Designing a Loud, Modular, Mobile Sound System

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Hey, so I'm part of the Audio Engineering Club at Oregon State which means we have access to other people's money and lots of free labor. So of course we want to build a large, loud, mobile, and most importantly, impressive speaker system.

None of us have ever done anything of this scale before, so I'm really interest in opinions on our ideas. Our goal is to build something loud, modular, that can be used in both small outdoor and indoor events, and as a marketing tool. Our current idea is to create something with a 22x22 footprint that allows for different modules of speakers to be stacked on a cart of some sort. For example, a sub (or two) on the bottom with mids and highs stacked on top. This modularity allows us to adjust the system for different purposes and add modules as time/funds allow.

As for driver choice, this is where we are still unsure. We love the idea of some massive UM18's but with two of them and matching mids and highs, they suck more power than a standard 15A outlet can give. And if we ever want to move these around, that's maybe not ideal. At the same time, we may not be playing these over 50% power because they're so damn loud. Are ultimaxes a descent compromise between loud PA speakers and low hitting home audio speakers? Are there alternatives that look as cool, use less power and still play in the 30's? Also, we're not sure whether we will need PA mids and highs or we will be fine with regular stuff?

Thanks for any help.
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If you want to play outside with decent volume you will not only want more efficient PA drivers you will probably want to be horn loading them to get even more efficiency. You should work out the size of crowd you want to play for, average SPL (could be up to 110dB in the sub bass region) you want furthest away and peak to average ratio of the music you want to play (6 to 30 dB depending on genre) . Then calculate the 1m SPL your speakers will need to output to achieve this (Sound level distance damping decibel dB damping calculation calculator change distance versus sound level apps reduction drop dissipation SPL sound transmission loss free field loss sound and distance - decrease drop fall sound over distance versus d). As a quick guide a sub bass system capable of 120 dB/1m is just about enough for 50 people playing non super bass heavy music (funk etc).

Most Genres of music don't need response below 40Hz. Its worth doing some spectrum analysis of the tracks you intend to play. You will find that if you sacrifice bass extension relatively loud speakers can be small. For something that is on a small cart I would not bother with <50Hz.
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in general you want to use pa drivers for the entire range.
The Um18 Is designed to reach under 20hz in domestic enviroment, but Will not be as efficent over 30hz as a dedicated Pa woofer. Look for something like b&c 18 sw115 or ds115 or 18 sound nlw9600 , since you have budget.
Be aware that for pa use you want the highs over head level, to reach the people behind and avoid deafening the Frontline, so consider that even while using few modules you Need that height or a way to raise the midtop.
About Power consumption, don't think you Will Need all your speaker wattage from the wall. Music Is Dynamic and average Power consumption Is often quoted at 1/8 of Power, that Is you Will Need around 125 real watts to push a 1000 watt speakers to the limits.
This Is overgeneralizing and depends on amplifier technology (go for class D, up to 90% efficency), speaker and program material, so don't worry too much about Power until your rig grows really big.
I heartly suggest you Plan your System as It Will be in the finale stage and move backwards from there, if you Plan small and than multiply the Pieces It Will not sound good. For example of you want One midtop per side you Need Wide dispersion, but if you Plan to have two midtops per side then you'd be Better served with smaller dispersion midtops that Array Better, as arraying Wide dispersion speakers Will cause comb filter issues.
FishNChips, you're a bit all over the place.

You say large and loud, and then you also say 22x22" platform, and only a couple of 18"s.

In the PA world, "large and loud" starts at 4x18"s a side, and goes up from there.

I'd recommend you decide exactly what this system needs to do, and go from there. It's all well and good being able to spend someone else's money, but if nobody agrees on the goal, how can you tell that you've succeeded?

What do you have in the way of amplification, system processing, and measurement gear?

I'd recommend you decide exactly what this system needs to do, and go from there. It's all well and good being able to spend someone else's money, but if nobody agrees on the goal, how can you tell that you've succeeded?


I guess I'm interested in what it would actually take to do a PA system well and then kind of dial back our needs from there. Yeah, I actually agree that to goal is not clear. Previous years wanted to be able to play for 50 people at high volumes, where I'm more interested in impressive sound quality and low end. I was kind of hoping able to find a happy medium between the two, but as I understand more about PA systems, that seems less realistic.

In the PA world, "large and loud" starts at 4x18"s a side, and goes up from there.


Well, early on we will only have the ability to build something with a couple subs, but the hope with the modular design is to be able to add subs right on top.

What do you have in the way of amplification, system processing, and measurement gear?


As far as gear, we have nothing for amp's, processing, or measurement gear yet. Just with some early stage planning we were considering a couple of crown xls, but not sure about processing or if a simple RTA mic would suffice.

And thanks for the info guys. Never though about how tweeters need to be above head level and such. Super useful to know the standards like 120db is good for 50 people. We have no experience in this area, so this stuff helps us to get our bearings.
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The common PA setup of 1" compression driver/wide pattern horn + 12" woofer main + 2 x 18" subwoofers (bass reflex) would meet your needs I think. Of course there's other ways to skin the cat. I would recommend a subwoofer design that can get down to 30ish Hz - the low string on a 5-string bass is 31.5Hz and electronic music sounds much better with that low extension. But then the box gets big so there's a trade-off there.

The advice about getting the main speakers up overhead is spot on - you will want stands. Build subs with wheels so you can roll them around - you will want to be able to put them in the best place, indoors or out, and that will probably not be one under each main. Having everything fit on a small cart will be unnecessarily limiting IMO.

Are you planning to design from the ground up or are you willing to build an established design? If you want to build an established design check out Art Welter's SynTripps + Keystones - a very cool and capable system.
Hey Fish;

I don't want to sound negative but I have a suggestion since by your questions you don't sound like an engineering student, don't sound like a serious audio hobbyist and don't sound like you have done much if any homework. Sorry, this is just how this reads to me.

Take some field trips and get out in the world and see what looks and sounds like what you are want and then dig in to see what makes it work. Reverse engineering is an art.

Will your source be live music or recorded? Both?

As others have said, you can get a lot done with a single 15A 120V circuit.

All the best.
Okay, it's getting clearer.

Here's what I'd do in your situation:
- Get a measurement setup. I'd recommend a Behringer UMC202HD and a Beyer MM1.
- 1x Powersoft T604
- 2x Faital Pro 10HX230
- Add subs until you're happy. If you want 30Hz, a couple of 18"s per side should get you somewhere decent.

This is maybe not the right forum to ask this kind of setups as they are not really into this as far as i see.

But there is a whole subculture of 12V soundsystems out there, and they use high efficient pro audio drivers with car amps to get a few hours of music out of car batteries. They are all on a lorry that you can push arround and play often on markets and on the side on festivals. There are many worldwide, those here in Belgium that are known are Serendipy Soundsystem and Bangarang Sound Station, wich both play mainly reggae.

Bangarang uses a 15" cubo sub, and 12" midbass wideband and a 1" compression driver, all powered with car amps and a dsp as crossover i thought. Serendipy is all recycled material, but i don't know his exact setup (he is a bit an outsider concerning setup in that scene, but very high rated).

It's doable to do a small party outside, but don't expect pa levels or the best sound in the world, this kind of setups have serious limitations, because of the limited space and power.
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I would first determine for how many people the system should be designed and at what distance are they listening of course. Then I would begin to make needed calculations for the SPL needed.

Well .. I have a story for You all, if it helps.

Some years ago I visited a car-show / fair, and when I was at the entrance I could hear Bum Bum. Well I thought there was a band or large PA playing on one of the halls...

We visited the fist, the second hall and Nada... but the Bum Bum was increasing.

On the third hall at a corner was a Ferrary Or Porsche equipped with 4 or 6 subs in the trunk and an Alpine system... I wonder what power was installed there. I remember seeing a wire plugged into the wall harness, so it wasn't running of batteries.
taking an armchair approach (I'm old - no real PA experience and not played bass for over 25 years) - if a solid 40Hz is good, then consider Jim Bell's "Single Sheet" tapped horn (aka "SS15") in multiples with appropriate 15" speaker having a good 8-9 mm xmax minimum. There's a good plan by TB46 (who we assumed passed away some time ago)

Also, look at Matthew Morgan J's Facebook "High Order Quarterwave Society" entries for a variety of super-planar types.

FWIW here's a sim of six SS15 in half space with the old B&C 15PZB40 spec

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