[Duggeh]

In the AMT adventure stakes, tonight I got fed up with not being able to listen to my records with the AMT. (The Amp1 and the Pro-Ject Xpression share the same powerbrick) So I dug out the transformer box.

Spent some time carefully wiring it up because I coudlnt find my magnetic screwdriver and so had to use a penknife (cables affix to the rear with screwposts). Ran it up between my NAD C352 and my missions.

Well I think that I prefer the sound of the Amp1 slightly, but turning the bass dial on the NAD around does wonders for the AMT, the sound has stepped a large leap closer to that of the O2. Im officially abandoning my "oh so high and mighty" position regarding EQ as being bad and polluting. Something this good must be sinful. EQ is sin.

Listened to my DSOTM 180 gram, and it had never ever sounded so good. Same for Brothers In Arms and F#A# (Infinity). Vunderbar.

 

[wualta]

Quote:

Originally Posted by Duggeh In the AMT adventure stakes, I think that I prefer the sound of the Amp1 slightly, but turning the bass dial on the NAD around does wonders for the AMT, the sound has stepped a large leap closer to that of the O2. Im officially abandoning my "oh so high and mighty" position regarding EQ as being bad and polluting.

This is precisely the discovery we made with the Staxen and their heretofore unregarded transformer boxes. Put about 200 watts behind each tiny driver and WHOOM, you're sinning louder and faster than anyone's ever done it before. Leaves the Polite Sound Of Stax behind.

Quote:

Originally Posted by Duggeh Something this good must be sinful. EQ is sin.

It is, as any good audio religious fanatic will tell you whilst covering your face with spittle. But isn't sin great? It just works.


Quote:

Originally Posted by Duggeh Could we get a more gratuitous shot of your AMT speakers?

Thought you'd never ask. This was the setup 2 years ago. Catspeakers on the far left and far right.

 

[Carl]

Your room reminds me of my own, with the random pieces of audio gear littering tables and such.

 

[wualta]

Quote:

Originally Posted by Carl Your room reminds me of my own, with the random pieces of audio gear littering tables and such.

One touch of audio makes the whole world kin, doncha know.

Here's a better picture of the AMT-II. It was a late model, used ESS's last-generation big Heil with the CNC'd pole pieces, but had a less-outrageous 10" fiber-cone woofer instead of the fully-outrageous 12" polypropylene cone of the AMT-1x series. Something for Duggeh to shoot for on his way to the Aulos, which is a good design but lacking some detail work relating to the sharp edges of the Heil (diffraction, diffraction and diffraction) as it hangs there imitating a coax driver. Duggeh-- prepare to uncork the Dremel!

 

[Duggeh]

The diffraction to which you refer would be the result of the 45degree outward planes of the front facing edges of the driver? Is this housing design what leads to the immersive field sound of the AMT?

I have been giving consideration to the possibility of a DIY speaker project using an AMT. Although only in the toyish idea sense.

 

[wualta]

I don't want to hijack your Ergo AMT thread, Duggeh, not any more than I already have, anyway, but the history of the AMT is so dang interestin', with yer kind indulgence I'll blather on a wee bit more. There might fall the odd relevant nugget.

Sadly, the whole fun-packed first paragraph has absolutely no application to headphones.

Quote:

Originally Posted by Duggeh The diffraction to which you refer would be the result of the 45degree outward planes of the front facing edges of the driver?

In the Aulos, the AMT is nice and small with its space-age neodymium magnets, which is all to the good, but they've still given the housing faceted er, facets and sharp, rectilinear edges. Why? or, as we'd say it in Atlanta, whah? Ideally they'd put it on a nice rounded hemispherical shell, something with big-radius curves-- like a floomin' Jecklin Disc!-- with no discontinuities that don't have to be there. The thing costs $3K US; they should be willing to pay attention to 50-year-old research that covers diffraction effects of cabinets, fer cryin' out loud...

Now notice all the nice sharp corners and edges on the AMT-II. Wow. ESS's excuse was they were slaphappy, it was the '70s, and they didn't know any better. A lie, but ESS wanted to be the poor man's Infinity, and wanted it bad. Nelson Pass worked for ESS back then, by the way. He was young, it was the '70s, they had this exclusive world-beating mid-tweeter..

Quote:

Originally Posted by Duggeh Is this housing design what leads to the immersive field sound of the AMT?

I rather think it's the dipolaricity of the AMT. It's effectively a figure-eight radiation pattern with nulls at the sides which fill in with room reverb, so it's pretty much an omnidirectional driver but with that antiphase sting in the tail.

Not too unlike the isodynamic headphone drivers we've been toying with.

Quote:

Originally Posted by Duggeh I have been giving consideration to the possibility of a DIY speaker project using an AMT. Although only in the toyish idea sense.

You want to build your own AMT? or just build a speaker around an AMT? or both? It's all doable.

 

[Duggeh]

Do you see any advantage to running the AMT balanced wualta? Its a 4 core cord, the only problem would be adapting the stock plug as far as I can see. Although my balanced know-how isnt brilliant.

 

[Carl]

Quote:

Originally Posted by Duggeh Do you see any advantage to running the AMT balanced wualta? Its a 4 core cord, the only problem would be adapting the stock plug as far as I can see. Although my balanced know-how isnt brilliant.

I guess it's just a case of try it and see. Certainly the possibility is there.

 

[Duggeh]

Ive been reading up on balanced headphones and the issue that occurs to me is how to actually connect the transformer box to a balanced output given it takes a speaker cable input. Im also uncertain what effect a balanced signal would have on the trasnformer circuit. Is there any reason why it might not like it?

I have much more reading to do, but its certainly an intriguing subject.

 

[Carl]

If you want to drive it balanced you'll need a differential push-pull output from your amp. The simplest way to do that would simply be to buy two of the exact same amp (T-amps might be good for the experiment), and then get something upstream that can split the phases for you.

 

[Duggeh]

So that would in fact be a L/R split biamp setup (doubling the wattage per channel) with an interim phase inverter between the amp output and the transformer input?

The next question, naturally, is "Where does one look for such device?" but thatd be getting ahead of myself.

The easier option would be to reterminate the cord with XLR connector as employed with normal dynamic headphones, but then I'd have to use something else to EQ the driver elsewhere in the equipement chain. This is something I'd definately like to avoid.

Your suggestion for the T-amp makes sense, trouble is they are a lot more expensive to get ahold of in the UK than elsewhere and for a bit more I could get a new integrated Denon. Or stagger buy, one amp to run the AMT as is, then a second one later to try the balanced arrangement...

 

[wualta]

Quote:

Originally Posted by Duggeh Do you see any advantage to running the AMT balanced wualta?

Let's just say that I am yet to be convinced. So many things to do before that.

 

[Carl]

Oh by the way, has anyone tried the TakeT piezoelectric heil drivers?

http://www.taket.jp/about2/about2.html

 

[Duggeh]

1500 bucks is a lot of money for something that looks like that. The principle seems interesting though. If im reading the article with its mish mash english correctly, its a heil driver made from a peizo element.

Suitable for dogs cats and bats everywhere then.

 

[setmenu]

Quote:

Originally Posted by Duggeh As for you EQ in the amp suggestion. I believe the AMP2 is a full class A with a meticulously designed EQ curve. The Amp1 imho could use a lift of a few db at around 40hz to give the sound a bti more meat. This might be accomplished with a beefier power supply, but given the amps topology I doubt it..

Hi Duggeh
Great review,nice to see the 'guts' of the amp and phones.
Regarding bass, it would be interesting to see whether the amps output is
filtered or the transducers themselves limit the bass.[I could not see
evidence of additional filtering at the traducer end of things]
My experience with my own Planar magnetic transducers [ribbon type]
was that they were capable of very powerful raw low end output.
This resulted it quite a large excursion of the ribbons.
I reduced output to achieve less excursion and a better balanced sound.
The Heil design design looks like it would become very mechanically noisy if
the pleats moved to far when doing bass duties.
Besides the loss in sound quality excessive movement may well create a
higher risk of metal fatigue in the conductors at the relatively sharp bends in
the pleats.
So it could be wise to exercise caution if you do decide to go the 'bass
boost' route, they may sound a better but at the risk of early failure.
I am only guessing here, so it might be worth asking the manufactures for
their views as to the potential risk.


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