Variable tension apparatus for transducer analysis

[thadman]

I'm interested in building a 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).

I've conducted significant research within the AES E-Library as well as my Universities research library with regards to ribbon transducers. Only a few articles have been published, and of those, very little research regarding the behavior of the membrane was conducted.

Assuming I can get access to the Universities measurement equipment, I'd like to do testing on a variety of transducer alignments, specifically low and high compliance membranes.

Haphazardly clamping the membrane does not appear to possesses the rigor necessary for a scientific analysis of transducer behavior.

To achieve an accurate correlation between experimental and simulated results, it will be necessary to apply a very specific, measurable force at the ends of the membrane.

I'm not sure how/where to build/purchase/acquire access to such a specific machine...or even what to google. If any users could provide help with regards to the aforementioned topic, I would be very appreciative.

Thanks,
Thadman

 

[bluelava0207]

I assume you're not applying just a constant force to the ends. If that was the case, I'd say just use calibrated scale weights. If you want to vary the force with time, how fast are the vibrations you want to create?

You could get any machine that pushes up and down on the membrane. Measure the force required to deflect the membrane. As the machine pushes the membrane, you will know what the force is from the deflection. Is this what you're talking about?

 

[thadman]

I assume you're not applying just a constant force to the ends. If that was the case, I'd say just use calibrated scale weights. If you want to vary the force with time, how fast are the vibrations you want to create?

You could get any machine that pushes up and down on the membrane. Measure the force required to deflect the membrane. As the machine pushes the membrane, you will know what the force is from the deflection. Is this what you're talking about?

The apparatus will be required to tension the membrane. After which, the membrane will be rigidly clamped to sustain a constant tension. Current will be applied to the membrane which will generate an electromagnetic field that will interact with the permanent magnetic field generated by 2 parallel rows of neodymium magnets. The membrane will deform as a result of this interaction over a specific bandwidth (100hz-20khz).

 

[tyroman]

This equipment should help insure a constant tension from test to test, however some other device will be needed to establish the initial design tension.

Google; Extensometer or "Laser extensometer"