Klipsch speakers and bi-amping

[Brinkman]

In the archives here at AK there have been threads regarding the use of an active crossover to bi-amp Klipsch speakers.

The pair I have are Klipsch Fortes. According to posts I've read, the lowpass filter slope of the crossover is 6dB/octave, and the bandpass and highpass slopes are 12dB/octave. In fact, I was surprised to discover how much sound the woofer contributes to what one hears from these speakers.

I recently purchased the two-way active crossover kit from audio-kits.com. In it's stock configuration it has eight 2nd order Linkwitz-Riley filters cascaded to form four 4th order (24dB/octave) L-R filters with Sallen-Key topology. However the designer, Ron Shaw, sent me modifications I could perform to change the kit to exactly match the crossover design of the Fortes. In other words, my active crossover now matches what the Klipsch engineers found to be the best "voicing" for the Forte.

A further benefit is that my woofer driver can now be fed directly by a 4-ohm output tap (solid state) and my mid/highs get fed off the 8-ohm taps of my modified ST70. The active crossover introduced no color and has an inaudible noise floor. And as was expected, my bass response and low-end presence has been vastly improved.

If any of you are interested in bi-amping but are having trouble finding an active crossover that matches your speaker crossovers, this is a very tweakable kit and Ron Shaw is incredibly accommodating. And if you have Fortes, he can provide you a crossover that is as close to the passive design as it gets.

Best.

 

[Mazeppa]

I've been back into audio for about a year now. Just purchased my first set of Klipsch (Quartet) a whole week ago, and am quickly becoming a fan.

Have been interesed in testing the claimed advantages of biamping for awhile, and these Quartets may just get me to it. I'm considering a set up similar to yours SS/woofer, tube/mid & high.

I hope you won't mind fielding a couple of noob questions.
1. Did you provide a copy of the factory passive crossover schematic to Mr. Shaw for matching the active crossover to your Forte's?
2. Is it neccesary to modify the passive crossover in any way other than to split the woofer section away for addition of the second set of amp output connections?
3. Is the woofer section of the passive crossover needed in this configuration (using the active crossover)?
4. Can you still "uni-amp" your Forte's by bonding the speaker inputs together? Channel to channel, of course.
5. How did you get into the cabinet? Pull both the passive and the woofer?

I have searched long and diligently and unsuccessfully for a Quartet schematic, can anybody help me out? Ive seen a lot of listings for schematics ID'd alphanumerically but don't know which, if any of those are for the Quartet. I might've been able to figure some of this out if I had a schematic. Still need to get one before I go much further.

Any and all assistance will be greatly appreciated.

 

[BECtoo]

Quartet schematic.

Bob Crites

 

[Coytee]

if you have Fortes, he can provide you a crossover that is as close to the passive design as it gets.

This is nothing more than a comment on some irony of your words.

My understanding is, Klipsch uses their chamber and an active crossover to get the best curve they can, out of a speaker. The goal then becomes trying to build a passive that mirrors the curve of the active, as much as possible.

In other words, the passive is designed to equal the active as contrasted with designing an active to equal a passive.

:thmbsp:

FWIW, I also use an active with some of my Klipsch so in no way am I trying to be critical, just wanted to make that point.

 

[skywave-rider]

Brinkman,
The price is really good, did you get the "turbo" IC upgrade?
Have you compared to the more expensive Marchand kits?
http://www.marchandelec.com/xm9.html
When you say the active x-o matches the passive, is he matching the x-o point, filter slopes and type, or what? If he could do all that, it's impressive.

I've been interested in upgrading my active and would certainly consider this option.

The Fortes are three way, yes? So you are using part of the Klipsch band pass and the high pass filter? Or is the kit expanded for tri-amp, 3-way operation. I did not see a 3 way on his site. Sorry if I missed it.

In the archives here at AK there have been threads regarding the use of an active crossover to bi-amp Klipsch speakers.

The pair I have are Klipsch Fortes. According to posts I've read, the lowpass filter slope of the crossover is 6dB/octave, and the bandpass and highpass slopes are 12dB/octave. In fact, I was surprised to discover how much sound the woofer contributes to what one hears from these speakers.

I recently purchased the two-way active crossover kit from audio-kits.com. In it's stock configuration it has eight 2nd order Linkwitz-Riley filters cascaded to form four 4th order (24dB/octave) L-R filters with Sallen-Key topology. However the designer, Ron Shaw, sent me modifications I could perform to change the kit to exactly match the crossover design of the Fortes. In other words, my active crossover now matches what the Klipsch engineers found to be the best "voicing" for the Forte.

A further benefit is that my woofer driver can now be fed directly by a 4-ohm output tap (solid state) and my mid/highs get fed off the 8-ohm taps of my modified ST70. The active crossover introduced no color and has an inaudible noise floor. And as was expected, my bass response and low-end presence has been vastly improved.

If any of you are interested in bi-amping but are having trouble finding an active crossover that matches your speaker crossovers, this is a very tweakable kit and Ron Shaw is incredibly accommodating. And if you have Fortes, he can provide you a crossover that is as close to the passive design as it gets.

Best.

 

[Mazeppa]

Quartet schematic.

Bob Crites

My thanks to BECtoo and Mr Crites for the schematic

 

[Brinkman]

Brinkman,
The price is really good, did you get the "turbo" IC upgrade?

When you say the active x-o matches the passive, is he matching the x-o point, filter slopes and type, or what? If he could do all that, it's impressive.


The Fortes are three way, yes? So you are using part of the Klipsch band pass and the high pass filter? Or is the kit expanded for tri-amp, 3-way operation. I did not see a 3 way on his site. Sorry if I missed it.

Sorry for the late reply; school has been stealing my "internet time". To answer your questions:

1) I did get the turbo IC upgrades. I'd imagine the upgrade is audible on high efficiency speakers, but it also may be a bunch of hoo-ha. The increased noise floor from adding an extra component was honestly a bigger concern, and in that respect there's nothing to worry about. The board is clean and transparent and I haven't even housed it in a proper chassis!

2) Yes. I could have provided a schematic for him but I already knew all the pertinent info so I just furnished him with the crossover freqs, filter type, and slopes. I had already built the board at this point and was hoping to correct what I heard as an acoustic "hole" where the woofer/squawker slopes cross over. It's apparent that in the Forte, the woofer extends up into the mids a bit to give the low-mids some body. With equal slopes steeper than the stock configuration, you lose the presence in this range.

After a couple days he emailed me with the circuit changes I needed to make.

3) The bi-amping scenario I have arrived at is addressing deficiencies in my modified ST-70 amplifier rather than an experiment in Klipsch modification. In short, the bass output was not as robust and extended as it was with the solid-state amps I grew up with. The active crossover was a way for me to re-direct some output wattage from my ST-70 and have a dedicated SS amp for the woofers. The ST-70 is thus fed into the mid-high passive crossover.

As a note, I have subsequently installed the K&K Audio ST-70 modification board into my amp and the sound is remarkable. There's a separate ST-70 driver thread in the Tube Forums here were I will describe it in more detail. After I roll in some KT-88s I may remove the crossover to see how well this new driver can push the low-end frequencies.

Best.

 

[skywave-rider]

Thanks for your thorough description.
An interesting,worthwhile experiment in all respects.
:thmbsp: