adjust gain in bi-amp setup

[skudra]

I have an Altec 803B horn with an unobtanium compression driver that has a sensitivity of about 108db, and a JBL 2235 driver in an Altec A7 box that is about 96db with the short horn-loading taken into account.
At present I'm using one tube amp to drive both highs and lows with a passive crossover. The horn is padded down using resistors and capacitors.
We are probably going to bi-amp the system using something like a QSC amp for the woofer and a tube amp for the highs. I would then need to compensate for the differnces in the gain of the two amps. How would I do this without changing the impedence at the speaker and to also get the adjustment to be as transparent as possible.

[hjames]

Okay, if you are going to biAmp you need some kind of crossover to split your incoming signal into low-band and high-band outputs. I used to use a JBL M552 as a crossover, but upgraded to an Ashly XR1001 active crossover to determine the crossover point - and each leg of the circuit has gain controls to control how much I send to my 2 power amps - I use a JBL/UREI 6230 for my high end and a JBL/UREI 6260 for the woofers.

The amps correct directly to the driver (well, except for some protection for your horn driver) -
your old passives come out of the system ...

See this post from Bo
http://audioheritage.org/vbulletin/showpost.php?p=20273&postcount=1
and the thread that follows ...
http://audioheritage.org/vbulletin/showthread.php?t=2316&highlight=Ashly&page=10


I have an Altec 803B horn with an unobtanium compression driver that has a sensitivity of about 108db, and a JBL 2235 driver in an Altec A7 box that is about 96db with the short horn-loading taken into account.
At present I'm using one tube amp to drive both highs and lows with a passive crossover. The horn is padded down using resistors and capacitors.
We are probably going to bi-amp the system using something like a QSC amp for the woofer and a tube amp for the highs. I would then need to compensate for the differnces in the gain of the two amps. How would I do this without changing the impedence at the speaker and to also get the adjustment to be as transparent as possible.

http://audioheritage.org/vbulletin/attachment.php?attachmentid=31709&stc=1&d=1206142264

[Loren42]

I have an Altec 803B horn with an unobtanium compression driver that has a sensitivity of about 108db, and a JBL 2235 driver in an Altec A7 box that is about 96db with the short horn-loading taken into account.
At present I'm using one tube amp to drive both highs and lows with a passive crossover. The horn is padded down using resistors and capacitors.
We are probably going to bi-amp the system using something like a QSC amp for the woofer and a tube amp for the highs. I would then need to compensate for the differnces in the gain of the two amps. How would I do this without changing the impedence at the speaker and to also get the adjustment to be as transparent as possible.

Since you are using two different types of amps you need to verify that the phase for both amps is coherent. That is, the outputs of both amps have the same phase relationship with each other.

Some amps invert the signal, some do not.

The easiest way is using an oscilloscope, but maybe some here has an idea how to test for phase of each amp.

As the previous post stated, you must remove the passive crossover before you bi-amp and stick a 50 µF cap or so in series with the horn to protect it.

Your active crossover should have level output controls to adjust the levels of all signals.

[clubman]

The easiest way is using an oscilloscope, but maybe some here has an idea how to test for phase of each amp.



Hook one amp to the left Low Freq driver and the other amp to the right Low Freq driver and listen for a phase differance.