Any advantage to stereo subs?

[AJ Soundfield]

Would any recording/mixing engineer in their right mind mix out the Stereo LF?

They don't for classical etc
https://www.aes.org/e-lib/browse.cfm?elib=13358
https://www.diyaudio.com/forums/the-lounge/247583-human-ear-localize-bass-18.html
...and now back to Simon Sez...

 

[ddude003]

Simon Sez... Techno, House, Trance, Psy, Goa... Shpongle...

I met a guy in New Zealand a few years ago that made various kinds of steel drums as well as other Aboriginal musical instruments... Some of them could make it below 45Hz...

 

[Greg Dunn]

I can't read the (paywalled) AES article, but the Australian article doesn't seem applicable - they tested entirely with headphones, which of course has nothing to do with subs.

I did haul the second sub downstairs and went through the steps to position, level match, and then EQ the composite setup. One sub had a slight null around 45 Hz where the other did not, so I thought there might be the possibility of them complementing each other. The measured response with both in place, unfortunately, didn't vary much at all from what I had originally; I did sweeps, impulse and RTA captures for each sub separately and all together. And while the measurements didn't look much different, initial listening impressions are that the two subs in stereo don't seem to have the LF extension of the single sub, and I haven't heard any spatial differences. Maybe there's some cancellation between the channels on music which doesn't exist in the (mono) test signals. It's hard to say when I don't see any issues in the measurements to point a finger at.

I'm going to do some more listening this week, and will report back if I discover anything worth mentioning. So far it's been an interesting experiment but without any revelations.

 

[AJ Soundfield]

I can't read the (paywalled) AES article

Which is precisely why I posted the relevant summary.

Australian article doesn't seem applicable - they tested entirely with headphones, which of course has nothing to do with subs.

It is a non-paywall article showing inter-aural phase differences below 80hz are audible, including using subs like the AES papers which concur. This is established science, not Simon Sez.

I'm going to do some more listening this week, and will report back if I discover anything worth mentioning. So far it's been an interesting experiment but without any revelations.

A single pressure mic cannot measure what 2 ears/brain hear. Of course there is no guarantee that you (or anyone else) will hear any difference with stereo subs in your home experimenting due to several factors, hence the highlighted areas of the AES paper.
The only guarantee, is with mono <80-90hz, there will be zero (VLF) spatial reproduction.
For most, no big deal.
For those with this type requirements for fidelity, absolutely critical, explained, no paywall slide 35.
As always, YMMV.

cheers

 

[Greg Dunn]

Just wanted to follow up (and thank everyone for their contributions).

I've run some additional tests, using both music and test tones - ears only. Again, my crossover is at 60 Hz, 24 dB/octave and the in-room response is decently flat down to 15 Hz (±2 dB in the listening area). It is only an 1800 cubic foot room, fyi, so there isn't much space for extremely low frequencies to develop.

I reached out to some friends who had suggestions for low frequency tracks with known stereo bass to evaluate. Despite using a fairly wide variety of music, I was able to switch from stereo to mono and there was never a difference in the lateralization of the sound sources. In fact, I got on the floor and placed my head "between" the subs (at least, much closer to them than to the mains) and couldn't detect the slightest bias in bass level left-to-right even when I turned one of the subs off! Stereo sounded like stereo in each case.

Then I used both sweep and steady tones sending them to the mains one at a time, full range, subs off. Localization of the sound source was fairly easy at 80 Hz, started to disappear below roughly 75 Hz and by 65 Hz it was gone. As a separate and extreme test, I stood between the mains and then next to the speaker which was off, and in neither case was I able to reliably identify which speaker was producing the sound below 65 Hz. Standing very close to the active speaker I could determine that it was playing, but it was surprisingly not that distinct. 5 or more feet away, there was no chance.

All in all, an interesting and informative exploration. For me and in my room, I am now confident that a 60 Hz crossover and mono subs is entirely satisfactory.

 

[DanDan]

There are tests more likely to show up the differences. e.g. Turn the mains off. 80Hz would probably reverse the conclusion. Impulsive tones vs steady state. It is a tough call between optimising LF by using the opportunity supplied by multiple subs, and the full range speaker. I suspect FR speakers which have the LF driver at the floor would change the bias in another direction. No floor bounce.
Tx for the journey in any case.

 

[linearphase]

You may hear a difference on a few acoustic audio recordings done in large spaces. Like an Organ recording done in a cathedral. About 30% of the people I have tested are repeatedly able to do this in an admittedly non double blind test. Interestingly some, myself included, perceive the difference as these sound being closer to what it is an an actual cathedral in that there is more ambience on the note decays. the rest just say it sounds better but can not describe what they are hearing. None has said they can hear any difference where the sound is coming from. On most recordings though there is no difference that anyone has been able to reliably detect.
Notably the bass in the case where it can be noticed can be measured as a little out of phase using a digital storage oscilloscope at the sub terminals.