ESS AMT 3 Crossover Schematic

My ESSs are 1978, with cast basket 12" woofers and 12" passives (identical without motor assembly), bextrene cones and doped-cloth surrounds, not really modern.

The Rock Monitor was introduced toward the end of the AMT Monitor run, my memory was that the twin 12s (active/passive) were replaced with twin 10s (active/active) and a midrange and a port? Apparently these are also steel?
 
I very much appreciate your input on this and helping me get out of this fog that I'm in understanding the lineage of this classic speaker. I wish I could remember the gentleman's name that called me yesterday from ESS, but he owns/runs the company as it is known today. He was apart of ESS in it's previous life before it went to sleep for 15 years or so and it seemed to me that he had a deep knowledge of what he was talking about. All that said, he was saying that there were a number of different types of speakers (woofers) used during the production of the Monitor series, one being the 679-1111 woofer. My confusion was that the one version that there seems to be the most information available calls for two 680-0010 8 ohm woofers in parallel, and my 679-1111 woofers are 4 ohm. For a brief time the variation that I have they were hooking the two active woofers in series but he is going to look through his archive of documents and verify that, and send me what he finds. The speakers that I got these woofers out of was from the ported type in closure which are the type that I'm trying to bring back to life.
 
Just to add there seems to be a ported enclosure and a sealed enclosure with the two active 10 inch woofer variation. This only adds to the confusion.
 
I believe that you are correct. At first I only knew about the sealed, and I didn't know if they are active/passive like the AMT Monitors or active/active.
The ported one when I first saw it I thought was a modification, not original. Since this series of speaker is (in my opinion) a really great tweeter with support from some cones below, it has many modifications and the tweeter is what most covet. Because of this I feel that there are many out there that are not the original configuration (and some might have added a port to an enclosure to update, some might be originally ported, I don't know). I'm guessing that the ported version was a design change later in the production of this series.

It does make sense that using a pair of matched 4ohm drivers they would put them in series to provide 8ohms and match the midrange and tweeter, you would not normally have a 4ohm woofer and 8ohm mid/tweeter.

I have probably talked with this guy also when I was researching surround doping, he was going to do some research when I got back to him with serial numbers (I never did but my Son who now has them did). The AMT Monitor series had several configurations also starting with an early heil and flat foam passive and paper woofer, going to black heil with cone passive, and finally my configuration with bextrene cone woofer and passive. The replacements available today from ESS are pulp cones.

I believe that the Rock Monitor was launched late in the production of this line and I do not know how much changed during their run.
 
This is like watching a couple of guys trying to figure out a hot chick with a multiple personality disorder. The AMT on top was an amazing invention that's still relevant to this day. It would be no tragedy to forget the haphazard, collection of parts that ESS cobbled together beneath it.
I would hope that Rick (Ricardo) would at least get a handle on the standardization issue with the modern versions as he sure as hell hasn't spent any time on innovation.
 
I guess the energy or wind behind this search is to keep everything authentic. I'm an old school guy that is just looking to keep everything stock. I get a lot out of driving myself nuts looking for this info that's out there. Every time I think I know a lot I come to find out that I don't, and I'm humbled.
 
I guess the energy or wind behind this search is to keep everything authentic. I'm an old school guy that is just looking to keep everything stock. I get a lot out of driving myself nuts looking for this info that's out there. Every time I think I know a lot I come to find out that I don't, and I'm humbled.
My worn out automotive analogy: Would you rather drive a stock '33 Ford or one with a 351 Cleveland, a modern MacPherson suspension and disc brakes?

BeforeAndAfter.jpg
 
MR_B from Canada.
I have 3 pair of the 3's.
After reading this thread, I went and checked, as I had never seen or heard of round magnet 10" in the 3's, only Alnicos.
One pair has one set of the round magnet, 680-0010, stamped on the edge of basket.
Thank you "On a Quest" and thank you AK. I would never have believed it.A6.JPG A6.JPG A5.JPG
 
This is the first time I've posted on anything but I like I said in the beginning I've been a long time miner of the wealth of knowledge that's out there on audiokarma much appreciate the feed back.
I really love these speakers, no exageration and in a way if it takes me a little longer to get them right no problem. The biggest question I had was paralleling the 680-0010 woofers and in another version hooking the 679-1111 woofer in series. It's a little odd that a Basic design would change that much.
 
Mr B,
If you still have the woofers out on the one set could you tell me the kind of crossover you have? I posted a picture of mine on this thread and was wondering if they were the same. If you can thanks, if you can't no problem
 
Your Pic is very dark, so I can't tell exactly.
It appears yours is the 3 Coil version. So is mine.
I believe it's for 8 Ohm woofers in parallel. Whether Alnico woofers or round magnet.
 
I think that the parallel arrangement is the 8 Ohm woofers with 3 coil X-over.
The series arrangement is the 4 Ohm woofers with a 4 Coil X-over.
Why?????????? Who knows.
I think AUTO stated this earlier.
All mine, 3 pair, have the 3 coil.
 
Mr B,
Thanks for taking the time to let me know. What you say cleared the fog a little bit on what I have. The Hiel tweeters and the midranges are the same between the two versions but the crossovers and the woofers are not. It looks like I need to make a trip up to Maine again and pickup the other cabinets and crossovers to make this work. Like I said, thanks for taking the time. I'll post some pics when they are done.
 
Here is a better picture of the crossover that are in the original cabinets. It's just a matter of finding the time to get back up to Maine and get the crossovers out of those cabinets to match up with the 4 ohm woofers I have in New Jersey. I'm pretty sure that the Heil tweeter and the midrange stayed constant through the different changes that they went through with the woofers, which I'm grateful for. Thank you all for all your help and input. Porkloin, just for my education, what drivers did you use in modernizing/improving your monitors. Thanks again Auto, Mr B, SaturationPt, Porklion for your help.
 
Here is a better picture of the crossover that are in the original cabinets. It's just a matter of finding the time to get back up to Maine and get the crossovers out of those cabinets to match up with the 4 ohm woofers I have in New Jersey. I'm pretty sure that the Heil tweeter and the midrange stayed constant through the different changes that they went through with the woofers, which I'm grateful for. Thank you all for all your help and input. Porkloin, just for my education, what drivers did you use in modernizing/improving your monitors. Thanks again Auto, Mr B, SaturationPt, Porklion for your help.
Quest,
Unfortunately, both woofers that were accepted as replacements for 10" ESS projects are now discontinued. The Dayton ST255-8 (pictured) was perfect for the project as it worked well within the cabinet volume with more drastic porting. The upper bass was not muddy and overbearing, so it didn't need a zobel network to compensate (per AutoMojo). It looks like Eminence, but I haven't found an actual Eminence model with it's specs. The Eminence 1040SF was also widely used, but alas, is discontinued. If you can find either on the used market, snap them up.
The Eminence Alpha 6a is the popular replacement for the transition driver. To my ear, it definitely needs an L-Pad as I've got mine turned half way down.

IMG_0180.JPGIMG_0178.JPG IMG_0174.JPG IMG_0176.JPG
 
Quest,
That looks like a X-over for 8 Ohm woofers. (3 Coil)
It doesn't look like any I have seen before, though.
Caps and sand cast resistors don't look original and there is no circuit board.
ANOTHER variation????????
 
Quest,
That looks like a X-over for 8 Ohm woofers. (3 Coil)
It doesn't look like any I have seen before, though.
Caps and sand cast resistors don't look original and there is no circuit board.
ANOTHER variation????????
I can only see three sets of capacitors (the bunch twisted together count as one). In order to have a 2nd order woofer leg, a 2nd order band pass, and a 3rd order tweeter leg, there needs to be four (sets of) capacitors. I'd be curious to see a schematic and a listing of the values of those parts. I'd also be curious as to how ESS incorporated that fourth coil into the mix.

Original for a pair of 8 ohm woofers - 4 caps, 4 resistors, 3 coils. See Automojo's schematic above.

IMG_0079.JPG
 
If you look back towards the beginning of this thread there is a posting from Lacrosplayer with a pic of the same crossover. I would really like to talk with him to see what woofers were in his cabinets. Sadly I've heard once from ESS and then nothing, I'm getting to think regretfully that might be a dead end. I'm going to hit my brother up in Maine tomorrow to see if he can send me a few pics of the crossovers inside the cabinets I left with him, hopefully a few more pieces to this puzzle will fall into place. I know I sound like a broken record, but I really appreciate the help through all these postings of mine
 
3-coil crossover traces.
The other picture is the final refinement on the port to an a on my first pair.
My second pair with a hardwired custom crossover will follow the same training method.
Yes... it looks odd work report wire sticking out, but I'm not gonna put on a new back panel. Boner thinking the port flyer was severely weakened the panel.
Each original court I installed was actually 3 1/4 inches ID. For some reason I didn't realize this at first, the tubing was Parts Express close out. I couldn't get the tuning spot on, because I wasn't taking into account the actual inner diameter of the tubes I had.
Actually, once I realize this, A 3 inch tube fits perfectly inside, and enabled me to easily play with the tuning.
The final specs are: Heavy damping, interior lined with one and a half inch foam. Directly behind the woofers is two pieces of 2 inch Pyramid foam by Auralex, slanted away from the ports.
I used bass box 6 pro's suggestion for the flattest response, of 35.68 Hz tuning. So each port came out to 6.177 inches. Each flare accounts for 2 1/2 inches.
Well, I have to correct this slightly, Bass Box actually recommended a slightly lower tuning by one hz ( ports would have been 6.95") or so, but I didn't like the sound as much. So this was my own fine-tuning. Which is pretty much the way the final design of more speakers is.. computers can't hear the sound like humans.
Once tuned properly, the sound is both astonishing and astounding. It runs deep, tight, clean, awesomely detailed.
It now blends damn near perfectly with the other drivers. And that was my struggle. Either too mushy/boomy, and/or super loud ( compared to the other drivers), or it was tight and clean but not at the proper level.
Finally nirvana.
I can play complex bass songs such as Cat Stevens Wide World, or Spoon Man for example, and it's tuneful clean, and at the proper level. And goes deep when need be, thanks to the port output, and doesn't struggle one bit, or lose its composure.
Now I can totally listen to the music and not listen to the speakers, exactly what I was looking for.
As a sidenote I removed the foam blocks on each side of the Heil.
It doesn't need them now, because they were a Band-Aid due to the miss match of the Daytons.
The inner 3 inch tube is secure, but I can easily remove the outer flares, because of the outside original tubing been 3 1/4 inches ID. So they are more or less press fit.
May look a little strange, but I'm not worried it sounds fantastic !!
Running the stock mid bass driver by the way.
I think I'm going to do that on my second pair as well.
 

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