ScanSpeak Illuminator 12MU/4731T-00

  • Monday, Oct 22, 2012

Up for test is the Scanspeak Illuminator 12MU/4731T-00 4.5” Midrange - 4 ohm.

Note: For a while I didn’t have the means to measure frequency response accurately. Rather than do it halfway I decided it best to not attempt it. So this is one of the reviews I completed at that time and thus there is no FR/HD data.

Below is the data obtained from Klippel (LSI only) testing of the Scan Speak Illuminator 12mu in 4 ohm version. This 4.5″ midrange driver has the goods to deliver hefty bass for a nearfield, compact system or excellent midrange as part of a farfield speaker due to it’s excellent linear stroke (at 5.1mm one-way). The use of shorting rings here help to lower IMD driven distortion (higher frequency distortion caused by pushing the driver to higher excursion levels). To date, this is the best midrange driver I have tested and lives up to the Scan Speak name.

For Frequency Response measurements, please visit and scroll down to Sept 22, 2011.

Thiele-Small Parameters

Re 3.2947 ohms
Fs 74.3 Hz
Qes 0.3906
Qms 6.2385
Qts 0.3676
Zmax 55.9197 ohms
Le 0.1052 mH (@ 1khz)
Vas 3.9555 L
Sd 5857.538 mm^2
BL 4.7691 N/A
Cms 811.5327 um/N
Kms 123.2362 N/m
Mms 5.7625 g
Sens 87.8233 dB @ 1w/1m

Large Signal Analysis (LSI)

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% 6.1 mm Displacement limit due to force factor variation
X C @ C min=75% 5.1 mm Displacement limit due to compliance variation
X L @ Z max=10 % >6.4 mm Displacement limit due to inductance variation
X d @ d2=10% 15.7 mm Displacement limit due to IM distortion (Doppler)
Asymmetry (IEC 62458)
Ak 10.55 % Stiffness asymmetry Ak(Xpeak)
Xsym -0.52 mm Symmetry point of Bl(x) at maximal excursion
Power Series
Bl0 = Bl (X=0) 4.7976 N/A constant part in force factor
L0 = Le (X=0) 0.15811 mH constant part in inductance
C0 = Cms (X=0) 1.3196 mm/N constant part in compliance
K1 0.00364 N/mm^2 1st order coefficient in stiffness expansion
Xpse 8.6 mm =-Xpse < X < Xpse, range where power series is fitted


Well, as we’ve come to expect from Scanspeak, this is a very high performing driver. A 4.5” midrange with Klippel verified >5mm linear excursion. Other site’s FR data show a nice linear response from 200Hz - 3kHz with only a small cone breakup on-axis spread from 5-6kHz. With this and a sensitivity of about 90dB @ 2.83v/1m spec, this is a very high performing midrange.


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