The first RD75 baffle/woofer prototype by Tom Bennett. Tom who is a Bass/DIY List
member, lives in Qatar. He says that he has since taken a saw to the baffles and
created a smoother-sounding triangle baffle. More photos please, Tom? Tom can
be reached at: tcb123@qatar.net.qa
Leif Aden, a Bass/DIY List member, has been building true ribbon drivers for
sometime now. This is one of his ribbons. Lief lives "...up north near the
polarcircle..." in Sweden. He says he has the same problems as the rest of us
trying to measure loudspeakers "...you know cars, aeroplanes and other disturbing
sounds gets you crazy." Yes I do, Leif!]
In Leif's own words (English is not his mother tongue), "We have had
some problems with the membranes we used to thin Al foil and as the
polyimide foil is so thin it tends to overcome the Alfoil tension so the
wrinkles get away. Now we use a thicker Al foil and it works, my first
ribbons are about 10 years and is using the thicker foil. I think they
even sound better. As soon I get my measuring equipment in order I start
to measure it will be very interesting."
A second ribbon driver from Leif. He services PC computers for a school system,
and does part-time work repairing TVs and VCRs. Where does the
time come for ribbons? He says, "... but there´s only 24 hours and I
try to sleep sometimes. I also have a wife and three small kids and they
are very active so...."
Sure wish Leif lived closer so that I could have a listen to his good
looking ribbon drivers. We wish him the very best on his goal to market
ribbon drivers in the future. Leif may be reached at: adelec@obbit.se
Carl Huff was quick to act on the one-sided baffle information. Here's a
drawing of this new baffle with woofer. He promises a photo soon.
The woofer is a dual 1259 and the RD75 baffle can be moved back and forth on the box in order to align the planar driver with the front woofer. The woofer shown with broken lines is behind the dipole baffle.
Carl says: "I had been following your 'one sided baffle' efforts, and was
'itchy' to do something!
... So I got out the circular saw and took after one of my ribbon baffles!! ...
There clearly is a difference. Imaging is the most obvious change. ... The
altered baffle is clearly more listenable, as it has a 'warmer' sound, something
that I had not expected. ... I had not expected the sound to be as different as
what it turned out to be. ... The character of the speaker has changed. " Carl
can be reached at: chuff@tir.com
The second RD75 baffle/woofer prototype by Tom Bennett. Seems like my first
mention of the 'one-sided' baffles lead to several instances of confusion
out there in BasserLand. Sincere apologies! Tom and I have since cleared
up the one-sided baffle definition; but his initial reading of my
description led to these beauties.
Tom says much greater SAF/WAF for these than the earlier rectangular baffles; and, they are smoother sounding to boot.
These sure have a great look to them. The 'objectivist' in me says
'wonder how they measure?'
Jan Nielsen is editor of High Fidelity magazine in Denmark. Here is his
completed ribbon and planar speaker - 6 feet high and 200 lbs.
In Jan's own words:
"The same speaker at an earlier stage. The midrange/treble unit is functioning,
but the bass is a test version. The foil is a special kind which shrinks when
heated. The al conductor was later glued with 3M (not very well). Bi-amped with
the mentioned 250W/0,5 ohm amp and two 250 W/2 ohm monoamps, the system could
play quite loud. Once the left speaker started to burn. It happened when I tried
one of these qrazy test discs with a racecar at a realistic level. A soldering
iron and a piece of copperwire cured the problem in a few seconds!"
Again from Jan:
"A close up of the (left) midrange/treble magnet assembly before black felt
was added. The back-wawe is damped as the "cage" behind is filled with damping
material. At the right you see the magnets for the bass system." Jan can be
reached at: soundim@cybernet.dk
Bengt Strom contacted me for discussion of his design for an RD75 or RD50 driver on a dipole baffle combined with a woofer cabinet. This is an interesting design, incorporating features for enhancement of the woofer's coupling to the room. Bengt wants the following made clear, (in his own words):
"1. It has not been built and tested."
"2. Please e-mail me any ideas, questions or suggestions about the
construction."
"3. If anyone builds it, ABSOLUTELY they must write at least one line
letting me know how it turned out:-)"
Bengt can be reached at: Bengt@tennbergs.se
He is very interested in hearing from folks who might have further ideas
about his design.
Tom Bennett's new one-sided baffle looks familiar to me. Tom has crafted at beautiful piece of work. He's working on a different woofer implementation.
He says, "...by the way the 'unusual' finish is piano black, the incredible gloss was achieved by using a polyester clear coat which dries hard as nails, the edging on both sides is a hardwood called Meranti, similar to Mahogany."
"Talking of tweaking, my listening room is small and so I have a problem with placement of the BG's, I have been playing with a diffuser similar to the Panga, it is in the form of a 4'' PVC 75''long pipe stuffed with insulation, placed 4'' behind the BG, my initial impression is that it makes a big difference, I can now place the BG's much closer to the back wall, 2' with no appreciable loss, in a small room, that is a big help."
Tom can be reached at: tcb123@qatar.net.qa
Acoustic Line Source Research - Table of Contents.
