The best wireless headphone setup was probably the AKG HEARO 999 Audiosphere II. That's quite a long name, and not easy to remember. I'll call it the 999 from here on out. I learned about them from a German audio engineer that uses them daily in his mastering studio. They were aimed for the pro market with a feature set far beyond what most consumer users needed, and they had a pricetag to match. The technical specs were tops, and I see nothing else for sale today that can take their place, unless Beyerdynamic is still building the competitive setup that sold for about $2500.
No audiophile needs to monitor three different transmitters from their wireless headphone, but the HEARO 999 could do it. It has a top quality DAC that I use in place of the one in my CD/DVD player. Each wireless headphone sold at a discounted price of $500, and few people could afford the $1200 initial setup with one headphone. My setup has two headphones, one to listen while one is charging. Otherwise, you will have to open a headphone to change battery pack about every 2 or 3 hours, depending on volume level.
The transmitter base has many features, and it has the thickest manual you ever saw for headphones, and thicker than any other piece of audio gear I ever bought. It comes in a very nice foam lined hard case made for hard traveling pro use. You could use the transmiter for a preamp in an audio system, besides using it as a DAC. Add an input switchbox that adds to the three inpuits already available, and add some processor loops, and you have a full fledged line level audiophile preamp.
The hardwired headphone amp is very good, and it works to perfection with my K601 cans. I think AKG voiced it to drive their cans, but something with a similar midrange centric sound would also work well. No trouble driving very inefficient headphones, which AKG are famous for being, at least the pro level ones.
I like the 2-channel synthesized surround sound, which is why it is my home theater preamp as well as my headphone amp and wireless transmitter.....besides being my outboard DAC.
Those who say wireless headphones can never sound as good as hardwired don't know what they are talking about. What they cannot be is as light as regular headphones. You have batteries, receiver, DAC and amp stuffed away in those cans, and they are bigger/heavier than those cheap consumer wireless headphones by quite a bit. It is as big as the K601 or K701 but much heavier. If the weight does not bother you, then yes, they can sound as good as all but the most expensive hardwired headphones. The transmission is digital, and does not suffer analog transmission problems. Sound quality is dependent on the inboard DAC and amp, as the headphone itself is a very high quality unit as good as say, a DT880, K701 or K601.
The cost of the DAC and amp in the headphone alone costs as much as the cheap consumer complete wireless headphone setup. For $1200 AKG could deliver a product far above mass consumer standards.
Besides the price, the extensive feature set like synthesized ambient sound environments was probably far beyond what most consumers wanted, and I couldn't imagine most everyday folks reading and really understanding the entire manual. I suspect most 999 setups will end up in pro hands, but you could build an entire miniature high end audio system around this unit.
