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How to properly judge wattage.

So, in summery, we must all buy oscilloscopes to monitor signal integrity, and hope that we don't blow up our speakers at optimal listening volume? :)
 
Well said. I reread the thread title and re-read the key word: properly. Yes, you'll need an oscilliscope and a few other bits to properly figure out your amps true wattage.
 
VolvoHeretic said:
So, in summery, we must all buy oscilloscopes to monitor signal integrity, and hope that we don't blow up our speakers at optimal listening volume? :)
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Interesting summary. Not sure how you came to that conclusion. In any case, I believe that having a basic understanding of the relationship between power, loudness, sensitivity and clipping is fundamental for making good decisions about one's set-up...and the OP seemed to be trying to get a handle on whether or not his amp would be a good match to his speakers.
 
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fred soop said:
IHF power is bogus. A typical musical peak will last more than a few cycles of 120 Hz power and it only takes a few cycles to pull the filter capacitors down to a long term steady state voltage for the duration of the musical peak.
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Like I said before, it's all the truth, just stated in different ways.


The service manual for my Yamaha amps lists FTC, IEC, and DIN power. Some of the numbers are quite different...but it's still the same amp and sounds/performs the same no matter which numbers you read from the SM. It's just different views/perspectives of the same thing.

The key is, as you well know, comparing apples to apples. DIN doesn't directly compare to IEC doesn't directly compare to FTC, etc. etc.
 
I have 2 Realistic audio power meters. They can be found on E-bay for the price of cheap cables. With the proper use of these meters I can keep any amp from 5 - 200 wpc safely out of clipping driving 98% of the speakers out there to full power. If your using a good amp and don't want the signal polluted, You can use the meters to determine the position of the volume control with a loud CD or LP that approaches clipping and then remove them.

The few ms of clipping that may be missed by the meters is not a problem for speakers if you are using their recommended power input. When driving 4 ohm speakers, Limit the amp to 1/2 (-3 db) power to insure it never runs out of current, or clips

As far as power ratings go, The FTC ratings are a reasonable basis for matching speakers. In the ops case it looks likes 27 wpc. Keep in mind these power ratings are typically for an 8 ohm load. This does not mean the amp/receiver is stable into a 4 ohm load, that info will likely be printed on the back of the receiver.
 
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Separate power meters really won't do it too accurately (substitute for clipping indicators) because they are not calibrated to the specific amp, nor are likely to respond as quickly.

Most amps actually make more power at 4 ohms so running them at half power seems like an underutilization of capacity. Granted, not like a dBw or two is going to make a difference in perceived volume but still...

If you don't have clipping indicators just use your ears. If it sounds bad it is bad. But, then, I guess I've heard people cranking stuff that sounded bad (in terms of distortion, beyond system capability) but they apparently thought sounded just fine.

EVERY amp should have clipping indicators included.
 
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