# REW Set Distance For Main Speakers



## Phillips (Aug 12, 2011)

Hi 

What is the best tool to use for setting distance for main speakers.

Also the process please.

If i EQ, does the distance setting change?


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## EarlK (Jan 1, 2010)

Not exactly what you asked for ( but what I think is far more interesting ) is how to align subs to the mains .

Here's an oldy ( but great thread ) on the topic of aligning subs to the mains ( some pretty heavy reading mind-you / bookmark it for future reference when the concepts are a little easier to grasp ) .

 *sub alignment ( a case study )* 


:sn:


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## Phillips (Aug 12, 2011)

EarlK said:


> Not exactly what you asked for ( but what I think is far more interesting ) is how to align subs to the mains .
> 
> Here's an oldy ( but great thread ) on the topic of aligning subs to the mains ( some pretty heavy reading mind-you / bookmark it for future reference when the concepts are a little esier to grasp ) .
> 
> ...


Thank you, i will read this. I would say it will help but using two different frequency speakers could be different?

I am after Distance Align the two main speakers, i have heard by looking at the impulse response but i don't know what to look for?


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## jtalden (Mar 12, 2009)

Phillips said:


> Hi
> 
> What is the best tool to use for setting distance for main speakers.
> 
> ...


I only have experience with my own audio setup, but have done lots of experimentation on this subject. There are several ways to fine tune the XO handoff to a high level of accuracy and they run from moderately difficult to very difficult.

I have most confidence using a careful analysis of the phase through the XO frequency but there is an easier way that should provide very accurate results for those with less experience. It still requires more measurements and time than most would be willing to spend and more than novice level of experience with REW.

The overview of the method could be stated as:

> Set the REW loopback measurement mode on.
> Set AVR XO to desired settings.
> Set the rough distances in the AVR [Using either the automated method provided by the AVR or by tape measurements]
> Measure the SW. [There would be some preliminary steps for multiple SWs]
> Measure the FL main speaker 
> View the IRs to confirm that the polarity and location of the two IRs are in the proper relationship.[ Adjust the FL distance if necessary and remeasure.]
> Measure the SW and the FL together and overlay the 3 SPL responses and using 1/3 smoothing confirm that there is the “proper SPL fill” in the overlap range.
> Adjust FL distance if needed and repeat until the desired result is achieved.
> The phase can also be checked at this point to just to reinforce the result.
> Proceed by using the same process for the FR main speaker and so on for the other main speakers.

This fine tuning of the adjustment is probably not needed for the casual setup as most auto setup methods probably provide reasonable results without this effort. Even hand measured distances may be adequate for good results for the SW to main speaker XO. Distance errors of a couple of feet are probably not significant to the sonic results. This method is more for the hobbyist interested in a learning experience. [It becomes much more critical when using electronic XOs for the higher frequency XOs as from MR to TW however.]

If this method is something that you are interested in trying, I can provide more detail and can review your measurement results as you work through the process.


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## jtalden (Mar 12, 2009)

Phillips said:


> Hi
> 
> If i EQ, does the distance setting change?


No.

If you change the distance however, then the EQ may well need to be adjusted for best results.


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## Phillips (Aug 12, 2011)

jtalden said:


> I only have experience with my own audio setup, but have done lots of experimentation on this subject. There are several ways to fine tune the XO handoff to a high level of accuracy and they run from moderately difficult to very difficult.
> 
> I have most confidence using a careful analysis of the phase through the XO frequency but there is an easier way that should provide very accurate results for those with less experience. It still requires more measurements and time than most would be willing to spend and more than novice level of experience with REW.
> 
> ...


Thank you.

Keeping in mind i can't do a loopback measurement for the soundcard, because i use a USB mic (Omnimic) with the laptops soundcard. The laptop only has a Mic in, not line input.

Would this method apply to the main speakers not worrred about the sub at this stage?

I took some measurements with different distance settings and the response changes significantly even from 3.45 to 3.50 meters.

I can hear the difference as i move upwards away from the receivers setting. The sound tends to get wider, but looses the imaging. With the receivers setting the voices come from the center or between the mains and center. 

The receiver has .50 meter setting, so not terribly fine, so to fine tune i could move the speaker.

I am not to familiar with the IR phase side, so if you send a 101 for dummies version that would be appreciated.

Thanks again


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## Phillips (Aug 12, 2011)

jtalden said:


> No.
> 
> If you change the distance however, then the EQ may well need to be adjusted for best results.


Thank you

I wondered that because distance adjusts a fair bit.

Would i start the EQ again or fine tune?

Thanks again


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## jtalden (Mar 12, 2009)

Phillips said:


> Thank you.
> 
> Keeping in mind i can't do a loopback measurement for the soundcard, because i use a USB mic (Omnimic) with the laptops soundcard. The laptop only has a Mic in, not line input.


Understood. I offered to help walk through the process above including the IR alignment as it sounded like that was the process you were looking for and wanted to do. It doesn’t appear to fit well with your situation and that is fine. 

As I mentioned, it is not necessary to do it that way for good results. It is more just to gain understanding in this area and provide a higher level of comfort in the final setup. [Maybe someone else will want to do this on their system.] 

In your case you could just skip the IR portion and just confirm reasonable distance settings.

Confirmation Method:
> Set AVR XO to desired settings.
> Set the distances in the AVR [Using either the automated method provided by the AVR or by tape measurements]
> Measurement sweep of the SW by itself. 
> Measurement sweep of the FL main speaker by itself.
> Measurement sweep of the SW+FL together 
> Overlay the 3 SPL responses (1/3 smoothing) and confirm that there is the "proper SPL fill” in the overlap range.
> Adjust FL distance if needed and repeat until the desired result is achieved.
> Proceed by using the same process for the FR main speaker and so on for the other main speakers.



> Would this method apply to the main speakers not worrred about the sub at this stage?]


Yes, that is what it is for. The distance setting is the relative setting between the SW and each main speaker. If we adjust the distance of the SW to fit well with the FL speaker Then we cannot move the SW distance setting again to fit the CC without losing the correct setting for the FL speaker. This means the main speaker distances need to be adjusted relative to a SW distance that remains unchanged.



> I took some measurements with different distance settings and the response changes significantly even from 3.45 to 3.50 meters.
> 
> I can hear the difference as i move upwards away from the receivers setting. The sound tends to get wider, but looses the imaging. With the receivers setting the voices come from the center or between the mains and center.
> 
> The receiver has .50 meter setting, so not terribly fine, so to fine tune i could move the speaker.


Steps of 0.5 m are just adequate for the main to SW handoff as the maximum error would be 0.25 m and that's okay. I’m a little confused however with the 0.05 m distance change being easily audible. This is too small to cause to a significant impact on LF SPL in my experience. Since you moved the SW it also changed the room response slightly. I’m still skeptical that 0.05 m would be significant however. I have not experimented with such small SW distance changes however. The issue for me would be, let’s see the measurements. The data tells to story objectively. If there are significant SPL changes with small changes in SW location I would just settle on one that is a reasonable starting point for EQ and leave it there. 

Just as an aside, you may want to experiment a little with the impact of small changes in mic location to get a feel as to how that impacts the SPL result as well. Just measure at several mic locations around the LP (3 to 6 locations is good). Then look at the overlay of the results. The larger the distance between locations the larger the variability. 



> I am not to familiar with the IR phase side, so if you send a 101 for dummies version that would be appreciated.


In the context here (speaker distance settings), The IR can be helpful to affirm that the initial distance setting is a reasonable starting point for the fine tuning of the distance settings. The simplified “Confirmation Method” mentioned above is "flawed" only in that the apparent proper “SPL fill” can be achieved at several different distance settings. [Basically 1/2 XO wavelength increments so a 100 Hz XO has phase alignment and apparent proper SPL fill at roughly 1.7 m increments. When the SW to main speaker IR’s are aligned at the leading edges, then the distance settings are very close to the ideal distance that will provide optimized results throughout the XO range. 

That is:
> The phase response of the SW and mains tracks closely throughout the XO range.
> The SPL will be maximized throughout this range, i.e., the setup will have maximum headroom available in this range. 
> The SW and mains will not be working against each other at some frequencies. 
> The GD will be properly minimized while providing a smooth transition. 

This would all be easier to see and understand with a case study hence my initial offer. But again, it is a mostly a learning experience as acceptable results are usually achieved with conventional setup procedures. I would still suggest that an REW user interested in assuring that the distance settings are indeed reasonable use the “Confirmation Method” above. It's reasonably easy to do and it is not impossible for an automated setup system to make a mistake.


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## jtalden (Mar 12, 2009)

Phillips said:


> Thank you
> 
> I wondered that because distance adjusts a fair bit.
> 
> ...


> The distances and room treatments are set
> The system is then EQ'ed. 

That is the normal condition. If a small distance change, room change, speaker change or other, impacts the setup and a measurement suggests the EQ can be improved it doesn't really matter if it is entirely redone using the automated REW EQ filter matching feature or if it is done manually, either in whole or in part. The subsequent measurements will indicate the efficacy of the adjustments. If major manual changes are done it is advisable to have at least a vague understanding of best EQ practices.


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## Phillips (Aug 12, 2011)

jtalden said:


> Understood. I offered to help walk through the process above including the IR alignment as it sounded like that was the process you were looking for and wanted to do. It doesn’t appear to fit well with your situation and that is fine.
> 
> As I mentioned, it is not necessary to do it that way for good results. It is more just to gain understanding in this area and provide a higher level of comfort in the final setup. [Maybe someone else will want to do this on their system.]
> 
> ...



Thank you very much.

Can i do the IR alignment with my setup?

Sorry i haven't really worded it very well about my setup.

The sub is only used for the LFE. 2 channel music is only played through the main speakers and these are the speakers i am trying to align (left and right mains only). I am trying to fine tune what the Yamaha Z9 has set. Would the process still be the same?

Thanks again


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## Phillips (Aug 12, 2011)

jtalden said:


> Understood. I offered to help walk through the process above including the IR alignment as it sounded like that was the process you were looking for and wanted to do. It doesn’t appear to fit well with your situation and that is fine.
> 
> As I mentioned, it is not necessary to do it that way for good results. It is more just to gain understanding in this area and provide a higher level of comfort in the final setup. [Maybe someone else will want to do this on their system.]
> 
> ...



Thank you very much.

Can i do the IR alignment with my setup?

Sorry i haven't really worded it very well about my setup.

The sub is only used for the LFE. 2 channel music is only played through the main speakers and these are the speakers i am trying to align (left and right mains only). I am trying to fine tune what the Yamaha Z9 has set. Would the process still be the same?

Thanks again


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## jtalden (Mar 12, 2009)

Phillips said:


> Can i do the IR alignment with my setup?


I don't think so because of the USB mic, but I am not an expert in all setup options. I think it's required to use the analog inputs to the sound card to setup the REW loopback. The IR is not helpful without the loopback in place. The loopback/IR is not required to confirm the distance settings using the "Confirmation Method" above.



> The sub is only used for the LFE. 2 channel music is only played through the main speakers and these are the speakers i am trying to align (left and right mains only). I am trying to fine tune what the Yamaha Z9 has set. Would the process still be the same?


??? I am not sure what you are saying here, but...

The "Confirmation Method" just confirms the Z9 distance settings from SW to each main speaker no matter the number of main speakers (1 to xxxx). When distances are properly set there is no need to worry about how many main channels are actually being used or if the SW is being used or not. The distance settings will be correct for all situations.


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## Phillips (Aug 12, 2011)

jtalden said:


> I don't think so because of the USB mic, but I am not an expert in all setup options. I think it's required to use the analog inputs to the sound card to setup the REW loopback. The IR is not helpful without the loopback in place. The loopback/IR is not required to confirm the distance settings using the "Confirmation Method" above.
> 
> 
> 
> ...



Thank you, sorry i haven't got back sooner.

I had a play with the Omni software and was able to fine tune the distance through the IR.
It made a difference between 3.45m and 3.40m. 
Sorry i meant i wasn't fine tuning the sub distance, only the main left vs right speakers


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## jtalden (Mar 12, 2009)

Phillips said:


> Thank you, sorry i haven't got back sooner.
> 
> I had a play with the Omni software and was able to fine tune the distance through the IR.
> It made a difference between 3.45m and 3.40m.
> Sorry i meant i wasn't fine tuning the sub distance, only the main left vs right speakers


Good.
Now your speakers are fine tuned to that exact mic position.

I'm sorry I confused the issue with all the info about SW to Main timing alignment. That's the isssue that can cause problems and the one most of us are concerned about.

Stereo speaker distances can just be set with a tape measure with no concerns. It's hard to get both ears to stay right at the mic position anyway.  

While there is no practical benefit to fine tune like this, when we are taking REW measurements anyway, it is easy to do.


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## Phillips (Aug 12, 2011)

jtalden said:


> Good.
> Now your speakers are fine tuned to that exact mic position.
> 
> I'm sorry I confused the issue with all the info about SW to Main timing alignment. That's the isssue that can cause problems and the one most of us are concerned about.
> ...



Thanks
No worries its good to hear good info.
The change in sound is very audible, even with the slight change.
When i get a chance i will post some frequency graphs with the difference.


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