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Old 14th July 2010, 09:26 PM   #21
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Quote:
Originally Posted by chris661 View Post
ElectroAudio - there's some mistake with that datasheet. The watts out when running at 13A@230v = 2250, with 763 watts being lost as heat.

The rated power is 18,000watts, sure. But it's never ever going to get there unless you use an alternative power supply.
Well, 2250watt x8 = 18000watt so it is correct...

The thing is that it is 18000watt peak, like in the initial kick from a kickdrum, or in this case from pinknoise with that powerdistribution, not continously because that is 2250watt.
1/8 is a common number among many producers since that is supposed to be like music.
-I think JBL has some papers describing this somewhere on their homepage???
Well, i found something...

http://www.jblpro.com/pub/electronics/mpa_man.pdf

Quote:
Originally Posted by JBL MPA Manual Page 9
All major safety agencies around the world measure amplifier current and temperature rise under the same “normal operating conditions” using a pink noise signal with an average power equal to one eighth of maximum power. This was in response to industry complaints that the former test level of one third power was unrealistic for high-quality professional amplifiers. To put these levels in perspective, music played at one third average power will be in a state of constant clipping, and this power level is about the greatest one can obtain without completely obliterating the program under clipping. The one eighth power level is about as loud as you can play music while making some attempt to avoid obvious clipping. We had to satisfy the following conditions:
1. Meet the safety agency requirements for “normal” current draw.
2. Remain within the functional limits of the plug for “severe program levels.”
3. Avoid unsafe conditions at full output power.
The AC consumption for each power level and load impedance is shown in
Table 1 and Table 2 (see pages 9 and 10).
The safety agencies are concerned with the current levels shown under the one eighth power column. This is because building codes prohibit the connection of a single load which exceeds 80% of the capacity of the branch circuit.
JBL Engineering standards call for ability to operate at one third power, in order to meet the demands of “worst-case” heavily compressed, clipped program material.
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Old 17th July 2010, 03:50 PM   #22
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To answer your questions Chris:
The budget will essentially be student loan/job/ebaying stuff/grant from uni, so its quite tight; but the plan is to just slowly pour money in, aka buy parts at a time to slowly build up the system.
The plan is to also not skimp on parts, it will take longer but we will be building high quality horn loaded speakers, amps (41Hz for all but really high power) and the crossovers.
We've been looking at the designs on speakerplans.com and freespeakerplans.com, both are good for these sort of speakers, but still I want to be able to design my own, eventually.. So I've been reading through these articles:
http://www.audioxpress.com/magsdirx/...olbrek2884.pdf
They're pretty good, although it will take a while to get used to all the equations and calculations.
As for the Audience/area, for a lot of it we will be using the rig at field raves around Sussex campus; theres already a huge free party scene, so getting into this scene and getting people to come won't be a problem at all. I have a friend who knows the people who currently throw most of the raves, who I should meet soon and discuss some sort of joint effort/ multi rig rave!
As for the Size/weight, I think I need more info from the above person on the way he transports his rig before I can answer that!
Cheers,
Will
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Old 18th July 2010, 04:00 PM   #23
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Good that you're going to talk to more experienced people - that's the way we're meant to learn. I know what you mean about the slowly pouring money in idea. My stereo has been in the making for 3 years now, starting cheap, but slowly buying more expensive stuff.

I'm glad you're going with the 41Hz stuff - from my experience of them, they make some really good stuff. The 900w/ch into 2 ohms from the amp7 will probably be sufficient to get you started.
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