This blog post features an ongoing project to design and build carbon composite diaphragms for certain compression drivers. The first being the popular JBL 2446H which uses a 4" diaphragm and 2" diameter throat. The stock JBL diaphragm was compared against the latest carbon composite prototype and the results are displayed below. The goal would be to offer these commercially to the audiophile market. I am collaborating with a friend on this project. We shall call him Mr. Carbon, since he owns a company manufacturing high performance carbon composite sports gear and would like to remain anonymous. Mr. Carbon is also an audio enthusiast and the initial set of measurements shown below were conducted by Mr. Carbon. I will conduct my own testing once I receive the prototype diaphragms from Mr. Carbon. I've also purchased a pair of my own driver from Ebay so that I can conduct my own testing without having to ship these heavy drivers back and forth between myself and Mr. Carbon.
|My recently purchased JBL 2446H drivers with original JBL diaphragms|
|Stock JBL 2446H Titanium Diaphragms|
Why carbon composite?
Without getting too technical there are obvious advantage to carbon composite as evidenced in it's use throughout any application requiring light weight and high stiffness. Race cars, sports equipment...you name it and you'll see carbon composites used. Extreme stiffness, combined with light weight and good internal self damping characteristics makes this material ideal.
The diaphragm is formed from a hybrid of various materials. The latest version includes an internal umbrella structure to stiffen the structure and dissolve potential modal build-up.
The horn used for the testing was a ES-300 which is similar to the JMLC. It's not not known at this point why there is a dip at 1.6kHz.
|Original Diaphragm (Red) versus Carbon (Black)|
Worth noting is the higher sensitivity of the carbon diaphragm. There also appears to be more usable treble.
This is the real litmus test to a driver's overall sound quality. As you can see from the Spectrogram burst decay that the carbon driver exhibits much quicker decay especially in the upper treble.
|Spectrogram Burst Decay for Original Diaphragm|
|Spectrogram Burst Decay for Carbon Diaphragm|
This has gotten me very excited about the potential this hybrid material combination has to offer. We are also working on a carbon composite diaphragm for the TAD TD-2001 which currently uses a beryllium diaphragm. Stay tuned for future developments.