[Soaa-]

My dad had these since forever, but I can't find any information on them online, at all.
 
Here's a pic:
 

 
As far as their sound goes, they're a bit warm and aren't the most detailed. Bass extension is pretty good; highs are a bit recessed but fairly sharp nonetheless. Imaging isn't so good for some reason.
 
Anyone know anything about these headphones?

 

[smeggy]

They look like an OEM from beyerdynamic. Piezo was probably a brand that went into oblivion in the 80s

 

[wualta]

The headband and yoke also look a little like the ones on the Pioneer SE-700 piezoelectric. This is an interesting find whether they operate on the piezo principle or not. If you ever get the urge to disassemble them, have a camera ready. 

 

[DefectiveAudioComponent]

Does it say DSR-7 on the other side?
 
The japanese site says PIEZO/AZDEN had a DSR-7 model that look exactly like yours:
(Still, it would be cool if you had a look at the driver just to be sure...)
 
Quote: babelfish translation from the japanese site

* Price ¥8,500
* Type dynamic type opening air type
* Diaphragm
* Impedance 200Ω　
* Playback frequency zone 20-20,000Hz
* Allowance input 200mW
* Sensitivity 98dB/mW
* Cord/code 2.5m
* Weight 200g
* Around sale 1976
* Around sale end 1983

 

[wualta]

Yep, only way to be sure is to peek at the diaphragm. If they're piezo, you'll see a flat piece of dark-silver plastic film. But I'm afraid it's a conventional dynamic.

 

[Soaa-]

Man I'm tempted to tear them down now but they aren't mine and I'm not sure my dad would like that.
 
It does say DSR-7 on both sides. Defective, mind sharing the link to the Japanese site?

 

[JeckyllAndHyde]

here:
http://20cheaddatebase.web.fc2.com/AZDEN/DSR-7.html

 

[Soaa-]

Hah, these are indeed the same as what I have. Somehow they got rebranded Piezo.
 
Thanks for the find. It sheds a bit of light on the origins of these mystery cans.