Seas H1397-04 (27TAFNC/D) 1″ Aluminum Dome Tweeter

Up for test is the Seas H1397 tweeter.  A commonly used tweeter in the car audio world and home audio world due to its compact size (outer diameter is only 53mm; approximately 2 inches) and relatively low cost.  Manufacturer’s information can be found here.

IMG_5084 IMG_5083 IMG_5085


Thiele-Small Parameters and Impedance

Electrical Parameters
Re 3.03 Ohm electrical voice coil resistance at DC
Krm 0.001 Ohm WRIGHT inductance model
Erm 0.53 WRIGHT inductance model
Kxm 0.0002 Ohm WRIGHT inductance model
Exm 0.83 WRIGHT inductance model
Cmes 246 µF electrical capacitance representing moving mass
Lces 0.07 mH electrical inductance representing driver compliance
Res 1.05 Ohm resistance due to mechanical losses
fs 1212.6 Hz driver resonance frequency
Loss factors
Qtp 1.479 total Q-factor considering all losses
Qms 1.974 mechanical Q-factor of driver in free air considering Rms only
Qes 5.68 electrical Q-factor of driver in free air considering Re only
Qts 1.465 total Q-factor considering Re and Rms only
Sd 7.5 cm² diaphragm area

Magnitude of electric impedance Z(f)


Frequency Response

2.83v/1m, Nearfield and farfield merged at 1300hz.

Seas H1397-04 0 30 60

Harmonic Distortion

Mic placed in the nearfield and measurements performed at an SPL equal to a farfield level of 90dB/1m.

Fundamental + Harmonic distortion components (Relative to 90dB1m) Harmonic distortion (Relative to 90dB1m)

Output increased to represent 96dB/1m.

Fundamental + Harmonic distortion components (Relative to 96dB1m) Harmonic distortion (Relative to 96dB1m)

Quick Analysis

The Fs isn’t terribly low and this can be misleading as most will shop by this spec only.  However, when viewing the other aspects of this driver it looks to be quite a value.  The response is (-)3dB from 0 degrees to 30 degrees at 10khz while down 10dB from 0 to 60 degrees. The frequency response has a rise on-axis but a smooth, flat 30 degree response averaging about 85dB at 2.83v/1m.  This means the tweeter may be better suited for an off-axis type install, however some seem to prefer a heightened top end.  Use your own judgement here and experiment with placement, depending on environment (home or car).

At high output, the HD is fairly low above 2khz, dominated by almost solely 2nd order distortion.  3rd order and subsequent odd order distortion components are at most 0.33% (3rd order; 2250hz) in the 96dB testing.  At a moderate output of 90dB/1m, the distortion is pretty much below 1% above 1.5khz with a rising trend above 5.5khz, but again comprised of 2nd order distortion.  It’s interesting to note the higher order distortion components essentially stay the same above 2khz as the output is increased while only 2nd order distortion rises.

Bottom line:

  • Small and very compact.
  • $42 price tag (as of this writing) is attractive.
  • Very nice off-axis performance, though you may not like the on-axis rise.
  • Well controlled high frequency dispersion.
  • Crossed at 2khz with a LR4 this driver should be able to provide some hearty output levels.

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