A variable geometry compressor for use in, for example, a turbocharger. A swing-vane diffuser is provided down-stream of the centrifugal compressor wheel. A nozzle ring is adjustable mounted on a center housing, and defines the nozzle face for the compressor diffuser. No spacers are deployed in the diffuser thereby improving efficiency, yet by stacking only the vanes and the nozzle ring, the diffuser clearances are maintained within strict tolerances. Further, seals, such as O-rings, are situated between the nozzle ring and the compressor housing and back plate to eliminate deleterious gas leaks between the diffuser and the spaces behind the nozzle ring.