Active HU + amp crossover = Higher slope?

[mcsoul 10+ year member]

If I set my crossover for 2-way active on my headunit and then set it again on the amps, does this increase the effective slope. I think it does.

So lets say I use a 24db slope on the HU and activate another 24db on the amp; what will my effective slope be (assuming the same frequency on each). 48db?

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[James Bang 5,000+ posts]

no

 

[mcsoul 10+ year member]

It's got to be, if you feed an active crossover an attenuated signal, it will just further

attenuate it by an additional XXdb per octave. It does not know or care that the signal

has already been crossed over.

 

[audioholic 5,000+ posts]

More or less yes, xover slopes stack. But not quite as linear as you think. The slope/point of the second xover will be slightly affected by the first one.

 

[dragnix 5,000+ posts]

just use one

 

[I Like Waffle]

I was wondering the same thing sortof, sometimes you run into a situation where youre forced to use a crossover 2 times. Example, most pioneer HUs force you to pick a crossover frequency for the subs at the HU, where as some amps dont allow a direct pass through, you HAVE to use a lp on them. Resulting in the double filtered frequencies. When i run into this i just use the one on the HU and turn the filter on the amp all the way up. However ive heard you need to stay away from this because you could lose SQ and SPL from it depending on the application, but i havent really looked into it that much and couldnt say whether thats true or not.

 

[audioholic 5,000+ posts]

I was wondering the same thing sortof, sometimes you run into a situation where youre forced to use a crossover 2 times. Example, most pioneer HUs force you to pick a crossover frequency for the subs at the HU, where as some amps dont allow a direct pass through, you HAVE to use a lp on them. Resulting in the double filtered frequencies. When i run into this i just use the one on the HU and turn the filter on the amp all the way up. However ive heard you need to stay away from this because you could lose SQ and SPL from it depending on the application, but i havent really looked into it that much and couldnt say whether thats true or not.

Not true really unless you set one of the x-overs very badly.
Id personally stay away from any piece of equipment that forces me to use its built-in processing. That includes h/u's. What would a guy that has that pioneer h/u and amplifier do if he were wanting to run an external processor like an h701/c701? He would be screwed.

 

[mcsoul 10+ year member]

just use one

mah tweets want all the slope they can get:laugh:

 

[Etac 10+ year member]

i dont think it would actually.. i guess it kinda depends where the crossovers are on the HU/amp.. i dont know if its internally processed before its sent out of the HU or works similar to other external crossovers, but if the crossover is the last thing the signal sees on the way out of the HU and the first thing it sees on the amp, wouldnt this just change the crossover point..since they would in a way combine...?

but if you used passive crossovers and active HU (or amp) i assume it would work

 

[DBfan187 5,000+ posts]

They combine.

 

[audioholic 5,000+ posts]

mah tweets want all the slope they can get:laugh:

Are you sure about that? Tweets usually like a shallower slope for blending. Try a shallower slope with a higher cut off frequency. You may also need to play with your LP slope/point on your mids to compensate for tweeter adjustments.

 

[Etac 10+ year member]

steep slopes are generally over rated (unless you have a huge peak).. like audioholic said.. it makes it easier to blend.. and most drivers tend to hit their highest excursion where it is crossed at... reguardless or its 6db slope or 48 db..

also drivers are capable of playing lower than X hz say..they just cant take the power flat without over excursion/bottoming out

edit: this is more for highpass /sub sonic filters..

also changing the slope can change the phase 90 degrees.. unless it can be divided by 12 (correct me im wrong) then its either 180 or 0...

 

[mcsoul 10+ year member]

Are you sure about that? Tweets usually like a shallower slope for blending. Try a shallower slope with a higher cut off frequency. You may also need to play with your LP slope/point on your mids to compensate for tweeter adjustments.

My choice of drivers leaves little room for play; they both want 3khz. In experimentation I will take the mid higher rather than the tweeter lower. I think the tweeter could be damaged by anything lower than 24db/octave at 2.5khz (seas neo fabric on 75w rms).

 

[audioholic 5,000+ posts]

My choice of drivers leaves little room for play; they both want 3khz. In experimentation I will take the mid higher rather than the tweeter lower. I think the tweeter could be damaged by anything lower than 24db/octave at 2.5khz (seas neo fabric on 75w rms).

Which is why I was suggesting trying raising the xo point higher than 2.5khz, and try a shallower slope. Alot of old-school SQ guys swear by 6db slopes between the mid and tweet.
Point is, you aren't locked into the 2.5khz xo point. Altering it will/can affect what slope is optimum.

 

[James Bang 5,000+ posts]

trial n error.