ESS AMT 3 Crossover Schematic
- Thread starter automojo
- Start date
JBL GUY
Addicted Member
Again thank you very much for the information...I have not read all of it yet.
But on one of the pages I took quick look at...It mentions "Buzzing" and I usually play my AMT1s with the covers off...Anyway I started hearing what I thought was a problem...Had to look very close...But a very small dust bunny had landed on the diaphragm of one of the AMTs. Interesting stuff.:thmbsp:
But on one of the pages I took quick look at...It mentions "Buzzing" and I usually play my AMT1s with the covers off...Anyway I started hearing what I thought was a problem...Had to look very close...But a very small dust bunny had landed on the diaphragm of one of the AMTs. Interesting stuff.:thmbsp:
lacrosplayer
New Member
Amt three mid range crossover question
I don't understand my crossover one speaker has three parallel caps 6mfd 75vnp
and on speaker has two 1 7.5 mfd 75 vnp and one 3.5 mfd nvp caps
All the caps are el cap mexi brand? I am going to upgrade and follow autojama digi post of his amt 3
But why parallel vnp caps
I don't understand my crossover one speaker has three parallel caps 6mfd 75vnp
and on speaker has two 1 7.5 mfd 75 vnp and one 3.5 mfd nvp caps
All the caps are el cap mexi brand? I am going to upgrade and follow autojama digi post of his amt 3
But why parallel vnp caps
lacrosplayer
New Member
I have since learned
Why ESS used three caps in parallel
Now I am wondering why my cross overs are different than any diagrams I have seen here to date. I will post pics here soon
Ok this pic is from the ESS AMT-3 Rock Monitor that works (I have the other and the mid range is out) So I proceeded to test and found out that the mid range caps are bad, this is where I became quite confused.
This speaker (pic) crossover works. However if you can notice from the pic that it only has three capacitors One 20 one 55 and one (3 in parallel ) 6 UF 75 volt
The dead speaker came to me with the SAME configuration, only the mid capacitor (that is bad ) there is two in Parallel one 7.5 and one 3.5 = 11 UF 75 volt.
All the caps a EL CAP Aluminum electrolytic
So My question is Is this original Or even close?
Should I just go and replace all caps? and why is there no 1 ohm resistor in there
Why ESS used three caps in parallel
Now I am wondering why my cross overs are different than any diagrams I have seen here to date. I will post pics here soon
Ok this pic is from the ESS AMT-3 Rock Monitor that works (I have the other and the mid range is out) So I proceeded to test and found out that the mid range caps are bad, this is where I became quite confused.
This speaker (pic) crossover works. However if you can notice from the pic that it only has three capacitors One 20 one 55 and one (3 in parallel ) 6 UF 75 volt
The dead speaker came to me with the SAME configuration, only the mid capacitor (that is bad ) there is two in Parallel one 7.5 and one 3.5 = 11 UF 75 volt.
All the caps a EL CAP Aluminum electrolytic
So My question is Is this original Or even close?
Should I just go and replace all caps? and why is there no 1 ohm resistor in there
Attachments
![IMG_0414[1].jpg](/forums/data/attachments/417/417707-fd3840072606404a94ac6a07f3a31f4d.jpg)
Last edited:
lacrosplayer
New Member
I apologize
I do not have any info Like you I am reading and trying to get more info on what I have
Hopefully some one will read these post and start the ess revival again
I do not have any info Like you I am reading and trying to get more info on what I have
Hopefully some one will read these post and start the ess revival again
PaladinMRB
Audiophile
These schematics and documents are excellent; thanks for sharing! :thmbsp:
I have my father's 40+ year old AMT3's which have been pretty much in constant use over the years.
The foam surrounds on all four of the circa 1980's replacement woofers rotted out once again about a week ago. I've got a set of 689-1012 ESS drivers on order for replacement...hopefully they'll work well in this application. But it's good to see the wiring chart and the original spec drivers for these.
I have my father's 40+ year old AMT3's which have been pretty much in constant use over the years.
The foam surrounds on all four of the circa 1980's replacement woofers rotted out once again about a week ago. I've got a set of 689-1012 ESS drivers on order for replacement...hopefully they'll work well in this application. But it's good to see the wiring chart and the original spec drivers for these.
This appears to be a crossover between the 4 coil crossover (4 ohm woofers)and the 3 coil crossover (8ohm woofers).
Hard to say here-I'm a bit suspicious as it has no P.C. board-but perhaps maybe it precedes even the 4 coil crossover.
Are the woofers O.E.?
Ohm value?
Is the mid O.E as well?
Peerless 4 ohm Alnico?
Separate fuse by the Heil?
Personally I would repair what you have first.
Hopefully your O.E. woofers are 4ohm.
On a quest
New Member
Hi,
I am a first time poster but I have been a very appreciative miner of information on AudioKarma for a very long time. Like Lacrosplayer in an earlier post I have the same crossover in my AMT 3 Rock Monitors and I'm in need of some advice on how to proceed in getting these classics back to their original glory. I have a long story behind these beauties but I will try to cut it as short as I can. Originally bought with the impression that everything was original and come to find out to my disappointment they weren't. All four woofers were cheap replacements so my search for the the originals started. I found a pair of incomplete monitors minus the Heils that did have the original woofers up outside of Bangor Maine. I was going to visit my dad (92, still chopping wood and shoveling snow) up in South Portland, so another two hour trip up to Bangor was no problem. Got up there and found that he had other pieces that became a package deal (Dahlquist DQ-10's in pieces but complete, Klipsch KG 3's complete, and some Cerwin Vega DX7's (drivers/crossovers no cabinets) all for $250. On the trip back to New Jersey trying to fit everything into our SUV plus luggage I left the Rock Monitor cabinets in Maine thinking I just needed the woofers. They needed refoaming which is no problem but the problem is that the partnumber doesn't seem to match the info previously posted (680-0010). What I pulled out of the Monitors from Maine were (679-1111). Another question i have is if all the variations of the two "active woofer" Rock Monitors were hooked up in parallel? The reason why I ask is that All 4 woofers show 3.3 ohms when measured and obviously in parallel they are measuring under 2 ohms. The woofers are definitly original to the cabinets but with the cabinets being up in Maine it's tough to compare the differences between the ones I have in Jersey. Sorry for the long story but I'm hoping Lacrosplayer is still around and hopefully you still have your monitors to bounce some info off each other.
I am a first time poster but I have been a very appreciative miner of information on AudioKarma for a very long time. Like Lacrosplayer in an earlier post I have the same crossover in my AMT 3 Rock Monitors and I'm in need of some advice on how to proceed in getting these classics back to their original glory. I have a long story behind these beauties but I will try to cut it as short as I can. Originally bought with the impression that everything was original and come to find out to my disappointment they weren't. All four woofers were cheap replacements so my search for the the originals started. I found a pair of incomplete monitors minus the Heils that did have the original woofers up outside of Bangor Maine. I was going to visit my dad (92, still chopping wood and shoveling snow) up in South Portland, so another two hour trip up to Bangor was no problem. Got up there and found that he had other pieces that became a package deal (Dahlquist DQ-10's in pieces but complete, Klipsch KG 3's complete, and some Cerwin Vega DX7's (drivers/crossovers no cabinets) all for $250. On the trip back to New Jersey trying to fit everything into our SUV plus luggage I left the Rock Monitor cabinets in Maine thinking I just needed the woofers. They needed refoaming which is no problem but the problem is that the partnumber doesn't seem to match the info previously posted (680-0010). What I pulled out of the Monitors from Maine were (679-1111). Another question i have is if all the variations of the two "active woofer" Rock Monitors were hooked up in parallel? The reason why I ask is that All 4 woofers show 3.3 ohms when measured and obviously in parallel they are measuring under 2 ohms. The woofers are definitly original to the cabinets but with the cabinets being up in Maine it's tough to compare the differences between the ones I have in Jersey. Sorry for the long story but I'm hoping Lacrosplayer is still around and hopefully you still have your monitors to bounce some info off each other.
Sure no problem
So what does your crossover look like?
Most 4 ohm woofer versions were the first run of these, and had 4 coils, plus lots of resistors in the woofer zobel. That would be helpful to know. Later version all had 8 ohm units. All had active woofers, no passives. The 2 ways Monitors had passives. All 3 way rock monitors had 2 active 10" woofers.
So the thing to do would be to give me a good picture of your crossover from your current cabinet. If it's a 8ohm, these won't work. So then you might want to see if the guy in Maine still has the crossovers. Should be easy to ship.
Thanks
So what does your crossover look like?
Most 4 ohm woofer versions were the first run of these, and had 4 coils, plus lots of resistors in the woofer zobel. That would be helpful to know. Later version all had 8 ohm units. All had active woofers, no passives. The 2 ways Monitors had passives. All 3 way rock monitors had 2 active 10" woofers.
So the thing to do would be to give me a good picture of your crossover from your current cabinet. If it's a 8ohm, these won't work. So then you might want to see if the guy in Maine still has the crossovers. Should be easy to ship.
Thanks
Porkloin
Oscar Heil Groupie
MONDO-NERDO UPDATE: See the addendum on the attached drawing. My Rock Monitors had brightness switches that rotated in opposite direction from one another. This made a difference in the layout of the resistors. I'm not sure if this would be applicable to the 4 coil units, but something to bear in mind for anyone with a rotary brightness switch.
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On a quest
New Member
automojo,
My crossovers are the same that is pictured in lacrosplayer's posting from a few years ago. Both the cabinets from Maine and the cabinets that I have in New Jersey are both the ported versions. I thought that there wouldn't be any problem parting out one to the other but I guess I was wrong. The cabinets that are up in Maine are securely tucked away in my brother's basement so getting the crossovers out of them will be no problem. I am just a little confused about the different versions that this classic speaker went through during production. Not only were the ported and non ported versions different from each other but it seems like within the ported version there differences. The lighting could be better but there is what I have. Thanks for any help or advice you or anyone else can provide, I really appreciate it. On a totally different subject, I am having a set of Ohm model F's totally rebuilt by Bill LeGall up at Millersound ( an unbelievable great audio mind) can't wait. In his opinion when properly rebuilt his "favorite speaker of all time". Thanks again for your help
My crossovers are the same that is pictured in lacrosplayer's posting from a few years ago. Both the cabinets from Maine and the cabinets that I have in New Jersey are both the ported versions. I thought that there wouldn't be any problem parting out one to the other but I guess I was wrong. The cabinets that are up in Maine are securely tucked away in my brother's basement so getting the crossovers out of them will be no problem. I am just a little confused about the different versions that this classic speaker went through during production. Not only were the ported and non ported versions different from each other but it seems like within the ported version there differences. The lighting could be better but there is what I have. Thanks for any help or advice you or anyone else can provide, I really appreciate it. On a totally different subject, I am having a set of Ohm model F's totally rebuilt by Bill LeGall up at Millersound ( an unbelievable great audio mind) can't wait. In his opinion when properly rebuilt his "favorite speaker of all time". Thanks again for your help
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On a quest
New Member
On a quest
New Member
Just got a phone call from ESS and they are sending me the schematics to this variation of the Rock Monitor, And as soon as I receive the info I will post it. He did say that the 679-1111 part number is a legit ESS part number and he will verify that they should be hooked up in series instead of parallel as the 8 ohm 680-0010 were in the other variation. He did say the later versions had the round magnets. Love people that stand behind their product, and help out when they can.
Those are original drivers? I am surprised to see drawn steel, the AMT Monitors have cast baskets.
Porkloin
Oscar Heil Groupie
I think the cast baskets are a relatively modern phenomena. These came out of my monitors and I've seen several more just like them pictured here at AK.
On a quest
New Member
There was a version of the Rock Monitors that used the 679-1111 woofers which measure 3.3-3.5 ohms. ESS verified that they are a legit part number for woofers that were used in a version with the two active woofers. I am waiting on some documentation including the schematics to put some more of the pieces of this puzzle together.
