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Opinions on cheap crossover for cheap wide and surround speakers.

post #1 of 2
1/21/13 at 8:49pm
Thread Starter 
Trying to use 4 old, but good shape 3-way box speakers that my father-in-law got somewhere. Going to use them for Front Wide and Surrounds, well they sound like crap, seems like full range coming from the woofers and after looking in the box, down by the connection plate, I discovered there are no crossovers??? Only a small capacitor inline with the tweet and mid.

(No Name) Speaker info: 14" x 24" MDF Box, 3" tweeter, 4" Mid, 12" woofer

I replaced the woofers of the previous ambient speakers (now front wide) a few years ago, they are Goldwood -
Power Handling (RMS) 120 Watts
Power Handling (max) 240 Watts
Impedance 8 ohms
Frequency Response 28 to 4,000 Hz
Sensitivity 87.2 dB 2.83V/1m
Voice Coil Diameter 1.5"
Magnet Weight 20 oz.
http://www.parts-express.com/pe/showdetl.cfm?partnumber=290-335

The 2nd pair now being used as surrounds also needed woofers and I went with these GRS woofers -
Power Handling (RMS) 100 Watts
Power Handling (max) 140 Watts
Impedance 8 ohms
Frequency Response 30 to 3,000 Hz
Sensitivity 84 dB 1W/1m
Voice Coil Diameter 2"
http://www.parts-express.com/pe/showdetl.cfm?partnumber=292-422

I have no info on the 3" Tweeter and 4" mid speakers.

So... I am in need of some cheap 3 way crossovers. These speakers may be, depending on how they sound, just hold over speakers until I can one day build/buy some decent ones.

I found these and wanted some opinions before spending a little cash on them. - http://www.mcmelectronics.com/product/28-12744

Thanks for the opinions.
Edited by Sabrewulf... - 1/23/13 at 10:11pm
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post #2 of 2
1/22/13 at 11:12am
Your 3-ways have very simple XOs because they used the natural driver roll-off as the low-pass filters. The woofer's running full range and the mid and tweet protected from low frequencies by a capacitor as a high-pass filter. Not uncommon, and can be made well if driver design is chosen properly. Very hard to substitute driver as you need specific electrical characteristics, too.

That said, we do it differently these days. Differently enough that there's not much I can suggest as we start with frequency response and impedence response curves, then use crossover simulators to design crossover circuits. The advantages are primarily in use of actual impedence data, not a rated DC resistance, and the ability to match driver levels as well as contour the response curve. The biggest difference is where to start - a speaker designer starts with goals and seeks drivers that will meet those goals. Many neop[hytes start with a box, or a box and drivers as you have.

Even if that MCM circuit was at the right frequencies and slopes (note there's a 12dB/octave version, too), you'd still need resistors to match output levels, woofer-mid and mid-tweeter. Hard to go wrong with $5-10 XOs, just temper your expectations...

... and consider building a proven deisgn next time.
http://techtalk.parts-express.com/showthread.php?211558-Links-to-existing-DIY-speaker-designs

Have fun,
Frank
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