Do they have that Stax-ish airiness?

Not quite. They don't have the airiness of the STAX. I think the HD800 has more air than the HE6. This is one of those things that's hard to determine with graphs, but I get the feeling that "good air" requires the following on the FR graphs:

• No roll off before 16k
• No sharp peaks or dips between 10k-20k. For some odd reason, reasonably smooth seems to be a requirement for air.

HE6 responds well to EQ if you want to tone the treble down. I also tried to EQ it to make the bass sound like the 007 with less success. There's a little bit of thickness - probably 2nd order harmonic to the HE6 bass. The strength of the HE6 is not with the bass, although it's still pretty darn good. LCD3 bass kills it though.

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As far as the etch, I am wondering if the 5.5k resonance mode and 12k mod (almost but not quite an octave apart) count for the double penetration ridges of death? See [4] in http://www.changstar.com/index.php/topic,71.0.html

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BTW. Very good impulse response.

BLUE = HE6
RED = HD800

I forgot to try the EH 6SN7. BTW both the Melos and BA had no problems powering the HE-6. The HE-6 was actually as tolerable as ever. But as many know, I have no tolerance for etch. Maybe with a PCM1702/04 based DAC.

They don't have the airiness of the STAX. I think the HD800 has more air than the HE6.

I was going to say that this is probably related to the ability of the respective drivers response time but your impulse data suggests otherwise.

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BTW. Very good impulse response.

Are these measurements frequency dependent? I would be curious if impulse data taken at 80Hz, 500Hz, 4KHz and 10kHz all look similar. The HD800 should be fairly uniform due to the radiator, I suspect that the big driver orthos generate different frequencies from different areas of their driver ( I should add more optimally ) If you picture a membrane stretched fairly tightly over a circular frame with the edges glued down  - the center has to have more flex than the edges. Vintage yamaha / fostex worked around this by pleating the driver , which is why I think many of them roll off the top end.

sidetrack
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Here is a project for you Purrin, we need raw driver data from all the different types of planar drivers out there, most of them have been pulled apart at some time so we know fairly well the inner construction , we would also need to measure the tension of the fixed drivers.

To my knowledge, the HE6 is a fairly taught fixed driver without pleats, traces are broad and sparse (relative to others ) and yet it provides excellent performance.

If we had a database of all these parameters we may see a pattern emerge to help us understand why a particular driver does better than others.

..dB

I forgot to try the EH 6SN7. BTW both the Melos and BA had no problems powering the HE-6. The HE-6 was actually as tolerable as ever. But as many know, I have no tolerance for etch. Maybe with a PCM1702/04 based DAC.

Interesting.  Even w/ the Lyr and that Audio GD disgrace from the Venice meet the HE6 was always less controlled and more congested than the HD800 on my speed tests.  I'll have to try it from the S7 and Sansui one of these days.