if existing amps have a builtin crossover is it necessary to use an electronic one?

amps:
mb quart 4 channel
alpine mono amp - 40hz

crossover
power acoustik c30-xr
lowest point 50hz

would it act as a double filter of some sort. improving audio quality?

 

What do you mean by "electronic one"? Might help if you post the actual model #'s for the amps, what you plan on doing, etc...

 

Post factory amp, the signals are crossed.

Pre factory amp, they are not.

I assume you're asking about something to do channel summing?

 

I plan on taking the signals from the factory amp output( front, rear, sub ) and connect them to the LC8i inputs.

From the LC8i, it will connect to a crossover, then to my amps... OR from the LC8i to the amps.

 

Your setup works fine for alot of people. Depends on how anal you are I guess.
Post amp signals aren't full range, but crossed pretty close to where most people would do it anyways with a sealed sub and descent comps.

 

The post-amp is crossed approximately:

80hz and up on the fronts
80 to 3K hz on the rears
30ish to 80hz on the sub

If those meet your needs, then you don't need the second crossover.

Usually, the more stuff that you add, the more that the signal degrades. The exception to this is high-quality stuff like a high-end processor.

 

If your using the LC8i it has internal signal summing if you choose to use it. You can create full range signals from the crossed over signals from the factory amp or you can leave it crossed over at the factory amps slopes. You have a couple routes you can go with using the LC8i. Good product btw.

 

If you go pre-amp...might want to make sure your amp accepts a 'balanced' signal, otherwise you'll get noise. The Audiocontrol units don't accept balanced I don't believe.

 

I know the audiocontrol matrix does, and it converts to unbalanced if you want. Did you ever figure out your noise?

 

its funny you mention the matrix.
I actually ordered the LC8i thinking it was a "line driver"
to late now to exchange it.
I guess when my factory amp dies I'll get the matrix to replace the factory amp and LC8i.

 

If your using the LC8i there is no reason the get the signal pre-amp. The LC8i was designed for vehicle sound systems just like those that are in the TL. The LC8i does have a line driver in it btw.

Audio Control LC8i:

Now if your factory amp dies yes you may have to go in the direction of splicing RCA's to the pre-amp side and running it thru a Matrix. But before going that route I would suggest try using your LC8i before spending more money, you may be able to get away with still using it.

Almost every processor made by Audio Control has the ability of taking in balanced signals. I know for sure all of there digital processors (DQL-8, DQXS, DQT, DQX, DQS) do and so does The Epicenter, Overdrive Plus, and The Matrix. Other great thing about audio control units is they all have ground isolation selectors built in to help reduce/remove ground loop noise.