Will this Bi-amp Xover idea work?

[chris ma]

Hello Folks,

A normal commercial 2 way speaker would normally has a set of low pass and high pass filters in the box right? Now assuming I have four mono blocks of power amps and just one pre-amp. But this pre-amp has 2 sets of L/R RCA outputs terminals that output the same signals to four interconnects which connects to the four power amps.

Now in order to retain the correct crossover design for the speakers, can I remove the appropriate sections of the speaker crossover and put each in between the power amp and the pre-amp as a passive xover without modification?

That means I will have the following connections

Pre-amp----A.Left channel------>Lowpass------>tweeter
B.Left channel------>Highpass------>mid/bass
A.Right channel----->Lowpass------>tweeter
B.Right channel----->Highpass----->mid/bass

Now the raw speakers would be connect to the power amps directly with no passive parts. Do I still need something to protect the tweeters?


Thanks in advance..
Chris

[till]

Now the raw speakers would be connect to the power amps directly with no passive parts. Do I still need something to protect the tweeters?

a capacitor

[paulb]

Originally posted by chris ma
... can I remove the appropriate sections of the speaker crossover and put each in between the power amp and the pre-amp as a passive xover without modification?

The speaker crossovers are designed specifically for the loads represented by the speaker drivers, and for a nearly zero source impedance (the amp output). If you change the source and load impedance by wiring them between your preamp and power amps, they will not have the same frequency characteristics.
Using any type of passive crossover between the preamp and amp will result in a gain loss; you'll have to turn up the volume more to achieve the same volume and may limit your maximum power output.

[mikewu99]

Now in order to retain the correct crossover design for the speakers, can I remove the appropriate sections of the speaker crossover and put each in between the power amp and the pre-amp as a passive xover without modification?

No.

The crossover is a passive filter - its response is dependent on the impedance of the load (the speaker). Any other impedance (such as the input impedance of your power amp) will alter the frequency response beyond recognition.

You could terminate the crossover with an impedance similar to the speaker, but your preamp will never be able to drive it.

To exactly mimic your existing crossover, you will need to redesign the crossover to work with the higher impedances found between the preamp and the power amp.

[Jason Hubbard]

You should protect the tweeter from DC thumps, etc that your amplifier might put out with a capacitor as previously suggested - i use a small cluster of polyproylene capacitors totalling about 100uf.

There are better ways to split the frequency bands than to simply use the old x-over components between the pre-amp and power amps - you should consider even a low cost in-car active x-over as a better solution (the passive x-over in the speakers is compromised by the amount of power it is required to handle).

[jonclancy]

Maybe a little off topic, but I am just about to build one of Rod Elliot's L-R 24 db/octave active crossovers. Might be of use to you. Boards and all the know-how are available at:

sound.westhost.com

Cheers

Jon