Tech Assist For X-over Use

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Tech Assist For X-over Use

Postby JR » Mon Apr 25, 2011 3:23 pm

I'm doing a relay this Saturday. They tell me 6,000 people is average attendance. So I think I need big sound, and I think I have it. Except for one thing, the knowledge needed to properly operate it using a crossover.

Equipment I plan to use for "Front of House":
Behringer Zenix 2442FX Mixer
2 way stereo/3 way mono crossovers in mono mode (one Samson and one dbx)
QSC 1450 Amp (x2, bridged, one/Sub)
QSC 2450 Amp in stereo mode
Pair EV Eliminator Subs for lows
Pair PV 215 for Mids
Pair EV ZXA1 (Pwrd) for highs

Now to me it appears that I'll have a total program power availability of 5,000 watts. (2.5Kw/side)
And I plan to set the L/M x-over at 100 Hz and the M/H x-over at 700Hz, and The ZXA1 has an internal crossover set at 1.8KHZ
So I'll have 4-way separation; Low, Mid Low, Mid High, and High Frequencies.

I know it's not the most ideal set up. Usually the equipment is used separately or in different smaller configurations, but this time I'm using all I have available. Normally for karaoke in a small venue I use just the ZXA1s; sometimes with a powered speaker (set to use only the lows) as a sub.

Now here are my questions (3 each)
First, Am I correct in using the configuration and crossover settings as I just outlined?
Second, am I running any risk with regard to the safe operation of my equipment or degradation to the quality of my production?
Third, I had a Guitar Center sales person recommend that I disconnect the compression driver from the PV 215s for this application but his reason wasn't clear. Is this a prudent suggestion? Would I cause any damage to the drivers, and/or would the sound quality be degraded if I didn't disconnect them?
JR LaPorte
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Peoria, AZ
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Re: Tech Assist For X-over Use

Postby TheBartman47 » Fri May 13, 2011 1:11 pm

Depending on how you arange the speakers, you may or may not want to disconnect the compression driver, but if you're using an active crossover, it won't really matter because, according to your post, you will only be feeding this cab mid range frequencies in the first place, so the horn won't be putting out much of anything (it will be some, but very little, depending on it's internal crossover frequency). This cabinet is NOT biampable, because it only has two 1/4" parallel inputs on the back, no bi-amp input jacks. To make it truely efficient, you would need to change the wiring inside and bypass the crossover and drive the two woofers directly to the midrange amplifier (and not connecting the horn to anything, or if you can, connect it to another amplifier that is fed the high frequencies from the x-over. I don't have the specs on the crossovers you're using, but it is necessary to use one that has CD EQ for the highs. If it doesn't, your highs are going to sound very "honky".

Considering what all you have available, I would simply run this system bi-amp instead of tri-amp (crossover only between subs and the mid-high cabs). Also, keep in mind the PV series is the lowest (entry level) series made by Peavey, and the EV eliminator subs are also "entry level" audio gear, and will hardly be heard in an outdoor setting. They are only 400 Watts continuous power rated.

If you bi-amp only, (crossing only between subs and mid-high cabs), I would set the x-over point very low, since the PV215 is a quazi 3-way cab (the lower 15 is a pseudo-sub) to let it do as much work as it can, and let the EV subs handle only the very low frequencies. Probalby around 70Hz - 80Hz (you can use your ears to see what sounds best). Then splay your EV ZXA1 cabs to cover far side area, and the PV215 pointed straight out for front area coverage. Aim the speakers far enough apart so that the horns aren't overlapping coverage areas in order to get the best sound. Overlaping horns will cause comb filtering effect, nodes of high and low dropout zones.

For 6,000 people, this system really isn't up to the task, so don't try to drive your system harder than it can handle. It's going to be tempting to push it harder, but don't or you're likely to burn up a voice coil. To adequately cover 6,000 people, I would use at least between a 12,000 to 24,000 watt system. But, if they aren't too demanding on how much sound you can put out, you'll probably be ok. If you're shooting the long distance of a football field, the opposite end won't be able to hear a thing unless everyone else is deathly silent. So, another option would be to use the EV ZXA1 cabs for remote location speakers.
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