# Please provide your impressions and advice on my REW graphs



## kjlewie (May 24, 2008)

OK – I’ve spent some time with my Radio Shack SPL meter, Behringer UCA202 external soundcard and REW to generate FR graphs of my subs. The REW online help thread is fantastic. No way could I have gotten everything set up to measure without it. Thanks to all who contributed to the help guide. I did have one question though. I could not find in the guide when I should add the RS SPL calibration file. So, I added it when I began calibrating the meter – seemed logical, but I was uncertain as it wasn’t in the guide. Was this correct?

I have an eD P7S-650 in the front of the room and two Infinity CSW10 in the back of the room. I measured the P7S separately from the CSW10. I measured the CSW10 together since they are basically co located about 3-4’ apart. There are pics of my room in my build thread, but I can post some here if it will help with analysis of the graphs. Now that I have the graphs, I have some questions and would like some impressions from those that are familiar with these graphs.

Here is a graph of the initial measurement of the P7S









Here is the graph of the P7S-650 with REW’s optimize pk gain and q









Here is the graph of the CSW10 with REW’s optimize pk gain and q









1.	What do you think of the FR?

2. These graphs are telling me that I need to add equalization to remove the largest peaks, correct? But, do I need two eqs - one for the P7S and one for the CSW10?

3.	I noticed the FR rolled off and then began to climb in both graphs so I extended the X-axis down to 2Hz. Here is the same graph of the initial P7S measurement down to 2Hz. The graph shows 104dB at 2Hz. What have I done wrong? Has this error compromised all of the measurements and do I need to start over?









4.	I ran the sweeps with all of my speakers connected. Should I have turned off my L,C,R speakers as I could hear bass coming from them during the test. They are crossed at 80Hz.

5.	I ran a measurement with all subs going but didn’t save a jpeg of it. Should I be attempting to measure all subs together or focus on measuring separately for the front and back of the room?

6.	What adjustments/corrections should I make to measure everything correctly?

Thanks for the help.

kjlewie


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

Hi kjlewie,



> 2. These graphs are telling me that I need to add equalization to remove the largest peaks, correct? But, do I need two eqs - one for the P7S and one for the CSW10?
> 
> 5. I ran a measurement with all subs going but didn’t save a jpeg of it. Should I be attempting to measure all subs together or focus on measuring separately for the front and back of the room?


It’s generally easiest to EQ the subs as a whole. So, you’d measure them the same way.




> 3. I noticed the FR rolled off and then began to climb in both graphs so I extended the X-axis down to 2Hz. Here is the same graph of the initial P7S measurement down to 2Hz. The graph shows 104dB at 2Hz. What have I done wrong?


That’s basically noise and should be ignored. There’s not much reason to extend the graph below 10-15 Hz, unless you have a sub that actually has some meaningful output below that point.




> 4. I ran the sweeps with all of my speakers connected. Should I have turned off my L,C,R speakers as I could hear bass coming from them during the test. They are crossed at 80Hz.


If you’re primarily interested in looking at the sub’s response, then turn off the main speakers. Typically the mains are added after the subs are equalized, to see any phase-related affects that might show up.




> 6. What adjustments/corrections should I make to measure everything correctly?


Your measurements look fine. :T


Regards,
Wayne


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## kjlewie (May 24, 2008)

Wayne,

Thanks for the reply - very helpful.

Tonight, I'm going to disconnect the mains and try to measure all subs together.

1. When setting the sub level with the SPL meter, do I attempt to get a 75dB reading with all subs or do I set each sub to 75dB individually? Seems the collective SPL reading would be higher than 75dB if each sub is producing 75dB on its own?

2. What should I expect to see in the 100Hz - 200Hz when measuring without the mains? It should look more or less like the blue line curving down at 200Hz, correct?

Thanks again.

kjlewie


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## glaufman (Nov 25, 2007)

kjlewie said:


> 1. When setting the sub level with the SPL meter, do I attempt to get a 75dB reading with all subs or do I set each sub to 75dB individually? Seems the collective SPL reading would be higher than 75dB if each sub is producing 75dB on its own?


Typically you would set each sub individually to 75dB using the level on each individual sub. When you put them together, the combined reading should then be higher than 75dB. You would then use the master sub-trim on the AVR to bring them all down equally so the combined response is 75dB. That way you achieve 75dB while making sure they're balanced.


> 2. What should I expect to see in the 100Hz - 200Hz when measuring without the mains? It should look more or less like the blue line curving down at 200Hz, correct?


Yes, if you've set a subwoofer target line with an appropriate xover point and rolloff, that's the ideal response from the sub(s).


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## kjlewie (May 24, 2008)

I'm going to do some more tweaking to generate additional graphs to post this weekend.

Greg - I set the subs as you suggested and got 81dB on RS meter before lowering it back to 75dB with the sub trim on my AVR. I was a little uneasy doing it though because I had to turn the volume knob up quite a bit on the Infinity sub to hit 75dB.

The measurements did track the blue line better. Here is the p7s without the mains.









Here are the csw10 without the mains.


















Here is all subs without the mains









Thanks for the help.


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## glaufman (Nov 25, 2007)

I bet that if you move some of them around you can get a flatter response.


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## kjlewie (May 24, 2008)

Last night I added in the mains and measured again.










Its not entirely clear to me why the level is higher than the target level of 75db?

But, the FR is somewhat flat, yes?

Based on feedback I will try to increase the 20hz response by moving the subs around a bit. I'm pretty sure I'll need to stretch out and warm up before tackling the P7S.

I do have a couple of places I can move the subs to try to lift the 20hz FR. Is it really all about trial and error, or are there some likely places the subs may yield better results based on my room (pic below)? In this pic:
Yellow = current position of the 2 CSW 10
Red = current position of the P7S
Green = proposed position of the CSW10 (stacked)
Orange = proposed position of the P7S (stacked)









If I can lift the 20hz response through repositioning and keep everything relatively flat (likely wishful thinking), then perhaps no need for an external EQ? I hope this is the case, but I’m expecting (not sure why) a tradeoff in flatness for the lifting at 20hz.


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## laser188139 (Sep 19, 2009)

kjlewie said:


> ... Its not entirely clear to me why the level is higher than the target level of 75db? ...


What crossover value is set in the receiver? Are the mains configured to small? 

What makes me most curious is the response curves of the subs themselves. The p7s shows a fall off that looks like a crossover at 80Hz. But the curves for the two csw10 speakers don't seem to show the effect of a crossover. Thinks that make one go "Hmmm". 

Bill


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## kjlewie (May 24, 2008)

I will double check my AVR settings but I was pretty sure the crossover was set to 80 for my mains and 120 for my surrounds. And that the mains were set to small. I've been tweaking and adjusting the settings a lot as I played with REW so some of the settings certainly could have been changed.

I'll double check the crossover on the subs as well.


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## glaufman (Nov 25, 2007)

Levels sometimes shift from one measuring session to the next. I make a point of calibrating the SPL every time I start a measuring session.
Also, are you measuring in the front or back row? You should take a look at both, as they'll be different.


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## kjlewie (May 24, 2008)

All measurements have been taken from the front row money seat. Interesting idea to measure from the back row because to my ears, the back row has more a bit more bass.


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## glaufman (Nov 25, 2007)

You'll probably find it's less even as well.


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## Nuance (Nov 2, 2008)

Any updates? I've been following your thread at AVS Forum and was hoping you had posted one here (the guys here are REW/PEQ geniuses). 

Best of luck to you. Do let us know how things go.


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## kjlewie (May 24, 2008)

After toting subs around my room and taking many measurements, its time to post an update. Instead of posting to report significant progress, I feel less certain about everything.

On Monday night, I moved and stacked the P7S to the front right corner (next to the mains) and I moved one of the CSW 10 to the bump out next to the first row of seating while leaving the other one behind the 2nd row.

Here is the FR of the P7S stacked in the front corner









Here is the CSW10 next to the 1st row









Here is the other CSW10 behind the 2nd row









Here are all of the subs in the new positions without the mains









Here are all of the subs in the new positions with the mains









Here is the waterfall









Below 25hz was already lacking and then it dropped off even more. The higher frequencies did not trace the blue line as I’d expected. I began to wonder if I shouldn’t have left the very heavy P7S boxes in place and instead moved the relatively light CSW10 boxes around first. I was too tired and decided I was done for the night.

Tonight, I decided to put the P7S boxes back in position flanking the center channel about 12” from the front wall with the drivers facing the front wall (its easier to reach the controls and all subs are sealed). I left the CSW10 in their new positions next to the 1st row and behind the 2nd row.

Here is a FR graph of the P7S back near its original position









Here is a graph of the P7S and the 1st row sub









Here are both CSW10 without the P7S









Here is a waterfall of all subs with mains









Here is a waterfall of all subs with mains (blue) with just the P7S back to its original position as an overlay (purple)









I’m not sure what to do next, but I’ll try something tomorrow night. I have to be mindful of our desire not to see the subs as I crawl around looking for the sweet spots. I appreciate any thoughts and comments on the attached graphs.


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

Hi kglewie,

What we have here is a classic example of what happens when trying to mix high performance and budget subs. It’s a familiar scenario: “Got these awesome new subs, but I hate to see these old ones just going to waste.”

The problem is that in the end, all that’s accomplished by adding in the inferior subs is that overall performance is “dumbed down” to their level. Looking at your graphs we can see it happening here.

Let’s take a look at the graph of your ED P7S-650's from Post #5, which happens to be the best posted for these subs:










We can see a peak just south of 50 Hz, but note that extension is flat all the way down to 20 Hz. Now let’s look at the best graph for the Infinity CSW10 subs:










As you can see, these subs are “done” at 30 Hz. So – what happens when we combine the two? The results are predictable: We have four subs operating 30 Hz and above, so the total system (all subs operating) has good extension down to only 30 Hz. Below that point response falls, since only two subs are operating below 30 Hz:










If you go back and review all the graphs you've posted, you’ll notice that any time the Infinity subs are added to the EDs, extension starts drooping below 30 Hz. The Infinity subs have "dumbed down" your overall response.

The other issue with mismatched subs is that the “weaker” one will max-out and start distorting, bottom out, etc. before the more capable one does. Well, you can’t push the system any harder than the point where the weaker sub gives up, unless you want to destroy it. Thus, maximum system output (SPL) is also limited by the lesser sub; the more powerful sub never gets a chance to live up to its potential.

My advice: eBay the Infinity subs, and put the EDs back where you had them at Post #5. See if you can adjust the location somewhat to bring down the peak. Often a peak like that can be tamed by moving the sub down the wall a few feet away from the corner. Once you’ve established your best location, equalize if needed.

Regards,
Wayne


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## Nuance (Nov 2, 2008)

Well stated, Wayne; I completely agree with you.


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## glaufman (Nov 25, 2007)

Well done Wayne. Looking at all these I was thinking along similar lines, but couldn't form the words.
Excellent case study.
Of course, the other thing that could be done, albeit with A LOT of work, would be to BP limit each of these subs to handle particular regions...


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## kjlewie (May 24, 2008)

Thanks for the detailed graph analysis and interpretation and also the layman's explanation - really quite helpful. Also, thanks for providing a suggested course of action. I was really stumped on what to try next as far as positioning. I'll measure the P7S in its original position with the mains. I suspect the result will indicate I need to EQ that peak at 49Hz but at least I should have my extension back.

I'll post an update tonight. Hopefully its not overkill and all of the graphs I'm posting will be helpful to others. Posting enough information so that those with experience can offer informed analysis has been quite helpful to me.


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## Nuance (Nov 2, 2008)

It is not overkill. The goal is to help you, so you (we) have to do whatever it takes. I (we) look forward to seeing your new measurements. Good luck!


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## kjlewie (May 24, 2008)

Tonight, as advised, I turned off my Infinity subs and ran a couple of measurements with the P7S back in its original position. First, just the P7S then with the mains added to the mix.

As a reminder, here is the graph of the P7S. I'll have to double check the crossover on the P7S as the 90-100hz range isn't quite like it was in post #5:









Here is the P7S with the mains added in:









The 20hz stuff is back but what is the graph telling us about 55hz and higher?


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## Nuance (Nov 2, 2008)

Looks like the graph is telling you that your subwoofer volume (output) is too low. 

Find the optimum crossover, EQ the peak, add in the mains and adjust the subwoofer output level until you've got a nice transition. You can also (again) try various placement options and see which achieves a better blend.


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## DanTheMan (Oct 12, 2009)

Thanks for this thread! It's been most useful.

Dan


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## fauzigarib (Mar 11, 2010)

This is a wonderful study... Really helpful for me, as this is the project that I'm just going to start, i.e., calibrating my sub.

Thanks for this.

Fauzi


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

> ...with the P7S back in its original position.


Where exactly is that? Up front by the screen? It would be nice if you could tame that peak some before equalizing.

Regards,
Wayne


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## kjlewie (May 24, 2008)

Yes, the original position of the P7S is up front by the screen. Each box of the P7S flanks the center channel speaker. It is the two RED boxes in my room diagram here:









I am game to try moving the subs around a bit more attempting to tame the 49hz peak somewhat. What are some other suggestions for what I could attempt to lessen the peak before deciding on a PEQ?


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

> What are some other suggestions for what I could attempt to lessen the peak before deciding on a PEQ?


Just try some different locations back there, both symmetrical and asymmetrical. A good assymmetrical you might try is one in the center and one in the corner.

Regards,
Wayne


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## kjlewie (May 24, 2008)

I could not find a position for the P7S that reduced the 49hz peak. But, using Wayne's suggestion of asymmetrical positioning, I was able to generate an additional 3dB from about 33hz on down. The 49hz peak is still hitting 84dB, but the 20hz region has improved from 72dB to 75dB without any significant deterioration anywhere else - I'll take it.










While sitting next to the P7S trying to catch my breath after dragging them all around, I decided to reverse the phase from 0 to 180. I was pleasantly surprised with the 10-20hz response at about 75dB. But, the phase adjustment also revealed a dip in response at 25dB that wasn't there before. Oh, and the 49hz peak - it was right were I left it:









Tomorrow I'll put the front soundstage back in place and measure with the mains. I'm thinking the Anti-Mode 8033 will be a welcomed addition to my bag of bass treatment goodies.


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## Nuance (Nov 2, 2008)

kjlewie said:


> While sitting next to the P7S trying to catch my breath after dragging them all around, I decided to reverse the phase from 0 to 180. I was pleasantly surprised with the 10-20hz response at about 75dB.


I wouldn't trust the gain between 10-20Hz; probably just a measurement anomaly. 

The first graph out of the last two you posted looks to be the best (green). Boost the subwoofer output some, EQ that wicked peak, then re-adjust subwoofer levels again to at least match the mains.


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## kjlewie (May 24, 2008)

Yeah - the first graph is the one I'm moving forward with as it appears to only require an EQ to pull down that peak. I'm spinning my wheels a bit on how to increase the subwoofer output some but I do have an ideaonder:. The asymmetrical position seems to have increased the lower end output by a few dBs. I'm curious if this is more the result of the box below the CC or the box in the corner?

When I had both units colocated (stacked) in the corner I do not recall detecting the increase in lower end dBs. So, now I'm thinking of colocating (side by side) the units in the center of the stage, below the CC and measuring once again. Shouldn't be too painful as I've bulked up from my recent execise program. It's called the "Lift, Carry, and Drag Subwoofers" all over the HT.:laugh:


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## glaufman (Nov 25, 2007)

Do you have some dimensions for that room layout?


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

kjlewie said:


> I decided to reverse the phase from 0 to 180. I was pleasantly surprised with the 10-20hz response at about 75dB. But, the phase adjustment also revealed a dip in response at 25dB that wasn't there before.


Don’t know what that is, but phase controls only have an effect when the mains and subs are both on. And then, typically only an octave or so above or below the crossover frequency. Unless you’re saying you reversed the phase on one of the subs?




kjlewie said:


> Yeah - the first graph is the one I'm moving forward with as it appears to only require an EQ to pull down that peak. I'm spinning my wheels a bit on how to increase the subwoofer output some but I do have an idea. onder:


 Are you saying your subs are maxed out? If so, you won’t be able to do any equalizing. Equalizing requires headroom.




> The asymmetrical position seems to have increased the lower end output by a few dBs. I'm curious if this is more the result of the box below the CC or the box in the corner?


If anything, the one in the corner.




> When I had both units colocated (stacked) in the corner I do not recall detecting the increase in lower end dBs.


That was because of the Infinities...




> So, now I'm thinking of colocating (side by side) the units in the center of the stage, below the CC and measuring once again.


Since that 50 Hz peak doesn’t seem to be going anywhere, I’d try co-locating them in a corner. That would get you a 6 dB increase in output, since that seems to be a concern. I hate to see such severe equalization employed (looks like it’s going to require a cut of 15 dB or so), but apparently that’s just the way it is. Just keep in mind that cutting that peak that much, you’re going to have to increase your sub output by about that much to make up for the reduced volume levels. Hope you have enough headroom for that...




> Shouldn't be too painful as I've bulked up from my recent execise program. It's called the "Lift, Carry, and Drag Subwoofers" all over the HT.:laugh:


Don’t you have a dolly? 

Regards,
Wayne


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## Nuance (Nov 2, 2008)

As far as increasing output, I simply meant turn it up on the receiver/preamp. There should be a subwoofer level somewhere. Also, don't forget to find the clip limits of the input signal before EQing. You can read how to do that here (titled SETTING THE INPUT LEVELS ON THE BFD):

http://www.hometheatershack.com/forums/bfdguide/

_Posted via Mobile Device_


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## kjlewie (May 24, 2008)

glaufman - the room dimensions are:

7'10" ceilings with soffit all around
22' in length from front wall (not false wall) to rear wall
13'4" in width at the seating area
11' in width at the stage area
The SPL meter is about 12-13' from the P7S and at ear height for the first row - about 45"
The room is very well sealed when the doors are closed

Wayne - There is only one phase switch for both boxes. And, the mains were not on. The measurement results must be an anomaly as Nuance suggested.

I'm not saying the subs are maxed out - there appears to be plenty of headroom according to REW and the sub volume knob is set at 12 o'clock. Frankly, I'm not 100% certain of what I am saying:blink:. What I was trying to say was in response to Nuance's last post advising to "boost sub output, EQ the peak, and readjust sub volume to match the mains." I may have misinterpreted his response as a further course of action from my last graphs? Perhaps he was just reiterating the overall course of action for subwoofer nirvana?

You are correct about the Infinity subs compromising the first stacked corner measurement. I'll give the stacked corner another shot without them though I'm not particulary concerned about overall output. I was more concerned about 20hz-28hz output relative to the rest of the below 80hz FR. Your comments on the Infinities diluting that range alleviated that concern.

Question for everyone. What do you think about locating the P7S somewhere in the seating area (away from the mains)? Maybe this would positively impact Mt. Everest (the 49hz peak)?

No dolly, but - and don't laugh - do you know those furniture slider coasters? I borrowed both sets of 4 from my wife and placed them under the sub boxes. At first, I'd place the coasters underneath, reposition the boxes and remove the coasters. Now, after nearly a week of moving and tweaking - I just leave the coasters under the sub ready for the next move. Okay, go ahead and laugh.:laugh:


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## kjlewie (May 24, 2008)

Nuance said:


> As far as increasing output, I simply meant turn it up on the receiver/preamp. There should be a subwoofer level somewhere. Also, don't forget to find the clip limits of the input signal before EQing. You can read how to do that here (titled SETTING THE INPUT LEVELS ON THE BFD):
> 
> http://www.hometheatershack.com/forums/bfdguide/
> 
> _Posted via Mobile Device_


Thanks for the clarification. That's is not what I thought you meant. I assumed you were sending me back to the drawing board to figure out a way to lift output.


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## Nuance (Nov 2, 2008)

kjlewie said:


> Question for everyone. What do you think about locating the P7S somewhere in the seating area (away from the mains)? Maybe this would positively impact Mt. Everest (the 49hz peak)?
> :


You can try, so long as your back can handle it.  What you're doing might be a pain (literally), but taking the time to find the ideal location is the right thing to do. Better to find the ideal spot than to just EQ the snot out of the response. 

Good luck.



kjlewie said:


> Thanks for the clarification. That's is not what I thought you meant. I assumed you were sending me back to the drawing board to figure out a way to lift output.


Nope - wouldn't do that to you.


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## glaufman (Nov 25, 2007)

If you're going to play with positioning, put a sub where you'd be sitting, play pink noise, use REW in RTA mode, and move the mic to all the possible sub locations. Put the sub in the area with the response you like the best. 
I would especially try the sub 8'4" and/or 13'8" from the front wall... other possibilities woud be the front wall 4.2' from either corner, or maybe 5' from either corner...
BTW, sorry for the delayed response, was without power since Saturday afternoon...


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## Nuance (Nov 2, 2008)

glaufman,

Is there a calculator floating around that uses room dimensions to calculate room nodes and/or ideal locations for subwoofer placement? I am sure I've seen it somewhere, just don't remember where exactly.


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## laser188139 (Sep 19, 2009)

Gerbrand started a thread which showed some very colorful representations of his modeling with the CARA room acoustics package (not free). I'm not sure a conclusion was reached on how well the model matched reality. 

I found an Excel spreadsheet (free) that did a more primitive version of the modeling. What I found, not surprisingly, is that the model is very sensitive to the assumptions made about the absorption coefficients of the walls. So, unless you have treated the room and you know fairly well how the walls/ceiling/floor behave, you will spend a fair amount of time playing with the coefficients to see what values give results that match what you measure with REW. I was looking at the higher frequencies in the mid bass region; it could be that the results are more stable in the sub range.

Good luck,
Bill


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## Nuance (Nov 2, 2008)

Thank you, laster188139.


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## kjlewie (May 24, 2008)

glaufman said:


> If you're going to play with positioning, put a sub where you'd be sitting, play pink noise, use REW in RTA mode, and move the mic to all the possible sub locations. Put the sub in the area with the response you like the best. I would especially try the sub 8'4" and/or 13'8" from the front wall... *other possibilities woud be the front wall 4.2' from either corner, or maybe 5' from either corner...* BTW, sorry for the delayed response, was without power since Saturday afternoon...


No worries - glad you have power now, I read about the stormy weather in the NE.

The front wall at 4.2' from the corners is actually were I got my best measurement (the first chart in post #5 which Wayne referenced).









The front wall at 5' from the corners would colocate the P7S boxes right next to one another in front of the CC. The response here was nearly as good as the 4.2' response. Both of these yielded my best FR among the many positions at the front of the room. I think this is the correct graph, but I’m not entirely certain.









The 13’8” position coincides with the wider seating area of the room. I have space to position a sub next to the front row there. I have yet to man up enough to move the boxes there. Thought about it a few times, though and may give it a go. I do not have a position 8’4” from the front wall as that would expose the sub in view of the 1st row. Just to clarify – is your suggestion to stack the P7S at 13’8” from the front wall?

BTW, laser188139, the thread and the spreadsheet links are quite interesting - thanks. I couldn’t replicate the REW measurements because (as you predicted) I don’t know enough about how my surfaces behave. Still, its very interesting to “move” the subs around and set the listening position. A freebie like this with the ability to reasonably accurately model irregular rooms would be, well, priceless.


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## kjlewie (May 24, 2008)

To my great surprise, my anti mode 8033 showed up last night:sn:. With the nice weather I didn’t get to play with it until late and by then, of course, it was late. So, I ran the calibration and took a quick measurement without moving the P7S from its less that ideal “front corners” positions. Look at that buzzcut! I think Mt. Everest met its match. What do you think?









When I get home, I'll put the P7S in a few “better” positions and rerun the calibration. But, I really like the effectiveness of the 8033 based on a quickie attempt.


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## kjlewie (May 24, 2008)

Okay, here is the P7S back in the original position that Greg also suggested with the anti mode active. 










I then added in the mains in but really got off track adjusting settings for the mains. I'm not sure what all I did to the mains settings before measuring this graph??:huh: I think I lowered the mains too much.










During a quick demo of the plane crash scene from "Knowing" I liked the sound of the subs quite a bit. I'm still a little surprised that the bass sounds better after removing 2 subs. I know removing the peak makes a big difference as well.

I need to go measure the mains and figure out what I need to do. Any suggestions?


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

> I'm still a little surprised that the bass sounds better after removing 2 subs. I know removing the peak makes a big difference as well.


That’s because response is no longer “dumbed down” to the level of the inadequate subs. 




> I need to go measure the mains and figure out what I need to do. Any suggestions?


Unless you have some means of equalizing the mains, not much you can do with their measurements, except adjust their overall levels in relation to the subs.

Regards,
Wayne


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## kjlewie (May 24, 2008)

Thanks Wayne. I readjusted the overall level of the mains in the AVR. I'm going to listen for awhile to see how things sound overtime. But, as of now, the sound is so much better, more impactful without booming. I'm very pleasantly surprised at the different bass notes of explosions I've heard many times that used to just go boom - time to rewatch some of the library:bigsmile:. This is what I expected the P7S to sound like when I built it.

If I decide to move things around again, I'll give the 13'8" position next to the 1st row a go.

Kind of funny that, after all of that repositioning, the subs ended back near their original position:coocoo:.

Thanks to all who provided advice and feedback to this thread, including those responsible for REW - a very useful tool. Measuring, finding a good spot, EQing the peak and matching the volume with the mains has made a huge improvement in bass quality. Time to research house curves and wider area equalization or just watch movies.


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## Nuance (Nov 2, 2008)

We look forward to your impressions. Things look real nice now, but I'd love to see a measurement from 15-500Hz with 1/3 octave smoothing. It will how well the phase was set and how the subs blend with the mains.

Your hard work has paid off. Enjoy!


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## glaufman (Nov 25, 2007)

For the record, no, I was not suggesting stacking them. But if doing so works, then by all means leave it.


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## kjlewie (May 24, 2008)

Thanks guys. Quick question - what do the Impulse and Spectral Decay tabs show?

As requested here is a FR graph out to 500hz with 1/3 octave smoothing. What does this tell you about how the phase is set and how the subs cross with the mains?









Here is the waterfall of the same measurement. What do the extended 'ripples' near 48hz signify?


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## Nuance (Nov 2, 2008)

Well, you definitely have some issues going on between 100 and 300Hz, either caused by phase or the room. I believe you said the crossover is set at 80Hz, but the crossover is not a brick wall, so phase issues can occur above and below that 80Hz mark. I noticed you said you built your subs, so does the amp you used have variable phase or perhaps a polarity reversal? If so, messing with those settings might achieve a smoother transition between 100 and 300Hz. Otherwise moving the speakers a few inches could help.

Perhaps I should have asked for a measurement to 3000Hz. Sorry.


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## laser188139 (Sep 19, 2009)

kjlewie said:


> ... Here is the waterfall of the same measurement. What do the extended 'ripples' near 48hz signify? ...


The longer duration resonances at 23Hz and 48Hz suggest room modes. These would correspond, roughly, to 1/2 wave distances of 24' and 12' respectively. It can be a little tricky to correlate room modal resonances with room dimensions, but in the simple cases a freq-distance calculator is sufficient. 

Bill


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## kjlewie (May 24, 2008)

The amp has a 0 to 180 phase switch that is only switchable from one to the other. I can also play around the the LF and RF positions by a few inches (I have a pillar that precludes further repositioning of the RF). The pillar is treated with acoustic foam, but could it be having an impact on the FR at 100 and 300hz? Maybe I should run a FR graph from the LF instead of the RF. Here is a FR graph out to 3000hz.









I moved the subs just a bit and ran another waterfall. The 48hz resonance duration in now inline with the overall response, but the 23hz one remains out to about 500ms. Can't seem to locate the pic of that though.


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

kjlewie said:


> Here is the waterfall of the same measurement. What do the extended 'ripples' near 48hz signify?


It's just some kind of low-level noise signal in the room - nothing to worry about.

Regards,
Wayne


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