, Panels, membranes, conductive coating and spacing

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Andrew Tomlinson2004-02-23 22:21

Hello Andy. What did Acoustat use for the conductive coating on the mylar film? What is the stator to diaphgram spacing. Thanks in advance.

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Andy Szabo2004-02-23 22:21

The conductive coating was a proprietary formulation developed by a chemist under contract to Acoustat. I don\'t have the formula, and it probably remains the intellectual property of whoever owns Acoustat today. I do know it contained carbon black, several solvents, and dissolved plastics. The solvents and plastics helped the coating bond to the mylar diaphragm, and the carbon black was ground to yield a specific resistivity.

Incidentally, Acoustat\'s coating was re-formulated in the late 1980\'s to have a higher resistivity, and thereby operate closer to the ideal ”constant charge”. This allowed the speaker to produce higher dynamic peaks without ”crackling”, and eliminated the random discharges sometimes observed in high humidity conditions. Panels made with the ”new” coating have a bias wire that is yellow with a red stripe. Older panels had either a solid red or white/red striped bias wire. The new coating did not change the sonic character of the speaker, but did considerably increase its dynamic cabability, most noticeably on the smaller models. All Spectra models were produced with this new coating, as well as the very last of the predecessor models.

The diaphragm-to-wire spacing for Acoustat was about 2.5 mm.

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