# SUB PLOT - Would you add the filters?



## MakeFlat (Mar 30, 2007)

:scratchhead: The attached graph shows the average curve for 3 listening positions. The effect of filters is shown in dashes. Would you add the filters as REW suggested or just lower the sub's output by 5 db?


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## Sonnie (Apr 11, 2006)

That actually looks pretty good without filters, but I'd flatten it out anyway, just because I could. You could boost that 29Hz back up and it would still effectively be a cut. You could also bring that minor hump at 50Hz on down. Just enter a couple of filters yourself.


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## Otto (May 18, 2006)

Yep, I agree with Sonnie.


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## bossobass (Jul 16, 2006)

Just my opinion, based on many hundereds of graphs using many different subs in many different locations...

It makes little sense to EQ a response without the satellites being included in the sweep. If you EQ the sub only, you may be making the end result worse when the sats are turned on.

Using a standard 80Hz crossover point, the mains can have effect down into the 30Hz range. You should always follow the standard regimen before post EQ (with sats on):

1. Absolute phase.
2. Location.
3. Volume leveling of sats to sub(s).
4. Relative phase (or, delay settings).
5. Final volume leveling.
6. Post EQ.

IOW, the graph shown makes it impossible to suggest whether or not post EQ should be applied, and where to apply it, if at all, IMO.

Bosso


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## Sonnie (Apr 11, 2006)

I'd say I've looked at a few graphs as well, but I can't remember one where 30Hz was affected by the mains crossed over at 80Hz. Not saying there aren't any... just saying that it's most likely be a very small percentage.

Either way, we've been making suggestions in this way since 2001, measure the sub only... equalize it and then measure with the mains to see the interaction, since most of us only have the option to eq the sub. Maybe we've been doing it backwards for 6 years :scratch: ... but it's been effective. :nerd:


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## Wayne A. Pflughaupt (Apr 13, 2006)

Well, I can see Bosso’s point. I had some trouble with this myself. You EQ with the sub only, run a fresh sweep adding the mains, and see changes that need to be made. Problem is, your new sweep wants to use all-new filters - it won’t allow you to open up and modify your existing filters. You have to tweak Chart B with filters from Chart A, then sweep and check Chart C to see if the filter tweaks got what you wanted. (‘Course, it’s highly possible that REW will allow you do a second sweep using existing filters, and I just don’t know about it...)

Typically response changes when adding the mains will show about an octave above and/or below the crossover point, in my admittedly limited experience. With an 80 Hz crossover, response from the mains should be down more than 30 dB at 30 Hz compared to the sub – too low to register. 

Still, I can imagine some scenarios where the mains might make an impact down there. For instance, if your mains were really too big and bass-heavy for your room, effectively flattening much of the crossover roll-out, and you had a room mode at 30 Hz on top of that. The EQ would eliminate the peak in the sub, but it would still be present (albeit to a lesser extent) in the mains, which would show up with a combined sweep. Unusual yes, but certainly not out of the realm of possibility. 

Regards,
Wayne A. Pflughaupt


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## bossobass (Jul 16, 2006)

Sorry guys, I'll be more specific...

I use amps that all have signal and clip indicator lights. When I used to use separate 1/12 octave sine wave tones, I would keep an eye on the indicator lights of the amps for the mains to see when the mains were getting enough signal from the crossover to light them up as the tones increased in frequency. That point was always somewhere in the 30sHz, not exactly 30Hz.

As far as only having EQ for the sub, the location, leveling and phase/delay tweaks all affect the interaction between the sats and subs. PEQ on the sub will also affect the interaction in that it introduces phase changes in many cases also.

Keep in mind that the stock pre/pro crossover is a 2nd order HP on the mains and a 4th order LP on the sub. Add to this the fact that the room gain and boundary gain effects are not influencing the sub up above cross, but certainly are influencing the mains below cross. You can imagine that the crossover ends up being nothing like the intended 4th order Linkwitz/Riley across 2 octaves.

It's also interesting to switch the pre/pro from stereo to 5 stereo when taking a measurement to see the effect of tweaks across the LCR, etc, especially right at the crossover point.

Maybe we could ask the OP to show a graph of the sub only, sub and mains, then sub only with EQ and finally, the sub with EQ with the mains added? Then, finally, sub with mains added with EQ applied to that combination (instead of applying EQ to the sub only first). Might be educational.

Bosso


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## Sonnie (Apr 11, 2006)

I see your point to a point and it makes sense. 

Here's where I see the challenge and I've run into this before with some of my previous systems from way back. You measure the sub only... then the sub + mains and see a 6db peak at 60Hz that appears with the mains, but wasn't there with the sub only. So you try to filter the peak at 60Hz but nothing moves... it just stays there. Of course you can try phase adjustment and it might help.

I found myself aggravated to death one day... I had a serious peak at 100Hz that I thought the sub was causing. I ultimately filtered it to -48db and it didn't budge. I was :scratching: ... then I figured it out... ahhh, my mains were still on and I wasn't paying any attention at all to that fact. I was trying to adjust something that couldn't be adjusted. If I remember correctly I was able to help that peak with the tone control on my pre-pro at the time.

But generally I've helped a lot of people adjust the sub only to flat or a house curve and the majority of the time when the sub + mains is played, it looks good. Honestly, I can't even remember the last time it was an issue. Again, I'm not gonna say that it's not an issue and I am definitely not gonna suggest to anyone that it's not necessary... they can proceed as they wish. It certainly will not hurt to measure both ways prior to eq'ing... :T


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## Wayne A. Pflughaupt (Apr 13, 2006)

> But generally I've helped a lot of people adjust the sub only to flat or a house curve and the majority of the time when the sub + mains is played, it looks good. Honestly, I can't even remember the last time it was an issue.


Yup – it’s not common, but it does indeed happen. The tell-tale complaint goes like this:” I cut that peak xx dB [_insert ridiculously severe number_] and it won’t budge!” 

Regards,
Wayne A. Pflughaupt


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## MakeFlat (Mar 30, 2007)

Thank you all for the recommendation on what to record. Okay, here is the FR of the sats and sub blended.


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## Sonnie (Apr 11, 2006)

Actually you should still only post the graph from 15Hz to 200Hz, even when looking at the mains + sub... and post the sub only graph as well.

Btw... I just uploaded the latest RS correction values yesterday... make sure you use those.


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## MakeFlat (Mar 30, 2007)

Sonnie said:


> Actually you should still only post the graph from 15Hz to 200Hz, even when looking at the mains + sub... and post the sub only graph as well.
> 
> Btw... I just uploaded the latest RS correction values yesterday... make sure you use those.


Alright I have put the curves on on a graph from 15-200Hz. When I ran REW, the oldrsanalog.cal was in effect. The new calibration file RADIO SHACK 33-2050.cal was loaded just now and is now ready to use the next time I run REW.

The curves are attached:


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## brucek (Apr 11, 2006)

> When I ran REW, the oldrsanalog.cal was in effect. The new calibration file RADIO SHACK 33-2050.cal was loaded just now and is now ready to use the next time I run REW.


You don't need to redo any measurements because of the new mic calibration file though, because the soundcard and meter calibration data isn't included in the impulse response. The mic/meter and soundcard calibrations are only applied when calculating the frequency response.

So if you saved your mdat file, then to apply or remove a mic/meter or soundcard calibration for an REW measurement after it has been taken, simply load or clear the cal data as required and press the Apply Windows button (invoked when you click the IR Windows ICON) to recalculate the frequency response with a new calibration file.

brucek


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## MakeFlat (Mar 30, 2007)

brucek, thank you very much for the time-saving tip.


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## bossobass (Jul 16, 2006)

MakeFlat said:


> Alright I have put the curves on on a graph from 15-200Hz. When I ran REW, the oldrsanalog.cal was in effect. The new calibration file RADIO SHACK 33-2050.cal was loaded just now and is now ready to use the next time I run REW.
> 
> The curves are attached:


Hi MakeFlat,

Thanks a lot for the effort:whew: 

As I suggested earlier, and you can clearly see, the sats do indeed have influence down to the low 30sHz.

It looks as if you're running your sub about 6-8dB hot?:scared: 

Is the crossover point still at 100Hz for these graphs?

Where do you have the distance set for the sub in relation to the mains?

Where is the relative phase control set?

Bosso


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## Sonnie (Apr 11, 2006)

Actually in the real world it won't really look like that, will it? Isn't the LFE on DD and DTS tracks 10db hot? On top of that, if you add a house curve, which many people tend to do, the sub response is going to be considerably higher than the mains and thus the mains will not be effecting the response below probably 80Hz.

Either way, it still would not keep me from attempting to level the sub response as best I could.


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## MakeFlat (Mar 30, 2007)

bossobass said:


> Hi MakeFlat,
> 
> Thanks a lot for the effort:whew:
> 
> ...


Bosso,

You are right - the sats' influence go down as low as the low 30's.

The sub is in phase with the sats. I checked that a while back using the THX test that is included with some DVD movies. The sub is 2 ft behind the right sat that is 9 ft from the middle listening position. As for the crossover, it is set at 100Hz.

The sub looks like it's about 6 db too hot compared to the midrange. The sub also appears to be 6db above the reference SPL of 75dB when tested by itself, with the sats disconnected (shown on my first post in the same thread). I am quite puzzled :scratchhead: by this but perhaps this is normal - the graphs I have seen by others also have the curve hovering above the reference line, except where the sub takes a dive at 24dB/octave.


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## Sonnie (Apr 11, 2006)

Here's an example of my response with all my levels set properly...

Red = Sub Only
Gold = Sub + Mains










In most cases with the levels set properly, this is what I see over and over and over... very little interaction below the crossover point.

If you are getting that much interaction down into the 30's, I'd suspect your levels are probably not set the same as most I've seen.


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## MakeFlat (Mar 30, 2007)

Sonnie said:


> Here's an example of my response ...
> 
> In most cases with the levels set properly, this is what I see over and over and over... very little interaction below the crossover point.
> 
> If you are getting that much interaction down into the 30's, I'd suspect your levels are probably not set the same as most I've seen.


Sonnie,

Perhaps it's a level issue. I am also seeing that my mains are not rolling off below 100Hz, the crossover point. They seem to roll off at 40Hz. Hmm... I wonder if it has something to do with the Denon 1604 "Direct Mode", or is it because it is a bottom of the line Denon. Question: Would it be better to use PLII Mode on the A/V Receiver when running REW? I am thinking that may be the "Direct Mode" would not have full bass management, on a low budget receiver like the 1604.onder:


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## Jerm357 (May 23, 2006)

You dont have a stereo setting?


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## Otto (May 18, 2006)

MakeFlat said:


> I am thinking that may be the "Direct Mode" would not have full bass management, on a low budget receiver like the 1604.onder:



I think you are correct that the Denon isn't doing any bass managemnt in Direct Mode, and it's probably not because of its price tag. 

Generally, Direct Mode is for those that want a quick selection that will allow them to listen to audio directly without any digitizing or other overhead that could modify the signal from the original. I would imagine that your bass and treble controls are also disable in Direct Mode. 

If that's the case, you should just find a mode that _does _apply bass management to a stereo signal (as Jerm357 suggested). That's the only way to make an accurate measurement of your mains/sub setup. If you are not seeing a rolloff in your mains at the crossover point, you are not high-pass filtering them.


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## brucek (Apr 11, 2006)

> I think you are correct that the Denon isn't doing any bass managemnt in Direct Mode, and it's probably not because of its price tag.


That's certainly apparent from the response curve supplied.

A 100Hz crossover will result in the mains having negligible effect on the response below ~50Hz. The mains would enjoy an HPF of -12db/octave from the bass management combined with the speakers natural 2nd order dropoff to result in the diagram you see below. Take your receiver out of Direct mode and use stereo to engage the bass management.









brucek


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## woozy_one (Oct 20, 2006)

MakeFlat said:


> The sub also appears to be 6db above the reference SPL of 75dB when tested by itself, with the sats disconnected (shown on my first post in the same thread). I am quite puzzled :scratchhead: by this but perhaps this is normal - the graphs I have seen by others also have the curve hovering above the reference line, except where the sub takes a dive at 24dB/octave.


I've also wondered about this.


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## bossobass (Jul 16, 2006)

brucek said:


> That's certainly apparent from the response curve supplied.
> 
> A 100Hz crossover will result in the mains having negligible effect on the response below ~50Hz. The mains would enjoy an HPF of -12db/octave from the bass management combined with the speakers natural 2nd order dropoff to result in the diagram you see below. Take your receiver out of Direct mode and use stereo to engage the bass management.
> 
> ...


Yes, it would be nice if the in-room roll off of the mains would look anything like the graph you posted, but the reality is that standing waves and room and boundary gain can grossly attenuate that HP filter-imposed roll off.

If you look at the graph MakeFlat posted, it seems that there is a LP filter on the sub that's much lower than 100Hz. It would be odd to me if the mains had no filter (because his receiver's 'direct' mode has no BM), but the sub did?? My pre's direct mode has BM, so I'm not familiar with one that imposes a LP but no HP.









Looking at Sonny's sub/sub+mains graph, the sub appears to be 10dB or more hot, which would swamp the crossover's intent for unity gain across the crossover region. If you properly level the sub and mains, at least leveling them at the crossover point with an 80Hz tone, first the sub only, then the mains only, then overlay a few graphs with the relative phase control at different positions, it might give a better picture of the mains influence.

I'll post a graph later in the week when I get some time to run a few sweeps.

Interesting stuff. Sorry if I'm boring anyone. Thanks again for the graphs.:jump: 

Bosso


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## Sonnie (Apr 11, 2006)

Again, the LFE, which will respond up to 120Hz, will be 10db hot on DD and DTS tracks, therefore my graph would be more indicative of real world response. :T


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## bossobass (Jul 16, 2006)

Sonnie said:


> Again, the LFE, which will respond up to 120Hz, will be 10db hot on DD and DTS tracks, therefore my graph would be more indicative of real world response. :T


Actually, according to the original patent application by Cirrus Logic back in Feb. 2002, it goes like this:

"In cases such as Dolby configuration 1 [all sats to 'small', sub to 'yes'] a gain of 10dB is not directly applied to the LFE channel to drive the subwoofer. Instead, the inputs to summer block 802 are attenuated to acheive the same result. In this example, the L, C, R, Ls and Rs channels are all attenuated by -15dB and the LFE channel attenuated by -5dB. This implements the LFE+10dB channel specified for Dolby Configuration 1. However, a compensating 15dB gain should be applied later, usually in analog after the DACs."

So, we see that 10dB is not added to the LFE channel, but rather, 10dB of headroom is added.

Bosso


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## MakeFlat (Mar 30, 2007)

Okay. Here's a graph that shows stereo versus direct mode:

The bottom graph shows 2.1 ch direct mode, 5.1 PLII cinema mode, and subwoofer respectively, with BFD filters applied. 

Edit: it appears that turning on the SUB caused the FR to dip at 200-300Hz. Why?


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## MakeFlat (Mar 30, 2007)

Okay. I now have the average of REW sweeps showing the curves before and after BFD. It looks like it is going to be tough to level the peaks at 50Hz and 90Hz without EQ'ing the mains. Perhaps I can replace the mains with smaller ones. Presently the mains can play down to 48Hz per Boston spec. If I swapped the surrounds (BA CR55, -3db @80Hz) with the mains (CR85, -3db @48Hz), do you think it might help?

Edit: Green - before BFD; purple - after BFD filters added. I showed only the two filters at the problematic peaks. I did the averages and then applied 1/3 octave smoothing. All previous graphs posted by me in the current thread used 1/1 octave smoothing.


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## brucek (Apr 11, 2006)

> I did the averages and then applied 1/3 octave smoothing. All previous graphs posted by me in the current thread used 1/1 octave smoothing.


Don't use any smoothing at low frequencies such as this. Smoothing is intended to be used for full range measurements when reflections cause comb filtering. 



> Green - before BFD; purple - after BFD filters added


It looks like almost no filtering has been done. You should be able to remove the peak at 50Hz with the BFD and I would think phase or time adjustmet would reduce the peak at 90Hz...

brucek


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## MakeFlat (Mar 30, 2007)

brucek said:


> Don't use any smoothing at low frequencies such as this. Smoothing is intended to be used for full range measurements when reflections cause comb filtering.


:duh: Thanks for the great reminder.




> It looks like almost no filtering has been done. You should be able to remove the peak at 50Hz with the BFD and I would think phase or time adjustmet would reduce the peak at 90Hz...
> 
> brucek


Apparently, the effect of filtering was washed out by the two mains. However, the graph that shows the sub by itself looks like the filters did a good job - only to be washed out by the two mains. As for time adjustment, I can only think of Audyssey. So perhaps a sub with continuously adjustable phase would help? Any PEQ that has phase adjustment?


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## bossobass (Jul 16, 2006)

MakeFlat said:


> Okay. Here's a graph that shows stereo versus direct mode:
> 
> The bottom graph shows 2.1 ch direct mode, 5.1 PLII cinema mode, and subwoofer respectively, with BFD filters applied.
> 
> Edit: it appears that turning on the SUB caused the FR to dip at 200-300Hz. Why?


Pretty cool.

This shows the flaw in thinking that the natural roll off of the mains combines with the 2nd order HP to result in a 4th order roll off. Actually, the vast majority of mains are ported, so it would really be thought to result in a 6th order roll off.

At 100Hz, the crossover affects it's roll off well above the (most) main's natural roll off, so the resulting roll off is 2nd order, which the graph (of the mains with 100Hz HP) verifies. From 100Hz to 50Hz (adjusting for the room induced hump at 50Hz) is 12dB of drop.

And, the influence of the mains on the sub+mains graph is to the low 30sHz, with a 100Hz HP in line.

You might try tweaking the placement of the mains. Sometimes it helps. Use a tape measure to get the FL, C and FR the same dimension from tweeter to head position if your layout allows for it. Also, notch the SW level down 3dB and see if that helps the overall response at all. Also, you can try little placement tweaks on the sub, sometimes a little nudge this way or that helps (in your case, the dip at 80Hz).

Did you say that you only have the 100Hz crossover option? Trying a 60Hz cross point would probably help the hump at 50Hz.

Bosso


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## brucek (Apr 11, 2006)

> Apparently, the effect of filtering was washed out by the two mains. However, the graph that shows the sub by itself looks like the filters did a good job - only to be washed out by the two mains


Then you need to be a bit more aggressive with the BFD filtering at 50Hz to compensate for the addition of the mains to get that hump lower.



> As for time adjustment, I can only think of Audyssey. So perhaps a sub with continuously adjustable phase would help? Any PEQ that has phase adjustment?


Use your speaker distance settings for time adjustment.

brucek


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## MakeFlat (Mar 30, 2007)

brucek said:


> Then you need to be a bit more aggressive with the BFD filtering at 50Hz to compensate for the addition of the mains to get that hump lower.


I will try that. I will also try plugging up the reflex port of the mains.



> Use your speaker distance settings for time adjustment.
> 
> brucek


:duh: I forgot to add a foot to the SUB setting to account for the BFD delay!! But will that contribute to the humps of the mains? Yeah I will recheck all the distance settings. Thank you very much Bruce. If anyone else have other ideas for my next REW run, I will appreciate it. I always plan for my next REW run because I don't get to do it that often when my family members would be out of the house.


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## Sonnie (Apr 11, 2006)

> And, the influence of the mains on the sub+mains graph is to the low 30sHz, with a 100Hz HP in line.


I still believe that for the vast majority of people this is caused by a level issue. I still conclude that this is absolutely not common place with all the graphs I have looked at over the years. Generally, most users are not happy with their bass when equalized to flat with the mains, hence the house curve.

Nick, you may end up liking it, who knows, but I believe you will end up being like the majority and once you get your sub level up properly to where the mains are not interfering with the sub response, you'll be happier with the sound. Personally if I dropped my sub level any, I would be without bass. Again, the response graph I show above is generally what I have seen for years and what most people like, however, there are exceptions, obviously Bosso being one of those.


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## brucek (Apr 11, 2006)

> I forgot to add a foot to the SUB setting to account for the BFD delay!! But will that contribute to the humps of the mains?


The answer is that it's a **** shoot. You have to use REW to find out. This is why you first took care of the equalization with the sub and then added the mains after to see how they affect the overall response at and around the crossover. Then you fine tune the filters, phase, placement, time variables to make it perfect.

brucek


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## bossobass (Jul 16, 2006)

Though I agree that the average listener prefers a sub-100Hz-heavy presentation, the proper calibration of a subwoofer into any system should be to a flat response for a reference setting. Deviation from there is personal taste and may vary for different source material, but an occasional return to the reference setting is a quick reality check.

In almost every HT I've installed and set up that I've later returned to for whatever reason, I've found the subwoofer levels to have been bumped to what I believe are simply absurd levels. This novelty usually wears off and a more accurate level is sought as time goes on...in most cases...in which case having a reference flat setting to instantly return to is a good thing, especially where a PEQ with presets is concerned.

I still disagree with those whose philosophy is to EQ the sub first, then add the mains. Seaton likes to include the center channel, some use the mains and I prefer to include all of the sats that are set to 'small' when calibrating the subwoofer.

MakeFlat's is a good case in point where the mains do things that aren't expected and need to be dealt with to smooth out the transition, and I've found it to be typical, YMMV.

On the subject of adding delay to compensate for upstream electronics, it's easiest to continue to add delay until the best response is arrived at, mostly because it's impossible to predetermine the total delay caused by things like BM and digital PEQ. Just run a sweep with the sats+sub, add delay, run another sweep, etc., until you see the best overall response.

PEQ should be the last tweak and used sparingly because most often a hole dialed into the input signal can begin to sound like compression when it reaches excessive amounts.

Just my opinions based on experience and many stupid questions to Ilkka, Ed Mullen, Seaton, Siegfried and others over the years.

Looking forward to the next sweeps session:jiggy: 

Bosso


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## MakeFlat (Mar 30, 2007)

Wow, I have read many instructions, suggestions and great ideas by Bosso, Bruce, Sonnie, Wayne, Otto and Jerm - not necessarily in that order. 

You all gave me good ideas in translating theory into practical action items. While all the technical terms sound clear to me, I am still having some hangups when it comes to actually trying to effect some changes indicated by some of the technical terms. But that may be because I am an acoustic newbie. 

I have the House curve still in mind and I will tackle that as soon as I get a practically flat curve for the subwoofer and the mains together. I may find something I did not find in the last 10 years I have had my sealed Sub (I wish they made many acoustic suspension speakers). In my not so good math, I calculated that if I EQ'd the sub with a -infinity gain (I think -48dB on the PEQ would be a practical equivalence), I could level an overall (mains+sub) peak by merely -3dB at the most. I am only expecting myself to EQ to +/- 5dB variation - that's the idea I get after reading many articles on room acoustics in the LF region of 300Hz and below. Correct me if I should do otherwise.


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## brucek (Apr 11, 2006)

> I have read many instructions, suggestions and great ideas


Everyone has different experiences and training that mold their ideas. You have to see what works for you. Not too many of us will ever disagree on the fact that peaks below the crossover frequency should be reduced.



> Correct me if I should do otherwise.


I definitely think you should try levels, treatment, positioning, delay and phase with REW first and then think about the eq......



> I am only expecting myself to EQ to +/- 5dB variation


yeah, around there is good enough.

brucek


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## Jerm357 (May 23, 2006)

I dont know if this has been discussed yet but have you played with speaker phase yet? It made a big difference for me at the crossover point and also lowered the peaks. I dont know what kind of sub setup you have but this is RL-P/ Pro amp combo with no phase ajustment, but by just switching the polarity you can achieve a 0/180degree phase change. Heres a graph of the difference it made. This is with an 80hz crossover.


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## Jerm357 (May 23, 2006)

And after the phase change I turned that to this with 3 filters


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## MakeFlat (Mar 30, 2007)

*More to thank*

Hi,

I would like to thank John for the Java based REW software. Thank you John for all the great work. Using REW, I recently discovered the 50Hz peak that I missed when I used only a Radio Shack SPL meter and test tones on CD.


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## MakeFlat (Mar 30, 2007)

brucek said:


> ...Not too many of us will ever disagree on the fact that peaks below the crossover frequency should be reduced.


I agree.




> I definitely think you should try levels, treatment, positioning, delay and phase with REW first and then think about the eq......
> 
> brucek


I agree.


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## clubfoot (Apr 12, 2007)

My first post here, so go easy on this REW newbie. 
Previously when I setup my system using a compensated RS CD and RS meter, I always set my levels at 1KHz @75db, set my mains for as flat a response as I could with speaker positioning in large w/o sub, then did the sub by itself, then speakers set to small with sub (all in stereo). I have always gotten great sound from following this process. The reason I always did it this way was to avoid the same result MakeFlat is experiencing, i.e. a response that was not as flat from low bass to high end. My point is, it is no good having the flatest bass response if it does not blend smoothly with the rest of the response past 200Hz with the main speakers also as flat as possible,.......it will not sound "right"!

What procedure are you guys using for "overall" flat system response tuning?


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## MakeFlat (Mar 30, 2007)

> What procedure are you guys using for "overall" flat system response tuning?


The scope of discussion below is subwoofer equalization. Thus, while midrange and hf equalization could be a valid approach to get "overall" flat response, it is outside the scope of this discussion.

After possible/practical room treatments have been considered and completed, proceed to do EQ. 

1. Do subwoofer sweeps to find the best location for the sub. Make a note of the next best location.
2. EQ the sub based on the result of subwoofer sweeps.
3. Using subwoofer sweep signal, do subwoofer+mains sweeps to see the effect of the mains on the overall response. Adjust subwoofer level on the sub for a flat FR (it it assumed that the receiver's sub level is already optimized for the BFD.) 
4. Using subwoofer sweep signal, do REW sweeps on the mains. 
5. Compare the results of Step 3 and 4. Check if the mains contribute to peaks.
6. If the mains contribute to peaks, try each of the steps below to see if one can get rid of peaks that are attributable to the mains.
7. Tweak the phase knob/switch to get the best REW runs. Check the region near the crossover, say one octave above and below the crossover.
8. Increase the sub's distance setting on the receiver to get the best REW runs.This assumes that you previously set the exact distances (sub and mains) in the receiver, based on measuring tape.
9. Check for overall flatness. If you are not happy with the result, continue with Step 10.
10. Reposition the mains to see if improvements can be made. If not, go to Step 11.
11. Reposition the sub at the next best location and start all over if the results are not satisfactory.


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## clubfoot (Apr 12, 2007)

OK, did all that, except for the lengthening the distance of the sub, because it made the FR look worst.
I'll post my sub plot later to see what you guys think.


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## Guest (May 2, 2007)

Hi Guys, its been a while since I posted, I was one of the first people to buy the BFD 1124 with the 1.3 version of the software that wouldn't do the midi tranfer. I have since then bought the new chip with the 1.4 software and have a perfectly functioning BFD 1124 thanks to all your help. Thank You very much.

I love the BFD so much that I have just purchased another one for my bedroom system and one for a friend, these are new units and the question I have is, do the newest versions of the BFD 1124 already come with the new 1.4 software on the chip or will I have to order new chips for these units? Did Berhinger actually change the software on any units that were shipped since the original 1.3 version is the question?

If anyone can let me know if they have purchased a BFD 1124 recently that came with the updated software or will I have to go ahead and buy a couple of reflashed chips now?

Just thought I would get the chips ordered so that they would arrive when the BFD's do.

Thanks again for all the help on this forum. I lived with a Paradigm Servo 15 for years always being unhappy with the sound due to a couple of bad resonant peaks in the critical 50 to 70 hz area and this forum has changed my life.

Its so nice to find a great bunch of equally fanatical audiophiles that realise how important good bass is.

Josh


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## MakeFlat (Mar 30, 2007)

Well, I bought my BFD a couple of years ago and it came with V1.0 firmware. I am accustomed to manually entering the filters and I can do it very quickly without errors. Perhaps someone with a recent experience can provide the info.


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## Guest (May 2, 2007)

Thanks Nick,

my mistake, it was a general question, not directed specifically at you

Josh


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## Guest (May 4, 2007)

Just received two BFD 1124's and they have the 1.3 software on them.

Have ordered chips from Hobbyroms

For Your Info

Josh


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