Any interest in Stax Lambda-series, Sennheiser HE-series & Grado HP-Series specs?

Hi everyone,

I've gathered a lot of technical specifications & info on Stax Lambda-series | Sennheiser HE-series | Grado HP-series

Here's some interesting technical specifications and observations

- Michael



Stax Semi-Panoramic Earspeakers
--------------------------------

It was during the years when Stax Industries, Ltd. was run by the the
president/owner Naotake Hayashi and later along with his son Takeshi Hayashi
that Stax developed their Semi-panoramic Earspeakers. After four years of
development the huge Stax SR-Sigma series was released in 1977 followed by
the SR-Lambda series in 1979.

During the 1980s Stax developed the Professional Series, originally developed
for Daimler Benz, the german car manufacturer.

By the end of 1995 Stax Industries, Ltd. along with its American subsidiary,
Stax Kogyo ceased business operations due to a disagreement between owners of
the firm and its employees. However, around 1996 some engineers from the old
company formed a new company, Stax Limited in Saitama, Japan.

Old Company: Stax Industries Ltd.,Tokyo Japan (1938-1996)
New Company: Stax Limited, Saitama Japan (1996-Present)

Sigma Series, Panoramic-sound Earspeakers (1977-1994)
-----------------------------------------------------
Name: SR-Sigma (-, Pro)
Transducer shape: Elliptical/Oval
Electrode type: Perforated metal plate
Diaphragm thickness (micron): High polymer film, 2, 1.5 (Pro)
Electrode gap: 0.3 mm (230 V), 0.5 mm (580 V)
Bias Voltage: 230 V, 580 V (Pro)
Frequency Response: 30-35 kHz, 25-38 kHz (Pro)
Signal cord: 6-pin OFC, 5-pin PC-OCC (Pro)


Lambda Series, Semi-panoramic Sound Earspeakers (1979-Present)
--------------------------------------------------------------
Name: SR-Lambda (-,Pro,Signature), Lambda Nova (Basic,Classic,Signature), Numerical Series (SR-202,SR-303,SR-404)
Transducer shape: Elliptical/Oval
Electrode type: Perforated metal plate
Diaphragm thickness (micron): High polymer film, 2 (230 V), 1.5 (Pro), 1 (Sig), 1.35 (Nova/Numerical Series)
Electrode gap: 0.3 mm (230 V), 0.5 mm (580 V)
Bias Voltage: 230 V, 580 V (Pro/Signature/Nova/Numerical Series)
Frequency Response: 8-35 kHz, 8-50 kHz (Pro), 8-80 kHz (Sig), 7-41 kHz (Nova/Numerical Series)
Signal cord: 6-pin OFC (230 V), 5-pin OFC/PC-OCC/Wide PC-OCC (580 V)
Notes: The Nova-series and later have improved stator design

Omega Limited Series (1993-1994)
--------------------------------
Name: Stax SR-Omega
Transducer shape: Circular
Electrode Type: Gold-plated copper mesh
Diaphragm thickness: High polymer film, 1.5 micron
Electrode gap: 0.5 mm
Bias Voltage: 580 V
Frequency Response: 6-41 kHz
Signal cord: Wide format high quality LC PC-OCC, 5-pin
Notes: Stax developed the Omega-series as a direct competitor to Sennheiser's Orpheus Series. Limited Edition. 300+ sets have been reported being produced (more likely around 350+). 50% larger diaphragms than Lambda Series, electrode mesh structure instead of flat perforated metal plates


SR-007 Series (1998-Present)
----------------------------
Name: SR-007 (Omega II)
Transducer shape: Circular
Electrode Type: Gold-plated perforated metal plate
Diaphragm thickness: High polymer film, 1.35 micron
Electrode gap: 0.5 mm
Bias Voltage: 580 V
Frequency Response: 6-41 kHz
Signal cord: Wide format high quality LC PC-OCC, 5-pin
Notes: Less (and smaller) holes than Lambda Series


Some interesting Notes about Sennheisers HE Series Headphones
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Sennheiser HE Series
--------------------
Name: Sennheiser HE-60
Transducer shape: Oval-shaped
Electrode Type: Gold-plated resin polymer with hexagonal perforations
Diaphragm thickness: Gold-plated polymer foil, 1 micron
Electrode gap: ? (probably ~0.5 mm)
Bias Voltage: 540 V
Frequency Response: 12-65 kHz (-10dB)
Signal cord: OFC copper, 6-pin
Notes: 260g, 105g lighter than the HE-90s due to the use of plastic material in the earcup design.

Name: Sennheiser HE-90
Transducer shape: Oval-shaped
Electrode Type: Gold-plated crystal glass with hexagonal perforations
Diaphragm thickness: Gold-plated polymer foil, 1 micron
Electrode gap: ? (probably ~0.5 mm)
Bias Voltage: 500 V
Frequency Response: 7-100 kHz (-10dB)
Signal cord: OFC copper, 5-pin
Notes: Sennheiser released the Orpheus-series as a statement to show that they - just as well as Stax - could develop and manufacture high-end electrostatics. Limited Edition. Some 300 sets have been made. 365g, Earcups are made of thin beachwood-veneer which has been hand-polished. The diaphragm has been stretched under stroboscopic lighting to ensure uniform movement, then "aged" to ensure correct tension. The headband is completely covered in leather.


Grado HP-1000 Signature Series Observations
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Grado HP-1000 Signature Series Drivers
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Trasducer type: dynamic
Operating Principle: Open Air
Frequency Response: 18-24 kHz
Nominal impedance: 40 ohms
Drivers matched: 0.05 dB (HP-3 drivers are described as "not matched as closely")
Notes: The UHPLC used in the voice-coils of the HP-1000 drivers was also used in the connecting cables. I've read that the factory-equipped Ultra-Wide Bandwidth Grados also used this cord in the voice-coils. This seem to indicate that there may have been as much as three types of drivers (one for every type of signal cord). Some people have stated that there are drivers with inscriptions on the back (i.e. "Joseph Grado Signature Products") and some without any inscriptions. The Grado SR-200 headphones use the same drivers as the HP-1000 Signature Series.

Grado HP-1000 Signature Series Aluminium Earcups
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I've noticed three types of finishes, which I have divided into three series:

1st Series: matte surface machined aluminium alloy, flat metal mesh
notes: The earcups don't appear as reflective as the later series

2nd Series: shiny surface machined aluminium alloy, flat metal mesh
notes: Lettering seems to shine a little bit brighter than the earlier series. The surface on which the lettering is placed seems a tiny bit more narrow than the previous matte series.

3rd Series: shiny surface machined aluminium alloy, domed metal mesh
notes: Domed metal mesh appears matte, otherwise similar to 2nd series.

Grado HP-1000 Signature Series Signal Cord
------------------------------------------
1st generation: Unsigned
reviewed as: dark, bass firm, treble roll-off

2nd generation: Joesph Grado Signature Ultra-Wide Bandwidth Reference Cable ->
reviewed as: light, bass subdued, treble extended (reviewed in comparison with the "unsigned" cable)
notes:developed by Joe Grado as a response to the alleged treble roll-off of the unsigned cable and offered as an upgrade.

3rd generation: Grado Signature Laboratory Standard Audio Cable
reviewed as: Sufficient bass and extended highs in comparison with the earlier cables
notes: developed by Joe Grado through the accumulated experiences/responses of the two earlier cables to perform as neutral as possible.

Okay, I'll edit the thread title and post the info on the phones :-)

Enjoy...

Well, I think I have references to most of the stuff. Of course, there may be one or two things, that I only recall reading somewhere the last 10 years.

EG. I seem to recall reading somewhere that the electrodes/stators in Sennheiser HE-series had hexagonal (honeycomb) perforations. But I cannot remember the exact reference. So, It would be nice if someone with a pair of HE-60s or HE-90s would take a closer look at the holes in the electrodes.

It would be nice, if there was a website with all this sort of info on headphones :-)

- Michael

It's a unique feature of the HE-series. Keep in mind the difference between the HE-60 and the HE-90.

HE-60 Electrode Type: Gold-plated resin polymer
HE-90 Electrode Type: Gold-plated crystal glass

Just to clarify about the Sennheiser honeycomb structure.

The outer honycomb structure is just a protective grille. The inner honeycomb structure is the actual electrode/stator.