Subsonic filter options - Page 3

Jimmy154 · 11th March 2010, 11:21 PM

Got confused again

Is the crossover down 3 db or 6 at f? Using these equations: Passive Line-Level Crossover

Jimmy154 · 12:33 AM

Looks like R2 (with the vertical line above it) has to be positive for the circuit to function properly, but it is recommended that I use 5K-10K resistor for the 12 db/octave slope. All values above 1K ohm for R1 will cause R2 (with the vertical line above it) to be negative, since my amp input impedance is 10K ohm. What do I do? Here is the link to the formulas: Passive Line-Level Crossover

Looks like my only option is to choose a R1 resistor lower than 1K ohm, correct?

Jimmy154 · 12th March 2010, 02:05 PM

Can I use the amp input impedance as the R2 resistance without using a resistor?

Values would be:

R1=1k ohm
R2 or amp's input impedance=10k ohm
C1=1.06e-5 F
C2=1.06e-6 F

or should I use?:

R1=500 ohm
R2=5k ohm
C1=2.12e-5 F
C2=2.12e-6 F
R2(with line over the 2)=10k ohm

Or should I use other values? It's a 12 db/octave high pass filter at 15 Hz.

Jimmy154 · 13th March 2010, 11:18 PM

I can see I have ostracized myself from the diyaudio community, possibly due to my signature.

I'm gonna have to go it alone. Wish me luck friends (and enemies).

Artie · 15th March 2010, 11:36 PM

Which BA amp do you, (or your friend), have? Don't the Bostons already have a built-in x-over / filter?

Jimmy154 · 12:41 AM

I have the GT-28. It does not have a subsonic filter. Although I do believe it might come with some sort of optional subwoofer control module that I do not have.

I'm going with these values:

R1=1k ohm
R2 or amp's input impedance only=10k ohm
C1=11.6 uF
C2=1.1 uF

Hopefully, as I understand it, this will give me -6 db at 14.5 Hz.

Artie · 16th March 2010, 01:06 AM

Those numbers look good, except that you'll have -12db at your "f" value. But thats good in my book. Try it and see.

Jimmy154 · 16th March 2010, 01:40 AM

Hmm . . . I was hoping for -6 db at 14.5 because my friend's subwoofers are tuned to 18 Hz roughly. Is it a problem that I used only the amp's input impedance as the R2 resistance or impedance?

I thought 12 db/octave Linkwitz-Riley were down 6 db at "f":

http://www.bcae1.com/images/gifs/xo2ndlra.gif

Artie · 16th March 2010, 09:19 AM

Quote:

Originally Posted by Jimmy154

Is it a problem that I used only the amp's input impedance as the R2 resistance or impedance?

I'm not sure. Someone more knowledgeable than me will have to field that one. It sounds feasible though.

Quote:

Originally Posted by Jimmy154

I thought 12 db/octave Linkwitz-Riley were down 6 db at "f":

I was just going by the fact that its called a 12db/octave curve. It may well start at -6db.

11th March 2010, 11:21 PM	#21
Jimmy154 diyAudio Member Join Date: Jun 2002 Location: Los Angeles	Got confused again Is the crossover down 3 db or 6 at f? Using these equations: Passive Line-Level Crossover __________________ We do not allow political statements or conjecture to be made on these forums.---the diyAudio moderation team

12th March 2010, 12:09 AM	#22
Jimmy154 diyAudio Member Join Date: Jun 2002 Location: Los Angeles	Looks like R2 (with the vertical line above it) has to be positive for the circuit to function properly, but it is recommended that I use 5K-10K resistor for the 12 db/octave slope. All values above 1K ohm for R1 will cause R2 (with the vertical line above it) to be negative, since my amp input impedance is 10K ohm. What do I do? Here is the link to the formulas: Passive Line-Level Crossover Looks like my only option is to choose a R1 resistor lower than 1K ohm, correct? __________________ We do not allow political statements or conjecture to be made on these forums.---the diyAudio moderation team Last edited by Jimmy154; 12th March 2010 at 12:33 AM.

12th March 2010, 02:05 PM	#23
Jimmy154 diyAudio Member Join Date: Jun 2002 Location: Los Angeles	Can I use the amp input impedance as the R2 resistance without using a resistor? Values would be: R1=1k ohm R2 or amp's input impedance=10k ohm C1=1.06e-5 F C2=1.06e-6 F or should I use?: R1=500 ohm R2=5k ohm C1=2.12e-5 F C2=2.12e-6 F R2(with line over the 2)=10k ohm Or should I use other values? It's a 12 db/octave high pass filter at 15 Hz. __________________ We do not allow political statements or conjecture to be made on these forums.---the diyAudio moderation team

13th March 2010, 11:18 PM	#24
Jimmy154 diyAudio Member Join Date: Jun 2002 Location: Los Angeles	I can see I have ostracized myself from the diyaudio community, possibly due to my signature. I'm gonna have to go it alone. Wish me luck friends (and enemies). __________________ We do not allow political statements or conjecture to be made on these forums.---the diyAudio moderation team

16th March 2010, 12:35 AM	#26
Jimmy154 diyAudio Member Join Date: Jun 2002 Location: Los Angeles	I have the GT-28. It does not have a subsonic filter. Although I do believe it might come with some sort of optional subwoofer control module that I do not have. I'm going with these values: R1=1k ohm R2 or amp's input impedance only=10k ohm C1=11.6 uF C2=1.1 uF Hopefully, as I understand it, this will give me -6 db at 14.5 Hz. __________________ We do not allow political statements or conjecture to be made on these forums.---the diyAudio moderation team Last edited by Jimmy154; 16th March 2010 at 12:41 AM.


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15th March 2010, 11:36 PM	#25
Artie diyAudio Member Join Date: Jul 2007	Which BA amp do you, (or your friend), have? Don't the Bostons already have a built-in x-over / filter?

16th March 2010, 01:06 AM	#27
Artie diyAudio Member Join Date: Jul 2007	Those numbers look good, except that you'll have -12db at your "f" value. But thats good in my book. Try it and see.

16th March 2010, 01:40 AM	#28
Jimmy154 diyAudio Member Join Date: Jun 2002 Location: Los Angeles	Hmm . . . I was hoping for -6 db at 14.5 because my friend's subwoofers are tuned to 18 Hz roughly. Is it a problem that I used only the amp's input impedance as the R2 resistance or impedance? I thought 12 db/octave Linkwitz-Riley were down 6 db at "f": http://www.bcae1.com/images/gifs/xo2ndlra.gif __________________ We do not allow political statements or conjecture to be made on these forums.---the diyAudio moderation team

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