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Discussion Starter #1
I have a pretty low-buck setup but I did pick up a A/D/S/ P640 amp fairly cheap and am attempting to use it but it's throwing me for a loop.

I have two active crossovers in the car, a Coustic XM-5 and Audiocontrol 4XS. When I have the XM-5 hooked up to the P640 amp it reacts completely differently than anything I've ever worked with. The gain control and crossover control at the crossover DOES NOT AFFECT the output of the amp whatsoever. I can flip, turn, squeeze, slap, and pop everything on the crossover and I get no change in output. It's as if the RCA hookup is full-range even though it is going through my XM-5 first. Have I just not figured out the signal routing of the P640 amp? The on-board processing on this amp is pretty high-tech, at least for me.

As a side question, this amp allows the summed signal of two stereo pairs of RCAs to drive the final stage of the amp. How does this summing function work with two signals that are already processed ('crossed')? Lets say for example, I have a 3k high-pass summed with a 150-4k bandpass, what is the output? Is it 150-20k+ and if so, is there any dips/peaks around the crossover frequencies?

Thanks,
Travis
 

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I'm surprised you need the 4xs with a P640. Seems redundant.

The P640 has about a million settings for how it routes the input. You probably just have one set wrong. Plug things in one RCA at a time so you know what's going to what.

You don't want to filter and then sum. I don't see what you'd be trying to accomplish there...
 

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Discussion Starter #3
Correct me if I'm wrong, but I always thought that if some is good more is better...

If I have 18db slopes, then what will it hurt to have a 30db slope? I offset them enough so it doesn't reduce output too much at the crossover points, but I've always thought it was worth a few more cheap RCA cables to stagger the crossovers and get a steeper slope. Am I completely wrong in this thinking?

I'd still appreciate some input on the amp's built-in summing network.

Thanks,
Travis
 

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If im not mistaken you can run active off those older ads amps. I wanted one but never found one at a good price. So why filter and filter and filter your signal? Just more chances for something to act up.

Directed Electronics - Owners Guides
Use that link for the manual if you dont have it.
 

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Discussion Starter #5
I do agree that it is more chances for something to go awry, but If everything is in working order I figured that the steeper slopes would be of some benefit.

Thank you very much for the manual site by the way.
 

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Steeper slopes can be useful. Depends on the application. I can get up to 120dB/oct slopes on my setup, but I choose 24dB/oct for most of the xover points and 12dB/oct for one. More isn't necessarily better. It's just more. :)

If you don't have noise issues in your setup, then the additional units probably aren't hurting anything.

As for the summing, I'm not really sure what you're asking. It's just a summing circuit. It literally adds the signals. Are you asking how it works?
 

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Discussion Starter #7
Well, what if two signals are already filtered? What is the result when they are added together? What I wonder about really is how the signals are affected at the crossover points.
 

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They add. If they have different crossover points, you get the bandwidth from both. Depending on the exact location of the crossover points and gain of the two filters, there might be a hump at the crossover point. Depending on the slope, you could have phase issues at the crossover point.

I don't see why it would ever be beneficial to do this.
 

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I would just get rid of your extra crossover(s) and use the amp. I have the 8 channel version of your amp- it's working quite well only using the amp's adjustments to run my active setup.
 

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Discussion Starter #10 (Edited)
I have decided to run the mids and tweets at 12db slopes only processed through the ADS amp. But, I want to run my stereo midbass processed through my 4XS first since otherwise I will not have a bandpass for it. This way I can run my door speakers from 125/150-350/400 Hz. Would this be a terrible idea? It would be equivalent to a 3rd order high-pass and a 5th order low-pass on my door drivers. Any advice on setting these crossover points. The mid would have two 2nd order filters and the tweet a 2nd order highpass filter. How would you expect these to blend?
 

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Id say if your going to use the 4xs to crossover then dont use the amp to do it. Just set the amp to full or whatever with no crossover.
 

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I thought you could run mids and lows bandpassed + tweets highpassed with the 4xs? If so, then the 4xs can do all of it, no?
 

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Discussion Starter #13 (Edited)
My setup requires several bandpass stages, that's the problem. I have subs, low midbass, high midbass, midrange, and tweets. I currently have the 4XS set in 4-way with the below crossover points:

highs: 4k+ Hz
mid: 150-4k Hz
midbass: 60-150 Hz
subs: 27-90 Hz

But that doesn't cover everything I need, that's why I used a XM-5 crossover with this unit at one time but that was before I had the 6-channel amp. From the 4XS I need the midrange split so I can get my front midrange and front midbass (as opposed to my low frequency rear midbass).

I know my setup sounds a little crazy but I appreciate any input.
 
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