AMT 3 & 6 Clones & Variants

[Hannibal Selector]

Hey all, this is my maiden voyage posting on any audio forum, aside from a
minor response or two.

ANYWAY,
I'm a Heil freak, and after reading lots of forum postings here & @ A-K, I'm
giving serious thought to building either a clone or variant of the Rock Monitor
3 - (probably using Eminence 1040 SF's and Alpha 6's) - or maybe a 6 Pro
(with added cone "transition" drivers). I do have a few big Heils and piles of
amps and active x-overs for the R&D stage, and will stay with bi-amping or
triamping the final product.

?'s I've yet to see answers to regarding the AMT Rock Monitor 3 are:
A) What are the dimensions of the enclosure, port, and mid-range chamber tube?
B) With the ported version being overstuffed to the point of acting somewhat like
a sealed box, does anybody know the actual bottom end roll-off characteristics? Even with the "tightness" advantage of sealed, I don't much like the "slow death" roll-off of it, and prefer a 3rd-order or sharper drop-off in the 35Hz neighborhood.
C) Where can I find a detailed description of PRECISELY how (and with what
material) to stuff the cabinet and the mid driver tube to function as ESS originally intended?
D) Some ESS litereature describes that un-vented mid driver enclosure tube as a "transmission line". Which almost seems as if they're trying to say that
it's timing backwave reflection back into the cone to augment what the front
of the cone is doing. Not sure I buy that. My guess is it's real function is to just deaden as much of the backwave as possible. Any opinions?

Regarding the Pro 6 I have just one question at the moment:
With all the benefits of the horizontal array of 4 Heils, how much, if any, does it
smear the side-to-side imaging presented to the "sweet-spot" listening area, as
compared to a vertical driver or array?

If anyone here can provide me with these answers or directions to where I can
find them, I would be very grateful.

Now going a little OT, I speak pro audio more fluently than audiophile, and the
term "fast" is new to me. Can I assume that's just shorthand for "good transient response"?

Thanks again, y'all.

[wintermute]

Hi Hannibal, and welcome to diyAudio!!

I'm not going to attempt to answer any of your questions but your interpretation of fast sounds plausible to me

Tony.

[Hannibal Selector]

Maybe I should have posted this in Planars And Exotics? My apologies to the
moderators if Introductions was the wrong place to post my very first ?'s.
Should I try to re-post to Planars And Exotics myself? Or leave well enough
alone? Or what?

[wintermute]

and magically it moved

I didn't know what sort of speakers these were, but I'll trust that this is the right section, and more likely to get some views

Tony.

[Hannibal Selector]

Ah, thanks for the course correction wintermute, it is appreciated.

[decooney]

Hannibal,

Did you start or finish your AMT clone project?

I use to work at ESS in 1983, and recently started doing some research to find out that LOTS of people are experimenting. Seeing variations of AMT ribbon type tweeters in all sorts of old and new speakers coming out. Had no idea. If you keep looking and looking, lots of "AMT" stuff out there. All ideas and variations. Stirred my curiosity.

I'm considering doing a small mini monitor with a pair of Heil s and some sort of light weight 7" or 8" woofers. Not finding any good passive crossovers to use yet. So, I guess I'm sort of looking at using an electronic crossover, smaller cabinet with the heil on top as a a mid-high speaker with Heils bolted to the top of the mini monitor - not sure yet. I will try to pair these with my dual 12" subwoofers and see how it pans out.

Any updates on your project or findings?

[Hannibal Selector]

Hey decooney, what's up?

Somehow I didn't see notification of your response coming in. I haven't started
on anything, still doing legwork - lots of legwork. I want to build this setup right
the 1st time, so lots of prep is OK. That, and I just can't get an answer ANYWHERE
to my original stuffing question. Now I've wandered into the TL concept and am
researching that too. Now THERE'S where I would love to pick your brain about the
AMT 3 Tower ESS made that was a T-line cab. I wouldn't mind building a clone
of that with a mid-bass driver shoehorned in. If you have recall or a source for
the dimensions/volume/stuffing, etc., of that thing, I'd love to know of them.

If you enjoy seeing what people have on their mind regarding AMT's, you might be better off at AK.
A fair bit of action there. I've posted my questions in multiple places @ DIYA and gotten pretty much nothing but silence so far. Planet 10 here has done some interesting things with them, and I THINK it's in DIYA Planars and Exotics that some crazy European (Scandi, I think) has been documenting his work on his own home-brew super-size AMT's that are made to reach real deep. If I can dig up the link, I'll post it here. There's another link to a sweet 'site of some very nice scans of all the old ESS literature. If you haven't seen that, I can re-post that here too. I got a thread going at AK right now debating TL vs other type cabs as to what's best suited to park under the big Heils. Also at AK there's been some good recommendations on finding mid-bass drivers quick enough to integrate well with
Heils - and where best to cross them over. Echowars and Automojo @ AK cover some of that.

Nothing wrong with active x-over if you've got the amps. Passives can be a lot of
work if you get beyond your basic 2nd-order biz - and you still don't get that
amazing articulateness and projection you can w. bi-amp/tri-amp stacks.
OR the sweetness of being able to just dial something back if it's too hot -
instead of tweaking resistors into a passive network.
Have you scoped out Marchand for that? I've got a DBX I mean to use to dial
things in, at which point, I'm probably going to order a Marchand.

[Hannibal Selector]

Pasted from elsewhere, enjoy:

"BTW, for any AMT/ESS junkies here who haven't run into this
awesome gallery of ESS ads, here's a link I first saw posted by
Cactus Bob @ AK:

* Michael Otto's Archiv * - ESS_Lautsprecher

Clicking a thumbnail gives you a not-so-big shot of the ad, but click
again and you get full-size."

Another link on the way, couldn't get it pasted into this posting.

[Hannibal Selector]

Here's the AK thread I was talking about:

TL vs Overdamped BR - Opinions? - AudioKarma.org Home Audio Stereo Discussion Forums

Wade on in and enjoy the mayhem.

Meantime I'm trying to root up a couple more links you'd likely find
interesting if you haven't already been there.

[decooney]

HS,
I saw that Hi Fi Classic site before with pictures of all the various speakers from back in the day. What a cool site. I knew some of the lines but not some of the early version AMT1 products. When I was there, the AMT-3s were winding down and even though I saw at least one AMT-6, never saw one come up on the line during my short time there. Most of what I've learned since has been on the internet just like you guys. As for damping, I would just experiment a bit. You can start with too much and keep taking it away until it sounds worse just to get some prelimnary ideas . I had a set of AMT Monitors and AMT 1Cs a few years later. They were cram stuffed but did have a notable amount of stuffing on the sides. Both models were nice speakers. The AMT Monitors were a tad more directional with sides as compared to the open depole effect of the 1Cs. Always wanted to hear the Transar ATDs in person , and never saw them or got that chance as it seemed much of those production runs were sort of offline and not happening. From what I learned later, I missed the tail end of what many refer to as the "old ESS". I probably would have liked working there even more so when the marjority of the originals were there.

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Yesterday I did find a decent thread on some AK members doing some fairly persistent trial and error research working to develop a suitable crossover for custom AMT builds using the Great Heil. The main guy building the speakers did something similar to what I was thinking, although he started with a 2-way and ended up with a 3.5-way after trying a few different driver configurations. He posted a copy of his crossover too. If you read to the end it seems like he is still wondering if he might even revisit and tweak it some more. I'm not sure I want to commit a few months of R&D to it without all the right tools, software, and hands listening testing. He already moved through one set of drivers to another sort of paving the way for others to pick up and go from there if they have enough motivation to carry it further forward. Still checking around.