Another mobile sound setup question

[djrockett]

Hello all,

So, we have to build a "mobile sound system" which would be installed in a used shuttle bus. The use will be a free dance project, promoting dance and dance therapy.

The vehicle would pull up to a parking lot or other outside location.
We are building pneumatic lifts in the 4 corners which will lift 4 speaker towers up out of the bus.

2 people have suggested 5000 watts will be enough, running at 3000 with the extra for peak.

The question is, do we build on automotive audio platform or pro sound equipment?

Thanks in advance

Darren

[Paul O]

Use pro audio amplifiers and drivers, car audio drivers are are far too inefficient and the DC current demands for 12v amplifiers gets expensive very quickly. Then forget putting a watts target on the project because it is irrelevant, the more efficient your speakers the less power you need to achieve a given SPL, so SPL at a certain distance is the target you want to set.

[Brian Steele]

Use pro audio amplifiers and drivers, car audio drivers are are far too inefficient and the DC current demands for 12v amplifiers gets expensive very quickly. Then forget putting a watts target on the project because it is irrelevant, the more efficient your speakers the less power you need to achieve a given SPL, so SPL at a certain distance is the target you want to set.

I'd agree re the use of pro audio speakers rather than car audio ones, but the choice of amplifiers really boils down to how you intend to power them, i.e. off of the bus's supply (in which case I'd suggest an extra battery bank with an isolator to ensure that there's enough juice to start the bus, or an external generator. With the former, class D car audio amps may be the way to go, with the added advantage of no noisy generator to have to set up before each gig. You can literally "stop, drop and run" if necessary

[Sydney]

...We are building pneumatic lifts in the 4 corners which will lift 4 speaker towers up out of the bus.

2 people have suggested 5000 watts will be enough, running at 3000 with the extra for peak....

As mentioned: it's not really a matter of power consumed but rather what you can get from the power, and SPL required.
As a point of reference I used 4 high efficiency 12's and 4 horn tweeters for a mobile sound platform in the county's annual parade, driven with a 12V based amplifier.

[djrockett]

As mentioned: it's not really a matter of power consumed but rather what you can get from the power, and SPL required.
As a point of reference I used 4 high efficiency 12's and 4 horn tweeters for a mobile sound platform in the county's annual parade, driven with a 12V based amplifier.

Hi Sydney, So should I assume that would be a 4 ohm setup? Did you buy 4 ohm pro speakers or use automotive brand stuff... The horns I gather would be pro stuff..

Darren

[Brian Steele]

Hi Sydney, So should I assume that would be a 4 ohm setup? Did you buy 4 ohm pro speakers or use automotive brand stuff... The horns I gather would be pro stuff..

Darren

4 ohm pro audio drivers are available from Eminence and B&C as far as I know. You can also use paralleled 8 ohm drivers to bring the impedance down to 4 ohms.

The car audio stuff as mentioned before tends to not be efficient enough for this type of use.

Questions:

What's the size of the intended audience?

How much space is available on the bus to give up to speakers?

How loud do you want the system to go?

How low do you want the system to go? What type of music do you intend to play back on it?

What's the budget?

All these questions are really the ones that need answering as part of planning the system.

[djrockett]

4 ohm pro audio drivers are available from Eminence and B&C as far as I know. You can also use paralleled 8 ohm drivers to bring the impedance down to 4 ohms.

The car audio stuff as mentioned before tends to not be efficient enough for this type of use.

Questions:

What's the size of the intended audience?

How much space is available on the bus to give up to speakers?

How loud do you want the system to go?

How low do you want the system to go? What type of music do you intend to play back on it?

What's the budget?

All these questions are really the ones that need answering as part of planning the system.

Hi, Brian,

Audience size might be 30 - 200 crowding close to the bus.
Crowd may grow (if we set up outside Fenway Park before ball game we might get 1000 come around..)
There might be background noise such as traffic/city.

The automatic risers are 2' x 2' square and 48" total height available.
4 of them, 1 in each corner
weight up to 300lb. ea.
Also 2 spots available at bus floor level to mount low woofers/subs, with opening panels on each side of bus estimated size avail. is 36" x 36"

Only 2 risers are planned for install at first. If we see we need to have sound 360 degrees, will add the other side 2 risers.
Same as low/sub woofer, only one side (one ) at first.

System should run up to 4 hours, but expected use is 1 hour.

Loudness should be good for Electronic/R&B/TOP 40
Purpose is to get people to find their groove, especially those that never dance

We will have volunteers from local dance schools getting into the crowds to encourage people...

Budget target $3000 - top $5000

So the bus pulls up, the risers pop out of top, the side panel opens, LED lighting starts and the show starts. All within 2 minutes of parking.

[Sydney]

Hi Sydney, So should I assume that would be a 4 ohm setup? Did you buy 4 ohm pro speakers or use automotive brand stuff... The horns I gather would be pro stuff..

Darren

Yes Total 4 ( 8 ohm ) cabs ( wired par ) on 2 amp channels ( each channel had a 4 ohm load ) - each cab approx 97db 1 watt sen. These were "pro" drivers.
As these were pro 12s, they traded low frequency extension for sensitivity - needed a Sub.

[Paul O]

Here is one of my sound systems that has been "vehicle mounted" if you like. LOL. It ran off a 4000w honda generator which was sufficient to make a lot of noise but not quite enough for full warp volume, but even with that I bet it was generating upwards of 130dB. With a bus you have lots of room underneath the passenger cabin to install a compartment big enough to house a generator, you are simply not going to hear it with with music playing at any volume level.. these inverter generators are rediculously quiet.
These speakers may be a bit large compared to what you were thinking.. or maybe not I don't know, but IMO the fewer number of drivers used the better sound quality is achieved. With that that in mind I'd suggest buying fewer high quality pro class drivers like perhaps B&C TBX or RBX 18" subs, some large 2" exit compression drivers and horns and 12" or 15" mid/bass drivers. You could probably get away with a single dual 18 sub and single driver 12+2 or 15+2 tops, these big dual 15+2 tops are overkill for many things I do with them, they have enough output to keep up with 4 double 18 subs just to put it in perspective but they do sound amazing loafing along at 100w or so input.

[djrockett]

Thank you Everyone! Paul, thanks for the info and pic.... I will post pics and specs as we go along.... Spring timeframe

[Sydney]

...Also 2 spots available at bus floor level to mount low woofers/subs, ...

Noted that - It is advantageous to have the subs as low to the ground as possible - a big drop in level when lifted.
( btw: Your budget is much larger than mine was )