Singular as subwoofer: low pass filter design (Singular)
The project is to use a dedicated Tripath based amp for a Singular with Fostex FW208N woofer. The singular will be used as subwoofer in the range of 35hz~200hz.
The idea is to modify the low pass filter present at the output of the Tripath amp to get a frequency cut at 200hz.
The low pass filter in the T-amp is a second order 107kHz LC filter with a L=10uH and C=0.22uF. The T-amp has too a Zobel RC filter with R=6.2ohm/2W and
C=0.22uF.
Using some calculators on line I got a 2nd order 200hz LC filter with L=9mH and C=70uF. I couldn't calculate the Zobel filter because there is not the "Le" (bobbin inductance?) in Fostex datasheet.
I've to confess I don't understand much about filters, can you help?
P.S.
T-amps work better with copper foil coils used in Xovers.
Singular as subwoofer: low pass filter design
by Bert 
, Friday, March 16, 2007, 15:07 (6241 days ago) @ Giovanni
Hi Giovanni,
I've to confess I don't understand much about filters, can you help?
Why don't you create that filter in front of the T-amp? This way the amp is not bothered with the impedance behaviour of the driver, any filter likes to see a flat impedance to work optimally...
Ciao,
Bert
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BD-Design - Only the Best!
Singular as subwoofer: low pass filter design
"In front" means before the amp? (anyway the t-amp would need the LP filter to recover audio from the switching signal).
Any circuit for a suitable filter for this driver?
Here is a link to give you an idea...
by Bert , Friday, March 16, 2007, 15:31 (6241 days ago) @ Giovanni
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
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BD-Design - Only the Best!
Here is a link to give you an idea...
Thanks for the link.
But I've no fun if I don't try new things.
For a line level LP filter I have another option: I have two DACs and an EMU1212M inside the PC, with a huge DSP and 2 separate digital outputs. So I could do filtering inside the PC and send different digitally filtered signals to the 2 dacs.
The problem is that I have still to learn how to syncronize the two dacs to a common clock.
The other option to use the amp output filter as LPF is funny because there are no components to add, only to mod. I think nobody tried this, that's why it is attractive 
Knock yourself out...
by Bert , Friday, March 16, 2007, 18:03 (6241 days ago) @ Giovanni
Hi Giovanni,
The other option to use the amp output filter as LPF is funny because
there are no components to add, only to mod. I think nobody tried this,
that's why it is attractive
Then you have to play around with that and try to have the Fostex driver's impedance flat from about 1 octave below the crossover frequency and up...
This way the filter works as it should but still, you might want to cross sooner to EQ a rising response if present.
Enjoy!
Bert
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BD-Design - Only the Best!