# Using Active Crossovers for Prototyping



## Anthony (Oct 5, 2006)

BoomieMCT and I decided to give active speakers a test run with my center channel prototype.

He has a portable pro amp and Behringer DCX2310 crossover. It's fixed at 24dB/oct L-R, but it is adjustable in every other way.

We set it up as a three way, using my car-amp test rig to drive the woofers and the pro amp to drive the mid and tweeters. Not ideal, I know, but it was interesting.

First off, the fans in pro gear are LOUD. Distractingly so. I may have to use 20' of speaker wire and put this off in a closet while I measure because it's tough to listen to detail when you hear a loud "WHIRRRRRRR" 

So we very unscientifically put on some music and just fiddled with the knobs for crossover frequency and output level. Every once in a while we'd toggle to the stereo Magnepan 10.1's for comparison.

We learned two major things: One, my woofers are too sensitive (or my mids too insensitive). I would need to pad the woofers -- not a good thing. Two I have some sort of stored energy problem that is present both active and passive (and doesn't show up in raw driver testing), so it must be the baffle. We mitigated this with moving the crossover around, but I think we were masking it by lower output at that resonance (around 350 to 450 Hz).

so active was not the panacea I was hoping for, but it gives great insight into where crossover points should go. If I can find a good fanless rack mount three channel amp), I may build a rig like this for all my speaker testing and use the DCX2496 for advanced prototype stuff like notch filters and the like.

the good news was that my original crossover points weren't too bad. The mid to tweet cross was spot on, as was the padding. (3.5kHz). I did, though like the sound of moving the woofer crossover from 400 Hz up to 650 or so. I never considered going up that high because I wanted to stay away from the breakup node (and I was only looking at 2nd L-R for the passive crossover).

I think I will still try to design a passive crossover for this speaker. There's something to be said for just having a speaker, amp, and that's it. Same speaker can go on any system with little fuss. Plus, I already have a beast of a power amp, so it's not like the efficiency hit is worrying me. 

Attached is a cell phone picture of the setup. Note that this is a test baffle -- I don't plan on having my actual speaker this ugly.


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## BoomieMCT (Dec 11, 2006)

I agree - using an active crossover to prototype kinda sped stuff up a bit. I don't see what the big deal about padding woofers is though - I've seen other designs that do it. As an option you can pad them like the DDRs which are padded in a such a way that it provides some EQing to boost the low end. Or you could get by using smaller woofers. Or, as a third option, try using more sensitive mids. Since you are raising your lower crossover you can try using a 3" mid that doesn't have quite the bass or excursion of the B3N's. If the Tang Band W3-1364S's I lent you don't work there are a plethora of other options to consider. With 20 watts on each they shouldn't hit overexcursion above 450Hz. 

Before my wife needs her amp and crossover back we need to try adding some angle brackets or something to that test baffle to make sure the woofers aren't loosing some energy moving the baffle instead of the air. I had something similar on my dipoles at about 150Hz before I added more bracing. Once that front baffle is stiff enough we can try messing with the size using cardboard or something.


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