SPL/2.8V, 1 meter distance, 38 x 100 cm baffle. Final
system sensitivity expected to be 90 dB/1 meter/2.8
Right: Impedance free air (red) and 33.4 litre closed
test cab (blue).
This driver is dedicated bass driver and
unlikely to play anything above 500 Hz, but for the sake
of curiosity, let's take a look at the 2.5 kHz peak.
measurements were done with mic some 10 cm in front of
cone. Input signal equivalent to ~85 dB/1 meter.
Left: Blue = 2nd harm. Green = 3rd harm. Basically <40
dB over the entire range.
Right: 1/6 octave smoothing and 3rd harm. (yellow) and
4th harm. (purple) shown.
CSD @ 40 dB scaling. Right: Same @ 20 dB scaling.
Modelling point of crossover around 800 Hz? No problem,
even with a simple crossover.
TS data, CLIO measurements, added volume method. Drivers
not broken in. Right: AudioTechnology TS data.
Having played the 10C77s for a month I measured this. Qt
a bit down, Vas a bit up.
I expect the drivers to only change a little after this.
Variation is remarkably low.
Comparing 10" bass drivers
AudioTechnology 10C77-25-10-KAP. Middle: ScanSpeak
26W/8861T00. Right: SEAS W26FX002.
experience from the Jensen
1071, SEAS Cyclop,
Jenzen NEXT, PRELUDE
and Jenzen Accu
the 10C77 is a clear winner in terms of overall performance. I rate the
SEAS a tiny bit higher than the ScanSpeak despite ScanSpeak's higher
mechanical Q but time will tell when the 26W/8861T00 is tried in the
Jenzen transmission line cabinets.
Box simulation 10C77-25-10-KAP
First of all
I do not intend to make a vented system for this
bass driver, rather a transmission line cabinet.
But before doing so, I want to investigate the
vented option to get a better feel of the driver
and its performance from a typical bass reflex
Getting any 10"
driver in hand we usually start thinking
of some 40-60 liter cabs. Most 10" drivers
will produce decent bass from this size cabinet
unless TS data are severely "out of
range", i.e. having extremely low or high
Qt. Ideally only drivers with a Qt close to 0.35
will perform optimally in vented enclosures. As
few drivers are even close to this requirement,
we tend to use too large cabinets for low-Qt
drivers and too small cabinets for high-Qt
A textbook QB3 tuning for the 10C77 driver will
dictate some 20-22 liters and obviously this is
too small. It would seriously compromise low-end
extension, thus 45-55 liter volume has been tried
in LspCAD to predict performance and this is
really where we're heading if a vented box was to
Below examples of 45 and 55 liter cabs from
calculated from AT data (left row) and my data
(right row) despite drivers not broken in. In
fact, the lack of break-in does very little to
the performance as can be seen.
Based on experience
I like a bass driver for vented boxes with a Qt
around 0.25-0.3 in a volume 1.5-2 x calculated
optimum volume - and tuned a little lower than
optimal to produce a slightly shelved response
towards lower frequences. This will make a decent
flat response taking into account the inevitable
room-gain. I assume some 80-100 cm to the rear
wall (behind driver; some call this the front
wall... whatever), 50-70 cm distance to floor and
1.5-2 meters to side walls. Placing a bass driver
in a corner is doomed to fail except for
dedicated subwoofers taking advantage of some 6-8
- click images to view large -
Left: AT data and 45 liter, 30 Hz vent
tuning. Right. My data, 45 liter, 30 Hz vent tuning.
Left: AT data and 55 liter, 30 Hz vent
tuning. Right. My data, 55 liter, 30 Hz vent tuning.
Left: My data and 50 liter, 30 Hz vent
tuning. Right. My data, 50 liter, 30 Hz vent tuning,
Vent diameter and length has been erased as LspCAD does
not calculate this correctly.
For 50L/30Hz, use 80 mm (D) x 200 mm (L) vent or 100 mm x
I suggest a decent flared 100 mm diameter vent to reduce
vent noise. This bass driver can move some air!
can be seen from above illustrations,
even 50 liters may produce decent bass down to 30
Hz when placed e.g. 55 cm above floor, 110 cm to
rear wall and 180 cm to side wall. This room-gain
calculation is a simplified model and doesn't
take into account a lot of things, but based on
experience it does give a decent hint of where
a pair of 65 liter cabs at hand I
quickly set up the bass drivers and placed the AT-SWs on top.
An electronic crossover, 24 dB-LR, made it easy
to find a proper point of crossover between the
two units. Playing a clean fender bass from a
test CD is great tool to determine the best
crossover frequency and 130-150 Hz made an
overall coherent sound although the AT-SWs may do
even better from being e.g. 15-20 cm closer to
the bass driver - at least when listening at very
short distance as my workshop only allows.
While playing the Fender
bass track and adjusting the point of
crossover from below 100 Hz to above 200 Hz I
placed my finger tips on the 18H52 membrane of
the AT-SW and I'm always amazed how much energy
comes from the 100-200 Hz range. This is an
indeed important frequency range and having a
driver not capable of moving sufficient air
leaves the overall sound thin and anaemic. 135
cm^2 like the 18H52 here does well down to
140-150 Hz, where an e.g. 6A77 with its 175 cm^2
does well to around 100 Hz. Using a 15H52 (95
cm^2) for mid we may have to increase point of
crossover up to 300 Hz depending on front panel
dimensions. The wider the panel, the deeper we
The result from these
experiments left no doubt in my mind
that a system like this is a go! These bass
drivers are exceptionally good. Clean, punchy and
dry bass is the result from these 65 liter cabs
initially fitted with 2 Variovents. Now,
Variovents may be good for drivers having a
higher Qt compared to these 10C77s, thus new rear
panels were made and fitted with two 68 mm ports
of 22 cm length, providing Fb ~28 Hz.Thanks to
the generous motor system, these 10C77s' are
control-freaks. I'm sure the majority of speakers
that will be made from these driver will be
Control is indeed what
comes to mind when listening to these
10C77s. Adding two 68 x 220 mm vents to the rear
brought things into perspective. Variovents with
these drivers is a miss-fit. I don't think I've
ever heard better bass from a vented system.
So, if you can't wait, the
current recipe is this: The cabs seen
above are a bit too high and the distance between
bass and mid should be reduced to ~15-18 cm.
Thus, bass cabs should be 36 x 65 x 36 (W x H x
D). Made from 22 mm MDF, this will make a net
volume of 62.5 liter. Allow generous bracing to
swallow some 2-3 liter to make a final net volume
of 60 liter. Place 10C77 with 10 cm from frame to
top edge. Add two 68 x 200 mm vents to make Fb =
32-33 Hz. Place AT-SW on top and use an
electronic 24 dB-LR at 140 Hz.
Result: It's a knock-out. Deep and dry bass, a
midrange to die for and shimmering highs from the
I can only imagine what it will sound like in
rock-solid cabs, better power amps, better
cables, better room, etc. Time will tell.
Next: The PRELUDE
A classic 3-way from AT 10C77 bass
+ new AT 15H52-SDKAM middriver + ScanSpeak
January 2010: Numerous crossovers
are being tested for this PRELUDE speaker
featuring temporary middrivers while waiting for
some new 15H52 drivers. 1st order filters for mid
and LR2 for tweeter and bass deliver an
astonishing presence and transparency with my new
JungSon class A amp. "Problem" with
this speaker is how loud it goes with very low
distortion. All of a sudden I find myself
listening at too high levels for the room....and
for my ears.
Comparing the 10C77 bass driver to the SEAS
W26FX002 - at low levels! - leaves no doubt that
all the talk on the Audio Technology website
about low-level authority isn't just - - talk.
Indeed the rigid cone and high mechanical Q does
the trick, which we usually have to go to PA
drivers to find, only this driver comes with a
set of TS data allowing modest cabinet size - and
still maintains 90 dB/2.8V system sensitivity.
2010: Prelude launched. Click heading or image
A few in-room (workshop)
measurements on current set-up (10C77 + AT-SW)
Left: What happens when point of crossover is set to
130-150-170 Hz. Disregard response above 1kHz. These are
Middle: Left speaker in-room @ 2 meter, 100 ms time
window and 1/6 octave smooting. Workshop has problems in
upper bass, making sound a bit forward.
Right: Same thing, here left and right speaker. Right
speaker has a dip (room derived) at 100 Hz and a boom at
30 Hz; sounds nice though!
Left: Left speaker with same and opposite polarity of
bass and mid. Fair integration between bass and mid
despite measuring conditions.
Middle: Nearfield measurements of port, bass and mid
showing point of crossover at 130 Hz and port tuning at
Right: Same thing, only 20 dB scaling to show no midrange
rubbish coming from port(s).
Overall: This speaker goes deep!