Subwoofer DSP - delay adjustment - align phase or best response ?

[Buckster]

I'm a bit confused to whether adjusting Subwoofer DSP and time alignment whether you should try to align for phase or for the best response please ?

I've a SVS Ultra 13, Polk R200 L/R, Genelec 8030C (centre), KEF Q350s as rears then front dolby atmos and rear heights

If I run REW on the R200 (crossed over at 60hz) running them full range, then compare to a sweep of the subwoofer I can align the phase of the Sub to the R200 at the crossover point

but when I do that I get a massive peak of bass around 50-70hz presumably as the subwoofer and R200 are both adding to the response, and it doesn't sound great at all

presumably that is the "most aligned" but not necessarily the best option, so is it better just to align to best overall response and ignore the phase ? as in adjust the distance of the subwoofer to remove any room nulls produced either by the fronts or any other speaker ? or just for the flattest overall response

I guess this is also why some recommend same crossover for all speakers, as the alignment of the sub at 60hz for the L/R is different when looking at phase to aligning with the Centre which is crossed over at 100hz

 

[Vladimir Filevski]

Crossover frequency at 60 Hz is too high. Looking at the anechoic response of Polk R200, 50 Hz is more likely to be the correct crossover frequency, but if you include room modes, maybe you should go even lower in frequency. Please post measured frequency response of Polk R200 in your room at the listening position.

 

[Keith_W]

The goal is phase alignment to get rid of XO cancellation. But I actually do both - first, I time align subs to mains. The goal is to align to within less than 1/4 period of the XO frequency. So if your XO freq is 50Hz, one period is 20ms. The subs need to be aligned to the mains to a +/- 2.5ms tolerance. Then I align the phase to get rid of cancellation at the XO point.

 

[3ll3d00d]

Looking at the anechoic response of Polk R200, 50 Hz is more likely to be the correct crossover frequency, but if you include room modes, maybe you should go even lower in frequency

That's a bad idea

It's clear the speaker has a port tune at about 50Hz and distortion rises from 80 or so down. A typical xo for sub (eg 80 +/- 10) is going to make sense, tweak exact xo based on room response

 

[Vladimir Filevski]

That's a bad idea

Clearly there is a misunderstanding on my side about the OP question. I thought OP wanted simply to add sub to the existing L/R speakers (Polk R200), without applying high-pass filter to Polk R200. It is still not clear to me if this is what the OP did, or intended to do.

 

[Vovgan]

I'm a bit confused to whether adjusting Subwoofer DSP and time alignment whether you should try to align for phase or for the best response please ?

I've a SVS Ultra 13, Polk R200 L/R, Genelec 8030C (centre), KEF Q350s as rears then front dolby atmos and rear heights

If I run REW on the R200 (crossed over at 60hz) running them full range, then compare to a sweep of the subwoofer I can align the phase of the Sub to the R200 at the crossover point

but when I do that I get a massive peak of bass around 50-70hz presumably as the subwoofer and R200 are both adding to the response, and it doesn't sound great at all

presumably that is the "most aligned" but not necessarily the best option, so is it better just to align to best overall response and ignore the phase ? as in adjust the distance of the subwoofer to remove any room nulls produced either by the fronts or any other speaker ? or just for the flattest overall response

I guess this is also why some recommend same crossover for all speakers, as the alignment of the sub at 60hz for the L/R is different when looking at phase to aligning with the Centre which is crossed over at 100hz

Here is what I did with my SVS subs and Denon AVR that improved everything to the next level. Posted it jn another thread, copying here:

ALL SUBWOOFER OWNERS — PLEASE READ THIS

Over the last week I achieved more progress in aligning my subs with my mains (and rear surrounds) than I had in the previous five years.

And I’ve tried everything: Audyssey MultEQ-X with custom PEQ filters, REW with a UMIK-1, different crossover frequencies, different phase settings… you name it.

But this week I did two major things:

1) I inverted the polarity of my subs from positive to negative in the SVS app.

Turns out this is not the same as applying a 180° phase shift. (If in doubt, ask AI why.) My Revel F208 speakers and subs were aligned in positive polarity when running full-range, but not when crossed over. Again, ask AI why a crossover often introduces an effective 180° shift (roughly +90° on the speakers and –90° on the subs). After inverting polarity, the sound improved A LOT.

2) I plugged the ports on my Revel speakers when crossing them over to the subwoofers. This also made the sound noticeably cleaner. I “lost” around 2 dB of bass between 50 and 140 Hz according to REW, but AI says that I am “not "losing" 2 dB of bass. You are successfully removing 2 dB of resonant, slow, boomy port bloat”. Like I said it definitely sounds cleaner and I am not hearing any less bass after plugging the f208 speaker ports when they are crossed with subs @60Hz.

I cannot begin to describe how much the overall sound improved. The bass is super tight - more massive but never overbearing. Just pure joy. (Of course, I still used PEQ on individual speakers, but I had done that before too.)

P.S. Audyssey cannot and thus will not flip subwoofers polarity for you even if needed, so that was the reason I was stuck. But AI says that Dirac Live Bass Control (DLBC) does this, and “it's the entire reason DLBC is a "magic" technology”. Or you can save a few hundred bucks and do it (at least try if you haven’t) like I did: manually.

(It’s kind of bewildering now that I see the effect to think that after so many years and so many millions of AVRs sold Denon have not incorporated this simple test for subs polarity in their auto calibration - which way subs play better with main speakers - and will rather do insane things like putting crazy distances to subs to try to compensate for polarity, and as an effect will create more problems and solve none)

If this helps your system as well, feel free to donate a like or something!

 

[OCA]

Here is what I did with my SVS subs and Denon AVR that improved everything to the next level. Posted it jn another thread, copying here:

ALL SUBWOOFER OWNERS — PLEASE READ THIS

Over the last week I achieved more progress in aligning my subs with my mains (and rear surrounds) than I had in the previous five years.

And I’ve tried everything: Audyssey MultEQ-X with custom PEQ filters, REW with a UMIK-1, different crossover frequencies, different phase settings… you name it.

But this week I did two major things:

1) I inverted the polarity of my subs from positive to negative in the SVS app.

Turns out this is not the same as applying a 180° phase shift. (If in doubt, ask AI why.) My Revel F208 speakers and subs were aligned in positive polarity when running full-range, but not when crossed over. Again, ask AI why a crossover often introduces an effective 180° shift (roughly +90° on the speakers and –90° on the subs). After inverting polarity, the sound improved A LOT.

2) I plugged the ports on my Revel speakers when crossing them over to the subwoofers. This also made the sound noticeably cleaner. I “lost” around 2 dB of bass between 50 and 140 Hz according to REW, but AI says that I am “not "losing" 2 dB of bass. You are successfully removing 2 dB of resonant, slow, boomy port bloat”. Like I said it definitely sounds cleaner and I am not hearing any less bass after plugging the f208 speaker ports when they are crossed with subs @60Hz.

I cannot begin to describe how much the overall sound improved. The bass is super tight - more massive but never overbearing. Just pure joy. (Of course, I still used PEQ on individual speakers, but I had done that before too.)

P.S. Audyssey cannot and thus will not flip subwoofers polarity for you even if needed, so that was the reason I was stuck. But AI says that Dirac Live Bass Control (DLBC) does this, and “it's the entire reason DLBC is a "magic" technology”. Or you can save a few hundred bucks and do it (at least try if you haven’t) like I did: manually.

(It’s kind of bewildering now that I see the effect to think that after so many years and so many millions of AVRs sold Denon have not incorporated this simple test for subs polarity in their auto calibration - which way subs play better with main speakers - and will rather do insane things like putting crazy distances to subs to try to compensate for polarity, and as an effect will create more problems and solve none)

If this helps your system as well, feel free to donate a like or something!

A1 Evo Express is free, works with your Denon (through Audyssey interface) and can not only invert sub polarities if needed but will align them better than you can manually do. It takes 15 minutes in total including the measurement step. Just make sure you turn off all processing in your subs before. You can thank me later.

 

[Buckster]

Huge apologises everyone - just realised I hadn't replied very sorry

Thanks very much for the replies

I've spent more time on the delay for the sub (using the time alignment feature in REW) - which added a large delay to the sub (approx equivalent to +2metres) - and this has definitely minimised the large dip I was getting when doing a sweep of the mains

in answer to a question earlier - yes sorry the mains are crossed over (now at 80hz I think)

OCA - I just watched your latest uploaded video on youtube A1 EVO AcousticX and what an amazing bit of software (great video too !). Makes me want to upgrade to an AV amplifier with MultiEQ-X. Unfortunately the upgrade path from my Denon X7200W to either a X4800 (which might be a slight overall downgrade in performance but not features) or a X6800 is VERY costly - and can't really afford/justify unless the X7200W completely fails

I think I spent £1500 on my X7200W 10 years ago and apart from the odd minor glitch and an issue with 2 of the rear speaker terminals (board behind the terminals)- it has been FANTASTIC - the 6800W would be £2300

 

[Oddball]

Huge apologises everyone - just realised I hadn't replied very sorry

Thanks very much for the replies

I've spent more time on the delay for the sub (using the time alignment feature in REW) - which added a large delay to the sub (approx equivalent to +2metres) - and this has definitely minimised the large dip I was getting when doing a sweep of the mains

in answer to a question earlier - yes sorry the mains are crossed over (now at 80hz I think)

OCA - I just watched your latest uploaded video on youtube A1 EVO AcousticX and what an amazing bit of software (great video too !). Makes me want to upgrade to an AV amplifier with MultiEQ-X. Unfortunately the upgrade path from my Denon X7200W to either a X4800 (which might be a slight overall downgrade in performance but not features) or a X6800 is VERY costly - and can't really afford/justify unless the X7200W completely fails

I think I spent £1500 on my X7200W 10 years ago and apart from the odd minor glitch and an issue with 2 of the rear speaker terminals (board behind the terminals)- it has been FANTASTIC - the 6800W would be £2300

All this will get you only so far. There is little you can do about decay with a single sub. Even with 4 subs building DBA is not easy or fully bulletproof. Once you are ready to upgrade, D&M offers Dirac ART which will just take care of things in the way we were not able to do before. Not sure if you need 6800H for 13 channel count - for 11 channels 3800H will do just fine.

 

[Buckster]

All this will get you only so far. There is little you can do about decay with a single sub. Even with 4 subs building DBA is not easy or fully bulletproof. Once you are ready to upgrade, D&M offers Dirac ART which will just take care of things in the way we were not able to do before. Not sure if you need 6800H for 13 channel count - for 11 channels 3800H will do just fine.

our room is very square so it is very difficult from an EQ point of view with a single sub

I am tempted to get a 2nd sub but its not a cheap investment. I was thinking of maybe a SVS SB3000 to complement the SVS PC-13 Ultra I have. I did purchase from a retailer (arrived today) some additional port bungs as I wanted to at least try the SVS PC-13 Ultra in Sealed mode as I have to apply so much EQ around the 29-37hz area, I was one port bung short so 3 new ones arrived today (just had to pay postage, the port bungs were kindly from SVS/retailer free - great service)

to get a reasonably flat response to remove remove gain I currently have to run the SVS in

Extended Port tuning
-21dB overall gain
25 hz room compensation - 12db slope
-12dB filter at 31hz - Q6.2
-4.5db filter at 34hz - Q7.2

so can see if I have to remove a lot of room associated gain from a bit above 20hz right up to low 40s

my SVS PC-13 is on its 3rd amp now, so it has the latest STA1000d amplifier, I'm interested to see how it will perform in Sealed mode

the only 2 options in my pricerange are the SB3000 (as a sealed option) and a PB-2000 Pro (as a ported option)

if I run Roomsim in REW - a 2nd sub doesn't look as much improvement as I would have thought but does look a bit more smoothed out in the extremes of responses

 

[Buckster]

A1 Evo Express is free, works with your Denon (through Audyssey interface) and can not only invert sub polarities if needed but will align them better than you can manually do. It takes 15 minutes in total including the measurement step. Just make sure you turn off all processing in your subs before. You can thank me later.

thankyou for your reply and for your great set of tools - I've watched a large number of your youtube videos, but more from an education and interest point of view as had always assumed none of the features of the Evo tools would work on the older Denons. ref A1 Evo Express are you saying will work even with the older amps that have the encrypted EQ/configuration files, I know uploading the EQ won't work, but will it read the config (via web-interface) and perform all of the calibration sweeps, crossover recommendations, interface with REW etc for these older amps ?