DTQWT-212 mkIII
Copyright 2015 © Troels Gravesen

DTQWT featuring two 12" EMINENCE bass drivers.

The new version is called "212" not to confuse it with the DTQWT-mkIII that use one 12" bass driver.

1. The DTQWT-212 main driver, JA8008, is now replaced by new JA8008-HMQ driver.
2. Apply DTQWT mkIII stepped front panel design to cabinet seen below and use
3. TQWT-mkIII crossover combined with bass crossover seen below.

Go to on this page: CROSSOVER    CABINETS    THE KIT   CROSSOVER LAYOUT

 


New JA8008-HMQ drivers

 
Audax TW034 or T35C002 tweeter and waveguide.
Read instruction from DTQWT mkIII for how to mount waveguide.

Before starting a DTQWT-212 project, please read entire DTQWT file as everything is the same except for size of bass drivers and cabinet dimensions. Here you'll learn about the rationale for the double-tapered quarterwave horns. Also read TQWT to learn about the choice of main drivers, JA8008 and TW034, used in the constructions.

A few people have misinterpreted the DTQWT-212 due to the two 12" bass drivers and think it can load 100+ square metre rooms and cope with the same amount of power we would only feed 15" PA drivers with huge 4" voice coils. The DTQWT-12 is still a 2-way from an 8" driver and a 1½" dome, only added extra bass drivers.

Like the TQWT and DTQWT-10" the DTQWT-212 is developed for low-wattage valve amps or high-quality class-A amps of modest power and not for 200-400 watt solid state amps. DO NOT be seduced by the two 12" bass drivers thinking this can load a 300 cubic meter living space or a larger surround theater. The 8008 front driver does not have a high-pass filter which has indisputable advantages but also limits power handling as it received the full bass load. If you want a speaker that can handle larger listening space volumes, take a look at the OBL-11. This speaker can make your ears bleed.

Ever since I made the TQWT I had this speaker in mind, the ultimate DTQWT with two 12" bass drivers loading a ~3 meter horn, thus the 8" JA8008 extended range driver supplemented by Audax TW034 tweeter loading a modest waveguide.
Ultimate DTQWT? Well, we can always go to the extreme and build a two-and-a-half meter high speaker with two-three 15" bass drivers - or build a new house with in-built 10 meter bass horns, but I think this will do for some time. I'm sure only a few will apply for a total of 600 liters cabinets in their living room as these will require.
The cabinet has grown to almost 152 cm height and 33 x 60 cm (WxD), so these are quite big speakers with brutto volumes of 297 litres and basically we're dealing with an expansion of the DTQWT bass horn proportional to the membrane area of the bass drivers.

Bass drivers.
For the DTQWT-12: Eminence Deltalite II 2512, available from e.g. Thoman/Germany. Download data sheet here.
I have been more than satisfied with the Eminence Deltalite bass drivers in the DTQWT-mkII (10") and OB-9 + OBL-11 (15") , so it was obvious to take a look at the Deltalite II 2512 for the DTQWT-12.
Over the years I've had many questions on alternative bass drivers and I can't tell because I've never tried them. Finding PA bass drivers - because we need a healthy 95 dB sensitivity - with a suitable low Fs is not easy and usually PA drivers feature significant higher Fs than claimed in specs. This Eminence driver is close to its promised 37 Hz, but 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 2512  bass drivers. Download data sheet here.
These Eminence bass drivers have an excellent performance/cost ratio.

 

DTQWT-212 mkIII Crossover
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CROSSOVER LAYOUT


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HOW, WHERE AND HOW MUCH?
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Download kit sale presentations here, pdf file with all options

All kit and component prices may be subject to change and are always to be confirmed by Jantzen Audio Denmark.

Mail your address and ask for shipping cost at: contact@jantzen-audio.com

Kit contains all drivers (excl. bass drivers), waveguides, crossover components incl. comp. for bass drivers.
More options available with regard to choice of coils and caps. Please specify.

Bass drivers: Eminence Deltalite II 2512, available from e.g. Thoman/Germany

All technical questions at: troels.gravesen@hotmail.com

 

 

DTQWT-12 Cabinet
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Cabinets, how to get started:
For the DTQWT-12 mkIII: Add DTQWT-mkIII stepped front panel design by extending tweeter plane panel.
1. Cut four sheets of 560 x 1480 mm for sides. For sides, rear and top panels some 22-27 mm panels can be used. Keep outer dimensions and dimensions A, B, C and D the same and allow some variation in dimension E. Marked with read on drawing above. For internal panels, 19-22 mm panels will do.
2. Cut two sheets 560 x 330 mm for top panels. I prefer to cut 45 deg to the top to make nice joints.
3. Make rebates in side panels for rear panel. Cut to a depth equal to the thickness of the rear panel, e.g. 27 mm if made from 27 mm Baltic birch.

4. Tape side panels and top panels together and determine the width of the rear panel exactly and cut accordingly. Now you can tape on rear panel as well.
5. Make a drawing of the interior panels on one of the side panels and measure their length. Measure the exact width of the interior panels and cut accordingly.
6. Assemble one side panel, top panel, rear panel and interior panel with tape and determine the position of the bracings as shown on drawing. Exact position is not critical, just as close to the drawing as possible.
7. Determine the position of the 8008 driver and make an Ø 150 mm hole for the magnet. Make and e.g. 170 mm diameter disc to cover the hole.
8. Now you should be able to assemble the whole speaker sans front panel.
9. Once assembled determine the length and width of the front panel and cut accordingly. You can use 20-22 mm panels for the front panels. Chamfer sides 45 deg as seen in drawing. Exact dimensions are not critical. The outer panel is only from bottom to top of 8008 driver. Use a router to make the curved finish. Routing radius is 230 mm like the DTQWT-mkIII.

10. Route for drivers - and not before you have them at hand! And don't forget to make serious chamfering of 8008 hole due to the thick front panel. Check out TQWT file to see how to route for drivers and waveguide.
11. Check out DTQWT file to see how to place damping material. Please calculate yourself how much you need.
MDF or Baltic birch? The choice is yours and I wouldn't be able to tell you the difference.
Please read the two files above to catch up on all the work and thoughts that went into this giant speaker.

Cabinet damping


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