[EricB]

I installed two capacitors directly to the RCA jacks inside of my 4 watt amplifier.



The red wires that used to go to the center pin of the RCA input jacks were reattached to one leg of a capacitor. The other leg of the capacitor got soldered to the now empty RCA center pin.
 
I used an online calculator to find the capacitor value.
 
(http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php#answer1)
 
I entered the input impedance of 100K ohm of my amplifier (yours will likely be different) and my chosen crossover point of 70 Hz into the calculator and it determined the correct capacitor value of .0227uF.
 
Loudspeaker sensitivity is 93db and 8 ohms and this change took a-lot of the load off of the speakers and amplifier that goes to the subwoofers anyways.
 
I plan to add a second set of RCA jacks to the amp that are full range.
 
Eric

[Danny Richie]

Yep, doing that can be very effective.

Your whole signal is passing through that cap. So changes in the quality level of that cap can have a dramatic effect too.

Since the values are pretty small, it might be worth experimenting with higher quality caps as the small values are not too pricey.

[Glady86]

Does the Rythmic plate amps have RCA outputs to connect the high pass signal to the main amplification for the speakers? I cant tell from the picture on the website.
 
 

[Hobbsmeerkat]

Does the Rythmic plate amps have RCA outputs to connect the high pass signal to the main amplification for the speakers? I cant tell from the picture on the website.

The A370 PEQ amp does have it's own high-pass filter built in, but the quality isn't great.

[Glady86]

The A370 PEQ amp does have it's own high-pass filter built in, but the quality isn't great.

  Whats the best way to add a high pass crossover to the speakers then? Or just run them full range?

[Hobbsmeerkat]

Put them between the amp and preamp, with a Y-splitter before the high-pass so one leg is kept full range for the subs
You can also build a full-range output (bottom) into the filter itself like this:

[BGA]

One thing to remember is when you add a capacitor there will be a phase shift so you may have to adjust your subs phase to have it blend properly with your mains. I tried a few different frequencies with my X-Otica's and Double Troubles and found they still sound best full range and just low pass the subs.

[Tyson]

One thing to remember is when you add a capacitor there will be a phase shift so you may have to adjust your subs phase to have it blend properly with your mains. I tried a few different frequencies with my X-Otica's and Double Troubles and found they still sound best full range and just low pass the subs.

Interesting!  I also came back around to running my speakers full range and just bringing the subs in underneath them.  That’s what sounded best to me.

[jmimac351]

Ayre Acoustics will do a similar mod to the input boards for a few of their units that can accommodate the tweak.  I have a VX-5 Twenty amp with these boards, which high pass at 100Hz.  The input impedance for the Ayre units are 1M ohms, per leg - so the caps are very small.  I haven't tried them yet, but this is something they commonly supply for use with Vandersteen Audio speakers. I expect it to work very well.