Yeah, or if the speakers are insanely bad loads, or maybe a few other cases, but generally (IMO) a huge waste of time, money and wire. I know - the above is far fetched and not the best solution, but I'm grasping at straws to try to justify something I'd never do.....

As always, YMMV. :-)

[This message has been edited by charlie (edited February 02, 2003).]

Charlie & Soundhound

Thanks for clearing the external crossover thing for me. When reading about bi-amping in the HT world I could never understand why someone would go through the trouble without a good external crossover (or several of them!)

Biamping with a "limited" crossover between the pre and power amps is a possibility.

By "limited" I mean just using a capacitor and resistor configured as a low or high pass filter at the input of the power amps and still using the passive crossover between the amp and the drivers.

For instance, lets say that the woofer crosses over at 500Hz to the midrange.

For the woofer amp, select a value of R and C to effect a lowpass to the input of the woofer amp at a couple (or three) octaves above 500Hz.

For the high range driver(s), select a value of R and C to effect a highpass to the input of the highrange amp a couple (or three) octaves below 500Hz.

The passive crossover between the amps and the drivers will still be the determining factor in regards to the spectra received by the drivers. The passive crossover at the amp's inputs will provide some out of band frequency limiting to the amps.

Depending on the power amp's input topologies, the high pass amp may need to have only a capacitor placed in series with the input. The low frequency amps may already have a capacitor, placed after a series resistor, to limit the ultrasonic response of the amp. Increasing the value of this capacitor to a suitably large value will then provide the low pass function for the low frequency driver amp.

This setup is a viable and more affordable alternative to having an active crossover between the pre and the power amps.

Paul

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the 1derful1

At that point why not do the same thing with an active crossover?

Using a single pole crossover such as this might pose a danger to the tweeter if it cannot handle the lower frequencies that would be passed by a 6db per octave crossover. If I were going to use the passive route (I actually do for my front center speaker, before the power amps) I would use a two pole inductor/capacitor/resistor filter which would yield a slope of 12db per octave, which is probably the same as that in the speaker's passive crossover.

In any event, I agree with Charlie on this however. It's a simple matter for me to fashon a line level LCR passive network, but It's probably beyond the capabilities of most HT hobbiests. I would recommend just going the full electronic crossover route. This would yield the benefit of being able to select the crossover point to achieve best response.

if you go to partexpress.com, they have on their site very informative materials on how to build your own 6, 12, or 18dB filter for various frequencies and either low pass, high pass, or band pass. I used them back in the day and found their kits the most effective for the price. A much lower cost alternative to active crossovers. Just another thought.

In my post I am still keeping the passive crossover between the amps and the speakers. The first order passive crossover between the pre and power amps was to remove some out-of-band material from being amplified by the amplifiers.

For someone who has the time and inclination, what I suggested can be a satifying and cost effective route.

I agree that an active crossover would be probably the "way to go" execept for those who can't or won't afford it.

Paul

Ask a simple question.....

I guess I should have know better then to ask a question like that on this board. Now my head is swimming...

So, to ask a stupid question...According to my manual, I just take the jumper off the back of the speaker posts. Run one amp for the low drivers, one set of amps for my high drivers. Do I need to wory about an external crossover? I thought that If my speakers were designed to be bi-wired/bi-amped that I was a fairly easy procedure to work with.

Is it, or am I completly missing something in what I've been reading in my manual (and that issue of What Hi-Fi? that I picked up).

Jason

[This message has been edited by fmcorps (edited February 07, 2003).]

You are right. All you need to do is to remove the jumper on the speaker and connect one amp to the highs (presumably the tube one) and one amp for the lows. You will need to "Y" the output of the processor to the input of the two amps. Remember, you may (probably will) have to balance the output of the two amps, but this can be done by ear, especially if you are fimiliar with the way the speakers should sound. Good Luck!

fmcorps, you might want to look here for Paradigm's thoughts on this subject- specifically Q12 and Q13. Best wishes.