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Probably a Dumb Question


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Please pardon the novice. If a amp is rates at a 105 Watts per channel what must I look at to make sure I have the correct speaker rated for that wattage ? For example, I see speakers that are rated for 50 watts continuous, 200 watts max. Will those work? Is there a rule of thumb I can follow ?

Paul C.

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OK, here's the rule....There is no rule!

Lots of people have amp rated wit more output than the speakers can handle--they don't turn them up all the way!

When a company says their speaker is rated @ 50 watts with a 200 watt max, they mean it can handle 50 watts continuously. Now in a movie, when like a bomb goes off or something, the amp deilvers much more power to the speaker to drive it to get that sound out with impact. This is a short burst and speakers can handle short bursts just fine. The 200 watt max is what this is referring to.

What is more important is the sensitivity of the speaker. This should be marked on the speaker (i.e. 94 db @ 1 watt/meter). This is a measurement of how loud the speaker will play per measure of power imput. This is where Klipsch rules! Klipsch speakers are very effecient--like above. It means that the speaker will produce 94 db's with 1 watt of power imput @ 1 meter (distance in front of the speaker).

So you can see that your speakers can play very loud without a lot of power if they are very effecient! Now it doesn't double with the imput, it's kinda a negative exponential thing (log 10 something or another--a little help here guy's). My receiver is rated @ 75 watts/channel--I rarely turn it up past 1/4 unless the wife isn't home & then rarly more than 1/2 way. I have KSF 8.5's rated @ 94 db's. They get too loud.

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As another fine fellow on the bbs stated, we should first give the disclaimer that there are no dumb questions.

The question IS a good one. It requires an appreciation that we are sometimes talking about the compatibility of components, but not always. The numbers thrown about in technology don't say, themselves, whether or not there IS a compatiblity issue.

E.g. I have a .45 Colt automatic pistol. Do I need .45 ACP (automatic Colt pistol) cartridges? Obviously, yes.

On the other hand, if you say, I have a car capable of going 150 mph, do I need a road rated for safe driving 150 mph to use it? Obviously no; unless you really want to go at 150 mph.

The examples are extreme. However, they are presented by me to show that the writers of specifications do not always point out that a given spec is, or is not, an issue of compatabililty.

Naturally, newcomers have legitimate caution. This is more a fault of the spec writer, than the consumer.

Turning to the specific. The power rating of the amp and speaker you most likely have is/are more like the second example than the first. This analogy is a bit lame, but bear with me.

In order to get typical consumer speakers driven to a "very loud" level, 105 watts available power is going to be more than enough. Technically, there are exceptions and extremes, but I doubt you're in that area.

When the amp is putting out 1 watt, the sound is going to be very loud in a living room. You will not be threatening the speaker with 1 watt.

In short, you have an amp with a good amount of power for most all speakers. Nothing to worry about. You'll almost never be trying to put 105 watts into the speakers.

It is not quite a matter that there are no rules. Rather, the rules are not well explained. Also, your amp and your speakers are most probably well within typical bounds. So you don't have to worry about the "rules" at the extreme.

If you have any further questions, I'd be happy to explain.



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Just remember, it most likely won't be the power from the amp that'll blow drivers but the amounts of distortion (clipping) coming from the amp itself.


Colt IPSC converted Series '70

Sig-Sauer P228 - yes a thirteen round

Browning Hi Power (Belgium)

Dan Wesson Pistol Pak .357VH

Ruger SP101

Ruger MK-678GC

North American Arms NAA-22LR

Ruger 10/22RB

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Remington 700ADL 22-250

Remington 11-87 Premier Heavy bbl.

Crosman 760 - Varoius Commemoratives.......

....oooops! wrong list.

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From a more technical speaker web site:

>When an amplifier receives an input signal capable of driving it beyond its power rating, the result is clipping. This means that the negative and positive peaks of the amplifier's output signal are "clipped" off. The amplifier may also clip in an asymmetrical fashion, meaning that the positive side of the signal is clipped more than the negative (or vice versa). When subjected to an asymmetrical clipped waveform, one end of the loudspeaker's voice coil is "on average" spending more time outside of the gap (corresponding to the direction that is clipped) than the other. The end of the coil that is spending more time outside of the gap has poor heat transfer to the magnet structure. As a result, it overheats and burns. <

I had read that you should have an amplifier capable of at least 100 Watts of output just to handle the dynamic range between the LFs and HFs of the (new) medium, CDs, to keep your amplifier from clipping.

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Needing 100 watts is just a rule of thumb. If you had inefficient B&W speakers, that might be 1000 watts, instead of 100. For K-horns at 104 dB @ one watt, 10 is likely enough. 104 dB is really pretty loud. You won't talk over it easily.


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