Dynamic Headroom

Kijanki...So it seems that the FTC power spec IS supposed to cover thermal considerations. That might be very reasonable for pro amps which play highly compressed and peak limited music at maximum volume. I play music on my system very loudly (but not compressed music) and my digital amps get barely warm. My comments above are aimed at home audio amps.

Eldartford - I don't listen very loud, perhaps 50% of max what makes already 1/10 of the power and because music does not contain peaks alone but most likely less than 50% volume most of the time it is another 1/10 of power. Music has also gaps - it is not continuous sinewave making it even less. I would assume that average power delivered to speakers is less than 1% of the max rms (around 1.5W).

Output stage of my amp is supplied from regulated 47V making 370W peak at 6 ohm. It's peak and not rms so overall headroom is not very big but it sounds big. It might be because of immediacy of response but also because of my moderate listening levels.

Take a 100wpc amplifier that doubles all the way to .5ohms; That is Dynamic Headroom, at its very Best.
Or another 100wpc amplifier, that produces 140wpc.@4ohms, and maybe 150wpc. @2ohms very briefly. The second amp. does NOT have ANY Dynamic Headroom.

While I agree with the general sense of your post, this statement reflects an incorrect definition of "dynamic headroom."

Re-stating what was said earlier in the thread, in slightly different terms, "dynamic headroom" refers to the ratio, usually expressed in db, of an amplifier's short-term maximum power capability to its rated continuous (long-term) maximum power capability.

An amplifier that can double down to 0.5 ohms is designed to be able to supply very large amounts of current. In many cases that kind of amplifier will have very little if any dynamic headroom based on the proper definition, because its maximum output power will typically be limited by the voltage range that its output can encompass.

At the other extreme, quoting Kijanki's accurate restatement of my earlier posts, "within given power supply size (wattage) you could design for higher output voltage (getting better headroom) sacrificing output current and making it weaker for average power demand."

Since the dynamic headroom of an amplifier is based on the proportion of short-term maximum power to long-term maximum power, it will be improved if the design (or the specmanship!) does one of the following:

1)Increases the short-term maximum power, without significantly affecting the long-term maximum power. This basically means increasing the voltage range that the output can swing without clipping.

2)Decreases the long-term maximum power without significantly affecting the short-term maximum power. This is why I mentioned that amplifiers with "weak" power supplies and/or marginal heat dissipation provisions can often have good dynamic headroom numbers.

3)Obviously, some combination of (1) and (2).

Mlsstl & Kijanki -- thank you for your excellent posts.

Regards,
-- Al

Correct me if I'm wrong. In my case dynamic / headroom and such doesn't matter.
If I use 30x2RMS, my ICE are 500x2@4, why would I care if they had 3db or 0.1db headroom? 30x2 is pretty loud.

Magfan -- No correction needed. You don't need any dynamic headroom provided that brief musical peaks do not approach the 500 watts. Keep in mind, though, that 500 watts is only about 12db louder than 30 watts.

Best regards,
-- Al