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Old 23rd December 2008, 06:52 PM   #1
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Default HighPass for main spkrs, to marry HSU subwfr

Hsu Research sells a $100 highpass filter for the main R/L line-level output to the main amp/ speakers, to "relieve them" of their low freq duty, allowing the sub to take over in the low range.
I would like to DIY a filter myself, and want to know my options.
Passive ?
Active ?

There are several circuits on the web, and I understand their basic theory of operation, but I don't understand how to properly match such circuits in terms of the existing impedance(s) in my system.

Here are some details:

Main Speakers:
d'Appolito 2-way, ported
3.5 kHz internal x-over (24db Link/Riley)
89 dB sens.
Flat down to 40 kHz
bi-wireable

Hsu Sub
X-over --LowPass only, 30-90 Hz @24 dB/oct.
0/180* phase switch
X-over "defeat" switch

Power Amp
51k input imp.

DIY preamp
63 ohms output imp.
---------------------------
BTW....I've incorporated a separate mono output for a subwoofer, summed from the main stereo outs (see schem (I am not using the series caps though that are shown.)

Mono Sum
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Old 23rd December 2008, 07:34 PM   #2
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Default Re: HighPass for main spkrs, to marry HSU subwfr

Quote:
Originally posted by redrabbit
Hsu Research sells a $100 highpass filter for the main R/L line-level output to the main amp/ speakers, to "relieve them" of their low freq duty, allowing the sub to take over in the low range.
I would like to DIY a filter myself, and want to know my options.
Passive ?
Active ?
How fast would you like to relieve them? The simpliest and least obtrusive would be a single cap on the input of the power amp driving the mains (1st order, 6dB/octave).

Click the image to open in full size.

where R1 = 51k.

dave
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Old 23rd December 2008, 08:09 PM   #3
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OK, I'll admit it, get ready to roll your eyes......the filter equation is killing me...
is the 51k (R1) inputed as 51,000 (ohms), or just "51" (K ohms)?

C=
2 x 3.1416 (pi) x 60 (hz) x ????? / 1

and the result (C) is in....pf, uF, ??
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Old 23rd December 2008, 08:37 PM   #4
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5.2 x 10e-8 F = 5.2 x 10e-2 uF = 0.05 uF

dave
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Old 24th December 2008, 05:33 AM   #5
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So this would be one channel ?

Click the image to open in full size.

Would a second one in series, become 12 dB/oct ?


=RR=
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Old 24th December 2008, 06:00 AM   #6
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Where the 51k is the input R already in the amp.

You could put another section in front of this, ideally 0.5 uF + 5k, but now you have only a 5k load for the pre-amp, so it better have lots of grunt and a really low output impedance. If it doesn't you mau need to add a buffer.

What kind of amp & pre-amp?

dave
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Old 24th December 2008, 10:21 AM   #7
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Quote:
Originally posted by planet10


What kind of amp & pre-amp?

dave
Preamp = opamp + buffer LH0063 ...with 62.5 ohm high wattage resistors on output for protection. No output blocking cap.
http://i5.photobucket.com/albums/y17...t/DSCN2921.jpg

Amp(s) = Muse 175 monoblocks (solid-state).

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Old 24th December 2008, 10:30 AM   #8
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Not trying to rain on anyones parade but what good is a 6db per octave filter? Something in the line of a 24db per octave would be in order in MHO.
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Old 24th December 2008, 10:35 AM   #9
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I agree. I'm open to all suggestions.
I believe at this point, we're talking about the simplest solutions and basic circuits first.

I have my eye on this circuit....
http://sound.westhost.com/project09.htm

....but I'll consider a passive approach as well.
I don't mind building and listening to different methods.

=RR=
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Old 24th December 2008, 12:09 PM   #10
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Sealing the ports and putting two of those passive filters in series with poles where the rolloff of the sealed speakers are would leave you with 24dB/octave slopes that would hopefully be fairly easy to integrate with the sub.
As dave said, ideally the first filter would use 5k, but you could probably get away with 10k if your pre struggles
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