One of the reasons for
this page is repeated requests for other combination of
the still popular SS drivers, thus four crossovers that
will balance the response from 18W/8545-K00, 18W/8545-00,
D2905/9500 and D2905/9700 in any combination. The two
bass drivers were more alike than I had expected, and
almost the same high-pass section could be used for both
drivers. The 9500 and 9700 tweeters are quite different
and it takes different measures to get it right.
Initial modelling was easy, but final fine-tuning more
difficult than expected. The target was to get proper
phase-tracking at tweeter height at 1 m distance and the
combination of 2nd and 4th order slopes were necessary to
get it right.
Both bass drivers provide a basic system sensitivity of
85-86 dB/2.8V.
Another reason to launch
parallel filters is that a number of people have had
trouble getting the series filters right. Some don't
understand what a series filter is, and some may have had
trouble due to variations in driver performance. Thus the
18W/8545-00 + 9700 series filter has been deleted from
the first Amish page.
I have 8545 drivers that perform quite differently
depending on how old they are and apparently it's tough
for SS to maintain the same performance from the
air-dried carbon-fiber/paper-pulp cones.
Generally I find parallel filters less sensitive to
variations in driver performance.
 
Left: Frequency response
of 18W/8545-00 and 9500 drivers without crossover
on TJL front baffle.
Right: same bass driver and 9700 tweeter.
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Blue = 18W/8545-00
Red = 18W/8545-K00
# 1
18W/8545-00 + D2905/9500
 
#2
18W/8545-00 + D2905/9700
 
#3
18W/8545-K00 + D2905/9500
 
#4
18W/8545-K00 + D2905/9700
 
The 9700 has a small saddle at 2.5-3 kHz due to a
combination of intrinsic response and the chosen
placement on front panel.
I tried adding a small 20 mm fillet to the top of the TJL
cab and got the green response. Now it's got a smooth
roll-off, but summed response
display a minor peak between 3 and 4 kHz (yellow graph) .
Not an easy thing to place a 1" dome on a small
baffle! Cabinet edge diffraction plays a major role.
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