Can I make a crossover or buy one?

My son got some small B&W speakers for Christmas and their low end bottoms out around 40-50hz, and if my guess is right it's probably down at least 3db at that range. So I bought him a passive sub, which is nothing more than a 12" woofer in a box. What I need now is a crossover that both combines L&R channels for 100hz and below(or there abouts), but also provides a high-pass for 100hz and above for the B&W's. If I can just buy a unit that will do all that I would probably just fork out the bucks but I can't find one. Twenty years ago or so I went to an electronic trade school (while trying to find myself), but have forgotten just about all I learned. But if someone had a schematic I may be willing to try. So if you know of a brand/model that will accomplish this or have a design could you let me know?Thanks, Jim
some sub's have integral adjustable crossovers built in that will take care of all this for you. They are even tunable for best integration; get one with a phase adjustment for even better results.
Your best bet is to get an active adjustable crossover and separate amp. To make a passive crossover for your existing sub, you will need the comprehensive spec sheet on the driver and then run calculations on the box to determine the system Q and any other effects the box may have on the driver. In addition, low frequency passive crossover networks are the most expensive ones to make, so it would not be a "cheap" experiment.There may be an active crossover "kit" out there, if you look around on the web, and if you're handy with a soldering gun.
Go to your local pro music shop - they may have what you are looking for - Rane brand comes to mind or even less expensive stuff they keep around to sell to DJ's.
Tried posting this last night, but for some reason, my connection went down. Maybe my server needs Viagra : )

Jimmy, the closest thing that i could easily find would be part number 260-221 OR 260 - 220 at One of those is designed for an 8 ohm system and the other is for a 4 ohm system. The 8 ohm crosses at appr 150 hz ( kinda high in my opinion, but... ) and the 4 ohm at 130 Hz ( same thoughts here ). It also provides outputs for the monitors that attenuate the lows at a rate of 6 db's per octave at the above mentioned frequencies. If you have questions about this, snag their phone number off of the website and give them a call tomorrow. Ask for Sean in technical assistance. NO, it's not me : )

You might also want to check and see what Madisound has to offer. They can custom build crossovers to your specs at pretty reasonable prices. I had them do computer simulation for the installation in my car after i gave them all of the driver parameters and mounting locations. Their website address is If you need technical help, they have an excellent forum. You could also call them. If you do, ask for.... Nah... i don't think that a Sean works there, but you never know... : ) Sean
I've been racking my brain for 2 you just ask, thanks!
Yo Jimmy,

You might want to consider the Parts Express subwoofer amp with built-in crossover. Go to:
It would require cutting a hole in the back of the enclosure and soldering a couple of wires to the speaker terminals but it should solve the problem.
If you want to go active, check out Marchand. Make sure you read through what they have to offer. There are a lot of upgrades and different options. Everything is also sold in kit form if you are a DIYer. Don't see what you need? Give Phil a call. I have a full blown tube x-over by them and it is phenominal.