Pass Labs SR-1 owner manual

SR-1 Owner’s Manual

the driver itself makes non-ideal load for the crossover. To retain performance comparable to the Rushmore something has to give, and that something is the overall efficiency of the loudspeaker system.

First off, the drivers must be intrinsically lower distortion and more neutral in their character. For this purpose we chose the best pieces that SEAS has to offer, Nextel coated cones in staggered diameters, topped off with the Crescendo high frequency dome. The Nextel coating provides for improved internal damping of the radiating surface, and we made a point of operating each driver in the “piston region” below the cone’s modal frequencies. The SEAS drivers feature long linear excursion, overhung voice coils, and exceptionally linear magnet assemblies and pole pieces.

These are exceptional drivers, the best we could find, but they still appreciate being driven by a low impedance source to achieve the most precise transient quality, the instantaneous “stop-start” response necessary to impart musical realism. Unfortunately the very nature of a passive crossover introduces reactive impedances between the amplifier and drivers, degrading the transient characteristics and creating lingering artifacts. The result is that the sonic image is smeared and the little details are obscured.

We experienced these phenomena while comparing various prototype passive networks against an actively quad-amped version used as a reference, and the difference was enough to make us choose a brute force solution – resistively shunting most of the amplifier current around the driver.

This gives the amplifier a less reactive, lower impedance load. It also gives the crossover network a less reactive, lower impedance load. Finally it provides the driver with a less reactive, lower impedance source.

There is a price to pay for this – instead of a speaker whose audio band impedance varies from about 8 to 30 ohms, the SR-1 varies

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