Multiple Subwoofers Summary: 

This experiment examined the use of 4 half-wall subwoofer placement compared to a single corner mountedsubwoofer at three listening positions used in a real room in a real system with listening positions chosen for optimal performance at higher frequencies.

 This room has a 13’ by 23’ footprint with a vaulted 18’ foot ceiling. It has an open foyer and staircase so the room has an acoustical space of 7600 ft3. There are fairly large openings at both sides of one short wall. Lots of partial walls and canted ceiling surfaces deliver nicely distributed room modes at 17,34,53,73 and 120 Hz.

Frequency Response measurements for all conditions were taken with a DRA Labs MLSSA Analyzer and are available upon request. SPL measurements were recorded with an Audio Control 3050a SLM. This interim report summarizes the Maximum SPL attainable with a 10% distortion limit with 4 subwoofers placed at ½ wall spacing on each of the four primary walls compared to a single identical unit placed in the corner of the listening room with a measurement and distortion sensing microphone placed at each of the three primary listening seats located 42-inches from the rear wall at a microphone height of 41-inches.  

Measurements show that ½ wall placement of multiple low frequency systems produce severe cost and minor output penalties along with a small improvement of bandwidth uniformity over the three primary listening positions (along a single row of seats.)

Static frequency response measurements (MLSSA) show that 4 subwoofers do not appear to deliver significant response smoothing benefits at any listening position. The SPL measurements show that a single corner subwoofer tends to display a depression at 40 Hz  but also delivers 4-5 dB more SPL below that frequency compared to 4 distributed subwoofers. This work confirms an earlier study where a single corner subwoofer in a 2136 ft3 room outperformed by a significant margin 5 subwoofer distributed in a 5-channel array.

Continuing work on sweet spot listening with DVD-A and SACD multichannel music systems also needs to be finished and this experiment should also be replicated in a 20’ by 15’ by 8’ room (found to be most common North American room size in a 250 listening room survey conducted by another manufacturer) helping ensure wide consumer application. 

dB SPL 25-62 Hz @ 10% distortion: 3 Seat Average

Single subwoofer supplies more SPL at every frequency except 40 Hz.

dB SPL 25-62 Hz @ 10% distortion: Left Seat Average

Single corner subwoofer has more dynamic capability at every frequency

dB SPL 25-62 Hz @ 10% distortion: Center (Money) Seat Average

Single subwoofer better everywhere except 40 Hz.

dB SPL 25-62 Hz @ 10% distortion: Right Seat Average

Only seat that four subwoofers best a single corner unit overall.

(Note single corner has more SPL capability at 25-32 Hz)

Raw Data: dB SPL @ 10% distortion by Listening Seat

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