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jessie.dazzle wrote:

Romy wrote: "...The use of the Vitavox AK151 driver is very good.  They went for 8-ohm coil. Well, this is interesting. Srajan promoted in his article Kevin and SET devote and then Kevin drops the AK151 impedance from 16 to 8 ohm..." I think it does not matter what was the originally intended. According to the Vitavox spec sheet, the AK151 always did have an "8" Ohm coil (nominal rating as indicated on driver housing is 7 Ohms). Its the K15/40 that has the "16" Ohm coil (nominal rating as indicated on driver housing is 15 Ohms). The K15/40 is the version that was originally intended for use as a direct radiator.

Interesting, as all my drivers, the AK151 and K15/40 are high impedance (15R-16R, DCR around 12R). I do not see a lot of difference between AK151 and K15/40 that and they “meant” to use one as direct radiator and another as horn is not really important. They have the very same resonance frequency and the same cone mass. That is all that I feel is important. If they have some minor differences in T/S characteristics then it is not relevant as a horn overrides the T/S anyhow.

I think that 8Ohm coil for Vitavox voice coil was a Vitavox fantasy based upon the facts they needed to integrated it in System 191 and they did not what to burn too much power on MF voltage divider. I would still stay with high impedance bass driver if we are in SET world at least would have the MF as LF driver to be of the same impedance if you used just one SET. If so, then you can set symmetrical clipping of your SET across the full range. If not then pretend the situation at in bass you have your output tube is starving from voltage but in HF your output tube is starving from current. Well, in the real world the only bass clipping would count….

Still, if they used the vintage drivers then let them to stay with whatever they found but if they use new production then I would make them all 16R. With no feedback SETs it would be only better…

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