A ZMF x Vibro Story

A Cherry ZMF x Vibro in RUST stain and Architectural Bronze sliders.

Even before the ZMF x Vibro, I’ve always had an inclination towards wood.  It’s been more or less sub-textual, but my life activities have often revolved around the amazing organism that wood is.  Before we get too into my “heart-throb” story, here are a couple neat facts about wood and the ZMF x Vibro, I'll interject these throughout this post.


1.       The lightest and softest wood in the world is Balsa, with a specific gravity of .16, the heaviest and hardest wood in the world is snakewood at 1.30 specific gravity.  For wood to sink in water, it must have a specific gravity over 1.00.  The wood used in the ZMF x Vibro is “Black” Cherry, and “Black” Walnut.  Black Cherry has a specific gravity between .47 and .56, Black Walnut is between .51 and .61. Don’t try to float your Vibros - not a good idea!

a.       ZMF x Vibro Fact:  Despite slight variances in wood, all ZMF x Vibro’s are tuned to the same frequency response curve, and although harder woods can have a little bit of a “brighter” tone, Cherry and Walnut were chosen for their similar densities and sound after “final tuning” was completed.  Whether choosing Cherry or Walnut, it will not have an impact on the sound of the ZMF x Vibro’s.

When I was a youngster and teenager I played a lot of baseball. A lot might be an understatement. I spent hours in the field behind my house perfecting my swing. I loved wooden baseball bats. I would stay out in my field trying to become a better baseball player by focusing on the natural sweet spot a wood bat provides.  I was especially transfixed by the different shapes and species of wood that were used to create fine wood bats. I ordered my bats from a variety of companies excited to explore the nuance of the wood and the construction. Getting to know each bat in an intimate and dynamic process that was extremely fulfilling. At one point, a company known as “Sam Bat” had gained popularity and carved out a niche making Maple bats. Not long after, many other companies followed suit opening up a fascinating market.  The beauty and functionality of a Maple baseball bat was awesome and fascinating to me.

After college and years of wear and tear on the body, I stopped playing baseball. It was at this point that wood came back into my life in another way. During this period, I spent my time playing acoustic guitar. My interest built and before I knew it, I was in my basement building my own acoustic guitars. Many small acoustic guitar companies had cropped up similar to the craft beer boom and again my attention was piqued by sampling wooden guitars of all varieties and discovering their unique distinction. I continued to build my own instruments and became obsessed with tone-wood and “tuning” each acoustic guitar by measuring the thickness of each piece of wood on the guitar, and then carefully tapping the top and listening as I shaved the braces with a chisel. 

Three sets of ZMF x Vibro cups in the polishing stage.  Colors from left: Rust, Cardovan, and Empire Red

Three sets of ZMF x Vibro cups in the polishing stage.  Colors from left: Rust, Cardovan, and Empire Red


The world's slowest growing tree is a White Cedar located in Canada. After 155 years, it grew to a height of 4 inches and weighed only 6/10th of an ounce. The tree can be found on a cliffside in the Canadian Great Lakes area.

The world's fastest growing tree is the Empress tree. This tree can grow up to 20 feet the first year and some have been documented growing 12 inches in 21 days!

Black Walnut trees that produce the wood for the ZMF x Vibro vary in growth like many other trees depending on where they are planted and how desirable the condition are.  Top quality wood tends to be 50-100 years old and 70-80 feet tall when harvested and used.  Walnut has larger pores than the tiny pored Cherry that we also use for the ZMF x Vibro’s, this gives the wood more “texture” to the touch, and a natural feel to the wood.

The Cherry used in the ZMF x Vibro’s also grows to approximately 70-80 feet, is harvested between 30-100 years old and has much smaller pores than walnut, giving a smoother feel, and is silkier to the touch.  The Cherry we use is mildly curly, with very evident grain lines, giving a great depth and visual texture.

One thing I noticed both through playing baseball, and in acoustic guitar tuning, was that nothing gives the craftsman, or user, feedback like wood does.  If you hit the ball in the right or wrong spot, or place the braces correctly, you will know by how the wood reacts when contact is made with it.  A thud, thunk, or thwooooooong, will say so much about the “instrument,” how you’ve created it, or how you’re using it.   It’s a beautiful thing, a human connection that you simply cannot get with any plastic or composite object (yes I tried composite acoustic guitars, not the same!).  I have noticed when tuning the ZMF x Vibro, I can literally feel the vibration of each ear working together when it has been tuned correctly, something I can’t say for any other plastic headphone I’ve tried.  I do urge those interested in acoustic guitars to check out FRETS.com or Ervin Somogyi’s blog.


Some African Baobab trees can store more than 25,000 gallons of water in their trunks.
Also, some with age have become hollow and have been used as homes. One was even used as a bus stop and could shelter up to 30 people.

The ZMF x Vibro’s need wood that is at least under 10% moisture content to work for being made into headphone cups.  Our Cherry is approximately 6% moisture content while the Walnut is about 8%.  This means that no matter what environment, if used properly (not getting them wet) then the wood will be stable for the long haul and not warp.  Cherry and walnut are both also very stable woods.  We wanted to try to accommodate to custom wood orders but after a number of tests with exotic and other wood, we found it hard to get a consistent supplier for high quality, dry exotic wood without building a kiln, and spending the time to dry wood.  This was a cost we’d didn’t want to pass on to the ZMF x Vibro owner, so here we are!

In graduate school, I didn’t have a wood-shop, as I moved to Chicago, and through my studies had more time to listen to music, and less time to make things.  As I came nearer to the end of school I started fiddling around with the t50rp, gave my brother a set and started selling sets just so I could recoup money to eventually make myself the “perfect” set.  I got the modification where I wanted it, and people were asking for pairs, so ZMF headphones was born.  After making a number of sets I knew I wanted to make a set out of wood.  But without the proper tools, less and less time as ZMF grew, and no business partner, I knew I had to find someone to help me make the cups.

I turned to numerous people for advice, had a few failed attempts with valiant help, and one thing became increasingly clear, someone with a vast knowledge of headphone parts, and an understanding of how headphones work was needed to collaborate on a wood cup. You can tell someone exactly what you want in a headphone cup, but you can't make someone enjoy what they’re doing.  As you know, a love for headphones is not something easily transferred to someone else if they aren’t passionate about them, just ask my wife!

So then, one day during a procrastination session, looking at Grado headphones on ebay because my dog, a beagle had eaten my sr60’s that I’d had since high school, I came across some woody grado cups made by Turbulent Labs.  I searched on facebook for their website and came across their facebook page, and saw something that looked like it was for the t50rp, and made out of wood.  My heart skipped a little, really, I know, silly, but yeah.  I wrote this email:

I saw a picture of a wood Fostex t50rp cup (I think) on facebook that you may have made?

Anyways, I am in the process of designing a t50rp cup with both a wood cup, but I’ve hit some road-blocks and it’s been a tougher process than I first imagined.

I would be interested in some sort of collaboration where we tune the cups you make and then sell them under the ZMF Headphone line-up and I could use both of our names.
Anyways, hopefully this is something you'd be interested in!  You can email me at the address above or call me anytime at xxx-xxx-xxxx

I am located in Chicago, IL, USA and you can check out my website at ZMFheadphones.com


Zach Mehrbach


Within a few days I spoke on the phone with Luke Pighetti, now of Vibro Labs, on the phone.  We had a rather long conversation, and it seemed our businesses were more alike, and very compatible in that his expertise was parts, and my expertise was sound.  We both had, and have a passion for wood, and both love creation, and the process of collaboration.  The three things needed to create a great headphone, or really anything.  Over the period of the next month Luke and I spoke almost every day, throwing ideas back and forth, sometimes on the phone, sometimes over skype, and many many times on g-chat.  In the end a design with similar depth to the original t50 was settled upon, at 1 inch deep, with greater in cup volume provided by the circular shape, and three bass ports on the front of the cup. 


The world's tallest standing tree, a Redwood, is in Humboldt State Redwood Park California. It is 368 feet {almost 37 stories} tall.

The world's largest diameter tree, a Redwood is in California. It is over 90 feet in diameter. Its root system is spread out for more than an acre.

The ZMF x Vibro has walls that are between 5mm and 6mm thick throughout.  This is quite thick and very stable, especially when compared to the Audeze LCD-XC, which has a thickness of between 2-3 mm.  Pair this thickness with baffle support beams that flute into the wood with flat, volcano like peaks.  This provides a very firm support for the baffle, and it can be felt, as the headphone plays as a whole, vibrating with the special ZMF tuning in unison with the music and sound that emanates from the ortho-dynamic driver.

Between getting the first prototype and the final design, there was much trial and error.  I certainly had an “oh f***” moment when I got the cups and attached the drivers, and measured them.  The response was much wonkier than a stock t50rp, and I had no idea how I was going to tune them.  A few monstrous mod sessions later I had found the general basis for what s now the ZMF x Vibro sound. A slightly bass enhanced, exceptional imaging, engaging and extended sound with very linear treble and a nice smooth, yet slightly gutsy mid-range.  My greatest fear was squashed, and I took a deep breath, the ZMF x Vibro would indeed sound better than the original ZMF.  I was worried that I had made the original enclosed ZMF’s sound so could that I couldn’t surpass their sound, but indeed, the living being that is wood enabled me to go further, and in a beautiful way. 

In my excitement I sent Luke a bunch of different sets of measurements and comparative graphs, and in turn he sent me designs and video’s of the cups being made on his state of the art equipment.  We both loved the process of creation, and the great results we were getting.  Also to boot, he was, and is easy to deal with, professional and provides valuable feedback without ever being contentious or shy about stating how he feels.  Many qualities that are uncommon, but necessary.


Cherry wood is photo-reactive, so when exposed to light it will darken over time, aging to a nice amber/brown color.  The ZMF x Vibro’s in Cherry, whether left natural or stained, will color with age, like a fine wine, becoming more mature each year!

When figuring out the logistics of the ZMF x Vibro I wanted to be able to offer many custom options just like with the original ZMF’s.  One of the things I wanted to do was to offer a plethora of wood options, as well as do custom sets.  At first I thought this would be easy to do, find a good supplier of multiple wood varieties and just buy the wood as needed per order.  I did a few test sets, one of which my father got for his birthday made out of paduak.   A beautiful set.  A few things happened that changed my initial desire to offer almost any wood imaginable:

1.        We had some itchy, scratchy, respiration issues when working with some exotic woods.  These woods are called sensitizers, because some people are allergic to them.

2.       Many woods had varying amounts of moisture content.  The Vibro needs below 10% moisture content to be stable enough to be made into headphones.  I like it to be even lower.  The Cherry we use is 6% and the Walnut is about 8%.

3.       The cost of exotic woods varies greatly.

4.       The workability and finishing process of woods varies greatly.  Woods with high density and larger pores makes for a varying finishing process with each wood.

Because of the above, I decided to find a couple woods (cherry and walnut) that are easily available, cost friendly, and beautiful while allowing me to put out a quality product for a great price.  My personal favorite is the Cherry for its beautiful grain,  warm color, and consistency in quality.

Now, about seven months after my collaboration with Luke at Vibro Labs started, the ZMF x Vibro has been out for about three months and everyone who has a pair dearly loves them, and they are often compared side by side with the likes of the Audeze LCD XC and Fostex TH900 and other uber hi-end closed headphones that cost over three times as much.  Many times this causes me to question myself, “are these really that good?”  While I am admittedly biased, I do know that they are both physically, and aurally as enjoyable a headphone experience I’ve ever had, and those who own them seem to like them...a lot!  There’s a satisfaction that comes with interacting with each customer to make sure their headphone is exactly what they want, and that gives me great pleasure. I love making these headphones.

Zach Mehrbach