I have the Eclipse cd5030, it has a seperate Xover for the front,rear & sub.

Lets say I set the Xover on the HU to 80hz for a HP Xover and set the Xover on the external amp to lets say...60hz HP.

What happens in this situation, will the Xover be used on the HU or the external amp? Or are they both combined or canceled out somehow.

I've always wanted to know this, Especially before I hook up my fronts to an amp

 

It just means you are sending a signal of 80hz and up to your amp. Setting the amp at a lower value than the HU does nothing. It's cutting out everything from 60hz and down but the HU isn't sending any signal lower than 80hz. So the amp's HP crossover really isn't doing any work when set at 60hz.

 

You answered my question, Thanks I will write this down.

 

more or less...remember there is a rate of cut off...6dB/oct, 12, 24 etc...depending on the rate of cut off you may still have a faily robust signal at 60hz even if you have the head set at 80 hz hp. for example; if your head unit is set at 6 db/oct at 80hz hp, that means that at 40hz(1 octave lower), the level is only 6 dB lower than it is at 80 hz. At 60hz, the level may be around 3dB lower, and the amps crossover if used, will take that 3db lower signal and add it's own filter which may be 6,12,18,24 etc.. dB/oct to it. What you actually end up with is a cumulative effect where the 2 cross overs add together their slopes for a steeper cut off. This may be beneficial if that's what you want, but can also be detrimental as it may cause the sound to be "thinner" than you'd like as it removes to much of the lower frequencies and causes an imbalance in the sound. Keep in mind that when a crossover point is selected, there are 2 goals; one is to protect the speaker from reproducing tones it really shouldn't be playing by lowering the level of those frequencies, and the other is to blend the speaker's range with your subwoofer and tweeter to get smooth sound. Most 5.25 and 6.5 mids will play down to 50hz, but typically they're crossed a little higher so that by the time the 50 hz signal get to them, it generates less output but still combines with the sub to smooth out the response.

 

I did have it set to 63hz at a 12db oct, But I found the midbass didn't blend well enough with the tweeter so I put it up to 80hz and it seems to sound smoother.

Although, this is without an external amp so I am guessing I might have other options with an external.