2 x 800W (8Ohm) on 1200AS2 ICEpower, good idea ?

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This design is just an example how to build a horn cabinet for a cone driver, not the ultimate solution (but a well working one). You cross it over to a sub woofer at maybe 120-200 Hz.

The horn has to match the driver, the volume of the chamber behind the driver is most critical. Sometimes designs can be adapted to other drivers, even maybe 2" smaller ones. This will give lower sound pressure with higher distortion. Horn drivers usually have low Qtc of 0.2-0.3 and a very strong magnet. Fs is on the higher side, Vas on the lower.
If you change drivers in a proven combination, you are in unknown territory, until you build, measure and listen in a A/B comparison to a reference design (and then, again, modify...)
2x 8" is quite small for open air and not much cheaper than 10" or 12".
A 1.4 or 1 " compression driver can work and is less critical than the cone driver.
A nice design would take a large horn and place one 10" horn loaded over and under it, as this gives a better result than 2x 10" in a row. More work to build it.
2x 10" is still a compact design in PA therms. Remember that such mid/high combinations have to "fly" over the heads of the crowd. If the radiation pattern of the box, height and angle are correct, you can keep sound pressure even over quite some distance. The aim is that it is just as loud near and far of the stage. Only well directed speakers can do this. That´s why you use horns.
Today commercial products go in the direction of using insane power and lot´s of drivers instead of elegant design´s. The results in the lower price range are often much worse than older, expensive (time!) to build cabinets, carefully designed.

Today´s very good sounding line array´s are expensive and very complicated, as they need basically a lot of speakers, each one with it´s own amp and perfectly tuned DSP. All this adapted to the individual situation. That´s what the big boy´s do...

Have a look at commercial designs, maybe you find inspiration.
 
Also, I'm planning to use this midrange driver between 150Hz and 800Hz, is the horn thing relevant in this case ? As I see the "Off Axis" only starts to go down after 1Khz (same on the 8 and 10inch).

Off Axis.JPG
 
+2dB is a lot. +3dB is two drivers instead of one.

If you plan to cut a 800 Hz this is quite low. Have a look what kind of compression driver and horn (it decides about the lowest frequency produced!) you need to do 800 Hz with opene air PA.
You save 100 € on the 8" and have to throw in 900€ with the CD& horn.

See, you are trying to re-invent the wheel and are in the phase where your prototype is still square. Maybe the start of an idea, but not practical. If you proceed on this way, maybe in 10 years you will start to chop edges off and make it round.

Better to go to some kind of dedicated PA forum and primarily read. Be prepared, these guys are not very patient and may get rude if you don´t talk straight.

PS The "horn thing" is relevant to get the sound where your audience is. Otherwise it goes everywhere. It is like trying to put out a fire by pointing the stream of water away from the flames.... useless.
 
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alright, well the goals are still the same : provide an outdoor coverage of 500/800 people (300 / 400m2).

Thanks so much for your advices, I've modelized this PA now :

GoingTHISWAY.JPG

SUB : 18" THAM
MIDRANGE : 10"
TOP : 1.4"

Planning to build 2 like this, for the Amp, I believe I will go with a Berhinger INUKE series to start. I also know that the top should be at least 2 meter high for good reach in the long distance.

BLESS
 
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This looks like a start. If you put a second 18" cabinet under the single one, this could even be fine. This is quite "old school" but done right can sound excellent.
The "modern" approach is using loads of drivers, but must not sound any better.

The mid high has to be higher than 2 meters, otherwise the sound will be absorbed by the people standing next to the top. Not "only" reach 2 meter.
Outdoor means safety, too. So some sudden wind may not drop the whole stuff on the audience. If you can not drill in the ground for fixing, very often flexible water tanks are used as counter weight, easy to transport empty and filled at the location. ( I had one gig where the music was delayed for 2 hours, because the landlord wanted 20 Euro for 100 litres. We needed 2000l for the stage.)

If you find it hard to realize the mid horn, think of two 10" over and under the high horn. This will give the sound some direction, too.

Building curved horns in 3-dimensions is not easy and will a give a full grown carpenter quite some thought´s. Might be easier to pay a little more for hardware and save weeks of wood building, depending on your skills and tools.

i-Nuke Mk2 is IMO a good amp, even as some people bash them. Because they are so inexpensive, people that never bough amps before, put their hands on them. Which kills quite some i-Nukes. Any amp can fail if mistreated. Most (Semi) pro´s with some experience have no problems with them (I got two).
Usually, if they fail, it is in the first hour of operation, so test them at full load, harder than you plan in operation.
You may use the DSP-version and are done with 3 amps. Saves a lot of wires, hum and other problems. Software is well designed (you can test it without amp) and can manage multiple amps.
 
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Got it !

If you find it hard to realize the mid horn, think of two 10" over and under the high horn. This will give the sound some direction, too

Do you have any design example to show as I can understand how it's supposed to be done well ?

Also I don't plan to build any curved horns but want to keep things straight (unless there is a huge difference in the sound quality / reach)

Danke that's really great help
 
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