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Old 10th January 2017, 04:37 PM   #1
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Default Amp for high power mobile PA

Hi,
we need a system for outdoor speeches and ralleys. Budget max 2000 Euros.

These are the targets:
  1. Be able to have very good voice transmision (for speeches) to about 300 people outdoor
  2. Play background music in acceptable quality (no dancing loudness needed)
  3. Have the whole system transportable on a trolley. It doesn't have to be small and light, just transportable by attaching to a bicycle or pulling by hand.
  4. Have enough battery for 1-2 hours of mobile use
  5. Optionally, but desirable: A system that is expandable, e.g. by adding additional speakers and a generator for larger events.

First one is most important.

Current plan is the following:

A) Two good full range PA speakers, e.g. 500 Euros each
B) AGM battery, e.g. 120AH for 120 EUR
C) Efficient Car Hifi Amp - 500 EUR?
D) Mini mixer, cables, charger etc - 200 EUR

Now, the big question is:

Is this the best way forward?

Other options considered included:

- bying an off-the-shelf system (e.g. Foohn Audio, or dB Opera Mobile). We think that our current plan gives us more bang for the buck.

- building something along the lines of the boominator (self-build speakers with full-range chassis, tda-something amp boards, 12v gel batteries) - however, we fear that without extensive expierence (which we don't have) it will not deliver the level of voice quality and loudness we strive for

And, should we continue with our plan, the actual purpose of this post:

Do you have reccomendations for a A) full range PA boxes and B) a car hifi amp that can power these?

We're thinking of e.g.:
2 x Electrovoice ELX 115 (8 ohm, 400W RMS)
or
2 x HK Audio L5 112 X (8 ohm, 350W)

(these were recommended by someone we know when asking for speakers that deliver good voice rendition - we're open for other suggestions)

and then, for the amp:
Alpine PDX-F6
(2 x 300W, but at 4 Ohm only..)
Sonora Combo 2S300
(2 x 300W at 4 Ohm)
If we'd bridge the two speakers (mono would be OK) - would that work out?

Do you have other suggestions for high-power 12V amps that work on full range?

Most monoblocks seem to work only up to 400 Hz, are there full range monoblocks?

Best regards and thanks in advance,
obliquemaria
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Old 10th January 2017, 08:37 PM   #2
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This is a "brute force" method using big battery and amp, it does the job but is fairly heavy...
I run a Pioneer GM-D9500f on a 60ah SLA and get 6 hours of "flat out" use, so you could maybe think about a smaller battery.
Small tips, get the speakers up high and try to use a small mixer in to the amp. There are some battery powered mixers out there, for your mic input.
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Old 10th January 2017, 08:51 PM   #3
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Why not use active speakers?
JB Systems make some cheap but for this kind of applications decent speakers: https://jb-systems.eu/psa-15

The advantage is that you can use more speakers to have a better spread.
You mentioned battery powered - is that because you don't have mains power on that site? If so, maybe consider using a small diesel generator?
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Old 10th January 2017, 08:58 PM   #4
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A silenced Honda 2kW generator is the same weight and cost as a couple of decent batteries! All it needs is fuel.
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Old 10th January 2017, 09:34 PM   #5
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Quote:
Originally Posted by delange View Post
Why not use active speakers?
JB Systems make some cheap but for this kind of applications decent speakers: https://jb-systems.eu/psa-15
That's the same ODM as McGee..

Aktiv-Lautsprecher McGee, 500 W - Unterhaltungselektronik - Lautsprecher - - Pollin Electronic
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Old 11th January 2017, 08:35 AM   #6
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Generators are too noisey and smelly to use amongt a crowd, and also draw negative attention
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Old 11th January 2017, 12:23 PM   #7
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Thanks everyone.

We do already have a generator in reach for bigger events, but we do want a battery powered solutions for this, that's requirement no. 1.

As I said, weight is not too much of an issue, the whole thing will be installed on a trailer, so 60-80kg total should be OK (20kg battery, 20kg each speaker). Lighter is better, of course, but we don't want to trade in power for lightness.

Regarding active speakers: That would mean we need 120 or 220V, right? We were told that transforming up loses more power than the possibly more efficient amps in active speakers gain us, that's why we're thinking of going the car amp route.

Back to the original question: Any suggestions for

a) passive full-range PA speakers with great efficiency (spl) and great voice rendition for up to 1000 eur / pair?

b) a high power, efficient Class D 12V amp to power these speakers?
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Old 11th January 2017, 01:16 PM   #8
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Addendum: With "efficiency" for a) I mean SPL/W/m, that's more important I think - though a max SPL of 125-130db would be good, to be able to use the system for bigger events with a regular amp and generator or normal power (and possibly two subs which we could easily rent when needed).
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Old 11th January 2017, 07:53 PM   #9
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If your goal is a maximum of 2 hours of use, you could use a bank of 18650 batteries for power. This should reduce your weight quite a bit. Also, you could have back-up batteries to replace in the field in case you run out of juice early.

A typical 18650 battery should be able to supply 1A for longer than two hours. The voltage will drop from a bit more than 4V down to 3.5V during the discharge, but most modern Class-D amp boards can handle that kind of voltage drop without any problem. Making your own 18650 based Li-ion batter pack takes some DIY work, but you can also buy a 24V 12Ah Li-ion battery pack for about $300. (They do sell some 24V 40A Li-Ion battery packs for $400 on eBay, but specifications are highly suspect).
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Old 16th January 2017, 04:00 PM   #10
ICG is offline ICG  Germany
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Quote:
Originally Posted by obliquemaria View Post
and then, for the amp:
Alpine PDX-F6
(2 x 300W, but at 4 Ohm only..)
Sonora Combo 2S300
(2 x 300W at 4 Ohm)
If we'd bridge the two speakers (mono would be OK) - would that work out?
On 8 Ohm (usual PA speakers) you get only ~half the power output. That means you would not use the potential of the amps or in other words: 3dB less output. And that's unfortunately the same for every car amp, they are often optimized for 4 Ohm or even 2 Ohm. You can get cheaper amps for the same power on 8 Ohm.

Quote:
Originally Posted by obliquemaria View Post
Do you have other suggestions for high-power 12V amps that work on full range?
Well, if you want to stay at batteries, you could take 2 or 3 in series (or a truck battery) and use 24 or (3x12) 36V and use a class D amp or use a step up converter (DC-DC converter) with a 12V battery. A good amp for that use would be i.e. a TAS5630, they are not very expensive.

Quote:
Originally Posted by obliquemaria View Post
Most monoblocks seem to work only up to 400 Hz, are there full range monoblocks?
Yes, but no car-monoblocks.
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