Posted by Duke [ 63.87.108.130 ] on April 18, 2007 at 01:14:57:
In Reply to: Room modes and speaker placement posted by Wayne Parham on April 18, 2007 at 00:18:33:
Hi Wayne,
Thanks for taking the time and having the interest to go into such detail in your reply.
It's quite possible that a deliberate rather than pseudo-random subwoofer positioning pattern would prove to be the best. I haven't done any research into the subject on my own. I corresponded with Todd Welti some, and he didn't raise any objections to my proposed asymmetrical rather than symmetrical placement. If we get down into the specifics, I draw from Welti, Geddes, and Griesinger for my general placement recommendations - which I didn't go into detail about in my post. Griesinger advocates using two subs in stereo mode and placing them to the extreme left and right of the listening position, which maximizes the psychoacoustic impression of spaciousness ("envelopment" is the word he uses) by maximizing the interaural phase difference at the ears if you happen to have stereo low frequency information. So I like to position two of the subs to either side of the listening position (though somewhat asymmetrically), and the other two over at the main speaker end of the room (with possibly one but not both in a corner).
Griesinger and Geddes both emphasize the desirablity of de-correlating the bass; I don't recall whether Welti goes into that aspect. At midrange and treble frequencies the reverberant energy is highly de-correlated, so we don't have audible room-boundary-induced peaks and dips at those frequencies (though of course we have radiation-pattern-induced anomalies). My intention is to bring decorrelation down into the bass frequencies. Since with asymmetrical placement each individual sub's peak-and-dip pattern will be different, that would be one step closer to decorrelation than symmetrical placement would be.
I haven't done any modelling on my own at this point; I don't have the tools. Thanks for bringing CARA to my attention - I was aware of it but it had drifted off my radar screen. I'll give the US distributor a call tomorrow, as that sounds like something I should have in my toolbox.
At this point it's unlikely that the Swarm will make it to LSAF - I don't anticipate having the room in my car, and it would be redundant with the Jazz Modules because they go pretty low on their own. If the 95 dB satellites had worked out, I would have brought them plus the Swarm instead of the Jazz Modules. But the 86 dB Leela just isn't really in the spirit of LSAF, in my opinion, so it won't be there.
I wish I had a small stand-mount sealed-box pair of truncated Jazz Modules to go with the Swarm. Just typing out loud here... the problem is coming up with nice-looking boxes on such short notice. But if I did, we could play around with corner vs quasi-randomized placement after hours for fun one evening. Hmmmm. Does that sound interesting to you?
If it turns out that corner placement sounds best, I'll just change the words but still sing the same basic (multi-sub) tune. Kinda like singing "For He's a Jolly Good Fellow" to the tune of "The Bear went over the Mountain". Try it!
Duke
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