Sizing amps for speakers

[tk2k]

Hi all,

Quick power amp question. I know this comes up a lot but I want to make sure I've got this straight

Peak power = maximum power required to move from from forward most to rear most position
Program power = 'normal' maximum power draw when playing music?

So, I have a pair of Danley SH-100B's 800 continuous 1600 watts program http://www.jmsmarketing.com/component/rsfiles/view?path=Catalogs/Danley-Brochure2011.pdf page 20

And I'm trying to size an amp for the pair, but the speakers don't list peak power usage. I know that's 2x the RMS, but the speakers don't list that either, so I'm a bit confused.

I was thinking of an RMX 5050 as that puts 1800 watts into 4ohms? Or do I need more overhead?

Application is general live sound.

 

[DuckJordan]

actually no, it does not mean 2x RMS, it looks like 800w is what it will need normally, with your high pops and thuds close to 1600w. A good size amp would be right around the 1600w range at 4 ohm. Make sure you have a limiter in your system, those danleys aren't cheap

 

[tk2k]

actually no, it does not mean 2x RMS, it looks like 800w is what it will need normally, with your high pops and thuds close to 1600w. A good size amp would be right around the 1600w range at 4 ohm. Make sure you have a limiter in your system, those danleys aren't cheap

Ah, I was under the impression that it was about 2x, my bad.

Alright so the RMX 5050 should be a fine fit, with 50ft cables and 14 gauge wire my power drop should be at least equal 150 watts of power drop, right? so very little limiting needed?

 

[DuckJordan]

the limiting doesn't bring the power down unless you would damage the speakers. You don't have to use a limiter but I highly recommend it.

 

[tk2k]

Sure, it's all through a digital console so I can set a limiter, I'm just trying to figure out an aproximate setting since I shouldn't be in too much power danger, and my amps all have clip protection

 

[JohnD]

Hey tk2k, I don't know if you are aware of this, but Ivan Beaver of Danley Sound Labs is a frequent poster at both prosoundweb.com and soundforums.net. It might be worth signing up at one of those and PM'ing him. It is always good to "know a guy at the factory" Or just give danley a call.

 

[gafftaper]

You can't just dismiss the 2x rule like that. It's been a widely followed rule of thumb for years for a reason. Although I don't claim to be a sound expert, I do know that headroom is a very good thing to have. In my experience it depends a lot on the Amp/speaker combination. Some speakers are a lot more thirsty for power than expected. Some Amps just don't have oomph that the rating on the box would suggest. I personally believe that most RMS and Continuous Power ratings are made up by the marketing department in order to just make the power rating chart for the product line look nice in the brochure. We put in a 20" JBL sub powered by a QSC amp at my old black box. I don't remember the ratings as this was about 6 years ago, but their ratings were "perfectly matched" for each other according to their web site spec sheets. We installed them and the sub immediately started barking on the deep notes. I replaced the amp with one nearly twice the rating of the speaker and the sub ran smooth as glass. I would either: contact Danley and ask them if they have a suggested amplifier to match your speaker, find a good sales guy who knows your speaker to help you choose a good matching amp, or simply buy an amp from a quality manufacturer with 1.5 to 2 times the rating of the speaker.

 

[museav]

A quick summary. the continuous power is the power a speaker can handle before failing when a specific signal is applied for a specified period of time. That is typically the only rating that is actually tested and measured. But keep it mind that it represents when the speaker failed, it does not tell you how the speaker failed (was it fatal or did recover to live another day) or what happened before failure (did it just keep getting louder, did the response change, did it start sounding like crap, etc.).

The test signal most commonly used for speaker power testing is intentionally manipulated to have a 6dB crest factor, thus the "Peak" power level for the speaker assumes the same +6dB or 4X above the continuous rating for the Peak power rating.

The Program rating is a sort of "hey, real world content is usually somewhere between those two extremes so let's make up something to represent that" and is thus usually assumed to be midway between the Continuous and Peak power ratings, thus +3dB or 2X the Continuous power rating.

"RMS" power is a technically incorrect form of saying Continuous power. The Continuous power Wattage value is based on the RMS voltage and current thus some assume it to be RMS Watts and power but that is not technically correct, it is just Watts and power.

Using an amplifier rated at 1.5 to 2 times the Continuous rating of the speaker is a rule of thumb developed for situations where it is assumed that you want to get as loud as possible with some reasonable degree of reliability. That does not mean the speaker system will be loud enough or that it might not be too loud, just that you are getting as much as you can with some reasonable safety factor.

Indirectly related, remember that with the vast majority of amplifiers an X Watt amplifier is an X Watt amplifier regardless of where you set the input level controls. Turning the input level up or down does not change the potential output of the amplifier, it simply varies the input signal level required to get that full output level. This can be important as say you have a 1,000W amplifier and a 500W Program rated speaker, then turning the amp levels down will not make that 1,000W amp the desired 500W amp and if somebody does something like drop a microphone you may still see the full 1,000W output.

If you call Danley I'm sure someone there can give you a recommendation. Being nearby I've gotten to know Tom Danley, Ivan Beaver and Mike Hedden pretty well and they're usually very good about such questions, they're also the kind of folks that if they don't know an answer about their products it will likely make them want to go and find out just to satisfy their own curiosity.

 

[tk2k]

Thanks everyone,

They reccomended two rmx1850hd amps in bridge mode, nice affordable yet reliable solution in their opinions.