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Janszen Model Z-20 Speaker Pair Vintage Circa 1978 - $100 (Red Wing)

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Janszen Model Z-20 Speaker Pair Vintage Circa 1978 1
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condition: salvage
make / manufacturer: Janszen
model name / number: Z-20
size / dimensions: 27-3/8" x 14-5/8'' x 15-7/8''

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Vintage 1978 to 1980 Janszen Z20 hybrid electrostatic loudspeaker pair with 12 inch woofers for salvage. New rubber surrounds ($36). Plastic wrap faux wood veneer is ok not totally perfect. E-stat panels have a bit of visible greenish copper oxide corrosion in a few places (please review pictures) yet all the insulated electrode wires (aka "stators") are intact. The panels test as functioning. Replaced old audio path electrolytic capacitors with high quality new MPT aka metallized polypropylene film capacitors (paid $62 for all those). Also, installed new 1N4007 rectifiers (diodes). The front grilles are in ok shape. One grille is missing the "JANSZEN MODEL - 20" badge / emblem in the front lower right corner. Manufactured by Electronic Industries, Inc. in Minneapolis, Minnesota on license. Included are paper baffles for inside the grill covers which had originally been attached to foam but that was deteriorated which I completely removed.

Ok so here is the bad news: These speakers had both worked when I first got them, then audio from one speaker's electrostatics was barely audible. I replaced all the above parts correctly (to the best of my knowledge and had two electronics experts check my work verifying the diodes are in circuit with the correct polarity) and presently the fuse in either speaker blows every time I plug them in. I was told it could be that the 1N4007 rated at 1000 volts @ 1 amp is not quite high enough or that the step up transformers (the primary or secondary windings have NOT tested as shorting or open in either crossover) are somehow creating an arc inside where then the fuse blows. I'm stumped and don't really wish to proceed to replace the expensive high quality audio grade step up transformers to try to chase the problem (I found one possible source via https://www.sowter.co.uk for $$$ or someone posted online of using the transformers from a Fi-Shock model EAC10A-FS or SS-525CS electric fence energizer for around $50 each: "low-impedance, continuous-voltage electric fence energizer that produced a low-current voltage of about 1100vac" https://audiokarma.org/forums/index.php?threads/my-janszen-z900-rebuild-thread-please-chime-in-pics.704261/#google_vignette ). I originally got these for free. I simply want to recoup ome of the money I've spent to try and save them reimbursed to me which reflects the above asking price otherwise I'll part everything out (throwing the cabinets away) and sell that stuff on eBay. Thought I'd try to find someone with much more expertise before I do that.

Please note: the last four images show the cross over with the new rectifiers, the new capacitors installed, the old board as it was originally (showing the original rectifiers) and a cross over schematic that I believe is exactly the same however it is stated as a model Z-2.

Info is scarce for this specific model. Here is specifications on a Janszen Z-412 which was somewhat similar (an earlier Z series from the mid 70s) yet had four e-stat panels per speaker so likely had a better high frequency range:

Frequency Response ± 3 dB 33 Hz-20 kHz, ± 6 dB 26 Hz-30 kHz
Minimum RMS Power Required 20 Watts
Maximum RMS Power Handling 100 Watts
LOW FREQUENCY TRANSDUCER CHARACTERISTICS
Type Dynamic, Acoustic Suspension
Cone Diameter 12 In. (305 mm)
Voice Coil Diameter 2 In. (50.8 mm)
Total System Resonance 43 Hz
Q Factor (Damping Characteristic) 1.1
Crossover Configuration Mass Loaded
Crossover Point (12 dB/ octave) 1.800 Hz
Impedance (lowest value) 4.6 ohms
HIGH FREQUENCY TRANSDUCER CHARACTERISTICS
Type Electrostatic Array, 4 Element
Radiating Area 64 sq. in. (413 cm2)
Air Displacernent Capabilities (P.P) .025 in (.635 mm)
Polarization Voltage 1.100 Vdc
Distortion T.H.D.(over operating range) 0.5%
Crossover Point (12 dB/octave) .800 Hz
Dispersion (minmum at 20.000 Hz) 50° Horizontal and vertical
MECHANICAL AND ELECTRICAL SPECIFICATIONS
Cabinet Size (H x W x D) 27.125 x 14.5'' x 11.75''
(689mm x 368mm x 298mm)
Shrpping Weight 44 lbs ( 19.9 kilo)
Electric Power Requirerments 100-240 VAC/50/60 Hz, 2 Watts

post id: 7845758113

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