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In Reply to: Kindly Disagree... posted by Todd Krieger on August 25, 2003 at 14:07:14:
Not that it matters.Please define "underpowered amplification" and
"sufficient power" in a way that could help fellow audiophiles
convert those terms into specific rms watts per channel
for their speakers.Did it ever occur to you that "minimum power recommendations"
may have more do do with the sound quality provided by the speakers?
You are speculating on what the words in the owner's manual really mean. The fact is clipping harmonics from music can only account for a very small perentage of the rms power needed to damage voice coil wires/adhesives. It's just a coil of copper wires glued to a cylindrical former -- so in plain English, only too much electricity can do damage ... and clipping harmonics are just a very small percentage of the electricity, so they should receive only a very small percentage of the blame.Nationally known speaker tester Tom Nousaine on "underpowered amplifiers" from a use net post (see link):
"You won't protect your speakers by using a larger amplifier.
It will just burn them out as fast by supplying more power no matter what the condition of the signal." TOM NOUSAINE
Follow Ups:
According to the Rane article, under powered amps are more likely to blow tweeters. The answer is not because of clipping, it's due to compression according to their research. Because the amp compresses the low end signal, the user doesn't notice the volume increase as much, but rather should notice an increasing brightness. In any case, the volume can be continued to be applied until the amp clips at 100 watts on the high end easily over powering and burning out the tweeter."If you overdrive the amplifier by 10 dB, the high frequency
amplitude goes up by 10 dB. This goes on dB for dB
as you turn up the volume, until the high frequency reaches
the 100 watt level. Meanwhile the peak level of the low
frequency portion can not increase above 100 watts (See
Figure 4). This now represents nearly 100% compression (no
difference between HF amplitude and LF amplitude).
vol. 38, pp.34-39 (Jan-Feb, 1990)"Their solution was to build in limiting. So, volume is the culprit, but using an under powered amp would be more likely to encourage the listener to abuse the speaker because of compression. This of course excludes people like my brother that blow tweeters because they just want to see how loud it will go before it breaks.
Do you really think I'm so dumb as to post a link that contradicts what I posted?
Don't answer that!What the link explains is that even if bass transients are clipped,
the treble is not and will get louder and louder as you turn the volume control clockwise so eventually the tweeter will fail.But the same thing will happen if you turn the volume control clockwise with an amplifier that never clips at all.
The only difference is the clipping harmonics that make the treble slightly louder and much more harsh sounding without you touching the volume control ... but only when there is clipping ... which is almost always intermittent when playing music.
A small quantity of clipping harmonics gets through the high pass filter to the tweeter -- the article calculated 1.4 watts for a severely clipped 100 Hz. sine wave which they represented by a 100Hz. square wave. And further, they assumed a 1000Hz. turnover frequency. For home speakers playing real music, not sine waves, and a typical 2000Hz or higher turnover frequency for the tweeter, the clipping harmonics are likley to be much less than 1.4 watts -- I was being very conservative in estimating one watt.
In plain English the article says treble too loud for too long = tweeter damage. The article speculates on what listeners would notice ... in a way that promotes sales of Rane limiters.
It's my opinion that the "warning effect" of an audiophile hearing
harsh clipping harmonics and then wanting to turn down the volume or at least not make it any louder ... at least offsets the slight danger of one watt of intermittent clipping harmonics. With no clipping at all, the treble sounds better ... but the tweeters are still damaged if they play too loud for too long.At least clipping gives some warning that the music is much too loud and speaker damage is possible. Of course if everyone is drunk at a party, no one would notice.
I can read just fine Richard.What the article states quite clearly it that when an amp compresses, it tend to damage the tweeter because it continues to supply power to the higher frequncies. What you're denying is that this is more common with under powered amps. If you're familiar with amps that clip nicely and compress when over driven, then you'd know that the user doesn't get the perception that the music is getting that much louder. Even if druck at a party, if the amp can deliver the power to sound louder, then it's less likely to get over driven into compression or clipping to the point of over driving the tweeter.
I've repeatedly stated that clipping harmonics can make lower power amps slightly more dangerous to tweeters than higher power amps.Assuming the listener plays the treble at exactly the same volume, the clipping amp will produce slightly more treble output from the clipping harmonics of bass and mid-range transients without one touching the volume control -- with real music this is likely to amount to 1/2 to 1 watt of intermittent clipping harmonics, which would be only a small percentage of the power required to damage even a cheap tweeter.
So I assigned 5-10% of the blame for tweeter damage to clipping harmonics.
But the typical "buy a more powerful amp" advice given to someone who has blown tweeters does not work. Some people do get conned into spending a lot of money on more powerful amplifiers. And maybe they will never damage tweeters again. But let's not be so fast to credit the new amplifier -- people who damage tweeters learn from their mistake and usually are more careful about playing LOUD music in the future (I had a tweeter-blowing experience as a teenager in the 1960's and have been much more careful since then = no tweeter damage in the following 35 years).
The reason this "buy a more powerful amplifier advice" does not work is because the new amplifier (assuming it NEVER clips which is probably not true) can only play the treble slightly louder than a clipping amp before the replacement tweeters will be damaged!
(No clipping at all but the tweeters will still be damaged ... although the "good" news is the treble will sound better ...
before the tweeters are damaged this time!"When voltage peaks of bass transients or lower midrange transients are clipped, the average power increases. The music is somewhat compressed ... and just like a compressed dynamic range TV commercial, the music sounds LOUDER. True that the kick drum hits can't reach higher dB's as you turn the volume control clockwise if the voltage peaks are being clipped ... but the guitars and cymbals and everything else can continue to get louder (as the average power increases).
Our perception of loudness is based mainly on the average dB's (power level) -- haven't you ever noticed how LOUD compressed TV commercials can sound -- that's from the high average dB (power) level.
The danger to tweeters from clipping harmonics coming from a clipping amplifier is comparable to turning up the volume slightly with a
non-clipping amplifier. That's why a "more powerful amplifier" accomplishes little -- it doesn't address the root cause of tweeter damage = treble played TOO LOUD for too long!
I have learned about underpowered amps taking tweeters out the "hard" way- in my *own* system... Several times, in fact...When it happened to me the first couple times, I did not realize an underpowered amp was causing the problem. Then Rudy Stoklos, head of Saras of America, found out I was using a 30-watt receiver to drive his speakers, he went on a verbal rant about under-powered amps clipping and taking out tweeters. I then went to a 70-watt Amber Series 70 amplifier, and I never blew out a Saras tweeter again.
All I am doing is attempting to save people the grief in making this mistake. If you think that's "wrong," oh well...
There are a lot of people I respect in regard to audio advice, but Tom Nousaine is *not* one of them... (I know him very well from rec.audio.)
Anecdotal evidence is not a very scientific analysis of the relationship between maximum amplifier power output and speaker damage. There are far too many variable involved.
For one example, did it ever occur to you that after damaging tweeters you became more careful about playing music at high volumes in the future? And had you simply stayed with the 30wpc amplifier and been more careful with the volume control, your tweeters would have remained intact in the future too?When I was a teenager in the 1960's I blew out a University horn tweeter from excessive volume and it cost $50 to replace, which is equivalent to about $250 in 2003 dollars ... so I learned my lesson and never blew a tweeter in the following 35+ years.
So what does that prove about amps and tweeters?
Nothing!I did say that clipping harmonics account for roughly 5-10% of the power reaching tweeter so did not imply they have no danger.
In my mind is a typical 12dB/octave 2000Hz. or higher crossover frequency. The danger to tweeters would increase if the tweeter couldn't handle much power, used only a 6dB/octave crossover slope and had a relatively low turnover frequency. But rms power would still be the primary cause of damage by far - not clipping harmonics.All other things equal, if you had massive clipping, let's say 10dB, using a 30wpc amplifier, then you'd still have 6dB clipping using a
70 wpc amplifier. That's not a big difference.Taking your popular but wrong "clipping is dangerous" theory to the extreme:
-- Would you say if eveyone used a 1000wpc amplifier that never clipped, we would never have damaged tweeters again ... and if everyone used a 1wpc amplifier that clipped heavily all the time, we'd hear horror stories of blown tweeter's every hour?
I think you two might be arguing two different points, actually. And it seems like at one point you were confusing talking about power to a speaker as a system as opposed to using the term speaker to refer to a driver....... Anyway, read the link for a good primer, which pertains to all speakers, not just the brand and type in the article.
Speakers consist of one or more drivers.
The term "speaker" communicates better than the
term "driver" to most people.My link provides data, rather than speculation.
I know you're thinking: "YOU know more than JBL?"
Well folks, the "Don't use an underpowered amplifier"
warning has been used for many decades to help sell expensive
powerful amplifiers! And it works too!When that article was written a long time ago when JBL did sell amplifiers (they may not anymore). Did you ever consider that back then JBL had a financial interest in selling more powerful pro amplifiers ... not to mention that pro usage is not comparable to home audio. Today, pro sound production companies can monitor speakers and amplifiers real time via computer links to built-in sensors in the equipment, not to mention using limiters that immediately cut power to prevent clipping. They take no chances.
Of course clipping distortion sounds bad, so who wants to listen to that?
And even a small amount of clipping harmonics reaching a tweeter can be bad news in very-high-SPL-close-to-the-edge pro situation where reliability is absolutely the top priority, not sound quality -- so why take even a little more risk? If the speakers break, the audience is liable to turn on the sound engineers and beat them up!
Even the Rane article in my link is slanted toward convincing readers to buy Rane Limiters (rather than providing the common sense advice "just turn down the volume", which I wish they would do more often in pro sound reinforcement) but at least there is useful data provided, while the ancient JBL article does not provide any data at all to support it's conclusions.
"... not to mention that pro usage is not comparable to home audio"Sorry, I flatly reject that; in fact, besides that all the physics are the same, the longer I am at this the less distinction (and need for distinction) I see.
As for the JBL article, no, I don't believe by any stretch that they wrote it to sell higher power amps; they wrote it to lower warranty costs, as did Klipsch, etc.
"Today, pro sound production companies can monitor speakers and amplifiers real time via computer links to built-in sensors in the equipment, not to mention using limiters that immediately cut power to prevent clipping. They take no chances."Yes, I know that, and I know that that pro sound people still know the value of sufficient power.
Anyway, here is another newer doc that describes recommended power based on speakers input rating. But then again, maybe they are just trying to sell something..........
I've read dozens of the articles on the JBLPro site over the years -- I especially like the one at the last link you provided because it explains how JBL rates woofers' power handling using a 40Hz. 12dB/octave high-pass filter to protect the drivers, which is fine for pro sound usage ... but many people up until a few years ago bought JBL 2235 and 2245 drivers for ported home DIY subwoofers
and used no high-pass filter protection at all because they wanted to hear/feel 20Hz. from their subs. So the JBL power ratings intended for pro use had low correlation with home usage as subwoofer drivers w/o high-pass filter protection. That's just one more example of differences between home and pro usage.For home usage, a 100 wpc amp with massive 10dB clipping oif bass transients could be replaced by a 200wpc amplifier ... and then there would only be 7dB clipping with the same input voltage, all other things equal. That would make little difference to the tweeter.
And the data in the above paragraph has no meaning at all for pro use
where limiters are always used.
Yeah, I HAVE ported JBL 2245 for home sub use, with a few caveats; I have never blown a single driver/system in my life, always had a pretty good sense how hard/loud I was pushing it; I don't run anything NEAR the rated input into most drivers; the sub is tuned to 28.8 and I don't try to get 20 hz; and I often use an amp with built in variable high pass, usually set to 30hz. Thanks for the reply.
MBB
The 2235's and to a lesser extent the 2245's in ported enclosures or infinite baffles could suffer overexcursion damage when one misunderstood the JBL power handling ratings. Very popular drivers for Michigan DIY subwoofer builders, especially infinite baffles.
The 2245 is a classic subwoofer driver -- not until recent years did the 18" Aura / North Creek Leviathan surpass it (for only about $800 each!!!)
Yes, I have been insisting that some of us are arguing different points, and certainly not answering the poster's question. Your link is a good one.
For the question that the original post asks, there is absolutely no danger whatsoever.
I owned ADS 410 speakers for about six months in the early 1980's.
Gave them as a gift to my sister-in-law. One time a few years later during a party she cranked up those little speakers very loud for a party in their large house which eventually blew both tweeters.
The Sony integrated amplifier I had also given her was either 40
or 50 or 60wpc -- I can't remember over 20 years later.Well since I'm such as nice guy, I bought two exact replacement
Audax dome tweeters for something like $30 each as a gift and installed them with the warning:
"Too LOUD for too long = goodbye tweeters ...
and I'm not paying for the next pair".Well the sister-in-law was a lot more careful after that incident and the ADS 410's were never damaged again and are still in use today.
And still sound pretty good too.Now the ADS 420's may be completely different than those ADS 410's which used a 7.5" Audax woofer and 1" dome Audax tweeter ... but the lesson is still the same -- almost any receiver can take out a tweeter if the volume control is turned too far clockwise.
To say there is absolutely no danger at all is not true.
If the receiver was only 3wpc there would probably be no danger.
nt
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