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I have had ls50s for a while and driven them with a 60/120 wpc Bel Canto integrated to good effect. I recently acquired a monster 250 wpc Musical Fidelity amplifier and I cannot believe how this thing man handles the Kefs. The woofers look like they are ready to jump out of the speakers.
I understand that under powering a speaker with an amp that clips is far worse, and I am assuming as long as things don't audibly distort I should be fine. But it is still shocking to see what these little woofers are being subjected to.
Follow Ups:
If you want to fry your tweeters, put a small amp into overload and sent a whack of distortion it's way.
If you want to cook woofers, send them raw power that they simply can't handle. They'll sustain either thermal damage or damage related to over-excursion or both. Sometimes the excursion damage is when the voice coil "bottoms out" and hits the back plate which can deform the coil causing rubbing and shorts or knock windings off the bottom of the coil causing all forms of mayhem.
If you want to get the most power out a speaker you can, send it lots of CLEAN power with an over-sized amp that will never see clipping, and then do a high-pass filter to relieve the woofers of the most heavy lifting: the stuff under 65 or 60Hz. Send that carnage off to a capable subwoofer.
Many people are surprised how blazing loud some floor-standers will go if the weakest link is sub-bass and that link is removed.
That said, if you have *1st order* acoustic crossovers, these speakers often have pretty staunch power limitations because of the very gradual rolloff rate of the tweeter. Although the tweeters and crossovers are especially designed for this, I don't think you're going to get the kind of levels one would expect from a 4th order acoustic design.
On the other side of fun, you have super-efficient speakers. I have a set of three-way PA speakers - 15" woof, 10" mid and a 1" compression driver on a 5x15" lense. These things are over 100db 1W/1m sensitive. I used to run them *comfortably* at home using a 40W/channel JVC receiver.
It's amazing how little power you need with super sensitive speakers!
Cheers,
Presto
pretty easy if you get them drunk first.
....it's easier to damage a speaker with too little power than too much.
Oz
Don't worry about avoiding temptation. As you grow older, it will avoid you.
- Winston Churchill
That isn't entirely true. It depends.
Too little power may result in the amp producing excessive distortion or even clipping, which results in excessive high frequency content, which can result in overheating the voice coil, especially HF drivers.
On the other hand, "too much" power allows the amp to pass the signal more-or-less faithfully, and if the speakers are played near their output limit and the signal contains significant peaks in the waveform (which is often the case when a recording has little or no peak limiting), a peak may cause the driver suspension or voice coil leads to move farther than it can, and break. This can be a problem with "audiophile recordings" when the listener wants to "crank it up".
:)
I worked at a couple of dealers in my hi-fi career that repaired gear. I never repaired a speaker that was driven by a tube amp and this is repairing hundreds of speakers over the years. It was almost always overdriven SS Amps. One guy over excurted with clean power and broke the wires from the terminal to the cone.
I never like to say too little power I like to say clipped SS amps which are like dc as they heat and roast voice coils. 99 out of a hundred it was a roasted vc. Tweeters were sometimes harder to figure out what happened but also less rugged of course.
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
If we are talking about someone that knows a tad about audio shouldn't they know the power ratings of their speaker / amp setup.
I always felt that "cranking it up" wasn't such a good thing anyway. I'm not talking about upping the volume for some Rock to "groove to" if "That's Your Bag Man" (and other bad 60's sayings). If you're clipping your amp or freaking out your speakers then switch it to headphones.
I just like to "mellow out and be one with the cosmos lest the Fuzzy be hassling me and bumming my trip".
It was easy to put twice the rated power or more into most speakers as long as it was clean and you didnt add lf equalization. I remember putting all 225 watts into PSB Alpha B's. We regurlarly tested new speakers that came in to our store by putting them to the test!
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
Edits: 07/25/16
With just a quick look KEF gives the LS50 suggested amp size of 20-100 watts, so some care should be taken with the volume control of your new amp if not wanting damage to the speakers.
There is something called Xmax, the throw of the woofers coil. If your amp for what ever reason is exceeding the cone/coils limits it can or will be slamming against the housing. Eventually bad things will happen if that is the case.
You gotta too much juice!
Xmax generally refers to the amount of linear excursion, before the coil is too far out of the gap and the speaker distorts. There is also a mechanical Xmax, but it's not specified as often.
Damage from over-excursion can happen at low frequencies, but burning the voice coil can happen at any frequency.
I had a friend (that was years ago!) in the late 70's that bought a new big Sansui monster integrated amp. Unfortunately the speakers he ordered with the amp didn't arrive yet. So he cranked up some Zepplin on his old speakers and you could actually hear the coil banging against the housing. Eventually it did stop. Unfortunately his speakers didn't arrive for another few weeks. It sucks when you're 18 and (with joint in hand) you're sitting there with a new toy and unable to play with it.Eventually the coil rub with trash it.
Edits: 07/24/16
I think he is describing more movement but controlled movement. So to the OP are you talking of quick controlled movement or sloppy, slow movement that doesnt seem to match the program material playing? Do you play vinyl and know what a woofer moves like when trying to reproduce rumble and subsonics? Im betting the former and things are fine.
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
Foam surrounds on a pair of Acoustic Rsearch speakers gave way during a particularly loud listening session. They were probably getting a bit brittle with age anyway...
It's actually fairly hard to do, unless you push the driver beyond its comfort zone. ;)The two primary failure modes for drivers are over-excursion and over-heating. Over-excursion occurs when you ask a driver's suspension to move farther than it can, so it breaks (typically either the spider or the surround is torn away from the basket or the diaphragm). Over-heating occurs when a driver, well, over-heats, so something melts (typically the insulation on the voice coil wire). This is a simplified basic explanation. Both failure modes can result in other types of damage - deformed voice coil, loosened dust cap, ...
Unless you're playing your speakers louder than before, or aren't comparing the amps using the same recording, or there's another variable which you haven't mentioned, it seems possible/likely that your new amp is delivering the low end better than your previous amp.
:)
Edits: 07/23/16 07/23/16
does it happen with both digital and LPs? If it's only LPs, it's probably record warp and the bass reflex loading of the KEFs. A reflex speaker woofer can become unloaded at low frequencies like those of record warp and the only solution is a high pass filter or stuffing the KEF [ports which, of course, changes the speaker response.
You nailed it, I am accustomed to having a rumble filter engaged and the integrated phono stage does not have one. Wow, I have never seen woofers go nuts like that before! The amp is definitely punchier as well, but this is absolutely rumble.
I am going to look into a subsonic filter, thanks for your post.
Thanks
missing from a lot of minimalist designs (preamps and Amplifiers)
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius
"or there's another variable which you haven't mentioned,"
Ah, yes. You neglected to mention that you were using a subsonic filter on the previous amp, but not on the new one. Kudos to Hahaverizon for deducing that.
You would do well to inquire in the Amp/Preamp or Vinyl asylum to find out about ways/products to insert a subsonic filter into your system. Personally, I'm only familiar with putting a parametric or graphic EQ between the preamp and power amp, and that may be overkill for your needs, unless there are other frequency response issues you'd also like to improve.
:)
could it be that you are now using an amp that supplies better low end?
It might be the Bel Canto has a higher damping factor than the MF. A low damping factor will do that with some speakers.
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