Motown wrote on Fri, 16 April 2004 23:40 |
I run an inexpensive set up, 12 channel Carvin board with 2 Carvin 15's with horn, and 2 Behrenger 18's. The question is about the 18's. I know the gear is not considered top notch but any other venue that would require a larger set up usually the venue provides the gear for live music applications, at least in my area. We have had a lot of muddiness from our system. Doing research mostly on this great site I recently found a few things that may help this dilemma. One would be delay and EQ, the second would be the crossovers in the Behrenger 18 subs. They are passive which from what I gather is not the best way to go. According to the website the specs are: Low pass 175hz, slope 9db/oct. High pass 175hz slope 12 db/oct. I'm a noob to this so it's all Greek to me right now, but that will soon change. I know Behrenger is not the best, nor Carvin for that matter but the cool thing about the subs are you can incorporate active crossovers. The question is with the specs provided and a brief description of my gear could the crossover be part of the culprit for the muddiness and if so what steps could be taken to correct it? Is an active crossover the answer if so which one? Could the Carvin 15's w. horns benefit from an external crossover as well? Thanks in advance!!
|
Well, I object to some of the advice given here--you're asking for help with what you've got, and some people are telling you to buy all new stuff. Not helpful. Someone else suggesting underlapping frequencies, which is a recipe for MUD in your case as well.
The answer is yes, you should actively cross over everything when you're using this setup. You can run mono and run the subs off one channel and the mains off the other channel of your amp, but I don't know how much power you're sending--probably not enough. Get a bigger amp for the subs as soon as you can, and get a DBX little crossover or something like that.
Engage a subsonic filter at 50hz--your subs won't go lower than that and it will save you lots of power. There's not much information down that low in your situation anyway. Then low pass the subs at 125-150, but with a 24db/octave slope. AN octave is a doubling of frequency, and this number gives you a spec for how much lower the signal will be at a given frequency. So, if you lo pass at
150hz@24db/octave, then the signal is 24db attenuated by the time the signal reaches 300 hz, and 48db down at 600. See how this works? It filters out what you don't want, and sharper slopes filter more--it is a steeper slope.
So, to continue, these things will vary a bit with the room, but I would use the hi pass filter for the subs (this is actually called bandpass, because you're allowing 50 and up and 150 and downm so it's just a band of frequencies being passed). My QSC sub amp has the 50hz filter so I don't have to use the crossover to do that. Then I set my crossover (in your case) to 150 lo pass for the subs. Then set the top cabs to 200hz or so. They won't go much lower than 100, anyway. So, you'll have the subs playing 100 hz full volume, and the tops will be playing that 100 hz, too--but 24 db attenuated. At 150, it's 12db down on the tops, and the subs run up to that. The fact that subs and tops are covering the 150-200 range at attenuated levels should make up for the underlap, but play around with it--try 150 lo, 150 hi, 125 lo, 150 hi, etc., until you find what you want.
But in short, the active crossover is crucial--because as you've noticed, look how shallow the slopes are on passive crossover networks! Passive crossovers also sap power--a good reason to pull them out of the loop if possible--bypass them once you're using the active crossover. Good luck!
David