Midrange and HF power requiremments
Quote: - (My main speakers have little 6" woofers and 1" tweeters. They don't produce much bass. I have the sub crossover way, way above the normal 80 hz because the little speakers need the bass support. I don't use much amplifier power at all to drive them. The sub takes most of the power beating.)
I doubt that is always true. We are getting a little away from the members question, but we are getting into an important and I believe misunderstood area, which I have commented upon a number of times previously.
I'm going to make some observations and generalizations which may well get me into trouble yet again!
My first observation is that members, and I think owners of sound equipment in general, have a very difficult time really internalizing and understanding the significance of the logarithmic db scale. People tend to visualize all physical phenomina in a linear and not a log fashion. If relationships are log it leads people to erroneous assumptions.
For example I live in central Minnesota where it has been very, and unseasonably cold for early December. The local worthies who gather at the coffee clutch at the little Fort Benedict general store, post office, gas station and trading post have a hard time understanding why their home heating fuel consumption is so much higher than last year. Now Newton's law of cooling is a log curve. So lets keep a house at 68 F with en outside temp. of 32 F. That is a gradient of 36 F. Now lets take an outside air temp. of -4 F, the gradient is now 72 F. Assuming it is still air and the house temp. does not change, the fuel consumption will not double but increase ten fold! Now that is hard for the coffee clutchers to really internalize. The same with power and sound pressure levels, or perceived loudness.
Now back to the energy spectra of acoustic sounds. The energy spectra displays that I look at, show considerable acoustic energy from 250 to 2.5 KHz. The human voice of both sexes has great power in that range. The voices of operatic singers are particularly powerful. Strings, brass and woodwind have enormous energy in that range. The energy of the pipe organ extends with significant power out to 5KHz.
Annunaki posted a good article on the power requirements of subs, and thermal dynamic range compression in particular.
Now I would assert that this applies with even more significance to midrange drivers and even tweeters. Now tweeters usually crossover at 2.5 to 4 KHz. However filters are usually of a low order and so a tweeter is producing a good deal of it output below crossover. That can lead to the tweeter producing power, close, or even at or below resonance. That makes things sound rough. I have a rule in my designs to keep tweeters 24db or more down at their resonant frequency.
My next assertion is that many speakers, and probably the majority, have inadequate midrange power handling. I have always allowed for significant power handling in the midrange. Take a Dynaudio M75 mid range. That has a huge 2.5 inch voice coil with a vented gap. You really need to look at the motor systems of midrange and mid/bass drivers very carefully before selecting them. The same is true of tweeters with crossovers below 4 KHz and low order filters.
Now to total power. The dynamic range of music is huge, especially in the classical genre. People's audio systems are running out of gas much more often than they think. Having really powerful amps really does make a difference to the realism of reproduced sound, as long as the speakers can handle it without distortion and excessive thermal compression.
I know people are often aghast when I tell them the total amp power of my system is 1.7 KW. However that only produces twice the spl of a 170 watt system!
I know this is tough to get your arms round, but when it comes to power and spl think log.
