Need Inexpensive Crossover


I'm using Monitor Audio GR-10 bookselves and a Klipsch powered subwoofer. Right now I'm running them both full range - and using the low pass on the crossover to have it kick in at about 80hz.

What I want to do is to roll off the low end on the bookshelves - as the bass sounds a bit too muddy at higher volumes (and just send the higher frequencies to the bookshelves - say above 80hz)...... and then just send the low frequencies (that aren't being sent to the bookshelves) to the sub (and probably not use the subs lowpass filter at all).

I know that crossovers can get to be pretty pricey, as all high end audio can. However, right now I'm a bit tapped out on the high end audio budget... and need something that will do for the moment - maybe I can upgrade lower.

Do I need something that has both a lowpass (for the sub) filter and a highpass (for the bookshelves) filter. Can one crossover unit combine this, or do I need 2?

I'm looking at spending no more than $100.

Is this possible?

thanks for the help (in advance)
zenguy
The Behringer 2496 is indeed a lovely way of making x-over dabbling a bit less tedious... with its full array of filter slopes and q. I had considered getting it to use as a tool in designing xovers for my spkr projects (including line level filters and passives). But the price, while excellent, was/is prohibitive for me :(
Sogood51...I did study the material on 1st order series X/O which Karls provided. (If you are there Karls, thanks again). Once you wade through all the greek alphabet it really doesn't say anything profound (IMHO of course).

Next thing I predict is a parallel/series three way crossover. Be the first on your block to own one:-)
There is also Outlaw Audio's ICBM. While primarily designed for bass management for multi-channel audio (SACD, DVD-A), it can also be used as a 2-channel crossover. It has continuously-variable crossovers from 40HZ-up, and either maintains stereo bass output or combines low-level signals into a mono LFE-out.

New it is only $249, and I think there are some used ones listed on A'gon for under $200.
The X30 is very good,  although the ICBM is much better even if you only use the front two channels......I had both and I regret selling the ICBM.