Amplifier power ouput

[occam]

To what does the power rating of a receiver refer? This would help in my choice of Klipsch speakers.

[Ray Garrison]

If the specs say something like "100 watts per channel, all channels driven" that tpically means that at the poine just prior to clipping, into an 8 ohm resistive load, that's the power the you'd get if every channel was driving the same load.

With some receivers, if the power demands are less extreme on the surround channels, then more power would be available prior to clipping on the main channels.

Do you have a specific spec for a specific receiver in mind?

[DrWho]

the rate on an amp is typically the long term max power handling (so there is a bit of room before actual clipping occurs).

the wattage rated for a speaker is also usually the max long term power handling and it works the same way as an amp.

The average wattage being put out by the amp is a function of the sensitivity of the speaker in question...the more sensitive the speaker, the less watts you need for the same SPL (volume).

Klipsch in general have some of the most sensitive (efficient) speakers out there which means just about any amplifier is powerful enough to drive them.

[Spkrdctr]

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On 8/8/2005 11:24:50 PM DrWho wrote:

Klipsch in general have some of the most sensitive (efficient) speakers out there which means just about any amplifier is powerful enough to drive them.

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Words of wisdom for a normal (non-high end audiophile type)listener. The main issue we should all be looking at is if the rating is for all channels driven. If it doesn't say that, then it does not give you the power they are advertising. Often you get much less.... If memory serves me right, it is also the FTC rating.

[Petrol]

^^^ I have also noticed that many of the HTIB systems advertise their power rating @ 1kHz vs what had been the more standard 20 Hz to 20kHz

[Petrol]

btw, one thing I have been meaning to look into is:

What makes a reciever/amp "High Current"?

is there a 'standard' relating to power supply/capacitor design or is it just something that they can claim if the reciever in question is capable of delivering an extra 10% current? wtf?

[colterphoto1]

Good points Petrol and DrWho.

However there is something commonly overlooked by the novice. 'Turning it up all the way', as our dear writer mentions, is VERY DANGEROUS TO ANY SPEAKER. There is a point on all amps, where linear (clean) power runs out and nasty, distorted power starts being output to your speakers. This will blow any speaker up.

So while Dr Who's statement is true that because of Klipsch speakers outstanding efficiency, that they CAN be run by even small receivers, you might not want to do so.

If you tend to listen to music or movies rather loudly, having an amp with minimal wattage available would tend to run into the distorted, or clipping, type of power more often, which could destroy your speakers. Almost better to have an amp with MORE wattage than your speakers can handle, so that the extra power (headroom) is only called upon for short peaks, keeping the amp from sending distortion to your speakers, and saving them.

So there is a 'matchup' of sorts, although it is a pretty wide margin. I would venture to say that an amp or receiver with close to the stated MAXIMUM POWER RATING of the speaker would be a good place to start. You could use half that much power pretty safely or twice the power if you're careful and don't turn it up quite all the way.

With Klipsch, you'll probably be on 2 out of 10 most of the time anyway. LOL

Hope this helps, didn't mean to confuse by being wordy.

Michael

[Mark Hardy]

Power handling (at least under the old FTC-mandated rules for stereo) was measured with a sine wave, so the issue of signal peaks was irrelevant. Any amp will have some threshold of linear amplification for a sine wave input at any given frequency. The old FTC spec gave that threshold (as measured by %THD) for a given range of frequencies based on sine wave input (typically 20 Hz to 20 kHz).

High power sine waves are rough on amps and speakers, since the signal is continuous (well, technically, varying continuously); the amp/speaker doesn't get a 'break'. Due to relatively sophisticated protection circuitry, lots of modern equipment will shut down (due to heat produced) when fed a sine wave at high power. Indeed, the original FTC specification mandated a (IIRC) 1 hour preconditioning at 1/3 power to ensure to the consumer that the amp had enough 'oomph' and robustness engineered in to it not to self-destruct under such conditions.

[PrestonTom]

Regarding the question about what qualifies an amplifier as being "high current"

Good question! It is usually overlooked and folks tend to get overly concerned about how many watts (power) that an amp can nominally deliever.

Unfortunately, there is no standard way of defining "high current" (unlike the FTC-mandated/prescribed procedures for sensitivity & efficiency).

The issue is whether transient levels of power are faithfully provided to the speaker. However, the duration of the transient is not specified. So the manufacturer can define their own (and this can vary across manufacturers). The reason this is an interseting issue is that if the amp can not provide an adequate amount of current (during a loud passage or percussive sound) then clipping will result (usually odd harmonic distortion). This, of course, is bad.

For instance, the Harman Kardon amps are referred to as high current (at least as advertised by HK) since they can produce about 30 amps for a period of a few milliseconds (don't quote me on the actual numbers, but they are in the right ballpark). That is quite a bit of current, for a short time.

The issue is not of great concern unless the impedance of the speaker goes low (perhap 2 ohms at low frequencies) or it is not very efficient/sensitivity. Fortunately this is not the case with most Klipsch speakers. It could be the case for others (esp electrostatics).

In years past (and this has probably changed) some manufaturers would go to great lengths to get an amplifier to produce high transienet levels of current (amps). This could be done by beefing up the transformer and capacitors. These included amplifiers by Carver, Harman Kardon, Adcom, NAD, Denon (in the old days), Luxman, and Hafler etc.

This issue of sensitivity and actual speaker impedance is what determines whether a speaker is an easy load for an amplifier or not. There is also a complimentary issue of the amlifier's "headroom". I will let some else tackle that definition.

Good Luck,

-Tom

[occam]

Thanks.

[Spkrdctr]

High Current, now there is a big issue in audio. This is a VERY tough topic to get into. Generally, (there is that word again!)you do not run out of current. What normally happens is that your reciever/amp will supply a bunch of current and cook itself. The output transistors are not large enough to handle the high current load. Now this is not getting into high current peaks which is yet another whole issue. Generally, if your reciever does not get hot (they all get warm) to the touch, you are ok. If it gets pretty hot, then you have problems. It is a function of the amplifier design along with its cooling capacity.

This is all to say that if you want high current (and you should always want high voltage) then you must pay for it. This is the land of high dollar recievers (Sunfire and others) or good amps. There are many amps available that supply all the current you will ever need, but you will pay for it.

All in all, there is no simple easy answer. Oh well, bottom line is that if you pay for a system rated to just about double its power ratings when going from 8 ohm loads to 4 ohm. You essentially have a high current amp. Well, that is the rough, average, ballpark answer. I hope your not totally confused by what I have written!

Oh, and this doesn't even get into class D amps........or is that class T now?

[Duke Spinner]

Two comment's here ....

1) select an Amplifier that is rated at Twice the Speakers RMS wattage

2) Uuuuuhhhhh ... I fergit the Second ....

[Duke Spinner]

OOooooh ....

#2 was ...HEADROOM .....

it's getting pretty hard to find, as all the Manufacturer's are playin the Car Stereo Game ...

yea, Our Amp is 2500 Watt's ... ....

try to find a Spec that shows at least 3 dB Headroom ....