AMT 3 & 6 Clones & Variants

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Hannibal Selector

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Joined 2011
#1
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.
 
#6
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?
 
#7
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.
 
#10
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.

----------------------------------------------------------------------------

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.
 
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#11
HS,
I would definitely do some trial & error checks on your own to see what sounds best on the stuffing. As I recall, none of the AMTs on the line were overly stuffed but most of the internal wood was covered. Never got the pleasure to work on the AMT-3s or 6s. By the time I got there I later learned most of the original ESS family was gone by then.


Here is a another interesting thread I'm participating on over at AK. its regarding AMT crossover development. Lots of trial and error going on over there.
My Great Great Heil DIY Speakers - AudioKarma.org Home Audio Stereo Discussion Forums
 
#12
"They were cram stuffed but did have a notable amount of stuffing on the sides."
"As I recall, none of the AMTs on the line were overly stuffed but most of the internal
wood was covered."
*
Well, that's more than anybody else has told me so far. Thanks for that. I'll just
have to keep checking here, as my reply notifications are still not coming in.

If that's the AK thread I think it is, I was following it some time ago, maybe
it's time to eyeball it again. I believe I've already got it bookmarked.

Seriously though, thanks for telling me what you can about the stuffing. Every little
bit helps.
 
#13
HS, reading your reply in quotes I jus want to make a clarification. I do not recall them being overly stuffed. However there was a sufficient amount of stuffing covering the sides on the inside. Without specifics, you can try loading them a bit, and then start pulling some out, incrementally. I sort of use my ears as a guide and see if there is a way to discern what is too much, and what might be not enough. Good Luck.
 
#14
Hannibal,

All the ESS I have seen have been stuffed with material. The type varied with the years the latest was Dacron.
I have:
an AMT1b: Stuffed at 80%
an AMT 1e Monitor: Stuffed as well (Dacron)
and I saw an AMT 1 (transmission line) which was completely stufed as well.

From my experience I do believe that the AMT 3 is the way to go but may be not exactly as it was done originally. I would use indeed 2x 10 inch bass drivers and I would try to pick a mid range driver that goes up to say 1500Hz (may be the Seas that was used recently in an AMT speaker). I noticed that the Great Heil is not very good in the 1K - 1.5K range (female voices are colored: "duck" sound).

One thing I did and Like is to use 2 Great Heils (in //) per speaker, for me it sounds better (obviously you have to correct the xover otherwise you just hear medium)
 
#15
cdfr and decooney, much thanks. Your input definitely gives me a clearer idea of
where to begin. I wanted to start off as close to OEM as possible and tweak from
there. I wanted the clearest picture possible of what the designers originally had in
mind when going from sealed to ODBR with the same cab volume, and to make any
mods from a well defined starting point.

cdfr, I definitely agree with you about updating how the original AMT 3 implements
the mid. I always thought it was weird to use a mid and yet cross the Heil in so low.
I actually have 2 pair of Heils I want to use, so we're on the same page there, too.
I will probably experiment with tipping the upper Heil back about 40 degrees. I'm
thinking that will both heighten the image for a sitting listener, and also improve the
sound for listening off axis and while standing/walking around. As for crossover, I just
tri-amp anyway so I don't have to tweak for the impedance difference. Active
crossover - the lazy man's best friend! :emoticon: Nice too that I can always dial back the paired
Heils if need be. I might engage in a little "amp-rolling" on the Heils, too.
At least as budget permits, anyway.
 
#16
Sure thing Hannibal. If I've learned anything experimenting with speaker builds myself, I let the listening to the sound itself be my guide. Right now I'm working on a plan for a design to use the Heil with two smaller mid-woofers instead of a large 12" woofer and PR. It was not until I bought my Totem speakers and paired them up with dual 12" subs I made did I realize what I was missing in audio listening and home theater. Although I liked my former AMT Monitors and AMT 1Cs, and they did have a unique sound, however those 12" drivers were nice but they just did not capture the presence and sound stage for me. Perhaps this is why many here on this site perfer the AMT3s over many of the other AMT models. I hope to pair up the Heils something closer to the ESS 450 Connoissuer but leaving the back of the back of the Heil exposed in a dipole configuration like the original AMT monitors were. If I can cram two 7s and a Heil together keeping it at ear level just above my subs, I might try it this spring.
 
#17
@decooney:_________________________________________________
"Sure thing Hannibal. If I've learned anything experimenting with speaker builds myself, I let the listening to the sound itself be my guide."
*
One more reason I love active crossovers. Tune on the fly, less work, unlimited
options, AND you get A/B comparisons instead of A... (long pause) ... eventually... B.
__________________________________________________________
"I hope to pair up the Heils something closer to the ESS 450 Connoissuer but leaving the back of the back of the Heil exposed in a dipole configuration like the original AMT monitors were. If I can cram two 7s and a Heil together keeping it at ear level just above my subs, I might try it this spring."
*
...And it might just cost you less than 14 grand :rofl:

-------------------------------------------------

Here's something I'm curious about, that you might have the knowledge to
help me with - just what do you look for in a driver's T&S parameters to
get an idea of it's "speed"? A couple things I've read said that only looking at
Mms is not the whole story, but they didn't go on to specify what else to look at.
Strangely enough, for all the years I've spent dealing with audio, I'm quite the noob
when it comes to T&S theory. But obviously you want something quick to keep
up with a Heil. I have good driver recommendations for an AMT 3 clone, but if I decide
to go outside that model, it would be nice to know how to choose my drivers.
Any thoughts on the subject?
 
#18
HS,
sorry, unfortunately I don't for the AMT3... I'm learning more here about those than ever before. I may pull out the old electronic crossover and try it for sure and plan to farm out my crossover to a real pro, or someone who can get me a lot closer than trying myself and knowing I'm a bit over my head in this area. There are some interesting reads on this site about the 3s. I'm just doing my research with the hopes like everyone who builds speakers - to be able to have some luck with all the formulas, theories. Good luck on your project.
 
#19
@decooney:______________________________________________________
"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... 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."

"I may pull out the old electronic crossover and try it for sure and plan to farm out my crossover to a real pro, or someone who can get me a lot closer than trying myself and knowing I'm a bit over my head in this area."
*
If you're looking at passive, it seems like automojo @ AK has done a lot of
geeking the passives on his '3's, if you haven't seen that already. Also, Solen in Quebec has
some pretty sweet coils that nobody else seems to carry. Good caps and other toys, too.
If you're looking getting at a better active once you're dialed in, have you checked out
Marchand Electronics' website? They have a rep for using all premium components throughout
and you can get pretty much any configuration you want - balanced inputs, you name it.
They even offer slope options, IIRC, though their standard is 4th-order Linkwitz-
Reilly. They seemed to offer the best menu of features compared to all the name
audiophile offerings - and for reasonable prices (for what you get).

I remember building bilateral low-tech 2nd & 3rd order passives, look up
component values, buy parts, apply solder... Now it's series this, Zobel that,
BSCC the other... Now THAT'S over my head. Good luck on your project,
too.
 
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