One thing I find interesting from a historical perspective is the thread on AudioRoundTable.com
where Geddes begins to talk about his "random" subwoofer placement. This is virtually the same conversation in a discussionboard thread that Earl Geddes, Duke LeJeune and I had at the Great Plains Audiofest in 2005. In fact, it's the same three of us and a few other ART regulars having this discussion online. So you can really see where Earl was coming from, and how his approach evolved.
Since then, Earl has refined his approach from just saying "place them randomly" to saying "one in the corner, one at a wall midpoint and one in a random spot" to having people do a measurement sweep before installing each sub. But in the end, his approach is still basically the same, but with measurements to help dial it in. That's always a good practice.
Back when we first started talking, I expressed interest in the Welti multisub method. I was starting to form my "flanking sub" approach as an adjunct to the Welti method, because I felt that the upper midbass and lower midrange needed to be addressed too. This is something the flanking sub approach deals with that really isn't addressed in any other multisub configuration, so I felt it should be included alongside the Welti approach.
Earl said he thought Welti mis-assessed the situation entirely by not studying random arrangements. He though that since all of Welti's configurations were symmetrical, an important piece of the puzzle was overlooked. I reminded him that this wasn't really the case - that Welti had
used a random structure of subs as a baseline, that it was sort of the target, but it was also a huge number of subs. Welti was seeking the performance of a massive number of randomly placed subs using a small number of subs placed in an organized and repeatable fashion.
The conversations always ended up sort of spiraling around with no real conclusions except that we all agreed once you get past four subs, it doesn't really matter where you put them. This was an important take-away for me.
Another important take-away for me was that everyone was looking at response below 100Hz, and nobody even considered the (more important, IMO) 100-200Hz transition region, where not only room modes live but also self-interference from nearest boundaries. That's why I always recommend flanking subs as first priority, and more distant distrubted subs to smooth lower frequency modes, if they are troublesome. Flanking subs will smooth the range down to about 60Hz to 80Hz, and that gets the most objectionable modes as well as the lower midrange notch(es) from nearest-boundary self-interference. More distant subs can be setup per Welti or Geddes, I don't care, nor should anyone else because as we all agree, once you get to four subs, it doesn't matter where you put them.
But anyway, for historical perspective, see the "Sub Placement" thread on AudioRoundTable.com
. To reach it, go to the Pi Speakers FAQ
, and click on the "Room modes, multisubs and flanking subs" thread. Go to the end and click on the "Geddes configuration" link. There you'll find the original Geddes setup instructions. You'll also find "Welti configuration" and flanking sub setup instructions.