ScanSpeak 18W/8545-01



The 18W/8545-01 is an 8Ω mid-woofer from the ScanSpeak Classic series.18W-8545-01_Pic2

The 18W/8545-01 is an improved version of the highly praised 18W/8545-00 midwoofer from the late 90ies. It has a new aluminum chassis, an updated cone and a new spider as wells as a few other details. These updates improves mechanical stability and the sound performance.

It uses an air dried Paper/Carbon Fibre cone which is stiff, but without the associated severe cone break-ups of the usual stiff cone drivers.

The patented SD-1 magnet system is designed to almost eliminate modulation and dynamic distortion, whilst the low loss linear suspension and rubber surround combines dynamic linearity and low colouration.

The 42mm voice-coil has an aluminium voice-coil former.

Key features:

  • Patented Symmetrical Drive Motor Design
  • Air Dried Paper/Carbon Fibre Cone
  • 42mm Voice Coil w. Alu foil
  • Low-Loss linear suspension
  • Low Damping SBR Rubber Surround
  • Aluminium Chassis


The 18W/8545-01 replaces the  18W/8545-00 version, which is about to be discontinued.

ScanSpeak Spec sheet: 18W/8545-01


T/S Parameters:

T-S parameters 18W8545-01

Good consistency between the two tested driver unit samples. As often with ScanSpeak mid-woofers the offical specification is far off the true measured T/S parameters. It has about 40% higher resonace frequency than the Manufacturer specification.


18W-8545-01 -- Imp 1L vs 2R


The two tested driver unit samples measures identical. The same small wrinkle around 900Hz can be seen in the impedance plot  as in the old 18W/8545-00 mid-woofer version.



Frequency measurement conditions:

The mid-woofer is measured mounted on a baffle in an 19 liter closed enclosure with the following conditions:

Baffle size (WxH): 24×35cm with 18mm round-over on the baffle edges (r=18).
Driver position: Mounted on center-line with driver unit center 22,4cm from the top of the baffle.
Mic position: 1m distance, on mid-woofer-axis.
Smoothing: 1/24 octave smoothing applied.

18W-8545-01 Freq 0deg 1L vs 2R jpg18W-8545-01 Freq 15deg 1L vs 2R jpg

(click on picture to zoom)

Left: Frequency response on-axis (Blue=sample#1 Red=sample#2).
Right: Frequency response 15deg off-axis (Blue=sample#1, Red=sample#2).

The two mid-woofer samples measures virtually the same. The broad hump between 500 and 1000Hz is due to the effects of the test enclosure’s baffle step. The 18W/8545-01 mid-woofer has a slightly smoother frequency response than the old 18W/8545-00 version.

18W-8545-01 Freq 0-15-22.5deg

0deg = Blue
15deg = Red
22.5deg = Green


18W-8545-01 Freq 30-45-60deg

30deg = Blue
45deg = Red
60deg = Green

The mid-woofer starts to roll-off at 2.5kHz and a good start for a x-over cross-over point would be somewhere around 1.8-2.2kHz.



Measurement setup:

  • Mid-woofer near-field measurement at 15cm
  • Frequency Range Mid-woofer: 200-10000Hz
  • Baffle size WxH: 24×35cm


The distortion measurements are done in near-field and the amplifier output level was adjusted for each driver so that the fundamental is 90dB and 95dB at 1m. This setting simulates medium-high and high listening levels.

18W8545-01-1L--15cm 90db18W8545-01-2R--15cm 90db

(click on picture to zoom)

90dB @ 1m

Left = Sample #1

Right = Sample #2

18W8545-01-1L--15cm 95db18W8545-01-2R--15cm 95db

(click on picture to zoom)

95dB @ 1m

Left = Sample #1

Right = Sample #2

Overall this is a low distorting mid-woofer. We have an elevated second-order harmonics between 0-7-1.5kHz, but the odd-order distortion profile is low throughout the frequency range.

The 18W/8545-01 mid-woofer has a slightly lower distortion profile than the old 18W/8545-00 version and for such an old base design, this is a respectable performance and it can still compete with modern mid-woofer designs.