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Manolo47 20th December 2011 01:31 PM

REL subwoofer + high pass filter in main speakers
Has onyone tried this, implementing a REL SW with the main speakers crossed over with a HP filter at say, 80 or 100 hz. There are advantages in not having the main spekaers running full range. I know the REL design does not call for thsi, but then, one could not declare the main speakers -if small- as full range in HT setup.

Wha' DIYa know? 14th November 2012 03:26 PM

I found this old, and apparently un answered question. I'm curious about the same thing with my Rythmik subs.

I used the subs built in high pass to "filter" the music to the main amp and speakers. It threw a wet blanket over the sound.

Next, i fed the power amp directly from the pre amp, fidelity restored!

I wonder if there is a high pass option, to relieve my amp and full rangers from struggling with low frequencies, that doesn't compromise sound quality.

Manolo47 14th November 2012 08:02 PM

REL SW and Rythmik
I solved my original question. If one uses REL SW's one has to use the main speakers full range, without a high pass filter. I tried it with a REL SW and it did not work well.

To answer your question in relation to the Rhythmik SW I can answer it from my experience with my Vandersteen SW which is designed to work with a high pass filter set at 80 hz in the main preamp.

With the Rhythmik, you can also do that, but you need to implement the high level connection to the SW, that is, connect the Rhythmik high level inputs to the main amplifier speaker outputs. Believe me, it should work much better than the low level -or line level - rca connection-

But you need a high pass first order filter for your main speakers which you accomplish by installing a series cap in the preamp output. The value of that cap depends on the input impedance of your main amp and the crossover frequency you select. It should be between 60 to 80 hz.

The advantage of dinf it this way is that the SW amp receives the information of the main amp nad thus reproduces the bass with the same sonic qualities as if the main speakers and amp would produce it.

If your input main amp impedance is 100K ohms and you select 80 hz, the value of that cap would be 0.02 uf. If it is in the 50k range it would double that or 0.04 uf

Hope this helps Try it.

Wha' DIYa know? 14th November 2012 08:42 PM

Hi Manolo,

Thanks so much for this "input", ha ha hah.

I might be confused about what you're suggesting. If I put a high pass cap between pre-amp and power amp, then feed the subwoofers with speaker level output (from that power amp), then the subwoofers aren't getting bass frequency information -- it's being rolled off after the pre-amp output. Right?

If I feed both power amp and subwoofers from different pre-amp output RCA's (I have two outputs), then I can high pass the audio going to the main amp/speakers, and feed the Subs with the unfiltered full spectrum audio to do their thing with (low pass, then amplify, then drive the sub speakers).

I must have something wrong here, since you've got yours working well.

Thanks, Brenton

Wha' DIYa know? 14th November 2012 08:45 PM

One problem I'm seeing with driving the Rythmiks with the pre-amp is that I've got some hummmmmm.

sreten 14th November 2012 09:46 PM


If you first order high pass the input of a power amplifier at 80 to 110Hz,
and then feed the sub from the anplifer output you need an inverse 1st
order bass boost somewhere to restore the correct low bass balance.

Could be built into the lead feeding the sub as a passive circuit.

rgds, sreten.

Wha' DIYa know? 15th November 2012 01:50 AM

Thanks Sreten, that makes perfect sense!

DrDyna 15th November 2012 09:42 AM


Originally Posted by Wha' DIYa know? (
One problem I'm seeing with driving the Rythmiks with the pre-amp is that I've got some hummmmmm.

Try lifting the ground on the power cord.

Wha' DIYa know? 15th November 2012 03:00 PM

Thanks for that tip, Doc.

youknowyou 3rd June 2017 04:25 AM

just tried it myself, you can see the thread here

Experimenting with High-Pass for P3ESR + KEF LS50 with REL T5i | Steve Hoffman Music Forums
Ive played more with the sub setting and managed to fill in more the 60 to 110 hz dip, but the dip is a room mode. happy with the measurements and more importantly how it sounds.

I wouldnt want to cross the mains too high since the rel have to fight, so to speak, the highpass since its still connected via high level input.

ive crossed the P3ESR 1st order roll off at 100hz. -3db point is around 100hz, -10db at 30hz.

result is much cleaner low bass and sub bass, the p3esr sounds more open and dynamic and less compressed.

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