Cross-firing?

Hactar · #1 09-25-2011, 01:32 PM

Here is the sad situation:

I am a student at a school that has a sound system that I will be using for a sort of talent show. I am, unfortunately, the most knowledgeable "sound engineer." Here are the speakers we have:

2x JBL Eon15 G2 powered speakers
2x JBL Eon 515 powered speakers

The venue is a large (~96x52) gymnasium (yeah, I know

).
My question is whether the coverage will be better if I cross-fire the pairs of speakers.

This document seems to say yes, but keep in mind, that the speaker pairs are mismatched (one Eon15 G2 and one Eon 515 per side).

So, what do you experts think I should do?

BTW, first post!!

T-Bird · #2 09-25-2011, 11:51 PM

Hi.

Welcome to TalkBass Hactar.

In a situation like that, I'd test the placement and orientation with noise, or with a very familiar reference tune.

The right angle to any wall will be bad, which You probably already know, so that limits the placement options quite a bit. Shouldn't bee that hard.

Cross firing arrangement without DSP and especially with mismatched speakers is always a roll of a dice, so I wouldn't even try.

Regards
Sam

walterw · #3 09-26-2011, 10:23 PM

all you can do is try to aim them so that they hit the crowd directly, don't point at any reflecting walls, and if possible so that most people are not getting two side by side both aimed right at them. maybe two on the outsides of the stage aimed in, and two in the middle aimed out a little?

for some real answers from world-class pros, ask your question over on PSW.

just remember to use your real name, and stay out of the "lab" where the national touring guys hang out.

MNAirHead · #4 09-27-2011, 07:47 AM

do you have a stereo mixer.

You could split the use.

Unfortunately we don't know exactly what you're trying to do -- without full information you'll probably just be mislead.

There are way too many variables -- we don't know if it's just speaking, vocals only, where in the room you're placed... and so on.

When in doubt cluster them together in the middle of the room.... there are various configurations...

In a tough environment getting a list of priorities and simplification seem to be the best route.

Tim

Hactar · #5 09-28-2011, 04:08 PM

Thanks for the responses guys.

Unfortunately a center cluster is not going to work, and there is no way to fly anything.

It is a very tricky venue, and walterw's suggestion is probably what I'm going to do. I do realize that with mismatched sides and no DSP, cross firing could be rather nasty.

The reason I thought cross firing would be a good idea is because currently the SPL levels throughout the audience are rather inconsistent.

More details:
Running main mix stereo (yes, I know:roll no

The mains will have mainly vocals in them, but also guitar, bass, kick, cello, violin, piano, and recorded playback.
Room is painted cinderblock

, 96'x52', mains are placed approx 25ft from wall.

walterw · #6 09-30-2011, 05:48 PM

mnairhead's idea could maybe work;

you could set it up stereo, but with each pair of boxes split apart, one on each side.

one set of left-right boxes could be the all-important vocals, as well as stuff that doesn't have the same frequency range as vocals, like kick and bass.

the other pair of boxes (also split left and right) could then have the rest of the instrumentation.

since the boxes sitting side-by-side on each side of the stage would have different stuff coming out of them, you wouldn't get the phasing weirdness.

or maybe one pair outside with the instrumentation, and the other pair in the center with vocals?

1958Bassman · #7 09-30-2011, 06:11 PM

Quote:

Originally Posted by Hactar

Here is the sad situation:

I am a student at a school that has a sound system that I will be using for a sort of talent show. I am, unfortunately, the most knowledgeable "sound engineer." Here are the speakers we have:

2x JBL Eon15 G2 powered speakers
2x JBL Eon 515 powered speakers

The venue is a large (~96x52) gymnasium (yeah, I know

).
My question is whether the coverage will be better if I cross-fire the pairs of speakers.

This document seems to say yes, but keep in mind, that the speaker pairs are mismatched (one Eon15 G2 and one Eon 515 per side).

So, what do you experts think I should do?

BTW, first post!!

How many people will be in the gym when the show is going on? I think you should have more speakers so the coverage will be more even and so those who are closest don't get blown out. Talk to a local music store and ask if they'll trade the rental for you guys putting a good-sized sign up with their name.

testing1two · #8 09-30-2011, 07:00 PM

I would suggest limiting the width of the stage area to 24 or 30' and place the 515's at each end of the 'stage' leaving the G2's to serve as monitors (even if you don't have an aux send and have to feed them the same mix, you can at least use the individual volume controls on the speakers themselves to keep from blasting out the performers).

The 515's have 100 degree horizontal dispersion so if you keep them away from the outside walls you will minimize the harsh first reflections and get relatively decent coverage.