Crossover points help!
 

Hi!
I run alpine 6.5 separates and alpine 8" sub in sealed box off Sounstream amp. It has continuiosly variable low and high pass xovers.
Is there any routine in setting xovers right? I am tweaking it all the time, but don't seem to get it right. It's either too much boom or midbass disappears almost completely.

Another question-where can I get that black sticky stuff used to glue clear plastic sheets inside the doors to keep moisture out.

Thanks for any tips
Alex

Do the Alpine separates have their own crossover? I would assume so if it's a component set.

Anyway - most people recommend cutting the sub @ 80 Hz, and high passing the door speakers at the same or a little higher.

Since you have an 8" sub, you might want to try crossing it over at 90. But 80 is the "accepted" sub cutoff frequency.

Basically, you don't want to have too much overlap between the comps and the sub. Do you know what ratio the x-overs on the amp are? Like 6dB per octave, 12 dB per octave, etc? This tells you how the "rolloff" is - steep or gradual.

Okay - like this - let's say your amp's x-overs are 12 dB/octave. Pretty safe assumption. Anyway, an octave is 10Hz, so if you low-pass the subs at 80 Hz, it WILL play frequencies higher than that, but at a lower volume - so 90 Hz will be 12 dB lower, which is basically 1/4 volume of 80Hz, and so on. The same thing applies to high-passing the components, just in reverse - high-passed at 80 Hz, the comps will play a 70Hz tone at about 1/4 the volume of the 80 Hz tone.

On a 6 dB per octave "slope" as it is called, the same math above will have the speakers' (or sub) output decreased by about 1/2, rather than about 3/4 below (or above-for the sub) the crossover frequency.

The steeper the slope (the higher the dB per octave), the closer you should set the crossovers to one another.

Find out the x-over slope on your amp, and start with the subs from 80Hz down, and the comps from 80Hz and up, and then space them apart from there. Another tip is to shut the sub off (even if it means disconnecting the speaker wires), and tuning only the components. Set the x-over to where the speakers alone sound good to you, and they can crank up as high as you want them to without distorting from too much bass. Then add the sub. If possible, it's not a bad idea to tune the sub by itself, too - if there is any way to run it without the components. Do the same thing - tune it until it cranks up good without distortion. Then let everything run (comps and sub) and tweak it from there. If you can't run the sub by itself, just tune the comps, and then tune the sub with the whole system playing.

Hope this helps some.


~HH

I would crossover the 8" at 65 or 70 hz and the 6 1/2 componenets at 80 hz.