The Ergo AMT Review. (56k, Dont Even Try)

[skudmunky]

Duggeh, I send you out on a mission: Buy many many more headphones so that we may enjoy more reviews from you!

Seriously, great review. Ever since I first saw a Float I've wanted to try one. Maybe someday...

[GreatDane]

Originally Posted by saturnine

This is the absolute best review I've seen here.

I agree. Very good job sir.

[Blueiz]

I do believe The Bard is amongst us........

[wualta]

Originally Posted by Duggeh

The upper and lower areas of the driver on the outside facing edge do appear to be covered by some sort of wolly material held in place by tape, as evident from the photos, the inside facing edge has this also but not over as great an area.

Ah. So the pleats of the AMT extend farther above and below the tape (I couldn't tell what it was, what with the spirochete design motif embedded in it or printed on it), and yes, there's something squidgy under that tape. But most of the driver is hanging out there in space, though squished slightly by the pole piece crossbars.

The tape would appear to be reflecting some of the sound back to the driver. I wonder why they didn't use netting or framing to hold the woolly stuff in place..?

Originally Posted by duggeh

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 bit more meat. This might be accomplished with a beefier power supply, but given the amps topology I doubt it.

It would certainly need a bigger heatsink! But I would think that even AMP1 must be supplying some extra bass, no?

Maybe it would be best to operate it from a good speaker amp's outputs with a custom digital EQ in the loop. Hard to say from here.

The Ergo passive box does seem to be supplying some EQ of its own.

My ideal amp to drive an AMT full range and use it as a headphone would supply absolutely hellacious amounts of bass boost with a sharp cutoff (and maybe an overall frequency-response tilt downward toward the treble end), but only at moderate levels. It would cut back, starting with the lowest frequencies, as you cranked the amp up, so no matter what you did, you'd still get clean sound. A soft-clip circuit would also be a good idea, I should think.

I'd also go for the tightest possible seal to the ears/cranium I could get to keep that bass from leaking away, but that would do violence to the Jecklin Way.

Originally Posted by Duggeh

Why do you ask about the padding? What purpose does it serve? Some sort of resonance control?

Precisely. My experience with a hardworking miniature Heil tweeter that looks surprisingly like your Ergo AMT driver is that at some midrange frequencies there's a narrowband natural resonance, which causes a kind of edginess. Some stuffing on the backside of the pleated surface cured the problem. Even the big Heils have a noticeable twang. I figured driving a small Heil full range, since small=stiff, might exacerbate the problem... or it might not. If you hear only a nice smooth flat response, then Precide's efforts (and sheep) have wrestled the problem to the noise floor.

Originally Posted by Duggeh

If theres one design flaw id cite with the construction of the headphones its the poor way in which the drivers are affixed to the housings.

I understand your concern, but unless the job was done so badly that the driver's likely to come loose, it's actually better that the mounting is soft and nonresonant. In audio, rigidity is often sought but just as often creates intractable problems. A real Caccia-22, as the Italians say. In any case, I wouldn't worry about it.

Originally Posted by Duggeh

ps, thanks for your kind words.

Quite welcome. I was very pleased that you thanked your dad for his Stax and, indirectly, for owning them, thus shining the Staxlight of goodness on your upbringing.

[jjcha]

[Duggeh]

Originally Posted by wualta

Ah. So the pleats of the AMT extend farther above and below the tape (I couldn't tell what it was, what with the spirochete design motif embedded in it or printed on it), and yes, there's something squidgy under that tape. But most of the driver is hanging out there in space, though squished slightly by the pole piece crossbars.

The cross bar structure of the magnets may aid with the reducing the resonances you mentioned further down.

Originally Posted by wualta

The tape would appear to be reflecting some of the sound back to the driver. I wonder why they didn't use netting or framing to hold the woolly stuff in place..?

The small amount of backwave reflection probably acts as a bass tweek. When you block off the outward facing edges with the palms of yoru hands there is a notable baffled bass increase.

Originally Posted by wualta

It would certainly need a bigger heatsink! But I would think that even AMP1 must be supplying some extra bass, no?

The Amp1 is EQ'd yes, but the Amp2 has a much improved curve (four years of tweeking I think the Precide site says), and its a large heaksinked affair with a seperate power supply.

Originally Posted by wualta

Maybe it would be best to operate it from a good speaker amp's outputs with a custom digital EQ in the loop. Hard to say from here.

The Ergo passive box does seem to be supplying some EQ of its own.

When I contacted Precide about fixing the broken connection in the box I was told that the Box is EQ'd and that its a lot to do with the coils. Althogh I've no idea of the specifics. Not my area of expertese.

Originally Posted by wualta

My ideal amp to drive an AMT full range and use it as a headphone would supply absolutely hellacious amounts of bass boost with a sharp cutoff (and maybe an overall frequency-response tilt downward toward the treble end), but only at moderate levels. It would cut back, starting with the lowest frequencies, as you cranked the amp up, so no matter what you did, you'd still get clean sound. A soft-clip circuit would also be a good idea, I should think.

Perhaps the Amp2 integrates these features.

Originally Posted by wualta

I'd also go for the tightest possible seal to the ears/cranium I could get to keep that bass from leaking away, but that would do violence to the Jecklin Way.

Just last night I spent a quarter hour gently bending the headband inward. I've now got all the comfort, but with a more secure less flappy fit and with measureably improved low end. I think that a closed design would be murder to baffle well.

Originally Posted by wualta

Precisely. My experience with a hardworking miniature Heil tweeter that looks surprisingly like your Ergo AMT driver is that at some midrange frequencies there's a narrowband natural resonance, which causes a kind of edginess. Some stuffing on the backside of the pleated surface cured the problem. Even the big Heils have a noticeable twang. I figured driving a small Heil full range, since small=stiff, might exacerbate the problem... or it might not. If you hear only a nice smooth flat response, then Precide's efforts (and sheep) have wrestled the problem to the noise floor.

The resonant frequency of the driver pleats is right down below 20 hz. I watched and listened while I was doing the test tones. Theres no driver caused distortion anywhere in the main spectrum insofar as I can hear.

Originally Posted by wualta

I understand your concern, but unless the job was done so badly that the driver's likely to come loose, it's actually better that the mounting is soft and nonresonant. In audio, rigidity is often sought but just as often creates intractable problems. A real Caccia-22, as the Italians say. In any case, I wouldn't worry about it.

It was just the absense of actual mechanical fixation that had got my eyebrow up.

Originally Posted by wualta

Quite welcome. I was very pleased that you thanked your dad for his Stax and, indirectly, for owning them, thus shining the Staxlight of goodness on your upbringing.

My dad got his Stax after being so impressed with my first one. I converted him. His only previous headphone was an '80s model DT880. Although for almost all his listening he uses Triports.

[wualta]

Originally Posted by Duggeh

The cross bar structure of the magnets may aid with the reducing the resonances you mentioned further down.

Yep, or, since they bi- and trisect the pleats (some of 'em, anyway), they'd move the resonant frequency way up where it might not be much of a bother and actually be easier to damp out. That looks accidental rather than intentional, though we'll take what we can get.

Sounds like they've got the Heil snubbed down tight enough for our purposes. Good enough is good enough.

Originally Posted by duggeh

When you block off the outward facing edges with the palms of yoru hands there is a notable baffled bass increase.

Whoa-- that's opposite of how it works with regular headphones. There's always a treble buildup instead. Sounds like you've stumbled upon your first mod. Shoot off an urgent missive to Precide. Anything that will give this baby more bass is exactly what both of you need. Keep us posted on this little development.

Originally Posted by Duggeh

When I contacted Precide I was told that the Box is EQ'd and that its a lot to do with the coils.

It looks very much like part of a speaker crossover network.

Originally Posted by Duggeh

I spent a quarter hour gently bending the headband inward. I've now got all the comfort, but with a more secure less flappy fit and with measureably improved low end.

As Sennheiser famously taught us, get that diaphragm close to the ear if you want more bass. Glad to hear you got simultaneous improvements in comfort and bass.

Originally Posted by Duggeh

I think that a closed design would be murder to baffle well.

It's hard for me to say what would happen. It's all so different from the usual headphone mechanical system. Would the enclosed cavity cause problems? Would the resonant frequency of the system rise due to the trapped air? You could do some quickie experiments with strips of closed-cell foam to try to enclose the ear somewhat and see what happens to the bass and also to see if the response curve roughens up.

Originally Posted by Duggeh

The resonant frequency of the driver pleats is right down below 20 hz.

Technically, that's not likely, since there's nothing I can see in that driver that's heavy enough and/or floppy enough to resonate at a frequency that low. Think of the example of subwoofer cones. Given the size, stiffness and mass of the Heil's pleats, you'd expect a free air (undamped, unclamped) mechanical resonance at around 2kHz, about the sound you'd get flicking a credit card (yes, the famous credit card resonance). But as you say, it's not audible:

Originally Posted by Duggeh

Theres no driver caused distortion anywhere in the main spectrum insofar as I can hear.

This is all that really matters.

Originally Posted by Duggeh

It was just the absense of actual mechanical fixation that had got my eyebrow up.

I'll bet these things are assembled and tweaked by hand individually. They can't be sellings millions of 'em. I'll leave it your literary imagination to give us a mental picture of the platoons of orphans they employ and their nationality. In any case, stay vigilant; keep a sharp eye out for the dreaded fallapart. I'm betting it won't happen. In fact, the construction may act as a shock absorber. Those of us who've dropped Heils know that the magnets are holding the thing together and a sharp blow makes things shift around sickeningly.

Originally Posted by Duggeh

My dad got his Stax after being so impressed with my first one. His only previous headphone was an '80s model DT880.

That's good enough. Most dads don't even use headphones, and remember, the 880 was expressly Beyer's attempt to mimic the sound of their ET 1000 'stats in a dynamic 'phone. So it still works. Besides, no decent dad would spend the money on 'stats whilst little porkers like you are crawling about the house in diapers. It's not good form. So it's poetic justice that you influenced him to finally spend the money to get the Stax.

Originally Posted by Duggeh

Although for almost all his listening he uses Triports.

Triports? We'll tiptoe out of that room quietly and close the door. It's better that way.

[stewtheking]

First off, awesome review. Truly awesome. Puts some of my inarticulate ramblings to shame.

And yes, I have been truly converted to team circumcranial.

[wualta]

This is a cat who likes to use an AMT for a pillow. This particular AMT was killed by UPS. We stuffed it and mounted it near the front door as a warning to all UPS representatives and to let all visitors know that they are about to enter an AMT-infested home (ESS AMT-II speaker visible behind cat). We're thinking of putting a bulb in it and converting it into a Japanese lantern-- the AMT, not the cat. Although...

Keep us up to date on any AMT adventures you get up to, Duggeh. See if you can get some AMT speakers to go with your 'phones. The cat will consult with you.

[Duggeh]

I had always intended to eventually upgrade my speakers to Quads. Either the dynamic 21L or the ESL63 if I could find one for a low enough price. This has been my long term plan in upgrading every since i very first got into hifi as a hobby. It faces serious reconsideration because of the Precide Aulos speaker. Could we get a more gratuitous shot of your AMT speakers? Nice cat too, clearly a feline with taste.