The rationale
behind this project is to reduce the number of my
ScanSpeak 18W/nnnn stock drivers. I have some 10+
pairs of SS 18W/45-85nn drivers and cleaning the
attic I found a box of pre-veneered MDF sheets
made more than a year ago, ready cut for a 13
liter vented design, actually the 18W/8542-00 +
SEAS 27TFFC, the classic compact studio monitor
from a producer than shall remain nameless here.
The 18W/8542-00/27TFFC will be the final
construction for sale, including the mahogany
veneered cabinets seen here.
When the 18W/85nn drivers
came about some 15 years ago, everybody was
impressed from the design, the "ugly"
looking carbon-paperpulp membranes and the huge
magnets. The rather slim chassis allows a 145
cm^membrane area from an overall 177 mm diameter,
quite impressive. All 18W/85nn have copper plated
polepiece, symmetric drive, and a vented centre
polepiece. The huge magnets and low Qt suggests
drivers suitable for 10-15 liter cabs and a few
small monitor designs were launched immediately
after the release of the drivers. Since then
numerous designs have been produced and often we
see the classic 18W/8545-00 driver used in up to
24 liter vented or transmission line
constructions despite really suited for smaller
cabs. My Amish speakers are examples of this.
The 18W/8545-00 has an aluminium voice coil
former, where the 18W/8545-K00 has a kapton voice
coil former.
Why build small speakers when we can have bigger
sound for the same money from a bigger cabinet?
Well, the answer is simple: Because sometimes
they must to be small due to how they
will fit in with a given idea about how our
living rooms are going to look. WAF is high from
small speakers. Even if a slim floorstander
doesn't not take more floor space compared to a
mini on a stand, the WAF is higher for the
latter. Not much we can do about it. Thus this
range of Compact Studio Monitors.
"Studio" because it started with the
8542 driver for studio use, by request from a
Norwegian studio ingeneer. The result was the 8542/9500/9700 design, released last
year. Not exactly a studio monitor suitable for
placing on the mixing console. Sorry it took so
long.
How small is small? Well, the W15CY001/OW1 is small, the Ellam a little bigger (10
litres) and delivers a bass performance leaving
the W15 behind. When we add 2-3 litres we may
have room for a 6-6½" driver, a significant
increase in membrane area and we can get a decent
bass response down to 50 Hz. Comparing a
18W/8545-00 to a 15W/8530-G00 in 13 litres and 10
litre respectively, we get this picture:

The 15W/8530K00 may produce a slightly
more extended bass response, but at the expence
of ~2 dB efficiency. Listening to the bass
response from W15W/10 litres and the 18W/13
litres - side by side - leaves no doubt which
driver is most comfortable in this area. I'm not
talking about midrange quality here, only bass.
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