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DIY Open Back Headphone Project?

jae

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Being in the market for a new headphone setup for the first time in over a decade, I've found myself auditioning many cans for dozens of hours, and both reading and watching tons of reviews and asking for suggestions from those who have stayed up-to-date with the latest offerings. I am leaning towards buying one of the Audeze or Mrspeakers headphones which I will pull the trigger on soon, but that's not what this thread is about.

I've noticed not only how expensive the upper echelon of headphones have become, but how it is becoming more commonplace to spend that much (which I am sure is correlated) even among those that aren't self-proclaimed audiophiles. Newer headphone technology definitely performs and sounds better in many ways, but headphones that aren't considered 'flagship' or near the top of the line can be well in the range of or over $1000-2000+ USD (ignoring more niche stuff like electrostatics etc), and I feel from my recent auditions that very few of them deserve to be priced as such. The Sennheiser 600-series were highly regarded headphones when they came out and still are to this day, and adjusted for inflation the HD650 would have cost about $700+ in 2020 which is interesting as I believe they still compete in many ways with headphones in that range, despite the fact that they can be had for a mere $200 from Sennheiser's partnership with Massdrop. In my search for an 'upgrade' of the HD650's that I've been using for almost 15 years, a lot of people have recommended to me a few cans from ZMF and more recently the Aurorus Borealis as dynamic headphones that have a somewhat similar sound yet perform better from a technical standpoint and have a more appealing FR, and I did like like their sound in the brief time I was able to hear them. I won't bother regurgitate the specs here, but they are easily found with a quick google search along with their praises and criticisms.

I was curious about the design of those cans and after doing some searching, it seems that in both cases they are a) using easily obtainable/mass produced drivers (Tymphany Peerless HPD-50N25PR00-32 in the case of the Borealis- I'm not 100% sure if some ZMF drivers are custom but I am fairly certain I've seen what looks like number of their models containing drivers that look like some of the better ones from Alibaba & other chinese sites) and b) they use a fairly minimalist baffle/dampening methods to tune these drivers to where they at least subjectively rival or surpass headphones like the HD600-series and HD800 with very little complexity in their design. Another $1000 headphone, the Kennerton Vali, uses the exact same driver as the Borealis. I have it under good authority from some of my connections there that there are a number of DIYers/'boutique'/handmade headphone makers that operate only in China are using these and similar drivers to make good sounding headphones that they sell for quite a bit. Interestingly some of these Chinese guys of which I speak also appear to sell some kind of planars modeled after Audeze/Hifiman (clones or factory extras?) and presumably sound good enough that they sell them for thousands. Honestly, I find things like hand-made wooden earcups, shipping, warranty, premium cables and water-proof carrying cases probably have given companies justification to charge double what they should for a pair of headphones.

Anyway, my conclusions from this are that I believe the Tymphany 50mm drivers and most likely some of the more premium aliexpress biocellulose/beryllium drivers can potentially be some DIY headphone 'gems' rivaling some nice headphones if given the right touch. Driver tuning is generally not an easy undertaking but I believe there's just something about these drivers that make them tune well and they could definitely be a key component in some kind of open source headphone baffle design. There's no need to reinvent the wheel with the remaining components, a hifiman or audeze headband/yoke assembly can cost $70-240 brand new or less if used, readily available earpads like those from Dekoni or ZMF cost $40-70 at most (and their number of options allow for further tuning), a high-quality cable/connectors can be made cheaply or bought new for $40-100 or even repurposed from another pair of headphones, and the drivers $20 a pair, although you may need a few to ensure a good matching. I definitely think it is in the realm of possibility to be able to make a comfortable headphone with premium parts and premium sound in the scope of a $200-500 DIY project, especially if the baffle design was 3d-printable or had easily machined components.

Thoughts? Opinions? Ideas?
 

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maverickronin

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I've never made a pair of headphone from scratch, but I have done quite a bit of modding in the past and it does take a fair bit of work to get good results. That said, if you have the time to spend it is a rewarding experience.

You'll also want to get MiniDSP EARS for ease of testing. Back when I was into modding I had custom flat plate coupler that held a Dayton omni measurement mic which worked, but was difficult to use. If I do get back into modding I'll get an EARS for the convenience.
 

A800

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jae

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As far as I can see the rim of the drivers in ZMF are basically fit to a TPU gasket to allow movement/cushioning on the driver, which is then friction fit to a wooden or maybe fiberboard baffle that is more or less a piece of wood with an appropriately sized hole/recess cut into it ('top-hat' shape). That is then screwed into the earcup assembly which is a cup fit with a metal grille. There's what appears to be an injection molded plastic screen screwed over the driver, and the baffle is further tuned with various vent holes drilled around the perimeter of the driver at specific locations. The amount and placement of holes vary depending on the model. A stainless steel mesh is just screwed over top, and the mesh's pore size varies between models/drivers.

The headphones do sound quite good overall but frankly there is nothing impressive about this construction at all to me, but what I am impressed with is the sound produced from the relatively simple design. Of course it did take time and resources for them to develop, but realistically the only non-trivial components of the design apart from the headband is the driver gasket, baffle cover, and grille, but who knows how much of the complexity of the cover/grille pattern actually contributes to the overall acoustics. Other than that, the wood can look attractive but I imagine using wood imparts a bit of variability and inconsistency to the frequency response between units or over different batches, and the fact there are screws biting directly into plastic and wood doesn't pose much for the durability/longevity over time


I rather like the design of the Aurorus cans (minus the headband...) for the sake of DIY inspiration, the assembly is made almost entirely of machined aluminium and appears to be just 3 or 4 simple components sandwiched together with machine screws. There is the 'ring' component (probably the most complex part) that has the mounting holes for the headband yoke on the outside and there is a portion at the bottom to house the mini-xlr connector which seems to just be friction fit/glued in? (Rean model # RT4MP it looks like). There are also 4 threaded holes to connect rest of the baffle which is just a sandwich of two relatively simple pieces also screwed together that contain the driver, although I didn't get a chance to see if there was any kind of gasket or plastic parts on the other side of the driver. There appears to be a mesh that covers the entire plane before the earpads. Reproducing something similar via 3d printing is definitely feasible, and it could be on the easier side to test different gauges of mesh or different fibre filters, or to drop in different geometries/designs of either of the two pieces of the baffle 'sandwich' without compromising the entire design.

I was thinking that if an off-the-shelf solution for an appropriate gasket couldn't be found, it would be possible to make a 3d-printed flexible bracket (TPU filament?) or even a 3d-printed mold to create a gasket out of silicone or similar materials.
 

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jae

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I've been looking at some of these:

HD800?
https://www.aliexpress.com/item/32957441597.html
https://www.aliexpress.com/item/33030747994.html

Interesting thread of a guy using HD800 drivers https://www.head-fi.org/threads/3d-printed-closed-headphones-with-hd800-driver.752877/page-11

Beryllium 64/500 Ohm drivers, wonder what cans these are used on
https://www.aliexpress.com/item/4000892041224.html
https://www.aliexpress.com/item/32950813973.html

Still trying to find the 300 Ohm paper drivers that look similar to the ones in the ZMF, but I lost the link
 

solderdude

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The drivers you mentioned aren't anywhere near the HD800 drivers at all.
 

Wolf

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OP- Since you mentioned using the 50mm Tymphany units, I've done just that...

I've been using a modded hybrid. My regular cans before were Sony MDR-V700DJ, but the leatherette on both the band and cushions rotted. I still have the guts hoping I can rejuvenate them down the road somehow.
This all started awhile ago (2 years now?), wanting to try the Pyle frames out as a sacrificial pair and utilize the Peerless 2"/50mm paper-coned driver units. Most are polyethylene, and that set these apart. The cheap Pyle frames allowed me to audition them and know that I liked what I heard.
https://www.parts-express.com/peerless-hpd-50n25pr00-32-2-headphone-driver-diaphragm--264-1510
The Pyle frames had issues with durability, and assembly inconsistencies that made them not a completely viable solution. Stock they were horrible.
https://www.parts-express.com/pyle-phpdj1-dj-turbo-headphones--248-4414
Then I sought out a better set of frames to continue with, and found the Talent SMH580 for dirt-cheap at the PE tent sale. I like the fit and feel of this 'AKG-esque' frame, and found it would be suitable and accepted 50mm drive units. Then- they were discontinued. Stock the bass was a little strong, and a little soft in the mids with polite treble.
https://www.parts-express.com/talent-smh580-semi-open-back-studio-headphones--233-350
And as you saw above if you clicked the link, PE also stopped carrying the Peerless drive units.
So, I was able to find replacements relatively easily/inexpensively....
Digikey is a source for Tymphany products, and they stock them:
https://www.digikey.com/en/products/detail/peerless-by-tymphany/HPD-50N25PR00-32/6211129
(The image on the item's online-page is not the correct image, and clicking the spec-sheet document shows the correct one.)
I was able to find a set of Stellar-Labs HP580 cans from Newark that looked very familiar, though a bit more red color is utilized:
https://www.newark.com/stellar-labs/ho-5960/full-size-dj-headphones/dp/52W8580#
AND- they were on sale (still are even) for about $18! Even the internals match that of the older Talent frames.
There are other options that are similar, like PreSonus HD7, available from Amazon:
https://www.amazon.com/PreSonus-HD7...6EPFW27QH87&psc=1&refRID=YPPA0K0RJ6EPFW27QH87
...but their cost is too high for sure! $18 is a lot better, added the cost of the Peerless units making the total about $40.
So- recap:
  • Stellar Labs HP580 or Talent SMH580 or PreSonus HD7 frames.
  • Peerless 50mm paper drive units, model HPD-50N25PR00-32
1- I gently removed the cushions from the frames.
2- I removed the 4 tiny screws from the face of the driver mount to gain access, and that is really all it takes to get in there.
3- Just snip the wires close to the elements to remove the whole assembly to work on it. I would leave about 0.25" wire on the driver to verify polarity before soldering later, as this ended up being the same in position on the Peerless units.
4- Use a small screw driver to work at the adhesive around the stock driver unit, and it will come free with very little elbow grease.
5- Remove the sticker that faces the listener's ear. It's a 'quadrant of a donut' shape, and says "Monitoring Headphone DYNAMIC" on it. All this does is reduce the midband when in place. If done right and you prefer them in place, you can reinstall them. I liked them better without.
6- Install electrical tape across 3 of the 6 open vents facing the listener. This will lower the tuning and tighten up the bass. I covered the 3 holes toward the rear of my head when worn because my Sony headphones' bass holes were towards the front of my head. I figured they knew why they did that.
7- Glue Peerless driver elements in with E6000 (about 2-3 hr cure time), around the entire perimeter of the driver for a good seal and to prevent rattles.
8- Place batting in the cups. I used about 4" square, 1/2" thick pieces of wool batting, but Ultratouch, Dacron, etc could all be substituted. I even bet cotton balls would be a worthy method for this. You can't get it too thick, or the mounting plate won't reinstall in the cup.
9- Solder terminals after glue has dried, and reinstall plate screws and cushions.
10- Enjoy!
I have a yearning to try adhesive felt around the inner perimeter of the cups as it seems like there is a midbass spot that might be resonating slightly, but I am really splitting hairs. The cups are pretty thin material and could be the reason, but who wants a heavy headphone?
I find the top-end to be polite, and nothing is offensive in relative output. These are comfortable, detailed, and sound much better than $40 has a right to. About 10 people have tried them whom ears I tend to trust, and no one has disliked them.
 
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