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SUB amp with Built-in Active Crossover
SUB amp with Built-in Active Crossover
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Old 9th January 2004, 06:12 PM   #1
Killjoy99 is offline Killjoy99  United States
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Default SUB amp with Built-in Active Crossover

I am building Anthony Holtonís Symmetrical Amplifier as a mono Sub amp. I would like to incorporate an active crossover with a low pass Frequency knob and a Volume knob. Are there any simple designs or ways to do this? I was looking over the projects on ESP, specifically:

Project 84

Project 28

Project 08

Would any of these work for me? I would like the crossover to be mounted within the amps case and the knobs on the front. If there are any other designs that would work better I am open to everything.
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Old 9th January 2004, 09:25 PM   #2
Killjoy99 is offline Killjoy99  United States
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Default Denon Receiver as Crossover

Actually, I might as well ask this first. I will be using a Denon DTS receiver for my surround sound processing and as a preamp for the Power Sub Amp. Does anyone know if the signal coming from the Denon's Subwoofer out in the back is crossovered at all or is it the entire range. I read in the manual and it seems like subwoofer channel will only produce the LFE signal prgrammed on the DVD. Not sure if I'm way off base here, but I figured it was worth a try.

I guess what I am getting at is will I even need a crossover for the Sub Amplifier if the DVD signal first goes through my receiver and than to the power amp.

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Old 9th January 2004, 09:45 PM   #3
maylar is offline maylar  United States
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I can't comment on your particular receiver, as I have no clue - but the general arrangement for "sub out" channels on decks (at least car decks) is that they have some kind of lowpass filtering built in. You need to investigate the manual further...

As for lowpass circuits, 12 dB/Octave (2nd order) is usually adequate and there are common op-amp circuits for that:


I've been considering these myself, and it looks like to make them adjustable you need to replace 2 resistors with a ganged pot.

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Old 10th January 2004, 10:37 AM   #4
RobWells is offline RobWells  United Kingdom
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Most receivers have a 'size' setting for your speakers - large is full range, small routes the low bass to the subwoofer. On my receiver this is at 90Hz, others may differ.

I *think* most receivers do a hi pass at 12Db per octave, and a low pass at 24Db per octave. This to try and intergrate the main speakers natural roll off into a 24Db acoustical slope. - Try blocking your mains ports if you go this route. (turns a vented box into a sealed).

With a receiver you don't need a xo on the sub amp, but a phase knob could come in handy for blending the sub to the mains.


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