Overview:
The 18W/4531-G00 is a 4Ω mid-woofer from the ScanSpeak Revelator series.
It uses a sliced paper cone technology. The slices are filled with damping glue, which dramatically reduces breakup modes in the diaphragm. In combination with Scan-Speaks low-loss linear suspension and the patented Symmetrical Drive (SD-1) it represented a break through in midrange clarity and overall smooth frequency response characteristics.
The 38mm voice-coil has a glass fiber voice-coil former.
Key features:
- Patented Symmetrical Drive Motor Design
- Low-Loss linear suspension
- Die cast Alu Chassis vented below spider
- Sliced Cone (Controls Cone Breakups)
- Low Damping SBR Rubber Surround
- Large Ferrite Magnet System
ScanSpeak Spec sheet: 18W/4531G-00
T/S Parameters:
Good consistency between the two tested driver unit samples. Higher sensitivity, resonance frequency and Qts compared to the official specification. This is unfortunately common with many Scanspeak mid-woofers.
Impedance:
The two tested driver unit samples measures identical. A small wrinkle in the impedance plot can be seen around 900Hz.
Frequency:
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 23,7cm from the top of the baffle.
Mic position: 1m distance, on mid-woofer-axis.
Smoothing: 1/24 octave smoothing applied.
(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.
0deg = Blue
15deg = Red
22.5deg = Green
30deg = Blue
45deg = Red
60deg = Green
Very smooth frequency response. The mid-woofer starts to roll-off at 2kHz and a good start for a x-over cross-over point would be somewhere around 1.8-2.2kHz.
Distortion:
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.
(click on picture to zoom)
90dB @ 1m
Left = Sample #1
Right = Sample #2
(click on picture to zoom)
95dB @ 1m
Left = Sample #1
Right = Sample #2
Elevated second-order harmonics between 0.4-1.1kHz, but the odd-order distortion profile is very low throughout the frequency range.