Spectra 3, Panel impedance

Read more on the Acoustat Spectra 3 in our home audio section

Jim Roller2008-08-12 15:40

What is the impedance of the panel portion of the Spectra 3? I am not using the woofer portion. I am trying to decide whether to use the 4 or 8 ohm taps on a tube amp I just picked up. thanks.


Andy Szabo2008-08-12 23:43

The nominal impedance of the Spectra 3 ESL system (i.e. transformer interface and panels) is 4 ohms. However, the impedance varies quite a bit over the audio band, running from about 2 ohms to around 10 or more ohms. Therefore, there is no correct answer to your question. The typical tube amplifier\'s output impedance also varies quite a bit with frequency, so the effect on frequency response can be quite dramatic. Each brand or model of tube amplfier will be different in this respect. My advice is to try each tap and see which one you like best - more than likely each will involve compromises, and you\'ll need to decide which combination yields the best results for your taste. The important thing to remember is that there is no wrong answer - no harm will be done to either the speaker or the amplifier from the use of the 4 or 8-ohm tap. (In fact, if the amp has a 16-ohm tap, it could be worth your time to try that, too!) One last comment - most tube amps make it easy to experiment with the output impedance, merely by choosing a different output terminal. However, I am aware that some designs require an internal wiring change, making experimenting with impedance much more cumbersome. If that is the case with your amp, and you feel it necessary to choose a tap without first experimenting, then I suggest the 4-ohm tap. But there is no guarantee that that is the best one for your taste.

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