The Third one will be a multiparter since I am still modifying it.
For this the inspiration was simply an inexpensive Hifiman Eggshape Pad on Aliexpress. I bought the pads and built the rest around that.
The drivers are the Peerless by Tymphany HPD-50N25PR00-32 which are as far as I know used in the Borealis and some Kennerton Headphones. I bought a few sets to also use in a future second closed back project.
The Physical
I again began with the “cups”. I used a piece of nice and thick plywood where i traced the outline of the pads on. I then cut the outside with a bandsaw and screwed the piece down towards a donor piece of wood. With a hand router and a concave curved bit I milled the outer profile. After then cutting a “lung profile” inside the piece with an electric jigsaw. With a convex curved bit the inner part got milled. This gave me a fairly reduced profile to reduce weight and give me room for modding.
For the grills I used the same honeycomb aluminium mesh from my ADX5000 project. I then also drilled the holes for the headband and a angled hole for the 3.5mm plugs on each side. After that I again gave the wood a few passes with wood oil to get the woodgrain out.
The innards I designed fully in 3D and then printed. In this post I will just show the Status Quo while I am still optimizing the design.
It consists of 3 parts. The first part is a flat piece with the correct holes for the cups and 8 3mm holes around the driver. The second big part is the backpiece that clamps the driver to the front piece. This also clamps the fabric down I will talk about later. The last part is a simple grill to keep me from sticking my fingers into the bare driver even more often. Due to the flat main plate the driver sits fairly close to the ear. The headband is the same design as the one for my Biocell closed back, more precisely the scraps from the prototype for that headband. With the new printed blocks it also holds the yolks very firmly. Since the pads are now slightly bigger or rather bulge out a bit the cups are a bit hard to tilt inwards.
The tuning
For tuning I ended here with a 3 part solution for now. Firstly I am using the full sheepskin pads with inner perforations. I shortly used the hybrid pads but didnt find them to fix the issue I was looking at, but I will revisit them with later designs for sure. Secondly I experimented with the backside venting or rather blocking of the openings from the “plate”. Here I am again using the fairly thin cotton fabric screwed down into the cup and between the plate and the back plastic. The densitiy does strongly impact all frequencys under about 250hz. After adding further fairly dense foams squished in the back openings I ended on a fairly linear bass response.
The foam does only impact the bass slightly and also did a slight change to the treble which is honestly not really audible to me but is measureble.
The pads are shipped with 3M adhesive but since I was not super happy with my results for the moment I only attached the pads with a strip of electrical tape. But random note be careful with that since the tape is appearantly sometimes strong enough to rip parts out of the leather. So no ripping it off every 20 minutes.
The Tuning I got sounds warm and thick to me. Not really what i was looking for. While measurements I will show later indicate that the bass and lower midrange are linear with just some dips in the upper mids it sounds as if after 2khz there are just 5+dB missing for what I usually enjoy. But that also leads to a sound that is nonfatiguing. It reminds me of my HD58X. Comfortable and listenable to hours but just missing in stage, clarity and just simply a wow factor.
With that being said lets see some measurements
Measurements
Here it is again with my dodgy rig compared to my Sundara. It has to be said that the measurements sometimes varied strongly but this is a result I got regularly and most reapeatably but again just with another grain of salt. As can be seen the bass extrends really well for a open back. The lack of air may be responsible for some of the perceived “lack” in clarity. Also just the imbalances in the upper mids / lower treble just give vocals a bit of a “dull shine” or rather just veiled with sudden moments of a kind of glare.
Its a bit hard to describe but in general I am just not content with my results and am currently printing new baffles for more air and space between the driver and ear. In very brief and dirty measurements the added space seemed to even out the treble. Additionally I hope to lower the lower mids a bit to get more distinct bass and leaner vocals which I simply prefer.