The next headphones were inspired by a friend constantly whining about his shitty headset yet not willing to spend some money to get actual good sound. With his birthday on the horizon I thought “oh well, still have a pair of spare drivers and pads lets see what we can achieve with the 3D printer”.
Since that would make a good “community” headphone i thought i’d do my best to build them with of the shelve parts.
And this is what ive come up with:
Meet the “Jalter”
As you can see they are very much open backed and kept simple but fairly elegant in design.
Its a neutral with a slight V tonality with good spaciality. It weighs 308g at this point and i can wear it for hours with no issues.
The off the shelve parts are:
A pair of Tymphany HPD-50N25PR00-32 which you know from the previous headphone aswell as the Borealis. They often are sold out but as of writing this are in stock at DigiKey
Next a Beyerdynamic spring steel. Just go to their website, on the bottom to Spare Parts and you can choose between the high pressure or low pressure variant originating from the “Pro” or “Edition” variants from the 880 for example. For me the low pressure is ideal but your mileage may vary.
Then a pair of 3.5mm Sockets. I used the literally first result from AliExpress for 2 bucks for this design. They rattle a bit with no cable inserted but work just fine otherwise.
For the comfort Strap I use about 22cm of leather but you can use whatever width and material that you want for it
You will also need some screws. To attach the headband, the baffle and fasten the yolks to the rods and into the chassis I use M3x10 and M3x6 Wood screws. Use the short ones on the headband blocks as to not peirce the material. The driver gets clamped with M3x12mm countersunk metal metric screws and the corresponding m3 nuts. For the headband you also need m3x8mm countersunk screws. You also need a little bit of wire to solder to the sockets and the driver.
For Tuning some felt and paper towels or whatever floats your boat.
Lastly the pads I landed on are Brainwavs XL Hybrids. They seem to give the best frequency response. But you can of course choose other pads. 105mm is minimum and can be too tight to fit but 110mm or more should fit just fine.
The Printed Parts:
The housing consinst of the structural Outer Housing which holds the Arc and the Socket. The Baffle which holds the driver screws directly into it aswell. Through the grid which keeps your fingers out of the driver and the baffle yuu screw into the nuts set into the clamp. This holds the driver really tightly. Then you screw the keyed end of the rod through the Arc with another wood screw. Not shown here are the “blocks” that hold the spring steel and the comfort strap aswell as the grill on the outside but that is just jammed in the hole and held with some Pattafix. On the blocks the Spring steel gets screwed down with some m3x8 metric screws and the leather strap uses the shorter wood screws. The middle hole is to optionally use a m2,5 screw to fix the Rods which is not necessary in my experience.
https://www.thingiverse.com/thing:5482763
As you saw in the Picture I only modeled the right side. For the left side mirror the parts in the slicer. The rods and the Blocks are symetrical so just print them twice
On thingiverse I also wrote short instructions how to print what.
The Assembly
Fairly Straight forward. Clean the 3D Parts from the support and check for fitment. The driver should just fit into the baffle and the clamp and the rod should just fit into the blocks. If it doesnt first drill out the block with a 6mm drill. If it still doesnt fit print the rod again a bit smaller, maybe 98% scale. It should slide with friction. It will loosen over time and usage a bit.
Then insert the Headphone socket and solder the wires to it. I like to route it around the housing to end at the top. Take the baffle and lay it on some felt or fabric with the convex side. Cut out the driver hole and cut around the perimeter. The thickness of this fabric is a necessary tuning decision I will talk more about later. With the tuning fabric cut out, slot the driver in the baffle, put the fabric around it and push the clamp on the driver taking care not to poke the diaphragm. Now take the Grid and the m3 screws. Use the 4 holes with no bevel on them and screw the Grid - Baffle - Clamp sandwich together with the nuts to secure the driver and the tuning fabric in place. Now add the other 4 screws for good measure. You can now screw the baffle with the wood screws onto the outer housing again clamping the tuning fabric in between. Now solder the wires onto the driver. You can also use an interconnect beween the driver and the socket to make it easier to change things up.
No try to stick the rod into the arcs hole. The rod should be angled away from the portrusion on the arc. This can be too tight to fit. In that case just carefully cut the keying on the rod down until it somewhat fits. With a wood screw screw it down through the arc until it feels really solid. Now you can push the Arc into the housing making sure its the right side. It should take a bit of force but once in turn fairly well. Now you can screw another wood screw into the sides to keep the hooks from depressing, keeping the arc fixed solidly inplace.
Lastly the Headband part itself. Shove the spring steel carefully into the slots on the front until the hole line up and the use a 6-8mm m3 screw with pressure to fasten it. Cut a roughly 22cm strip of whatever you want as a comfort strap and just thread a wood screw directly through it into the blocks holes.
Add the pads and after inserting the rods into the blocks the headphones are basically done. The extra holes on the end of the rods can be used to keep them from ever sliding out on their own but arent necessary.
The Tuning
As this is an DIY headphone I highly want to encourage you to try stuff for yourself. And since the stuff and way I used them are very hard to exactly reproduce its easier for me to just give you intructions on how to tune it and what things do.
The goal is a mixture of reflectivity control aswell as finding the “correct” amount of seal in the chamber. The Tymphany drivers react strongly to the seal of the chamber as shown in the previous project. So you dont want to just seal it completely (so either open pads or more closed pads and open housing).
What i used is some medium thick felt and some paper towel. The felt by itself was already pretty ok, giving some seal so that the bass was essentially linear until a slight rolloff in the subbass, but i like a little more sauce in there. So the paper towel again is used to seal it up a bit more. You can of course achieve this with another fabric altogether thats just more solid than the felt i used. Sealing the complete lower portion was too much in my case but adding the slits there gave the bass a very tastefull boost of maybe 2 dB. In my experience I also was able to reduce a bumb in the upper mids by putting the paper inside instead of outside, probably due to its reflectivity so maybe try that aswell and look what works best for you. Also you can try to add some front or rear dampening but I personally like to keep the driver as “nude” as it gets and just change the environment. But you aint me so do whatever you feel is correct.
Measurements
As per usual i like to follow up with some measurements to show what it does. The first graph will again be made with my janky DIY setup with a surroud receiver mic and a plastic printed Pinnae. This is NOT a standard and should NOT be compared outside of what I show. I had the opportunity to measure my stuff with another rig that has IEC couplers for a bit more accuracy which I will show after my own.
The Jalters are shown in green, the Sundara in blue and the previous Tymphany build in red. You can see A slight boost in the bass followed by very smooth mids. Compared to the Sundara we have a slight bump at 2-3kHz with a drop at 4.5kHz. The big spike at 7kHz is a lot less prominent in a sine sweep than it seems in the graph. Lastly one could argue for similar upper treble levels but this is so far beyond the point where it is accurate that it could just be measurement error.
If we compare it to the previous Tymphany headphone we can see that we have more smoother mids from 500Hz - 3kHz, slightly less bass and more treble. This checks out with listening with the Jalter being very neutral in general and very clear to my ears. Due to the similar angled driver design spaciousness is again excellent in my opinion.
Lastly something of interest in my opinion is distortion. Due to the very open and undampaned nature of the driver we see rising distiortion in the subbass. I tried to replicate the levels with my Sundara which is a lot cleaner in those regards. My finding was that the second harmonics that I see with the jalter up to 50ish Hz just give bass a thicker tone which i thoroughly enjoy. Note that a more closed chamber with the resulting more bass level will also dampen the driver and reduce distortion a bit. So keep that relation in mind.
A few final Points
This is my personal design which you may print, modify and use for personal non commercial use. I am no professional CAD or Acoustic designer so all parts can be a little rough and/or non optimal but as a DIY project I encourage people to try things out for themselves and use this works as a starting point that works pretty well.
If somethings was unclear or if you have any suggestions please feel free to ask/post. Since it is rather late at night at this point things can be a little jumpy and duplicates here and there.
Lastly there is already another 'phone in the pipeline a bit more exotic 
