matching amp with speakers

Re: matching amp with speakers

Michael Smithers said:
Just curious why you recommend long term RMS limiting to half AES or IEC power? I thought the AES (or IEC) power test was fairly conservative anyway?
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Hey Michael,

Tim and Art have touched on the majority of it. What it comes down to for me is two things:
a) I would like to avoid major power compression.
b) When I say "500w" to the limiter, what does that actually mean? Is it "loudspeaker industry watts" or real watts? Hopefully the former!

Anyway, the AES test is only conservative as a guide to amplifier selection, in terms of comparing power handling it is a pretty good guide. Powersoft has a very expansive document to explain their limiter design, which I have attached below, and can help in understanding. In short, entering 1/2 AES "watts" into their limiter will likely keep the loudspeaker safe, out of severe power compression, and hopefully not sounding too bad either. Good woofers are of course better at this than normal ones, but that's one thing you cannot read off a spec sheet. Just because a loudspeaker can survive 1000W AES doesn't mean you'll want to use it within 6dB of that number.

P.S. Technically pink noise has an infinite peak to average ratio. Like most signal seen by loudspeakers, you can pretty much bet on 12dB crest factor by the time it's gone through some phase shift either due to that inherent in the speaker / enclosure combo or the LPF / HPF in the processing. Unless you are literally reproducing single sine tones, as some of our customers are, double AES power is a good amplifier selection criteria.
 

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Re: matching amp with speakers

Ivan Beaver said:
Me to. Back then the way to test the power of an amp was to drive it into a dummy load and measure the voltage at clipping.

That took several seconds-WAAAAYYYYY longer than most modern amps can deliver their "rated" power.

But you also knew what you were getting. Today the big "unmentionable" in how long they can deliver rated power. and then what the power drops down to.

For many amps it is simply embarrassing. So they hope their customers don't understand the basics and "simply believe" the specs. Without ever testing.

I wonder how amps "back in the day' would have been built/designed if going by current "standards"-which arguably is closer to what is actually required.

So much has changed in the way of amp design over the last 30yrs or so. What we currently have was completely unthinkable back then.
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I am surely repeating myself, and I have wasted too many bits trying to describe a meaningful test for amp duty cycle, ever since Bink's great amp shoot out (remember that?).

I was in the trenches watching as amplifier evolved from 24x7, to "how long can you hold your breath", or even shorter full output duty cycles.

Squishy performance parameters like this evolve over time in a give and take with consumers and markets. While we all preferred the robust good old "all day every day" CS800, that robust performance cost money for more aluminum heat sinks and more copper/iron in the transformer than absolutely necessary (for music). When customers were offered the option of a lower duty cycle amplifier for less money, they jumped on that with both feet. So the race to the bottom was on, and Peavey had to capitulate to the new paradigm or give up market share to competitors who were already leaning out the window.

Some may recall the CS800"x" that over-night changed from 800W to 1200W output power simply by swapping out the fuse for a resettable breaker, and opening up the current limits in the output devices. This clearly gave it more short term power, but not one iota more long term power. The rest is history, and the markets hav embraced these lower duty cycle amps because they mostly work for typical applications, so why pay for more amp than you need?

While I can point to which manufacturer did it first, I can not blame them for giving the customer what they wanted , even if the customer didn't know that they wanted it yet. :-)

This will remain squishy, and every new value amp probably needs to be vetted in the real world to see how well it works for typical applications. I am optimistic that modern technology has dramatically scrubbed off a lot of aluminum and iron, without compromising amp power, somebody will always be testing the margins of how much can they cut and still be acceptable for mainstream use.

Professional users will always gravitate to more professional amps that do not test these performance limits so aggressively. This higher duty cycle is a feature that professionals willingly pay up for.


JR
 
Re: matching amp with speakers

Art & Ivan

My statement about speaker excursion vs thermal damage is based on years of following speaker repairs while I was at Peavey. I'm not just talking about tearing cones. You will still very likely end up with a burnt VC from an excursion related issue if you drive the VC out of the gap.

I don't know how far back the old days are for you guys but I remember rolling off the lows at about 80 Hz on my UREI 527's. Back then we didn't have "subs" ... we had A7's and A2's :)
 
Re: matching amp with speakers

Bennett Prescott said:
P.S. Technically pink noise has an infinite peak to average ratio. Like most signal seen by loudspeakers, you can pretty much bet on 12dB crest factor by the time it's gone through some phase shift either due to that inherent in the speaker / enclosure combo or the LPF / HPF in the processing. Unless you are literally reproducing single sine tones, as some of our customers are, double AES power is a good amplifier selection criteria.
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AFAIK both the EIA and AES speaker tests use shaped pink noise that is limited to 6 dB peaks. But I suppose that in the real world you could have peaks that equal whatever your headroom is at that moment in time.
 
Re: matching amp with speakers

Don Boomer said:
AFAIK both the EIA and AES speaker tests use shaped pink noise that is limited to 6 dB peaks. But I suppose that in the real world you could have peaks that equal whatever your headroom is at that moment in time.
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This is correct, but pink noise in general will not have 6dB crest factor. Truly random pink noise has no defined peak to average, but long term you can count on 12dB.
 
Re: matching amp with speakers

Ivan Beaver said:
What brand of speakers? Many of the cheap speakers tend to "overrate" the drivers and not use standard methods.

It is also HIGHLY dependent on the crest factor of the program material. Material with a low crest factor puts a lot more heating on the voice coil.

There is no simple answer for amp rating and speaker power ratings. There are A LOT of "it depends".
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i have a set of old CGM 15's , that have done extremely well for my setup. the cabs are rated at 400 rms to 800 watt peak. I have a set that someone made and i gutted them and put all new parts in them. a 3 way crossover and it is fully eminence loaded with the woofer rated at around 400 rms to 800 watts also. they are cheap ones i will admit but they have really surprised me in the sound and clearness. not to toot my own horn , but i have a lot of people say that my setup is a good one and i am like you really think so or are you just saying that just to be nice? my only concern is blowing something. I dont want to get my amp too hot and blow them or the speakers, as others have told me on here , I am pretty sure that isnt going to happen as long as i keep a close eye on things. my material that i have ran through it so far is stuff like speaking events , bluegrass, country, rock and praise and worship and rap from time to time.
 
Re: matching amp with speakers

Jimmy Hardin said:
i have a set of old CGM 15's , that have done extremely well for my setup. the cabs are rated at 400 rms to 800 watt peak. I have a set that someone made and i gutted them and put all new parts in them. a 3 way crossover and it is fully eminence loaded with the woofer rated at around 400 rms to 800 watts also. they are cheap ones i will admit but they have really surprised me in the sound and clearness. not to toot my own horn , but i have a lot of people say that my setup is a good one and i am like you really think so or are you just saying that just to be nice? my only concern is blowing something. I dont want to get my amp too hot and blow them or the speakers, as others have told me on here , I am pretty sure that isnt going to happen as long as i keep a close eye on things. my material that i have ran through it so far is stuff like speaking events , bluegrass, country, rock and praise and worship and rap from time to time.
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You were fine until you got to the rap part-------------------

You have not provided enough information for anybody to start to guess at. We don't know what drivers-just a rating that does not make any sense (typically the peak is 4 times the RMS-although there is no such thing as "RMS' watts.) We don't know what the other components are-what the crossover is-what actual limiting capability you have-or what capability you have to measure things and so forth.

If you are not having any issues-then I would not change anything-since it seems to be working for you.
 
Re: matching amp with speakers

Ivan Beaver said:
You were fine until you got to the rap part-------------------

You have not provided enough information for anybody to start to guess at. We don't know what drivers-just a rating that does not make any sense (typically the peak is 4 times the RMS-although there is no such thing as "RMS' watts.) We don't know what the other components are-what the crossover is-what actual limiting capability you have-or what capability you have to measure things and so forth.

If you are not having any issues-then I would not change anything-since it seems to be working for you.
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ok, sorry about that . here is a link to the crossovers and the woofer that i have in the cabnets.

http://www.usspeaker.com/homepage.html

Official Speaker Repair Site - Orange County Speaker - Home of GLS Audio Eminence Delta-Pro-12A - 400W RMS / 800W Peak 50Hz-5kHz


The only limiters that i am using is just whats on the amp.

I dont have a actual DB meter , all that i am using is a iphone db meter app.
 
Re: matching amp with speakers

Jimmy Hardin said:
ok, sorry about that . here is a link to the crossovers and the woofer that i have in the cabnets.

http://www.usspeaker.com/homepage.html

Official Speaker Repair Site - Orange County Speaker - Home of GLS Audio Eminence Delta-Pro-12A - 400W RMS / 800W Peak 50Hz-5kHz


The only limiters that i am using is just whats on the amp.

I dont have a actual DB meter , all that i am using is a iphone db meter app.
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The link to the crossover does not work. But I will assume it is a generiac crossovers-which means the final result you are getting is most likely not very good.

Yes it will "divide" the freq-but it does not account for the different impedances of the actual speakers being used-the sensitivity differences and so forth.

I am sure your speakers are far from ideal-meaning flat/constant impedance-flat amplitude past crossover freq-and the same sensitivity.

So without more measurements-it is hard to tell what is actually happening.

What amps are you using? Maybe you said-but I don't feel like looking back through all the posts to figure out what you have-and then have to go look up what the limiters are capable of.

So what are the limiter options? Do you have a voltmeter? Do you have a sine wave generator?
 
Re: matching amp with speakers

Ivan Beaver said:
The link to the crossover does not work. But I will assume it is a generiac crossovers-which means the final result you are getting is most likely not very good.

Yes it will "divide" the freq-but it does not account for the different impedances of the actual speakers being used-the sensitivity differences and so forth.

I am sure your speakers are far from ideal-meaning flat/constant impedance-flat amplitude past crossover freq-and the same sensitivity.

So without more measurements-it is hard to tell what is actually happening.

What amps are you using? Maybe you said-but I don't feel like looking back through all the posts to figure out what you have-and then have to go look up what the limiters are capable of.

So what are the limiter options? Do you have a voltmeter? Do you have a sine wave generator?
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I am running the Behringer ep4000 in stereo mode @4 ohms. the only limiter options is the ones that came in the amp.
 
Re: matching amp with speakers

Jimmy Hardin said:
I am running the Behringer ep4000 in stereo mode @4 ohms. the only limiter options is the ones that came in the amp.
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So exactly what would be those options?

It never hurts to actually provide that information-or a link to the unit/settings so people do no have to look it up for themselves.

After all-YOU are the one asking the questions-make it easy for people to give you answers.
 
Re: matching amp with speakers

Ivan Beaver said:
So exactly what would be those options?

It never hurts to actually provide that information-or a link to the unit/settings so people do no have to look it up for themselves.

After all-YOU are the one asking the questions-make it easy for people to give you answers.
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Ivan , I am so sorry if i have left any info out , please forgive me. what is it that you are looking for in info wise?
 
Re: matching amp with speakers

Jimmy Hardin said:
Sorry, art I put the wrong link up. its the 15" that i have in that speaker. sorry.
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The Delta Pro 15" has the same 400 watt EIA 426 power rating as the 12", and the voice coil will burn up if given 400 "watts rms" as in a sine wave.
Set your high pass filter a few Hz below box tuning, and long term limiting to around 200 watts (40 volts) and peak limiting to around 800 watts (80 volts) and your 15" will be protected. Your HF drivers are another matter, those limiter settings won't do anything for them.

Ivan asked you to provide the limiter options available "that came in the amp".

Art
 

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Re: matching amp with speakers

Art Welter said:
The Delta Pro 15" has the same 400 watt EIA 426 power rating as the 12", and the voice coil will burn up if given 400 "watts rms" as in a sine wave.
Set your high pass filter a few Hz below box tuning, and long term limiting to around 200 watts (40 volts) and peak limiting to around 800 watts (80 volts) and your 15" will be protected. Your HF drivers are another matter, those limiter settings won't do anything for them.

Ivan asked you to provide the limiter options available "that came in the amp".

Art
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That amp (That i know of) just has a switch to cut the limiter on or off, it doesnt have any other things that deals with the limiter on it. my cabs arent bi amped they are full range.
 
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