Stereo Bass using subwoofers

[Krunok]

So here's how I do the downmix:

# Stereo Bass
Copy: RL=1*L RR=1*R C=0 SUB=0 SL=0 SR=0
# Mono Bass
#Copy: RL=0.707*L+0.707*R RR=0.707*R+0.707*L C=0 SUB=0 SL=0 SR=0

Channels RL and RR go to the subwoofer DAC. I don't perceive the mono bass as much louder and -3dB should be correct for summing two channels, right? I can switch between mono and stereo just by switching the comment statement between the Copy commands. The mono bass is more central than the stereo bass (not that the stereo bass wouldn't be in the middle), and seems more defined, but the stereo bass has more detail. Checked polarity just now, it's correct.

Yep, -3dB seems like a pretty good solution to me.

 

[Severian]

That raises the question, What is mono? We had endless arguments over this in the past. Is it A+B, (A+B)/2, (A+B)/Sqrt2

Yeah, I don't fully understand what's going on or if I'm doing it correctly. When my subs were a single channel, I had my DSP's mixer set such that IN1 and IN2 were both low-passed to OUT3. Now with two channels of sub amplification, I send the same low-passed signal to OUT4.

Frankly I don't worry too much about it. I adjust the gain on all of my amps to get a civilized downward slope in REW and make what corrections I can with EQ filters. If the mono signal is hotter than it "should" be, I end up compensating for it with lower gain on the amp. But for actual listening, I'm constantly adjusting the gain on the subwoofers to taste anyway.

 

[Krunok]

. But for actual listening, I'm constantly adjusting the gain on the subwoofers to taste.

That is not EQ-ing, that is post-producing.

 

[Krunok]

If you got a room mode in the form of a “suck out” ie suddenly -10dB or even more energy could disappear at some frequency.
You can’t really compensate by pouring more power into to this “black hole”

"Black hole" is popular but actually false concept when it comes to room modes. As peaks are not indefinitely high the dips as well are not indefinitely deep. Usually EQ software raise dips not more than 10-12dB and that gives very noticeable results.

Of course, it goes without saying that things are much much easier with multiple subs.

 

[Severian]

That is not EQ-ing, that is post-producing.

I make no claims to my approach being true high-fidelity. Sometimes I'm listening to dance music and want it to sound like a club. Sometimes my wife is home and doesn't want to house shaking!

 

[Mnyb]

"Black hole" is popular but actually false concept when it comes to room modes. As peaks are not indefinitely high the dips as well are not indefinitely deep. Usually EQ software raise dips not more than 10-12dB and that gives very noticeable results.

Of course, it goes without saying that things are much much easier with multiple subs.

Yes you are rigth but raise a dip 10dB in the bass is an awful lot of power ( I do consider that a black hole )? Is it not ? You better have a system that has 10dB headroom above what’s you comfortable listening to at any frequency if you do this .

But some of you do , was it 4 subs with multiple large drivers ? That would do it .

 

[Severian]

Thanks, Severian, seems you had a similar experience. Interesting. My impression is that the woofers all firing in tandem makes a big difference in output (duh) vs even increased levels of stereo (independent) signals. My initial thought was that this could be overcome with increasing the signal levels, but not so much in my experience.

My interest in this is that it determines my equipment list - I had planned on completely eliminating the integrated amp - running the Topping as a pre-amp/DAC, with the advantages of one less component, using XLR and the resulting extremely clean signal path of DX7PRO to a Hypex 122MP based amp along with the RCAs to the powered subs.

This bass "issue" however make that not the favored approach. Although the rest of the spectrum is astonishing, the lack of bass and how the subs and mains gain up differently with volume adjustment makes the Topping not a good performer as a pre-amp.
Disappointing, but hey, first world problems...

What you need to do is handle the crossover with DSP, either an external unit following the Topping or in software outputting to multiple DACs or a multichannel DAC.

 

[Krunok]

I make no claims to my approach being true high-fidelity. Sometimes I'm listening to dance music and want it to sound like a club. Sometimes my wife is home and doesn't want to house shaking!

Oh, I was only joking. Not to mention that every reasonable man tries to keep wife happy.

 

[digitalfrost]

Found an interesting piece by Ken Rockwell on the issue:

https://www.kenrockwell.com/audio/stereo-subwoofers.htm

I can mostly confirm his findings, also that subwoofers are locateable despite crossing over at 80hz.

 

[Krunok]

Yes you are rigth but raise a dip 10dB in the bass is an awful lot of power ( I do consider that a black hole )? Is it not ? You better have a system that has 10dB headroom above what’s you comfortable listening to at any frequency if you do this .

Yes, you will loose 10dB of headroom but 100-150W amps driving medium sensitive speakers (app 87dB/1W/1m) would still be able to deliver more SPL than your neighbours will like.

 

[Krunok]

.., also that subwoofers are locateable despite crossing over at 80hz.

I definitely don't share that experience.

 

[Mnyb]

I xo my rythmik 15” sub at 60 Hz , a single sub i’m slumming. It’s a really good sub it’s dead quit no rattle no “f*rt” noises just bass i just can’t locate the damn thing , a large step up from my old rel stadium 3 that died on me ...

 

[dkinric]

Found an interesting piece by Ken Rockwell on the issue:

https://www.kenrockwell.com/audio/stereo-subwoofers.htm

I can mostly confirm his findings, also that subwoofers are locateable despite crossing over at 80hz.

Not a big KR fan, but he did discuss the issue - thanks for the link!
Ken advocates for stereo subs for high fidelity music reproduction and claims there is stereo bass recorded in modern recordings (circa 2014 mind you) and benefits to be had from this setup. He also suggests a low as practical x-over point - below 80hz.

 

[levimax]

Due to WAF in a new house I am thinking about multiple subs for a 20' X 25' room with sloped 8' to 16' ceiling. Any recommendations on good value high performance blue tooth subs that "look good" or are as non obtrusive as possible?

 

[dkinric]

As far as good looking / unobtrusive subs, I would look at the Martin Logan Dynamos. The sealed varieties are small and with downfiring woofers and high output, built in DSP and app control, as well as wireless option - are a great option.
https://www.martinlogan.com/en/category/powered-subwoofers

Sister company Paradigm has something similar with the Defiance X series:
https://www.paradigm.com/en/subwoofers

 

[Mnyb]

Not a big KR fan, but he did discuss the issue - thanks for the link!
Ken advocates for stereo subs for high fidelity music reproduction and claims there is stereo bass recorded in modern recordings (circa 2014 mind you) and benefits to be had from this setup. He also suggests a low as practical x-over point - below 80hz.

There in lies a misunderstanding it does not matter if it’s stereo information < 80 HZ in the recordings for this issue.

Well I can think of uses with smaller speakers higher xo points and gentler xo slopes that do require stereo subs close to the speaker , so it’s all about the application

 

[dkinric]

There in lies a misunderstanding it does not matter if it’s stereo information < 80 HZ in the recordings for this issue.

Well I can think of uses with smaller speakers higher xo points and gentler xo slopes that do require stereo subs close to the speaker , so it’s all about the application

It does matter as far as output goes. I understand low frequencies are non-directional, but if one of your two subs is getting less / or a different signal than the other sub, it will affect the overall sound significantly vs both getting the same signal at the same time.

 

[Krunok]

It does matter as far as output goes. I understand low frequencies are non-directional, but if one of your two subs is getting less / or a different signal than the other sub, it will affect the overall sound significantly vs both getting the same signal at the same time.

Driving 2 subs with stereo signal makes sense if you have each of them near your mains so they are acting as a pair of large speakers. In any other placement scenario inputting stereo signal to a pair of subs doesn't make much sense.

 

[thewas]

I definitely don't share that experience.

Neither do I, when subs crossed at 80 Hz are still locateable it is usually due to one or more factors creating hearable higher frequency components like low crossover order, higher order distortion noises from the drivers or ports or sometimes also vibrations from the sub housings or furniture.

 

[EB1000]

In the case where bass management software is used, then dual-mono if better, as it allows smoother response and better null cancellation.