DIY ribbon design/construction

[thadman]

I'm interested in building a DIY ribbon loudspeaker in my free time over Christmas break and would like to drive it directly. Following the resolution of some meetings with faculty in the engineering department, I might be able to gain access to the Universities Laser Vibrometer and Anechoic chamber for measurements (and comparison with the RAAL 140-15D)

My primary goal for the project is reproducing a Dirac Pulse/Square Wave, so impulse response will be weighted with the highest significance.

A few particulars related to the design.

How have members clamped the foil? With regards to heat transfer, I believe most of the energy will migrate through this interface as air is a very poor conductor of heat.

How have members cut the foil to the desired width/length?

How have members centered the foil within the gap?

What are some sources for aluminum foil?

Thanks,
Thadman

[Andrew Eckhardt]

The highest temperature will be at the mid-section of the length of diaphram material. Cross sectional area will be so small compared to length you will not get significant thermal conductance compared to radiated loss in the middle. Burn-outs will occur there if ever. I'd consider trying to make it black?

[thadman]

Originally Posted by Andrew Eckhardt

The highest temperature will be at the mid-section of the length of diaphram material. Cross sectional area will be so small compared to length you will not get significant thermal conductance compared to radiated loss in the middle. Burn-outs will occur there if ever. I'd consider trying to make it black?

Anodizing the foil/surface etching will SIGNIFICANTLY degrade its fatigue performance, so I do not consider either of those appropriate options.

[Andrew Eckhardt]

Yeah I don't think you'd want to anodize. Maybe smudge some carbon on it. After thinking about it probably most of the dissipation will occur due to convection. If there was any way to force air without biasing the diaphram you'd be set for serious power handling.

[thadman]

Originally Posted by Andrew Eckhardt

Yeah I don't think you'd want to anodize. Maybe smudge some carbon on it. After thinking about it probably most of the dissipation will occur due to convection. If there was any way to force air without biasing the diaphram you'd be set for serious power handling.

I believe that is exactly what Stage Accompany does with some of their planars.

I believe AES has an article available on the topic (specifically with regards to SA) if you're interested.

[thadman]

There is very little research available on the AES E-Library with regards to ribbon transducers, only a few articles have been published.

Some valuable research may be procured following an exhaustive analysis of ribbon transducers. Linesource as well as finite segment ribbons could be tested.

An apparatus which provides variable tension would be required. Any ideas?

[thadman]

Any ideas on what the shape of the immediate waveguide in front of the driver should be?

The ribbon will initially launch a plane wave, which will transform into a spherical wave with respect to time. As the wave propagates down the rectangular duct, an abrupt transformation of the wavefront will occur once it reaches the end of the duct. Diffraction and Higher Order Modes (reactive forces) will result from this I believe (read: BAD).

For flat pistons, they are affected by the global pressure over the surface. However, ribbons, being elastic membranes, are affected by local pressure over the surface. I haven't done any simulations, but the reactive nature of the aperture may have an effect on the ability of the ribbon to reproduce an impulse.

A small roundover should provide a linear rate of expansion and can provide a vector that is orthogonal to the initial vector, however this seems like an obvious solution.