[gmarks]

I stumbled on a video of REL's subwoofers, stacked 3 to a side, tuned by John Hunter. https://youtu.be/X0IgdeSheak

He tunes each subwoofer, doing one at a time, setting level and the low-pass crossover point differently for each, while listening right next to the sub for one thing for the lowest sub, another thing for the middle sub, and yet another for the top sub.

He uses a track from the movie Sneakers, saying this is the best way to do the fine tuning. https://youtu.be/X0IgdeSheak

I was thinking ok, ok, you have different subs at slightly different room locations, so maybe these adjustment make some kind of sense, although I could not grasp why there was a particular part of the sound assigned to bottom, middle, and top subs.

Then at the end (29:08) he talks about a collapsing sound field as each level is taken out of the stack, and I went into full "Voodoo!" mode.

I would appreciate reactions from others about what is going on here. BTW my current speakers are Danny's LS-9's, so I get the idea of a line source for the RELs (albeit pretty short) and the benefits of cone area.

[artur9]

Dunno about the collapsing sound field part.

The rest of it sounds a bit like Geddes' method for tuning multiple subwoofers to address room modes.
His method requires different positions, level, phase and crossover settings for each subwoofer in the room


https://forums.audioholics.com/forums/threads/geddes-approach-to-multi-sub-setup-instructional-video-by-matthew-poes.112553/

[Wayner]

Low frequencies are pretty obscure. Why anyone would need 6 of them is beyond me.....

[Hobbsmeerkat]

Noone needs six.
But want six? 

[gmarks]

About the Geddes' method, or Welti, or other discussions about room modes and adjustments - Artur9, I appreciate the link; a really good one. I have to admit that viewing your link reminded me that in the past I had been scared away by the complexity of placement around the room of multiple subs. I realize now that part of what at first glance got my attention about the REL setup is that it looked visually appealing, and then when I watched the whole thing my brain went ??????

I know some people have stacked Danny's open baffle subs - any comments on the acoustic principles and results of that versus the admittedly strong visual impact?

[NoahH]

Low frequencies are pretty obscure. Why anyone would need 6 of them is beyond me.....

A - the added height helps as you can localize subwoofers to an extend, partly from the higher frequencies they cover during roll-off and partly from the pressure. In general, speaker height is really a bigger deal than it is credited for in general.
B - settling time. If one sub has to move an inch to drive enough air, 6 only need to move 1/6th of an inch, so they can settle faster and generally be faster.

[Tyson]

A - the added height helps as you can localize subwoofers to an extend, partly from the higher frequencies they cover during roll-off and partly from the pressure. In general, speaker height is really a bigger deal than it is credited for in general.
B - settling time. If one sub has to move an inch to drive enough air, 6 only need to move 1/6th of an inch, so they can settle faster and generally be faster.

Also, as you stack the subs they start to also take on some of the characteristics of a line array (a very good thing).