KODA^1 – Koenig’s Ortho Dynamic Acrylic Headphone

KODA^1 – The Prototype model 

After following the ortho dynamic round-up thread on head-fi.com I got interested in making my own custom cans. I knew right away that the T50RP driver was just what I needed for my custom headphone project. A driver capable of delivering an extraordinary detailed midrange – with potential for delivering a fast and tight oomph in the bass region while maintaining detailed highs, without emphasizing  them too much.

Remember to read about the  KODA^1 successor:  THE KODA^2 – Optimizing the Prototype 

About the material
Having worked quite a lot with PMMA or acrylics in the past – I know this material is dead silent when bonded with solvent and build up in multiple layers. A construction of this feels and sounds more like a solid block of granite or marble than a plastic material. It’s a bit like a solid block of aluminum – but it weighs much less. It can be cut with laser, making it easy to make completely identical parts unlike with wood. Is it better than hardwood?  No – it is different, with different sound characteristics and a much different esthetics and possibilities in design. IMHO It is more comparable with aluminum than wood concerning sound signature.

There are some downsides to acrylics compared to hardwood though. It is not as light weight. It is much more expensive in raw material and even more so to process. It requires much skill to work with and most errors cannot be corrected, meaning you have to start over. Not a beginner’s project.


The actual construction
The headphone cups are build up in 6 layers of black acrylics, 5 of these are bonded with a solvent making it more or less one piece of solid acrylic. On layer has the hole for the wiring and one has the bass port. The last one is the baffle and it is mounted with six screws to the rest of the cup, with a silicone gasket in between to make a completely airtight seal. The T50RP driver is mounted with the the three original screws and also has a silicone gasket to make another airtight seal. The small hole through the driver is extended through the baffle and the gasket.

 

KODA^1 Headphones

 

KODA^1 Headphones

KODA^1 Headphones

 

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The outer layer of the cup is covered with real wood veneer – purely for the esthetics. The veneer is bonded with epoxy and weight pressed while hardening.

 

 

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KODA^1 Headphones

 

 

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KODA^1 Headphones

 

 

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KODA^1 Headphones

 

 

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KODA^1 Headphones

 

    

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KODA^1 Headphones

 

 

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KODA^1 Headphones

 

I kept the T50rp headband and used dual angled ball joints for connection between the cups and the headband. This makes the cups very flexible and secures a perfect fit. The joints are fastened to the cups with 6 mm bolts and nuts. This will probably last a nuclear war – but I like the look and I would like to avoid any visible screws.

 

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KODA^1 Headphones

 

I found that my original bass port size needed a lot of tweaking to hit the exact sport where the oomph was deep while remaining tight, fast and well controlled. After changing the size with various tubes about 20 times – I found just the right size.

The cups has been dampened over and over again until I found just the right well balanced sound signature, with just a tad to the warm side.  The driver ended up being stripped of the mesh on the ear side and fiberglass of the cup side, making the highs shine even more with a beautiful vivid soundstage. I found the hard craft felt to be terrible harsh to the ears in the high notes, so after a lot of experimentation with materials of different sorts, I ended up with 3 mm 100% wool felt, with a square hole in the middle. The square hole extends the bass and soundstage and makes driver “breathe” better. Without it, the sound is a bit muffled up. The back side of the cups was covered with 3 mm felt, but I found that felt with holes made for at bit bigger cup and a bit more airy sound. The treble was extended a bit by using craft felt behind the holes. And finally I was satisfied with the sound signature.

 

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KODA^1 Headphones

 

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KODA^1 Headphones

Ear pads
I found the original T50rp pads to be pretty disappointing. So I planned to use the widely available and not too expensive Shure SRH840 pads. They are much more comfortable makes for a better seal.  I would like to try the Shure SRH940 velour pads sometime in the future.  The cups are actually designed to make a perfect fit with both Shure pads.

 

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KODA^1 Headphones

 

Wiring
I started with buying some very expensive Vandamme cables – but they were not nearly as flexible as I wanted them to be. So I ended up using some good quality thin OFC loudspeaker cable that I weaved into a nice and very flexible cable. They actually sounded better than the Vandamme cable with better low frequencies. I really like the new cables and I think they match the sowings on the Shure pads very nicely.

Remember to read about the  KODA^1 successor:  THE KODA^2 – Optimizing the Prototype 

Final Pictures:

 

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KODA^1 Headphones

 

 

 

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KODA^1 Headphones

 

 

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KODA^1 Headphones