PA speakers for huge space?

[bachatero]

In a couple weeks I'm bringing some of my audio equipment to a volunteer event where they're taking over around a 600x600 foot (180x180m) convention center space.

Right now, I have some EV ZLX-12BT PA speakers and an active sub. Everything will be set up at one of the columns near the middle with the speakers pointed at 45 degrees on the ground to get some ceiling bounce. This is in fact an upgrade over last year where I had a single offbrand PA speaker (but one with a 15" driver)!

The only problem is, the ZLXs are made of polypropylene, not the stiffest material, so they've got YUUUGE resonances around 70-200Hz. Dr. Toole et al. found that resonances are one of the biggest limiting factors to sound quality.

I was thinking of upgrading to the ETX-12Ps which are made of super solid wood, but they're a whopping $1600 each. How would you feel about making this change?

 

[DVDdoug]

so they've got YUUUGE resonances around 70-200Hz.

Have you checked them outdoors to make sure the speakers are the problem? It's hard to believe they are THAT bad... Or have you tried some EQ?

If you can't fix it with EQ, think about renting some speakers before buying them.

 

[chelgrian]

In a couple weeks I'm bringing some of my audio equipment to a volunteer event where they're taking over around a 600x600 foot (180x180m) convention center space.

Right now, I have some EV ZLX-12BT PA speakers and an active sub. Everything will be set up at one of the columns near the middle with the speakers pointed at 45 degrees on the ground to get some ceiling bounce. This is in fact an upgrade over last year where I had a single offbrand PA speaker (but one with a 15" driver)!

The only problem is, the ZLXs are made of polypropylene, not the stiffest material, so they've got YUUUGE resonances around 70-200Hz. Dr. Toole et al. found that resonances are one of the biggest limiting factors to sound quality.

I was thinking of upgrading to the ETX-12Ps which are made of super solid wood, but they're a whopping $1600 each. How would you feel about making this change?

To be brutal the ETX and anything you could afford to buy are not enough rig for the gig in a space that size. You should look in to hiring specifically for the event.

 

[bachatero]

To be brutal the ETX and anything you could afford to buy are not enough rig for the gig in a space that size. You should look in to hiring specifically for the event.

I should have been clearer, there's no gig happening here but rather a bicycle training camp and a family friendly Spotify playlist. The reason audio quality matters here is to maximize athletic and cognitive performance so a setup with low distortion and hopefully low resonance would be good.

 

[IngMishael]

Are you open to DIY?

 

[rdenney]

I don't think I'd ever use a sub in a large echoey and resonant room. Usually, boomy bass is the problem and a sub isn't the solution. The last system I installed was in a smaller space, but still pretty big, and I used speakers that roll off at 80 Hz. There's still an abundance of bass presence in that room.

I'd also be considering the shape of the cabinet--does it have a horn-shaped waveguide to project the sound straight ahead? That will help cover the distance. The model in my mind is the very traditional Altec A7--very large with a horn waveguide on the 18" woofer, plus horns for the higher frequencies.

I have a Crate PA system that works surprisingly well, given that it's basically crap, in spaces up to 200x500', even with just a couple of cabinets. No horn loading on the woofer, but horns for the higher frequencies. A lot of the pedestal-mounted actives I've seen are for smaller spaces and don't have the long-throw directivity of big-space PA speakers. Again, not so much woofer is needed if the space is resonant.

JBL accomplished a similar kind of directivity using a phased vertical line array arrangement in their CBA series, but I don't think those are large enough for a room that big.

Rick "projection pattern might trump other considerations" Denney

 

[EERecordist]

Good for you supporting events. Do you have many other uses throughout the year to support the upgrade? Professional sound systems have many rental options and systems/parts are often available used at much lower prices than new.

Can you measure the performance of the athletes in detail? It would be a good project to study frequency response of motivational music vs athletic performance. You could switch back and forth between control and test on the frequency response/resonances/distortion. That would be a great scientific paper.

 

[bachatero]

Have you checked them outdoors to make sure the speakers are the problem? It's hard to believe they are THAT bad... Or have you tried some EQ?

I've tried them outside a few times before and they always sound a little funky, like they have a deficiency somewhere around 2kHz, and not even as good as my cheapo Kali LP-6v2s. According to EV, here's what their FR looks like:

But they also have a passive version which eliminates all built in DSP EQ:

Looks like they've flattened the resonances at 120Hz and 600Hz. But they look UGLY to start with, which means the enclosure is contributing significantly to the sound.

 

[chelgrian]

I should have been clearer, there's no gig happening here but rather a bicycle training camp and a family friendly Spotify playlist. The reason audio quality matters here is to maximize athletic and cognitive performance so a setup with low distortion and hopefully low resonance would be good.

To cover that kind of space with any kind of fidelity requires pattern control, which implies a line array or Danley horn system flown at height. Worrying about the properties of small direct radiating
box in a space like that rather misses several large elephants in the room.

 

[Miley_B]

What is the reason for placing them on the ground?
If you’re after any level of fidelity then the direct to reflected sound ratio is important so before changing speakers the first thing I would consider is putting the speakers on some tall wind up stands to get above heads and obstructions, probably the taller the better assuming a common ceiling height for a room of that size.
More height will also help even out the SPL difference between the nearest listener and the farthest although in a room that size with so few speakers this will be of limited efficacy.
Something like this:

Speaker stand

A high quality steel speaker stand with zinc die-cast clamps for professional use. Infinitely variable height adjustment with a hand crank and push button system which prevents an uncontrolled…

www.k-m.de

If you want to step up from that then I would recommend hiring in a much larger and likely very expensive system possibly suspended from the ceiling.

 

[bachatero]

What is the reason for placing them on the ground?

The reason was to avoid a tip hazard from the stands but now that I think about it, they'll be next to a giant column which should help improve safety.

I just did an FR test outside sitting the ZLX on a table and here's what I got:

Looks like it somewhat resembles EV's provided graphs (albeit the "bass" is +3dB and "treble" -1dB) but what sticks out the most is the huge suck out at 1.2kHz. SAD!

Also looks like an upgrade to the ETX might be in order if my gold futures trading pays off next week

 

[drumphil]

To cover that kind of space with any kind of fidelity requires pattern control, which implies a line array or Danley horn system flown at height. Worrying about the properties of small direct radiating
box in a space like that rather misses several large elephants in the room.

This x 1000.

And once you get into spaces measured in hundreds of meters, delay stacks become part of the plan.

Or potentially some kind of omnidirectional centrally located system.

We're getting well into the realms of non trivial, large scale PA systems.

A sub and a couple of full range boxes may as well be a boombox in a space that size.

Depends on what you are hoping to achieve, and what the expectations are I guess.

 

[bachatero]

I don't think you get it. There is no chance in hell a line array system is going to be here, it's a fun volunteer camp thing and I just wanted to optimize the sound quality given the constraints of a couple PA speakers and a sub. Here's a photo from a past edition of where the setup approximately was:

The acoustics here make whatever setup sound a lot better than it actually is and the competition isn't so good. Before 2022, they had a tiny little Bluetooth speaker to one side. You couldn't hear much of anything if you weren't in the right quadrant in the space. 2022 to 2024, it was a single puny Samson PA speaker. That one worked a LOT better but on the loudest tracks at the bassiest notes you could hear it ducking. Now it's going to be 2x whatever I get plus the active sub.

 

[Chrispy]

I don't think you get it. There is no chance in hell a line array system is going to be here, it's a fun volunteer camp thing and I just wanted to optimize the sound quality given the constraints of a couple PA speakers and a sub. Here's a photo from a past edition of where the setup approximately was:
View attachment 461647

Tuning in, that room and your system IMO just aren't a good match especially with lofty audio goals.

 

[drumphil]

Now it's going to be 2x whatever I get plus the active sub.

All you can really do is turn things up until you run out of power. I can't see how a single sub would keep up with four of the top boxes (well depending on the sub I guess!), but it is what it is.

If you walk around and find that in general the tonal balance offends you in some way, you may be able to do something with EQ, or by controlling the rellative level of the subs and top boxes, but there is no real high fidelity solution with that space and those speakers. ¯\_(ツ)_/¯

Will it sound better with the top boxes on speaker stands, or on the ground pointed at the roof? Only one way to find out!

At least if you have three for four top boxes, you can kinda make things the same volume in every direction around you. Subs are fairly omnidirectional, so less of an issue there, just one of keeping up with the top boxes with only one sub.

 

[Oboreal]

Several key points to consider:

• By nature, this space is the complete opposite of one designed for listening. The geometry is poor, reflective surfaces are everywhere, and the roof probably resonates even at modest volumes.
• You should aim to excite the room as little as possible. In a context like this, I’d opt for multiple column-style speakers — they project wide and far while offering better control over floor and ceiling reflections.
• If you want a centralized setup, place four speakers in a star-shaped pattern around the central column and skip the subwoofer. (If you provide your EV speakers that are totally workable even non optimal : see if you can have at least 4.
• You can strap the four speaker stands securely around the central column and create a “safe zone” using barriers or tables to prevent any possible accidents.). You won’t want to push volume levels too high anyway but keep in mind the sound is going to turn into a mushy mess past 10-20 meters from the source. (put your speakers on stands pointing at ears height of the farest people, and avoid any ceiling and floor reflexion as much as possible, it's a bad idea in such a reflective room).
• Upgrading to wooden cabinets doesn’t make much sense in this scenario. A better approach would be to multiply the sources — for example, four speakers per side depending on audience location (ideally the closest possible, the better). You can work around cable routing by using Bluetooth if the distances are manageable. Compression won’t be an issue here.
• More importantly — and you didn’t mention this — you’ll need a master EQ or playback processor with at least 24 bands, or ideally a fully parametric EQ with a minimum of 8 bands. This will help you control the resonances of the room. (the not so perfect FR of your speakers will clearly not be your main concern in this room and diffusion is not hifi : you correct things to sound right in the environnement you're into with the source you have). Also, consider using a spectrum analyzer and a white noise generator to calibrate your system. That, combined with source multiplication, will make the biggest difference.

 

[Mart68]

For a space that massive, I'd rent a PA system. Maybe $500 for the day for something suitable if U.S prices are similar to UK prices.

You know what you're doing so you won't need to pay extra to have an engineer on site.

There's no chance of those rinky dink Electrovoice speakers filling that space, especially once it is full of people.

 

[Oboreal]

Ok, lets try to precise things.

A speaker like the Electro-Voice ZLX-12BT outputs 126 dB SPL peak at 1 meter.

In free-field conditions (i.e., outdoors or with no reflections), sound pressure level drops approximately 6 dB for every doubling of distance due to spherical spreading.

Let’s work backwards from 126 dB to find where it drops to 85 dB : 1 m → 126 dB, 8 m → 108 dB, 64 m → 90 dB, ~90 m → ~85 dB (approximate)
So in ideal conditions, the speaker could thoerically still hit 85 dB peak at around 90 meters away : probably around 70 dB average.

Not that bad for ambiant sound. (It's not a live music event or a dancefloor context) but you will have to low shelf your speakers to avoid them resonate as hell. (no plastic fll range speaker can achieve his max spl in full range mode)

Realistically, you’re probably looking at 30–50 meters max before intelligibility drops below 85 dB — even if SPL is present, clarity will collapse well before that in such a chaotic acoustic environment.

If rental is an option : i will personnally go to 4 powerfull column array like QSC KC 12 :

Compared to point source, a column speaker like the KC12 has narrower vertical dispersion and wider horizontal coverage. This allows it to deliver consistent sound to a broader audience across a horizontal plane while maintaining clarity over longer distances. In terms of sound pressure loss, you’re closer to a 3 dB drop per doubling of distance, rather than 6 dB, as long as you’re within the coupling zone and well within its directivity range.

For a model like the KC12 that delivers about 127 dB SPL at 1 meter, we can estimate that it maintains intelligibility and useful SPL levels between 40 and 80 meters, potentially more with optimal positioning.

In your case, placing four KC12 speakers in a cross layout can create uniform coverage around the central space. Elevating them to ear level and pointing them directly at the audience helps avoid early reflections and improves clarity. Using EQ is essential to control room resonances. You don’t need excessive bass reinforcement unless you want a punchier effect; column speakers already perform well with vocals and background music.

Of course, in theory, the ideal would be either 4 central line array clusters or a multitude of speakers hung overhead. But honestly, for a amateur sporting event where music isn’t the priority, the option of four powerful column speakers (above 130 dB SPL) arranged in a cross shape with eq seems to me like a solution in the top 1 % of what you can find in this kind of event. (It will cost something like 400-800 euros).

​

 

[rdenney]

• More importantly — and you didn’t mention this — you’ll need a master EQ or playback processor with at least 24 bands, or ideally a fully parametric EQ with a minimum of 8 bands. This will help you control the resonances of the room. (the not so perfect FR of your speakers will clearly not be your main concern in this room and diffusion is not hifi : you correct things to sound right in the environnement you're into with the source you have). Also, consider using a spectrum analyzer and a white noise generator to calibrate your system. That, combined with source multiplication, will make the biggest difference.

dbx DriveRack PA-2 with calibration microphone. This is the most capable single device for killing resonances and feedback in a PA system that I know of, at least in the affordable range. It will equalize the system in addition to notching out resonances that can cause feedback. It will provide the sweeps and noise generators automatically.

Rick "and only 1U of rack space" Denney

 

[Krusty09]

If you need a mixer along with eq and peq for cheap you can use either xr18 or 16 and mix with an ipad . It pretty much will have everything you need . You can use the aux/bus outputs and feed the speakers and eq each one individually.

Good luck on your project.