Digital Sound Processor: Tuning According To Room Conditions

Every room has a resonance. The resonance is caused by fixtures or simply by the room itself. Since usually the room is bordered by hard walls, these walls represent resonance nodes for the sound particle velocity. This results in the following resonance for your listening room:

Room Resonance	Closed room resonance Please enter decimal separator as "."
Room dimensions	Height in m:	Width in m:	Depth in m:


Major modes 1st order^*):	Hz	Hz	Hz
Major modes 2nd order^*):	Hz	Hz	Hz
Minor modes 1st order^*):	Hz	Hz	Hz
Monor modes order 2a^*):	Hz	Hz	Hz
Monor modes order^2b*):	Hz	Hz	Hz
Calculation: f_res = c/2 * sqrt( (l/lx)^2 + (m/mx)^2 + (n/nx)^2), with l,m,n = 0,1,2... where major modes: over one wall, minor modes: over 2 walls, not considered: all 3 walls and c as velocity of sound: 344 m/s
© Lautsprechershop Daniel Gattig GmbH, 2002. All rights reserved - Warranty excluded

If there is perhaps more than just one resonance, and all of them close to one another (in the example above in a room of 4.5 x 5 x 2.5 metres, there are multiples of frequencies around 35 Hz and 80 Hz), it is obvious to soften these frequencies.

That's exactly what a digital sound processor (DSP) does. Sitronik or Audaphon also supplies a software package to adjust the frequency response in an easy way:

eingestellter Frequenzgang
Picture 1: tuned frequency response for a room of 5 x 4.5 x 2.5 m.

In picture 1 there is a flap for the subwoofer (there is also one for the left and the right amplifier channel, if you want to use them). The adjustments were chosen as follows:

HP 20 Hz, 24 dB/Oct, protecting the subwoofer from frequencies below 20 Hz (subsonic filter)
LP 80 Hz, 12 dB/Oct, slow 12 dB roll-off to satellite at 80 Hz.
Delay 0 cm 0 Phase - since the subwoofer is lined up with the satellites.
Level 3 dB, the basic volume should be somewhat higher (please refer to the following).
EQ1 35Hz/Q=2/-3dB the first equaliser reduces the volume for 35 Hz (first dip from the left)
EQ2 80Hz/Q=1,5/-3dB the first equaliser reduces the volume for 80 Hz, volume already declining
EQ3 100Hz/Q=1/-1dB removes further boost in the range of 100 Hz.

eingestellter Frequenzgang mit Q=1 und Q=5

The value Q describes how steep a cut-off is.
A small value Q=1 (the green curve pictured left)
bends the frequency response gently,
a Q=5 (the blue curve pictured left) generates a steep curve.

Using the three equalisers with nine parameters, all required frequency responses up to +/-6dB may be selected. Experience shows that bigger deviations are most the time not useful (also filters that are too steep), since the overall sound is affected.

It's, however, a lot of fun to reduce the resonance of satellite speakers like the full range Ciare CH 250 or a satellite speaker that overdoes it.

Using the buttons E and S, adjustments may be transferred to or from the module.

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