The 27TDFC (H1189) is a tweeter from the Seas Prestige series. It offers a sturdy build quality with a glass-fibre reinforced plastic faceplate. It has a wide, soft polymer surround and the coated fabric dome diaphragm provides a frequency response to 35kHz (on-axis), with a nice off-axis dispersion and low distortion.

The Sonotex precoated fabric diaphragm has high consistency and excellent stability against variations in air humidity.

Voice coil windings immersed in magnetic fluid increase short term power handling capacity and reduce the compression at high power levels.

Stiff and stable rear chamber with optimal acoustic damping allows the tweeter to be used with moderately low crossover frequencies.

This is a very affordable tweeter that measures very well and is capable of  a 2kHz cross-over point or even lower if a steep filter is used.

Seas Spec sheet: 27TDFC (H1189)

T/S Parameters:


Good consistency between the samples and they have slightly lower resonance frequency than the manufacturers specification.








Free air impedance measurement:
Sample 1 = Green
Sample 2 = Blue

A close match between the two tested samples. The use of ferro-fluid in the magnetic gap gives a well damped impedance peak at the resonance frequency, but at the same time gives the characteristic dual bump in the impedance commonly seen in some Seas tweeters.





Frequency measurement conditions:

The tweeter is measured flush-mounted on a baffle with the following conditions:

Baffle size: (WxH): 24,8×35,8cm

Driver position: Mounted on center-line with driver unit center 8,7cm from the top of the baffle.

Mic position: 1m distance, on tweeter-axis.

Smoothing: No smoothing applied.


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

Virtually the same frequency response between the two samples. Between 1.5-4kHz the baffle diffraction is noticed as dips and peaks in the frequency response. This is reduced in the off-axis measurements. The tweeter has a rising top-end frequency response from 10kHz. Very extended frequency response in both ends.

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

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



 Measurement setup:

  •         Tweeter near-field measurement at 10cm
  •          Frequency Range Tweeter: 500-10000Hz
  •          Baffle size WxH: 24,8×35,8cm


The distortion measurements are done in near-field and the amplifier output level was adjusted for each driver so that the fundamental is 85dB and 90dB at 1m. This setting simulates normal to medium-high listening levels.

85dB @ 1m (click on picture to zoom)

Left = Sample 1

Right = Sample 2

90dB @ 1m (click on picture to zoom)

Left = Sample 1

Right = Sample 2


The odd-order harmonics are very low throughout the tweeters usable frequency range. The harmless 2nd order harmonics is a bit elevated compared to the odd-order harmonics.

To sum up, this is a very affordable low distortion tweeter and it can be used as low as 1.5-2kHz with an appropriate filter.