Fieldcoil + K-tube

[Retsel]

Any news on the 2 inch Transylvania tubes?

I used 1 inch K-tubes for a while with a pair of transmission line midrange drivers, Karlson boxes and subwoofers when my Lowther drivers I used in front waveguides went down. The 1 inch K tubes sounded great. I tried aiming the K-tubes directly at the listening position to extend the high frequencies at the listening position. In the end, I did not like it and aimed the K-tubes upward, but the high frequencies rolled off at about 8 khz. I added a pair of ribbon tweeters to bring up the high frequencies.

I replaced the failed Lowthers (were DX4s, now DX65s) and I am now using them from 500 hz to 8 khz in the front waveguides in lieu of the transmission line midrange and 1 inch K-tubes. At some point I will likely try the 1 inch K-tubes in lieu of the Lowther high frequencies which can be troublesome.

I am using a pair of K15 boxes and put EVM15L drivers in them. I find them quite excellent, with lower distortion and better dynamics than open baffle variants I have tried.

What did you not like about the K15s that you heard? I need to build a new pair of K15s though, because these are very old and the plywood is delaminating causing obnoxious buzzing sounds in the midrange at certain frequencies.

Retsel

[moray james]

have you tried using a double cutaway K- tube. I like them much better than a single cutaway version. I set mine up centred upon my seated ear height, the tube is parallel to the floor with the cutaway in the vertical position. I start with the tube firing directly at each ear then adjust toe in or out as required to suit my taste. I keep k- tubes on the short side at 1/4 wave of the compression drivers impedance peak or the cone drivers Fs. Longer k- tubes can be easily damped with open cell foam (25 PPI).
Please note that I borrowed the photo of the single and double cutaway k- tubes off line it is not my own, I make mine from single or double wall layer rolls of standard weight graph paper the kind in school note books. These have zero energy storage can be made or modified in a few minutes each and sound wonderful.

[as_audio]

How do you compare efficiency and directivity of both versions ?

I can not imagine that thin paper tubes have any effect as wave
guides. Dense tubular cardboard could probably be used. Thanks

[moray james]

I never measured efficiency or directivity of either version I simply listened to each and played with positioning of each and I chose the one I liked best it was not a difficult choice to make. I did not notice any difference in efficiency so far as I could tell. You would be very wrong about using paper as a tube material but if you want to make protoyping and your build more expensive and time consuming build what ever type you like. Having some hands on experience would give weight to your comment on the suitability of using paper as a tube material.
Here is a simple paper tube on one of my compression drivers this is a EV DH1A fitted with a single cutaway paper K-tube. With paper you can experiment with as many different profiles as you like to find which you like best in a single session you never have to leave the room all you need is a pencil paper scissors and a form to roll on (you don't have to have a form it just makes the process faster). Every paper tube you make will be a perfect fit for your driver exit.

[pelanj]

Double cut K-tube model for 3D printing is here: 3D printed K-Tube for 1" compression drivers and some measurements here: 3D printed K-Tube for 1" compression drivers

[freddi]

Moray, how long is that single slot 1.4" format K-tube ? I like "The Tube" and clones - on axis (straight down the tube) they go to about 17K with a DE250, but should be elevated or pointed down for best sound.

The double slot tube by Pelanj has excellent sound. It freaks me a bit that I like it best with the slots facing the ceiling and floor.

For K-midrange I hope to try a strong 6 or 8 in a regular and shallow K -"wedge". Softening the hard/sharp inside corners with auto putty might be helpful (?)

@Retsel - what compression driver do you run with the K-tube? If a crossover was high enough the Tymphany Ti with polyimide surround might be a good budget choice.

Test Bench: Peerless by Tymphany DFM-2544R00-08 Compression Driver | audioXpress

[moray james]

the tube was set at 1/4 wavelength at the impedance peak of the driver (around 475 Hz), so the tube was about 5 3/4" - 6" long. I had my tubes (double cutaway) set up so the vents were facing up and down with the solid sections of the tubes to the left and right, tubes parallel to the floor at seated ear height gave best results for me after a lot of different orientations. Hope this helps.

[moray james]

the K-Tube set up mentioned above was used for near field listening. Other orientations of the K-Tube might suit other listening goals more effectively, Omni directional reproduction comes to mind.