Let's Talk About Amplifier Clipping.

[Pandovski]

I'm curious now. Why do we have speakers that have power ratings of (example) 200W RMS max, yet they keep benefiting from amps 3-4-5 times the power rating and don't burn their tweeters even in large transients. Especially this is the case with inefficient speakers.

Can we bust this myth, if it is a myth.

 

[frankxbe]

I'm curious now. Why do we have speakers that have power ratings of (example) 200W RMS max, yet they keep benefiting from amps 3-4-5 times the power rating and don't burn their tweeters even in large transients. Especially this is the case with inefficient speakers.

Can we bust this myth, if it is a myth.

That seems to be the age old question for which I can not provide a definitive technical answer.
I would defer to those more qualified .

I read somewhere maybe AVS that a 20 db peak above average may require in some cases as much as 100 times more amplifier power momentarily.

As I understand it, it could be possible that for example a 200 watt
amp playing at lets say 2 watts average into a given speaker load (not unreasonable) may indeed in such an instance
(20dB peak) can momentarily peak at 200 watts if it is capable.

ofc using that specification a six watt average in turn may generate a 600 watt peak if the amplifier has sufficient peak power reserves and the speakers can handle it .


Klipsch has some home speakers rated at 250 WPC RMS and 1000 WPC peaks with surprisingly a 101dB 1w 1m efficiency

POWER HANDLING: 250W RMS / 1000W Peak
NOMINAL IMPEDANCE: 8 ohms compatible
SENSITIVITY: 101dB @ 2.83V / 1m
http://www.klipsch.com/rf-7-ii-floorstanding-speaker/details#specs

otoh I would caution anyone in the above predicament (amps with much higher power than the speaker is rated for ) not to get to carried away with the loudness control as the potential for frying speakers certainly is a possibility having done that myself
the past with both woofers and tweeters and yes mids too! :yes:

 

[89grand]

I'm curious now. Why do we have speakers that have power ratings of (example) 200W RMS max, yet they keep benefiting from amps 3-4-5 times the power rating and don't burn their tweeters even in large transients. Especially this is the case with inefficient speakers.

Can we bust this myth, if it is a myth.

Well, because we listen to music. Even if it's "loud" you're probably only using a few watts on average, since music typically has loud and soft passages. On the loud peaks maybe the amp puts out power above the speakers rating, but it's usually very brief. If you played pink noise at maximum volume with an amp rated at 3-5 times the speakers rating, you'd kill that speaker in no time.:yes:

 

[Pandovski]

Pink noise?

 

[ofajen]

I'm sorry, I keep logging on to answer your question, only to be distracted playing Internet Whack-A-Mole with the clipping enthusiasts.

Setting power ratings for a speaker is never a science and is based largely on the experience of the designers, along with commercial pressures. If one tries to establish an absolutely safe rating, where the speaker would survive any frequency for any amount of time, at any plausible ambient temperature, few speakers, even large ones, would reach 10 Watts. Rating a speaker that way would be commercial suicide, and would keep people from using their speakers anywhere near their actual potential.

At NHT, we rated speakers over a range of amp power. At the low end of the scale, we considered the sensitivity of the speaker and its likely application, and picked a Wattage that we felt would give people at least a decent and expected sound level. At the high end of the scale, we picked an amp the would push a speaker to its limits in normal use. One that, if it was exceeded, would probably not wring more performance from the speaker, and would only increase the risk of damage.

Of course, there are plenty of situations where folks were very happy running speakers with smaller amps in, say, desktop applications. And, plenty of reports of SuperZeros, etc, being successfully run off of 200W/ch.

-k

Thanks for that. After reading through that article and considering the likely variation in use patterns, I'd pretty much guessed what you were going for on the end points: from "barely enough" up to "don't bother with more". That makes a lot of sense to me.

Otto

 

[ofajen]

Pink noise?

That's the generic form of 1/f noise. The "Hello Kitty" version costs a lot more.

Otto

 

[89grand]

Pink noise?

Yes. Although playing Pink real loud might do it too.

 

[Pandovski]

So as long as I'm listening to Pantera and not pink noise, I can have a 1000WPC RMS amp pushing 200W RMS peak speakers to extremely loud levels?

 

[fhawk618]

I'm in the camp that believes that there is no such thing as too much power... with the caviat that power is not just watts @ 8 ohms... it has to do with current as well... I collect (hoard) speakers that drop below 1 ohm impedence and tend to crush amps. Therefore, a power rating at 8 ohms on an amp or power rating on a speaker are pretty much irrelevant to me...

 

[winters860]

I've always thought that a good rule of thumb for the rubes is to learn to recognize distortion. Audible distortion is a sign that either the amp or speakers are being pushed too hard and that speaker failure is likely imminent. Keeping that in mind, it doesn't matter, really, how much or how little output the amplifier is capable of.

Nonetheless, I appreciate Ken's debunking. I've told a lot of people wrong over the years.

 

[nailer]

Ken, I remember a while back I said I quit and it was pointless. Nice to see you are more dedicated than myself. It's hard to keep repeating yourself over and over and over again, but you deserve credit for continuing the fight against incorrect information, and you are certainly more knowledgeable than me, so hopefully coming from you it sinks in.

The sad part is, half the forum tomorrow will again say clipping ruins tweeters. I hope I'm wrong.

Lost causes are the only ones worth fighting for. Doctor Johnny Fever

 

[ofajen]

Ken, I remember a while back I said I quit and it was pointless. Nice to see you are more dedicated than myself. It's hard to keep repeating yourself over and over and over again, but you deserve credit for continuing the fight against incorrect information, and you are certainly more knowledgeable than me, so hopefully coming from you it sinks in.

The sad part is, half the forum tomorrow will again say clipping ruins tweeters. I hope I'm wrong.

A sticky thread on this... short and to the point, would be a handy way to bring people up to speed if they are unfamiliar with this, without having to get into a lot of back and forth.

Otto

 

[ken kantor]

Ken, I remember a while back I said I quit and it was pointless. Nice to see you are more dedicated than myself. It's hard to keep repeating yourself over and over and over again, but you deserve credit for continuing the fight against incorrect information, and you are certainly more knowledgeable than me, so hopefully coming from you it sinks in.

The sad part is, half the forum tomorrow will again say clipping ruins tweeters. I hope I'm wrong.

First of all, I hope you know that your posts in this thread and in the past were very helpful in spreading the word. In addition, they often clarified confusing points, encouraged me to stick with it, and added a credible second opinion to the fray. So, really, we couldn't have done it without you!

As far as the general opinion lapsing back, or perhaps not having been reached at all.... well, the important thing is that a few more people now know the correct information, and can spread and defend it to yet more still. And searching the term "tweeters and amp clipping" is that much more likely to provide correct results now.

-k

(As a side note: I suspect that an additional unconscious motivation for my tenacity was guilt about having been some small part of spreading the wrong info in the first place. No reason for you to have that particular motivation.)

 

[frankxbe]

Sound loudness - Sound pressure - Sound intensity The factors and their levels in dec

removed double post ( I hate it when it does that)

 

[frankxbe]

Found this chart (actually Google found it )
http://www.sengpielaudio.com/calculator-levelchange.htm

As I presently understand it a doubling of loudness +10dB SPL requires in the order of 10X multiplication of amplifier power to a given speaker ...

Ofc I understand there are many other amplifier -speaker specifications to consider such as dampening factor slew rate impedance curve performance and a whole list of some other specifications I do not necessarily understand at a technical level but this looks like a good direction from where to start anyway.

If for example you had a speaker rated at a 101dB 1W 1M@ 8 ohm efficiency and you wanted to allow for 20dB peaks it would perhaps not be unreasonable to design the speaker around a 250w rms@ 8 ohm maximum specification and 1,000 watt peak power specification
so if one were to use a 200watt @8 ohm specification amplifier and was using 2 watts average music level a 20dB peak would require 200 (x100) watts (ofc usually per channel in a 2 channel system )
momentarily from the amplifier to address that peak without distress to either the amplifier or speaker .
that is exactly how Klipsch specified the RF7 II speaker for instance. http://www.klipsch.com/rf-7-ii-floorstanding-speaker/details#specs this is assuming ofc the manufactures specifications are genuine and accurate.

OTOH given these speakers efficiency maybe be a much smaller amp would be fine but how much smaller and what dB peak increase could it address ?
with a 2 watt average level. and how would we arrive at such a solution?

if a +20db gain (4x) loudness requires 100x power from 2 watts or 200 watts therein lies the dilemma.
how would a 100 watt amp with good headroom work or 50watt amp?

ofc a 20dB is a (4x ) increase in loudness and(100X) power given the
efficiency of these speakers @ 2watts and accounting for some room gain in an average size maybe 25'x15' room is a +20dB specification requirement realistic?
or given the speakers efficiancy would less than 2 watts be ideal for a reasonable level at lets say 4 m to the listening position .
and also staying within a THX reference level and peak specification capability

I'm a little confused on the math (the logarithmic thing) as applied to dB but gaining respect for the engineer types that have to figure this stuff out.

 

[fhawk618]

I'm curious now. Why do we have speakers that have power ratings of (example) 200W RMS max, yet they keep benefiting from amps 3-4-5 times the power rating and don't burn their tweeters even in large transients. Especially this is the case with inefficient speakers.

Can we bust this myth, if it is a myth.

Using larger than probably necessary amps prevents the potential for clipping a signal... how speaker builders' establish a power rating has always been a mystery to me...

What I do know... and I do pro-audio/live sound reinforcement... is that heat build-up or effective (or lack thereof) dissipation is a speaker's worst enemy when driven under large amounts of power. I have pro sub cabs that have external heat sinks that are bolted to the motor structure of the drivers, and by the end of the night, you can burn yourself on them. A quick little transient spike to a driver is not likely to "smoke" it, but continuous power generates a lot of heat due to the inefficiency of the motor structure and impedence of the voice coil.

 

[bowtie427ss]

As I presently understand it a doubling of loudness +10dB SPL requires in the order of 10X multiplication of amplifier power to a given speaker ...

Yes. :yes:

+3db = double power
+6db = double amplitude, quadruple power
+10db = 10x power
+20db = 10x amplitude, 100x power

What I do know... and I do pro-audio/live sound reinforcement... is that heat build-up or effective (or lack thereof) dissipation is a speaker's worst enemy when driven under large amounts of power. I have pro sub cabs that have external heat sinks that are bolted to the motor structure of the drivers, and by the end of the night, you can burn yourself on them. A quick little transient spike to a driver is not likely to "smoke" it, but continuous power generates a lot of heat due to the inefficiency of the motor structure and impedence of the voice coil.

............... and that is a viscous cycle. Heat increases resistance in a conductor, and it reduces magnet strength causing increased power compression, all this causing the soundman to push the system gain higher in order to maintain the same acoustic output.

 

[fpitas]

I read somewhere maybe AVS that a 20 db peak above average may require in some cases as much as 100 times more amplifier power momentarily.

Yes, some recordings (mostly classical) have 20dB peaks, or slightly more. 20dB is 100 x the power, by definition. Now, good recordings of popular music will have more like 15dB peaks at most, but if you look at a highly compressed recording it may have as little as 4dB (!). This is what the whole "loudness war" discussion is about, the loss of dynamic range.

 

[audiozaz]

Yes. :yes:

+3db = double power
+6db = double amplitude, quadruple power
+10db = 10x power
+20db = 10x amplitude, 100x power

............... and that is a viscous cycle. Heat increases resistance in a conductor, and it reduces magnet strength causing increased power compression, all this causing the soundman to push the system gain higher in order to maintain the same acoustic output.

DJ-induced thermal runaway. Alternatively, use current-drive amps for the automated version.

I always believed harmonics blew tweeters and am glad I now know better. Seeing the spectral power distribution of a square wave makes the point IMO.

az

 

[RayW]

What I do know... and I do pro-audio/live sound reinforcement... is that heat build-up or effective (or lack thereof) dissipation is a speaker's worst enemy when driven under large amounts of power. I have pro sub cabs that have external heat sinks that are bolted to the motor structure of the drivers, and by the end of the night, you can burn yourself on them.

I was the guy power testing the Eminence Kilomaxx speakers while they were being developed. The thought of using them as a grill for burgers at lunch was always in the back of my mind.