A gift from the Gods? Seas presents mythological speakers

By Lars Mytting
05 Mar 1996

Introduction

Ok folks, here they are; fresh from the oven, the new Seas kits. Five of them uses Seas' top-of-the-line drivers, the Excel series. These five are designed by Murray Zeligman from USA, an independent consultant with over 25 years experience in design of speakers and amplifiers. The two other kits are designed "in house" at Seas; the Embla by Bjørn Børja, the Njord by Jon Paulsen. Four of the kits has been baptized with names from the old Norse mythology, three of them has not got any name yet. For these three, we have so far no information on how they will be marketed, or if there will come changes to them. The drawings and crossover schematics on these should therefore be regarded just as suggestions.

Who are these gods?
For those interested, the mythology department at The Speaker Building page presents a short introduction to relevant Norse:

Odin - The master of the gods, also god of poetry, sorcery and wisdom.
Embla - The first woman, the Norse equivalent to Eve.
Njord - God of the sea and of wealth, Frøy's father.
Froy - God of fertility and good crops. (A note: We assume that Seas has meant "Frøy", which is the real Norwegian name, but that they have omitted the "ø" for better anglo-computer-compatibility)

The Excel drivers
The Excel kits are based on three different woofers, in single and D'Appolito configurations. The T25-001 tweeter is used in Excel kits. Drivers used are:

• T25-001 1" tweeter, double magnet, silver wire voice coil.
  
• W14 CY-001 5" driver, magnesium cone, solid copper phase plug.
  
• W17 E-001 6.5" driver, glass fibre cone, solid copper phase plug.
  
• W17 E-002 6.5" driver, magnesium cone, solid copper phase plug.
  

The most remarkable with the woofers are the cone materials, which gives low distortion figures. Especially the magnesium drivers has remarkable low distortion compared to paper and polypropylene. The tweeter has very good off-axis response, at 30 degrees it is only 2db down at 13.000 hz.

The main challenge for the amateur speaker builder using Seas Excel drivers has been to get the crossover right. The problem for the glass fibre cone has been to attenuate the midrange correct, because the driver's rising sensitivity with increasing frequency. It has also a more uneven midrange response than the magnesium cone. The magnesium drivers has a extremely steep and narrow cone resonance peak at 5000 or 10.000 hz. This is easily attenuated with a LC circuit. The T25-001 tweeter has a slight rolloff from 4000 hz, which may be corrected by parallelling a capacitor over a series resistor.

The Excel series includes several other drivers. The 6.5" drivers are available with three magnet sizes, the W17E 001 and 002 being of medium size. Unfortunately (and unavoidable) the different W17 drivers has different frequency response, so the present crossovers is not fully compatible with the other Excel drivers. But, using the same crossover topology as presented here, and adjusting the values with computer simulation like Leap or Calsod, it should be easy to get optimal results using the other drivers.

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