ESS AMT 3 Rock Monitor find, from original owner
- Thread starter G871
- Start date
The AMT 3 used a higher pleat diaphragm then other AMT’s-15 I think
So keep them fused!
At least from what I’ve seen they look different than other diaphragms..clearer..
As a side note- Rick from ESS..isn’t even aware of this..
That’s why I try to discourage people taking his advice on any vintage ESS restoration....
Well at least AMT3’s...he knows very little.. and most of that is totally in accurate
It may be that there’s not enough documentation for him to be aware of these things from ESS company archives...the AMT3’s... from when I bought my first pair years ago there’s always been a lack of accurate info on these... there were a number of different configurations...
He is stuck on his 2 ways and headphones...good for him..
I don’t really have a problem with it.. he should concentrate on the new stuff.... because frankly he’s not willing to really learn anything about AMT3’s...
So keep them fused!
At least from what I’ve seen they look different than other diaphragms..clearer..
As a side note- Rick from ESS..isn’t even aware of this..
That’s why I try to discourage people taking his advice on any vintage ESS restoration....
Well at least AMT3’s...he knows very little.. and most of that is totally in accurate
It may be that there’s not enough documentation for him to be aware of these things from ESS company archives...the AMT3’s... from when I bought my first pair years ago there’s always been a lack of accurate info on these... there were a number of different configurations...
He is stuck on his 2 ways and headphones...good for him..
I don’t really have a problem with it.. he should concentrate on the new stuff.... because frankly he’s not willing to really learn anything about AMT3’s...
jcidave
Well-Known Member
Back in the early days of the 70's all the Great Heils used the same diaphragms. They all had more pleats at that time. However, ESS started modifying the diaphragms right away as they started to get failures. First they put 3 rows of silicone across the pleats to keep them from moving too close to each other. Once they heated up, they could stick together, and that would be the beginning of a failure. My attached picture of spares shows one of the silicone rows diaphragms at the bottom right. This diaphragm has 17 pleats. All the others have 12 or 13. You may also see that the 17 pleat dia has the wires on either side of the frame. All the others have the wires paired together on one side of the frame. Soon they abandoned the rows of silicone and went to the bridal veil covering. During my brief tenure at the ESS dealer store I worked at I saw both modifications and I was out of there by the end of '78. At one point decades later they also went to using Kapton as the substrate. You see the 2 yellow diaphragms in the picture. When I asked Ricky about Kapton, he balked and just said it was too stiff. Funny how all the other makers of AMTs seem to be using it. It supposedly can handle higher heat than other substrates. If anybody has diaphragms with no silicon rows, no bridal veil and wires on either side of the frame, you have a very old original diaphragm. I have several pair of them and they work fine. I'm not replacing them.
The AMT3 was $435 MSRP each when I purchased my pair in 74 or 75. Got 2 for the price of one with free shipping. That was the salesman's deal.
The OP's 3's are different than mine. I only have a single 2 amp fuse for the whole system. He has a 1.5 and separate 1 amp for the Heil. I don't know if the Heil fuse is a factory change or a personal modification. His upper bass driver is different than mine and installed differently. I think the 3 is an outstanding speaker. Liked them better than anything else we had in the store. Pic is upside down. don't know how to fix.
The AMT3 was $435 MSRP each when I purchased my pair in 74 or 75. Got 2 for the price of one with free shipping. That was the salesman's deal.
The OP's 3's are different than mine. I only have a single 2 amp fuse for the whole system. He has a 1.5 and separate 1 amp for the Heil. I don't know if the Heil fuse is a factory change or a personal modification. His upper bass driver is different than mine and installed differently. I think the 3 is an outstanding speaker. Liked them better than anything else we had in the store. Pic is upside down. don't know how to fix.
G871
Active Member
Thank you all for your contributions and support! I will definitely be reporting back with what I think of the sound, with comparisons to my favorite speakers so far.
A little update.
I got all 4 woofers removed, along with some of the baffle. (For those of you who haven't heard, ESS sealed drivers in with black RTV silicone...and it likes to stick so well, that it takes wood with it)
Here's a pic showing one speaker with its polyfill (in a large contractors' garbage bag) and you can get a little glimpse of the woofer mounting surface that suffered a bit of loss. They really didn't lose too much, but I will be reinforcing with epoxy as Automojo has recommended.
Next up is the crossover. Turns out these are an iteration of the 3-coil 8 ohm woofer version.
Here we've got a 55mf cap (near bottom, by 2 coils), a 13mf cap (just up and to the left from the 55mf cap) and a 20mf cap. (very top left, on the terminal strip) The uppermost resistor is 10 ohm, and the other 3 are all 2ohm.
Each woofer measures 6.5-6.7 ohms and each pair is wired together. (pos to pos and neg to neg)
Next up - the transition driver. In the owners manual and brochure I got with these, it's stated that the transition driver is mounted in a "resistively terminated line which extends back into the bass enclosure." This refers to the 6" cardboard tube that houses the driver, going almost the whole depth of the cabinet. The ALMOST part is important - there is about 1/16" (about width of a fingernail) from the end of the tube to the back wall of the enclosure, meaning that the transition driver is allowed to vent in to the larger cabinet as part of the design. See here:
Notice that on the right of the picture, the end of the tube doesn't touch the wall. It's open at that end.
I've read multiple people talking about resealing their cabs, incuding the transition driver housing - but this tube is supposed to be left open at that end. So hopefully nobody has irreversibly sealed that!
Next is the cabinetry. These are built with double walls. So you have the outside cab, and inside that, there are additional walls nailed to the outer walls.
But, are these glued together? More importantly, are the outer cabinet walls glued together at the seams? I couldn't find anywhere where I could see those seams, because of the additional internal walls....I'm hoping there's glue/sealant somewhere I can't see, because the interior walls are certainly not sealed:
I'll probably lay a bead of caulk along all seams I can see before I button 'er back up.
Other crossover - same as the first, but with one red coil.
And, a shot at the end with a peak at one of the Frazier Sevens that are taking a turn on stage for a while.
A little update.
I got all 4 woofers removed, along with some of the baffle. (For those of you who haven't heard, ESS sealed drivers in with black RTV silicone...and it likes to stick so well, that it takes wood with it)
Here's a pic showing one speaker with its polyfill (in a large contractors' garbage bag) and you can get a little glimpse of the woofer mounting surface that suffered a bit of loss. They really didn't lose too much, but I will be reinforcing with epoxy as Automojo has recommended.
Next up is the crossover. Turns out these are an iteration of the 3-coil 8 ohm woofer version.
Here we've got a 55mf cap (near bottom, by 2 coils), a 13mf cap (just up and to the left from the 55mf cap) and a 20mf cap. (very top left, on the terminal strip) The uppermost resistor is 10 ohm, and the other 3 are all 2ohm.
Each woofer measures 6.5-6.7 ohms and each pair is wired together. (pos to pos and neg to neg)
Next up - the transition driver. In the owners manual and brochure I got with these, it's stated that the transition driver is mounted in a "resistively terminated line which extends back into the bass enclosure." This refers to the 6" cardboard tube that houses the driver, going almost the whole depth of the cabinet. The ALMOST part is important - there is about 1/16" (about width of a fingernail) from the end of the tube to the back wall of the enclosure, meaning that the transition driver is allowed to vent in to the larger cabinet as part of the design. See here:
Notice that on the right of the picture, the end of the tube doesn't touch the wall. It's open at that end.
I've read multiple people talking about resealing their cabs, incuding the transition driver housing - but this tube is supposed to be left open at that end. So hopefully nobody has irreversibly sealed that!
Next is the cabinetry. These are built with double walls. So you have the outside cab, and inside that, there are additional walls nailed to the outer walls.
But, are these glued together? More importantly, are the outer cabinet walls glued together at the seams? I couldn't find anywhere where I could see those seams, because of the additional internal walls....I'm hoping there's glue/sealant somewhere I can't see, because the interior walls are certainly not sealed:
I'll probably lay a bead of caulk along all seams I can see before I button 'er back up.
Other crossover - same as the first, but with one red coil.
And, a shot at the end with a peak at one of the Frazier Sevens that are taking a turn on stage for a while.
G871
Active Member
Which model Ohms are those?
Hi cidave, thanks for the informative post. Looks like my diaphragms are the original 17 pleat version, with no silicone. Does the silicone have any adverse effects on the sound/capabilities of the AMT? Wondering if that's something I should consider doing, to protect these original diaphragms.
Also, the fuse setup on these is factory - the owners manuals I got with them mention the 1A and 1.5A fuses.
However! The spare fuses are all (4) 2A! The seller was the original owner, and she said that these are the original spare fuses that were given to her with the speakers. So, I wonder if they'd moved to manufacturing and selling the 2A fuse setup but still had this pair of older AMT-3's left in the store to sell, and nobody noticed or knew, so the customer was given the 2A's...?
And, I'm curious cidave - what other speakers did you have in the store??
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G871
Active Member
Whoa. Very cool. I'll be keeping an eye out for those.
jcidave
Well-Known Member
G871: I would not attempt to modify your diaphragms. I would not boost your treble or midrange and be certain to have lots of clean reserve power if you want to play it loud. Again, my originals have lasted all these decades. Trying to remember back all the speakers we had in the store: Altec, JBL, AR, KLH, Dynaco, McIntosh, B&O, Pioneer, Yamaha, Phillips, Nakamichi, BIC. We had a bunch of ESS out for demo at all times including the Tempest bookshelf series. All the ESS had one version of the Heil or another. Because of the Heil, the ESS line had the most consistent sound from bottom to the top of the line. No other line we sold could deliver that performance.
To be fair, there are lots of other great speakers owned by AK members that I was never able to compare to the ESS.
Your fusing is confusing to me. Not sure if you have a super early version or a very late version just prior to the changeover to the AMT1A Monitor.
To be fair, there are lots of other great speakers owned by AK members that I was never able to compare to the ESS.
Your fusing is confusing to me. Not sure if you have a super early version or a very late version just prior to the changeover to the AMT1A Monitor.
In my 4 coil set up- the mid and Heil are fused separately, not together.
The top Heil fuse holder and location is indentical to OPS speaker pair
Op's mid is a Peerless.
My 4 coil used a 4 ohm Peerless-it lacked the 'bars'-only had 2 screws with the heads overlapping the speaker frame, along with silicone.
All the Peerless had rubber surrounds, and Alnico magnets.
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Note 8 resistor Zobel- this model has 4 ohm woofers and 4 ohm Peerless mid
Doesn’t surprise me about Rickey-all about the profits...
Thanks for clarifying pleat construction. Original 3 diaphragms, from my 2 pair, and clearly physically different. And from current, and past replacements I have.
One member here-can't recall his handle, worked for ESS, and mentioned the differences-apparently the 17 pleat has a higher DB output. So if one goes south, you would need to probably replace both for a proper match.
Interestingly he echoes Rickey's issues with vintage stuff he doesn't like too acknowledge...among other things...
Doesn’t surprise me about Rickey-all about the profits...
Thanks for clarifying pleat construction. Original 3 diaphragms, from my 2 pair, and clearly physically different. And from current, and past replacements I have.
One member here-can't recall his handle, worked for ESS, and mentioned the differences-apparently the 17 pleat has a higher DB output. So if one goes south, you would need to probably replace both for a proper match.
Interestingly he echoes Rickey's issues with vintage stuff he doesn't like too acknowledge...among other things...
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jcidave
Well-Known Member
Automojo: Interesting that your fuse config is like the OP's. Same mids, but you have a 4 coil and he seems to have a three. Obviously, production changes were happening all the time. I believe it was always all about the profits.........even before Ricky showed up decades later. It would seem to me that you and the OP both have earlier configs than my 2 pair.
As far as the midtube goes-I can't imagine why you would want it leaking into the main bass cavity-not good!!
That's why many speakers run close back mids-among other things...
The reason they didn't seal it was because of cost-with all the stuffing-it was close to being sealed.
The AMT3's cabs are not precision-they got things close enough, more or less...
The mids are designed to work in a sealed enclosure-I sealed all mine.
That's why many speakers run close back mids-among other things...
The reason they didn't seal it was because of cost-with all the stuffing-it was close to being sealed.
The AMT3's cabs are not precision-they got things close enough, more or less...
The mids are designed to work in a sealed enclosure-I sealed all mine.
Sure, Nelson Pass, or so the story goes had a hand in these early 3's...
My first pair is a later version 3 coil, foam mid, one fuse for mids and Heil.
This 4 coil pair now sports this crossover, different mid and woofers...
Also a full ceramic interior treatment, foam, felt lined walls and bracing between the woofer opening, and woofer, midtube opening..
The speakers now are about 30 lbs heavier then stock...
Note new style switch-Mills resistors, 12-14 gauge wire...new fuse holders and input terminals..custom wound 13 gauge bass coil...
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If you like the stock AMT3's....you love the final MOJO version...
Still musical and enjoyable like the stock AMT3's, just more even in the bass, less distortion and compression at higher volumes..and a few db more efficient. The slight midbass/bass veil no longer exists..
Like all AMT's, they probably aren't the most accurate speaker around, but they are just so fun and enjoyable to listen to...more then any other speaker I have run across..
Kinda akin to the Divore's speakers everyone at Stereophile seems to be so in love with..except the measurement guy...
Efficient, musical, fun and enjoyable to listen to, speakers aided by ear tuning, not just a measurement..
That's why I think Ricky is really missing the mark here...he really has no clue!!
Like these Stereophile guys, rediscovering the soul of music, instead of the weird direction high end speakers went for awhile...
That's the nice thing about hindsight, and new technology...
You can take a great design, with a few relatively small draw back, and really improve it, with out having to start from scratch..
With the AMT3, it starts with the Great Heil, second the transition driver-next to the heil, the key to making a true full range Great Heil speaker, without holes in the frequency response, i.e. you can hear everything at the correct levels intended, and third, two active highly efficient woofers-in a decent size, but not huge enclosure.
Regardless of Ricky's opinion-the 2 ways will never succeed, there is always a dip, and a absence of critical midbass-to lower midrange cohesiveness.
Still musical and enjoyable like the stock AMT3's, just more even in the bass, less distortion and compression at higher volumes..and a few db more efficient. The slight midbass/bass veil no longer exists..
Like all AMT's, they probably aren't the most accurate speaker around, but they are just so fun and enjoyable to listen to...more then any other speaker I have run across..
Kinda akin to the Divore's speakers everyone at Stereophile seems to be so in love with..except the measurement guy...
Efficient, musical, fun and enjoyable to listen to, speakers aided by ear tuning, not just a measurement..
That's why I think Ricky is really missing the mark here...he really has no clue!!
Like these Stereophile guys, rediscovering the soul of music, instead of the weird direction high end speakers went for awhile...
That's the nice thing about hindsight, and new technology...
You can take a great design, with a few relatively small draw back, and really improve it, with out having to start from scratch..
With the AMT3, it starts with the Great Heil, second the transition driver-next to the heil, the key to making a true full range Great Heil speaker, without holes in the frequency response, i.e. you can hear everything at the correct levels intended, and third, two active highly efficient woofers-in a decent size, but not huge enclosure.
Regardless of Ricky's opinion-the 2 ways will never succeed, there is always a dip, and a absence of critical midbass-to lower midrange cohesiveness.
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Porkloin
Oscar Heil Groupie
Hear-Hear! I have technically better speakers in the house, but that Heil is what I've referred to as more "organic" ad nauseum. They convey the nuance that breathes more life into a given performance and hence, a better appreciation of the content. One would instinctively think that the cloth half sphere of dome drivers would produce a more "oranic" sound than the robotic pleats, but they're mechanical by comparison.
My biggest beef with Ricky and present day ESS is the lack of a 3-way in their product line, which is a damn shame with the crop of modern full rangers that would make a great transition driver.
