We're done with the woofer testing. We have an impedance
and a frequency response for prototyping a crossover and we've verified
the enclosure and port sizes. Now it's time to work on the tweeter.
Next we start working with the tweeter. For the tweeter
we really just need to measure the impedance and the frequency response
- both done while in the enclosure. The enclosure front will affect
both measurements slightly (due to diffraction effects, more than
Here's the tweeter "Free Air" measurement
(done in the enclosure) and the tweeter On Axis response.
Before we start prototyping the crossover note that
the tweeter dropoff is substantial at the high end (above 15KHz).
I haven't decided for sure if I'm going to use this tweeter. It's
a large mid-tweeter made by LPG (the 38T) a 1 1/2" midrange
dome made from titanium.
The purpose of these speakers is primarily as home
theater speakers and as I get older I hear fewer high frequencies
so I'm strongly considering this because it should be able to generate
more volume at lower distortion than a standard 1" or 3/4"
tweeter. Also the crossover should be simpler because it goes farther
down in frequency. Finally, the driver is much lower in distortion
in that important midrange area (700-2000Hz) than a standard tweeter.
The next step is to prototype a crossover and listen
to the speaker to see whether that top 1/2 octave matters to me
or not. The crossover prototyping is a good exercise, either way.