Monitoring voice-coil temperature

You're paranoid.

 

But the temperature rise would occur so fast that you couldn't do anything anyway.

And, although your setup exceeds the "2 x power" rating, you'll be safe IME, since you never use the full power over a longer period of time.
You'll hear clipping before anything happens anyway IME.

 

It is possible that the Acme cabinet is not very efficient. It may require a large amount of power to produce the volume that you are trying to produce. That may be why your amp is clipping.
According the Acme's website the sensitivity of the Low B-2 is 93 dB 1W/1M. It takes takes twice the power to increase volume by 3dBs. Many bass cabinets have a sensitivy around 99dBs. It would take 4 times the power going the Acme to produce the same volume as a cabinet with a 99dB sensitivity.
On the other hand, Acme cabinets tend to go lower than many other Bass cabs on the market. For example the freq response is 41hz-22kz for the Acme Low B-2 while an Ampeg SVT-210HE has a freq response of 58-18KHz (but a sensitivity of 97dB).

 

it might be easier to monitor average power into the cab if you really want to "see" it. maybe ask around on some electronics forums or maybe www.harmony-central.com forums?? I'd be curious too! but possibly the easiest way to know if you're pushing too many watts is to know when distortion is happening in your speakers and turn them down at that point.

let me know about the watts meter.

 

How long do you usually play?

 

Nexo make PA systems that revolve around a processor that monitors the voice coil. Well not really, it's actually a simulaion based on a computer algorithm. The result is really small PA's that can blow away really big PA's.

The technology is very new and very expensive. And it will only work on Nexo speaker cabs (I believe they're loaded with B&C speakers.

Have you thought about Polyswitches? Though with that amount of watts, you'd probably need too many to make it feasable.......

 

My daughter's band played a car show in Bakersfield last weekend. The sound folks did the PA system the old fashioned way: brute force. There were (12) 18" subs, 6 on each side of the stage, and each sub was powered with its own Crown Macro 2400 amp. The mains were flying high from masts as an angled array. There were three Mains in each array on each side of the stage.

Ambient was 107 degrees, so I'm sure the voice coils were hot. You'd never know it from the chest hits those subs put out.

IMO, it is much easier to add more speakers, so each gets half its rated power capacity. This combination will be louder overall by avoiding power compression due to over heating.

 

They're made of a polymer that partially melts when overloaded, restricting the current if overheated. As soon as the current is reduced or removed, is solidifies again and restores the original signal. All this happens in a split second.

I've never used them and to be honest they look like they're designed more for low powered, Hi-Fi applications. And they won't protct against mechanical overload which to be honest, is probably more of a concern in your case.

 

Full power means full heat on the voice coils. You will get power compression for sure, at least -3dB and probably more. I'm not at all surprised they sound better at a lesser input power.

My rig lives in the back of my Toyota pickup truck and never enters the house. Too big. Too much of a pain in the butt to load/unload between gigs.

 

so there aren't any thieves in Sacramento. Interesting.

If I tried that, my gear would be stolen quicker than you can say "pawn shop".

 

First, keep it ugly.
Next, keep it hidden under something ugly.
Keep it in an ugly truck, preferably unwashed.



Last secure the tail gate inside with a big chain and lock so it won't open. The gear is too big to get out the lid, so they'd have to remove the entire shell to get the gear out. The shell removal bolts are blocked by all the gear.

 

If you're worried, get a reasonably-powered amp with built-in clip-monitoring limiters and leave them turned on.

 

you might want to check out those polyswitches. They seem like a pretty good idea. They'll protect against temerature, voltage and current. By the way, does anbody know the equation for figuring wattage by current and voltage?

 

Power (in Watts) = Potential Difference (in Volts) x Current (in Amperes)

So P=V*I

Is that what you needed?