'Low Pass Filter' Options - Post Amp (Passive)? - AVS Forum
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post #1 of 8 Old 01-26-2013, 08:03 PM - Thread Starter
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I plan on powering a sub with a receiver that does not have any low pass crossover built in.

Since the receiver I am using is only a two channel receiver (connected via component output from TV), which is also powering a pair of tower speakers, I have no ability to use an active crossover; so I'm looking at a low pass filter that I can stick after the receiver and between the sub.


I ran across this, which is close to my needs (I only need something to handle around 75watts RMS; 130-180hz @ 4ohms / 250-300hz @8 ohm crossover - unsure if I will be running 8 ohm or bridging down to 4 ohm, depending what sounds best):
http://www.ebay.com/itm/Treble-Blocker-Low-Pass-Crossover-130hz-4-ohm-SubWoofer-/290420156833?pt=US_Signal_Processors&hash=item439e63e9a1

I'm going to assume those 'treble blockers' are just coils. Are there any calculators where I can make my own coils or buy a coil for a lot cheaper than $20 from maybe RadioShack? Seems a bit much.

Or does anyone have any other ideas for me? I'm looking for a fairly inexpensive solution to get my sub online.

Thanks for all the help! I will be active on responding to this thread.
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post #2 of 8 Old 01-27-2013, 09:04 AM
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Originally Posted by WoogityBoogity View Post

I plan on powering a sub with a receiver that does not have any low pass crossover built in.
Just use the speaker level inputs on the sub, and wire the mains to the outs on the sub for them, which are capacitor high passed.

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post #3 of 8 Old 01-27-2013, 04:08 PM - Thread Starter
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Originally Posted by Bill Fitzmaurice View Post

Just use the speaker level inputs on the sub, and wire the mains to the outs on the sub for them, which are capacitor high passed.
Thanks for the response. I understand what you are saying, but unfortunately it's not a powered sub. No high level inputs or anything of such. The receiver is (will be) actually driving the sub.
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post #4 of 8 Old 01-27-2013, 04:22 PM
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Originally Posted by WoogityBoogity View Post

Thanks for the response. I understand what you are saying, but unfortunately it's not a powered sub. No high level inputs or anything of such. The receiver is (will be) actually driving the sub.
Get a plate amp. You can buy one for the cost of the components for a 100Hz crossover. The stuff you linked to is junk, don't even think about using that.

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post #5 of 8 Old 01-28-2013, 08:09 PM
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what kind of sub are you powering from a receiver. I agree with Bill Fitzmaurice, in most circumstances a receiver is not the proper tool for driving a sub. What is the ohm rating on the sub? Your cheaper older AVR (assuming here) is likely only rated for 8ohm, while your sub may be 4ohm. Good way to burn up the receiver, and still sound bad before it pops. if you actually have a decent sub get something like the Inuke DSP 1000 which will allow you to do all things DSP and can be had for around $250 most of the time.

If you are strictly looking at passive crossover and are DEAD set on using the receiver - here are some options
http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Daps&field-keywords=fmod+low+pass

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post #6 of 8 Old 01-30-2013, 01:11 PM
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how do you even power the sub off the receiver?
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post #7 of 8 Old 01-30-2013, 03:01 PM
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Originally Posted by WagBoss View Post

how do you even power the sub off the receiver?
The same way you'd power any speakers. But to do so requires a passive crossover between the sub and mains, and the cost of one worth having runs over $100 for the parts alone. You can buy one pre-made for maybe half that, but it won't work very well.

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post #8 of 8 Old 01-30-2013, 03:22 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

The same way you'd power any speakers. But to do so requires a passive crossover between the sub and mains, and the cost of one worth having runs over $100 for the parts alone. You can buy one pre-made for maybe half that, but it won't work very well.

oops, I misread his post, I thought he was already powering the subwoofer, but it had no lpf. I was confused how a passive subwoofer was being powered by a receiver if it did not have high level inputs.
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