So I did some measurements to understand what the DSP does. Place an SPL meter 6 inches at front and rear at mid midrange drivers. Used inter station white noise as a signal source and set the front side SPL to 0dB.
Measuring the rear drivers I got
setting
2 Near -2dB
1 Near 0dB
Off +2dB
1 Far +3dB approx
2 Far +5dB
The front and rear amps are not matched.
Front is a Forte Model 3 202 WPC 8 ohms 275 at 4 ohms
Rear is a Bryston 3B pro 100 WPC 8 ohms 200 at 4 ohms
Note the Bryston seems to have better sensitivity and appears to be louder for the same input.
I can't tell if there is any change made in the Bass responses as I would expect for room boundary bass compensation.
Perhaps the old speaker placement scenario is expected to be used to tame rear wall bass extenuation.
I wish Axiom would explain how the DSP works but the company seems too busy absorbing Bryston to care.
From the manual:
The location of your new Axiom LFR1100 speakers will significantly affect the sound quality you experience in your particular room so take care to position them correctly. Since the LFR1100 is an omnidirectional speaker with active drivers located in both the front and rear of the cabinet you will want to keep some space all around your LFR1100s. Around twelve inches (300mm) would be considered the neutral position. If you need to place them closer to or further from the wall or corner than this your DSP box does have a switch on the rear panel labeled “Boundary Compensation”. Around 8” (200mm) from the wall would be “Near 1” and 6” (150mm) or closer would be “Near 2”. If you are more than 24” (600mm) from the wall “Far 1” should be used and more than 48” (1200mm) would be “Far 2”. Th e “Boundary Compensation” switch can also be used to adjust for highly reflective or highly damped rooms. A highly reflective room may be more suited to the switch being in one of the “Near” positions and a highly damped room one of the “Far” positions. Ultimately it is best to try various positions in your room and go with what you feel delivers the best performance.
This pretty much covers how the boundary compensation switch should be used based on distance from the rear wall. There no other adjustments possible to the DSP and this is on purpose. The DSP programming has been exhaustively adjusted for optimal sound power response of the loudspeakers.
As craigsub has mentioned, you MUST have amplifiers with identical gain, otherwise the levels to the front and back sections of the LFR1100s will not be as intended and the interaction between the sections can certainly throw off correct imaging and soundstaging.
Thanks,
Andrew
