TQWT/DTQWT mkIII FLAT
Copyright 2022 © Troels Gravesen
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I've named this page TQWT/DTQWT-mkIII-FLAT, but could
also call it TQWT/DTQWT-mkII UP-GRADE as it describes
the use of the new JA8008-HMQ driver in the cabinet of TQWT/DTQWT-mkII
or any previous version.
Some people would like to use the new JA8008-HMQ driver in their
previous flat front panel cabinet versions without having to change the
front panel design. When the new JA8008-HMQ driver was launched I
reckoned there would be a limited demand for this, but there have been a
few requests, as kids and cats can be rough on the foam surround of the
old JA8008 driver, so here it is.
Should you loathe the stepped front panel of TQWT/DTQWT mkIII, this is
obviously also a solution for a new construction with a flat front
panel. Just add the bass section crossover and you're flying.
The stepped front panel was introduced to allow better timing of the
drivers and implementation of a true LR2 crossover, something that pays
off in terms of sonics.
Pulling the waveguided dome some 20-22 mm forward calls for a higher
order crossover like used in previous versions. However, the low point
of crossover of the mkIII, 2 kHz, is maintained and the added
presence of upper-mid/lower-treble of the stepped mkIII is fully intact.
Draft solutions and the flat front panel
The bad news is that you not only need the new JA8008-HMQ drivers, but
also a new crossover as it is different from previous versions due to
the change of point of crossover and slopes.
The new JA8008-HMQ appear to have an increase in chassis diameter of
some 0.2-0.3 mm, so in case you have a very tight fit you may need a
little extra routing:
http://www.troelsgravesen.dk/tips.htm
Read about new JA8008-HMQ driver
To provide proper phase integration and flat frequency response the
filter above will produce a close to LR4, 4th order, roll-off of both
drivers.
SEAS T35 requires R1 = 2R2 for proper balance. A number of resistors
follow the kit to tune tweeter level to your taste, but don't be seduced
by high tweeter levels! Causes ear fatigue over time. R1 = 1.0 Ohm is
really only for tizzy treble addicts. All for the customer!
Above the fine-tuning of JA8008-HMQ driver.
Red = response of driver with no crossover.
Green is without the LCR circuit. Orange final response from crossover
seen above. FLAT midrange!
Final response.
System response (red) and response of driver driven from crossover.
Blue = SEAS T35 tweeter response and orange = system response with T35
tweeter compared to TW034 response (red).
Audax TW034 version discontinued.
If you have the mkII version crossover, you have 2 x 5.6 uF and 2 x 6.8 uF. These can be re-used by adding 2.7uF and 1.5 uF respectively to make 8.3 uF, which is perfectly OK - and you save money. Ask Jantzen if interested to replace all four 8.2 uF caps with 2 x 1.5 uF and 2 x 2.7 uF. These are the only components that can be re-used.
All questions regarding purchase of
kit, please mail Jantzen Audio at
contact@jantzen-audio.com
All technical questions to
troels.gravesen@hotmail.com
CROSSOVER-LAYOUT
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Bass section for 2 x 10"
