# Subs and mains Phase



## Phillips (Aug 12, 2011)

Hi am setting up my mains with REL subs.

They will be run as stereo, Left Main with Left Sub, Right Main with Right Sub

I have attached the mdat (zip file) file below, please can someone check the phase for me.

Please correct me if i am wrong.

They are labelled.

The way i see it:

Left B speaker and Left REL should be set to Phase 0
Right B speaker and Right REL should be set to Phase 180

View attachment rel phase.zip


Thanks in advance


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## jtalden (Mar 12, 2009)

The relative SWs polarity is the same as shown in this file. 
The relative mains polarity is the same as shown in this file. 

The polarity of both SWs is opposite of the polarity of both mains. [This is not necessarily "wrong" as a "good" handoff from SW to main is possible either way.] 

If you are using an acoustic LR-24 XO it is "conventional" to use the same polarity for SWs vs mains.
If you are using an acoustic LR-12 XO it is "conventional" to use the opposite polarity for SWs vs mains. 

If the acoustic XO is some other order or does not match a "textbook shape" acoustically then there is no "conventional" answer. 

In summary:
The measured polarities are fine. You could reverse both SWs if you like. A good alignment is possible either way. 

Also:
I would suggest you time align the handoff using a delay/distance control rather than using a variable phase control if you have that option. A variable phase control just adds more phase rotation to compensate for poor setup of the delay/distance control.


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## Phillips (Aug 12, 2011)

> The relative SWs polarity is the same as shown in this file.
> The relative mains polarity is the same as shown in this file.


Thank you

Keeping in mind there are hooked up via Neutrik cable (yellow, red, black cable) high level and will be run as stereo.

Could you post the files please to see where i went wrong.



> The polarity of both SWs is opposite of the polarity of both mains. [This is not necessarily "wrong" as a "good" handoff from SW to main is possible either way.]


Please could you post the file/s to explain.



> If you are using an acoustic LR-24 XO it is "conventional" to use the same polarity for SWs vs mains.
> If you are using an acoustic LR-12 XO it is "conventional" to use the opposite polarity for SWs vs mains.


I will try and find what the XO is in the RELS, they use High Level.



> If the acoustic XO is some other order or does not match a "textbook shape" acoustically then there is no "conventional" answer.


Is there any way i can measure this in REW?



> In summary:
> The measured polarities are fine. You could reverse both SWs if you like. A good alignment is possible either way.


Actually listening there appears to be more bass (not much) with both reversed.



> Also:
> I would suggest you time align the handoff using a delay/distance control rather than using a variable phase control if you have that option. A variable phase control just adds more phase rotation to compensate for poor setup of the delay/distance control.


The only option is the receiver, i hookup via speaker B > high level.

When setting up dual stereo subs does it pay to still do a combined all speakers subs playing to finalize phase / polarity?


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## jtalden (Mar 12, 2009)

Phillips said:


> Keeping in mind there are hooked up via Neutrik cable (yellow, red, black cable) high level and will be run as stereo.
> 
> Could you post the files please to see where i went wrong.


SW IRs








Mains IRs








I didn't find anything "wrong", but I was puzzled as to why one SW is set at a much higher SPL level that the other. I adjusted the level of one down to match the other for this comparison.

Notes:
> The SW IRs are very noisy. I suspect that is just the result of the signal level being down near the mic noise floor. We should be able to just ignore the high freq fuzz on the SW IR traces.
> I manually adjusted SW IR delays to align them in time for these graphs. In this case, the automated SW REW timing alignment in the original file was significantly different.



> Please could you post the file/s to explain.


> The initial SW IR rise is negative and the initial mains IRs rise is positive. This is what indicates opposite polarities for SWs vs Mains. It is not a problem in this case.




> I will try and find what the XO is in the RELS, they use High Level.


Was the XO active for these traces? There appears to be a LPF on the SW but no HPF on the mains, so the overlap is very long. Is this standard and the only option for this type of setup?



> Is there any way i can measure this in REW?


There is no need to do that. It was informational; to explain why the SW vs Main polarity is not always the same. There is only need to establish good handoff timing from SW to mains. That may, or may not, be assisted by reversing the polarity of the SWs.



> Actually listening there appears to be more bass (not much) with both reversed.


When listening to just the SWs?

The only option is the receiver, i hookup via speaker B > high level.

I am not sure what you are implying. I have no actual experience with powered SWs or with speaker level XO setups, so I have no direct experience with what controls might be available. If your SWs are the same distance from the LP and you have a control for time/distance setting in the SW amp (in the SWs) then that is all you need. If you do not have that control then you may need to use a variable phase control if you have one. 



> When setting up dual stereo subs does it pay to still do a combined all speakers subs playing to finalize phase / polarity?


My only experience is with mono SWs. In my case, below of the XO range, there is no SPL difference between measuring FL+SWs and FR+SWs (separately) or measuring FL+FR+SWs (together). In the XO range itself it is very different between FL+SWs and FR+SWs, but when measuring them together it appears to be basically a simple average of the 2. As a result I rarely measure FL+FR+SWs. My experience is limited to my setup however. Per JohnM's recent comment, it may be a good idea for you to confirm the impact on your setup "together" to be sure. I would still think "separately" is the primary setup method however.


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## Phillips (Aug 12, 2011)

> SW IRs
> View attachment 44958


Thank you for your reply

Is there a automatic way to align the impulse, i see that you have shifted them to align.
Why are they not aligned?




> Mains IRs
> View attachment 44959
> 
> 
> I didn't find anything "wrong", but I was puzzled as to why one SW is set at a much higher SPL level that the other. I adjusted the level of one down to match the other for this comparison.


Sorry that was my fault i had been playing with levels and hadn't returned it to the original level.



> Notes:
> > The SW IRs are very noisy. I suspect that is just the result of the signal level being down near the mic noise floor. We should be able to just ignore the high freq fuzz on the SW IR traces.


Is it best for me to measure higher for the subs, my intentions were to measure at the same level as the mains?



> > I manually adjusted SW IR delays to align them in time for these graphs. In this case, the automated SW REW timing alignment in the original file was significantly different.


Please can you elaborate.



> > The initial SW IR rise is negative and the initial mains IRs rise is positive. This is what indicates opposite polarities for SWs vs Mains. It is not a problem in this case.


I found that 180 degrees on both subs gave better results.



> Was the XO active for these traces?


Yes 



> There appears to be a LPF on the SW but no HPF on the mains, so the overlap is very long.
> Is this standard and the only option for this type of setup?


That's right just a LPF for the mains.
REL work in a different way to conventional they use High Level (speaker terminals) and Line (RCA) simultaneously for Hometheatre.
The mains are rolled off naturally and the REL picks up the low end for 2 channel and then when HT they use both High Level and Line for LFE, works really well. 
REL highly recommend corner loading to lock in the room, no boom whats so ever.
They have a setting for SLAM / DEPTH which is used only for the LFE.



> There is no need to do that. It was informational; to explain why the SW vs Main polarity is not always the same. There is only need to establish good handoff timing from SW to mains. That may, or may not, be assisted by reversing the polarity of the SWs.


By reversing both subs it made a little difference.



> When listening to just the SWs?
> 
> The only option is the receiver, i hookup via speaker B > high level.
> 
> I am not sure what you are implying. I have no actual experience with powered SWs or with speaker level XO setups, so I have no direct experience with what controls might be available. If your SWs are the same distance from the LP and you have a control for time/distance setting in the SW amp (in the SWs) then that is all you need. If you do not have that control then you may need to use a variable phase control if you have one.


Because the Subs are hooked to the speaker terminals (High Level) speaker B terminals on the receiver this is automatically adjusted for distance by what the mains are adjusted to because i think speaker A and Speaker B on the receiver are bridged. The subs are very close to the mains.




> My only experience is with mono SWs. In my case, below of the XO range, there is no SPL difference between measuring FL+SWs and FR+SWs (separately) or measuring FL+FR+SWs (together). In the XO range itself it is very different between FL+SWs and FR+SWs, but when measuring them together it appears to be basically a simple average of the 2. As a result I rarely measure FL+FR+SWs. My experience is limited to my setup however. Per JohnM's recent comment, it may be a good idea for you to confirm the impact on your setup "together" to be sure. I would still think "separately" is the primary setup method however.


I always measure all separately then together, take advantage of the time.
I have been playing around with the Antimode Dual Core with different profiles (it has 4).
I have been EQing with stereo filters instead of separate.
I noticed when i used separate filters i lost the imaging and sound stage it sounded muddled.
I have gone from 6 filters for each main to 2 stereo filters for both mains and it sounds alot better.

Thanks again


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## jtalden (Mar 12, 2009)

Phillips said:


> Thank you for your reply
> 
> Is there a automatic way to align the impulse, i see that you have shifted them to align.
> Why are they not aligned?


Yes, that is the purpose of the REW loopback feature. I don't think it is possible with a USB mic however. 



> Is it best for me to measure higher for the subs, my intentions were to measure at the same level as the mains?


You have good intentions.



> Please can you elaborate.


Sure, but what should I focus on? You need to express what you don't understand so I don't waste time telling you what you already know. This manual shift of the IR position has been discussed here many times since you have been following the forum. You have seen all the needed info several times. If you are confused you need to be specific on the aspect of it you don't understand. It may also be covered in the REW "Help". It is part of the control box on the Impulse tab. Maybe you just don't understand why I shifted it? I can't help you, if you can't help me.



> Yes


Okay, your final intended XO was active. You have no ability to adjust the relative delays. Your speakers are about same distance from the mains. 

My analysis indicates there "can" be very good phase tracking through the entire extended XO range with the settings you have now. The only issue is if the delay between the SWs and mains is already good. Since the subs are about the same distance as the mains good timing is much more likely. If the SPL is not good then your only recourse is the variable phase control to try to improve the SPL.

The way we investigate to determine if the timing is good in detail is the similar to that done in other threads. 
[First see below; there is no need to do additional measurements if the SPL is already acceptable in the XO range. You haven't provided that information yet.]

Measure:
FL
SWl
FL+SWl

FR
SWr
FR+SWr

Overlay FL, SWl, and FL+SWl to see how much XO range SPL support there is.

Do the same for the Right Channel.

If needed, adjust the variable phase control to try to improve the support.

_____________

Thinking about this more; maybe you are missing the biggest picture.
For a given room setup condition:

1- If the XO range SPL is already reasonably near the target then all is well - done. 

2- If the XO range SPL only varies a little and can be brought to acceptable level with moderate EQ then make that EQ adjustment - done.

3- If there is a big dip in the XO range and reversing the polarity of the SWs removes the dip and places it in category 1 or 2 then make the change - done.

4- If the XO range is very lumpy or has a large dip that is not easy to remove with moderate EQ and/or a SW polarity change, then there may be a timing error that can be investigated more fully with REW to understand why. [In this case, Since no timing changes can be made, then there is nothing that can be done about it (except maybe the variable phase control).] 

Some dips in the XO range may be the result of room modes that may not be correctable even if we have all the proper controls to adjust.

Maybe you are at 1, 2 or 3 and for some reason fooling around with 4?

Some of us fool around with 4 just to better understand the details of the alignment and assure that it is adjusted as closely as possible to a "conventional setting" before EQ is applied. A reasonable SPL response is still the only practical objective however. It really doesn't matter if we first fine tune delay settings to a "conventional setting". I consider a "conventional" timing alignment to be one that has the closest phase tracking of the SW vs main through the entire XO range.

I hope this helps, but I have the feeling that I keep telling you things that you already know. If you have additional questions please try to be more specific in your questions. It will ease my mind and save me time. Thanks!


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## Phillips (Aug 12, 2011)

Thanks again



> Yes, that is the purpose of the REW loopback feature. I don't think it is possible with a USB mic however.


No i don't think they can to either.



> > I manually adjusted SW IR delays to align them in time for these graphs. In this case, the automated SW REW timing alignment in the original file was significantly different.
> 
> Please can you elaborate.
> 
> Sure, but what should I focus on? You need to express what you don't understand so I don't waste time telling you what you already know. This manual shift of the IR position has been discussed here many times since you have been following the forum. You have seen all the needed info several times. If you are confused you need to be specific on the aspect of it you don't understand. It may also be covered in the REW "Help". It is part of the control box on the Impulse tab. Maybe you just don't understand why I shifted it? I can't help you, if you can't help me.


Why would the automated SW REW timing alignment in the original file be significantly different.

I think you shifted it to show more clearly what i had missed?



> Okay, your final intended XO was active. You have no ability to adjust the relative delays. Your speakers are about same distance from the mains.


The subs are in the corners slightly behind outside each main.



> My analysis indicates there "can" be very good phase tracking through the entire extended XO range with the settings you have now. The only issue is if the delay between the SWs and mains is already good. Since the subs are about the same distance as the mains good timing is much more likely. If the SPL is not good then your only recourse is the variable phase control to try to improve the SPL.


No variable phase available.



> The way we investigate to determine if the timing is good in detail is the similar to that done in other threads.
> [First see below; there is no need to do additional measurements if the SPL is already acceptable in the XO range. You haven't provided that information yet.]
> 
> Measure:
> ...


I will do this 
_____________



> Thinking about this more; maybe you are missing the biggest picture.
> For a given room setup condition:
> 
> 1- If the XO range SPL is already reasonably near the target then all is well - done.


I will measure to clarify.



> 2- If the XO range SPL only varies a little and can be brought to acceptable level with moderate EQ then make that EQ adjustment - done.


I could introduce the Antimode for this if necessary. 



> 3- If there is a big dip in the XO range and reversing the polarity of the SWs removes the dip and places it in category 1 or 2 then make the change - done.


180 degrees seems to work the same for stereo as well as mono setup. The subs only have 0 and 180 degrees settings.



> 4- If the XO range is very lumpy or has a large dip that is not easy to remove with moderate EQ and/or a SW polarity change, then there may be a timing error that can be investigated more fully with REW to understand why. [In this case, Since no timing changes can be made, then there is nothing that can be done about it (except maybe the variable phase control).]


Is there a acceptable standard for this.



> Some dips in the XO range may be the result of room modes that may not be correctable even if we have all the proper controls to adjust.


Those modes would be 20 & 37hz



> Maybe you are at 1, 2 or 3 and for some reason fooling around with 4?
> 
> Some of us fool around with 4 just to better understand the details of the alignment and assure that it is adjusted as closely as possible to a "conventional setting" before EQ is applied. A reasonable SPL response is still the only practical objective however. It really doesn't matter if we first fine tune delay settings to a "conventional setting". I consider a "conventional" timing alignment to be one that has the closest phase tracking of the SW vs main through the entire XO range.


Because REL do things a bit different from others i am a bit restricted but have benefits in other ways so re-measuring to clarify my settings and fine tune. These subs are really good when finely tuned, why not use something like REW to do the job.



> I hope this helps, but I have the feeling that I keep telling you things that you already know. If you have additional questions please try to be more specific in your questions. It will ease my mind and save me time. Thanks!


Can you recommend a thread that you have been involved in that explains the timing align using a USB mic, i think it can be done but needs more work, is this correct?

Thanks again, ok will try to do this.


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## jtalden (Mar 12, 2009)

Phillips said:


> Why would the automated SW REW timing alignment in the original file be significantly different.


REW aligned the peak IR value of the each trace to 0 ms as you requested in your REW preferences settings. The peak value on one SW was positive and the other negative by small margins. When this happen the IRs are not overlaid in a way that is easy to quickly interpret polarity. 

[I noticed that if you select "Estimate IR Delay" manually REW will sometimes detect this and improve the alignment. It did so in this case, but it was still not well matched so I adjusted it further manually. All the fuzz on the IR traces did not make these traces easy for REW to automatically align. Also; if you change preferences to deselect "Set t=0 at IR peak" Then REW will not align the peaks at t=0 but the initial rise at t=0. In this case I don't think that would have helped anyway - too much fuzz. This only works for new REW sessions.

[For JohnM if listening: I notice that a change made to deselect "Set t=0 to IR Peak" it will not work on existing measurements, or on new measurements within the current REW session. It will work on new measurements in a new session of REW. I am not sure if this is a bug or is what you intended.] 



> I think you shifted it to show more clearly what i had missed?


Yes, it was only done to made the polarity more obvious to you. 



> No variable phase available.


Okay, then the only adjustment within the current setup is the polarity switch. You have already selected the best setting for this so the current system is "adjusted". If it looks good for SPL or can be EQ'ed to look good then all is well - done.

If not, then your other options are to move SW or speakers to change relative distance, or to change AVR and wiring or other equipment in the system to allow delay/distance adjustments.



> 4- If the XO range is very lumpy or has a large dip that is not easy to remove with moderate EQ and/or a SW polarity change, then there may be a timing error that can be investigated more fully with REW to understand why. [In this case, Since no timing changes can be made, then there is nothing that can be done about it (except maybe the variable phase control).]
> 
> Is there a acceptable standard for this.


What is "This"? [The rest of the questions are fine - thanks for the great improvement.]

A> Lumpy? - You can find opinions on the level of SPL variation, but there are no "standards". My personal level is; "as good as possible" given the inherent constraints resulting from my chosen setup (room, positions, speakers, and audio equipment).

B> Moderate EQ adjustment limit? - No.

C> Large Dip? - _(probably not what you meant )_

D> Allowable Timing Error? - _(probably not what you meant)_

E> Polarity setting? - _(probably not what you meant)_



> Can you recommend a thread that you have been involved in that explains the timing align using a USB mic, i think it can be done but needs more work, is this correct?


*This* one uses a USB mic.

It is complicated for me to make a recommend timing/distance change based on a single initial set of measurements. That is because the initial timing information is not available and must be determined by me through indirect means. This takes significant time and has risk of error. I get confused easily! If I find the initial timing/distance settings accurately then I can accurately recommend the best timing/distance settings by using REW math functions. 

For the person taking measurements in the room using the USB mic, it is not really a problem. The timing/distance adjustments can be made and the resulting measured SPL simply compared to other settings. The best setting can then be chosen.

In your case, since you have no timing/distance control to change, you have only 2 possible conditions; positive or negative SW polarity. You only need 2 measurements to confirm which setting provides the best SPL through the XO range.


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## Phillips (Aug 12, 2011)

> REW aligned the peak IR value of the each trace to 0 ms as you requested in your REW preferences settings. The peak value on one SW was positive and the other negative by small margins. When this happen the IRs are not overlaid in a way that is easy to quickly interpret polarity.
> 
> [I noticed that if you select "Estimate IR Delay" manually REW will sometimes detect this and improve the alignment. It did so in this case, but it was still not well matched so I adjusted it further manually. All the fuzz on the IR traces did not make these traces easy for REW to automatically align. Also; if you change preferences to deselect "Set t=0 at IR peak" Then REW will not align the peaks at t=0 but the initial rise at t=0. In this case I don't think that would have helped anyway - too much fuzz. This only works for new REW sessions.
> 
> ...


Thank you



> What is "This"? [The rest of the questions are fine - thanks for the great improvement.]
> 
> A> Lumpy? - You can find opinions on the level of SPL variation, but there are no "standards". My personal level is; "as good as possible" given the inherent constraints resulting from my chosen setup (room, positions, speakers, and audio equipment).
> 
> ...


Ok let me have another go.

Should it be flat or highest through the XO, i have seen different opinions on this.



> *This* one uses a USB mic.
> 
> It is complicated for me to make a recommend timing/distance change based on a single initial set of measurements. That is because the initial timing information is not available and must be determined by me through indirect means. This takes significant time and has risk of error. I get confused easily! If I find the initial timing/distance settings accurately then I can accurately recommend the best timing/distance settings by using REW math functions.
> 
> ...


I will have a read on this thread. I might have some more questions about this but will read the thread first. I would like to learn about this more. The USB mics do have some restrictions.

Thanks again for your patience


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## jtalden (Mar 12, 2009)

Phillips said:


> Ok let me have another go.
> 
> Should it be flat or highest through the XO, i have seen different opinions on this.


Either is fine. Flat implies very good phase tracking just as "highest" does. Highest is "highest overall" in the XO range not at one freq as at the XO freq. If there are modes in the range, and there almost always are, that makes it a little difficult to read the best setting, but we are looking for support through the range and if we have that, we are good. A 1-2 ms error is not an issue in practical terms. If we give away 3 dB in the XO range due to timing then we need 2x the power to the drivers to EQ it back. This is extra load on the P-amp and speakers that is unnecessary. If we have too much support in that area we can use EQ to flatten the response and reduce the power to the drivers easing the load on them. For those with lots of capacity this is not too important, but some people are using modest equipment.


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## Phillips (Aug 12, 2011)

jtalden said:


> Either is fine. Flat implies very good phase tracking just as "highest" does. Highest is "highest overall" in the XO range not at one freq as at the XO freq. If there are modes in the range, and there almost always are, that makes it a little difficult to read the best setting, but we are looking for support through the range and if we have that, we are good. A 1-2 ms error is not an issue in practical terms. If we give away 3 dB in the XO range due to timing then we need 2x the power to the drivers to EQ it back. This is extra load on the P-amp and speakers that is unnecessary. If we have too much support in that area we can use EQ to flatten the response and reduce the power to the drivers easing the load on them. For those with lots of capacity this is not too important, but some people are using modest equipment.


Thanks again

I generally go for more power than needed, i do it for cars and boats etc as well, don't have to work as hard.

Sometimes to much power in audio gear doesn't always work though.

Will check the thread suggested

Thanks again


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