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Circumaural Yamaha HP-1 Build Thread

Back to work on the headphones. The first band failed. The curve was too tight, the glue was too brittle & the form was too soft. The band had a bow across it's width. So I'm making a proper 2 sided MDF form this go round. I will be using West Systems toughened marine epoxy. It's what bow makers use so it should do the trick.
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Wow, You are doing some really nice and intricate work. West Systems is really great stuff. Interesting project. Good luck and please keep us updated!
 
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Tonight I completed the rough ear cup mounting blocks. The long cap screws provide a good range of adjustment. More so when the blocks are cut down to size and shaped. They are held in position by the 6-32 thumbscrews in threaded inserts. I'm pretty happy with the way they turned out so far.
 
Very cool project. I'll be waiting for your impressions. Was the driver choice (Yamaha) based on past experience?
 
Thanks westend. Yes, I have a pair of Yamaha HP-1s I bought new in '76. I listen to them every day at work. I really like their sound. The recent resurgence of orthodynamic, aka planar magnetic, headphones has peaked my curiosity about how they would sound as more comfortable over the ear cans. Because of my project assignment across the country from my home and wood shop I needed a small scale, apartment-friendly creative outlet for when I have time on my hands. Next up I have to work out the padding and then I can do the trimming and fitting to my melon.
 
Thanks it was a fun project, learned a lot along the way about doing without my usual arsenal of machines. A few thoughts and impressions at the end of this journey:

Comfort: The conversion to over the ear was a 100% success. I'm looking forward to longer listening sessions with increased comfort. Mimicking the original Yamaha ball joint and leather sling paid off. Actually my steel ball and Delrin ball joints are better than the original. A million times stronger and totally quiet, both drawbacks of the originals. The finished weight came in at 15.9 oz vs. 9.4 oz for my modified HP-1's. Heavier and bulkier to be sure, but that comes with the circumaural territory.

SQ: My design provided much more breathing room for these drivers than Yamaha's. As it turned out that yielded mixed results. More room in front of the baffle sounded terribly muddied and garbled. I've read of flabby bass just from using thicker than standard ear cushions. This was way past that. So conventional wisdom was upheld - these drivers sound best close to your ears. The ear caps and one spacer I made for in front of the driver ended up in the parts box.
The extra room behind the baffle once properly dampened with 1 layer of standard weight craft store felt greatly improved the bass impact and depth. Nice punch, no flab and more space to the soundstage while maintaining the Yamaha orthodynamic "air" I've enjoyed all these years. I also added a 3/8" treble dot to very good effect as well. I hadn't tried this on my modified HP-1's, but may.

The stacked or modular approach I took really made dialing these in pretty convenient. I must have taken these apart and reassembled them a dozen times since Friday to change configurations and play with different dampning schemes. Not that I would have settled, but it just condensed the process. Thanks for watching.

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Since my last post I've been trying different damping approaches. I gotta say that if these weren't so easy to open up I'd have settled already. A recent post in a thread on transplanting the 45mm version of these drivers got me thinking to go back to basics on damping these. So tonight I went to a felt layer backed with foam. The bass is reduced a touch, but tighter. Time will tell if the occasional bass distortion during decay is gone for good. I also adjusted the headband tension by shaving some thickness off of it. I took 2 of the 5 plys off, but that was too much so I laminated 1 back on. 4 feels about right.
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