Originally Posted by Alimentall
I understand, but you can't take ribbons which don't behave pistonically, and translate that to all types of drivers. Pistonic drivers have precious little 'sound' blend with other pistonic drivers when used within their best operating range.
It doesn't matter whether the drivers are "pistonic" - besides that is only an approximation
anyway - true drivers are really not pistonic.
The relevant physics here is "antenna' theory - and loudspeaker drivers are "antennas".
Suppose we have a speaker like the Xd satellite - with a 5" cone and a 1" dome - or
whatever the Xd has. Suppose "fc" is the crossover frequency and the crossover is
very steep - so the range in which the two drivers overlap is very narrow, if not zero.
A frequencies just below fc; the 5" cone is doing the radiating - and the radiation pattern
is that of whatever wavelength corresponds to frequency fc being radiated with a 5"
antenna. The size of the antenna vis-a-vis the size of the wavelength determines the
Now we increase the frequency slightly to get us above fc into the tweeter passband.
The frequency is not only slightly above fc - so the frequency hasn't changed much -
but it is enough to put us into the tweeter's passband.
Now we have a 1" antenna radiating a wavelenght that is only marginally different from
the one the woofer was radiating. However, the size of the antenna has changed
suddenly from 5" to 1"; and hence the radiation pattern suddenly became more
isotropic with a slight increase in frequency.
Real musical instruments don't do that - they don't change their radiation pattern in the
frequency span of just a few Hertz. It would have been better to blend the output of
the drivers so that the transition from the 5" radiation pattern to the more isotropic
pattern of the 1" driver took place over a greater span of frequencies so that it was
A sharp crossover between two different sized drivers is going to give a sharp transition
in the radiation pattern as a function of frequency at the crossover. Real instruments
don't have sharp transitions in radiation pattern. The artificiality of this transition calls
attention to the fact that the reproduction is an artificial one.
Again - Mother Nature doesn't have these sharp transitions in radiation patterns - why
would one try to emulate Nature with a characteristic that Nature doesn't have?