CEDIA presentation of 4 subwoofer configurations - Forum

My collegue recently attended a CEDIA talk given by Dr Floyd Toole which advocated aiming for 4 subwoofers in home theatre designs.

The aim was to create an opposing subwoofer displacement that would counteract a few of the primary room cancellations thus providing predictatable seating corridores away from the main room modes and eliminate some of the big modes.

For a typical rectangle theatre, a suggested layout was for 2 x subs on the front wall each placed 25% in from the left and right corners. The same layout applied for 2 x subs on the back wall.

The paper also recomended putting all of the subwoofers in phase with each other and all running at the same volume.

Some issues I see or would need to be adressed would include;
* Achieveing a tight phase relationship to the main speakers
*Creating new and less predeictable cancellations in audience seating zones by the timing issues between 4 subs in different locations.
*The impact on the attack of the system - a smearing of the subs
*Is there a potential impact on the mid-high frequencies when the room is preasurised to this level?
* "Sub to Audience" proximity issues where many typical home theatres lack the extra space at the back as you have between the front wall and the front row.
*The assumption that all walls will provide the same and predictable or equal boundary barriers.

Given that CEDIA have featured this as a Keynote talk and that many of your designers and installers are probably CEDIA members, I thought this is worth exploring from a Genelec perspective and what Genelec have observed with multiple subwoofer placements such as this.