audiozaz
rtfm!? - tl;dr
I recently decided to try the K-Tubes inverted, that is, with the slots facing upwards. I found this made for a better meshing of wavefronts with the K12 below. I had also previously measured the time offset between both modules and found that the K-Tube needed to be way recessed relative to the K12's front, so much that the small module I had made would topple down backwards if pushed back enough. I quickly made the following:
It allows for different tweeter angles and can be arranged as slot-up or slot-down. It's simply two 1/8" thick 1" wide steel flatbars attached to the ladder-brace on the back. Wingnuts provide enough torque to hold the tweeter in place with friction. I did not measure time-alignement yet, but it's got to be pretty close to what I remember.
The K-Tube's power response quickly goes down towards the side of the tube where there is not slot, so I can "aim" the tube about an inch over the K12 front edge and still avoid much diffraction, although a piece of felt or foam on there could maybe still improve things a bit.
Another modification I've made at the same time is to change the previous speaker-level crossover of 3kHz to 1.5kHz. The K12 still has a high-level 2nd order network as well as a Zobel, but I've made a PLLXO for the HF, which is handled by my RCA/Victor 6BQ5 PP amp, whose OPT is directly coupled to the Selenium D220Ti on K-tubes. I like this very much so far. The Tube plays very well down to 1.5kHz and no passive components in front certainly help.
The vacuum tube amplifier also has 0dB voltage gain, it's pretty much a power buffer, so it pads down the more sensitive compression driver, even a bit too much, as I have to adjust the level controls on the Yamaha M-45 which drives the K12 to match levels.
az
It allows for different tweeter angles and can be arranged as slot-up or slot-down. It's simply two 1/8" thick 1" wide steel flatbars attached to the ladder-brace on the back. Wingnuts provide enough torque to hold the tweeter in place with friction. I did not measure time-alignement yet, but it's got to be pretty close to what I remember.
The K-Tube's power response quickly goes down towards the side of the tube where there is not slot, so I can "aim" the tube about an inch over the K12 front edge and still avoid much diffraction, although a piece of felt or foam on there could maybe still improve things a bit.
Another modification I've made at the same time is to change the previous speaker-level crossover of 3kHz to 1.5kHz. The K12 still has a high-level 2nd order network as well as a Zobel, but I've made a PLLXO for the HF, which is handled by my RCA/Victor 6BQ5 PP amp, whose OPT is directly coupled to the Selenium D220Ti on K-tubes. I like this very much so far. The Tube plays very well down to 1.5kHz and no passive components in front certainly help.
The vacuum tube amplifier also has 0dB voltage gain, it's pretty much a power buffer, so it pads down the more sensitive compression driver, even a bit too much, as I have to adjust the level controls on the Yamaha M-45 which drives the K12 to match levels.
az