Amtfan

This very well done review of the Heddphone 2 reads like it was a review of the Monoprice AMT headphones, which I have. The two are evidently very similar in performance and pros/cons. The Monoprice has the bass rolloff below 60 Hz or so, and also the upper midrange dropout. These characteristics must be due to the Heil driver basic design. In my case I have used considerable parametric EQ for correction. The only significant differences according to the review are the weight and the price. The Monoprice AMT weighs quite a bit more, 680 grams. I notice that somewhat excessive weight quite a lot, though at least for me it is distributed evenly enough to not be a big problem. The other significant difference is the price, where the Monoprice AMT comes in currently at $900. There is also an annoyance in the Monoprice design: it uses an ideosyncratic oddball pinout configuration for the 4-pin mini XLR headphone connectors, so that aftermarket high quality headphone cables designed for common high-end headphones are incompatible. For instance using cables designed with the common Audeze pinout can burn out the amplifier due to shorting signal to ground.

Bobishere

The AMT is a great driver, my first ever loudspeakers were ESS AMT1 Towers (1970s) and I have used Heil based speakers ever since. However, they were never designed to be full-range drivers. The only all Heil driver loudspeaker system was the ESS Transar and it was a two-way system (Dr Heil’s patents for the bass driver are very interesting). Like all full range single speakers, there are compromises in the AMT’s performance that cannot be overcome without digital compensation and even then… In the bass, the roll off in the lower bass identifies the primary resonance as higher than ideal, not only does this affect the frequency response but it will affect the impulse response depending on the damping of the diaphragm. Damping an AMT is not an easy or exact science (it is probably harder than even electrostatics and certainly harder than dynamic drivers) and the deficiencies in the bass performance of these headphones shows that. There are also a number of other issues with AMT drivers that do not seem to have been addressed in these headphones. A bit of a shame, most of them can be solved with careful design.

I can’t really see any advances on the original Heil design for the drivers, so I am not sure where the “new” VVT technology comes in.

As to headphones, ESS made some closed AMT headphones for a short time back in the late 70s (early 80s?), they were not a success or particulary good sounding, even for the day and they were heavy. The magnetic materials available at that time doomed the whole exercise.

It is amazing how many people seem to have reinvented Dr Oscar Heil’s driver over the last 60 years, what will they think of next.