What is it?
Cryogenic treatment is a fairly common process typically used for enhancing strength and durability to ferrous metals (usually steel). This process is known to convert a soft, unstable carbon impurity known as Austenite to a more stable form called Martensite. The material is then typically heated to form a "tempered" form of Martensite- resulting in extremely fine grained, evenly distributed carbides in the steel making a harder, stronger, and more durable material. That's great if you need stronger parts in your car engine, better tool and die life, or knife blades that will cut through stone like Excalibur.
But what about audio?
There is NO significant amount of Austenite or Martensite in many of the materials we use for audio. So what is happening? The truthful answer is no one really knows. Even the exact mechanics of the proven process for steel (noted above) is debated among metallurgists. Theories abound, but many speculate it may be the crystal boundries and/or impurities in the metals we use for audio that are being changed, as well as the dielectric material being affected. The result may not only be modifying the ELECTRICAL characteristics of the material(s), but may also alter the PHYSICAL/MECHANICAL properties of the metal. This would explain why a French Horn may have a different resonant quality after cryogenic treatment vs. no treatment.
VH Audio's deep cryogenic processing has been developed specifically for audio cables and connectors, and consists of a computer-controlled, slow cool-down cycle from room temperature to the temperature of liquid nitrogen (-320 °F). Our profiles use several temperature "plateaus" as the material is ramped down to below -300 °F. Once the material reaches the temperature of the liquid nitrogen, it is "soaked" for an extended period of time before being ramped-up to ambient room temperature. Again, computerized equipment is used to control the temperature ramp-up, as well as the quantity and duration of the temperature plateaus.
The $35k+ cryogenic processing machines used for our process utlize vacuum insulation, and an air circulation fan to maximize efficiency and assure even temperature distribution throughout the chamber. The chamber shape has a round cross section for the best possible airflow and consistent temperatures. Additionally, our process introduces the cold into the chamber by means of a heat exchanger, which prevents parts from being "cold shocked" by contact with liquid nitrogen.
Properly treated parts do NOT need to be cryogencially treated multiple times, if done RIGHT the first time. Once treated, the effect is permanent, unless heat or stress is applied to the part. Double, triple or quadruple cryogenic treatment has more to do with clever marketing than tangible benefits yielded, in our experience.
In the end, we are left with subjective evaluation.
From a subjective standpoint, common evaluations of cryoed vs. non-cryoed parts are:
Wider dynamic range
Smoother, more refined highs
Better bass articulation
More organic presentation
Deeper, more three dimensional soundstage
In our experience, the degree of difference vs non-cryoed parts is not the "earth shattering" or "night/day" difference that some companies' sales literature might suggest, but rather an incremental improvement more akin to an upgraded connector, cable or other "tweak". Also, in our experience, not all materials benefit from cryogenic treatment to the same degree. Brass seems to benefit more from cryogenic treatment than pure copper, and high purity silver may actually be DEGRADED by cryogenic treatment, based on our listening tests. Plated materials are also a mixed bag, with the resultant sound improvement varying by type of base metal, the plating material, AND the plating process used.