Never Put Subwoofers In Corners... Even with DSP and Multi-Sub Setups?

[Duke]

Because most people don't put their speakers against the walls, and to do "stereo bass" they put their subs right next to their speakers.

Ah, I hadn't thought of that. I see what you mean.

 

[RichB]

Because most people don't put their speakers against the walls, and to do "stereo bass" they put their subs right next to their speakers. The distance to the walls causes SBIR which is normally avoided with proper sub placement.

In addition, the subs are generally not aligned as a mono source, which causes them to work against each other and potentially the main speakers, too. That is what mono subs and bass management solves.

This is my current plan because that is where the space is located. When my Rythmik subs come in, I'll measure and see how well it works.

- Rich

 

[jtwrace]

Because most people don't put their speakers against the walls, and to do "stereo bass" they put their subs right next to their speakers. The distance to the walls causes SBIR which is normally avoided with proper sub placement.

In addition, the subs are generally not aligned as a mono source, which causes them to work against each other and potentially the main speakers, too. That is what mono subs and bass management solves.

You mean like the Wayne Parham writeup?

https://audioroundtable.com/forum/index.php?t=msg&&th=3387&goto=66914#msg_66914

https://audioroundtable.com/forum/index.php?t=msg&th=16726&goto=69874&#msg_69874

https://audioroundtable.com/forum/index.php?t=msg&th=17930&goto=74653&#msg_74653

 

[Duke]

You mean like the Wayne Parham writeup?

https://audioroundtable.com/forum/index.php?t=msg&&th=3387&goto=66914#msg_66914

https://audioroundtable.com/forum/index.php?t=msg&th=16726&goto=69874&#msg_69874

https://audioroundtable.com/forum/index.php?t=msg&th=17930&goto=74653&#msg_74653

I like Wayne's flanking subs concept, wherein he places stereo subs halfway between the main speakers and the wall behind them, to fill in the wall bounce dip. They probably help smooth the in-room response in other ways as well.

Here's a quote pulled from one of the posts you linked to:

"You aren't looking for phase coherence, actually just the opposite. We're looking for phase difference. If the mains were coherent with reflections off the walls, ceiling and floor, we wouldn't need flanking subs. But they're not, and the interference that results creates distinct peaks and dips in various places throughout the room, especially at low and low/mid frequencies in the modal range. So we have to abandon the idea of coherent summation, and go for the next best thing, which is dense interference. It makes the modal range act a little more like the reverberant field, statistically averaged in a sort of homogenous sound distribution throughout the room."

 

[LightninBoy]

"never put a subwoofer in the corner"

Is that you, Patrick Swayze?

 

[Kvalsvoll]

Is this true, though? The bass pressure sensation comes from SPL, which is, in a room, equally all around you (more or less).

No, that is not quite exactly true (Referring to previous answer).

Hearing is pressure-sensitive - SPL. While we can detect direction down to around 60Hz, the harmonics will be what determines perception of sound source location, because the directional cues from the harmonics are so much larger they completely mask the lower frequency direction. To get good localization and realistic images of bass instruments, you need to address early reflections in lower midrange - fix that, and bass instruments will move to their intended location. The bass-system should always be mono, there are reasons for that.

Tactile sensations are more complex than hearing. Sound intensity, particle velocity and phase between velocity and pressure has significance for how the sound is experienced on our body. But direction is not important for tactile perception, and generally we can not detect direction of a soundfield through tactile feel.

If you measure the soundfield in a room at low frequencies, you will find that direction is all over, and does not correlate to location of the speakers. So when you think you hear bass coming from one speaker, it is the higher harmonics you hear, because the direction of the sound in itself is determined mostly by room acoustics.

 

[Hipper]

No, that is not quite exactly true (Referring to previous answer).

Hearing is pressure-sensitive - SPL. While we can detect direction down to around 60Hz, the harmonics will be what determines perception of sound source location, because the directional cues from the harmonics are so much larger they completely mask the lower frequency direction. To get good localization and realistic images of bass instruments, you need to address early reflections in lower midrange - fix that, and bass instruments will move to their intended location. The bass-system should always be mono, there are reasons for that.

Tactile sensations are more complex than hearing. Sound intensity, particle velocity and phase between velocity and pressure has significance for how the sound is experienced on our body. But direction is not important for tactile perception, and generally we can not detect direction of a soundfield through tactile feel.

If you measure the soundfield in a room at low frequencies, you will find that direction is all over, and does not correlate to location of the speakers. So when you think you hear bass coming from one speaker, it is the higher harmonics you hear, because the direction of the sound in itself is determined mostly by room acoustics.

If I were to play test tones (such as these from Real Traps: https://realtraps.com/test-cd.htm ), which presumably do not have any harmonics, making them come from say the left speaker only, could I test this idea that below around 60Hz we can't detect the source?

 

[Hipper]

The system I peddle consists of four passive subwoofers which normally are connected in series-parallel and driven by an amp which goes on the shelf or equipment rack. So the only wires which wrap partway around the room are speaker wires. There is one set of speaker wires running from the amp to the first sub on each side of the room, and a second set of speaker wires running from that first sub to the second one. The "first" subs each have two sets of terminals because they will be connected to two sets of speaker wires, while the "second" subs only have one set of speaker terminals.

In case anybody wants to DIY something like this, the amp I use is available from Parts Express.

Peddle power!

I knew of battery and of course mains power. Presumably you get a partner to do this in another room because of the noise - rusty chains, groans and grunts of your slave.

 

[Duke]

Hi Kvalsvoll,

Your post is excellent and educational, explaining things to a deeper level of understanding than I could have. Thank you.

I do have a question about one thing:

The bass-system should always be mono, there are reasons for that.

Could you mention what those reasons are? You don't necessarily have to go into detail. I'm interested in what line(s) of thinking led you to that conclusion.

Thanks.

 

[win]

Could you mention what those reasons are? You don't necessarily have to go into detail. I'm interested in what line(s) of thinking led you to that conclusion.

I look forward to his reply, but my 0.02 is that you get enough directionality from your mains for bass, and you might as well use all the subs you have to complement each other, and have them work together. If they are playing something that actually has stereo bass separation, you can end up getting unpredictable interactions between the different channel subs.

I only have two subs, so the equation might change if you have 4, but I reluctantly went mono subs after trying a stereo setup. Specifically, one of my subs had a deep null at 90hz, and running them out of phase with each other did a swell job of fixing that null. If there was actual stereo separation, the frequency response would be unpredictable, depending on if the two subs are playing the same music. It seems like most modern music is mixed to have mono bass anyway. Ditto RIAA (?).

 

[Kvalsvoll]

If I were to play test tones (such as these from Real Traps: https://realtraps.com/test-cd.htm ), which presumably do not have any harmonics, making them come from say the left speaker only, could I test this idea that below around 60Hz we can't detect the source?

Try, and hear. A pure sine wave will be difficult to detect where it comes from, at any frequency. You may be able to hear the speaker, because any harmonic distortion or noise or vibration from the speaker will stand out unmasked, when there is no other sound present at higher frequencies, that would otherwise mask the distortion. Pure 60Hz will only be possible to detect at close to 90 degrees horisontal, with no other masking sound present.

 

[Chromatischism]

the frequency response would be unpredictable, depending on if the two subs are playing the same music

Yes - if the subs aren't playing the same signal at all frequencies, they're going to be at times pushing against each other - and the main speakers - and the effect will vary with frequency.

 

[Kvalsvoll]

Could you mention what those reasons are? You don't necessarily have to go into detail. I'm interested in what line(s) of thinking led you to that conclusion.

In most installations the response from each subwoofer unit will be different, and the sum of all subwoofers will be different from those again, which means you will not be able to get a similar response for only L, only R and L+R. Bass will be different depending on which channel it is mixed into.

 

[Thomas savage]

"never put a subwoofer in the corner"

Is that you, Patrick Swayze?

View attachment 79067

Beat me too it ... Nobody puts @amirm in a corner either, unless you want to read 30 pages of circular back and forth with heavy doses of appeals to authority...

 

[Duke]

In most installations the response from each subwoofer unit will be different, and the sum of all subwoofers will be different from those again, which means you will not be able to get a similar response for only L, only R and L+R. Bass will be different depending on which channel it is mixed into.

Agreed, and very well explained. Thank you.

 

[Kvalsvoll]

Hi Kvalsvoll,

Your post is excellent and educational, explaining things to a deeper level of understanding than I could have. Thank you.

And thank you for this nice and positive comment. Being an engineer, I am not much into smalltalk, and I mostly miss any opportunity to leave nice words, when deserved.

 

[Lbstyling]

This article seems to go against a lot of what I hear on the forum: (Is this guy just trying to sell something?)

https://www.acousticfields.com/why-you-should-never-place-subwoofers-in-your-corners/

"So don’t buy into this culture of putting the subwoofer in the corner. And definitely don’t buy into the culture of multiple subs will smooth out the frequency response. Yes, technically it will but the smoothness, the level of smoothness that you get in the bump is so minuscule, it’s maybe 1 or 2 dB."

Pretty sure it's going to sum and be +3dB or -3dB, plus a MiniDSP should be able to help even more.

Also, if it's just adding a bunch of gain putting it in the corner, DSP would fix that too it seems: I have my Genelec's in a corner and they measure flat down to 18hz or so.

I remember another user who said that it's all about controlling the peaks and nulls in the room, and even ringing and smear can be controlled just by having a DSP system take care of the peaks, which goes against what this guy says about treatment:

"Put that money in treatment. You’ll be way better off. Use less energy, more treatment and balance it out that way. It’s better to reduce the response."

Looking at getting a pair of Rythmik FV15 subwoofers to use as stands once I move everything to the basement, but apparently corner placement is bad even if I run things from a MiniDSP.

Also of Note: Speakers that go low enough not to "need" subwoofers... Just make me want subwoofers more because now I know what things can sounds like and sometimes want it louder when watching Interstellar.

In short, whoever said this doesn't know what he is talking about.

You perceive time smear in bass differently to other frequencies, and to effectively trap or modify the response with panels etc is a crazy idea in the real world as the waves are massive. I have used geddes methods with as many as 8 subs and it works very very well. Walking around the room lead to no perceivable change in bass response unless you put your ear up to a specific sub.

I would also describe the subjective 'sound' I achieved as what many would describe as 'tight' or 'fast'. At the time, this was not what I expected as I was in the 'sealed subs make tight bass' camp. I now know better. What caused this was the fact that sealed subs tend not to play the lowest frequencies (at least not without EQ).... which in my room, it turned out I had a room mode at!

 

[Duke]

Being an engineer, I am not much into smalltalk...

Not all engineers are good at distilling complex ideas down to concise statements.

 

[Lbstyling]

If I were to play test tones (such as these from Real Traps: https://realtraps.com/test-cd.htm ), which presumably do not have any harmonics, making them come from say the left speaker only, could I test this idea that below around 60Hz we can't detect the source?

Tried this.
You will likely detect its direction, especially at high SPL. But that's because the harmonics will be audiable, not because you can localise 60hz.

Solution? Use JBL 2242h subs. (Or 3 like me!)

Downside? You'll not be hiding this purchase from the missus...

Here's the port of one of the subs....

 

[Duke]

I would also describe the subjective 'sound' I achieved as what many would describe as 'tight' or 'fast'.

Agreed. "Smooth" bass = "fast" bass. It is the peaks which stick out like sore thumbs, in part because they take longer to decay into inaudibililty (and sounds which last longer are perceived as being louder).