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TQWT-mkIII
and
DTQWT-mkIII |
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TQWT/DTQWT mkIII FLAT
(upgrade kit for old cabinets with flat front
panel)
It's been six years since I had the first
production samples of the
JA8008 driver and
quite a range of speakers have been made around this high-efficiency
driver: There are two main features of the new TQWT-mkIII and DTQWT-mkIII constructions: New JA8008 HMQ driver and stepped baffle allowing a true LR2 filter to be implemented. The JA8008-HMQ driver features a high mechanical Q (low damping) and a better match to the magnificent Eminence bass driver(s), thus enhanced transient response and low-level detail. The stepped baffle allows true LR2 filter, which has become my favorite from the constructions made over the last few years. To properly implement LR2 filters we need to acoustically align the drivers, thus the stepped baffles. This is - like the mkI and mkII - a speaker I can listen to for hours and hours. Not having a high-pass filter to the midrange pays off and the waveguide and crossover makes a seamless integration of mids and highs. How the bass will respond to your room is out of my control. Based on response from the numerous builders of mkI and -II, I guess 90% are happy, 5% have too much bass and 5% too little. Too much is always due to near-corner placement and the 5% too little had expected more or their room simply suck up bass energy. For those requiring more bass, add a 12-15" bass driver driven by a plate amp. Put it against the wall to get the necessary room gain and you should be able to tune things into place. Questions are already coming in a few days after launch: Should I upgrade to mkIII. The answer is: If you're happy with mkI/mkII, don't. I try to implement new things when it makes a difference, but whether this will make you a happier person, I can't tell. So please do not ask! To my ears the LR2 filter delivers enhanced transparency and micro
detail and at the same time protects the tweeter properly compared to
1st order filters. The large domes available for these
constructions have no trouble in terms of power handling with the target
2 kHz point of crossover.
Read the story behind the JA8008 driver and TQWT construction
Read the story
behind the DTQWT and the special cabinet design Useful links (Please follow all links before e-mailing!): http://www.troelsgravesen.dk/tips.htm http://www.troelsgravesen.dk/tips.htm#CONSTRUCTION_OF_CROSSOVERS http://www.troelsgravesen.dk/crossovers.htm http://www.troelsgravesen.dk/LCR-RC.htm http://www.troelsgravesen.dk/Inverted-Polarity.htm http://www.troelsgravesen.dk/choices.htm http://www.troelsgravesen.dk/power-handling.htm
Like the TQWT and DTQWT mkII versions, these new
speakers will play any kind of music. The mkIII version is in no way a discriminative
speaker leaving out certain recordings as is often the case when
speakers excel in particular aspects of music reproduction. The "thing"
about these speakers is having a single driver handling
all of the midrange with no crossover between the bass and midrange. In
this respect the TQWT and DTQWT can play a few tricks any other of the
larger 3-4-ways systems on these pages cannot. Regardless of how smooth
a transition we can manage between bass and mid and regardless of how
good crossover components we use, the absence of a crossover between
bass and mid can be appreciated. The JA8008-HMQ driver is in fact the
same size as the 23I52 driver used in the ATS4 for upper bass and does
deliver the same punch and dynamic qualities as the 23I52. The new driver is JA8008-HMQ and the new main
speaker constructions are TQWT-mkIII and DTQWT-mkIII
as the modified crossover versions
of both were called mkII.
Former Audax TW034 version has been discontinued. |
PA drivers are often pretty rigid out of the box and I always do some "break-in" by pushing and pulling the membranes to their limit before mounting. On a fresh unit you can hear the lacquer on the spider cracking when doing so. This will do the same as at least 50 hours off burn-in. Take care and do no puncture the membrane with your fingers when doing so. In addition to this - and if you have a test CD with some 40-50 Hz sine waves - give the bass drivers a couple of hours at +/- 6-8 mm membrane excursion. All this helps loosen the suspensions and reach optimum performance quickly.
DeltaLite II 2510 specs
here. Get Deltalites here:
Europe:
USA: Crossover
TQWT mkIII
Please read below at DTQWT, same crossover except for no bass section.
Crossover
DTQWT mkIII
The bass section runs 1st order and due to the
single 8 Ohms driver we here have a 10 mH coil rather than the 18 mH
needed for two 8 Ohms drivers in series from the mkII version. The
"thing" about this speaker - and the mkI and mkII versions - is that the
middriver does not have a high-pass filter. Thus an 8" driver that can
handle the bass range as well as midrange. This has indisputable
benefits and is to be heard, even compared to my ATS-4. But every
speaker is a compromise.
Should you want to maintain higher impedance (SET
amps) and a slimmer design, you simply replace the bass crossover with
the same as for the
DTQWT mkII and buy four Eminence DeltaLite II 2510 bass drivers and
adjust the rear panel like the mkII.
CROSSOVER LAYOUT
Speaker Wiring
Cabinet
TQWT mkIII
Cabinet damping is the same as for the DTQWT front chamber and top. No
damping in rear chamber. Cabinet DTQWT
mkIII Click image to view large. If you choose to do the 2 x 10" version
for the sake of higher impedance, you can obviously leave out the rear
fillets and do the rear panel like the mkII version: Also check out construction images from the mkII version here: http://www.troelsgravesen.dk/JA8008_DTQWT_cabs.htm
DTQWT mkIII CABINET CONSTRUCTION IMAGES
Complete kit only available from Jantzen Audio, contact@jantzen-audio.com Please state where you live for full quotation incl. shipping. All kit and component prices may be subject to change and are always to be confirmed by Jantzen Audio Denmark.
Download sales presentations for four versions of TQWT The Stand-Z versions still holds Superior-Z cap for the tweeter. Sup-Z: All Superior-Z caps All technical questions to me at troels.gravesen@hotmail.com
Complete kit only available from Jantzen Audio, contact@jantzen-audio.com Please state where you live for full quotation incl. shipping. All kit and component prices may be subject to change and are always to be confirmed by Jantzen Audio Denmark. Download sales presentations for DTQWT mkIII with 1 x 12" or 2 x 10" bass drivers: All technical questions to me at troels.gravesen@hotmail.com A few comments on
MEASUREMENTS before you start interpreting all the
readings below. Here are some DTQWT mkIII screen shots from the CLIO measuring system:
Above the basic response from the new 8008-HMQ driver in DTQWT cabinet. Red is without any filter, green with 1.0 mH in series with the driver.
Above the T35 tweeter incl. waveguide mounted in DTQWT cabinet. The waveguide will boost the response in the 2-7 kHz range. Overall a response that makes crossover work easy.
Above the two most important measurements. Left: SPL from drivers driven from crossover and summed response. System sensitivity around 94 dB/2.8V. Here the midrange counts. How we tune the treble level is a matter of taste and overall system set-up. With R1011 = 0 ohm we have a fairly flat response. I prefer 1 ohm in series with the tweeter making a better balance of basic notes and overtones. Point of crossover is around 2.1 kHz.
Above the impact of mid LCR equalising circuit. Initially I left out the circuit and enjoyed a slightly vintage presentation from the elevated 500-800 Hz range and it's easy to be seduced from a response that emphasize a particular frequency band a little. We tend to think it delivers more detail. However, after some months of listening I started fine-tuning the midband and removed the ~1.5 dB bump and this is what it should be. Slightly less presence but more depth and perspective. Try it out and decide for yourself. The crossover provides you two opportunities to modify the sound to your taste: Mid equalisation and treble level.
System impedance displaying 5 ohms in most of the range and a minimum of 3.8 ohm at 38 Hz. My KT88 PP amp has no trouble running this speaker. The minor ripples around 100-300 Hz are normal for a horn-loaded system, in fact this looks very good compared to the few who dare publish such data. The 12" Eminence here goes deeper than the mkII version and I was a bit surprised to hear that as the horn basically is the same length, but apparently the 2512 bass driver does a bit more in the low end. And by the way, this 12" takes some beating to loosen up before delivering. Stretch the suspensions by pulling and pushing the membrane to its extremes and don't stick your fingers through the membrane! This simple exercise is equivalent to hours of burn-in. For the 8008-HMQ and T35 I don't find any change in sound over time.
Cabinet damping follows the same rules as for the
original version of the DTQWT. Above what comes with the kit.
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