Would a rack mount crossover be better?

[Turdus]

This past weekend, I provided sound for a dance troupe in an 800 seat auditorium. I used the following, and the results were very good... plenty of clean power, moderate low end, and no dead/weak spots in the room:

mains: 2 Yamaha Club 15's, powered by QSC 1804, 600 watts @ 8 ohms

sub: Single EV 18, powered by Peavey 1500. I utilized the Peavey's built in switchable 150 Hz xover.

Looking at a rack unit, such as DBX, the xover seems to go as low as 45 Hz. Would there be much benefit in going with something like this, versus the switchable xover in the Peavey amp?

[Jimbilly]

As much as I don't like to recommend Behringer, we've had great luck with the all-in-one (crossover, protection, time delay, eq) Ultradrive Pro. It's a single space rack unit, 2 ins, 4 outs, I think of it as a crossover, but it does quite a bit more. My pro audio buddy set it up for our system (plugged it into his laptop for 'quicker' setup), I don't think I could have done it myself. Lots of other companies make all-in-ones, and there's probably better units out now, this one being about 4 or 5 years old.

If you want to keep it simple, and do it yourself, I'd probably go with the dbx or a Rane rack crossover, but it's hard to argue with what sounded very good last time. Do you run your speaker send cables through the sub amp?, and are they affected by the 150hz crossover? It might be nice to have a 'standard' crossover, that you can dial in a little better, especially if you're sending full-range to your mains. What does a good used dbx/rane cost?, about $100 these days?

[Turdus]

I should mention that the mains were running straight from the L/R outs on the board into the mains amp.

the sub was run from the mono out on the board, into the Peavey sub amp with 150 Hz xover engaged.

Trying to decide if it would sound much different if I went L/R into a xover, then sent those signals to main and sub power amps.

[Jimbilly]

I've always believed that if you're asking your mains to do less (less lows), they will be able to do better what you are asking them to do. If it were me, if I were adding a sub to my powered mains on my small rig, I'd go the rack crossover route.

Some of the newer QSC amps have built in crossovers so that you can run subs and mains off one amp, I think it's at about 100hz, - am I the only one that thinks the 150hz on your Peavey is a little high for a fixed crossover?

[Thundernotes]

Yes, bass is a power-hog. It is generally better to run through a crossover and steer your lows to a sub and let the mains carry the mid/high frequencies. It also helps to maintain proper phase relationships with the various signals.

[Hackubus]

Yes. Plus you'll have more control over your subs with the X-over. Not near as much control if you're just going out of a sub out on the mixer.

[Turdus]

the Yamaha Club 15's have a Frequency response of 55Hz-16kHz.

you guys have any suggestion for where I might initially set the xover?

[Hackubus]

Try setting the crossover point around 100hz. If the subs sound muddy, lower it down to around 80hz. Or adjust to taste from there.

[marcnorth]

I'm using a DBX Drive Rack PA+, It's a breeze to set up and our PA has never sounded better. It eliminated my cross over, dual 31 band EQ, Compressor and RTA unit. It walks you thru the setup process and when you're done you can store it for when you come back to the same venue. Best peice of PA gear I've ever purchased.

[Turdus]

Marc - I'd love to have one of those, but they seem kinda pricey... even used. Do you have to have the external mic to make those work properly?

[marcnorth]

They are a little pricey @ $500 for the unit and $100 for the RTA mic. You do have to have the mic to make it work properly.

But if you add up the price of all the stuff it replaces it comes out about the same if not cheaper.

The hassle it's saved me was worth the cost, and like I said before my PA has never sounded better and no more trying to turn knobs and play bass at the same time.

I justified buying it by telling myself I would sell the other units to make up most of the cost but as usual I still have all of it in the basement. If you decide to go the crossover route I have a nice DBX 234 stereo 2 or 3 way, mono 4 way crossover I could let go.