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In Reply to: RE: Active Crossover Question for Maggie IIIas posted by neolith on February 10, 2012 at 13:48:58
I know this has been discussed before, but I did not pay much attention because I don't see any issues as far as gains. It seems to me that the level adjustment on the crossover is a gain adjustment. It that's correct, then you adjust it to match the gains of the high and low amps and nothing else to be concerned with as far as gain. Am I missing something? I'm enjoying my sound.
Follow Ups:
Basically, correct. Most units have gain controls to compensate when the amps have different gains. If you don't compensate then the balance of the amps will vary as you alter the input signal strength from the preamp.
Gain is not the same as sensitivity but the two are related and has nothing to do with the wpc. A lot of manufacturers report sensivity but may not specify gain. G = 20*log(Vo/Vi). Vo can be calculated from the power rating (maxium output before clipping) using P=IE and Ohm's law E=IR (or I=E/R) as SQRT(P*R) and Vi is the sensitivity, invariably reported at 8 ohms.
Since manufacturers often "cheat" when they report maximum power, the gains may still need some adjustment even if you have calculated the amps to have the same gain.
On the violin: "Heaven reward the man who first hit on the idea of sawing the innards of a cat with the tail of horse."
Edits: 02/11/12
After doing a bit more reading, I may go the MiniDSP route. Looks like it will do the correct crossover slopes, etc. I am just not sure how much of a benefit I will realize vs. when I tried using the biamp feature of my Pioneer Elite AV receiver. It has the capability to split the signal and create a flat response using the built-in mike. But I am assuming the crossover slopes and pts. the Pioneer is using aren't the factory specs that Magnepan recommends with my IIIas and that is the reason why I didn't hear any benefits.
Unfortunately Magnepan's suggestion of a 3rd order LP at 300 Hz and 2nd order at 500 Hz does not produce the same result as the OEM speaker level XO. I was not pleased with those value and went to a symmetric L-R at 400 Hz, and then 340 Hz. I then designed a custom crossover that simulates the original and had Phil Marchand send me the boards -- success.
On the violin: "Heaven reward the man who first hit on the idea of sawing the innards of a cat with the tail of horse."
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