# crossover for a home stereo



## mbandgeek (Apr 29, 2008)

Hi all,

I am assembling a stereo from speakers that i have here around the house for college. I have two KLH 970As as the front L and R. I have a rather large speaker 10" speaker i have posted about previously I plan on using as a subwoofer. I plan on using a standard radio receiver and these speakers; however, my reciever is too old to have a dedicated sub channel. I was looking at building a crossover for this to put in line with the front speakers to send the low frequencies to the sub. 

Do you guys and gals know of any good websites where i can learn how to build one of these?
or
is there a website that sells them?


----------



## Eboy87 (Apr 29, 2008)

A crossover is essentially a capacitor and an inductor. Cap filters out high frequencies, and the inductor filters out low frequencies. Varying the value of each will determine the x-over point, and varying the number of components in each band will determine the slope of the x-over point. I haven't the faintest clue as to values you should use, but conceivably, yes, you can build your own, though I would probably look around for a pre-made one.


----------



## avkid (Apr 29, 2008)

Parts Express has post amp crossovers meant for car audio, but they should work for you.
http://www.partsexpress.com/webpage.cfm?Webpage_ID=3&CAT_ID=35&ObjectGroup_ID=745
As for the crossover point, I have no clue.


----------



## museav (Apr 30, 2008)

You mentioned having a (singular) speaker for a subwoofer, meaning that you might also have to derive a mono signal for the sub, have a dual voice coil subwoofer driver or just use one channel. Also keep in mind that you typically would low pass the sub and then high pass the main speakers so that they don't overlap, you could try it with just a low pass on the sub, but it may sound muddy.

You can buy a passive crossover or build your own, there are numerous online sites addressing either approach. In either case, you ideally need to know the desired filter characteristics such as the crossover point, slope and type of filter, speaker impedance and so on. Unless you have the necessary information from the speaker manufacturers or a way to determine these values through measurement, then you'll probably just have to guess. With those speakers and a 10" sub, you might have to crossover fairly high, I would not go below 100Hz and would probably look at more like 120 or 150Hz.


----------



## mbenonis (Apr 30, 2008)

I skimmed over this page, and it looks like it'll be pretty helpful. I'll read through it when I get a few minutes of free time.

http://sound.westhost.com/lr-passive.htm

Feel free to ask if you have any electrical questions...


----------



## BNBSound (May 3, 2008)

Simple passive crossovers are likely to lack the slope and depth that you need to work very well. While a cap/coil circuit might work well enough to help tune up an external speaker on a CB, there will be significant loss. A cheap alternative might be to see if you can scavange some passive crossovers off some old PA cabs. Then at least you would have some engineering in them. One last thing, while 10" subs do exist and can be quite effective, unless your 10 is specifically designed to be a sub you won't be happy with the results. The frequency response won't go low enough and if you drive it too hard you'll start to fold the cone, which is a particularly unpleasant thing to listen to. It sounds like your stereo is farting to the beat.


----------

