The Trike (From HiFi News & Record Review 50 years ago!)

This is a very easy build and low cost as well at least for the enclosure. The aim is to use cardboard tubes to make a quarter-wave pipe. The simplest construction would be to simply block one end of a pipe and put a loudspeaker driver there. Here there is a trick were a smaller diameter tube is inserted into the larger one. The pipe is then in reality in three sections. 1. The smaller pipe, 2 the outer pipe minus the area of the inner pipe and 3 the outer pipe.

The inner diameter of the outer pipe (M) should be 1.5 times the effective cone diameter of the driver. The driver is a Phillips AD3701M a 6.5" driver with a cone diameter of about 130mm so 1.5 times that is 195mm and the pipe is 200 mm. Height of the outer pipe should be about 4 times its inner diameter or in this case 800 mm and that it what it is. The inner pipe inner diameter should be 0.6 M-wall thickness of inner-pipe so that is 200mm times 0.6 minus 4mm wall thickness = 116mm. As far as I can tell it is 118-120mm close enough. The average lenght of the inner pipe is 0.6 of the length of the outer pipe, in this case 480 mm.
M=1.5 cone diameter, T=0.6M-t (keep it above 0.5 and below 0.7)
H= 4M and d=0.6h

The building material. Going right to left: The pipes from Bauhaus, in the US it would be Home Depot and such. The drivers are from old Philips speakers bought at a thrift store at a very low cost. The plate and the bowl have the right diameter for marking the cutouts. Never use the cardboard tubes to trace the cuts as they are not truly circular.  The outer tube is fine as it is the inner has to be cut to the right lenght and slant. Cables and connectors is needed. The inner tube will get some bonded acetate fiber (I do not like to work with fiber glass. The green felt to the left may come in handy if I need to add some more damping material in the pipe.  The pine board will be material for the baffle of the driver and blocking the end of the inner pipe. Missing is some kind of feet to lift the pipe up from the floor to a hight of M/10. The feet will depend on how I finish the tubes, cover with a nice fabric, painting it, wall paper perhaps. I think I will build it first and if I like the sound I will work on the looks ;)

DIY Loudspaker plans for 2012

At long last I am about to embark on several DIY projects.  Last year I sold my large transmission loudspeakers and now really have to get some proper HiFi setup going again. And yes I know that I could get at least good sound by buying them of the shelf, but what would be the fun in that!

Preliminary candidates are as follows.

1. Jericho XII, based on the Jerricho 08 design from Klang & Ton but with some improvements and changes for my particlular setup.
2. Axiette of evil. A bassreflex design for the vintage classic Goodman Axiette, bessel tuning and vent geometry of the Onken type.
3. Onken 180, a "small" onken like box with the Eminence 15" Omega Pro 15A driver. Not a true Onken as far as tuning goes but vent geometry and the large total vent opening is similar.
4. Mjönir, a front loaded bass horn with Beyma 12" as horn driver...
5. CT 164, my take on a small backloaded horn using a Tangband 4" driver.
6. Mini TLS, Atkins HFN&RR design from the 80s, using modern Peerless and Seas drivers.
7. Trike, a HFN&RR design of a Voigt pipe using cardboard tubes as enclosure!
8. The Post horn, a vintage design dating all the way to the 50s, in original a mono design with the driver facing the backwall and no damping material at all inside the enclosure. The damping was improved in the HFN&RR publication by removing a brace! The thin (12mm) walls should absorb resonances by flexing.

How many of these I build and what order will depend on mood as well as time and space constrains, the last one imposed by my dear wife.