April 22 -
I began listening tests today on the mono
prototype tower. It took me a while to get the digital crossover
emulator working without problems, but now I am able to listen to the
tower array with a variety of crossovers.
I will likely not be able to recruit a pair of arms to help set up the
array in stereo until Sunday, but I do have some results to report. Just
to remind everyone, the 1500AL woofers are each mounted in a 4 cu ft
sealed box with baffle dimensions of 19" H x 21" W. Two woofer cabinets
are stacked at the bottom with an 11" x 21" subcabinet for the horn
placed above the woofers. A third woofer cabinet in placed on top. The
center of the horn is 43.5" from the ground. If people are concerned
about the horn height, I'm still looking into the horn throat at that
height. The horn is a JBL 2380A and the compression driver is a BMS4590P
with an attached network that crosses over from the midrange to the
tweeter at around 6200Hz. The center to center distance on the woofers
is 30" when the system is wired as an MTM. The two lower woofers are 19"
apart when the cabinet is wired as a TMM.
On to listening tests. Dynamic range will not be a problem with the
project May. The test amp produces 70watts into an 8ohm load and
somewhere around 100watts for the 4ohm load presented by the system. I
can't remember how much power Don has available, but I would think that
200watts per side should provide adequate headroom.
I did a quick and dirty crossover at first, using 3rd order electrical
networks with 4th order LR acoustic crossovers at 800Hz, just to make
sure the filter emulator was working. The second crossover included some
notch filters to smooth out the response. I still need to work on
smoothing the response above 12kHz.
The systems were auditioned with a variety of live and studio music from
Van Morrison, Ben Harper, Diana Krall, Miles Davis, Smashing Pumpkins,
Morcheeba, and Radiohead.
Based on initial listening, in mono remember, both the MTM and TMM
arrays sound excellent. There was very little difference in the sound
field when I was seated 7ft from the speaker. I could hear a difference
between the two speakers when I did the sit-down stand-up test.
Specifically, I could hear a recess in the response with the MTM, but I
could not say that one array sounded significantly better than the
other. When seated it was a toss up.
I will work on getting help moving the system to another room so that I
can conduct stereo listening tests this weekend with a few more sets of
ears. I have found at least 1 volunteer and I can hopefully convince his
wife to listen as well. They are both music teachers. My wife says
everything she hears sounds good, but she always objects to everything
being too loud. I bet I'm not the only one who has heard that comment.
I will post images of the response graphs directly below this post. The
images show screen captures of the crossover schematics and the response
being produced by the crossover, at 1M, on the horn axis. The component
values may be too small to view.
I think its time to start measuring the 435Be's. I have found a horn
similar enough to the H9800 to at least start listening to them. If
nobody objects I will order a pair from Parts Express, along with the
port tubes, and some 1.5" to 1" throat adapters from JBL.
First 800Hz crossover before notch filters
Second 800Hz xover with notch filters