SEAS E0021 W12CY001



The W12CY001 is a mid-woofer from the Seas Excel series. It uses a surface treated magnesium cone coupled to a natural rubber surround and showing no signs of the commonly midrange edge resonances. The extremely stiff and light cone gives tremendous bass precision and midrange detail.

Heavy copper rings are mounted above and below the T-shaped pole piece and reduces the non-linear and modulation distortion and increase the overload margin.

An extra-large magnet system is used for good sensitivity and transient response as well as copper plating of the top and bottom plates and a solid copper phase plug, which enhance the performance of the copper rings and improve heat conduction away from the pole piece.

This driver is one of the very best small mid-woofers on the market in its class. For its size it has great woofer capabilities and has an overall smooth frequency response characteristic up to the cone break-up at 10kHz. This cone break-up needs to be taken special care of with a special notch filter in the cross-over filter design. Failure to take care of the cone break-up results in a driver unit with a very fatiguing sound and that “rings like a bell”.

This loudspeaker driver unit needs to be crossed over low in frequency in order to keep the odd order harmonics distortion at bay. I recommend a cross-over <2500Hz.

SEAS spec sheet: W12CY001

T/S Parameters:


T/S parametrs are measured both when the driver unit are cold and when warmed up with a 1 hour stress stimulus  at 5.66V (4W/8Ω). The warmed up driver units are rested for 2-3 minutes before they are measured.








Free air impedance measurement “cold” driver units:

Sample 1 = Green

Sample 2 = Blue

The samples are an almost perfect match between eachother and they have a very smooth impedance response curve with no signs of any resonances besides the cone break-up at 10kHZ


Free air impedance measurement “hot” driver units:

Sample 1 = Green

Sample 2 = Blue

The Fs is lowered by 4-5Hz, but otherwise they have the same smooth response curve as the “cold” driver units.




Frequency measurement conditions:

The mid-woofer is measured mounted in a 8 liter Dayton Audio enclosure (PartsExpress part #302-701) baffle with the following conditions:

Baffle size (WxH): 19,05×30,48cm (7,5″x12″)

Driver position: Mounted on center-line with driver unit center 10cm from bottom of the baffle.

Mic position: 1m distance, 12.2cm above driver unit center (tweeter-axis)

Smoothing: No smoothing applied.

0deg tweeter-axis
Sample 1 = Blue
Sample 2 = Red

Nice consistency between the two driver unit samples. Downwards sloping frequency response from 2kHz. Heavy cone break-ups at 10kHz, 13.5kHz and above.The cone break-up at 10kHz needs to be corrected for with a notch-filter in the cross-over.

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

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



Measurement setup:

  • Mid-woofer near-field measurement at 15cm
  • Frequency Range Mid-woofer: 200-10000Hz
  • Baffle size WxH: 19,05×30,48cm (7,5×12″)

The distortion measurements are done in near-field and the amplifier output level was adjusted for each driver so that the fundamental is 85dB, 90dB and 95dB at 1m. This setting simulates medium, medium-high and high listening levels.
W12CY001-1L--15cm 85dbW12CY001-2R--15cm 85db

(click on picture to zoom)

85dB @ 1m

Left = Sample #1

Right = Sample #2

W12CY001-1L--15cm 90dbW12CY001-2R--15cm 90db

(click on picture to zoom)

90dB @ 1m

Left = Sample #1

Right = Sample #2

W12CY001-1L--15cm 95dbW12CY001-2R--15cm 95db

(click on picture to zoom)

95dB @ 1m

Left = Sample #1

Right = Sample #2

The mid-woofer has cone break-ups at 10kHz and 13.5kHz. These break-ups show up in the 3rd harmonics at 3.3kHz and 4.5kHz and at the 5th harmonics at 2kHz and 2.7kHz. The 2nd order harmonics is what stands out here. It’s as low as the odd-order harmonics up to 2kHz. I think this fact contributes to the very neutral and uncolored midrange presentation this driver unit reproduces.

This driver is optimally used with a cross-over <2kHz, but it can be used up to 2.5kHz depending on how steep the cross-over filters are.