Sign in with
Sign up | Sign in
Your question

I did not kill my power amp

Last response: in Home Audio
Share
Anonymous
May 7, 2005 7:08:49 PM

Archived from groups: rec.audio.pro (More info?)

Just an update for the archives, the Adcom 535 II that I posted about is
now performing beautifully. All four of the 4 amp 250V fuses on the main
circuit board were blown, while the 5 amp 250V main fuse was not blown.
I replaced them with 4A 250V fast-acting fuses and both channels now
sound great *whew*. Thanks to all who responded and berated me for
buying on eBay and using gain as a testing tool. After the fuses were
replaced I also made sure to try out both channels on an old panasonic
junker.

Jonny Durango

The subway doors open. A hobo enters, holding a bottle of windex in one
hand and a tube of toothpaste in the other. He says: Which is the better
time to read Dostyevsky? Winter?

He sprays the windex.

Hobo: Or Spring?

He squeezes toothpaste out of the tube.

Japanese girl: Spring!

Hobo: You are correct.

Source: http://www.overheardinnewyork.com/

More about : kill power amp

Anonymous
May 7, 2005 7:22:59 PM

Archived from groups: rec.audio.pro (More info?)

and still I want to inquire

did you fuse the speakers you built? and if you did, how?

It was much discussed and the pro's and con's debated here.

dale
Anonymous
May 7, 2005 8:06:01 PM

Archived from groups: rec.audio.pro (More info?)

> did you fuse the speakers you built? and if you did, how?

There are two ways to "fuse" a speaker. One way is to pump too much current
through them.

By the way, I'm glad the problem turned out to be blown fuses. It's nice when
you can fix stuff yourself for a few bucks.
Related resources
Anonymous
May 8, 2005 9:40:13 PM

Archived from groups: rec.audio.pro (More info?)

dale wrote:
> and still I want to inquire
>
> did you fuse the speakers you built? and if you did, how?
>
> It was much discussed and the pro's and con's debated here.
>
> dale
>

No I never ended up doing that. I probably will later down the
road....in the mean time I'll simply have to be very careful and keep
friends away from the volume knob.
Anonymous
May 8, 2005 9:59:43 PM

Archived from groups: rec.audio.pro (More info?)

> No, I never ended up doing that. I probably will later down the
> road... In the meantime I'll simply have to be very careful and
> keep friends away from the volume knob.

This is The Great Speaker Killer. Listeners who don't recognize distortion (ie,
most listeners) keep cranking up the volume until the speaker is destroyed.
Anonymous
May 9, 2005 12:50:53 AM

Archived from groups: rec.audio.pro (More info?)

George Gleason wrote:

> Distortion does not kill(as in burn out) speakers any quicker than clean
> sound
> what kills speakers is exceeding the heat shedding(wattage rateing) of
> the voice coil
> 235 watt of pure distortion will NEVER burn out a properly rated 300
> watt speaker

Are you sure about this? I always heard that using an under powered amp
and driving it to distortion can kill speakers. Even a low powered amp.
So this is not the case?
Anonymous
May 9, 2005 7:18:07 AM

Archived from groups: rec.audio.pro (More info?)

On Mon, 09 May 2005 02:05:48 GMT, George Gleason
<g.p.gleason@worldnet.att.net> wrote:

>which is why I said "properly rated" in regards to the speaker

Sure 'nuf. That should really mean that the amplifier never
clips; not impossible with modern amplifiers and sensible
operaters.

The "sensible" part might get difficult in some circumstances,
so another issue can crop up: clipping causes distortion
products that *all* are higher in pitch that the note that
cause them. To the extent that they fall into the range of
the inherently more fragile tweeter-ish drivers, damage can
occur from "too small" amplifiers.

All stuff you know all too well; only mentioned for completeness.

Chris Hornbeck
"Clean, edgy, gutless, and lifeless." -Dan Kennedy
Anonymous
May 9, 2005 8:56:14 AM

Archived from groups: rec.audio.pro (More info?)

>>> No, I never ended up doing that. I probably will later down the
>>> road... In the meantime I'll simply have to be very careful and
>>> keep friends away from the volume knob.

>> This is The Great Speaker Killer. Listeners who don't recognize distortion
(ie,
>> most listeners) keep cranking up the volume until the speaker is destroyed.

> Distortion does not kill (as in burn out) speakers any quicker than clean
> sound what kills speakers is exceeding the heat shedding(wattage rating)
> of the voice coil 235 watt of pure distortion will NEVER burn out a properly
> rated 300 watt speaker

That isn't what I said. At all. Please re-read it.
Anonymous
May 9, 2005 9:00:51 AM

Archived from groups: rec.audio.pro (More info?)

> > Distortion does not kill(as in burn out) speakers any quicker than clean
> > sound
> > what kills speakers is exceeding the heat shedding(wattage rateing) of
> > the voice coil
> > 235 watt of pure distortion will NEVER burn out a properly rated 300
> > watt speaker
>
> Are you sure about this? I always heard that using an under powered amp
> and driving it to distortion can kill speakers. Even a low powered amp.
> So this is not the case?

The "urban legend" has always been that driving a low-powered amp into clipping
is more likely to burn out a speaker (the tweeter, at least) than playing a
higher-powered amp at without clipping.

The reasoning is that a clipped waveform has considerably more HF energy than a
higher-voltage waveform that isn't clipped. This makes sense, but no one (AFAIK)
has ever actually performed the experiment.

Regardless of whether the waveform is clipped or not, a speaker is damaged when
the average power (not RMS power -- there is no such thing) delivered to its
voice coil heats it to the point where the adhesive comes loose, the former is
deformed, etc.
Anonymous
May 9, 2005 9:53:00 AM

Archived from groups: rec.audio.pro (More info?)

Joe Sensor wrote:

> George Gleason wrote:

>> Distortion does not kill(as in burn out) speakers any
quicker than clean sound
>> what kills speakers is exceeding the heat
shedding(wattage rating) of the voice coil
>> 235 watt of pure distortion will NEVER burn out a
properly rated 300
>> watt speaker

> Are you sure about this?

If he isn't, I am. ;-)

George posts frequently and expertly to
alt.audio.pro.live-sound. People who do live sound as a
group probably have more experience with damaging and
damaged speakers than just about any other group of audio
folks, because of the nature of their work.

>I always heard that using an under powered
> amp and driving it to distortion can kill speakers.

An old wife's tale - one that has been deconstructed by
technical experts and expert hands-on workers many times.

> Even a low powered amp. So this is not the case?

Nope.

Here's a technical paper from a reliable source that
debunks that idea:

http://www.rane.com/note128.html
Anonymous
May 9, 2005 10:05:03 AM

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck wrote:
> On Mon, 09 May 2005 02:05:48 GMT, George Gleason
> <g.p.gleason@worldnet.att.net> wrote:
>
>> which is why I said "properly rated" in regards to the
speaker
>
> Sure 'nuf. That should really mean that the amplifier
never
> clips; not impossible with modern amplifiers and sensible
> operaters.
>
> The "sensible" part might get difficult in some
circumstances,
> so another issue can crop up: clipping causes distortion
> products that *all* are higher in pitch that the note that
> cause them.

However, this does not mean that clipping always produces a
signal with more energy at high frequencies than the
origional unclipped signal. Distorting a signal produces
spurious responses at both harmonics and also difference
frequencies. As a rule, the difference frequencies vastly
outnumber the harmonics. Their basic nature is that they are
lower than the frequencies that are present in the original
signal.
Anonymous
May 9, 2005 11:50:31 AM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger wrote:

> If he isn't, I am. ;-)
>
> George posts frequently and expertly to
> alt.audio.pro.live-sound. People who do live sound as a
> group probably have more experience with damaging and
> damaged speakers than just about any other group of audio
> folks, because of the nature of their work.

Agreed. That's why I was very interested in George's reply.
Anonymous
May 9, 2005 1:53:27 PM

Archived from groups: rec.audio.pro (More info?)

In article <3e7tvsF1lq1kU1@individual.net>,
Joe Sensor <crabcakes@emagic.net> wrote:
>George Gleason wrote:
>
>> Distortion does not kill(as in burn out) speakers any quicker than clean
>> sound
>> what kills speakers is exceeding the heat shedding(wattage rateing) of
>> the voice coil
>> 235 watt of pure distortion will NEVER burn out a properly rated 300
>> watt speaker
>
>Are you sure about this? I always heard that using an under powered amp
>and driving it to distortion can kill speakers. Even a low powered amp.
>So this is not the case?

It _is_ the case, because very few speakers out there meet George's
definition of "properly rated."

In fact, speaker power ratings are mostly made-up numbers that someone
in the marketing department pulled out of their okole.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
May 9, 2005 2:19:23 PM

Archived from groups: rec.audio.pro (More info?)

William Sommerwerck <williams@nwlink.com> wrote:
>
>The "urban legend" has always been that driving a low-powered amp into clipping
>is more likely to burn out a speaker (the tweeter, at least) than playing a
>higher-powered amp at without clipping.
>
>The reasoning is that a clipped waveform has considerably more HF energy than a
>higher-voltage waveform that isn't clipped. This makes sense, but no one (AFAIK)
>has ever actually performed the experiment.

I believe Dick Pierce has.

>Regardless of whether the waveform is clipped or not, a speaker is damaged when
>the average power (not RMS power -- there is no such thing) delivered to its
>voice coil heats it to the point where the adhesive comes loose, the former is
>deformed, etc.

This is the usual failure mode for woofers, but not always the usual one for
compression drivers.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
May 9, 2005 3:50:26 PM

Archived from groups: rec.audio.pro (More info?)

In article <117uk6icpk6j9b7@corp.supernews.com> williams@nwlink.com writes:

> The "urban legend" has always been that driving a low-powered amp into clipping
> is more likely to burn out a speaker (the tweeter, at least) than playing a
> higher-powered amp at without clipping.
>
> The reasoning is that a clipped waveform has considerably more HF energy than a
> higher-voltage waveform that isn't clipped. This makes sense, but no one
> (AFAIK)
> has ever actually performed the experiment.

Well, we don't like to destructively test our speakers. Also, the
"threshold of destruction" for a speaker isn't particularly well
defined. There really isn't a good experiment to perform.

> Regardless of whether the waveform is clipped or not, a speaker is damaged when
> the average power (not RMS power -- there is no such thing) delivered to its
> voice coil heats it to the point where the adhesive comes loose, the former is
> deformed, etc.

The average energy in a square wave is greater than that in a sine
wave of the same fundamental frequency and peak amplitude. Since the
peak output level of an amplifier is usually equal to or very close to
the power supply voltage, when you let it clip, you put more energy
into the load than if you don't. More energy blows more speakers
sooner.




--
I'm really Mike Rivers - (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
May 9, 2005 5:28:33 PM

Archived from groups: rec.audio.pro (More info?)

William Sommerwerck wrote:
>>> Distortion does not kill(as in burn out) speakers any quicker than
>>> clean sound
>>> what kills speakers is exceeding the heat shedding(wattage rateing)
>>> of the voice coil
>>> 235 watt of pure distortion will NEVER burn out a properly rated 300
>>> watt speaker
>>
>> Are you sure about this? I always heard that using an under powered
>> amp and driving it to distortion can kill speakers. Even a low
>> powered amp. So this is not the case?
>
> The "urban legend" has always been that driving a low-powered amp
> into clipping is more likely to burn out a speaker (the tweeter, at
> least) than playing a higher-powered amp at without clipping.
>
> The reasoning is that a clipped waveform has considerably more HF
> energy than a higher-voltage waveform that isn't clipped. This makes
> sense, but no one (AFAIK) has ever actually performed the experiment.
>

An amplifier is rated and measured by its *sine* wave average power
(Irms.Vrms). The peak supply voltage to achieve this rms voltage is
sqrt(2) times larger. The peak current from this voltage is also sqrt(2)
times larger for the same load. So, a square wave at these peak rail
voltages will generate 2 times the average rated power into the load,
continuously. We therefore don't have to introduce any hi tooting
concepts of "hf energy spectrum" to account for why such a signal can
thermally destroy a resistive voice coil. Its *twice* the rated power of
the amplifier, at any frequency. Dah...

What contributes even more so, is that heavily clipped waveforms look
like a square wave for much longer, and so spend more time at that
maximum output power. Non clipped waveforms, only have peak average
powers for a fraction of the time, such that the average average power
is less. Yes, and I mean the average average power!

Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
Anonymous
May 9, 2005 6:21:38 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> In article <3e7tvsF1lq1kU1@individual.net>,
> Joe Sensor <crabcakes@emagic.net> wrote:
>> George Gleason wrote:
>>
>>> Distortion does not kill(as in burn out) speakers any quicker than
>>> clean sound
>>> what kills speakers is exceeding the heat shedding(wattage rateing)
>>> of the voice coil
>>> 235 watt of pure distortion will NEVER burn out a properly rated 300
>>> watt speaker
>>
>> Are you sure about this? I always heard that using an under powered
>> amp and driving it to distortion can kill speakers. Even a low
>> powered amp. So this is not the case?
>
> It _is_ the case, because very few speakers out there meet George's
> definition of "properly rated."
>
> In fact, speaker power ratings are mostly made-up numbers that someone
> in the marketing department pulled out of their okole.
> --scott

Well, according to JBL, they do power noise testing. As far as thermal
goes, all you should have to do is measure the steady state temperature
of the coil. The aging/fusing characteristics of wire over temperature
is very well known.

Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
Anonymous
May 9, 2005 6:21:39 PM

Archived from groups: rec.audio.pro (More info?)

Kevin Aylward <see_website@anasoft.co.uk> wrote:
>Scott Dorsey wrote:
>> Joe Sensor <crabcakes@emagic.net> wrote:
>>> George Gleason wrote:
>>>
>>>> Distortion does not kill(as in burn out) speakers any quicker than
>>>> clean sound
>>>> what kills speakers is exceeding the heat shedding(wattage rateing)
>>>> of the voice coil
>>>> 235 watt of pure distortion will NEVER burn out a properly rated 300
>>>> watt speaker
>>>
>>> Are you sure about this? I always heard that using an under powered
>>> amp and driving it to distortion can kill speakers. Even a low
>>> powered amp. So this is not the case?
>>
>> It _is_ the case, because very few speakers out there meet George's
>> definition of "properly rated."
>>
>> In fact, speaker power ratings are mostly made-up numbers that someone
>> in the marketing department pulled out of their okole.
>
>Well, according to JBL, they do power noise testing. As far as thermal
>goes, all you should have to do is measure the steady state temperature
>of the coil. The aging/fusing characteristics of wire over temperature
>is very well known.

JBL's numbers are really about the only ones out there that I would come
close to trusting. Most of the vendors out there don't even bother doing
that.

Part of the problem is that there are a bunch of different failure modes.
You can overheat a driver and burn the coil with high continuous levels,
but then again you can also drive the coil beyond maximum excursion and
rip the cone and spider with a short transient too. So one single scalar
power number may not tell the whole story anyway....

And it's made worse by the fake power ratings on amplifiers. Pro audio
manufacturers don't have to hold by the FTC guidelines for power ratings
and you do see some crazy numbers out there that don't reflect the real
amplifier power. It's not as bad as it is in the car audio world, mind
you, but it's bad.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
May 9, 2005 7:20:39 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> Kevin Aylward <see_website@anasoft.co.uk> wrote:
>> Scott Dorsey wrote:
>>> Joe Sensor <crabcakes@emagic.net> wrote:
>>>> George Gleason wrote:
>>>>
>>>>> Distortion does not kill(as in burn out) speakers any quicker than
>>>>> clean sound
>>>>> what kills speakers is exceeding the heat shedding(wattage
>>>>> rateing) of the voice coil
>>>>> 235 watt of pure distortion will NEVER burn out a properly rated
>>>>> 300 watt speaker
>>>>
>>>> Are you sure about this? I always heard that using an under powered
>>>> amp and driving it to distortion can kill speakers. Even a low
>>>> powered amp. So this is not the case?
>>>
>>> It _is_ the case, because very few speakers out there meet George's
>>> definition of "properly rated."
>>>
>>> In fact, speaker power ratings are mostly made-up numbers that
>>> someone in the marketing department pulled out of their okole.
>>
>> Well, according to JBL, they do power noise testing. As far as
>> thermal goes, all you should have to do is measure the steady state
>> temperature of the coil. The aging/fusing characteristics of wire
>> over temperature is very well known.
>
> JBL's numbers are really about the only ones out there that I would
> come close to trusting. Most of the vendors out there don't even
> bother doing that.
>
> Part of the problem is that there are a bunch of different failure
> modes. You can overheat a driver and burn the coil with high
> continuous levels, but then again you can also drive the coil beyond
> maximum excursion and rip the cone and spider with a short transient
> too.

Yes. Thats why I always go for the amp rating <= speaker ratings.

> So one single scalar power number may not tell the whole story
> anyway....
>
> And it's made worse by the fake power ratings on amplifiers. Pro
> audio manufacturers don't have to hold by the FTC guidelines for
> power ratings and you do see some crazy numbers out there that don't
> reflect the real amplifier power. It's not as bad as it is in the
> car audio world, mind you, but it's bad.

I would say most pro audio companies pretty much always give correct
average power ratings (rms) in my view.

Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
Anonymous
May 10, 2005 9:21:59 AM

Archived from groups: rec.audio.pro (More info?)

Kevin Aylward wrote:

> Scott Dorsey wrote:
> > In article <3e7tvsF1lq1kU1@individual.net>,
> > Joe Sensor <crabcakes@emagic.net> wrote:
> >> George Gleason wrote:
> >>
> >>> Distortion does not kill(as in burn out) speakers any quicker than
> >>> clean sound
> >>> what kills speakers is exceeding the heat shedding(wattage rateing)
> >>> of the voice coil
> >>> 235 watt of pure distortion will NEVER burn out a properly rated 300
> >>> watt speaker
> >>
> >> Are you sure about this? I always heard that using an under powered
> >> amp and driving it to distortion can kill speakers. Even a low
> >> powered amp. So this is not the case?
> >
> > It _is_ the case, because very few speakers out there meet George's
> > definition of "properly rated."
> >
> > In fact, speaker power ratings are mostly made-up numbers that someone
> > in the marketing department pulled out of their okole.
> > --scott
>
> Well, according to JBL, they do power noise testing. As far as thermal
> goes, all you should have to do is measure the steady state temperature
> of the coil. The aging/fusing characteristics of wire over temperature
> is very well known.

Actually, it's often the adhesive that gives up first.

Graham
Anonymous
May 10, 2005 9:24:05 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> And it's made worse by the fake power ratings on amplifiers. Pro audio
> manufacturers don't have to hold by the FTC guidelines for power ratings
> and you do see some crazy numbers out there that don't reflect the real
> amplifier power. It's not as bad as it is in the car audio world, mind
> you, but it's bad.

It is ? Please give an example.

I've rarely seen a pro amp that didn't deliver its rated rms power.

Graham
Anonymous
May 10, 2005 9:24:06 AM

Archived from groups: rec.audio.pro (More info?)

> I've rarely seen a pro amp that didn't deliver its rated rms power.

There is no such thing (other than a mathematical definition) as RMS power. The
correct term is average (or average continuous) power.
Anonymous
May 10, 2005 9:53:33 AM

Archived from groups: rec.audio.pro (More info?)

On Tue, 10 May 2005 05:21:59 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>Actually, it's often the adhesive that gives up first.

Or the VC former hitting the magnet enough to bend itself
fatally. But, yeah, most all abuse failures are thermal, and
clipping/overdriving the amplifier causes most tweeter
failures. My personal experience, with my first pair (always
mono before) of store-bought (always homemade before) of
Smaller Advent's on the very evening that I bought them, excepted,
playing the Yes _Close to the Edge_ album, was clearly Divine
intervention.

Chris Hornbeck
Anonymous
May 10, 2005 9:53:57 AM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:Qsmdna4oEJjXq-LfRVn-uw@comcast.com...

> However, this does not mean that clipping always produces a
> signal with more energy at high frequencies than the
> origional unclipped signal. Distorting a signal produces
> spurious responses at both harmonics and also difference
> frequencies. As a rule, the difference frequencies vastly
> outnumber the harmonics. Their basic nature is that they are
> lower than the frequencies that are present in the original
> signal.

Naw. Distorting a signal produces sum *and* difference frequencies. The sums
are higher. The differences are lower.

Peace,
Paul
Anonymous
May 10, 2005 10:55:59 AM

Archived from groups: rec.audio.pro (More info?)

Paul Stamler wrote:
> "Arny Krueger" <arnyk@hotpop.com> wrote in message
> news:Qsmdna4oEJjXq-LfRVn-uw@comcast.com...
>
>> However, this does not mean that clipping always produces
a
>> signal with more energy at high frequencies than the
>> origional unclipped signal. Distorting a signal produces
>> spurious responses at both harmonics and also difference
>> frequencies. As a rule, the difference frequencies vastly
>> outnumber the harmonics. Their basic nature is that they
are
>> lower than the frequencies that are present in the
original
>> signal.
>
> Naw. Distorting a signal produces sum *and* difference
frequencies.
> The sums are higher. The differences are lower.

The sums are very often out-of-the-audible range, and can be
therefore safely ignored.
Anonymous
May 10, 2005 2:05:54 PM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
>Paul Stamler wrote:
>> "Arny Krueger" <arnyk@hotpop.com> wrote in message
>> news:Qsmdna4oEJjXq-LfRVn-uw@comcast.com...
>>
>>> However, this does not mean that clipping always produces
>a
>>> signal with more energy at high frequencies than the
>>> origional unclipped signal. Distorting a signal produces
>>> spurious responses at both harmonics and also difference
>>> frequencies. As a rule, the difference frequencies vastly
>>> outnumber the harmonics. Their basic nature is that they
>are
>>> lower than the frequencies that are present in the
>original
>>> signal.
>>
>> Naw. Distorting a signal produces sum *and* difference
>frequencies.
>> The sums are higher. The differences are lower.
>
>The sums are very often out-of-the-audible range, and can be
>therefore safely ignored.

No, not at all! That ultrasonic stuff can't be heard, and it also cannot
be reproduced by the tweeter. Because the tweeter is unable to move quickly
enough, it gets dissipated as heat. Check the impedance curve of a typical
dome tweeter and see what happens above 20 KHz. Pumping ultrasonic stuff
into a tweeter is a very quick way to get smoke.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
May 10, 2005 5:12:15 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> No, not at all! That ultrasonic stuff can't be heard, and it also cannot
> be reproduced by the tweeter. Because the tweeter is unable to move quickly
> enough, it gets dissipated as heat.

I was wondering about that.

Thanks, Scott. It is great to have someone around that really knows his
stuff.
Anonymous
May 10, 2005 5:32:50 PM

Archived from groups: rec.audio.pro (More info?)

On 9 May 2005 09:53:27 -0400, Scott Dorsey <kludge@panix.com> wrote:

> In article <3e7tvsF1lq1kU1@individual.net>,
> Joe Sensor <crabcakes@emagic.net> wrote:
>>
>> Are you sure about this? I always heard that using an under powered amp
>> and driving it to distortion can kill speakers. Even a low powered amp.
>> So this is not the case?
>
> It _is_ the case, because very few speakers out there meet George's
> definition of "properly rated."
>
> In fact, speaker power ratings are mostly made-up numbers that someone
> in the marketing department pulled out of their okole.

And speaker ratings tend to assume a standard music/speech signal rather
than sine waves. High frequency drivers in a system are often rated at a
much lower power than low frequency drivers - something like 20W in a 100W
system. With normal music most of the power is used at the bass/mid
frequencies so highly rated tweeters aren't needed.

Cheers.

James.
Anonymous
May 10, 2005 8:56:44 PM

Archived from groups: rec.audio.pro (More info?)

"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:Ba6dnTWk7rhVDh3fRVn-1w@comcast.com...
> Paul Stamler wrote:
> > Naw. Distorting a signal produces sum *and* difference
> frequencies.
> > The sums are higher. The differences are lower.
>
> The sums are very often out-of-the-audible range, and can be
> therefore safely ignored.

Not if the issue is burning out tweeters.

Besides, it ain't so. If both signals are <10kHz then the first-order sum
will be audible, at least to children, and if they're below 7kHz the sum
will be audible even to old farts. And, of course, lower frequencies
intermodulate plenty too; the secret of the fuzzbox.

Peace,
Paul
Anonymous
May 10, 2005 8:56:45 PM

Archived from groups: rec.audio.pro (More info?)

Paul Stamler wrote:
> "Arny Krueger" <arnyk@hotpop.com> wrote in message
> news:Ba6dnTWk7rhVDh3fRVn-1w@comcast.com...
>> Paul Stamler wrote:
>>> Naw. Distorting a signal produces sum *and* difference
>> frequencies.
>>> The sums are higher. The differences are lower.
>>
>> The sums are very often out-of-the-audible range, and can
be
>> therefore safely ignored.
>
> Not if the issue is burning out tweeters.

Agreed.

> Besides, it ain't so. If both signals are <10kHz then the
first-order
> sum will be audible, at least to children, and if they're
below 7kHz
> the sum will be audible even to old farts. And, of course,
lower
> frequencies intermodulate plenty too; the secret of the
fuzzbox.

Right.

I've done the experiment, and take many kinds of music and
clipped the !!#@!! out of it. It ends up with about the same
overall spectral shaping of a square wave. We all know this
is like a -6 dB/oct roll-off which is the same as the
spectral shaping of red or brown noise. IME this happens
pretty consistently.

I may not have the reason right, but this is what I've
repeatedly observed happening.

Whether the clipped signal is tougher or easier on tweeters
or whatever than the origional music thus depends on the
spectral shaping of the origional music. The unclipped music
is going to be whatever it is, but the clipped output is
going to be spectrally shaped something like red noise.

Music being what it is, its spectral shaping can range from
the same spectral shaping as white noise, pink, noise, red
or brown noise etc.

Therfore, we can't make any global generalizations about
whether clipping is harder or easier on tweeters without
considering the spectral shaping of the origional unclipped
music.
Anonymous
May 10, 2005 8:56:45 PM

Archived from groups: rec.audio.pro (More info?)

Paul Stamler wrote:

>>The sums are very often out-of-the-audible range, and can be
>>therefore safely ignored.
>
>
> Not if the issue is burning out tweeters.

Exactly. The discussion wasn't about what is audible. But rather about
damaging speakers.
Anonymous
May 10, 2005 8:56:46 PM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger wrote:


> I've done the experiment, and take many kinds of music and
> clipped the !!#@!! out of it. It ends up with about the same
> overall spectral shaping of a square wave. We all know this
> is like a -6 dB/oct roll-off which is the same as the
> spectral shaping of red or brown noise. IME this happens

Oh stop blathering already. Why don't you just let people that know what
they are talking about explain it?
Anonymous
May 11, 2005 1:12:46 AM

Archived from groups: rec.audio.pro (More info?)

William Sommerwerck wrote:

> > I've rarely seen a pro amp that didn't deliver its rated rms power.
>
> There is no such thing (other than a mathematical definition) as RMS power. The
> correct term is average (or average continuous) power.

Well, that'll be a surprise for everyone that's been using rms quite happily to
measure AC voltages, currents and powers for the last century or so !

Actually *average* is also a mathematical definition.

The usage of the term average in the FTC spec is highly misleading since average
and rms power have different mathematical definitions.

For example 500W rms = ~ 600W average power ( mathematically ).

I'm afraid you're talking nonsense.


Graham
Anonymous
May 11, 2005 1:12:47 AM

Archived from groups: rec.audio.pro (More info?)

> > There is no such thing (other than a mathematical definition) as RMS power.
> > The correct term is average (or average continuous) power.
>
> Well, that'll be a surprise for everyone that's been using rms quite happily
to
> measure AC voltages, currents and powers for the last century or so !
>
> Actually *average* is also a mathematical definition.
>
> The usage of the term average in the FTC spec is highly misleading since
> average and rms power have different mathematical definitions.
>
> For example 500W rms = ~ 600W average power ( mathematically ).

> I'm afraid you're talking nonsense.


No, I'm speaking the truth. Sorry about that. Check any textbook on electronics.

Multiplying RMS voltage by RMS current produces average power. There is no such
thing as RMS power.
Anonymous
May 11, 2005 1:13:55 AM

Archived from groups: rec.audio.pro (More info?)

James Perrett wrote:

> On 9 May 2005 09:53:27 -0400, Scott Dorsey <kludge@panix.com> wrote:
>
> > In article <3e7tvsF1lq1kU1@individual.net>,
> > Joe Sensor <crabcakes@emagic.net> wrote:
> >>
> >> Are you sure about this? I always heard that using an under powered amp
> >> and driving it to distortion can kill speakers. Even a low powered amp.
> >> So this is not the case?
> >
> > It _is_ the case, because very few speakers out there meet George's
> > definition of "properly rated."
> >
> > In fact, speaker power ratings are mostly made-up numbers that someone
> > in the marketing department pulled out of their okole.
>
> And speaker ratings tend to assume a standard music/speech signal rather
> than sine waves. High frequency drivers in a system are often rated at a
> much lower power than low frequency drivers - something like 20W in a 100W
> system. With normal music most of the power is used at the bass/mid
> frequencies so highly rated tweeters aren't needed.

Except there is no such thing as a standard music signal !

Graham
Anonymous
May 11, 2005 1:13:56 AM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>
>Except there is no such thing as a standard music signal !

Yes, there is! It's the Osipov State Balalaika Orchestra recording on
Mercury! I always use it for musical testing, so it's a standard. That's
the great thing about audio standards... everybody has their own....
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
May 11, 2005 2:10:47 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Pumping ultrasonic stuff into a tweeter is a very quick way to get smoke.

Same for DC and woofers. ;-)

Graham
Anonymous
May 11, 2005 2:10:48 AM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
>Scott Dorsey wrote:
>
>> Pumping ultrasonic stuff into a tweeter is a very quick way to get smoke.
>
>Same for DC and woofers. ;-)

Yes, and for the same reason! DC resistance of a typical woofer is a good
bit lower than its nominal impedance... lots of DC can flow through there.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
May 11, 2005 2:13:10 AM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger wrote:

> Therfore, we can't make any global generalizations about
> whether clipping is harder or easier on tweeters without
> considering the spectral shaping of the origional unclipped
> music.

Or - perhaps more appropriately - any assumption made by the designers
of the speaker as to the spectral content they expected the speaker to
be able to endure !

i.e. consider the power rating of the tweeter.


Graham
Anonymous
May 11, 2005 2:32:53 AM

Archived from groups: rec.audio.pro (More info?)

On Tue, 10 May 2005 21:12:46 +0100, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

>William Sommerwerck wrote:
>
>> > I've rarely seen a pro amp that didn't deliver its rated rms power.
>>
>> There is no such thing (other than a mathematical definition) as RMS power. The
>> correct term is average (or average continuous) power.
>
>Well, that'll be a surprise for everyone that's been using rms quite happily to
>measure AC voltages, currents

Yes. Average power = RMS voltage * RMS current. It's standard AC
circuits analysis.
The sine-wave RMS voltage across a resistor, or sine-wave RMS
current through it, gives the same amount of heat (resulting from
power dissipation) as the same value DC voltage or current. The
average power is the same in both cases. The instantaneous power is
the average power in the DC case, but in the sine-wave AC case it's
sine-squared (sine-wave voltage * sine-wave current), or 1 + cosine
wave, which varies from zero to twice the average, tracing out a sine
wave (actually a cosine, or sine wave shifted 90 degrees).

>and powers for the last century or so !

No, it's only since the mid-70's or so when the FTC got involved
with the overinflated power output claims of stereo manufacturers that
the the term "RMS power" became in use.

>Actually *average* is also a mathematical definition.
>
>The usage of the term average in the FTC spec is highly misleading since average
>and rms power have different mathematical definitions.
>
>For example 500W rms = ~ 600W average power ( mathematically ).

So can you tell us the mathematical definitions of these?

>I'm afraid you're talking nonsense.

The use of RMS power is nonsense, but then the use of nonsense in
the consumer stereo industry has been constant, since well before the
term "RMS power" became common.

The power ratings and testing methods required by the FTC (or
whoever it was), as I vagely recall them, may actually be reasonable,
and results in a useful figure to compare the power outputs of
different amplifiers. But calling it "RMS power" was a mistake.

>Graham

-----
http://mindspring.com/~benbradley
Anonymous
May 11, 2005 3:13:02 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
> >Scott Dorsey wrote:
> >
> >> Pumping ultrasonic stuff into a tweeter is a very quick way to get smoke.
> >
> >Same for DC and woofers. ;-)
>
> Yes, and for the same reason! DC resistance of a typical woofer is a good
> bit lower than its nominal impedance... lots of DC can flow through there.

Plus no cooling *again* due to lack of cone movement.

The possibilities for blowing spkrs are endless !

We currently sell a range of plastic cabs that aren't too bad actually. Made in
Thailand ( I'll let you guess the manufacturer ) to a modified spec re: the
standard product that only we are supplied.

They take one hell of a hammering ( kapton voice coil formers for example ) but
the 12" unit has a weak spot. It's between the flexible lead in wire and the
voice coil. It uses an aluminium strip to make connection and quite simply it's
too high resistance - for *some* ppl it seems anyway ! Damn thing *fuses* if
substantially overdriven. Never seen anything like that failure mode in any
other spkr. Nothing else is damaged which begs the question how damn hard it
might be capable of being thrashed otherwise.

We've requested a design mod to improve it. That should up it's 'safe' amp
rating from 500W to God knows what !


Graham
Anonymous
May 11, 2005 3:13:03 AM

Archived from groups: rec.audio.pro (More info?)

Pooh Bear wrote:

>
> The possibilities for blowing spkrs are endless !
>

I think it typically involves some type of booze, though.
Anonymous
May 11, 2005 3:26:03 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:

> Pooh Bear <rabbitsfriendsandrelations@hotmail.com> wrote:
> >
> >Except there is no such thing as a standard music signal !
>
> Yes, there is! It's the Osipov State Balalaika Orchestra recording on
> Mercury! I always use it for musical testing, so it's a standard. That's
> the great thing about audio standards... everybody has their own....

LOL !

My 'torture test' for amps and speakers involves track 4 of disc 3 of a 'rave
compilation' that one of our guys once bought for this purpose. Set the CD
player on auto repeat and set the amp to just clip occasionally and let it
rip.

Then do it & 2 ohms ( to fry the amp ).

Then do it & elevated ambient temp !

If that doesn't fry something in the speaker - then there's always the Sisters
of Mercy for an interesting spectral content ! I recommend Lucretia actually.
I made a serious point with the Sisters once. I burnt out the 'standard'
tweeter protection bulb on a product we were evaluating ! Further
investigation showed that the bulb was stupidly rated and only allowed about
10W into the compression driver. Soon fixed that with a bigger and higher
voltage bulb ! In fact I entirely redesigned the crossover with more 'ample'
components. They're so reliable it's wicked. It pays to test.


Graham
Anonymous
May 11, 2005 3:51:43 AM

Archived from groups: rec.audio.pro (More info?)

Joe Sensor wrote:

> Pooh Bear wrote:
>
> > The possibilities for blowing spkrs are endless !
> >
>
> I think it typically involves some type of booze, though.

LMAO !

I have to admit to taking out a couple of RCF compression drivers at the
end of a very successful gig with a band we did sound for regularly in
what I could only excuse as a fit of exuberance !

I rarely fried anything to be honest - but I guess I just got carried
away on that occasion.

Not sure if alcohol was involved. I do recall it was an an ex-church
building though if that helps ?


Graham
Anonymous
May 11, 2005 4:36:17 AM

Archived from groups: rec.audio.pro (More info?)

On Tue, 10 May 2005 17:17:13 -0700, "William Sommerwerck"
<williams@nwlink.com> wrote:

>> I'm afraid you're talking nonsense.
>
>No, I'm speaking the truth.

Y'all are from different countries. In the Land of the Free
and the Home of the Brave, the FTC mandated a "continuous
average power" rating, that included preconditioning,
specified line voltage, yada-yada. Furrners have different
meanings.

Is that FTC ruling still in effect?

Chris Hornbeck
Anonymous
May 11, 2005 10:51:00 AM

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42811603.EF5D8F60@hotmail.com...

> > And speaker ratings tend to assume a standard music/speech signal rather
> > than sine waves. High frequency drivers in a system are often rated at a
> > much lower power than low frequency drivers - something like 20W in a
100W
> > system. With normal music most of the power is used at the bass/mid
> > frequencies so highly rated tweeters aren't needed.
>
> Except there is no such thing as a standard music signal !

E-V used to use pink noise that had been filtered so that its spectrum
represented a heavily-distorted electric guitar.

Peace,
Paul
Anonymous
May 11, 2005 11:25:08 AM

Archived from groups: rec.audio.pro (More info?)

In article <42811603.EF5D8F60@hotmail.com> rabbitsfriendsandrelations@hotmail.com writes:

> Except there is no such thing as a standard music signal !

There was a standard test signal for the IHF(m) power rating that gave
a number somewhat higher than RMS power with a sine wave, but not
nearly as high as the "music power" claims that were common in
consumer audio equipment of the day - mid 1960s as I recall. It was a
burst of 1 kHz sine wave, generally performed with one channel of a
stereo amplifier operating.


--
I'm really Mike Rivers - (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
May 11, 2005 11:36:59 AM

Archived from groups: rec.audio.pro (More info?)

William Sommerwerck wrote:

> > > There is no such thing (other than a mathematical definition) as RMS power.
> > > The correct term is average (or average continuous) power.
> >
> > Well, that'll be a surprise for everyone that's been using rms quite happily
> to
> > measure AC voltages, currents and powers for the last century or so !
> >
> > Actually *average* is also a mathematical definition.
> >
> > The usage of the term average in the FTC spec is highly misleading since
> > average and rms power have different mathematical definitions.
> >
> > For example 500W rms = ~ 600W average power ( mathematically ).
>
> > I'm afraid you're talking nonsense.
>
> No, I'm speaking the truth. Sorry about that. Check any textbook on electronics.
>
> Multiplying RMS voltage by RMS current produces average power. There is no such
> thing as RMS power.

Maybe in your country !

As I mentioned before, rms and average power are very different. Most meters measure
ac voltage and current as 'average calibrated rms' but that definition only holds
true for sine wave. The accuracy fails for any other waveform. Hence you can get
rather more expensive meters like one we have in the lab that are 'true rms
reading'.

If you want to read up on the difference between average and rms etc I believe
analog devices did a great app note for their rms converter chip.

Graham
Anonymous
May 11, 2005 11:48:49 AM

Archived from groups: rec.audio.pro (More info?)

Ben Bradley wrote:

> On Tue, 10 May 2005 21:12:46 +0100, Pooh Bear
> <rabbitsfriendsandrelations@hotmail.com> wrote:
>
> >William Sommerwerck wrote:
> >
> >> > I've rarely seen a pro amp that didn't deliver its rated rms power.
> >>
> >> There is no such thing (other than a mathematical definition) as RMS power. The
> >> correct term is average (or average continuous) power.
> >
> >Well, that'll be a surprise for everyone that's been using rms quite happily to
> >measure AC voltages, currents
>
> Yes. Average power = RMS voltage * RMS current. It's standard AC
> circuits analysis.

Over here we call that rms power, which has the same heating effect as DC power.


> The sine-wave RMS voltage across a resistor, or sine-wave RMS
> current through it, gives the same amount of heat (resulting from
> power dissipation) as the same value DC voltage or current. The
> average power is the same in both cases. The instantaneous power is
> the average power in the DC case, but in the sine-wave AC case it's
> sine-squared (sine-wave voltage * sine-wave current), or 1 + cosine
> wave, which varies from zero to twice the average, tracing out a sine
> wave (actually a cosine, or sine wave shifted 90 degrees).
>
> >and powers for the last century or so !
>
> No, it's only since the mid-70's or so when the FTC got involved
> with the overinflated power output claims of stereo manufacturers that
> the the term "RMS power" became in use.

This seems to be an American definition thing.


> >Actually *average* is also a mathematical definition.
> >
> >The usage of the term average in the FTC spec is highly misleading since average
> >and rms power have different mathematical definitions.
> >
> >For example 500W rms = ~ 600W average power ( mathematically ).
>
> So can you tell us the mathematical definitions of these?

Sure. For a simple example take 3 numbers, say 1, 2 and 3.

The average of these is ( 1+2+3 ) / 3 = 2

The rms value is sqrt ( 1^2 + 2^2 + 3^2 ) / 3 ) = sqrt ( 1+4+9 / 3 ) = sqrt (
4.6666) = 2.16

That method applies to any waveform if you integrate it. Hence average voltage is
different to rms voltage and average power is doubly so ( to the power of 2 in fact )
..


> >I'm afraid you're talking nonsense.
>
> The use of RMS power is nonsense, but then the use of nonsense in
> the consumer stereo industry has been constant, since well before the
> term "RMS power" became common.

In Europe I can only say the opinion is different simply bevcause average is the
*wrong* description.


> The power ratings and testing methods required by the FTC (or
> whoever it was), as I vagely recall them, may actually be reasonable,
> and results in a useful figure to compare the power outputs of
> different amplifiers. But calling it "RMS power" was a mistake.

Well.. the FTC didn't call it rms power IIRC.

The FTC spec sounds to me like someone attempting to use the word average in a
layman's context and forgetting that it has a mathematical meaning.

Graham
Anonymous
May 11, 2005 11:58:40 AM

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck wrote:

> On Tue, 10 May 2005 05:21:59 +0100, Pooh Bear
> <rabbitsfriendsandrelations@hotmail.com> wrote:
>
> >Actually, it's often the adhesive that gives up first.
>
> Or the VC former hitting the magnet enough to bend itself
> fatally. But, yeah, most all abuse failures are thermal, and
> clipping/overdriving the amplifier causes most tweeter
> failures. My personal experience, with my first pair (always
> mono before) of store-bought (always homemade before) of
> Smaller Advent's on the very evening that I bought them, excepted,
> playing the Yes _Close to the Edge_ album, was clearly Divine
> intervention.

I have that on vinyl somewhere ! ;-)

Graham
!