Raidho D-2.1 loudspeaker Lab Report

Raidho claims an 89dB sensitivity for the D-2.1 but that is remote from the 83.0dB pink noise figure we recorded. Impedance could have been reduced to increase this somewhat but Raidho appears to have preferred to make the D-2.1 a little easier to drive than many modern floorstanders. Although the measured impedance dips to a minimum of 3.7ohm, a little below the >4ohm quoted by Raidho, impedance phase angles are low so the EPDR (equivalent peak dissipation resistance) falls to a minimum of 2.0ohm at 20Hz with a more practically relevant second dip to 2.4ohm at 210Hz. Compare this with the 1.7ohm we more typically record.


Forward response indicates a depressed presence band relative to a fairly bright treble


Cabinet modes are well contained but the pseudo-ribbon tweeter shows numerous resonances

The forward frequency response(s), measured at 1m on the tweeter axis, show a deep, broad presence band suckout, followed by rising treble output above 10kHz [see Graph 1]. These contribute to quite high response errors of ±6.0dB and ±6.7dB respectively for the pair, and matching of the two was also a little wayward at ±1.9dB over the same 300Hz to 20kHz frequency range, although much of this is accounted for by a narrow-band disparity at 11kHz. Ignoring this the pair matching error drops to ±1.3dB, and still further to ±1.0dB below 9.8kHz. Diffraction-corrected nearfield measurements recorded a bass extension of 37Hz (–6dB re. 200Hz) – a good figure for a speaker of this size and further justification for the low sensitivity. The CSD waterfall [Graph 2] confirms that much of the treble unevenness is associated with tweeter resonances. Past experience has shown that isodynamic tweeters give variable distortion results when measured nearfield, so the D-2.1's was measured at a mic distance of 250mm. KH

Sensitivity (SPL/1m/2.83V – Mean/IEC/Music): 84.8dB / 83.0dB / 81.5dB
Impedance modulus: minimum & maximum (20Hz–20kHz): 3.7ohm @ 146Hz / 15.9ohm @ 3.1kHz
Impedance phase: minimum & maximum (20Hz–20kHz): –18° @ 6.1kHz / 34° @ 968Hz
Pair matching/Resp. error (300Hz–20kHz): ±1.9dB / ±6.0dB / ±6.7dB
LF/HF extension (–6dB ref 200Hz/10kHz): 37Hz / >40kHz / >40kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) : 0.9% / <0.1% / 0.3%
Dimensions (HWD) / Weight (each): 1055x200x520mm / 44kg
Price: £37,995-£41,995

Raidho Acoustics (Dantax Radio A/S)
Supplied by: Decent Audio, Stockton-on-Tees
05602 054669