Transducer v3


I wound a new voice coil on a former made out of card. I tried it with two layers first, but this would barely fit into the 1.2mm airgap, so I ended up taking one layer off. The measured resistance was 2.2 ohms. Not good. I'll need to get hold of some much thinner wire which will reduce the power handling, but that's not an issue for this project.

It's time to consider the suspension system. At least something that will hold the former in position. For a temporary solution I used some elastic bands.

I used a plastic lid to roll the former around. The elastic when stretched around the former was deforming it, so I left the lid inside to keep it in shape. An AOL cd was used for the cone. About the only thing it's good for. This was stuck down using some blu-tac which removed the crackling noise made by the former banging against it when only tape was used. Now I could better hear how much noise was coming from the voice coil scraping the top plate.

One interesting point is the amount of sound emmitted from the voice coil/former alone - without a cone. There was little difference when attaching a cone relatively speaking. This makes me wander how much the spider, former and vibrations in the magnet assembly contribute to the sound in commercial transducers. They clearly add to the sound produced by the cone surface but I've never heard anyone speak of the sonic effects of say, an aluminium former. Could this be another reason for choosing one former material over another?

The Suspension System

It was difficult trying to reduce contact between the voice coil/former and the top plate. There was a clear change in perceived output and frequency range with minor changes. The suspension system is evidentally going to be very important. Until I get that voice coil centred throughout its excursion without touching anything, I really can't make any guesses as to what i'm going to end up with.

Looking back, I would probably have done better to use a larger air gap. This is a learning project after all, and at the moment the gap is as tight as a duck's arse, and proving difficult to work with. I guess I could always open it up by 1mm or so.

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Copyright © 2006 Vikash Chauhan. All rights reserved.