My TQWT build some time ago, was straight forward, following the excellent and detailed plans laid down by Mr. Gravesen.
I used 22mm MDF covered with bamboo veneer. Only deviation in my build, was heavy oakwood ring for extending the woofer for 2,4 cm, instead of building the additional front plate.
I bypassed 8,2uF Alumen tweeter cap with Duelund JDM Pure Silver Foil 0,01 uF, and kept tweeter 1R0 resistor (as the most appropriate).
After hundreds of hours of listening and changing so many other components, I am ready to give my assessment of the TQWT. Of course this is strictly subjective perception with my old ears in my room, with my gear.
I have dedicated Win Server 2019 music server, heavily modified Intel NUC Tiger Canyon in Acasa fanless case, Matrix Element H USB interface, IFI Audio Gemini 3.0 USB cable is with separate power/audio. All powered by separate PSU 19V, 12V and 5V. DAC is Musician Pegasus, amp is Pathos Classic Remix, analog cables Acoustic Zen.
I have dedicated acoustically treated room 4m x 5m x 2,4m.

First thing I noticed is the excellent reproduction of voices, male or female. Diana Krall, Alison Krauss, Jill Johnson, Miranda Lambert, Maria Callas, Kiri Te Kaneva or even 60 + years old recordings of Kirsten Flagstad. No sibilance! Very natural sounding female voices in all kind of vocal timbres. Male voices also very faithful to mention only few singers with J, Jack Johnson, Jackson Browne, James Taylor, John Mayer or John Fogerty.

At the recent Audio Show here in Ljubljana, I heard $$$ speakers with much less convincing male voices. Next thing I praise is the stereo imaging, boxes disappear acoustically. When I listen Malia (w BB) the sound is very enveloping like coming from the outer space. And her voice deadly in the centre and above. It depends great deal of the recording.
The TQWT are also very transparent to the source and amplification. Whenever I changed the source, even a miniscule change would be noticed for better or worse. Bass reproduction is punchy and extended - beyond my expectation.
To build TQWT or DTQWT was eternal question for me, I may never have an answer. Luckily the bass reproduction is more than adequate for my room size. Better then my previous speakers ATC or Dynaudio C1.
Every bass note is clear down to 30-35 Hz and has a nice timbre (bellow 40 Hz the room modes are prevalent). I built the pair of BMS 12in ported subwoofers tuned to 26Hz, driven by Hypex FA501, but they are contributing very little and after a lot of DSP changes and measurements and repositioning, I crossed them low at 40Hz. Sometimes I listen the music without subs.
TQWT, as others have said are good for all kind of music, maybe IMO leaning towards fusion jazz and rock (sound very good with George Benson/Earl Klugh - Colaboration 1987). But sounds good also with classic music preferably chamber music. I was pleasantly surprised with Vivaldi - Four Seasons - Alexandra Conunova - Orchestre International de Genève 2020.
Well even though the midbas dynamics is also pretty good, maybe little under par compared to Dyna C1 and Gryphon Callisto combo I previously owned, which were real midbas champions in my book.
Now I might be wrong since I owned completely different equipment, so difficult to compare. All in all, very pleasant and excellent sounding boxes are here to stay.
Thank you Mr. Gravesen for your great contribution to our HIFI community. Regards, Predrag from Ljubljana