Speaker wattage question


I'm new here, so I hope I'm posting this in the appropriate forum.
I am running KEF LS50's with a Parasound Integrated amp. The amp is rated at 165 WPC @ 8 ohms. The speakers are rated for 25-100 watts (and are possibly lower than 8 ohms according to some sources).
If pushed, do I risk damaging a driver, or will I simply get clipping?
Any help appreciated and please pardon my ignorance on something I'm sure is common knowledge.
chrisg1000
I am running KEF LS50's with a Parasound Integrated amp. The amp is rated at 165 WPC @ 8 ohms. The speakers are rated for 25-100 watts (and are possibly lower than 8 ohms according to some sources).
If pushed, do I risk damaging a driver, or will I simply get clipping?
yes, if pushed, you risk damaging your tweeter (before you damage your woofer). The amp will not clip since it has 165W/ch & plenty of current drive (that's usually the case for Parasound amps). The speaker will start distorting indicating it's been over-driven &/or broken. 
I'm thinking that you are not going to use more than 10W/ch from your amp at usual listening levels. The transients will be much higher but for much shorter duration. SO, then, it becomes a question of reliability - in how much time will your LS50 fail when you keep pushing more than 100W into your LS50 repeatedly over a period of time? I don't have an answer for you other than a fuzzy "long time".
Don't get too enthusiastic with the volume knob & you should be fine, I believe.  
Any speaker has limits, and modern speakers generally are going to be way too loud for anyone nearby to enjoy before those limits are reached. Your 165 watt amp will be using far less than its max before the speaker seems to be screaming, and if you push a SS amp too far it can certainly damage the drivers from the distortion that shows up eventually. Kind of like driving a sports car…you know it might be fast, but a sharp corner at 120 might be less of a good idea. Clipping a 165 watt amp means you're drunk and attempting to get your dinner party guests to twerk or something, or you sat on your remote, but with your rig you should get some nice sound before any issues come up…with SS amps the good news is the distortion is at the end of the power limit and generally results in clean "head room" which is fine for all but the wimpiest drivers. I have a much older pair of KEFs (Q10s…ancient) that I've never driven hard enough to hurt 'em…luckily…they still work perfectly as deck speakers and have been subjected to SS slam frequently…within reason.
If pushed, do I risk damaging a driver, or will I simply get clipping?
In my experience, most speaker drivers will blow because of clipping.  Yes, you can send to much power (wattage/current/voltage) to a speaker and pop it, but normally clipping is the issue.

With your rig, it would be INCREDIBLY loud, way before you do damage and you would surely turn it down long before this happens.
With high-powered amps, you can damage speakers with both prolonged high volume listening, where the heat from current running through the voice coil will do the damage, or from short, very intense bursts of power that are typical of accidents, such as leaving the volume knob all the way up, or accidentally unplugging or plugging in an interconnect when the amp is on.  
Thanks, all. I appreciate the responses!
Clean power is key.. Its not at all uncommon to have more power then the speakers are rated to handle use it wisely( i have 275w a side at 8ohms into 6 ohm spkrs rated 50-200 w) .There's nothing like more cowbell :)
also most not all amps are clipping long before the volume is all the way up ..not all but many..
enjoy

@chrisg1000 The key is to be sensitive to the sound quality.  The speakers will first compress, then distort, when you approach their real limits.

Keep them sounding well and you can attach a 2,000 watt amp with no problem. :)

Best,


Erik
Speaker wattage ratings are generally meaningless.  The two key specs are impedance and sensitivity when matching an amp to a pair of speakers. 

As others have pointed out, you have a quality amp with more than enough power to drive your KEF's without fear of ever clipping.  The sheer volume level alone would cause you to back off on the knob long before you ever start to approach clipping with your Parasound. 

Low powered amps driving difficult loads destroy speakers by clipping.  Not high powered amps like yours.  Don't worry about it and enjoy your system.  I bet it sounds great!
paraneer

Speaker wattage ratings are generally meaningless. The two key specs are impedance and sensitivity when matching an amp to a pair of speakers.  
  Add to that a third, any high negative phase angles at low impedance's as well.

Cheers George
paraneer
639 posts
08-10-2016 5:09pm
Speaker wattage ratings are generally meaningless. The two key specs are impedance and sensitivity when matching an amp to a pair of speakers.
I wouldn't say that speaker wattage rating is generally meaningless - it does have a function. And that function is to generally make the user aware how much wattage the cone drivers can handle before they start distorting. Even tho' one is going to hit those max wattage numbers infrequently, one needs to be aware of the max wattage handling or one is going to break/fry/destroy the driver(s) with too much power. Personal experience confirms this. If the max wattage handling of the speaker was not mentioned one could do a lot more damage more quickly than if this spec was stated - i.e. you know whether you can go all out with your amp or not. For example - my DMT10 speakers can handle 350W & they are connected to a 120W/ch amp. I know that even i crank the volume to max, i will not destroy the drivers. OTOH, my Scintillas can handle 200W max so I cannot crank the volume to max as my amp can output 1100W into 1 Ohm. If I didn't know this I'd have fried the ribbons by now....

I agree with you that speaker wattage handling spec is not what one uses to match amps to speakers.
good additional point by georgelofi.  
Look at this review and you can see that the reviewer used a pair of Anthem Statement M1 monoblocks which are rated at 1000w.

http://www.soundstagehifi.com/index.php/equipment-reviews/557-kef-ls50-loudspeakers 

" Then, for the heck of it, I tried the LS50s with the Copland CTA 506 ($6000), a tubed stereo amp that puts out 90Wpc into 16, 8, or 4 ohms; as well as a pair of Anthem Statement M1 monos ($3500 apiece), a proprietary class-D design capable of unbelievably high power (1000W into 8 ohms). The sound was slightly different with each amp, but one thing remained the same: the diminutive LS50s sounded much bigger than their size let on. I also learned that, with any of these amps, the LS50s could play loud -- louder than I expected from speakers of their size, and louder than I really needed them to."

Unless you get really crazy stupid loud with your Parasound, I don't think it's 165w/channel will be a problem.

Bill
bombaywall- That's my situation. I had a NAD Viso Five @ 65 WPC, so I knew I never had to worry. Now I possibly do.


So, the general opinion is that if I hear distortion, turn it down. Otherwise I should be fine?

And, willand, they do play loud. The sound is much larger than their size would let on. I'm pretty blown away. That's why I'm asking this question. They sound fine very loud, but I don't want to cause damage.
Chris, Lots of good information above.  Just to expand on a couple of points - music in general has relatively little energy at the frequencies handled by the tweeter and these drivers are not designed to handle a lot of energy.  Once an amplifier is pushed into clipping it begins to generate harmonic distortion.  The distortion products relevant to this discussion are caused by the summing of fundamental frequencies in your music which produce higher frequencies.  Harmonic distortion is present in all equipment to a (hopefully) small extent but in most clipped amplifiers this distortion increases dramatically.  Your speaker's crossover dutifully routes any of these signals higher in frequency than the crossover point to the tweeter, increasing the likelihood of damage.  This is why the interaction between  your amp and speakers (impedance and negative phase angles), especially in the frequency ranges where most music - or the music you listen to - resides and why it's important to know your speakers impedance characteristics (see JA's measurements in Stereophile) when matching an amplifier.  As has been said many times, far more speakers have been damaged by pushing an underpowered amp into clipping than by playing a powerful amp loudly.  Dick
Harmonic distortion is present in all equipment to a (hopefully) small extent but in most clipped amplifiers this distortion increases dramatically. Your speaker’s crossover dutifully routes any of these signals higher in frequency than the crossover point to the tweeter, increasing the likelihood of damage.
well explained djohnson54. One point that djohnson54 made that i’d like to elaborate on - when the amp goes into clipping, the output music signal looks like it has lopped off tops & bottoms. The lopped off top comes from the fact that the output voltage maxed out to the B+ power rail. Anytime you have a music signal with sudden changes in amplitude it is like having a high frequency content in that signal. Sudden changes in amplitude = amplitude changes happening fast = high frequency content. So, it is this high frequency content that is dutifully passed onto your speaker’s tweeters (x-over is simply just doing its job). And, like djohnson54 wrote, the tweeter is not designed to handle high(er) power as there is not much hi freq energy but the clipped signal from the power amp does have high(er) power. And when this hi freq distortion power exceeds the tweeter’s power handling capacity, you fry your tweeter.....
Per the "danger of clipping" comments already seen here, the off-take is that you're more likely to damage a tweeter with an underpowered amp driven too hard than you are with an amp that has "too much power".
Why do speaker manufacturers put it in the specs when you can possibly drive anything with 1000wt of clean power?
inna2,182 posts08-11-2016 5:49pmWhy do speaker manufacturers put it in the specs when you can possibly drive anything with 1000wt of clean power?

Inna, i think that you misunderstood. You can drive any speaker with 1000W/ch but it does not mean that you can crank up the volume indefinitely. If you do, you will fry the tweeter & eventually the woofer. So, you can use a 1000W/ch amp, just be careful of where the volume knob is & do not exceed the manuf's speaker wattage upper limit. it's not so much about "clean" power i.e. just because it's clean it wont damage the speaker. No, not true.

If the speakers are rated to be able to handle 200 watt/ch continuously and I am using 1000 watt/ch amp, how do I know where those 200 watts are, speaking of volume? 
@inna

The SPL at a listening location is a function of the speaker sensitivity, room acoustics and distance from the source.

You could measure the SPL at 2.83 volts (1w/8 ohms) with the mic at the listening location and then do math from there if you really wanted to. :)

Divide your maximum RMS voltage by 2.83 and convert to dB. Add this to the SPL measured at the listening location and voila, you have your maximum SPL.

inna
2,183 posts
08-11-2016 10:46pm
If the speakers are rated to be able to handle 200 watt/ch continuously and I am using 1000 watt/ch amp, how do I know where those 200 watts are, speaking of volume?
what erik_squires wrote is correct. 
Another method to do the calculation is as follows (you'll find this in several other of my posts in other Audiogon threads):

Say, your speaker is 90dB SPL at 1W, 1m & your speaker is 8 Ohms.
Since it's 8 ohms we are sure that 2.83Vrms into 8 ohms produces 1W of input power.
The SPL with drop by square of the distance from the speaker.
So, if you are listening at 3m (~10' away), the resulting SPL = 81dB.
There is approx 3db loss due to furniture, curtains, carpet, walls absorption.
There is a 3dB increase due to listening in stereo. So, the absorption & stereo effects essentially cancel out. 
You have 81dB SPL at 3m using 1W.
you have 91dB SPL at 3m using 10W.
you have 101dB SPL at 3m using 100W.
you have 104dB SPL at 3m using 200W.
you have 111dB SPL at 3m using 1000W.

using the metric above & your RadioShack SPL meter you can gauge when you have reached the 200W mark approximately (pretty decent approximation). Does this make sense?

The power recommendation given by the manufacturer is just a rough guide of the kind of amplifier that should be used with the speaker.  Those numbers do not necessarily mean that the speaker is capable of operating at sustained levels as high as the top wattage rating.  The top end number is probably chosen to limit the possibility of damage even from short term events, such as a loud accidental pop, and I highly doubt that a speaker like the LS50 can take 100 watts for anything but the shortest period of time.  I would not want to put too powerful an amp on a speaker for fear that some event might cause such accidental large transients that could damage the speaker even though I would never actually try to run the speaker anywhere near the full output of the amp.

While it is most common to damage speakers with sustained levels of high output (overheating the voice coil), one can also damage speakers with very strong short-term transients.  I recently spoke with someone who damaged a tweeter by playing a classical recording that had extremely wide dynamic range (I have a few of these, and they come with a warning about the dynamic range), while not playing them at a very high average volume.

As to the idea that one is more likely to damage a tweeter with an underpowered amp driven into clipping than by excessive clean power from a too powerful amp, I spoke with a manufacturer who said that, by far, there are more instances of damage from use of too powerful amps than from clipping underpowered amps. 

I would personally stick with amps more toward the lower end of the recommended power range because I don't do that much loud listening and I find that lower-powered amps tend to sound better than higher powered amps, provided that the speakers are suitable for the lower-powered gear. 

My speakers are rated 15 watt - 200 watt. Before I was using 60 watt amp, now using 120 watt, and it is definitely better, though the quality of the current amp is higher as well. I sometimes listen to jazz/rock fusion at relatively high volume for couple of hours straight - nothing happens. The amp feels very relaxed and so do the speakers. In the case of the speakers that I have I wouldn't want to stay closer to the 15 watts than to 200 watts.
That math is too complicated for me. But the question was not about the precise figures but about real life situation and the position of the volume control. Anyway, I guess that this is the kind of situation when you cannot just rely on your hearing not to damage the speakers.
It appears that as it is often the case there is no general answer, it all depends on the particular application. One thing is certain though - when choosing speakers first choose quality drivers not nice cabinets and fancy crossover work.
That math is too complicated for me. But the question was not about the precise figures but about real life situation and the position of the volume control.
sorry. I thought i had simplified it as much as i could. 
Well, one thing you could do it measure the SPL at your listening position with a RadioShack SPL (or any other) meter & see at what volume knob setting you are getting 91dB SPL average (which corresponds to 10W), 101dB SPL average (which corresponds to 100W) & what the peaks are at each of those volume knob settings. That will tell you how much you can crank it up & be safe with your speakers.

One thing is certain though - when choosing speakers first choose quality drivers not nice cabinets and fancy crossover work.
mostly true. Remember that cross-over networks can make or destroy your speaker. I.E. you could have quality drivers in your speaker but a really crappy, current hogging x-over driving those quality drivers & you will end up with an overall shitty speaker.
In the end, the quality drivers, the x-over & the cabinets are all tied together. It's difficult to separate them as individual pieces. Another example - you could have quality drivers, a 1st-rate x-over network but your cabinets side-walls could be weak & resonate too much w/ the music. Once again, the result will be shitty (with too much bass boom/overhang) & you would have wasted your $$ on quality drivers + x-over in an ill-designed cabinet.
All 3 items you wrote need to work in compliment w/ each other for the speaker to be sounding its best.
Yeah for sure don't buy a fancy speaker cabinet when you know that the drivers aren't top quality. 
Of course, all three elements must come together to make good speaker, but drivers come first, that's the start.
Hi all, I know 165 watts sounds like a lot but it is not a huge amount.

The way to think about this in my opinion is in dB.

100 watts into 8 ohms is a 20 dB amplifier  referenced to 1 watt of power and you add that 20 dB to the 1 watt efficiency of your speakers.  
When talking power 3 db is twice the power so 165 watts is close to 23 dB added to the 1 watt efficiency of your speakers.
a 1000 watt amp is 30dB of power.
So if you decide 1 watt is the reference power level
Then 10* log of (RMS wattage of your amp) is how many dB it adds to the 1 watt efficiency or sensitivity of your speakers.
If you do that with your 165 watt amp you come up with 22.16 dB added to say 90 dB for a total sound pressure level of 112.16 dB at 1 meter.

General rule of thumb if your speakers sound clear you aren't putting in too much power if they sound distorted you should turn it down and see what is going on.


This is how JBL determines maximum power level and it is run for 8 hours to sense failure not distortion.
https://www.jblpro.com/pub/technote/spkpwfaq.pdf

other companies may do it differently.


You can always install a fuse on the speaker cables to insure that you won't damage them...