[Quad]

I am using my Quad II amps to power my new AKG K1000's. I have the amps wired for 4-8 ohm speakers but I can change it to 12-20 ohmn setting. The amp was origionally meant for ESL's (55's) which was I think are 16 ohm speaker and they came from the factory wired for the higher setting. So they were designed with this setting in mind. To change it involves a bit of soldering so it is a small chore and a bit of a hassel.

Now the amps power the phones nicely but I am not sure if I should take the trouble to rewire them. Theoretically I think the lower impedance should be better as I think the signal has a shorter path. I could be wrong about this. The amps were designed for the higher setting so they might drive the phones that little bit better that way.

I ask this only because switching back and forth is a bit of a pain with the soldering and all and it is not like I am unhappy with the sound. I am very happy with it and will likely post some more details a bit later.

What to the folks with the electronics background/experience here think?

 

[mkmelt]

The Quad ESL-57 has an impedance curve that varies from a high of over 40 ohms at bass resonance in the range of 55 Hz, varying between 16 and 8 ohms through most of the frequency range, except above 10Khz where it drops as low as 2 ohms. Since there is very little musical content or energy demand above 9khz, it was reasonable to rate these as 16 ohm speakers.

Depending on the amplifier, they may sound better when using other than 16 ohm taps on the output transformer. I have tried the Quad ESL-57 on a Fisher 400 receiver with 4,8, and 16 ohm output taps. The least satisfactory was the 16 ohm tap, too bass shy. The 8 ohm was the best balance of sound with usable volume control range. The 4 ohm tap had the best overall sound but there was little usable range available from the volume control, as maximum output was reached with the control raised just a fraction of its range.

As far as the AKG K1000, when using the Fisher 400, the 4 ohm taps were the best sounding. The rated impedance of the K1000 phones is 120 ohms, so the best power transfer from the output stage of the amplifier would be using the 16 ohm taps, however this did not provide the fullest range of sound. I have yet to find any speaker that sounds best on the 16 ohm output taps of the Fisher 400, while both the 4 ohm and 8 ohm taps sound very good.

The lower sensitivity of the K1000 vs the ESL-57 speakers required that the volume control be raised through what I would consider a normal amount of travel, i.e., between 9 and 10 O'clock as I recall.

Bottom line, if you are satisfied with the sound of the K1000 with your Quad II amplifier when using the 8 ohm taps, I would leave things as they are.