Help me figure out my PA speakers.

[spasticteapot]

I'm assembling a PA for use at impromptu desert dance parties. I currently have:

- 2x Dayton PA465S subwoofers
- 2x Faital 12PR300 woofers
- A Crown XLS 402 (mids?) and QSC RMX1450 (subs?)
- BSS Soundweb 9088 (it was $50.)

It is, for the most part, pretty conventional stuff. I was looking at putting the PA465s in the recommended ~6.5cu. ft. ported boxes and the 12PR300s in some ~1.5 cu ft boxes tuned to about 80hz - they'd be useless without subwoofers, but they'll fit in the front seat of my Mazda. Obviously, I'll need some compression drivers and horns - suggestions?

The other question is one of amps. I could go passive on the tops to save weight and simplicity, but it would greatly restrict either the crossover point or power handling. Alternately, I go buy a Behringer iNuke 6000 and go 3-way, which is increasingly tempting.

Finally - how do I figure out how big a generator I need? PFC is legitimately an issued with cheapass borrowed generators.

[Sydney]

Re: Help me figure out my PA speakers.

A possible concern ( of which you may already be aware ) is amplifier instability.
Not having attached these particular amps to any generator; I have heard of problems with some amp typologies on gensets.
I'd use the UL listing and add a safety factor ( for in-rush ); this is S.O.P. for estimating load as listed by Honda.

[wg_ski]

Re: Help me figure out my PA speakers.

The amp that I'd be worried about using on a genny is the iNuke. Cheap (non-PFC) switching supplies wreak havoc - not to mention that Behringer anything isn't going to have much design margin to handle power surges. Your mid/hi amps shouldn't be any trouble if it's big enough. Size the generator for the max sine wave current draw of the mid and sub amps, not the 1/8 power "nameplate rating". You can do that with a bigger diesel unit, but those Hondas just don't have enough energy storage to do so. Every THUMP THUMP THUMP draws the full sine wave current and can make a small generator unstable. I used to occasionally run up to 2000 watts of audio off a genny. The 2.8kW unit would get unstable (it would surge, and the voltage and frequency would be all over the place), the 5k ran perfectly.

[Brian Steele]

Re: Help me figure out my PA speakers.

This is how I power my impromptu PA:

1 Alpine PDX-M12 for the bass (1.2kW into 4 or 2 Ohms)
1 Alpine PDX-M6 for the tops (150Wx4)

...and if I need the extra run time, 1 deep-cycle marine battery connected in parallel with the car's battery :-).

The processing unit is a Pioneer PRS80 that provides EQ and X-over duties, and numerous input options.

[spasticteapot]

Re: Help me figure out my PA speakers.

The amp that I'd be worried about using on a genny is the iNuke. Cheap (non-PFC) switching supplies wreak havoc - not to mention that Behringer anything isn't going to have much design margin to handle power surges.

Better question - what's the odds I'd kill the generator in, say, an RV?

[wg_ski]

Re: Help me figure out my PA speakers.

You probably won't hurt the generator - at least not before something elese cries 'uncle'. If you pollute the line with harmonics, it will run the gen hot, but the real problems are created for the rest of the loads, not the generator itself. The heavy intermittant peak loads won't blow anything up, but may drive the speed regulator nuts unless it's a bigger engine than you "need". Which gives you the wildly varying voltage and frequency. Nothing plugged into it (amp or otherwise) will like that very much. Transformer amps are bad enough - they don't like it much when the frequency falls much below 50Hz, but do ok with voltage spikes because the trafo filters them. Switchmode have even higher harmonic currents, respond even faster to musical peaks, and a 10% overvoltage can send them to the grave. Some have undervoltage lockout, which can just shut them down on poorly regulates lines.