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Old 4th November 2006, 03:22 AM   #1
Bob0513 is offline Bob0513  United States
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Default Power output vs speaker power handling

Hello everyone,
What happens when a chip capable of driving 50W drives a speaker only capable of 20W? Does the speaker blow or does the amplifier only put out 20W? If the former is true, how can one implement a safety device to prevent any damage?
Robert S.
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Old 4th November 2006, 03:27 AM   #2
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Yes,a 50W amplifier could blow a 20W speaker.
The best protection is to go easy on the volume control.

Also,I've seen cases of 25W amplifiers frying 60W speakers.
Again,a case of watching the volume control-clipping kills speakers.

Headroom is good thing,just don't go overboard with the volume control.
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Old 4th November 2006, 04:14 AM   #3
Bob0513 is offline Bob0513  United States
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So, If I have 20W speakers, should I just build a 15W amplifier and stay away from full volume?
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Old 4th November 2006, 07:20 AM   #4
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Originally posted by Bob0513
So, If I have 20W speakers, should I just build a 15W amplifier and stay away from full volume?
No totally true IMHO.
From your question, I undesrtand that you want to reach "max" values, either from amplifier or from drivers. With oversized speakers, you assume you will push amplifier to its maximum, which may generate distortion, able to blow your speaker more easily than extra power (especially on hi-medium and tweeters)

More power will generate more heat. On long run , it might blow your speakers. However, with amplifier power above speaker nominal limit, you will reach speaker mechanical limit before blowing speaker coil.

Obviously, if you jump from 10 to 250W amplifier on 15W speaker, what I try to explain is meaningless.

To make your own idea, instead of writing "blow speaker", try to distinguish between too much electrical power that might blow the coil on long run and too much power that might destroy spider.

My 2 cents,

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Old 5th November 2006, 10:41 AM   #5
AndrewT is offline AndrewT  Scotland
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the best control is your ears. Listen to the sound hardening and adopting that "loud" sound when you turn the volume up. These are good indicators that the signal is starting to clip.
A clipping signal when taken a little farther destroys tweeters. Take care.

Most people will listen to music at an average level of 70dbA to 80dbA. If you want real effect then add 10db to these figures.

Now the big problem
The peak signal to average signal ratio is often about +10db to +20db

Let's turn that into power ratios.
If you are listening to an average of 0.1watt in speakers that are 86db/W then you have about 76dbA at the listening position. People talking fairly loudly but not shouting are about this level when just a couple of feet apart.

The peak power could be 1W to 10W for that avearge level.

When you turn the wick up to loud then multiply all these power values by 10 i.e. 0.1W becomes 1W.
The 100W is now 106dbA peak. That is loud. But a dicso is often just below this when at average. That's when your hearing is at permanent risk.

I recommend that the amplifier is slightly more powerfull than the speaker power handling capacity. That way you, hopefully, avoid clipping, thus saving your tweeters but still have the ability to generate high peak levels. The speakers start to gently distort (without damage) and your sensible brain says "loud enough".
regards Andrew T.
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