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In the Forum: Playback Listening
In the Thread: How to give bats a headache.
Post Subject: It's nice to dream about full range capability... but the ultra-super tweet ain't itPosted by Gregm on: 4/28/2006
Two basic premises:
A) The concept we all operate on is: a chain of components connected between one another that pick up info from a medium, transform the info into ac and amplify that info; then, we attach speakers to the last of these components {amplifier(s)} to LISTEN to the result.
B) The most important frequency range for music is often defined as 100Hz-10kHz (I would prefer 50-10kHz), where the most fundamental musical content (+some harmonics) resides. This is well within our hearing capability -- even sine wave hearing capability.

Now, in order to reproduce these 50/100-10kHz IMPECCABLY, the system MUST be capable of much more: as Romy notes, a tweet hitting upper limit say at 40kHz can have anomalies a 1-2 octaves lower -- i.e. 20-10kHz -- and we can hear those, basically as anomalies compared to the rest of the music we're listening to. 
By the same token, a good tweet reaching 100kHz will not, in all probability, interfere annoyingly with the basic musical content...

So, it's not a matter of whether our ears catch a 15kHz sine wave alone -- it's how well we reproduce what our ears Do hear + perceive, as a whole...

Of course, all this applies IF the system as a whole is capable of undistorted reproduction -- which is a tall order...

Unfortunately adding another tweeter or two to each of the speakers won't make the result any better -- just different. It won't correct that narrow bandwidth tranny; nor that marvellous 2nd order passive crossover we have at 350Hz/ 1W that slips to third order, at 460Hz, at 10W, etc...

Finally, some practical points:
1) it is VERY difficult to ALIGN a drive unit operating over say 20kHz with the rest of the speaker. Think about it: the wavelength is less than 2cm -- if your acoustic centres are off by <1cm you;re already heavily out of phase... I love the idea of bringing 1MHz in phase!
2) While you're at it, you might check out the FR and the power response vs the rest of the spkr
3) Similarly, what about the filtering? Is it 1st order, 2nd, 65 order? Bessel, Butterworth, L/R?
4) Adding another component to the spkr changes the circuit the amplifier sees -- there we go again with the output trannies (tube) or the power capability (ss), etc, OR look for another amp...
5) For the rich, I thoroughly recommend Murata - the pro models. For a motley 3-4k each, they will play nicely from ~15kHz -~45kHz and reach their upper res ~120kHz.
6) I tried the Murata above, courtesy of friends. I won't go into the complication involved in trying to get this thing to work -more or less correctly. Suffice it to say that this was an excercise with radio techs involved. But it sounded good -- as long as you didn't touch it fm where the techs placed it.
Cheers

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