ESS AMT Monitors, refurb

[AudioLapDance]

ESS AMT Monitors (Heil Air-Motion-Transformers), refurb

Hey all,

I inherited a pair of ESS AMT Monitors with "the great" Heil Air Motion Transformers! Wow, I'm just blown away by the quality and workmanship. Oh and they're a bit flimsy ... Nearly busted my hump carrying them to my car and 2 story walk-up appt. by myself!






Oh you poor thing, all dusty ... and that's dust that came through the grill cloth! Nasty, ... and smells like Old Man.

Having trouble finding specs, manual, xover schematic, etc ...

Here's good ol' HiFi Engine - Owners and Service Manuals

ESS Monitor Manual - Loudspeaker System - HiFi Engine



Description
Powerful in it's sonic delivery, tall and stately in appearance, the AMT Monitor represents the utmost perfection in ESS's superlative AMT series.
The AMT monitor effortlessly unleashes thundering crescendos with great force, yet deftly reveals the most subtly detailed musical tapestries.

Specifications
Type: 2 way, 3 driver loudspeaker system
Frequency Response: 30Hz to 23kHz
Power Handling: 375W
Crossover Frequency: 1000Hz
Impedance: 5Ω
Bass Radiator: 305mm cone passive
Bass: 305mm bextrene cone
Tweeter: heil air motion transformer
Grille: black, brown
Finish: walnut veneer
Dimensions: 997 x 397 x 403mm
Weight: 47kg

Wait ... 997mm x 397mm x 403mm is ... 39"x15"x16" and 47 kg is ... 104 lbs. No wonder I almost busted my hump!!!

It was sooooo worth it!

So here's the Great Heil (all cleaned up)







The 12" passive radiator just ... dissolved! All that's left is the Styrofoam disk!

So, it seems like there were a few versions of the Monitor:

from "L7" at ESS AMT Monitors - Page 4 - AudioKarma.org Home Audio Stereo Discussion Forums

I guess it goes without saying that when the crossover says AMT MONITOR that one would surmise they are AMT MONITORS.
Not trying to be the fly in the ointment but hey...
Four unpublished revisions took place on those AMT MONITORS. None of these four were labeled anything other than, AMT MONITOR.
Early versions were with silver AMT units, metalized capacitor films, bextrene woofer cones w/ open cell foam surrounds, and .75in styrene disc radiators on the aluminum rings w/ the same suspension.
1st mid-build revisions came with flat black AMT units, bextrene woofer cones w/ rolled-edge treated surrounds, and .5in styrene discs w/ open cell foam suspension.
2nd mid-build revisions incorporate a huge change to the radiator, they were made to reflect the same outer rolled-edge suspension of the bextrene woofer and updated to a conical bextrene passive. When this radiator was introduced, it attached to an entire cast woofer frame (less the magnet and motor structure) obviously. The inner coil area behind the dual dustcaps was sealed up with an inverted pulp disc.
Final build revision on the AMT MONITOR came circa 1979 when they utilized the SBR (styrene butadiene rubber) half-roll suspension on both the bextrene woofer and conical bextrene radiator. This final build was in production during the outphasing of the 1B towers hence the SBR suspension changeover, which the 1C line of towers took on exclusively.
Hope that helps some confusion on the whole "MONITOR" thing ESS did lol... not to be confused with the entirely different builds of the AMT3 and the AMT1AM which were housed in the identical footprint of 15.75x15.75x39.5 inches respectively


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

Hmmm,

Mine is the 1st version with the simple passive radiator: just foam surround and 0.75" Styrofoam circle (or is it the 2nd because it has the flat black Air Motion Transformer--AMT?) I'll need the replacement kit, it's:

PART# ESSPR-12 $28.95 usd (12")
ESS Laboratories USA (Replacement Passive Radiators at bottom)

Also available at

http://www.parts-express.com/home.cfm?CFID=6555147&CFTOKEN=72535094

Official Speaker Repair Site - Orange County Speaker - Home of GLS Audio

Simply Speakers - Official Speaker Repair Page - Speaker Parts and Repair Service

Not sure if these are "official" ESS ones but they're the best price:

Official Speaker Repair Site - Orange County Speaker - Home of GLS Audio 12" or 10" Passive Radiators (choose size)


Then maybe later I'll upgrade to the more advanced passive radiator: speaker without voice-coil (cone passive).

ESS Factory Replacement Passive Radiator, 689-12P


I've been listening to them (even with no passive radiator: no deep bass and a bit 'boomy') non-stop for 3 days!

Yesterday, I was walking by and ... the next thing I know 2 hrs had gone by! Like some sort of time warp!

Here's pics of the xover and the back panel:








Anyone know where to get official stats, manual, xover schematic?

I've emailed Ricky "Rico" Caudillo at Ess (ESS Laboratories USA) and will post his reply.

Oh and it looks like Nelson used to work on the 10" woofer version at (Electro-Static Sound) ESS in Sacramento way back when he was just getting going in audio!

Thanks and cheers,
Jeff

 

[puppet]

Looks like the same frame as their "rock monitor" ... that's the one NP worked on. Dual 10's w/6" mid.

The configuration you have could use the amt 1b xo. same/same 12" w/12"PR and a 1k xo point. Don't have a schematic for it though.

 

[AudioLapDance]

All hail The Great Heil!

Thanks puppet,

You're right, they look similar: Monitor and AMT 1b and ...

Lots of AMT 1b stuff over at audiokarma:
ESS AMT-1b Crossover - AudioKarma.org Home Audio Stereo Discussion Forums

Repost here SVP!

All Hail the Great AMT Heil!

 

[kidcoma]

Hey, I just picked up a pair of these myself - first version as well. Sound fantastic, but have some issues with the veneers and one of the grill supports at the top is busted - looks like you're missing one entirely! I recapped my friend's AMT 1b's a few months ago - I was expecting to see the same crossover which has two 33uf caps, but also two 10uf caps. I haven't cracked mine open yet; do you happen to know what value the remaining cap is?

 

[dhaigh]

Anyone know which wires go where?

This week I picked up a pair of AMT – 1a tweeters with the crossovers. The speaker cabinets had been damaged beyond repair in a move 13 years ago. The owner had remove the tweeters and then cut the tops off of the cabinets. So now what I have is the top of the cabinets with the crossovers and the tweeter separate from that. I made a diagram of the physical crossover lay out. But I don't know which wires go where. The back of the tweeter has a purple wire and a light blue wire. I would assume purple goes to purple.

 

[el seven]

Hey all,

Having trouble finding specs, manual, xover schematic, etc ...

The 12" passive radiator just ... dissolved! All that's left is the Styrofoam disk!

So, it seems like there were a few versions of the Monitor:

from "L7"

Hmmm,

Mine is the 1st version with the simple passive radiator: just foam surround and 0.75" Styrofoam circle (or is it the 2nd because it has the flat black Air Motion Transformer--AMT?) I'll need the replacement kit.

Then maybe later I'll upgrade to the more advanced passive radiator: speaker without voice-coil (cone passive).

Anyone know where to get official stats, manual, xover schematic?

Thanks and cheers,

Jeff

Hi Jeff - this is L7. (obviously!)

I wouldn't recommend the cone passives for your towers. Stick with the flat radiator as the suspension employed in the active woofer is too stiff for a conical drone.

 

[erik777]

Your heil tweeter needs to be time aligned.

 

[ATatum]

ESS AMT Monitors (Heil Air-Motion-Transformers), refurb

Thanks L7,
For the explanation re choosing PRs for the AMT Monitors. The general answer I got was stay with the flat PRs for the Monitors. Some of the later AMT monitor (4th generation) used the cast frame PR, but I think the same woofers. This suggested that some other variable was in play. Dont know if it was the box, XO, or maybe used an updated woofer, although it seems most used the 12" Bextrane woofers.

Since there are no specs for the various flat PRs, I was wondering how they could all be "optimal" for all ESS AMTs using 12" woofers.

Here are specs for the cast frame PR.

ESS 689-12P 12" Cast Frame Passive Radiator

Specifications: • Fs: 18 Hz • Vas: 4.44 cu. ft. • Qms: 2.30 • Cms: 0.31 mm/N • Mms: 250 g • Rms: 12.4 kg/s • Sd: 535.8 sq. cm. • Xmax: 11 mm • Dimensions: Overall diameter: 12-3/8", Cutout diameter: 11-1/8", Depth: 3-1/2".


I am refurbing both the AMT1b and the original AMT Monitors. Over the years I have mixed and swaped the parts and now have parts of 2 different passive radiators that are somewhat different. Both have white plastic weights, but some are thin and weigh 23.6g and some are thicker and weigh 47.2g. I figure these may have been used in different radiators with differing foam surrounds.


Asked by: Tatuma - 8/27/2015
A: The new units weigh 79g which is correct for either model. ESS used different manufacturers for these parts over the years and their quality control was not always the best. You should replace them to match for best performance.
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Answer provided by: Simply Speakers (8/28/2015)

ESS Speaker Passive Radiator Kit, 12" Speakers, ESS AMT-1A, 1B, 1C, 1D, PASK-12

ESS Factory Replacement Passive Radiator, 689-12P


I am pretty much done with recapping the original crossovers, by just replacing the old caps with Dayton audio grade MPT 5%, and the square power sand resistors with low inductance wirewounds.

I have the flat 1/4" PRs in the AMT1bs, and I have the aluminum frames for PR repair, if I just want to update the flat PRs. So I can just swap them back into the monitors, and do some listening tests. I still have one of the Monitors with the original XO with the old caps, so I can still do a comparison, changing only one variable. I

I also just happen to have a couple of the original Bextrane 12" woofers, that I think I got , as a "bonus" with the Monitors, with the only problem that they have infinite resistance. I was thinking about trying them as PRs in the Monitors, until I get the definitive repair.

I guess any differences will be the degree of damping, but I have never done any woofer damping measurements. Any suggestions about the usefulness of such measurements? I am asking as the flat disk PRs should be easy to change the disk weights, to tune to the box, but I am unsure about how to tell underdamped from overdamped, except by just adding more weight.

I have seen a discussion of using drivers as PRs, and adjusting the compliance by adding resistance to the voice coils, but since mine already have that perfect infinite resistance, further resistance is futile!

Thanks for all your help while lurking, I enjoy this site very much, but a lot goes over my head.

I also have