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rf-7 question


knorman

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should the speakers be hooked to the 8 ohm or 4 ohm terminal of the power amp? I have a mcintosh mc202 and mac c42 preamp. I have it hooked to the 8 ohm side currently, but I wonder if the 4 ohm terminal would better the sound? IC's are balanced and speaker wire is bi-wired. The room is large and irregular (18ftx28ft) with another 15ftx15ft extension to one side. One speaker is in a corner and the other in the open space. Listen to light jazz only. Any advice or opinions will be greatly appreciated.

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The RF-7's dip down into 4 ohm territory several times, so from a tube amp's point of view -- it's a 4 ohm speaker. Using the 4 ohm taps gives you better damping on the LF side. However, as frequency increases, impedance rises as well, and since tube amps are voltage driven as opposed to current driven -- output increases as frequency and impedance go up. So, the 4 ohm taps help with bass response, but the treble begins to tip forward a little. The swamping resistor causes the amp to see something closer to a constant impedance so that it produces a flatter response. With the swamping resistor, the amplifier sees a '4 ohm speaker'. The RF-7's sound much smoother run this way.

The downside is that since the resistor is chewing up power and turning it into heat, you lose some of your amp's output capability (you'll reach clipping sooner). I used this setup with my RF-7's and 60wpc Quicksilvers, and could still easily reach the limits of what my hearing could stand. However, I was sitting only 12 feet back from the speakers. I used a Mills 12 watt resistor, and this seemed to work fine for me.

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