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Drive units

The woofer used in this system is the SEAS L18RNX/P.

L18RNX/P is a 6,5” High Fidelity woofer with an injection moulded metal chassis, intended for bass reflex and transmission line designs.

Stiff, yet light aluminum cone and low loss rubber surround show no sign of the familiar 500-1500 Hz cone edge resonance and distortion assosiated with soft cones.

Large magnet system gives good transient response, and the bumped back plate together with the very long, and light weight copper clad aluminum voice coil allow for extreme coil excursion with low distortion.

Extremely stiff and stable injection moulded metal basket, keeps the critical components in perfect alignment.

Large windows in the basket both above and below the spider reduce sound reflection, air flow noise and cavity resonance to a minimum.

The tweeter is the SEAS 27TBFC/G or 27TDFC.

27TBFC/G is a High Definition metal dome tweeter with a wide, soft polymer surround and a rear chamber.

Aluminium/magnesium alloy diaphragm with pistonic behaviour throughout the audible frequency range, resulting in a good dispersion also above 10kHz.

A Hexagrid protects the diaphragm, and supports a phase plate which compensates for a slight axial roll off towards 20 kHz.

Sonomax surround for low resonance and excellent mechanical linearity.

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.

Precision moulded chassis from glass fibre reinforced plastic, and its front design offers optimum radiation conditions.

27TDFC is a High Definition precoated fabric dome tweeter with a wide, soft polymer surround and a rear chamber.

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

Sonomax surround for low resonance and excellent mechanical linearity.

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.

The chassis is precision moulded from glass fibre reinforced plastic, and its front design offers optimum radiation conditions.

The Enclosure

This system uses bass-reflex with a net volume of 15.4 litres, and with a port tuning frequency of 49 Hz. It should be made from high quality MDF (medium density fibreboard). It is important that the cabinet sides are accurately cut, so they may be precisely joined together. Internal bracing and damping of structural resonances of the cabinet walls is also recommended. Details are provided in the cabinet drawing.

The Crossover

The crossover network is a 1st and 2nd order parallel network. High quality components should be used to obtain an optimal result. Air core inductors with low DC resistance and high quality film capacitors are recommended. The crossover frequency is 2.3 kHz, and only a slight attenuation of the tweeter has been necessary to match the woofer sensitivity. Please see the crossover schematic for complete details. For highest reliability, we recommend you solder all connections within the cabinet; both at the crossover network and at the driver terminals.

Measurements

Measurements are not provided. Third party measurements are welcomed.






P.S.

1. Because of the sheet limit, the drawings have been simplified, so only the positions of the speaker
units' mounting holes are drawn. As for the mounting and trepanation, please refer to the dimensional
drawing of the speaker units.

2. DIYers can decide on their own the mounting position and trepanation according to the junction board
or binding post they use.

3. The enclosure is built of MDF. All the boards are 18mm thick except marked in the drawing.

4. It is recommended that the crossover network should be installed outside the enclosure.






L1:  SOLEN S16   0.82mH
L2:  SOLEN S16   0.75mH
L3:  SOLEN S16   1.2  mH

R1   4.7    Ω／10W
R2   3.3    Ω／10W
R3   6.8    Ω／10W
R4   6.8    Ω／10W
R5:   2       Ω／10W   ( If  H1212 is used )
           0.47  Ω／10W   ( If  H1189 is used )

C1:  11     μF
C2:  11     μF
C3:  3.3    μF
C4:  0.47  μF

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