You set all the frequency controls to zero and the preset gains and the master gain to some neutral position to cause the unequalized preset to simply pass the signal through unaffected. That's what I call bypassing the SMS.

Then follow the standard routine I outlines above and zero all your receiver trims, run your receiver test tones and balance all your speaker and sub levels with the trims.

Now all the speakers and sub are at the exact same level and the sub is unequalized with signal passing through the SMS.

Now equalize the sub using one of the other presets. The overall level will end up around the same level as the unequalized level. IF not tweak that presets individual volume control

You're done.


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## Doctor X

I think I understand. I'll try that out.

Is there a reason why my SPL meter is still moving back and forth using pink noise ? It shouldn't be doing that because my FR is about as flat as it's going to get, right ?

I mean, can my frequency response get any better ? If so, please advise me (based on the graphs) on what I should do to improve.

Thanks for your advice Brucek ! Much appreciated.

--Regards,


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## brucek

> Is there a reason why my SPL meter is still moving back and forth using pink noise ? It shouldn't be doing that because my FR is about as flat as it's going to get, right ?


An SPL will always move around quite a bit when reading pink noise - perfectly normal.

Your response chart is quite flat - couldn't get much better.......

brucek


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## Wayne A. Pflughaupt

> I get audibly less impact, or extension on the same scenes.
> 
> Why on earth would this be ?


Possible because the bumps you had before at ~ 40 Hz and 25 Hz are no longer there:

















And possibly because you’ve equalized for flat response with no room curve (although the complaint there is usually “thin” sounding bass, not what you’re describing).



> Is there a reason why my SPL meter is still moving back and forth using pink noise ? It shouldn't be doing that because my FR is about as flat as it's going to get, right ?


SPL meters always move with pink noise.

Do we really know anything about this processor? The specs at Velodyne’s site are pretty worthless. Are the AD/DA converters any good? :huh:

Regards,
Wayne


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## Doctor X

Wayne, what I don't understand is that I increased the levels across the board. In graph 2, you clearly see that the response from 25 hz and up has been increased to produce a more uniform, flat response.

I mean, from 25 hz and up the levels are 73-74 dB's on the graph. I've increased the levels to match the speaker levels on the graph which is about 80 dB's or so. So I should be getting much improved low end output compared to before.

I don't see any peaks in that response curve and I never brought anything in the deep bass range down. I increased. Apparently the SMS-1 is extremely accurate in it's measuring otherwise I wouldn't have bought one. 

--Regards,


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## Wayne A. Pflughaupt

I guess I need to enroll in a “how to get your point across” class. 

The broad bump you had at 40 Hz would have lent itself to perceived impact, as would the 80 Hz region an octave above it (that’s the sweet frequency for that kick drum “chest thump” you get at concerts, I’m told by professional sound mixers). Flatten them out = less perceived impact. Which is actually more accurate, because you were hearing an exaggerated effect before.

Same with the 25 Hz. Removing that bump there, perceived extension goes with it.



> I don't see any peaks in that response curve and I never brought anything in the deep bass range down.


But raising everything above it (between 25-40 Hz) has the same effect. I.e., if you boost the area between 25-40 Hz, to flatten response, or cut _at_ 25 and 40 Hz, to flatten response, you end up with the same thing either way – flattened response!

The problem probably is, you’re just not used to hearing accurate response. It can take some getting used to.

Again, I suggest moving from flat response to a house curve – let’s see how you’d like that, while you still have some hair left. :laugh: A lot of people think it sounds more accurate, even if it doesn't "look" accurate.

Regards,
Wayne


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## JohnM

It would also be better to cut the peaks then raise the overall level rather than boost the response either side of the peaks. You are applying a lot of boost which causes extended decay times at the frequencies you boost, making the sound more boomy.


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## Doctor X

Alright things are much better today. I did what a member suggested and I reversed polarity on the SMS-1. Huge difference. That huge suck out before from 80 to 120 hz has been almost transformed.

I haven't used too much boost this time around. What I did was, I increased my sub level from -10 to -7 and I raised my gain control on my sub. When I did the graph I made sure that my speaker level hit 80 and I matched this for the subwoofer.

I noticed that, yes, the 20-25 hz content is around 3-4 dB's higher than it is unequalized. After this, I popped in some music. Now MUCH better. Everything sounds more balanced and fuller. 

The funny thing is that now, my EQ'ed results are not that different from my unEq'ed results (there is a difference, don't get me wrong, but it's not as substantial as I made to make in previous attempts). The main culprit was flipping polarity from + to -.

Watching films, the deep bass is still there but just not quite as strong as after equalization which I understand.

I will post updated graphs today to confirm.

John, if I'm shooting for an 80 dB graph level so that everything inbetween 20 to my crossover frequency is flattish to 80 dB then all I need to do is to cut or boost to achieve that result, right ?

What do you mean by raising the overall level ? If I cut 20 - 30 hz and then boost the rest until around 70 hz in which case I then cut, is that not achieving the same result ? This time around, I almost had to cut 80 hz down all the way. This time around things were different. 

The level calibration I'm starting to get confused (and believe me, I am) with because if I achieve the flat result using a baseline volume on SMS-1 at 19 (for both unequalized and equalized graphs) then go and raise the levels using pink noise in AVR afterwards, I end up increasing the levels by 2-3 on the SMS-1 volume so the levels then become 21 on the SMS-1.

This is what I need to achieve 73-74 dB's for the subwoofer level (both in equalized and non equalized level). BUT....but and this is what I'm getting confused with... if I THEN go to the SMS-1 graph display, will my bass then not be out of proportion because I just raised the volume by 2-3 to give me the volume of 21 ?

This is my stumbling block.

Help would be appreciated. 

--Regards,


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## Doctor X

Alright, some new graph's.

Unequalized :










Equalized :










My last attempt in class :










Tell me what you think ?


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## Sonnie

You can place the <img> tags around your link instead of <url> tags and the images will be visible within your post... :T


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## Doctor X

I thought I tried that and nothing happened ! Gee whiz. . 

I tried the same thing over at Audioholics and nothing happened. I just put









Is that right ? 

--Regards,


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## Sonnie

Yep... or click on the







icon and type or paste in the URL of your image and click OK.


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## Kal Rubinson

Sonnie said:


> You can place the <img> tags around your link instead of <url> tags and the images will be visible within your post... :T


I see 'em just fine.

Kal


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## Doctor X

Heh. So Kal, what do you think of my results ? Can my graphs be improved and if so, what more could I do ? 

Perhaps I need to buy another PB10 ISD because once the subsonic limiter is disengaged, I'm boosting the low end baby ! 

Well, in moderation, of course. 

This is not necessarily to create a house curve but just to create a flatter in room response where my output below 20 hz will probably be several dB's down. The only other factor which I haven't even factored in is that the Radioshack meter is already inaccurate and reads low frequencies low.

So if I create a truly flat response from 15 hz up to my crossover region, will that be indeed flat or is my Radioshack meter going to be inaccurate because it reads low frequencies, um, low ?

Your advice would be helpful.

--Regards,


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## Sonnie

Kal Rubinson said:


> I see 'em just fine.
> 
> Kal


Yes, I edited them so that you can... :T


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## brucek

> The only other factor which I haven't even factored in is that the Radioshack meter is already inaccurate and reads low frequencies low.


I thought the SMS came with an ECM8000?

brucek


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## Doctor X

Brucek, it does come with the ECM8000. But I'm using the Radio Shack SPL meter to calibrate the actual SPL levels.

The behringer microphone is used with measuring and analysing room response.

--Regards,


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## Kal Rubinson

Vaughan100 said:


> Heh. So Kal, what do you think of my results ? Can my graphs be improved and if so, what more could I do ?


Move the mic around and see how flat the sub is in the listening area. One mic position = one ear position. 

Kal


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## brucek

> The behringer microphone is used with measuring and analysing room response


So why would you think the level at 15Hz would be any different than at 80Hz if you are using the ECM8000 to create the response from _15 hz up to my crossover region_?

brucek


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## Doctor X

Fine, I don't know what I was thinking typing that. Just forget I mentioned it, alright ? 

Edit : I forgot I was using a Behringer microphone for measuring. Duh !

Kal, but isn't the SMS-1 supposed to correct FR problems in a very small listening window ? I assume that if I move the mike to the other seat that the response is going to be different.

Why do you ask me to move the mike to other positions ? I asked what you thought of my graphs. So, what do you think of them ? Can they be improved ?

--Regards,


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## Kal Rubinson

Vaughan100 said:


> Kal, but isn't the SMS-1 supposed to correct FR problems in a very small listening window ? I assume that if I move the mike to the other seat that the response is going to be different.


 Very small window is right. Move the mic a foot in any direction and you should see lots of changes in the response. (Should, of course, but the SMS-1 display may be too smoothed to show it.) Do you listen with your head in a vise? I prefer to look at the region around where I sit since I do not always sit still and see if, perhaps, a compromise is better than optimal at one spot and bad near by.



> I asked what you thought of my graphs. So, what do you think of them ? Can they be improved ?


They look pretty good. Although I've seen better, I do not think there is a significant subjective difference.


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## Doctor X

> Do you listen with your head in a vise? I prefer to look at the region around where I sit since I do not always sit still and see if, perhaps, a compromise is better than optimal at one spot and bad near by.


I'm not sure what you are suggesting. I can't EQ more than one location unless I decide to get the MIC-5 which I certainly am not going to get.

If you prefer to listen in areas around your location (I'm not entirely sure why you would) how can you EQ in that location ? And if you could EQ in that location would it not inadvertantly mess up the "sweet spot" ?

Perhaps you could explain in better detail what you are trying to say.



> They look pretty good. Although I've seen better, I do not think there is a significant subjective difference.


Kal, in what way can my graph be improved ? I would really like your opinions on this. Looking back at my graph, perhaps I should lower the 50-80 hz material (it might be 2-3 dB's out) but then perhaps I'm going senile. At 24, you never know. 

I mean, in your great experience looking at FR graphs, is there any indication by looking at my latest graph that would give you reason to believe that perhaps music would be slightly heavy handed ? 

Or put another way, by looking at my graph, can I get the bass to sound clearer (flatter is cleaner, right ?) ? Thanks.

--Regards,


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## Kal Rubinson

Vaughan100 said:


> I'm not sure what you are suggesting. .......Perhaps you could explain in better detail what you are trying to say.


The corrections are VERY local. After all, it cannot be in the same place as BOTH of your ears. Moving less than a foot often gives different results. My suggestion is to measure what is going on in the immediate neighborhood of the first measurement position. If there is a downside to a correction, perhaps you want to back off a little so that at both positions, the EQ is good rather than excellent at one and ****** at the other. Get it?





> Kal, in what way can my graph be improved ? I would really like your opinions on this. Looking back at my graph, perhaps I should lower the 50-80 hz material (it might be 2-3 dB's out) but then perhaps I'm going senile. At 24, you never know.


While the 50-80Hz range could be smoother, what I am saying is that a smoother response may not be audibly better. See above: You are obsessing over measurements from one spot and what you want is good response in the area where you listen.


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## Doctor X

> If there is a downside to a correction, perhaps you want to back off a little so that at both positions, the EQ is good rather than excellent at one and ****** at the other. Get it?


I don't see why you have to be condescending with your "get it" remark. If I make one spot sound "good" then the chances of the other spot sounding "good" are not high because the locations are different as you just said. So I don't know how one would go about making two spots sound good. 



> While the 50-80Hz range could be smoother, what I am saying is that a smoother response may not be audibly better.


Isn't the 50-80 hz range more in the musical range as far as bass goes ? If so then surely creating a flatter region there would prove to be a positive and not a negative ?



> You are obsessing over measurements from one spot and what you want is good response in the area where you listen.


But the area in which I listen is 4" to the right where I measured ! Unless you are telling me that if I move the microphone 4 inches to the right that the results will be substantially out.

--Regards,


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## Kal Rubinson

Vaughan100 said:


> I don't see why you have to be condescending with your "get it" remark. If I make one spot sound "good" then the chances of the other spot sounding "good" are not high because the locations are different as you just said. So I don't know how one would go about making two spots sound good.


 First, just measure again and see if/how the results differ. If there is a substantial difference, you may want to settle for less flatness in one place in order to gain better responses over the listening area.



> Isn't the 50-80 hz range more in the musical range as far as bass goes ? If so then surely creating a flatter region there would prove to be a positive and not a negative ?


Right but not if it is at the expense of much less flatness right near by. I can hear (and measure) a huge shift in the 50-80Hz levels by moving my head about 8 inches in one of my setups. 



> But the area in which I listen is 4" to the right where I measured ! Unless you are telling me that if I move the microphone 4 inches to the right that the results will be substantially out.


What is 4" to the right of the mic? Which ear? There is no single spot unless you listen with one ear and have your head clamped firmly. One can have wide swings from node to null over very short distances in small domestic rooms and you don't want to compensate for one and yet listen in the other.


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## Doctor X

Thanks Kal.

--Regards,


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## Doctor X

Is it true that if I position my subwoofer away from the corner that the modal decay times will also be lower ? Because my subwoofer is in a corner right now and even Eq'ed flat, bass, although full sounding, can sometimes sound a bit fat.

Would taking the subwoofer out of the corner reduce the decay times do you think ? I also need some advice when setting the distance for the subwoofer with the SMS-1.

My current distance is 2.7 m but I've set it to 4.3 m. Output starts to increase up to the point of 4.3 m and then it starts to drop off so I assume that my current distance is accurate with the SMS-1.

Is there a procedure that one can go through to work out the best distance settings with the SMS-1 ? And I heard from one member that it also can accurately test the delay of the left and right front speakers. 

Thanks.

--Regards,


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## Wayne A. Pflughaupt

> Is it true that if I position my subwoofer away from the corner that the modal decay times will also be lower ? Because my subwoofer is in a corner right now and even Eq'ed flat, bass, although full sounding, can sometimes sound a bit fat.


Extended decay times are best addressed with absorption (a.k.a bass traps).
Frequency response problems are best addressed with equalization.

Regards,
Wayne


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## Doctor X

I understand that Wayne. But is it true that decay times will be reduced if I place the subwoofer away from the room boundries ?

Also, could you please answer my questions concerning distance with the SMS-1 ?

Thanks !

--Regards,


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## Wayne A. Pflughaupt

> But is it true that decay times will be reduced if I place the subwoofer away from the room boundries ?


Only in the sense that in an untreated room decay times are largely tied to signal level, and moving the sub away from the boundaries will reduce the signal level. So all you’ll be doing is reducing your sub’s output. Once you adjust its level to compensate, the decay times will be pretty much the same as before.

So the succinct answer is "no."



> Also, could you please answer my questions concerning distance with the SMS-1 ?


Aside from the fact that Velodyne makes it, and it appears to have some distortion issues, I don’t know a thing about the SMS-1.

Regards,
Wayne


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## Ayreonaut

I heartily suggest you move the sub away from the corner as much as is practical. Away from the wall 1/4 of the width and depth of your room is ideal, but most people can't place their sub out that far. (Mine is in the ceiling so I can.)

In the graphs that you've posted so far, there's no significant house curve. Try it, you'll like it.


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## Doctor X

If I manage to create a flat frequency response, how would I know where to start with a house curve ? 

I want music to be flat and not to over-accentuate certain bass notes. But I also want to feel bass down to the tuning frequency of my PB10 ISD. I read the article here on house curves but I still don't know what the curve itself must look like.

Furthermore, is a house curve accurate ? I've been told that if one uses a house curve that it is not being faithful to the original signal. But on the other hand, I've also been told that a house curve gives you a perceptually flat response.

Thoughts would be appreciated.

PS All those with SMS-1's, any advice on setting the distance levels or an easy way for me to determine what the distance must be set to ? Thanks.

--Regards,


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## brucek

> All those with SMS-1's, any advice on setting the distance levels or an easy way for me to determine what the distance must be set to ?


There's not much mystery about the distance setting. It's the distance from the seating position to the subwoofer, plus any additional processing time added by the DSP used for equalization. I have read that the SMS enjoys about 2.5ms processing time, so add 2.5 feet to the actual distance - that's it.

brucek


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## Kal Rubinson

Vaughan100 said:


> Furthermore, is a house curve accurate ? I've been told that if one uses a house curve that it is not being faithful to the original signal. But on the other hand, I've also been told that a house curve gives you a perceptually flat response.


Flat means measured flat. Anything(!) else is not flat regardless of the pleasure it may bring you.

Kal


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## Doctor X

Brucek,



> I have read that the SMS enjoys about 2.5ms processing time, so add 2.5 feet to the actual distance - that's it.


Why is it that if I increase the distance past this that the output tends to increase even more ? If I add 2.5 feet to 2.7 m (sorry, we South Africans use meters and not feet ) that would give me 3.45 m.

Setting distance to 4.3 actually yields more output. But is that a bad thing ? I need to understand why this is happening. 

Thanks.

--Regards,


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## Wayne A. Pflughaupt

> I want music to be flat and not to over-accentuate certain bass notes. But I also want to feel bass down to the tuning frequency of my PB10 ISD. I read the article here on house curves but I still don't know what the curve itself must look like.


How to determine the room curve you need is explained in the first part of the article.



> Furthermore, is a house curve accurate ? I've been told that if one uses a house curve that it is not being faithful to the original signal.


That’s addressed in the third part.

Regards,
Wayne


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## brucek

> Setting distance to 4.3 actually yields more output. But is that a bad thing ? I need to understand why this is happening.


This tells the receiver that the sub is further away and so advances the signal sooner. This mixes with the mains in such a fashion that the resultant signal adds to a higher value. Nothing is bad or good. If you like the sound, do it. You have been given the general rules and why. If you want to change it from 3.45 meters because it results in a better signal, then do that.

brucek


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## Doctor X

Brucek, the bass sounds boomier when it's set to 4.3 meters (greatest output) and sounds actually less muddy at 3.43 meters (but there are slight dips in the response around the crossover region) which is more or less the distance that is required for the SMS-1.

I know that sound is subjective but I also don't want to be setting my system up incorrectly. Thanks.

--Regards,


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## Doctor X

Very disappointing day today, because I had to move the subwoofer back which messed up all my settings. I can't get the response to look as good as before either.

Bummer.

I tried for one hour to get my response relatively flat but it's getting harder and harder now. Right now, with EQ, pretty much all my EQ sliders are set to near maximum. Funny thing is, even before I moved the sub, I think most of my sliders were set to near maximum as well.

I'm not joking either. Otherwise from 50hz to 80 hz there are huge drop off's. Far better than what it was but it's the only way for me to get that punch back. I don't know if this is because of my SVS PB10 not giving good output in the 50 to 80 hz range, if it's because of my speakers or if it's solely because of cancellation. 

Regardless, I guess I need to invest in some bass traps. But I still don't quite get the Q factor.

I understand that it can vary the FR in a narrow band or in a wider band but what I don't understand is that I can increase almost my entire graph by just setting one EQ slider to minimum Q. Currently, I have almost all EQ sliders set to maximum but almost all of them vary from 3.5 to 6.5 Q. 

Can Q values alter the sound even if the graph remains flat ? What I mean by that is, if the graph is relatively flat with Q set at a low level would it sound identical to a high Q setting yielding the same flat response ? 

Perhaps I must set a few EQ sliders to a low enough Q so that all the levels are much higher and then decrease the individual EQ sliders so that I'm not boosting all the levels. Maybe someone can chime in and explain what is happening and what is the necessary step in my case.

Thanks.

--Regards,


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## Doctor X

Maybe I should post a pic showing the EQ sliders I currently have.

--Regards,


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## Doctor X

Is everyone asleep ? 

--Regards,


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## Ayreonaut

We're at work!

Q is a measure of sharpness. When you minimize Q, you are creating a wideband filter that will affect the entire subwoofer range.

I measure response at four listening positions, compare the average response to my desired house curve, and filter the peaks for the average response. That way I know I am treating room resonances, rather than localized cancellations. The end result is that the response at any individual seat doesn't measure "perfect," but it sounds great in any seat.


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## Doctor X

But if a low Q "lifts" the entire range or almost, then would it be wise to just use a low Q and then to cut whatever needs to be cut instead of using a higher Q ? Because if I use a high Q then I need to boost certain frequencies more than usual to get a flat response.

Seems to me that one can get a whole lot of free output by simply taking one band of EQ and using a very low Q. Everything just goes up and up. 

--Regards,


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## brucek

> Seems to me that one can get a whole lot of free output by simply taking one band of EQ and using a very low Q. Everything just goes up and up


This statement leads me to believe you have a weak understanding of Q and bandwidth. Take some time to read up on these concepts.

I re-read this thread and can't see how I could say anything new to you that hasn't been covered already.

Have you considered using the SMS Auto EQ feature. This would likely offer you a suitable result.

brucek


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## Wayne A. Pflughaupt

> Right now, with EQ, pretty much all my EQ sliders are set to near maximum. Funny thing is, even before I moved the sub, I think most of my sliders were set to near maximum as well.


Not good. When things get like this it’s time to set everything back to flat and start over. Not to mention, you’re killing your extension, as response below the lowest filter will roll out with the filter.

Taking another look at your earlier pictures...






















...that hump centered around the 80 Hz slider (top picture) could have been dealt with by cutting it down. Probably would have taken only one or two filters to accomplish it. Instead, you used a multitude of filters to boost up everything else around it. This is inefficient equalization.



> what I don't understand is that I can increase almost my entire graph by just setting one EQ slider to minimum Q.


That would be a broad filter. Yes, they will affect a large area.



> Can Q values alter the sound even if the graph remains flat ?


You bet, especially if you’re using narrow filters.



> Seems to me that one can get a whole lot of free output by simply taking one band of EQ and using a very low Q.


There’s no such thing as free output. All you’ll be doing is sending a hotter signal (read voltage) to your sub.



> Maybe I should post a pic showing the EQ sliders I currently have.


REW graphs would be a lot more helpful.

Regards,
Wayne


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## Doctor X

I apologize if I'm not understanding things properly but I am new to all of this. I don't think the manual (Outlaw or otherwise) goes into depth on Q but rather simplifies the explanation.

Obviously now I'm getting more indepth answers concerning Q which no manual would likely give me. Wayne, you said that narrow Q filters can alter the sound. In what way ? Can you add boom to the sound that is not supposed to be there ?



> Not good. When things get like this it’s time to set everything back to flat and start over. Not to mention, you’re killing your extension, as response below the lowest filter will roll out with the filter.


Alright I think I will start over. Please explain a little more about the "killing the extension" part. I don't completely understand that. Thank you.

Remember I said a while back that once I had Eq'ed my response the bass was fuller but also sounded boomier ? Well perhaps me using different EQ bandwidth's is the cause.

Brucek, again, sorry if I'm not up to speed on this as I very much would like to be up to your level of understanding all of this. Alas not yet. Because for me, I'm finding things are getting unpredictable with these variables.

Now I'm not sure why I would want to use a narrow bandwidth filter instead of a wider one (yes, I know what they'll do to my graph but that is oversimplifying it) but I'm not sure what audible degradation or improvement I'll get for using narrow filters. 

In your experiences, do narrow filters give better sound than wider ones ? Thank you all for your advice and patience.

--Regards,


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## JohnM

Are you able to run REW, Vaughan? Even without taking measurements you can put filter settings into REW and adjust the Q values and see the effect that has on the overall correction you are applying, that should help you get a handle on the effect of the Q control. Your aim should be to match the Q (shape) of the filter to the shape of the hump or peak you are trying to correct with it, and have the gain set to the opposite of the height of the hump/peak - a narrow peak needs a narrow (higher Q) filter to counter it. Applying filters with gain (rather than loss) to correct your response is something to avoid. Filters with gain act like room resonances, they increase the decay time at their centre frequency so can give you a boomy character. The narrower the filter (the higher the Q) the longer the decay time and the more of a problem is created. It is best to use filters to cut peaks then use the gain control on your sub to raise the overall level back to where you want it.


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## brucek

> Even without taking measurements you can put filter settings into REW and adjust the Q values and see the effect that has on the overall correction you are applying, that should help you get a handle on the effect of the Q control. Your aim should be to match the Q (shape) of the filter to the shape of the hump or peak you are trying to correct with it, and have the gain set to the opposite of the height of the hump/peak


For example - below is a picture of two filters of equal -6dB gain at 25Hz and 80Hz for demonstration. 

One has a Q=10 and one has a Q=1. The difference in their effect is quite dramatic. 

You must match the filter +/- gain and Q to the peak you are trying to control. Super low Q simply raises or lowers a very wide area as you noted when you said, _"Seems to me that one can get a whole lot of free output by simply taking one band of EQ and using a very low Q. Everything just goes up and up_. Look at the picture of the two filters and see why that is so. You need to pick a single peak in your unfiltered response and start with a high Q (narrow bandwidth) filter with some negative gain and see its effect. Then widen the bandwidth (decrease Q) until the peak is gone.









brucek


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## Doctor X

John, sorry, I've been unsuccessful in getting REW to work. I think my sound card chipset is problematic. I will buy a better sound card because I really want to use REW.

If for nothing else, I want to see modal ringing. But with the SMS-1, it's difficult for me to grasp the concept of using a high Q and a low Q to correct FR anomalies especially when for all I know, if I do reduce a peak, I still might have the boom associated with it because the level of Q I'm using is too high.

It's not enough that I reduced the level or flattened the level to create a flatter in room response but now I need to make sure that I am not using high enough Q settings to get there. It seems confusing to me especially when this was not discussed in any manual that I'm aware of.

And what if I don't have any specific peaks in my response but dips ? The whole time I've been describing this boomy character it hasn't simply been the increased levels of bass (because the gain levels have been greatly increased for the dips) but the Q settings have been less than optimal which has led to this one note bass.

I would have never known this unless I spoke to you guys. One guy told me that perhaps my room was resonating more at the frequencies that I _increased_ in gain which would give me the impression of boomy bass. 

So if I'm understanding things, using a low Q will give lower decay times than a higher Q setting ? 

--Regards,


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## JohnM

The Q setting of the filter is of most concern if you are using filters to boost level. Filters that boost have the same characteristics as room resonances, and the higher the Q of the filter used to boost the longer it will ring. When you use a filter to cut level the filter will add little or nothing to decay time, even if it has quite a high Q. For filters that are used to cut, the Q is used to match the shape of the filter to the shape of the peak it is countering. If the filter is accurately matched to a peak that is due to a room resonance (most are) it will reduce the ringing at that frequency.


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## Doctor X

Is there a way to accurately match the Q filter to target the resonance without using software ? Are there any methods you know of or is it just in my best interest to get the software working.

I just bought the SMS-1 and I don't want to neglect it. 

--Regards,


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## Doctor X

John, so then are you telling me that if I boost frequencies that I will have to live with the boomy character ? There is no way to boost and to get as little decay as possible ? 

Or no added decay ? Thanks !

--Regards,


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## JohnM

Vaughan100 said:


> Is there a way to accurately match the Q filter to target the resonance without using software ? Are there any methods you know of or is it just in my best interest to get the software working.


Getting an accurate match without using some kind of measurement software is all but impossible. To get a rough Q setting from the response on your SMS-1 display, estimate how far a peak is above where it should be, estimate how wide the peak is at half its height and set Q to (centre frequency)/(peak width). You can also use REW to manually adjust filter shapes to get something that looks similar to the response on your SMS-1 measurement, or make a text file of your best guess of the frequency & SPL readings from your SMS-1 measurement and import those numbers to REW so you can match them up that way.



Vaughan100 said:


> John, so then are you telling me that if I boost frequencies that I will have to live with the boomy character ? There is no way to boost and to get as little decay as possible ?


If you use Q values below about 3 the increased decay time is unlikely to be audible, but bear in mind that dips in the response can be very localised so a small distance away from your measurement point the boost could be acting on an area where the dip isn't present and you will hear the emphasis at that frequency. Boosting gives very poor results, and much of the boominess will be due to the peaks in the response, boosting adjacent regions does nothing to help that.


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## OvalNut

Rather than boosting all the filters, why not increase the sub gain, then level the freq resp with cuts instead?:scratchhead:

Tim
:drive:


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## Doctor X

My graph now looks different and I'm not using nearly as many filters to boost. I'll post a graph shortly.

Many thanks.

--Regards,


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## Doctor X

I just wanted to add that if I don't bump up the bass in the 50 to 80 hz region (where most of the dips are), the punch that is supposed to be there is almost nonexistant.

When watching certain films, I've noticed that I actually get a lot more of the "punch in the chest" moments than without the boost. It makes sense too because I had a serious lack of power in those critical bass regions. I think 50 to 80 hz is where the punch in the gut bass is anyway.

If I just cut one or two peaks and have a huge dip (actually more of a null because the levels are reduced by a factor of 6 dB's or more) then I'm going to be without the punch and have less bass.

I don't want to do a house curve just yet. I'm actually getting used to the whole chest slam effect because I had none before and I only have a single PB10. Granted, it's not really a chest slam but more of a subtle "something is hitting me ever-so-slightly" feeling which causes me a bit of discomfort after repeated viewings.

The best part is that this is supposed to be there. If I had a room filled with bass traps I probably would have all that punch retained but without much ringing at all. 

I hate ringing. 

--Regards,


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## Wayne A. Pflughaupt

Vaughan100 said:


> I apologize if I'm not understanding things properly but I am new to all of this. I don't think the manual (Outlaw or otherwise) goes into depth on Q but rather simplifies the explanation.


I’m not really keen on manufacturers using Q values for bandwidth as its not readily known or understood by audio novices – as you are experiencing. I find bandwidth expressed as octaves easier to comprehend, and adjust filters to. Here’s an old post of mine discussing bandwidth as octaves that might help clarify:

Wayne P on bandwidth

If you really determined to get a handle on Q, try this:
brucek on bandwidth

Scroll down this page a bit for a handy Q-to-octaves conversion table:
Q to octaves conversion table



> Wayne, you said that narrow Q filters can alter the sound. In what way ? Can you add boom to the sound that is not supposed to be there ?


If filters get too narrow, you can actually be equalizing specific bass notes, if the filter happens to fall on the center of a fundamental of a note. There won’t be any boom with narrow filters – that would typically happen with broader filtering.



> Please explain a little more about the "killing the extension" part. I don't completely understand that.


Maybe this picture will help. It shows what happens to response when numerous filters are boosted to max.







​

Assuming a flat starting point (0 dB line at center), the crude red lines I inserted shows the ragged, saw-tooth response you end up with, that basically tracks the filter peaks. At the bottom end, response will “chase” the lowest filter and cause a sharp drop-off below its frequency center.

For example, if your sub was flat to 18 Hz before equalization, and you add a bunch of boosting filters, with the lowest filter being 25 Hz, your response now falls off rapidly below 25 Hz. Make sense?

Regards,
Wayne


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## Doctor X

Thanks Wayne ! I'll take a look at those articles.

--Regards,


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