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

[youngho]

I am confused how mid to 1/4 away from the wall proves better than corners when more SBIR will be presented? Closer to wall brings SBIR higher frequency then you use some absorbers to tame then EQ. Is there something else at play with mid to 1/4 away from the wall approach that goes against the norm of the abovementioned geneal consensus or is this method for people who don't use absorbers?

Yes, the something else at play is the concept of standing waves or modes. It will be helpful if you read this: https://www.harman.com/documents/LoudspeakersandRoomsPt3_0.pdf

 

[Flaesh]

Square passive radiator?

Just a hole cut into the box instead of factory pipes.

 

[jhaider]

Welti shows…

Simulations and analysis of a drastically simplified room, with no doors, windows, openings, fireplaces, etc.

This work was a milestone as a proof of concept to show that multiple subwoofers can markedly reduce spatial bass variation. However, you can’t make generalized predictions of placement in a real room based on a model of something else entirely.

 

[DRNNOO]

That is not corner loading.

lol that definitely is corner loading....

execute it in real life and then take a picture lol... Its strategically placed in the corner... My subwoofer box if any bigger wouldn't fit. 32" is the desired 1/4 Width and my boxes are 32" wide... perfect fit... in the corner. Anything closer than 1/4 W or L is pretty much the corner. If its not in the corner what is it? Near the corner? The only corner being literally the 90 degree meeting of the surfaces? Be for real, "Corner Loading" is a whole concept in its own that involves using the walls of the Corner as a waveguide... you are trying to argue that at 1/4 W or L dimension, that, the walls are not being used to load the bass response? 1/4 - W/L spacing is the optimal corner loading.

 

[Propheticus]

You will be surprised of the audible differences experimenting with the hight when installing a subwoofer - the differences are as big as moving the subs L - R in the room.

My own experience in a room with 240 cm distance from floor to roof is that the bass quality will be best placing the subwoofer about 60 cm above the floor on a stable bench. This is the same optimal height as my main loudspeakers on loudspeakerstands. Coincidence ?

Here is more interesting videos from this guy:

Makes sense, because some modes will exist due to the distance between ceiling and floor.

You can play around here Amroc room mode calculator and enter your room's dimensions and RT to get an idea where the modes are located.
In the linked config you can see a ceiling/floor mode at 63,5Hz
Of course it's a limited model only fitting rectangular rooms.

 

[Chromatischism]

lol that definitely is corner loading....

execute it in real life and then take a picture lol... Its strategically placed in the corner... My subwoofer box if any bigger wouldn't fit. 32" is the desired 1/4 Width and my boxes are 32" wide... perfect fit... in the corner. Anything closer than 1/4 W or L is pretty much the corner. If its not in the corner what is it? Near the corner? The only corner being literally the 90 degree meeting of the surfaces? Be for real, "Corner Loading" is a whole concept in its own that involves using the walls of the Corner as a waveguide... you are trying to argue that at 1/4 W or L dimension, that, the walls are not being used to load the bass response? 1/4 - W/L spacing is the optimal corner loading.

This is corner loading:



What you are showing is clearly labeled on the image: 1/4 room distance from the corners.

 

[DRNNOO]

The loading of the corner has more to do with acoustics than being literally physically square in the corner. Thats the part you are missing. We are literally loading the corner to acoustically resonate, similar to a waveguide, increasing resonance through directivity and potentially 1/4WL resonance... You are arguing the idea of where in the corner it is located to be called corner loading when corner loading isn't defined by its exact position in the corner, its the use of the corner purposely to amend the Frequency Response. Where in the corner obviously affects performance, having the subs output be 36" out from dead center corner, in my case, is just a detail of corner loading. The best way to load a corner, is obviously 1/4 dimensions of Width and or Length.

According to your strict definitely of corner loading the tower on the right and sub cannot both be "corner loaded" but I bet the response given by each will show heavy corner loading as opposed to the left which for this example we will assume, nothing but open space to the left of that speaker.

In effect, corner loading is essentially an Offset horn, how far out/in the offset, affects performance. I don't think it can be simplified more than that.

 

[Chromatischism]

The loading of the corner has more to do with acoustics than being literally physically square in the corner. Thats the part you are missing.

I am not missing anything. The response you get when you push the subs into the corners is different. The Welti study is very specific about that placement being 1/4 of the room dimensions and they do not call it corner loading. That could be 3-5 feet from the corners which will change the response.

But I think we both understand that.

 

[jhaider]

The Welti study is very specific about…

…not being a real room.

But I think we both understand that.

Do we?

 

[DRNNOO]

The response you get when you push the subs into the corners is different.

Its just a matter of where in the corner, and dead up against the two adjoining walls being the only place to be allowed to be called "corner loading" is very short sighted. In truth there are several distances away from the corner that are still loading the corner. It is the proximity to the corner that causes corner loading, and being dead within the corner instead of some calculated distance away from it, isn't a perquisite. Corner loading has a measurable effect, dead in the corner or 1/4 nearest boundary dimension both have a considerable amount of corner loading that will reflect in the measurement. Corner loading isn't an exact position it is the boundary reinforcement that reflects in the measurement. Strongest effects happen dead in the corner, and the most desirable effects happen 1/4 boundary dimension spacing, from the corner.

 

[Chromatischism]

And on that, I generally dislike subs not being against walls. SBIR is real, even for subs, and the further they get from boundaries, the more problems you'll see in the frequency response. That's been true at every house I've set up. Welti also shows that in their results of the mid-wall placement—they are literally against the walls.

But I think you're misinterpreting the study. Some important points:

Page 18:

Obviously, wall midpoint locations result in optimum room response, based on the std anyway. Not surprisingly, symmetrical configurations seem to work better than nonsymmetrical ones. Four subwoofers results in the most symmetrical configuration and the best results, but with significantly less (normalized) low frequency output than two subs.

Page 21:

This figure shows that there is no obvious trend towards lower Std, Max-Min or Max-Ave metrics when more subwoofers are used. In other words, there is no obvious benefit to using a large number of subs. Configurations 6 and 10-12 show the best results. Subwoofers at each wall midpoint (#11) shows the lowest Std, Max-Min and MaxAve. Subwoofers in all four corners (#10) is almost as good and shows a strong low frequency support. The LF generally goes down for larger numbers of subwoofers, possibly due to having more locations away from the corners.

Then he tries a non-centered layout, more typical of a real room.

Page 26:

Two and four subwoofers at the wall midpoints are still the best configurations overall.

Four subwoofers in the corners does not seem as advantageous as when the grid was centered. There is still little or no advantage to using a large number of subwoofers. LF factor still goes down for higher numbers of subwoofers.

And the conclusion on Page 28:

One subwoofer at each wall midpoint is the best in terms of Std, Max-ave and Max-min but does not support low frequencies particularly well. Two subwoofers, at opposing wall midpoints, performs very nearly as well as four at the midpoints and gives a much better LF factor. One subwoofer in each corner also has good low frequency support, but does not perform quite as well as one subwoofer at each wall midpoint, in terms of Std, Max-ave and Max-min. If cost and aesthetics are considered, subwoofers at 2 wall midpoints is preferred.

https://www.harman.com/documents/multsubs_0.pdf

 

[DRNNOO]

thats just it... He's only talking about the positions he tried... the 1/4 wall dimension spacing, that I am claiming is best... is not included in the charted data nor his comments. When he talks about what he thinks is best, he's talking of the positions he experimented with, 1/4 wall spacing is Not one those experiments.
As I explained before, here is the simulated response for 4 subwoofers at midpoint

And here is the simulated response for 1/4th spacing... its only simulated data because he never included this figure in the rest of the test... can you read these charts... Do you not see that this response is better than the one above?

 

[Chromatischism]

thats just it... He's only talking about the positions he tried... the 1/4 wall dimension spacing, that I am claiming is best

Are you? I thought you were claiming corners were best?

When he talks about what he thinks is best, he's talking of the positions he experimented with, 1/4 wall spacing is Not one those experiments.

Both corners and different variations of 1/4 placements were tested as seen on pages 19, 20, and 23.

In which the results show that numbers 6 and 11 were best, with number 6 having the best low frequency output. This is what I've been using in my rooms, for two reasons. First, after moving subs all over the place, front+rear measures the best. Second, it happens that it is the most convenient placement because it's much easier to keep the subs out of walking spaces, unlike subs at the sides. Since my rooms tend to be narrow, you wouldn't be able to squeeze past side subs to sit down. One sub is next to my center speaker, with a wall-mounted OLED screen. The other is behind my seats along the wall.

I also haven't been able to accommodate corner placement in any room so far because up front, they would interfere with the speakers, and in the back, I may not actually have corners to use.

Most consistent response is from 6 and 11 (mid-walls).

As you brought up, he apparently does not test the theoretical double 1/4 distance setup from earlier, or whatever it should be called. Why, I have no idea. So since it is only theoretical, it is hard to say that it is the best.

In the conclusion, the best overall response was the four mid-wall locations, however using only front+rear is nearly as good, but with noticeably better low-frequency output. Here's where the corners come into play: when using all 4 corners, you get a response that is good, but not quite as good as the four mid-walls, but with better low-frequency output. Therefore if I had 2 subs, I would use front+rear. If I had 4, I would go with four corners, if you have the space. Often you end up with a door in the way, or the room is open, etc.

You're free to experiment with the close seat corner aka double 1/4 pounder placement though . But I don't think the locations are as practical as I'd be tripping over them.

 

[Propheticus]

It's right in the titles: the word "practical".
While 1/4 was theoretically best as simulated, apparently it was not tested because it was deemed impractical.
For most home situations I think that's absolutely the case.

 

[DRNNOO]

Its not impractical at all. 3d printing a waveguide is impractical and people do it every day. Flush mounting a set of monitors is impractical, people do it every day. 1/4spacing placement is the least impractical thing listed so far, either you want the FR performance or you don't. My subwoofer is 32x32x26.... 1/4 spacing for me is 32inches....fits perfectly, put sub in corner, turn 45 degrees, done. Not a small box, impractical for some, as we all know Hoffmann's Iron Law, I sacrificed size for sound quality. Either you want to do it or you don't.

Both corners and different variations of 1/4 placements were tested as seen on pages 19, 20, and 23.

So in other words you don;t know how to read the chart.
this is 1/4 spacing

this is the best configuration in the main test group, config 11

The smoother the line, the less deviations from a straight line, the better.... 1/4 spacing is obviously a much better response

 

[youngho]

Its not impractical at all. 3d printing a waveguide is impractical and people do it every day. Flush mounting a set of monitors is impractical, people do it every day. 1/4spacing placement is the least impractical thing listed so far, either you want the FR performance or you don't. My subwoofer is 32x32x26.... 1/4 spacing for me is 32inches....fits perfectly, put sub in corner, turn 45 degrees, done. Not a small box, impractical for some, as we all know Hoffmann's Iron Law, I sacrificed size for sound quality. Either you want to do it or you don't.

That's so interesting! So from the above, it sounds like your listening room is square 10.67'x10.67' with four subwoofers, only about 3' or so from the central listening position to each subwoofer driver. How do you have your speakers positioned? It would be great to see a setup diagram and some actual measurements!

 

[Propheticus]

Its not impractical at all.

1/4 of your wall's length is 32 inches? And then you filled it with four 32" by 32" subs? Sounds ... full
(because you keep referring to the 4 subwoofers at 1/4th spacing simulated plot.)

From your description / photo it seems you have 1 sub, does the simulated plot even apply then?

Also the distance is related to the centre line of the driver/voice coil. In your case that would mean (almost) flush to one wall and 16"away from the other wall.
On the photo you shared it doesn't look like there's anywhere near 16" between the side wall and your sub.

 

[RichB]

After consulting with the subwoofers, the optimal placement is to put the subwoofers in the center of the room and the people must sit in the corners.

- Rich

 

[Flaesh]

put the subwoofers in the center of the room and the people must sit in the corners

useful below second mode only:

 

[DRNNOO]

So from the above, it sounds like your listening room is square 10.67'x10.67' with four subwoofers,

I have a long rectangle, but I will eventually have 4 subs around me symmetrically

A good rule of thumb is like a good place to start or investigate. It doesn't appear that the rule of thumb is the result of combined response. Thats why I think its quarter wave related, the 1/4th division by distance relates to harmonics.

1/4 of your wall's length is 32 inches? And then you filled it with four 32" by 32" subs? Sounds ... full
(because you keep referring to the 4 subwoofers at 1/4th spacing simulated plot.)

I don't expect identical performance in my room, I just expect to see a connection between good mode performance and 1/4 spacing. Its probably a play upon quarter wave harmonics, but whatever the underlying cause "In this case, rule of thumb subwoofer placement worked well". Not my words but the conductor of the study. So its a rule of thumb not, the absolute rule. That picture is not my system, and I don't have 4 subs. I have 2 subs, and one is down here with me now. My subs are 32x32 by 26inches tall.