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#11677 - 06/06/03 01:45 PM Re: A/V receiver for Epic 80?
Ken.C Offline
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Registered: 05/03/03
Posts: 18044
Loc: NoVA
Wattage at the speaker end is just a measurement of how much power the speakers can take without blowing. It is not a measure of how loud the speakers can go, etc. In fact, it is an overly quoted, unimportant factoid, if you're looking at decent speakers. Basically, if the speakers can't take 100 watts, I wouldn't touch them, but other than that, the wattage rating is unimportant.
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#11678 - 06/06/03 02:02 PM Re: A/V receiver for Epic 80?
marik Offline
frequent flier

Registered: 06/05/03
Posts: 10
kcarlile,

Thanks for your input on this.
I know that wattage for speakers is how much it can handle without blowing up.
But what I was asking: If, for example, a certain receiver is 100W/channel and it's used with M80ti speakers (that actually can handle 400W/channel), does that mean that that's all they're getting, 100W each, at high volume or whatever. Or am I missing something?


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#11679 - 06/06/03 02:29 PM Re: A/V receiver for Epic 80?
Ken.C Offline
shareholder in the making

Registered: 05/03/03
Posts: 18044
Loc: NoVA
Essentially, yes. 100 is an average power at full volume (I think), so it will peak much higher than 100 Watts. Unless you're dealing with very low wattage amps (like, 10W, say), the speakers will be performing optimally.
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#11680 - 06/06/03 02:42 PM Re: A/V receiver for Epic 80?
marik Offline
frequent flier

Registered: 06/05/03
Posts: 10
kcarlile,

From what you've said I'm sensing that a receiver rated 100W/channel actually capable of providing more watts to speakers at higher volumes?
Confusing...and if it's not true, then what's the point of 400W speakers if all that they can output is what 100W receiver gave them? Then maybe makes more sense to get 200W speakers?

See what I mean?

Thanks.


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#11681 - 06/06/03 02:45 PM Re: A/V receiver for Epic 80?
spiffnme Offline
axiomite

Registered: 04/01/03
Posts: 5233
Loc: Los Angeles
Get the speaker which sounds best to your ears. FORGET about what the handling capacity is. It's NOT important.
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#11682 - 06/06/03 02:46 PM Re: A/V receiver for Epic 80?
Ken.C Offline
shareholder in the making

Registered: 05/03/03
Posts: 18044
Loc: NoVA
OK. Amplifiers are rated generally in root mean squared, which is a way of averaging power. In essence, they take the average of the output power, take the square root, and then square it. (If someone actually has an EE background, feel free to correct me). Therefore, an amp may put out 50 watts at one point, and 150 at another, which would average out to 100. Amps do not continually put out one wattage. There are peaks, which are the reason to get speakers that can handle higher wattage than the amp puts out.
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#11683 - 06/06/03 03:16 PM Re: A/V receiver for Epic 80?
marik Offline
frequent flier

Registered: 06/05/03
Posts: 10
kcarlile,

ok, I see. But is it possible for a 100W receiver to peak at anywhere close to 400W?

Thanks. I'm learning a lot here.


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#11684 - 06/06/03 03:18 PM Re: A/V receiver for Epic 80?
marik Offline
frequent flier

Registered: 06/05/03
Posts: 10
spiffnme,

But it is important to me...that's the reason I'm interested in Epic 80 system.

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#11685 - 06/06/03 07:09 PM Re: A/V receiver for Epic 80?
sushi Offline
connoisseur

Registered: 02/09/03
Posts: 1490
Loc: Dallas, TX
marik,

There are three factors with regard to how loud a speaker plays:

(1) Efficiency -- Usually measured as dB/W (in-room or anechoic), it dictates how much sound pressure the speaker produces at the distance of 1 meter in front of it when driven with 1W of power.

(2) Maximum sound level -- The absolute maximum sound pressure playable by the speaker within a given limit on distortions (for example, 110dB at 1kHz at 2% total distortions).

(3) Maximum power handling -- The maximum amount of power input the speaker can handle without breaking itself (regardless of how loud it plays at that level of power).

An important thing to remember here is that, in the vast majority of cases, (3) is irrelevant because (2) is reached way before (3). For example, the M80 is a very efficient speaker with 95dB/W of rated in-room efficiency. If you do the math under the assumption that there is no limitation (2) above, then with 100W of input, the M80 will play at 115dB; and with 400W, 121dB. But in reality, I do not think the M80 (or any ordinary non-horn-loaded speakers) will go much beyond 115dB or so, perhaps much less if you are talking about a “clean” reproduction (there is no published specs of max sound level available). This is why (3) above is irrelevant, other than it gives you some peace of mind.


kcarlile, let me pick nits.

This is a very common misconception, but in fact, there is no such a thing as “RMS (root-mean-square) power.” RMS is a measure of AC voltage or current: To calculate RMS, you square the instantaneous voltage (or current) first, time-average it over one cycle or more, then take the square root of the average. Since the power (W) has the dimension of [voltage (V) x amperage (A)] with always-positive values, you do not do the above. In order to get “average power,” you simply time-average the power.

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#11686 - 06/06/03 07:13 PM Re: A/V receiver for Epic 80?
spiffnme Offline
axiomite

Registered: 04/01/03
Posts: 5233
Loc: Los Angeles
OK...my brain is in a knot now, thanks sushi.
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