$100 ESS AMT3 rock monitors

Discussion in 'Speakers' started by Jer, Sep 9, 2017.

  1. Jer

    Jer New Member

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    IMG_4041.JPG IMG_4036.JPG IMG_4038.JPG IMG_4039.JPG

    I picked these up locally off Craigslist for $100
    The guy said his wife wanted them gone. They were in their master bedroom.

    So, a couple questions.
    Does anyone have a parts list of the capacitors I should buy?

    Second question,
    Will these woofers work well in these cabinets?

    Eminence 10” Foam 1040SF - 175w/350w https://www.amazon.com/dp/B01A9CF58U/ref=cm_sw_r_cp_api_useTzbW004RDJ

    Thanks -
     
  2. djnagle

    djnagle Lunatic Member

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    These are well worth finding original woofers and doing a total rebuild.
     
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  3. BilboBaggins

    BilboBaggins AK Subscriber Subscriber

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    I have to agree!
    You scored!

    Those are world class speakers if you spend a little bit to get the right drivers and restore them. I had the 1aM towers and yours are considered better than mine. They are big beasts that disappear when you play them with a sufficient high current amp. They can take up to about 275 watts max. The imaging is incredible. I drove mine with a Bose 1801 and they were a really good match. I abc' d mine with Kef 104/2s and Kef 105s and the differences were more which one was slighter better at this type of music than anything else. I ended up keeping the 105s in the end. Couldn't afford to keep both.
     
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  4. BilboBaggins

    BilboBaggins AK Subscriber Subscriber

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    There are a lot of good threads on the web on the rock monitors! You really lucked out. By the way, ESS is still around and has replacement drivers for them, I think. I recently bought a diaphragm for one of my Heils on a pair of AMT 1 pedestals from them, and I believe they had woofers for the RMs.
     
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  5. BilboBaggins

    BilboBaggins AK Subscriber Subscriber

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    IMG_1676.JPG [Here were mine during the AB C session. Oops, I think I have that session on another machine. IMG_0674.JPG IMG_2073.JPG
     
    Last edited: Sep 9, 2017
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  6. Porkloin

    Porkloin Oscar Heil Groupie Subscriber

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    The Eminence 1040 SF is the long time heir apparent to the original drivers in the older ESS speakers with 10" drivers. If you plug their TS parameters into one of the online calculators, the cabinet volume of the Rock Monitor is correct for a pair of them. If you can lay hands on a set, it's probably a good thing to do.
    Below is the schematic of the crossover for my generation of the Rock Monitors. However, yours looks a little different. I believe that there was a rendition with 4 ohm woofers at one point, so you may want to post the values of your existing capacitors to see if we can determine what the impedence of woofer your crossover was meant for.
    AK ESS guru @automojo has also pointed out that the 1040 SFs would benefit from a Zobel network, which is easy enough to calculate and implement when and if that time comes.

    AMT3_Schematic.jpg
     
    Last edited: Sep 10, 2017
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  7. Jer

    Jer New Member

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    Thanks for the info !

    I'll check those caps.
     
    Last edited: Sep 10, 2017
  8. Jer

    Jer New Member

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    51.5 uf
    75v
    Are the values from the cap in the bottom of this photo.

    I need to remove the wad of silicone from the other one.

    Woofers are factory wired in parallel.
     

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  9. GD70

    GD70 AK Subscriber Subscriber

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    Awesome score! Porkloin did a gorgeous restoration on his. After seeing his, I've been intrigued to at least hear a pair of these, and recently did a bit of online looking.
    I don't need any more speakers, but I would not pass up a pair of these of the right deal fell into my lap!
    Looking forward to your listening impressions.
    Glenn
     
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  10. Jer

    Jer New Member

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    The cap in top of this pic reads 7r5 uf / 75v
     

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  11. Porkloin

    Porkloin Oscar Heil Groupie Subscriber

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    The value of the inductor coil is actually the more relevant figure in guestimating the crossover point and impedence of the woofer(s), but if the woofer cap is the same (51.5 uF) as the one in the schematic, I'd be willing to bet that the coil is the same (2.4 mH). This is further bolstered by your woofers being wired in parallel, like the ones in the schematic. This at least confirms that you can use a pair of 8 ohm woofers, like the 1040SF. A pair of 4 ohm woofers wired in parallel would have drastically different values
    "7R5" uF? I wonder if that's 7.5 uF? Probably labeled in their country of manufacture. You'll have to see if you can see the labeling on the other capacitors paralleled to it. When you parallel capacitors, you sum their values. For example, a 7.5 uF capacitor paralleled to a 20 uF capacitor would present a 27.5 uF capacitor to the circuit. If you pararlleled a 5.5 uF capacitor to those two, it would become 33 uF. When ordering a replacment, you could order a single 33 uF cap rather than parallel 3 of them together, or you could order any combination of caps that total 33.
    I know that it's not much help, but you're going to have to read the values on all of your existing capacitors to determine replacements as a schematic of your particular generation of AMT3 crossover doesn't seem to be available.
    Frankly, I'd be a bit skittish about working without a factory schematic, and in your shoes, I'd probably convert the entire setup to match the present drawing. Unfortunately, inductor coils cost money, although Dayton (Parts Express) has offered them at very reasonable prices.

    The crossover laid out in the schematic above.

    IMG_0079.JPG
     
    Last edited: Sep 10, 2017
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  12. Porkloin

    Porkloin Oscar Heil Groupie Subscriber

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    A bit of info for the Eminence:

    Link to the online enclosure calculator.

    The Eminence 1040SF figures plugged in
    EminenceEnclosureCalculator.JPG

    The calculated volume for a SEALED enclosure (you can put that ball gag the little lady got you a couple of Christmas' ago into the port)
    EminenceEnclosureCalculatorResults.JPG
    That's 1.37 cubic feet per driver. With two drivers, that's 2.74 cubic feet, which is pretty close to the volume of an ESS monitor cabinet. NOTE the low end frequency of 55.6, which is relatively anemic in a chest-puffing audiophile pissing contest, but if you can listen to them without the manufacturer whitepaper preconceptions, I think you'd be pleased.
     
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  13. Jer

    Jer New Member

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    Awesome. Thanks for the replies.
     
  14. automojo

    automojo OurBandCouldBeYourLife Subscriber

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    Curious if your mid range has a rubber surround hard to say ?
    I would just replace the capacitor's in the resistors with the value shown on them
    Obviously they ran out of crossover boards or this is the transition between the four coil and the three coil.
    I would measure the resistance of the midrange driver.
    The 4 coil had 4 ohm woofers... most three coil model as I know I've had eight ihm woofers .
    Regardless you want to put the right rating back in otherwise it throws your crossover off
    I'm thinking if your mid is 4 ohm, your woofers were probably the same... but I can't be absolutely certain
     
  15. automojo

    automojo OurBandCouldBeYourLife Subscriber

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    Awesome but by th way!
    I've had good luck using the Eminence BP 102's as well.
    However I run mine with 2x 3" vents, interior foam lined and 5" of foam behind the woofers.
    The problem with the 1040SF, running them with the stock port and all the stuffing, essentially a leaky sealed system, is they have a nasty peek in the 40 or 50 Hz range. You could re-engineer the crossover or add a Zobel.
    I can run a simulation with the BP 102's in a sealed 2.7 cf enclosure.. to see if it leans towards a peak... but a lot of times you just don't know till you install them and listen to them after they've broken in.
    I'm thinking the BP's will be smoother and tighter in response.
    A tip off is if they play fairly loud at low/mid volumes, then you have a peak that needs to be dealt with.
     
    Last edited: Sep 11, 2017
  16. Porkloin

    Porkloin Oscar Heil Groupie Subscriber

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    My concern arises from the remote possibility that someone else along the way was not as prudent and deviated from factory original values. Without a known schematic, you'll never know unless you chart what you already have and do a bit of reverse engineering.
    Can the software you have take a schematic and simulate it's potential output? If Jer was willing to work with us, I could send him out a small LC meter to take a reading on those coils and we could recreate the documentation that ESS seemed to lose back in the great Sacramento beer flood of '81.
    Whoops, almost forgot the gratuitous shot of the girls playing in the living room.

    ListeningSpace.JPG
     
  17. automojo

    automojo OurBandCouldBeYourLife Subscriber

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    I doubt it..those look like stock caps..
    He can figure out the value of each and the resistors..but I bet they are the same, or close the the typical 3 coil pc set up
    The advantage is they aren't going through small pc traces..a major draw back IMHO... as I've seen the traces lift before from heat..
    The circuitboard may look neat, but it's there to reduce production costs, specifically labor not improve sound.
    Plus if you look at the colors of the wires they make sense .. comparing to the circuitboard version .
    Looks stock to me..
     
    Last edited: Sep 11, 2017
  18. Jer

    Jer New Member

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    The mid cones have rubber surrounds.
    I'll check ohm...
     
  19. Jer

    Jer New Member

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    Here's a few more pics IMG_4076.JPG IMG_4077.JPG IMG_4075.JPG
     
  20. Porkloin

    Porkloin Oscar Heil Groupie Subscriber

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    (4) inductor coils and (3) capacitors with a pair of 8 ohm woofers and an 8 ohm midrange. This sort of goes against everything said here so far. It's the other way around on the drawing above and Automojo pointed out that the (4) coil crossover came with the 4 ohm woofers, but apparently ESS threw yet another deviation into the mix.
    Do you have the ability to follow the component contacts and sketch out a schematic?
    You may want to think about replacing those resistors also as they're considered a wear item. They go for about a buck a piece. That, with electrolytic capacitors, and you still won't qualify for free shipping at Parts Express.
     

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