DIY'ing ribbon drivers?

[fr0st]

Hi all
From all the comments I've seen, most people rate ribbon drivers quite highly and there apparent simpilicity makes them quite apealing to DIY.
The plan sofar is to get the left over copper copper foil (25 micron, 4mm wide) as the ribbon for starters. I also have left over mylar from some ESL making if it requires some extra strength.
I just have a few questions related to the constructions of the ribbons themselves.
Is it ok to run two ribbons down the one gap, one above the other?
or... can I use the mylar to insulate between two copper strips (effectively one ribbon)? The only problem is that the ribbon would be alot stiffer as opposed to a single. (lower effieciency?)
In order to keep up with 6.5" driver in a two way speaker, what sized driver would be best suited? (or perhaps a name of a comercial driver that can for reference)
If anyone has ony other advice please feel free to share


Thanks
Matt

[MarkMcK]

Hi Matt,

I did not want your thread to go unanswered. You may have entered territory a little too strange for most of the active posters.

You also have some design challenges ahead. While ribbons are relatively easy to construct, they pose two challenges. They require extremely strong magnetic fields and they have very low impedances unless you go to a printed circuit/race track design "ribbon." The Parts Express PT2 (and the old infinity EMITs) is an example of this quasi ribbon design.

The strong magnets can be delicate and even dangerous (to fingers) to assemble, and the low impedence of the true ribbon can require transformer coupling. Both make this a much more difficult construction project.

Copper is not typically used because of its higher mass and lower heat conductivity. The heating of the ribbon will make it expand and deform. This deformation makes "slapping" and then arcing very likely in the two layer ribbon design you envisioned. I remember watching the old Gold Line ribbon speakers that actually had the vapor deposited gold conductor visably deform from 4 meters away at merely moderate listening levels. For heating problems, aluminum is still the metal of choice in ribbons. The heating also makes polymers suitable for electrostatics unsuitable for ribbons.

If you can find anyone with an old Speaker Builder magazine collection, I know they printed a couple of articles on ribbon construction. One artcle unrolled a metal foil capacitor to source the ribbon. This might help you formalize your design.

Good luck with your project and try to get to doing instead of just thinking,

Mark

[Pjotr]

Hi Matt,

Apart from Mark’s remarks forget about copper foil. Aluminium is the optimum of all known metals concerning efficiency.

In John Borwick's “Loudspeaker and headphone handbook” there is a very good analysis of ribbon tweeters.

Cheers

[Raoul]

Have you seen this? The actual construction of this speaker is described in a copy of audioXpress. I can look for the article if you want, but it might take me a while to get it scanned...

http://www.audioxpress.com/bksprods/books/bkaa65.htm

[Pjotr]

Originally posted by Raoul

http://www.audioxpress.com/bksprods/books/bkaa65.htm

That is a lot cheaper than Borwick’s book.

[Volenti]

Originally posted by MarkMcK

Copper is not typically used because of its higher mass and lower heat conductivity.

The higher mass part is correct, but copper has almost twice the thermal conductivity of alluminium.

[planet10]

audioXpress now has a book on the subject Ribbon Loudspeakers by Justus V. Verhagen

dave

[Leeuwarden]

I bought the book written by Justus Verhagen. Haven't started reading yet but I was wondering if there is anyone out there who actually built his ribbons?



Jan

[fr0st]

Thank you for your replies

I'm going to experiment with the ribbon (seems like noone from the diy scene had published anything about thier success and failures anywhere) but it seems like aluminium looks the most promising from your surgestions (and commercial usage).
From the pictures orca have of the Raven R3 in the datasheet, the ribbons looks about 17cm long and 1.5cm wide and is highly corrugated. One thing that is puzzling me is how they keep the corrugations if the ribbon is highly tensioned? (I'm assuming it would be to reduce the time it take to reach its rest position to retain the accuracy there renound for)
For the magnet structure, I'm going to use neodymium but i'm unsure whether to use lots of smaller magnets (10mm diameter x 3mm thickness) lined at the the edges of the ribbon (no top plate) or have four larger magnets (15mm diameter x 20mm thickness) and use a top plate.

They require extremely strong magnetic fields and they have very low impedances unless you go to a printed circuit/race track design "ribbon." The Parts Express PT2 (and the old infinity EMITs) is an example of this quasi ribbon design.

I was considering a running multiple smaller ribbons but that would require the ribbon to be looped back around (from top to bottom out of the magnetic field) which would no doubt create inductance so I abbandoned the idea.

Copper is not typically used because of its higher mass and lower heat conductivity. The heating of the ribbon will make it expand and deform. This deformation makes "slapping" and then arcing very likely in the two layer ribbon design you envisioned. I remember watching the old Gold Line ribbon speakers that actually had the vapor deposited gold conductor visably deform from 4 meters away at merely moderate listening levels. For heating problems, aluminum is still the metal of choice in ribbons. The heating also makes polymers suitable for electrostatics unsuitable for ribbons.

I've seen a picture of a ribbon tweeter that uses heatsinks at the top and botton of the ribbon which seemed to me like an obvious solution to the heating problem. Although the heat disapation would ultimately be limited by the thickness of the ribbon.

The plan sofar is a 17x1.5cm corrugated ribbon, a horseshoe piece of steal with the gap lined with 3mm thick neodymium & small aluminium heatsinks on the ends of the ribbon.
I have intentionly missed out the transformer for now but after electrostat transformers they don't look that hard

Thanks again for your replies
I thought the thread was doomed for a while there

Matt

[dnsey]

You might like to take a look at
http://www.audiodesignguide.com/mag/...a/lafolia.html
Perhaps not quite what you're aiming at, but a lot of tips to help!

Edit: the system couldn't handle the full URL; it's www. followed by audiodesignguide.com/mag/lafolia/lafolia.html