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Old 14th November 2006, 05:19 PM   #1
GeorgeJ is offline GeorgeJ  Canada
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Default ELS passive equalizer circuit

It is not clear to me how the passive midrange equalizer circuit described in Roger Sanders book (pg 168)would be wired into an existing system.

I am using JRM panels www.justrealmusic.com/content/model-2_111.htm
crossed at around 350hz to a woofer, and I would like to try the equalizer circuit.

Thank you

GeorgeJ
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Old 17th November 2006, 09:08 AM   #2
Calvin is offline Calvin  Germany
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Hi,

C1 and R1 form a highpass/subsonic-filter with f=1/(2pi*R1*C1) (here ~10Hz)
R2, R3 and C4 form kind of a stepped lowpass-filter with following freqs:
1st: f1=1/(2pi*[R2||R3]*C4) --R2 and R3 parallel R||=R2*R3/(R2+R3)
2nd: f2= 1/(2pi*R2*C2)
f1, f2 ~500Hz and 3.2kHz with the shown dimension.
The resistors R2, R3 and R4 set the gain of the filter.

Below 10Hz the signal volume rises with rising freq up to a level of ~+17dB
Between 10Hz and 500Hz gain is constant and set by: A=1+(R2+R3)/R4 (6.9times ~17dB)
Between 500Hz and 3.2kHz the gain drops with 6dB/oct.
Above 3.2kHz R3 is shorted by C4 and the gain becomes: A=1+R2/R4 (1.9times ~5.7dB) and remains there constant with rising freq.

jauu
Calvin
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Old 17th November 2006, 09:03 PM   #3
GeorgeJ is offline GeorgeJ  Canada
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Quote:
Originally posted by Calvin
Hi,

C1 and R1 form a highpass/subsonic-filter with f=1/(2pi*R1*C1) (here ~10Hz)
R2, R3 and C4 form kind of a stepped lowpass-filter with following freqs:
1st: f1=1/(2pi*[R2||R3]*C4) --R2 and R3 parallel R||=R2*R3/(R2+R3)
2nd: f2= 1/(2pi*R2*C2)
f1, f2 ~500Hz and 3.2kHz with the shown dimension.
The resistors R2, R3 and R4 set the gain of the filter.

Below 10Hz the signal volume rises with rising freq up to a level of ~+17dB
Between 10Hz and 500Hz gain is constant and set by: A=1+(R2+R3)/R4 (6.9times ~17dB)
Between 500Hz and 3.2kHz the gain drops with 6dB/oct.
Above 3.2kHz R3 is shorted by C4 and the gain becomes: A=1+R2/R4 (1.9times ~5.7dB) and remains there constant with rising freq.

jauu
Calvin

Thanks Calvin, I appreciate your answer. I apologize if it is evident, but I need to know where in the system this xo is physically placed.

After the pre-amp? After the amp before the speaker xo or after the existing speaker xo?

George
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Old 17th November 2006, 10:20 PM   #4
Calvin is offline Calvin  Germany
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Hi,

after the xo when its an active one. You just want to eq in the HP-part of the xo!
IŽd then omit C1 and add an resistor instead to lower the input volume to the equalizer. Otherwise with +17dB the signal might become too high.
Between Pre and Power-amp if the yo is a passive one. In this case it might be necessary to lower C1 in value, such that there is not much lift left for the bass, but just for the panel (it might not work well with an passive speaker anyhow)

jauu
Calvin
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Old 22nd November 2006, 06:33 PM   #5
GeorgeJ is offline GeorgeJ  Canada
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Thanks Calvin.

I had forgotten that the equalizer was really meant for full range panels.

Regards,

GeorgeJ
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