Stereo Subs - Do they need to be identical?

Funnily enough the link I gave above came from a manufacturer...

The link also shows up to a 20 DB SPL hole in the bass in some cases due to quarter wave cancellation and a succession of harmonically related cancellations further up in frequency (a comb filter)...

Furthermore one might wonder why studios often soffit mount large full range speakers ?

These same studios often leave small (less than full range) near fields out far into the room on the meter bridge.

Perhaps there is some logic ....perhaps is is all just aesthetics...

Here is another speaker designer's comments on the reasons for soffit mounting speakers.

Read and draw your own conclusions. Dismiss the science if you like...

In some cases, the quarter-wave cancellation from the bounce off the rear wall can be taken advantage of to tame a peak.

As for asymmetrical placement, here's a link to a brief informal paper by one of the leading researchers in psychoacoustics, Earl Geddes. He's comparing four subs in corners vs four subs asymmetrical, so it's not exactly what's being discussed here, but might be worth taking a look at as it illustrates one of the advantages of asymmetrical placement. The thing to look at is how much the peaks and valleys are reduced for each of the three listening positions in the asymmetrical case (represented by different color lines):

http://www.gedlee.com/downloads/sub%20study%20.pdf

Duke

Here is the link to calculate the wall bounce from reflections. If you use stereo subs then you can assume the same thing will happen up to a couple of octaves above the crossover (when the effect starts to become negligible compared to the many other room effects/anomalies)

Yes science (theory) and experimentation are necessary to get you to where you need to go. Theory is a good starting place. Mounting into the wall (soffit) is an option and can be tried but you also have to factor into the equation the room length and how this placement will specifically fit into that. My point is that theory is just a starting point and that when you really get into this particular project you have to do your own listening and your own measurements because the variables in any given case are so numerous as to render any given prediction based soley on theory ( even very sound theory) woefully insufficient. - Jim

Dear Outlier and friends: IMHO it is better to have to identical subs it does not matters which is the crossover frequency.

There are IMHO many subjects on the subs integration and maybe many things to know about, here are some links that can be interesting to read:

http://www.soundstage.com/maxdb/maxdb061999.htm
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&27&4#27
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&31&4#31
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&75&4#75
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&84&4#84
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&158&4#158
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&183&4#183
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&196&4#196

There are to much to " explore " on the subs subject ( a complex one ) and there are a lot of misunderstood about, IMHO I think that till today the last word on subs is/are not writing yet.

Regards and enjoy the music.
Raul.