calculating Q for spl due to RLC notch filter
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 21st August 2009, 12:30 AM #1 Dave R   diyAudio Member     Join Date: Aug 2006 calculating Q for spl due to RLC notch filter Is there such a thing as a "Q" for the notch in spl caused by a parallel RLC filter, and if so is it calculated similar to the Q for the notch in the impedance? I can't seem to find this defined anywhere. Numbers below are for example only. freq atten (Hz) (dB) ---- ------ 6184 -2.00 7039 -2.83 9016 -4.00 << (notch center freq) 11548 -2.83 13145 -2.00 Is it simply calculated at the point where the attenuation is .707 x SPL@ notch? In this case where atten = 4.00 x .707 = 2.83, I'd be inclined to calculate Qspl as follows: Qspl = [9016/(11548-7039)] = 2.0 What I'm leading toward is trying to size up the RLC values for a notch filter, when the Q for spl can be obtained from measured data. Dave R the 200% Norske __________________ - Dave R the 200% Norske
 21st August 2009, 12:58 AM #2 infinia   diyAudio Member     Join Date: May 2005 Location: SoCal Q is defined for any second order system response ie any RLC. So you would measure it the same way for a speaker driver or a sallen key filter stage. Q = central freq /half power BW Hint use 3 dB away from central point not 0.707 If meas. using voltage then 0.707 is correct. Vp=1 V then 20log*1/0.707= 3 dB __________________ . . Last edited by infinia; 21st August 2009 at 01:20 AM.
Ron E
diyAudio Member

Join Date: Jun 2002
Location: USA, MN
Quote:
 Originally Posted by Dave R Is there such a thing as a "Q" for the notch in spl caused by a parallel RLC filter, and if so is it calculated similar to the Q for the notch in the impedance?
See attached. Have fun.
Attached Files
 NOTCH.zip (23.0 KB, 33 views)
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 22nd August 2009, 01:56 PM #4 Dave R   diyAudio Member     Join Date: Aug 2006 Thanks Ron. Nice little spreadsheet. __________________ - Dave R the 200% Norske

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