4-day weekend, so I figured I'd finish these up so I can stop being distracted by the project. After about 16 hours over the last two days, out come my omega clones.
I decided that I should etch away that copper. I just did a standard toner transfer lining it up by eye. Upon typing up my last post, I realized it'd be correct within a millimeter or two, which is more than enough precision for this.
Next, I assembled the plastic mount for the earpad. This is made of 1/8" ABS as the rigid structure, with a 0.02" styrene spacer and a mounting loop of the same thickness. The slit allows for the earpad to easily rotate into place:
Diaphragm's were made by my typical method of hanging weights as I've discussed earlier.
Next, I cut a spray mask on a styrene sheet and airbrushed elvamide solution onto the mylar. The mask is to keep the elvamide off of the edges to prevent any leakage of charge. I really like the airbrush technique... hook it up to a compressor, spray uniformly, and in a couple minutes of work effectively perfectly matched coatings can be accomplished.
I used my crumpled mylar sweat screen design, since it seems to be completely acoustically transparent:
And, the final product:
I need to play with damping a bit, may need to add a felt sheet to the outside. But that's it pretty much.
Weighting in at 0.60lbs, they feel weightless compared to my previous builds (in fact they can be comfortably worn with the elastic head strap not present just pushing against the ears). Free air resonance is 75hz.
I'm not going to bother posting analysis graphs yet, since honestly I'm too tired to even think about analyzing them. I'm going to play with damping first anyways since there is some distortion in the 300-600hz range as is typically seen in fully undamped headphones.
As for the sound, they are fantastic. noticeably better than my previous rectangular builds, I imagine largely due to the quality earpads (a purchase that I most certainly do not regret!) and the large driver area.
This will probably be the last pair of headphones I make in the foreseeable future (right... like that'll happen).