Active crossovers

Matching two amps is trivial.

There is no matching to be done, other than level setting. Just about every electronic crossover has level adjustments for every band.

Regardless of the "gain" of an amp, when you increase the input by 3dB, the output goes up 3dB. So, all you have to do is to put a level into amp 2 that when compared at the speaker output using pink noise gives the *same* level on your SPL meter as does amp 1. Of course, your ear will be the final arbiter of the precisely perfect relative levels.

If your electronic xover does not have level controls, and your amp does not either, you can either build a fixed pad into a small box - after measuring the dB difference with no pad. Or you can buy an after market in-line adjustable attenuator box to put in line with the amp that is "too loud" to reduce its level. Alternately, you can drill some holes into your amp and put a small rotary switch with MF resistors and make your own attenuator built in,or just put a decent pot there... I do that all the time on Phase Linear 400s that are used as subwoofer amps from time to time (on the front panel of the PL400, to match the PL700).

All done.

_-_-bear

Yes, having an amp with adjustable volume control gains, like the Parasounds (God bless em for doing so!!!), makes live way easier when you biamp!
Hey, also let me know which active crossover you are ending up with ultimately!!! I would like to know for my own references/uses! The only one I can recall having heard implemented is the Krell, and am currious to hear how the Bryston, or others, sounds!

If you use the Krell KBX, it has gain adjustment for each Highs and Lows, making the need for adjustable volume on the amp totally unnecessary. In fact, the less in the signal path the better, so unless I could bypass the amps volume control, I would prefer one without it.

Richard

OK, I posted this in the wrong thread, hehe! Hope I didn't cause too many blank stares!

I asked Albert the best way to bianp the VR's, here's his info:

Hello, again,
for facilitating active biamping of the speakers, does anything need to be
done to the speaker itself?

No. The internal circuitry divides the signal between the two amplifiers, so you don't need to change the speakers or buy an electronic crossover. Just connect the preamp or CD player to both amps with a "Y" connector and interconnects. Just make sure that both amps have a similar input sensitivity, so that they play at the same volume level. The output power has nothing to do with this, we use an 8 watt SET amp on the mid/tweeter unit and a 200 watt solid state amp on the woofers with complete integration! Albert

Let's be clear, these are LEVEL controls, NOT "gain" controls!!

We call them "gain" but 99% of the time they set the output level of a fixed gain circuit. To change the gain of a typical solid state circuit you need to change the feedback resistor. Few circuits (for good reasons) actually permit you to adjust the gain of a stage directly.

It is standard practice to build in "excess gain" so that you can set a level control midway - in fact the volume control only LOWERs the level down from maximum.

On power amps 99.9% of all level controls are right at the input of the amp, before any active circuitry. Again they only serve to lower the input level to the front end.

There are some exceptions, like the Crown Macro Techs which if I recall actually has a neat circuit that adjusts gain, not level, in order to *set the level* then sent on to the fixed gain remainder of the amp...

Again "gain" is not an accurate description of this control, although we all tend to use the term!

_-_-bear