Question for any Sound/Audio Engineers

[PHANTOM21]

I'm producing a conference at the Corpus Christi Convention center.....the group i'm working for will be in exhibit hall B, a cavernous hall with 30 ft. ceilings and is about 15,000 sq. ft.

The conference is for about 1000 people.

My dilemma is how to configure an audio sound system for that type of room without running into any delay or sound clarity problems.

Dilemma #2...the client wants to keep to the costs down to around $2000 - $3500, so any kind of rigging is out of the question. Unions will kill me on the labor alone.

I have my hands on 8 JBL Eon15 powered speakers and 4 JBL non-powered speakers.

any advice would be appreciated

thanx

[Manu4Mayor]

Do you have stands for those Eons? Describe the non-powered speakers. Will you be located at the far end of the room? What kinds of amps do you have for the non-powered speakers?

I'm not a sound engineer but I haved stayed in a Holiday Inn before.

[Veritas]

Originally Posted by PHANTOM21

I'm producing a conference at the Corpus Christi Convention center.....the group i'm working for will be in exhibit hall B, a cavernous hall with 30 ft. ceilings and is about 15,000 sq. ft.

The conference is for about 1000 people.

My dilemma is how to configure an audio sound system for that type of room without running into any delay or sound clarity problems.

Dilemma #2...the client wants to keep to the costs down to around $2000 - $3500, so any kind of rigging is out of the question. Unions will kill me on the labor alone.

I have my hands on 8 JBL Eon15 powered speakers and 4 JBL non-powered speakers.

any advice would be appreciated

thanx

Well, each person absorbs the same amount of sound as a 6 square foot rug, so keep that in mind during sound check

As for delay/echo's, there isn't much you can do about that, it all depends on the acoustics of the room. In other words, no matter how you position your speakers, you'll get an echo/delay if the room has bad acoustics. To make it less apparent though, turn down the 'attack' of the sound.

It's hard to give advice on this, since you can change so much and it all depends on the situation; seminar, rock concert, etc.

[PHANTOM21]

Originally Posted by Manu4Mayor

Do you have stands for those Eons? Describe the non-powered speakers. Will you be located at the far end of the room? What kinds of amps do you have for the non-powered speakers?

I'm not a sound engineer but I haved stayed in a Holiday Inn before.

I have a 320 watt powered amp mixer that i typically use with the non-powered speakers which i set on 6' stands. The non-powered's are same shape and size as the powered speakers and are of course lighter.

The main stage area is on one end of the room which would be the short side if you were looking at a rectangle

Originally Posted by Veritas

Well, each person absorbs the same amount of sound as a 6 square foot rug, so keep that in mind during sound check

As for delay/echo's, there isn't much you can do about that, it all depends on the acoustics of the room. In other words, no matter how you position your speakers, you'll get an echo/delay if the room has bad acoustics. To make it less apparent though, turn down the 'attack' of the sound.

It's hard to give advice on this, since you can change so much and it all depends on the situation; seminar, rock concert, etc.

its more of a seminar and yes the room as crappy acoustics.

it has been suggested that i use mutliple speakers set along the sides of the room spaced 20-30 feet apart.

even with that type of configuration and keeping the Hi's down and Low's even lower, would there still be a significant delay problem?

[Manu4Mayor]

Hmm. Unfortunately, because of the high ceilings, size of the room and rectangular shape you're probably going to run into echos that you can't do anything about. You might be able to cut down on sound reflection if you could run some sound absorbing material below, behind, and to the sides of the speakers. Then you could just stack the speakers with equal sums on each side. For example, 4 Eons and 2 non-powered speakers per side.

If you can't stack the speakers and lay down carpet or other material then line them up with the non powered speakers on the inside and Eons on the outside on each side. Then angle the Eons slightly toward toward the middle, in kind of a semicircular configuration on each side. This should help channel the sound forward towards the middle of the room. Because of the natural dispersion pattern of the speakers and the power behind them, people along the side walls should still be able to hear fine.

One last question. Are any of these speakers long-throw or are they all short to medium throw speakers? If the non-powered speakers are long throw you should be okay. If none of these speakers are long-throw then we need to go back to the drawing board with my suggestions.

Given the size of the room you need to produce sound that can travel in a forward direction a long way. Long throw speakers do this well.

[PHANTOM21]

heres a crude diagram of what i have to work with...keep in mind the ceilings are 30'+ high

[Manu4Mayor]

Your situation is actually better than I thought based on your diagram. I think it helps that your room is almost a square. If all of your speakers have similar characteristics to your Eons, here's what I would do. Scrap the ideas I initially mentioned and do something similar to the prior suggestion you received. I would position your non-powered speakers below the stage in the center, only elevated slightly so that they are not touching the ground. Then I would run two Eons on each side on the stage. One flanking the non-powered speakers on each side and not on a stand and one on each side near the front two corners of the stage, angled, on a stand. Finally I would run two Eons on each side, near the side flat plasma monitors and angled towards the center of the room. This only works well if all the speakers have similar characteristics.

[Veritas]

By having more Low's than Hi's you will be able to reduce the echo a bit, just because of wavelength difference, but it won't be a significant difference.

Manu said it best- "you need to produce sound that can travel in a forward direction a long way"

You don't want speakers all over the place going in every direction. If you're going to have an echo it might as well be a consistent echo. I'd position speakers on the main stage towards the audience and possibly another set in the middle of room also going towards the back of the room, angled slightly inward though.

Manu also made another good suggestion with trying to find sound absorbent material, but given the size of the room that might be pretty hard to do. 1000 person audience is a great start though, people absorb sound great Carpetting is another thing you can use that would also look nice.. having egg cartons on the wall during a seminar would look a bit strange lol.

All technical issues aside, your ears are your best friend, be patient while setting up. Sound setups always require a lot of trial and error.

[Manu4Mayor]

Great advice Veritas.

[PHANTOM21]

im guessing this is the configuration you are suggesting, also would it help if i was to use a small line delay processor between the front speakers and the secondary speakers?



i was informed that sound travels at 1 millinsecond per foot in which case the secondary speakers should be set 60 ft from the front speakers to enforce the sound coming from the main stage speakers, any validity to that?

[Manu4Mayor]

Phantom, can you post specs about your non-powered speakers? Like frequency response, dispersion pattern, peak and RMS power ratings, etc... Are they also JBLs? I'm familiar with the Eons. I looked at them when I was considering what speakers to use to for the lounge my friends and I are building.

I'm not big on using sound processors for delay. I like using speakers with controlled output and similar characteristics so the sound is uniform.

As for the diagram, pretty much except I would put the first set of Eons along the wall, a little further down the wall and closer to the first plasma monitor. The second set of Eon speakers would probably be just to the right the middle plasma monitors. That way, I could put one more set of Eons on the front corners of the stage, aimed at the middle of the room.

[PHANTOM21]

from their website


The flagship of the new series is the JBL EON15 G2, delivering 300 watts of power to a 15" neodymium Differential Drive® LF driver. The driver boasts a dual neodymium magnet and dual voice coil motor that efficiently delivers high output from a lightweight woofer. Meanwhile, the HF amplifier delivers 100 watts of power to a 1.75" titanium diaphragm compression driver with Ferro-fluid cooling.

On the rear panel of the powered speakers: 120v 60Hz 140 watts / Aux Receptacle 6.6 amps 800 watts max

rear panel of non-powered 250 watt 8 ohms

Frequency Range (-10 dB): 39 Hz - 18 kHz
Frequency Response (±3 dB): 42 Hz - 17 kHz
Horizontal Coverage (-6 dB): 90° Nominal
Vertical Coverage (-6 dB): 60° Nominal
Rated Maximum SPL 129 dB, @ 1 m (3.3 ft)
Dimensions (H x W x D) 686 mm x 430 mm x 444 mm (27 in x 17 in x 17.5 in.)
Net Weight 21 kg (46 lbs.)
LF Driver Integral frame with one 15" (380 mm) driver, dual neodymium magnet, 2" differential drive voice-coil.
HF Driver JBL 2418H-1 1" (throat diameter) compression driver with 1.75" diameter titanium diaphragm. Ferro-fluid cooled.
Amplifier Power LF 300 watts @ low-frequency driver impedance.
Amplifier Power HF 100 watts @ high-frequency driver impedance.
Input 1 Sensitivity -44 dBu to -22 dBu for rated output (Mic/Line switch in MIC position).
-12 dBu to +20 dBu for rated output (Mic/Line switch in LINE position).
Input 2 & 3 Sensitivity -18 dBu to +20 dBu for rated output.
Output Level +20 dBu (peak), Loop/Mix switch in MIX position.
Connectors
- Input 1
- Input 2 & 3 XLR/F, balanced
1/4" Phone, balanced (TRS)
Crossover Frequency 1.5 kHz
Limiting Low frequency amplifier controlled by dynamic filter.
Loop/Mix Out XLR/M, balanced
EQ High Frequency Shelving, ±15 dB @ 5 kHz Low Frequency Shelving, ±15 dB @ 120 Hz
AC Input 110 - 230 VAC, 50 - 60 Hz., 175 watts rating per UL, detachable IEC power cable.

[Manu4Mayor]

Originally Posted by PHANTOM21

from their website


The flagship of the new series is the JBL EON15 G2, delivering 300 watts of power to a 15" neodymium Differential Drive® LF driver. The driver boasts a dual neodymium magnet and dual voice coil motor that efficiently delivers high output from a lightweight woofer. Meanwhile, the HF amplifier delivers 100 watts of power to a 1.75" titanium diaphragm compression driver with Ferro-fluid cooling.

On the rear panel of the powered speakers: 120v 60Hz 140 watts / Aux Receptacle 6.6 amps 800 watts max

rear panel of non-powered 250 watt 8 ohms

Frequency Range (-10 dB): 39 Hz - 18 kHz
Frequency Response (±3 dB): 42 Hz - 17 kHz
Horizontal Coverage (-6 dB): 90° Nominal
Vertical Coverage (-6 dB): 60° Nominal
Rated Maximum SPL 129 dB, @ 1 m (3.3 ft)
Dimensions (H x W x D) 686 mm x 430 mm x 444 mm (27 in x 17 in x 17.5 in.)
Net Weight 21 kg (46 lbs.)
LF Driver Integral frame with one 15" (380 mm) driver, dual neodymium magnet, 2" differential drive voice-coil.
HF Driver JBL 2418H-1 1" (throat diameter) compression driver with 1.75" diameter titanium diaphragm. Ferro-fluid cooled.
Amplifier Power LF 300 watts @ low-frequency driver impedance.
Amplifier Power HF 100 watts @ high-frequency driver impedance.
Input 1 Sensitivity -44 dBu to -22 dBu for rated output (Mic/Line switch in MIC position).
-12 dBu to +20 dBu for rated output (Mic/Line switch in LINE position).
Input 2 & 3 Sensitivity -18 dBu to +20 dBu for rated output.
Output Level +20 dBu (peak), Loop/Mix switch in MIX position.
Connectors
- Input 1
- Input 2 & 3 XLR/F, balanced
1/4" Phone, balanced (TRS)
Crossover Frequency 1.5 kHz
Limiting Low frequency amplifier controlled by dynamic filter.
Loop/Mix Out XLR/M, balanced
EQ High Frequency Shelving, ±15 dB @ 5 kHz Low Frequency Shelving, ±15 dB @ 120 Hz
AC Input 110 - 230 VAC, 50 - 60 Hz., 175 watts rating per UL, detachable IEC power cable.

Thanks Phantom. But how about your non-powered speakers? Are they similar to these. Never mind, I think I figured out the answer to this question.

Yeah, I think you'll be fine with the speakers you have. Just get there early to setup, preferably a day before the show so you can have time to try out some things.

[PHANTOM21]

im still lookin for info on the non-powered's......all the manuals were trashed a while back

Originally Posted by Manu4Mayor

Thanks Phantom. But how about your non-powered speakers? Are they similar to these. Never mind, I think I figured out the answer to this question.

Yeah, I think you'll be fine with the speakers you have. Just get there early to setup, preferably a day before the show so you can have time to try out some things.

we'll have a full day to set up........im goin out on a limb here but maybe just maybe you might have a clue how to set up an audio system....need a job??


could always use an audio tech...even tho the brass wont get me one

[Loop]

[quote=Manu4Mayor]Your situation is actually better than I thought based on your diagram. I think it helps that your room is almost a square. QUOTE]

WRONG WRONG WRONG. Please do yourself a favor and ask this question on avsforms.com they actually know alot more about this than most people in here. A sqaure room provides the WORST acoustical properties of any room design.....ever wonder why a movie theater is NOT square? If you are really interested, I have a room dimension calculator which I used to help design my home theater that I can send you (pm me if interested). It allows you to enter your room dimensions, and then tells you how many problem frequencies you have. Then based on where your seating is located, it will tell you if you are in a null or peak (peaks can be tamed--if you will, but nulls cannot).

Based on your situation, you might be able to move items (banners, booths, etc.) in specific locations (i.e. first reflection points) to help with acoustics. You need to spend some time in the room testing. Also, I use a Behringer Pro Feedback destroyer (I only use the parametric EQ portion of it to flatten out my bass response), but it is a very useful tool for reducting feedback for just this type of occasion.

Good luck, and do yourself a favor and go check out http://www.avsforum.com/avs-vb/index.php

[PHANTOM21]

thanx loop, actually feedback isnt a problem its all the damm echoing and delay's that give me headaches....but ill check out that site too.

[Manu4Mayor]

Originally Posted by PHANTOM21

im still lookin for info on the non-powered's......all the manuals were trashed a while back



we'll have a full day to set up........im goin out on a limb here but maybe just maybe you might have a clue how to set up an audio system....need a job??


could always use an audio tech...even tho the brass wont get me one

Well, I'm not a professional audio tech but I do know some things about audio systems and hookups. When I worked for RadioShack back in college I had to be able to teach people how to hook up their home theatres. People that bought stuff at Bjorn's often had questions and I had to have answers.

I learned about what to look for when it came to buying speakers, amps, etc and how to put them together (basically how to make sense of amp, speaker specs, etc...) and some basic knowledge about acoustics.

When's the conference? If you need help, I might be able to free up some time for a nominal charge.

[quote=Loop]

Originally Posted by Manu4Mayor

Your situation is actually better than I thought based on your diagram. I think it helps that your room is almost a square. QUOTE]

WRONG WRONG WRONG. Please do yourself a favor and ask this question on avsforms.com they actually know alot more about this than most people in here. A sqaure room provides the WORST acoustical properties of any room design.....ever wonder why a movie theater is NOT square? If you are really interested, I have a room dimension calculator which I used to help design my home theater that I can send you (pm me if interested). It allows you to enter your room dimensions, and then tells you how many problem frequencies you have. Then based on where your seating is located, it will tell you if you are in a null or peak (peaks can be tamed--if you will, but nulls cannot).

Based on your situation, you might be able to move items (banners, booths, etc.) in specific locations (i.e. first reflection points) to help with acoustics. You need to spend some time in the room testing. Also, I use a Behringer Pro Feedback destroyer (I only use the parametric EQ portion of it to flatten out my bass response), but it is a very useful tool for reducting feedback for just this type of occasion.

Good luck, and do yourself a favor and go check out http://www.avsforum.com/avs-vb/index.php

Loop, you never want a perfectly square room. I know that and lots of people here probably know that. What I feared was a room that was very narrow on the short side and really, really long. If you look at a theatre you have a reasonably shaped rectangle. If his dimensions were 60 x 250+ then to me that is harder to work with than a room that is 200 x 250. In the former kind of room, you need to send sound a long long way. You need to use long throw speakers that are clearly more expensive than the budget he has to work within. In a 200 x 250 room, you can space out smaller medium throw speakers, like he has, a little more and take advatnge of the shorter dispersion characterics on the speakers he is using. My ideal preference would have been a room whose width was roughly half the length. But that is not what he has to work with. With medium, tight dispersion characterics you can more easily control the sound. The kind of speakers he's using, can work in this environment as long as he utilizes proper spacing and angling of the speakers.

Ever wonder why theaters use series of relatievly small sized, similar speakers throughout. Even though they can purposely build ideal sized rectangles and work in plenty of sound dampening material, they use lots of smaller speakers so they can purposely control the sound and produce sound that is uniform throughout.

Phantom, use common sense. It goes a long way. Trust your ears, they can really tell you a lot. Sound Analyzers and processors work great but you don't have to make this more complex that it needs to be.

[FamousJames]

^^^Exactly......you only have so much to work with...just plug it in and listen....then make adjustments.

[Fingerroll]

I wanna toss in my 2 cents. I run sound every Sunday and sometimes play through what looks to be like a comparable setting. With that ceiling you're going to have echos and probably some hums, but I'm sure they'll clear up as the room fills with bodies. As everyone has said here earlier, the best thing is to get there early and find a comfortable setting, then see if you have to change things when the talking starts. Chances are you won't have to change much if you do.

I would also recommend the "2 in front, 2 in the center" config. It's a very basic set-up that always seems to work best. The simpler your hook up, the less you'll have to adjust if problems arise.

Let me guess: Wireless mic? Love those things.