Klipsch RP-600M Loudspeaker Lab Report

Lab Report

We're becoming habituated to Klipsch making enthusiastic claims for its speakers' sensitivity (repeated in online 'reviews'), and the RP-600M fits the mould. Klipsch says it generates 96dB SPL at 1m for 2.83V input – which, if true, would be an outstanding result – but our tests recorded exactly 89dB, averaged for the pair, on pink noise. This is still a good result, but the 7dB gap to Klipsch's specification is a vast one. In part the sensitivity is achieved through the use of low impedance. Despite Klipsch's vague '8 ohms compatible' specification, this is a 4ohm design. We measured a minimum modulus of 3.4ohm and sufficiently high impedance phase angles to drop the EPDR (equivalent peak dissipation resistance) to a minimum of 1.8ohm at 129Hz. This makes the RP-600M averagely difficult to drive for a modern loudspeaker, but not as easy as the crib sheet implies.

Forward frequency response was measured at 1m on the axis of the horn-loaded tweeter [see Graph 1, below]. The traces are very uneven – to the tune of L/R response errors of ±5.8dB and ±5.9dB, respectively. A wide suckout between 1kHz and 2.5kHz, and a high treble peak at 17kHz, are principally responsible, the former in particular surely colouring the RP-600M's sound. A pair matching error of ±0.7dB over the same 200Hz-20kHz frequency range is a much better result. Also creditable is the bass extension of 40Hz (–6dB re. 200Hz), determined by diffraction-corrected nearfield measurement. LF output shelves down below 140Hz before falling off at 24dB per octave below 45Hz. Despite the horn-loaded tweeter, the CSD waterfall [Graph 2, below] is mostly clean in the treble, but the 17kHz peak suppresses the level of modes at 2-5kHz. KH


Response is quite uneven, with a depressed midrange allied to a rising treble above 10kHz


There's one mode below 1kHz but resonances associated with the horn treble are mercifully low

Sensitivity (SPL/1m/2.83Vrms – Mean/IEC/Music) 91.2dB/89.0dB/88.3dB
Impedance modulus min/max (20Hz–20kHz) 3.4ohm @ 192Hz, 25.7ohm @ 2.1kHz
Impedance phase min/max (20Hz–20kHz) –51° @ 105Hz, 62° @ 1.3kHz
Pair matching/Response Error (200Hz–20kHz) ±0.7dB/ ±5.8dB/±5.9dB
LF/HF extension (–6dB ref 200Hz/10kHz) 40Hz / 21.6kHz/22.1kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) 0.8% / 0.3% / 0.2%
Dimensions (HWD) / Weight (Each) 399x202x301mm / 7kg
Price £625

Klipsch Group, Inc.
Indianapolis, USA
Supplied by: Henley Audio, Oxfordshire, UK
01235 511 166