Low powered amplifiers can clip when pushed to their upper power limit, which sends out DC to the speaker. DC current melts speaker driver voice coils.
How does a speaker blow out?
I don't understand how a speaker "blows" if the wattage of the amplifier is less than the upper limit of the speaker's limit. Then again, I guess I don't really understand what "clipping" is. The amp is 22w, I was listening at a moderately high level, there was a bass heavy section in the music, and then I heard the most painful noise coming from one the of woofers. Sad.
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Well, the theory is actually that the clipping causes a square wave, which has a lot of high frequency harmonics, not DC exactly, so more likely to blow a tweeter. It can happen for a lot of reasons including age and prior abuse. There are two kind of failures. Mechanical and electrical. Mechanical means that the surround or the spider has failed, either from age or excess physical motion. The electrical failures are caused by the melting of wires in the voice coil or to/from it or a disconnect. |
What Erik said (regarding clipping), but: after a x-over passes that high freq distortion to the tweeter and burns it (typically: open), the energy that no longer has a path that way, is routed to the next highest freq driver, in the circuit. In the case of a two-way: that would be the woofer. I lost count of the number of two-way systems in which I found both drivers toasted by an under-powered amp, while in the reconing biz. Blown x-over caps, as well. Though a clipped signal isn't DC; it certainly can do as much damage. On the other hand: hearing a, "...most painful noise, coming from one of the woofers", might indicate a woofer that was driven past it's mechanical excursion limit (Xmech, per Thiele-Small), bottoming the voice coil, or: causing it to hit the gap's top edge(s). That type of damage usually resulted from boosted/heavy Bass and a vented cabinet, regardless of amplifier rating.
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Organ music can be pretty demanding, but it seems something’s amiss. I’m running a pair of KT66s in triode that produce in the 10-12 watt range, and am able to power 89db sensitivity speakers fairly loud in a large space, Granted I haven't fed them low pedal notes lately. Tubes typically break up pretty gracefully without causing damage. I do have an active subwoofer to augment the bottom octaves, but the mains still run full range without issue. What model is your amp? |
Yes, low power amps go into clipping when trying to drive speakers unless the speakers are very efficient, i.e. Horns. Also, tweeters: IF the tweeters are not capable of sudden bursts, like the Dynaudio D21’s, their voice coils can melt. These days many tweeters have ’ferro fluid’ which can absorb the heat of a burst, thus the coil does not melt. Example: amp on wrong input. Volume jacked up, then, switch to correct input: that high volume slams the tweeters coil. |
From my experience too low power (ie HF clipping) is generally the culprit behind tweeters failing, but over power (possibly LF clipping but certainly overheating the voice coil ) is why you blow woofers. Subsonics can often be the mysterious cause of over output in LF. Curious this happened on notoriously difficult organ material. |
True, but since most crossovers are in parallel, the HF voltage seen by the woofer remains the same. More likely to burn the first coil in the low-pass filter than the woofer itself, but things happen. :) The amp having less current draw due to an open tweeter circuit could mean a higher voltage though. |
After having repaired a few hundred speaker systems; I can only speak from my own experience/observations. A clipped signal and it's energy, after opening up a tweeter and having no where else to go, will end up in the x-over's, next-highest freq, driver.
Lots of blown up electrolytics, BUT- in over 15 years of repairing speaker systems (mostly: college student or Pro musician owned, it always seemed): I never once saw a burnt inductor. Some: with signs of having been abused and accompanied (in series) by a burnt driver voice coil, but- never one that opened or shorted. Perhaps the customers that clipped their amps, were just lucky in that regard. Then too: there are a multitude of systems out there, with no inductors in series w/their woofers, to block such damaging, high freq, energy. YEP (things happen)! Happy listening! |
As others have said, clipping generally causes damage to the tweeters before the woofers. If you heard a bad noise from the woofer, then it seems likely it is a mechanical failure, not an electrical failure. Does the speaker make any sound when you play it now? Is the tweeter and midrange still working? If so, and the woofer is not totally dead, then this seems like it is damage due to overdriving, not clipping. You can often tell if there is mechanical damage by gently pushing on the cone. If you feel any scraping or stiction, then you have mechanical damage. How old are your speakers? Have you always used the relatively low power tube amp to drive them? Do you use any equalization or dsp to boost the bass? |
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using low powered amps, and your want volume, but the little amp is asked to push more power than available, as mentioned sends DC to tweeter, mid, and heat destroys the coil, driver, etc. NEVER any issues with my high powered amps, just be careful downing, alcohol, it tends to make you push upper limits.
drunk ears, don't hear the tweeter, strain, nor the clipping,....if you have a clip light, or the MAC limiter, you should be ok.
just set a volume you don't cross, and your golden. my( as just mentioned today, by me) set a limit for volume which sounds good, clear, and great. don't cross the limit.
my speaks are rated 250W peak im sure, yet ive been using my 650-700 W RMS amps for a few years now, nary an issue, or problem. Just have self control when you wanna show off with friends over, and they say, is this all? don't it go louder. Most people think your at a live show, and want the floor, and chest to get a front kick in the sternum, that's not how it works, for some yes with massive wallets and a wicked speaker pair, otherwise, be gentle when ripped, or tweeters will melt.
blow a tweeter/mid on a beautiful speaker pair, or try to impress friends, or yourself.
the most accountable culprit is low powered amps which can not give you the OOOMPH, you really want. get a good power amp with headroom, 250-300 WPC+. don't look back |
Power and speaker quality are what you need i have a Krell 700fpbcx puts out 700 watts crystal clear sound 👩⚕️ paired with a set of B&W 801 series 2 these were used in most recording studios until the nautilus line came out I could rattle the windows in the house but this is just a good example of a high quality power amp matched with speakers that can handle the power |
@mikedc - When you heard that painful woofer sound, during the organ music, was your source vinyl? Asking because: subsonics, caused by stylus travel (ie: record warp, arm/cart resonance, etc) will often cause woofer over-travel and damage, in a vented system. How old is your amp? Asking because: power supply filter caps (if one has gone South/leaked electrolyte) can cause noises that simulate a woofer malfunction*, at anything above low volume. *Especially on heavy Bass notes. |
If in fact the woofer is the culprit, I would definitely call Bill at Millersound Millersound Speaker Refoaming, Speaker Reconing and Repair Services and have him repair it. They are top notch.
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@mikedc - A test* (if you haven't already): *IF your problem/distortion only arises in one channel/woofer: swap your speaker systems to see if it follows the driver. If not: it's probably the amp. |
"Speakers are approximately 15 years old and this has happened before and I have replaced the woofers." It appears that you may not be getting what you want/need out of the current setup? Woofers typically last 30+ years, so they do not appear to be having a good time with what is being presented to them. There are numerous remedies here. For one, you might consider a subwoofer to help with the low end. You can accomplish this with a compact unit that does not become an additional piece of furniture in your room to deal with. I wasn’t able to locate specs on your speakers (I tried), but remember the "3db down point" at the extremes translates into half the energy being produced at that frequency. So, say your speakers are -3db @ 45Hz that means at 45Hz you’re getting half the energy that you are getting from the "average" SPL leaving the speaker at other frequencies. So, dialing in a subwoofer @ 45Hz will flatten the response at that frequency and add atleast another octave to the usable bottom end. Also, it’s good to note that if your woofers are trying really hard to pump out the lowest pipe organ notes at, say, 22Hz the woofer is moving twice as far as it does at 45Hz (attempting) to produce the same volume of sound. This doubles the distortion at that frequency and also could "exercise" the woofer well beyond it’s comfort zone. A little hifi trivia: Back in the early days of the Bose 901s, they were rated at 270 watts, That’s 30 watt drivers x 9. The problem was that 10wpc receivers were blowing them up. So, Bose revised their minimum power rating to (if memory serves me correctly) 50 wpc.
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No, the sound spectrum has nothing at all to do with it. It's the voice coil and diaphragm that mostly determine power handling capacity. Consider the woofer, for example. The ones in my system cover just a few octaves octaves - 20 Hz to 80 Hz yet they can safely handle hundreds of watts. |