Orthodynamic Roundup
Feb 22, 2013 at 4:45 PM Post #21,182 of 27,203
Doing a listening comparison of the Unipolar and HP-50S now - as far as bass goes (in reference to the above), both phones do 50 and 40 Hz relatively close to the 1 kHz level, though the Unipolar more so, and only the Unipolar manages 30 Hz audibly when the overall volume is set to comfortable at 1 kHz.
 
Feb 23, 2013 at 9:44 PM Post #21,185 of 27,203
HOK open-backed, not forgetting duct tape.
 

 
 

 
The headband is that of a Pioneer SE-90D (a bit rare).
http://20cheaddatebase.web.fc2.com/pioneer/SE-90D.html has a picture of the headband's cup fork – it happens to be the sort of shape to hug the HOK's baffle just right on the backside. Not the most durable attachment there with the tape, but it doesn't seem to wobble too much anyway. Not sure how I'd attach the pads.
 
The sound needs +10 dB of EQ in the bass (that's HOK #1 for you), but apart from that, it's pretty decent with the pads just pressing against the baffle. A wide, relatively natural soundstage, though not very deep. I'll do some measurements later to see if anything improved over stock or whether everything got worse.
 
Feb 24, 2013 at 8:21 AM Post #21,186 of 27,203
Quote:
Doing a listening comparison of the Unipolar and HP-50S now - as far as bass goes (in reference to the above), both phones do 50 and 40 Hz relatively close to the 1 kHz level, though the Unipolar more so, and only the Unipolar manages 30 Hz audibly when the overall volume is set to comfortable at 1 kHz.


there seem to be wide variations in the HP50 series: my HP50A bring the 30Hz with ease.
 
Feb 25, 2013 at 8:15 PM Post #21,191 of 27,203
Put the HOK drivers back into their cups. Stuffed the cups chock full of cotton, then added two discs of wool to the back of the driver just to increase the amount of stuff in the cup. They barely stay closed. Blu-tacked the rim of the baffle shut.
 

 
Not a big change overall compared to no cup at all, but the decay in the mids now measures very clean.
 
Also, as the plot kinda shows, the response starts going downhill below 1 kHz – the bass extension is literally over before it began.
 
The curious bit is that the soundstage is still decent. I don't have the back disc in, so in essence the cups are open, but there's a wall of cotton there.
 
Feb 25, 2013 at 9:40 PM Post #21,192 of 27,203
Playing around with the HE-6, a bit of twaron angel hair in front of the driver made a huge difference, moreso than anything behind the driver. Makes sense in retrospect, but sometimes it's easy to get caught up in thinking about how to stuff the cups (heh) that we forget about the front end.
 
Feb 25, 2013 at 11:04 PM Post #21,193 of 27,203
Now there's a novel idea.
No issues with it expanding into the diaphragm itself? I never bothered to remember how it's all set up in there from the pictures I've seen. 
 
Feb 26, 2013 at 12:04 AM Post #21,194 of 27,203
Nope, the front is protected by a grill and magnet assembly, though I do still have that nylon dust cover in front and a piece of felt (the twaron is sandwiched in between). I also regrilled the backside with something much more open, and took out the stock foam as well. The result is far less reflections/ringing. That combined with the angel hair in front and the J$ pads and the HE-6 is almost dark sounding in comparison now. It still has that delicious clarity and sharpness, but that upper edge is gone. Taking out the angel hair would give it a bit more bite, but that's into preferences again. 
 

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