Vifa Coaxial Project Page
The Vifa coaxial drivers were originally used in several M & K home theater speaker systems. We have some very creative customers who have put these drivers to good use. This page is dedicated to showing off their designs. If you have a design you would like to share with our customers, please email it to us.
A little while ago I bought a pair of the Vifa coax drivers you have for a project and thougth I'd share it with you.
I wanted to make a boombox. I used a similar volume to your suggested one but left them sealed. I put the guts of a Sonic Impact T-amp in it and used your crossover (sometimes I just get lazy). I took some pictures of it and a friend dubbed it the "Boomboxa Rustica" so I left it unfinished. I have added a 1/8" stereo jack in the front so I can plug in a CD player, MP3 player or whatever catches my fancy. It sounds great and I take it everywhere.
I made a set of simple tubes, 37" long. The drivers are apparently only good for 80Hz (well Fs is 80 Hz AFAIK). Using the basic calculation for a non-taperd TL (if that is what they are). results in:
L=c/(4*f), c:=1133ft sec^(-1), L:=37" or 3.083 ft ----> f=c/(4*L), f=91.87HZ
into 1/2 space, there would be a boost of 6dB, using the "field" equation: dB (referenced to "0" dB):=20*log(2)
Because of the speaker playing into 1/2 space, it is capable of creating a
frequency much lower. I suggest that it is capable of something like 1/2 of
"f", so 45.94 Hz. This corresponds well to my listening observations.
I have no means for measurements. Perhaps I was just lucky? The tube is lightly
stuffed with Dacron and lined with some thin blue foam used to dampen the PVC
pipe. Cross-overs are 2nd order Polk salvaged crossovers purchased over the
internet. The values are similar to your provided schematic.
The TEAC "retros":
Basically I just pulled the original small driver out of the speakers from an old TEAC Reference 100 mini-system. I disconnected the existing tweeter, but left them in the enclosures. The stock cross over provides signal to the tweeter and mid-woofer (if you can call a 3-1/2" or 4" driver a "mid-woofer"). These easily better the stock speakers with more apparent bass. The boxes are only 4-1/2"X 6-3/4"X 7-1/2" and are ported. I did not change the box tuning. (1" diameter port, 2" long). The box is made of 1/2" "hardboard". These are very good for so little money. Great on the desktop, as home theatre surrounds or as a small speaker package to play music as originally intended (as long as not too loud). New enclosure could be built using better material. If I do I'll report the improvements (if any).