TOPIC:

Hello there

I've been experimenting with miniDSP 2x4 HD in combination with REW and RePhase. 100 h. in I still didn't find the SQ and effect that I find satisfactory. So I bought the Dirac Live upgrade for the minidsp. And I must say that I'm initially very positive with the results. A handful measurements and 12 test profiles in, I have the initial frequency response that I like. -A magnitude better than I've achieved with REW and RePhase. It sounds better than ever.

But I have a question. -Right now I have my single SVS sub connected to the two RCA out (3+4) on the DDRC-24. And I wonder if the mixed phase corrections Dirac makes for L+R (1+2) will interfere with the signals to the sub and smear the outcome? Is it perhaps better to only use one RCA out to the sub or does it sum the signal identically either way? You can see the routing matrix attached.

You don't want to only have the sub connected to left or right, so your options are doing what you're doing or having say output 3 connected to the sub and this being routed (0 dB) to both left and right. What I do personally is the latter, but I suspect it won't make any acoustic difference either way. You could test by taking a measurement with our current setup and then compare to one with the routing changed as I described. 

Ultrasonic wrote:

You don't want to only have the sub connected to left or right, so your options are doing what you're doing or having say output 3 connected to the sub and this being routed (0 dB) to both left and right. What I do personally is the latter, but I suspect it won't make any acoustic difference either way. You could test by taking a measurement with our current setup and then compare to one with the routing changed as I described. 
 

Okay, I understand that summing two to one or two to two may be the same result but my main concern or question at hand is if the two L+R signals different corrected phases will interfere and smear the signal to the sub. I mean, won't the sub get two different signals because of the corrections made by Dirac and won't the result be a more or less smeared signal when the two are summed?

holdtdk wrote:

Ultrasonic wrote:

You don't want to only have the sub connected to left or right, so your options are doing what you're doing or having say output 3 connected to the sub and this being routed (0 dB) to both left and right. What I do personally is the latter, but I suspect it won't make any acoustic difference either way. You could test by taking a measurement with our current setup and then compare to one with the routing changed as I described. 


 

Okay, I understand that summing two to one or two to two may be the same result but my main concern or question at hand is if the two L+R signals different corrected phases will interfere and smear the signal to the sub. I mean, won't the sub get two different signals because of the corrections made by Dirac and won't the result be a more or less smeared signal when the two are summed?

You'll only get different adjustments in the crossover region with your main speakers, with how big and differences will be depending on how symmetric your room/setup is. You can't do anything about it though, with the potential compromise of only sending your sub the left or right channel signal being a MUCH bigger potential compromise. The reason being recorded audio signals in the frequency range covered by your sub can't be relied on to be mono (same on both channels), plus your sub will still have a crossover with both main speakers.

I send a summed left and right signal to my sub with speakers in an asymmetric room layout and it sounds good to me  .

I'll just add that if the MLP frequency responses for your two main speakers do differ then this may influence what frequency you choose to crossover at. I actually use a higher crossover frequency than I might otherwise to get to crossover at a point the responses are more similar (and in phase).

Ultrasonic wrote:

holdtdk wrote:

Ultrasonic wrote:

You don't want to only have the sub connected to left or right, so your options are doing what you're doing or having say output 3 connected to the sub and this being routed (0 dB) to both left and right. What I do personally is the latter, but I suspect it won't make any acoustic difference either way. You could test by taking a measurement with our current setup and then compare to one with the routing changed as I described. 



 

Okay, I understand that summing two to one or two to two may be the same result but my main concern or question at hand is if the two L+R signals different corrected phases will interfere and smear the signal to the sub. I mean, won't the sub get two different signals because of the corrections made by Dirac and won't the result be a more or less smeared signal when the two are summed?

You'll only get different adjustments in the crossover region with your main speakers, with how big and differences will be depending on how symmetric your room/setup is. You can't do anything about it though, with the potential compromise of only sending your sub the left or right channel signal being a MUCH bigger potential compromise. The reason being recorded audio signals in the frequency range covered by your sub can't be relied on to be mono (same on both channels), plus your sub will still have a crossover with both main speakers.

I send a summed left and right signal to my sub with speakers in an asymmetric room layout and it sounds good to me 

.

That's true. The room is quite symmetrical but the sub is placed at the side wall so is much closer to the left speaker than the right.

holdtdk wrote:

That's true. The room is quite symmetrical but the sub is placed at the side wall so is much closer to the left speaker than the right.

I think you realise but for my points above it doesn't matter where the subwoofer is in the room. 

You might like to have a look at what your Dirac Live filters actually look like, then you can see for yourself what differences exist. I tried to describe a good way to do this in the following post, but it would be worth reading around it a bit in the thread for full context. A little further down I give an example, although an extreme one as it was based on filters generated from measurements at a single location.

www.minidsp.com/forum/dirac-series-suppo...droom?start=75#63051

 

Ultrasonic wrote:

holdtdk wrote:

That's true. The room is quite symmetrical but the sub is placed at the side wall so is much closer to the left speaker than the right.

I think you realise but for my points above it doesn't matter where the subwoofer is in the room. 

You might like to have a look at what your Dirac Live filters actually look like, then you can see for yourself what differences exist. I tried to describe a good way to do this in the following post, but it would be worth reading around it a bit in the thread for full context. A little further down I give an example, although an extreme one as it was based on filters generated from measurements at a single location.

www.minidsp.com/forum/dirac-series-suppo...droom?start=75#63051


 

Oh, because the distance from sub to microphone is the same either way?

holdtdk wrote:

Oh, because the distance from sub to microphone is the same either way?

In part but basically you'll get an identical measurement whether you send a left or right channel frequency sweep to the sub. This won't be true of the main speakers, mostly down to the different interactions between the speaker output and the room (even if the speaker to microphone distances are identical).

Ultrasonic wrote:

holdtdk wrote:

Oh, because the distance from sub to microphone is the same either way?

In part but basically you'll get an identical measurement whether you send a left or right channel frequency sweep to the sub. This won't be true of the main speakers, mostly down to the different interactions between the speaker output and the room (even if the speaker to microphone distances are identical).

Yes, I think I got it now. Because I already set the crossover before running Dirac, the correction below the crossover point is the same for L+R signals below that crossover point because the sub is reproducing the sound in that range. (mostly).

holdtdk wrote:

Yes, I think I got it now. Because I already set the crossover before running Dirac, the correction below the crossover point is the same for L+R signals below that crossover point because the sub is reproducing the sound in that range. (mostly).

Yes. What crossover type are you using actually? The steeper the crossover the smaller the range of frequencies where you'll have both sub and main speakers meaningfully contributing and so potentially causing the issue that concerns you. Other factors to consider though are what your speakers natural roll-off is and what the crossover frequency is.

Ultrasonic wrote:

holdtdk wrote:

Yes, I think I got it now. Because I already set the crossover before running Dirac, the correction below the crossover point is the same for L+R signals below that crossover point because the sub is reproducing the sound in that range. (mostly).

Yes. What crossover type are you using actually? The steeper the crossover the smaller the range of frequencies where you'll have both sub and main speakers meaningfully contributing and so potentially causing the issue that concerns you. Other factors to consider though are what your speakers natural roll-off is and what the crossover frequency is.

I've tried all the types available to be honest. I'm a patient bloke. Ultimately Linkwitz Riley 48 dB/Oct. was chosen as both low-pass and high-pass not because it was the absolute flattest at the crossover point but because it sounds the "driest" "cleanest" to my ear.

My speakers are tower speakers, System Audio Mantra 70 which goes quite low but due to placement I get more bass out of my SVS sub.

My setup is similar: a subwoofer with floorstanding speakers crossed over using LR 48 dB/octave filters. So long as the crossover isn't too low this should work well. With standmounts with more limited bass extension more care needs to be taken not to 'double-up' by an applied filter overlapping the natural roll-off and resulting in too little contribution from the main speakers.

Anyway, the sharp filters you have will limit the issue you started the thread about  .