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In Reply to: My point and I do have one is virtually ANY amplifier can damage speakers posted by Richard BassNut Greene on August 25, 2003 at 14:07:16:
While your explanation makes excellent sense in the abstract it does not jive with my experience. I worked in high end audio retail for a major shop for a cumulative period of about seven (not all consecutive) years. We sold considerable numbers of fairly robust amps: big ARCs, Brystons, Levinsons, etc. The cooked tweeters we saw were very, very rarely connected to those amps and quite commonly from systems using receivers, integrated amps, or relatively inexpensive separate amps with comparatively lightweight power supplies. I can think of specific examples where the customer repeatedly fried tweeters and the problem went away when they moved up to a more powerful amp. I realize that this is anecdotal evidence and not a statistically meaningful data set, however, if you must have statistically solid data sets you might consider picking another field rather than high end audio. My trust in my ears and my experience has limits but in this case I'll go with them over your data.
Follow Ups:
I did not claim clipping harmonics have no danger at all -- but they are just a small percentage of the power needed to damage a typical tweeter.So an amplifier that never clips is theoretically "slightly safer" for tweeters ... but then it's also more likely to cause overexcursion damage to mid-range and bass drivers!
So you can't win.In the past few decades tweeters have been gradually improved to be able to handle more and more power --- ferro fluid in the voice coils really helped. In the early days of transistor amps when only 30wpc was typical and people used low-power handling paper cone tweeters -- clipping harmonics were then a considerably higher percentage of the power needed to damage the tweeters. One watt of clipping harmonics is a big deal for a tweeter than can only handle 5 watts continuous power.
Did it ever occur to you that people who have enough intelligence to make enough money to afford your high-end equipment might have learned from their experience damaging tweeters (by the time you were done with them they probably spent a small fortune buying a more powerful amp!) and as a result, they were much more careful in the future and rarely, if ever, damaged tweeters again!
Interesting note, Richard, about the less capable tweeters of yesteryear. I have never blown a tweeter. I wonder what the sound has to get like to do it. ?
So an amplifier that never clips is ... more likely to cause overexcursion damage to mid-range and bass drivers!Slight touche' there. A more powerful amp typically provides greater electrical damping. More powerful amplifiers typically need a little more SPL to blow a woofer, as compared to less power, less damping.
That's my experience. I can push a woofer to compression, which is not over-excursion; that can't come into play until the driver is out of control. I've seen over-excursion come about specifically as a result of not enough amplifier!
Along the same lines, I think also a reason why folks say that more powerful amps don't blow drivers as much is because there is typically less distortion at the same SPL. As a result of this, typically it's going to take more db to get it to tear itself up or experience over-excursion, when using a more powerful amp.
And also please don't take any of this out of context - I make no mention of melting coils here. I'm guessing that's what all the talk about tweeters is about - melting voice coils?
With woofers more powerful amplifiers are more dangerous.
Clipping harmonics would add to a mid-range driver's workload or a tweeter's workload but would have little effect on true bass drivers.Many modern subwoofer drivers, for example, could be driven at full volume with a 30wpc amplifier indefinitely with no damage ... but almost all could be damaged by a 300wpc amplifier (which should be able to produce 600wpc at high distortion levels).
Here is a cut and paste of an e-mail I received from Adire Audio whose Temmpest driver I use in one of my DIY subwoofers ... about the "danger" of driving their 15" sub driver with an often clipping 30wpc receiver:
"Richard,
Thanks for the e-mail! A 30WPC channel amp won't damage a Tempest at all, regardless of clipping. On the other hand, a 300W amp clipped heavily could cook a Tempest quite easily. Clipping is a problem in that it can double the effective power delivered to the driver, and do it with a much more damaging spectrum. However, I think the 30WPC concern is a bit overzealous."
Thanks again,
Adire Tech Support
-----Original Message-----
From: Greene, Richard (R.K.) [mailto:rgreene2@ford.com]
Sent: Tuesday, August 05, 2003 8:37 AM
To: 'techsupport@Adireaudio.com'
Subject: Clipping dangerous to Tempest driver?
While a more powerful amplifier is being repaired, would it be dangerous for me to use a cheap ($98) Japanese 30wpc receiver to drive a DIY Tempest ported Sonotube subwoofer? I expect with only 30wpc there will be amplifier clipping but I did not believe such a low power receiver could damage a Tempest driver ... until I read what a pro audio speaker expert posted on the internet
-- his post suggests to me that a 30wpc receiver could be a
"Tempest killer" even though the Tempest is rated at 750 watts power handling. Could you provide any comments on his warning below:"99.999999999% of amplifiers driving subs have feedback.
When the amplifier clips this can destroy the woofer.
It has to do with the time constants in the power supply and feedback loop of the amplifier. Watch the motion of the subwoofer cone at clipping, it will generally have a 1~2 hz component to it.It is this 1~2 hz component at rail-to-rail output (clipping)
that causes the destruction of the driver."
Thank you;
Richard Greene
A 30WPC channel amp won't damage a Tempest at all, regardless of clipping. On the other hand, a 300W amp clipped heavily could cook a Tempest quite easily. Clipping is a problem in that it can double the effective power delivered to the driver, and do it with a much more damaging spectrum. However, I think the 30WPC concern is a bit overzealous."Richard;
As it says, a 30 wpc amp just isn't powerful enough to do it. Try asking the same company about the difference between one amp powerful enough to blow it, and then another amp twice as powerful as that one. According to the above quoted text, I think you will find the less powerful of the two to more likely blow the driver.And I'll quote it again...
Clipping is a problem in that it can double the effective power delivered to the driver, and do it with a much more damaging spectrum.Man, I've really seen this - I've seen a lack of power cause clipping where a more powerful amp would not have clipped, and therefore having blown the driver!
I think it's interesting to consider the idea of using an amp that just isn't powerful enough, even when clipping, to blow a driver. I hadn't even considered it before. I'll keep it in mind. Meanwhile, do you feel like dashing off another note to Adire about what's being said here?
You speculations are wrong.
With all drivers too much power causes the damage and a small
percentage of that power could be clipping harmonics. With a subwoofer driver, however, the clipping harmonics are likely to be miniscule because fundamental tones in the 40-80Hz. octave such as bass guitar and kick drums would have clipping harmonics above the subwoofer's pass band (it would be protected by the usual 24db/octave low-pass filter).Sometimes one can point out faulty logic by extrapolating it to the extreme sduch as a 1wpc amp versus a 1000wpc amp!
One could burn out any driver I've ever used in 32 years of building DIY speakers and the other could not damage any drivers. Now you guess which is which ... because I don't have the energy to type much more on this subject, so I'll just quote someone else:From speaker tester Tom Nousaine's usenet post:
"I regularly test speakers near the burn-out point. What fries tweeters is an amplfier that has too much power. A smaller amplifier even driven into clipping is safer than a larger amplifier that delivers more power. Often a somewhat smaller amplifier is still too much but a bigger one never fixes the problem clipping or not."
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From another Tom Nousaine usenet post:
From: Nousaine (nousaine@aol.com)
Subject: Re: xmax
Date: 1998/08/14
Steve notes:
"Don't go into extremes. A severely clipped signal of 1 Watt or so will of course not damage a tweeter."
TN: That's because the tweeter is working within its power limits.
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"When an amplifier clips, most of it power goes into higher order
harmonics."TN: That's not true. Why should that be so? The fundamental is still the same frequency. True there is more power put into harmonics but not "most" of it.
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"Let's presume that in a standard 3 way system, the tweeter typically receives about 10 to 15% of the total power. When the amp clips, sending maybe 70% of it's output to the tweeter, it'll burn out."TN: No. That's not so unless the signal was 10 kHz or something. The reason the tweeter burns out because it just gets too much power. Clipping isn't the issue. Power delivery is.
But we do not need to argue this point. Tweeters are the lowest power handling devie in your speaker line-up. Therefore they are the most damaged device. The main reason that tweeters get gobbled up these days is synthesizer music. Acousttic instruments do not have any power needs at high frequencies. Synthesizers, on the other hand, can deliver full power signals at 20 kHz.
In the final analysis you are just noting that you can fry a tweeter with a 25-watt amplifier. You can also fry it just as easily with a 100-watt amplifier. Or a 1000-watt amplifier. Too much power is too much power.
People want to tell us that a 100-watt amplifier is "safer " for your tweeter than a 25-watter. It's not true. If you want to preserve your tweeter get a 10-watt amplifier. The issue is power delivery NOT clipping.
If the issue was simply clipping my original 'far out' example would still apply. I only used it to illustrate the point that the power delivered to your tweeter is the main concern. And that tweeters have low power handling capacity compared to the other drivers in your system.
I want to point out that when you are frying tweeters getting a bigger
amplifier will not solve your problem."
You speculations are wrong.I don't appreciate the apparently very egotistical presumption on your part. Here is something that has happened right in front of my eyes, and others that I have associated with in audio as well.
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I have seen a 70 watt amp driving a 12" woofer clip very hard, causing the woofer to separate into two physically distinct pieces.It goes something like this. Some detail provided for general readership. The amp is providing a sine wave acting as a carrier, and the height of that wave equates to amplitude. The motor of the driver coorespondingly travels in and out - excursion. In this case, the amp had enough power to begin to recreate the blast of a canon in the 1812 Overture, however; having completed the introduction of a sharp amplitude and a quick excursion, the amp was then exhausted. There wasn't, for a moment, any power left to continue to provide electrical damping to return the driver along it's natural sine curve. The capacity for the driver to physically provide mechanical damping was not sufficient to prevent the launching of the driver on that excursion from continuing to the point of physically separating from the remainder of the driver assembly - leaving the cone forever floating - torn and separated from the rest of the assembly.
It is not necessary for the coil to be electrically overloaded for the above type of a blown woofer to occur. Some might say this is caused by bad driver design, or perhaps one might say that amp just got a really good start. The important note is this. The driver was not electrically overloaded.
If I irritated you I apologize whether you deserved it or not.
Oops ... I just irritated you again.
I would like to irritate you for a third time by pointing out that
observing a speaker being damaged does not guarantee that one knows
exactly why it was damaged or how to prevent damage in the future ...
but if you guessed the cause was "too much power input" you'd almost always be right. True that too much power input can cause overexcursion damage before any voice coil overheating occurs.
This is especially a risk with ported speakers with high input at frequencies below the port tuning frequency.Woofer overexcursion damage is rare although overexcursion damage is a common problem for the "boombox car" guys -- that's why they often don't care about their driver's XMAX or DUMAX -- all they are interested in is XMECH = maximum excursion before overexcursion damage becomes likely.
Every woofer has an XMECH spec beyond which overexcursion damage is likely. The more powerful the amplifier, of course, the easier it will be to cause overexcursion damage. Clipping is not the cause although it is related in one way -- under conditions that cause a lot of clipping (compression of the complex A/C waveform also known as music) an amplifier's average power output will be roughly double the rated power output. Therefore, a speaker that can absorb 100 watts continuously could be damaged by a severely clipping amplifier rated at over 50wpc (producing over 100 watts continuous output).
If that was the Telarc 1812 overture with output under 10Hz.,
that is definitely one the best CDs for causing overexcursion
damage.Unless you are listening to sine waves the amp is not
"providing a sine wave".
Richard;
My God man, you certainly do type too much. You're way off topic and back onto tweeters again, and the relatively inconsequential amount of power added to the high pass when clipping the amp on the lower.I think you missed your yoga class this morning. Your points are all very well and good, but your apparent desire to avoid a point contrary to your own seems quite unbecoming to me.
I'm sticking to my story. I can rip a woofer right off the magnet by clipping an amp, and based upon the note from Adire, I am willing to bet that they wholeheartedly agree. The only remaining question, then, is, "would you?" Please, read on...
With all drivers too much power causes the damage
Edited: With all drivers, too much power causes damage. I urge you to find a way for the following statement to exist simultaneously. Clipping produces a nastier, less driver-friendly signal than when not clipping, and clipping begins with a lesser amp earlier than it does with a greater one.The fact that some amps simply do not, even when clipping, have sufficient power to blow a driver, has also been recognized. Please try to keep each point in perspective. All of these things are simultaneously true.
Get a grip!
... and annoy you some more!Most amps these days are 100 to 200 wpc.
If you had a 100wpc amp that clipped once in a while,
then a 200 wpc amp would probably clip once in a while too,
given the same input voltage.Lets start with a 100wpc amp with intermittent 9dB clipping,
-- using a 200wpc amp would only reduce clipping to 6db
-- using a 400 wpc amp would only reduce clipping to 3db
-- An 800wpc amp would be needed to entirely eliminate
9dB of clipping.The true comparison is between a typical 100wpc amp that someone owns, and perhaps a much more expensive 200wpc amp upgrade that some people may claim is "safer" for speakers.
But that "upgrade" would only reduce intermittent clipping by 3db, which probably would not even be audible.
When using a 200wpc amp, however, the probability of woofer overexcursion damage would increase compared with a 100wpc amp.
As I said, you're bearing has struck me as egotistical - just callin 'em like I'm seein 'em. Or maybe you are saving the world. Or maybe I'll just never know - comments about others present a different environment than comments about oneself. I'm just trying to add to the thread, not take your comments away. My point about you is to describe your behavior as adamant and dictatorial, not allowing other points of view in the face of your own. And I may have been unduly argumentative myself - sorry - it wouldn't be the first time! Sometimes I don't adapt at the speed of things in real time.
When using a 200wpc amp, however, the probability of woofer overexcursion damage would increase compared with a 100wpc ampIn my experience, a 70 watt amp blew a 300 watt woofer.
If there isn't enough power to blow a driver, then there generally just isn't enough to do it. In the example I had, however; there wasn't enough electrical power, and the design to some extent could be blamed - driver or system. But I also think this leads to some regard for where the wattage desired by the speaker is not the only thing to be measured. There's been alot of discussion on this. I've added a link to the discussion you previously took part in at DIYSubwoofers (and also quoted from in this thread with the Adire note), since there are comments there where the nature of the signal, and not just the wattage, play a role. This can be, and indeed has been, argued at length in it's variety, importance and effect. My current speaker system is rated at 500 watts into 5 ohms, so the equivalent of 350 to 400 watts into 8. When I get to the point where I want to replace the drivers, I will be able to test blowing them without suffering a loss. I will replace the drivers not when they are blown, but when they have experienced noticeable wear and tear.
Too much power blows a driver. A more powerful amp puts a person into a higher risk category, and in my experience audio salespersons know that and do tend to advise their customers of these risks. But you bring up a great point in the face of what may have developed into thinking by some that more power means drivers do not blow, or some such thing. I think the truth is that within the speaker's power handling capacity, such-n-such an SPL level simply sounds better. Generally, more power offers better control of the drivers within acceptable levels. It's been a learning experience to me to hear you say that wattage is everything on the matter.
I want to bring it all together into a single thought now. The most commonly blown driver is the tweeter, at say, 30 watts there. But my God, man, 30 watts to the tweeter. Either someone went ballistic with an 8K test tone, or the amount of power going to the speaker system is really high. In an overall musical presentation, isn't 80% of the power at 300 Hz or below? And when a person puts that amount of power into it, aren't they either statistically forced to be using either an ungodly huge power plant or an ungodly horrid noise coming out of their speakers? I'm not referring to the wimpier tweeters of yesteryear or of the $3 bin. I will never blow the drivers of my 87.5 db speakers. I'm hitting 105 db peaks as it is (bass) - often enough - isn't that enough? When the linear travel is through, I've still got a little space (beyond the XMAX), but I'm not going to like it, and so I'm not going to do it.
Maybe it's a little rough to say that a person might deserve a blown driver if they push it to that point, maybe a little leeway for folks who have drivers that can't handle much. My roommate has, incidentally, also experienced blown woofers in his Aiwa boom box - by it's own amp and it's own speakers. Geesh. Did he deserve it? I don't know if anyone does. It doesn't happen to me, but some folks don't seem to mind when the sound gets bad. Maybe I have my own protection circuit built in? Maybe I'm also spoiled, because presently 150 wpc has me in heaven with the afforementioed speaks. That Aiwa amp is rated more than twice the wattage as my Odyssey (but I think it's a marketing gimmick based design). Maybe I'm starting to see your position better when I start to think of folks whose speakers don't handle very much power.
I'm done, and I'm happy. Glad to give you the last word at this point, Richard.
You Wrote:
"As I said, you're bearing has struck me as egotistical My point about you is to describe your behavior as adamant and dictatorial, not allowing other points of view in the face of your own."My reply:
Thank you for the complements. I'll put them on my resume.
I believe I accused you of speculating in one of my posts,
so I guess I deserved this outburst of affection.
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You wrote:
"In my experience, a 70 watt amp blew a 300 watt woofer."My reply:
Assuming the amplifier was honestly rated at 70wpc, it should
be able to reach roughly 140wpc at high levels of distortion.
Therefore, the woofer was unable to survive roughly 140wpc
due to overexcursion I assume, and most likely was overrated
at "300 Watts" ... or this rating only referred to the voice coil's ability to dissipate heat, and didn't account for overexcursion damage. Not very useful speaker or drivers power handling specs are common in audio.
JBL Pro drivers, for example, are rated for power handling using pink noise with a 6dB crest factor and the protection of a 40Hz. 12dB/octave high-pass filter. Someone I know damaged his JBL 2235 15" subwoofer driver from overexcusion because he he didn't understand how the JBL power handling number was calculated.
He used a very powerful amplifier and had no high-pass filter to protect his ported driver below the port tuning frequency.
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