Which power amp for these subs?

#2
The first "problem" I see, is what do they mean by "program" ??
Different vendors use program and RMS to mean different things. Peak is peak :)
based on the specs in your link, I believe the AES value = RMS = program, and what they call program = peak!
So, if you apply the standard rule of thumb (allowing for peak and headroom) of an amp being able to deliver 1.5 to 2.25x the RMS rating of the speakers RMS/program value (800w here)...
800 x 1.5 = 1200w
800 x 2.25 = 1800w
An amp that produces from 1200-1800w into a single 18" you listed OUGHT to be OK.

However, you didn't provide the amp link to specs..
So.... Assuming 3000w is the peak power of your amp, and
Assuming a stereo amp with each output hooked up to each sub, EACH speaker will see 1500w (3000/2w).
Assuming bridged mode and speakers are daisy-chained, each speaker will STILL see 1500w.

Either way, you should be OK - based on the assumptions I have made and no more info that you have provided being available.

If you are putting the full 3000w into a single speaker, then YES, you are overpowering them.
The amp specs would help :)
 
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#4
73jbass said:
I have a pair of Ciare 18 subs that I have been using for a couple of years, but I think I have been overpowering them. Rated at 1600 program,and 800 AES (rms)? So can I use a 3000 watt power amp,or something less?

http://www.usspeaker.com/ciare 1800sw-1.htm
Click to expand...

The attached documents give an explanation of AES testing. The AES specs for my JBL 2206 drivers specify 600 watts power handling from 60 to 600 hz. If you look at some of the JBL cabinets that use the 2206, Program is defined as twice AES and Peak is twice Program. I believe EV used the same terminology but they use EIA standards instead of AES. Regardless, literature associated with your speakers should define the terms.

You can use a 3000 watt amp with speakers rated for 800 watts AES, but it is advisable to setup compression and limiting and run the speakers conservatively. Basically you want to keep the peaks under the maximum levels the speakers can take. So the limiter should have as short of an attack as possible and the threshold should be set a few db below the Program rating if that is the highest rating provided by the OEM.

The compression should be setup with a relatively long attack, but a lower threshold. The idea is to keep the average power under 800 watts, while letting shorter transients like bass drum hits pass without keying the compressor. With this sort of setup, if you push a low sustained note above the compressor threshold for longer than the attack parameter allows, the compressor kicks in and drops the level so the amp feeds the speaker less than 800 watts. Depending upon how transparently you set the compressor to work you may still need a bit of awareness to avoid destroying your drivers.

IMHO, running two 8 ohm subs off one bridged PLX3002 should be pretty much ideal. 3000 watts at 4 ohms vs 3200 watts program power handling. If you don't have a speaker processor I recommend engaging the amp's clip limiter and whichever subsonic filter is most appropriate for your subs. If you built the horn loaded cabinet shown with the driver, the 50 hz subsonic filter is probably best. Discretion is still important as the amp exceeds the continuous power rating of two drivers.
 

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#6
73jbass said:
What compression setting would you use as far as ratio and threshold?
Click to expand...

IMHO this is something you should base on how you will operate the speakers, how close to the edge you are willing to push the subs, and how attentive you are. If you want to be super conservative, set your limiter at 800 watts and set your compressor threshold 3 to 6db lower with something like a 3 second attack and an equally long release. If your not attentive run a high ratio so the compressions provide significant protection and is obvious enough to catch your attention. If your one to watch the meters like me, then you can set the compression a bit more transparent so it just keeps the average power a bit below 800 watts.

My processor has three levels of dynamics. I run my sub's output limiters about 1/2 db under the driver's peak power ratings, but my processor is digital and uses look-ahead limiters to prevent overshoot. The output compressors are set 7 db below the limiters with a 3:1 ratio, fast attack and fast release.

Note the threshold is 1db below the continuous EIA power rating. The way I operate the system is to turn it up only until the output compressors starts to regularly engage. As I am operating the system relatively conservatively, I am not overly concerned about exceeding the continuous power rating, but the sub compressors are configured to give me a little visual alarm that they are peaking above their continuous power rating.

The input compressors are set with a longer attack and release, and a 5:1 ratio. They come into play slightly after the sub output compressors and before the output limiters hit. Basically the system starts with soft multi-band compression, ramps up with higher ratio full-band compression, then hits multi-band limiting.

Even if I push the system hard enough to hit the limiters on the subs and low mids, I can't really hear it...the intent is to never operate the current subs at this level for an an extended period of time.

If someone else were going to operate this system. I would drop the sub output compressor threshold and increase the ratio, and probably drop the threshold of the limiter as well. The subs are the weak link in the system for now and the current setup does not provide adequate protection from someone who lacks my discretion....I may be pushing them too hard myself.

I am sure a real pro would have a more scientific answer and maybe some formulas for you. Ultimately it's a tradeoff between the risk of destroying the drivers and a few decibels, so choose your settings wisely.
 
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#7
Thought I would mention I am running PLX3002 amps on my mid horns and super tweeters. I don't know the actual power level/voltage they are limited to as my notes were lost in a computer crash. I believe I limited them below the drivers' continuous power ratings which is 75 watts for the JBL 2445s and 20 watts for the 2405s. The processor shows both are limited to the same threshold and I have never seen either channel hit the limiter. The signal leds on these two amps barely light when the rig is pushed to its limits.

The amps for the subs and low mids are PL340s. The subs are limited to the peak power specs of the driver and low mids are limited just below the clipping limits of the PL340 with a low ratio compressor set 4.8db below the limiter. I believe I did this so the mid bass driver and sub would hit the compressor at about the same SPL for a more consistent sound. I can't say whether the decision is good or band...only I did it for this reason.
 
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