# In Need of Some Help



## ske (Mar 3, 2013)

I've been chasing my tail trying to make adjustments, and could use a hand.
At the moment my subwoofer adjustment options are one collective distance, or adjusting phase. I believe the left sub is the culprit here. I have been making changes, and really getting nowhere. *****Then we installed carpet in a bedroom close by, and alot changed.**** So instead of flailing for a week, I thought I'd post today's findings. These are with a calibrated ECM800 & Tascam US-122MKII. Please let me know if more info is needed...
Thanks!

****UPDATE****
Took new measurements, and got better results. The ones I took before must have been a fluke.
I will post the currrent set when I get a chance.


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## Phillips (Aug 12, 2011)

More info

Subs going to be run mono or stereo?

Subs location?

Subs make?

Have you shifted the subs around?

Post a Waterfall graph if you can?


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## hjones4841 (Jan 21, 2009)

I don't see how the carpet in another room would make any difference - it offers some absorption in the upper freq range, but little or nothing in bass. Did you maybe have the mic in a different position when you ran the sweep after the carpet was installed? Due to room modes, even a small relocation of the mic can make a difference in measured response.


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## Phillips (Aug 12, 2011)

hjones4841 said:


> I don't see how the carpet in another room would make any difference - it offers some absorption in the upper freq range, but little or nothing in bass. Did you maybe have the mic in a different position when you ran the sweep after the carpet was installed? Due to room modes, even a small relocation of the mic can make a difference in measured response.


Exactly

Specially when it is in another room.

We think we have the mic in the exact position but chances of that, very slim.


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## jtalden (Mar 12, 2009)

Your 2 subs are opposite polarities. 
Check your switches for polarity or other places where polarity can be reversed.

The SW1 + SW2 will measure about +6 dB above the individuals when all is correct.


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## ske (Mar 3, 2013)

Oops, I meant to include the equipment. I haven't looked into how to create a signature just yet.

I will definitely take another measurement before making any changes. If it's a fluke, it's pretty drastic.

I've included waterfalls as well.

Emotiva XPA-2 (Main)
Emotiva XPA-3 (Center, Rear)
Emotiva UPA-2 (House)
Emotiva ERC-2
Yamaha RX-A820
Magnepan 1.7 (Main)
Klipsh RC-35 (Center)
Klipsch SS.5 (Rear)
Power Sound Audio XS30 (Front L&R)
Klipsch SW-8(Rear)
Panasonic TC-P60UT50
Panasonic DMP-BD85


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## hjones4841 (Jan 21, 2009)

A moderator can delete posts. I just did for the one you requested.


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## jtalden (Mar 12, 2009)

I see now that that the SWs are indeed in the correct polarity. I misread the colors as they are almost identical on my monitor. Also the way the you unwrapped the phase confused me. Sorry for misleading you.
In the last chart the levels for the SWs are improved and the polarity is correct on both. If you post the .mdat of the 2 SW individually and together. We may be able to see if any improvement is possible with either timing or phase.

It may be easier for you to just use the RTA feature of REW to fine tune the phase adjustment until you get the smoothest response for the 2 SWs.


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## ske (Mar 3, 2013)

Can you please explain further how to see they are in phase? Does the "both subs" line down the middle indicate this?


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## morca (Aug 26, 2011)

I alway,s like to see some picture,s of the room.

to see because how a sub in a room sounds depends on:
1 the space, the size and shape of the space

2 what is in the state space (furniture, etc., but also eg bass traps: google: ie acoustic measures)

3 the position in space of the sub relative to the listening position.


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## morca (Aug 26, 2011)

Sorry double post,something went wrong i think.


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## ske (Mar 3, 2013)

hjones4841 said:


> A moderator can delete posts. I just did for the one you requested.


Thanks!


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## ske (Mar 3, 2013)

I will definitely post photos. But it will have to wait until the weekend.


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## jtalden (Mar 12, 2009)

ske said:


> Can you please explain further how to see they are in phase? Does the "both subs" line down the middle indicate this?


I indicated they are the same Polarity, not that they are in Phase. These are 2 different things. In any setup having the same polarity between SWs is important. Positive polarity is when the initial IR rise is in the positive direction. You did not show the 2 IRs in your post so that easy method was not available.

The fact that the 2 SW phase traces were separated by an integer multiple of 360° In the low bass range (before the first room mode, 9-40 Hz in this case) is the reason that I indicated they are the same polarity. Had one SW been reversed from the other then it would have been offset 180° from one of those increments. 

This would have been less confusing if the phase was still wrapped and thus a 180° offset would have been more obvious.

I did mentioned Phase, but it would have been more accurate to refer to Delay/Timing /Distance as the next important concern. This impacts the phase relationships at each frequency, but it is the relative Delay between the SWs that is actually adjusted.

To determine the current relative delay between your 2 SWs it is necessary to use the REW loopback feature for the measurements. These would be best measurements to start with.

Working without that, I could still use a measurement of each SW measured separately and then together and manually change the relative delay by shifting the IR locations. They can them be added together using "A+B" to see the resulting response. This is what I was referring to when I offered to look into the "phase" relationship. It is very complicated to fully explain and requires practice/experience to fully understand. The only outcome would be to compare your current measured SPL response to the best calculated response and see if there is a significantly better delay setting possible between the SWs. To actually implement it would require being able to change the delay between the SWs using a MiniDSP, Behringer unit, or similar. If your SWs are very dissimilar in distance from the LP then often this capability is helpful. 

Without changing the relative delay you can still use the SW Phase controls to see if that helps the SPL output in the XO range; both between the SWs and then again with each main speakers. No doubt a compromise setting would be needed as each speaker will be different. I have no actual experience setting up a system using SW phase controls, but I have a working understanding of the impact. Specific advice is best offered by others.


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## ske (Mar 3, 2013)

I've attached the .mdat, which includes subs together, apart, and with a speaker, and a speaker by itself.

I have no problem getting a minidsp, or whatever else I need to dial the system in. I really want to learn how all of this works.

Thanks for the help


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## jtalden (Mar 12, 2009)

Thanks for the data. I will be able to work with it. The loopback worked well.

> The Left Sub and Right Sub appear to be equidistant from LP. Is that correct? [The delay between the 2 is correct. No delay adjustment between the 2 subs will be needed.] 
> Are they placed front and rear and if so, which is which?
> Volume Level of the 2 individual subs is very different and the "Subs" level is not the expected level, so that leads me to believe that you changed the levels during the measurements. Is that correct? [It will be no problem for this analysis. I will just use "Subs" measurement for the analysis as that is what was used for your measurements with the "Left Spk/Subs" and "Right Spk/Subs"]

Please answer these questions to confirm I am understanding correctly. I will continue on with the analysis and provide some feedback later today.


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## jtalden (Mar 12, 2009)

I reviewed the measurements regarding the "Left Spk" and "Subs" and those 2 combined.

My guessed is that this setup was the result of the auto setup routine (YPAO) in the AVR. I did not find any detail of the EQ portion of the YAPO routine or its handling of dual subs from my quick look for info on the web. Your AVR has 2 sub outputs however so it is possible that it adjusts the delay between the them.

My Findings:
> The SW polarities are the same as shown in the IR traces below.
> The SW delays appears to be very accurate as shown by close overlap of the 2 SW IR traces below. [Possibly your SWs are equidistant from the LP or the Yamaha YAPO system adjusted the delays appropriately.] 








> The delay between "Left Spk" and "Subs" is very conventional in that the initial rise of the IR is at about the same timing as shown below: 








> The phase alignment is also very good as shown by the strong SPL reinforcement through the XO range and shown below:








Overall Comments:
> There is no significant improvement to be made in the "SW-SW" delay, or the "Subs-Left Spk" delay.
> The Right channel timing is slightly different, but not significantly so. The difference may be the result of mic positions between measurements, or the limits in precision of the delay/distance settings in the AVR. No adjustment will be significantly better.


EQ Comments:
> I am a little surprise with the EQ in the low bass. There is a significant rise in SPL below 40 Hz. [This is not necessarily a concern as you may have enough capacity there with your 2 subs to avoid any overload situation when these frequencies are present in the program. This will not impact much music as there as limited content there. It may be more apparent in action movie sound effects. If you listen at high levels this may overload the Subs when those frequencies are present.] 
> I see YAPO offers a multi mic position setup and recommend that this be used. [A single mic position does not correlate as well to the perceived sound quality even if only the main LP is a consideration. Possibly you have already selected that option.] 

This looks like a very good setup as is. Is there a particular concern?


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## ske (Mar 3, 2013)

First, thanks so much for digging into the data!
The Yamaha has two SW outputs, with one collective delay. I have difficulty setting the level on the left subwoofer. The sub requires less gain to achieve the same SPL's on a Radio Shack Meter, using the Avia disk. I will try using the REW meter and the Behringer mic next time.
The SW are both about 11 feet from the center listening postion.
I've tried multiple postions with YPAO, and it sounds terrible.
In regards to the large bass hump, I may pick up a BFD1000 to even that out. Ears are sore after movies!
My concern is with the dip at about 50hz when both subs play at once. And the dips when the subs are played with the right speaker, especially at about 72hz. Perhaps it's not an issue? I wouldn't know from lack of experience with this.


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## jtalden (Mar 12, 2009)

ske said:


> First, thanks so much for digging into the data!
> The Yamaha has two SW outputs, with one collective delay. I have difficulty setting the level on the left subwoofer. The sub requires less gain to achieve the same SPL's on a Radio Shack Meter, using the Avia disk. I will try using the REW meter and the Behringer mic next time.


I find it easiest to adjust the 2 SW levels so that the SPL traces overlay one another. I just use sweep measurements, but the REW RTA could be used also. When the 2 levels match well then use the AVR level control to adjust both together to match the mains. An SLM does not give visibility to which frequencies are contributing to the level reading. 



> The SW are both about 11 feet from the center listening postion.


That is working well. The timing of 2 SWs is very good.



> I've tried multiple postions with YPAO, and it sounds terrible.


That's too bad, I am not sure why that should be, but of course, use whatever sounds best to you. 



> In regards to the large bass hump, I may pick up a BFD1000 to even that out. Ears are sore after movies!


A BFD should be able to address that hump and also allow some additional smoothing. I have no personal experience with that unit however.



> My concern is with the dip at about 50hz when both subs play at once. And the dips when the subs are played with the right speaker, especially at about 72hz. Perhaps it's not an issue? I wouldn't know from lack of experience with this


50 Hz and 72 Hz deep dips are room modes and it is better to not try to remove them with EQ. They will not sound nearly as bad as they look. I would normally suggest trying differ SW locations, but you have already done that.


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## ske (Mar 3, 2013)

Thanks. Just for kicks, would making phase ajdustments affect those dips? It looks like I could afford to lose a little in the crossover range?
Also, I am having trouble understanding how to interpret the IR. Such as the graph you created a couple posts ago. Could you please explain what I'm looking for to determine the timing differences between the speaker and subs?


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## jtalden (Mar 12, 2009)

I believe the SW phase control will only significantly impact the SW-Main XO range. Possibly the 70 Hz and 116 Hz dip would see a very minor impact. Since your timing/phase is very good through the XO range already, I would expect this adjustment to only make that range worse for overall SPL. No reason not to try it though. Maybe my expectation will be wrong. I think it may have the best chance of working if the 2 phase controls are not adjusted the same, i.e., leave one at 0° and change the other to 90°. Let us know if you have any success. Again, I have never actually played with one of these controls on a SW. I would expect the sound to be better with very narrow dip no matter the depth, so a trade off to a dip that is broader, but still drops 5 dB will probably not help the overall sound.

The IR timing is easy. With loopback on, the actual time for the signal to arrive is shown on the IR chart. If the 2 SW IRs traces land on top of each other then the timing/delay/distance is the same. 

Possibly what isn't clear is that I offset all your measurements by 30.793 ms. I did not use the "Estimate IR Delay" button as that automated function will result in different offsets for each measurement so the relative timing would have been be lost. I didn't need to offset them to see if the timing is correct. I did it so I could look at the other charts like phase and GD. All the charts except SPL need to have there IR near 0 ms for proper interpretation. That is why REW automatically offsets the IRs to near 0 ms when loopback is not turned on.

The timing for SW to main speaker is best adjusted as explained above; align the initial rise of the IRs and then change the delays/distance to maximize the SPL in the XO range. The phase is aligned when the SPL is maximized.


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## ske (Mar 3, 2013)

I am playing with the phase on the right sub now, and will report back soon...

I do understand how to see the subs compare in the IR graph now, but is there a way/need to see how the subs align with the main speaker?


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## ske (Mar 3, 2013)

Phase adjustment was a total bust, you called that one right for sure.


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## jtalden (Mar 12, 2009)

ske said:


> ...
> 
> I do understand how to see the subs compare in the IR graph now, but is there a way/need to see how the subs align with the main speaker?


YPAO aligned them well.
If we were to instead align the SWs to the mains manually we could:
> Set all the speaker distances in the AVR by the tape measured distances.
> Activate the SWs and the FL (or FR) main
> Turn on the REW RTA with: RTA 1/48 mode, rectangular window, using a "Pink PN" signal. 
> Adjust the SWs distance in the AVR to maximize the SPL output in the XO range. 
We should find a good setting within ±2'. If not, reverse the polarity of both SWs and try again.

Instead of setting the initial SWs distance by tape measure we could have adjusted the initial AVR distance setting for the SWs until the initial rise/fall of the SWs IR lines up with the initial rise/fall of the FL IR. [In this case we must use sweep measurements with loopback turned on.] It is still necessary to then adjust the SWs distance using the RTA method above.

I was just confirming if your current setup could be significantly improved. To do that I first looked to see if the 2 IRs were aligned properly. I then virtually moved the "SWs distance" by moving the SWs IR position relative to the FL and then calculated the impact of that change using the A + B function. There is no need to do this if you are on site and have control of the settings. You can just use a tape measure and the RTA process above to see the impact real time.

When using an automated process like YPAO the EQ is probably set dependent upon the timing/distances that were selected automatically. If those are then changed manually the EQs in the XO range may no longer be ideal. When using an auto setup that includes EQ as well and distances, my thought would be to leave the distances as set. If another device is being used for EQ as well, apply those filters on top of the automated ones to adjust the house curve as needed, or possibly to address a problem with the automated setup as the large boost you measured below 40 Hz.


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## ske (Mar 3, 2013)

Thanks. I was considering the MiniDSP if the timing really looked off. But the BFD has more filters, and selectable presets, so that looks likea good way to go.


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