Diaphragms and Voice Coils - Nano-Scale, Ultra-Thin, Parallel Uniforce
April 15, 2019
Diaphragms and Voice Coils - Nano-Scale, Ultra-Thin, Parallel Uniforce
Blood Is Thicker Than Water
Before we begin, we’ll ask for your brief indulgence. We’re going to give you a few typical measurements, just to set the stage for a little infusion of Audeze tech knowledge. A piece of standard printer paper is about 100 microns thick. An average human hair is about 75 microns thick at the base. A red blood cell is only 5 microns across. What’s a micron, you ask? It’s a measurement of length. A very, very small measurement. One one-millionth of a meter to be exact, or about 0.00004 inches.
Pretty small, right? Why in the world are we talking about blood and hair and microns? (oh my) Well, my friends, it’s because we at Audeze have become very good at making things thin. Let us hit you with one last measurement that’s a bit more relevant: 0.5 microns. 1/10th of the thickness of a red blood cell. Nano-scale. Why does this measurement matter to your headphones? It’s all about the diaphragm.
You And Your Beautiful Heart
The real heart of what makes a pair of planar magnetic headphones special comes from one component - the diaphragm. To understand why the diaphragm is so important, you must first understand how headphones work, at least in a broad sense. Headphones use two main components to make sound, the magnet and the diaphragm. The magnet creates a static magnetic field. Electrical current passing through the diaphragm’s voice coil interacts with this magnetic field, which pushes the suspended diaphragm back and forth. The diaphragm movement pushes and pulls the air around it, which causes a series of pressure waves. These pressure waves are interpreted by your brain as sound.
Headphone diaphragms have to do this FAST. To produce sounds in the upper range of human hearing, the diaphragm would have to move back and forth over 20,000 times per second. For this reason, one of the most important factors in accurate sound reproduction is the mass of the diaphragm that the magnets move. In a typical pair of headphones, the diaphragm is usually a cone of plastic, cardboard, or lightweight metal. Audeze’s diaphragms are completely different, and this is where that micron measurement comes into play: the diaphragms in our headphones are flat sheets of film that are orders of magnitude thinner than a human hair, and are so light that they actually weigh less than the air that’s being moved!
That extreme weight reduction is a key factor in our headphones’ superlative transient response (see our tech article detailing transient response, transparency and resolution here). In short, transient response boils down to this: thin diaphragms mean less weight to move; less weight to move means less inertia of the diaphragm to overcome. The faster the diaphragms can change direction, the more detailed, accurate, and transparent the sound.
The Way You Do The Things You Do
At Audeze, we produce all of our drivers in-house at our Southern California facility. The process is entirely proprietary, so nobody else in the world does it like we do.We start with film that’s strong, ultra-thin, lightweight, and flexible. Through an extremely slow and precise vacuum deposition process (it takes about two weeks for this process alone in our LCD-4 series), we create a thin metal layer on top of the film, which we then micro-etch to create the voice coil.
The length of the voice coil is one of the deciding factors in the quality of the sound produced by the headphones, but the deposited metal also increases the strength and flexibility of the diaphragm itself. One of the many advantages of the ultra-low weight of our flexible, oversized diaphragms is that they have very high compliance (a measurement of how much a surface can “comply” or convert an electrical impulse into soundwaves) and the extremely large surface area that is required to produce deep bass. In contrast, the dynamic drivers found in most headphones use diaphragms that are small, heavy and very stiff. This makes them incapable of achieving the same levels of resolution and bass reproduction as Audeze’s planar magnetic drivers.
We’d Like To Get To Know You On A Nano-scale
Most of our headphones feature our Ultra-thin diaphragm material, but our flagship headphones like the LCD-4, LCD-4z, LCD-5 and LCD-i4 feature some of the thinnest diaphragms in a production headphone anywhere in the world, which we call our Nano-scale diaphragm. Developing this unique diaphragm meant creating a new formulation for the film from scratch. Even measuring the diaphragm’s thickness during production was difficult. Our engineers kept busy making it work as we developed new measurement techniques. Remember that 0.5 micron measurement from before? Turns out it’s a bit tricky measuring something thinner than a red blood cell!
Our Nano-scale film has an extremely low dielectric constant and acts as a perfect insulator, meaning that it almost completely inhibits electricity flowing through it. Its high elasticity provides the high compliance needed for bass reproduction, and the extremely low mass provides the ultimate resolution and transparency.
I Want To See You Shake Your Uniforce, Baby
One of planar magnetic technology’s “claims to fame” is its ultra-low distortion. However, not all planar magnetic drivers are created equal. Planar magnetic technology does not automatically guarantee a uniform magnetic force (or flux) across the diaphragm surface, and achieving this is a key way to reduce distortion even further. The force acting on the diaphragm is proportional to the amount of magnetic force being produced by the magnets, but the magnetic field is almost never uniform (you can read about our Fluxor™ magnet arrays here). How do you solve this problem?
Our engineers came up with a novel and patented solution in 2015: Why not vary the width of the conductor so it’s wider where the magnetic field is stronger and thinner where the magnetic field is weaker? This would ensure that all parts of the diaphragm experience the same force, resulting in more truly pistonic motion. Thus the Uniforce™ voice coil was born.
Not content to rest on our laurels, in 2021 we developed and patented the Parallel Uniforce™ voice coil, which achieves even more uniform force by altering the current density within each parallel circuit trace. The parallel traces have variable width and were optimized to achieve a uniform force over the entire surface of the diaphragm without increasing the impedance. The uniform force helps avoid distortion and provides better control over the driver resulting in improved resolution. (Imagine breaking a thick pipe up into several smaller pipes-- they move the same amount of water, but the pressure in each pipe can be altered to suit the needs of the circuit.) Parallel Uniforce™ was first used on the limited edition LCD-R and the flagship LCD-5, and will be rolled into future models from here.
Audeze uses “a genetic algorithm-based heuristic optimization technique together with magnetic simulations to optimize trace widths to achieve Uniforce.” For those of us who don’t speak Enginese: we use advanced computing techniques to get the most uniform distribution of force possible on the diaphragm. This is what allows our headphones to deliver virtually distortion-free listening experiences with the greatest accuracy and detail offered in any headphone in the known universe.
Great things can come in small packages
Although they’re so insubstantial that they’re measured the same way you’d measure bacteria, our diaphragms play a very substantial role in what makes our headphones some of the best reviewed in the world. They weigh so little, but they do so, so much-- providing a great example of how Audeze goes to great lengths over tiny distances in the continued quest for uncompromised audio.