Fisher 500-C speaker guidance

[lalla]

Hello, fellow Fisher lovers.

I've just replaced my beloved 500-C of several years past with a newly restored example and am now looking for some advice. I have previously driven my Crites updated Klipsch Cornwall I's (8 Ohm, 101db) off the 8 Ohm tap of a partially restored 500-C. I would now like to drive these same Cornwalls, along with a pair of Klipsch KG-4's (6 Ohm, 95db), with a restored and slightly updated 500-C. Is this safe? If so, should I run these off of the 4 Ohm or 8 Ohm tap?

All electrolytics in the power supply have been replaced, as has been the rectifier bridge. In addition, 10 Ohm resistors have been added to cathodes at each output tube. Coupling caps have been upgraded, as have power stage main resistors (1.2kOhm, 470 Ohm).

Thanks all!!

 

[larryderouin]

8 ohm tap. One pair on the Main, and one pair on the Remote.

 

[Dave451]

I run my KG-4's on the 8 ohm tap of any amplifier I'm using. No issues evident. Mine are labeled on the backs as 4 ohm nominal impedance, by the way. Speaker impedance varies considerably with frequency and I've encountered no issues.

 

[lalla]

8 ohm tap. One pair on the Main, and one pair on the Remote.

Thanks, Larry. This was my assumption. Having not run 6 Ohm speakers on a Fisher before, I just wanted another opinion.

Cheers!!

 

[lalla]

I run my KG-4's on the 8 ohm tap of any amplifier I'm using. No issues evident. Mine are labeled on the backs as 4 ohm nominal impedance, by the way. Speaker impedance varies considerably with frequency and I've encountered no issues.

Thanks, Dave. What are you driving the KG's with?

 

[Dave451]

Various Fisher, Scott, Dynaco and Sherwood amps/receivers. Went all tube a while back. Fisher 400 & X-200, Scott 299B, 340B, Sherwood 8000 IV, Dynaco SCA-35.
I looked at the curves and never really believed the KG4's were 4 ohm so, assuming 6 ohm like nearly all the literature said, I use the 8 ohm tap.
Dave

 

[NewKidInTown]

Can anyone share an opinion on whether or not AR 510 speakers from the 80's would run well with a 400? I believe they are 6 ohm speakers.

 

[larryderouin]

Sensitivity is 87db. Fairly inefficient for tube gear. These are really more for S.S. units of 100W or more. Find something that has a Sensitivity in the mid 90's so the 400 isn't straining so much when it's cranked to a bit over normal levels.

 

[NewKidInTown]

Thank you for the response!