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Old 23rd May 2011, 12:21 PM   #1
bentl is offline bentl  Norway
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Default True ribbon prototype

Hi,

I found some time this weekend to build a true ribbon speaker prototype.

the ribbon is 920 x 28mm corrugated alufoil suspended between 10x10x40mm neo magnets.

I mounted the ribbon arrangement in a solid oak baffle, hand routed and not my best work.
RibbonFront.jpg
I tested the ribbon briefly late last night by connecting it to my sourround amplifier instead of one of the small box speakers I use.

I used a 5ohm series resistor at first, and the ribbon played almost as loud and clear as the small Mission box speaker on the other channel.
RibbonConnector.jpg

I then replaced the series resistor with a 1,5ohm resistor, and the ribbon played even higher.

Feeling brave and trusting Denon to supply their amps with a decent protection cirquit I bypassed the resistor. The ribbon played just as loud as the box speaker, but the ribbon tends to move out of the magnetic gap and slightly sideways. Any idea why the sideways move occurs - and how to prevent it?

I find that ribbons are easy to build and gives a rewarding result, so I will contiue down this path and try to build a pair of ribbon speakers as front speakers for the TV/surround setup.

RobbonBack.jpg

Next attempt will be with a alu-baffle with a mesh protecting the ribbon from small fingers and toys. Possibly I will make several shorter ribbons as separate modules and connect them in series .

regards
Bent
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Old 23rd May 2011, 01:06 PM   #2
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Well done mate, thanks for going to the effort of creating the thread, good luck with the project.

Dean
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Old 23rd May 2011, 06:41 PM   #3
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Quote:
Originally Posted by bentl View Post
I Feeling brave and trusting Denon to supply their amps with a decent protection circuit I bypassed the resistor. The ribbon played just as loud as the box speaker, but the ribbon tends to move out of the magnetic gap and slightly sideways. Any idea why the sideways move occurs - and how to prevent it?
regards
Bent
Hi Bent,

I suspect the sideways ribbon movement is due to the amplifier clipping and generating some DC current because of the low impedance of the direct ribbon connection. You can destroy your amplifier and twist up your ribbon from this direct connect.

A series resistance of 4 ohms would probably be the safest way to connect the ribbon until you either build a step up transformer, or build a DIY custom solid state amplifier that is designed to drive ultra low resistance (0.1 ohm) ribbons.


The original 1984 Full Range Apogee Ribbons used a 90 degree angle iron frame similar to your construction.

Last edited by LineSource; 23rd May 2011 at 06:46 PM.
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Old 24th May 2011, 02:04 AM   #4
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Hi Bent,

That's a very nice built. Congratulations!

Wachara C.
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Old 26th May 2011, 09:17 AM   #5
bentl is offline bentl  Norway
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Hi,

It seems I will have to support the ribbon at a few points in its length as it tends to move out of the gap between the magnets.

I made the fixture for the ribbon so it is easy to replace the ribbon, so I can test different types of ribbons, tension and width.

I have not yet made any measurements and I am curious to what requency response the speakers gives

Regards,
Bent
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Old 26th May 2011, 10:42 AM   #6
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Very nice build,I like it! jer
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Old 26th May 2011, 05:25 PM   #7
Paul W is offline Paul W  United States
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What is the HP frequency and slope of your XO? I found ribbons will turn sideways in the gap if driven with LF content. Mine were 1"x45" supported at 15" intervals, so very similar to yours.
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Paul
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Old 26th May 2011, 06:19 PM   #8
bentl is offline bentl  Norway
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Hi I have only tested them full range so far. Will test them with a crossover during the weekend and also add some supports for the ribbon

I tested it briefly with my 50w tube amp yesterday and it played vert nice

I'm having a small problem with a ribbon that is to widerøe and touches the magnets and causes some rattling sounds

Will fix that as well during the weekend

Bent
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Old 26th May 2011, 08:03 PM   #9
a.wayne is offline a.wayne  United States
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question Guys :

The backing plate for the ribbons , better to be deep or thick when trying to get a stronger field ..


regards,
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Old 29th May 2011, 06:49 PM   #10
bentl is offline bentl  Norway
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Quote:
Originally Posted by Paul W View Post
Mine were 1"x45" supported at 15" intervals, so very similar to yours.
What do you meen by "were"? Did you recycle them or what?

Regards,
Bent
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