argh!!...I've had it with Eminence....

Discussion in 'Amps and Cabs' started by bolero, Dec 4, 2005.


  1. bolero

    bolero Member

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    for fock's sake...*another* one of my private jacks fell apart on me today...:rolleyes:

    I bought a brand new quad of these for my '68 basketweave cab this summer (...running a '66 jtm100 into it, which barely puts out 100w, cranked )



    right out of the box one of them was buzzing...but I assumed it was the old cabinet, so spent some time experimenting before I realized it was the new speaker!!


    no problem..send it back, they looked at it, determined that it was defective & replaced it


    meanwhile I had 3 of these otherwise new speakers sitting around...waiting a couple weeks for the replacement to show up I decided to try one out in a ~35w combo I have....sounded great..I will say these are excellent sounding speakers...but then that speaker died suddenly....."disassembled itself catostrophically" is what Eminence said, when I sent it back. defective. luckily it didn't damage my amp..:mad:


    so I get those 2 replaced, and pop them back into my 4x12....GREAT, I can use it again!!


    just 10 minutes ago one of those replacements did the exact same thing....fell apart while I was playing :mad: :mad: :mad: these are rated at 50w, there are 4 of them, and my amp doesn't put out more than 100w

    WTF Eminence?????


    I've had it with these things....I'm also worried if they keep replacing them, eventually one will damage my amp when it goes...


    any advice on convincing them to refund me so I can buy another brand of speaker?

    thx
     
  2. HeeHaw

    HeeHaw Member

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  3. doctord02

    doctord02 Member

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    I dont question your Eminance issues at all, but if your '66 JTM 100 is bearly putting out 100 watts when cranked, something is seriously wrong.

    My '66 JTM 100 does 214 watts with everything dimed, and does 112 watts at the onset of clipping.
     
  4. bolero

    bolero Member

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    no, the early 100w amps were only just 100w..the later ones ( like yours I guess) got louder

    something to do with the output transformers they used not being ideal for KT66's

    I'm sure someone here ( Ned?) knows the specifics


    cheers
     
  5. riffmeister

    riffmeister Gold Supporting Member

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    sweeeeeeet! :rolleyes:
     
  6. Antero

    Antero Member

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    "disassembled itself catastrophically" is an amazing phrase.
     
  7. big mike

    big mike Fixed Bias Moderator Staff Member

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    Grrrrrrr. That would put me off em permanent.

    My solution was Scumbacks. I liked the Private Jacks, these are better. By a ton!
     
  8. hogy

    hogy Member

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    I have a very early JTM45/100 (it still has Vox style brass vents) that has the KT66 OT. With nearly 600V on the plates it does put out well over 100W before it breaks up, and dimed it will destroy a 4X12 with greenbacks.

    Hogy
     
  9. Laroosco!

    Laroosco! Member

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    Mike,
    Are your Scumbacks the G12H or G12M's?

    How does the Z28 sound through them?
     
  10. big mike

    big mike Fixed Bias Moderator Staff Member

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    I have H/M mix in both my 2x12's, and the 65watt H in my Z 1x12.

    The Z28 shines through them!

    As does the marshall and Rockytop. But The Z in particular is just stellar through the higher wattage version.
     
  11. bolero

    bolero Member

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    well, there must be some variation with them then, because we scoped this & it's just over 100w cranked

    -->it's actually useable without being too loud when it's crunchy


    this coincides with cerrems' observations over on plexi palace forum..I did a quick search & found this

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

    The normal plate load for a 100W OPT,67 on up with EL34 is 1.7K....
    Important NOTE: early Marshall 100W heads used 4K plate loads..which is too big BUT makes the tubes clip sooner and put out less watts..more crunchy overdrive..

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

    The whole plate load issue with Marshalls is a "wacky" topic...especially the JTM-45 stuff.....
    There was a "gross" mistake made when they originally fit the plate load.....Two KT66 valves at 400V plate/screen a 4K is a perfect fit.....and with 450V plate and screen you get 3.4K as a perfect fit...these are numbers I came up with when using the correct curve sheets...
    The "rookie" mistake they made,which is common, is that they used the wrong data sheet to derive the plate load....The GEC and RCA manuals show 6L6/KT66 plate curves at 250V screen.....if you plot a plate load at 450V on the 250V "screen" curves you get exactly 8K ...and if you look in the data sheets under KT66 "TRIODE" connected yo get 6.6K...
    Now when the plate load gets bigger...you get less clean headroom and therefore the output valves clip sooner...
    So if you hook up a scope to the output you will note the point when the sine wave just has onset of clipping...that is "clean" power output and it's this point that is reduced with increased plate load value...BUT...the power-output doesn't end there....when you continue to crank the amp past clipping you will put out a ton of harmonics that all sum up to make more power output "distorted" power output....So my JTM45-100 puts out 49Watts of clean power just up to clipping..then from there on its all crunch and at full volume puts out 105 watts of distorted power...
    So by increasing plate load you exchange one for the other..clean power for distorted power....
    One thing to note about plate resistance durring "full-throttle" amp operation.......when the amp is cranked with a big plate load, it slams into the triode region of the curves, instead of staying in the saturation region....well now since this is a 50% di]uty cycle square wave....this means that majority or 99% of the wave is spends it's time in the triode region of the curves and this means the KT66 plate resistance will be roughly about 200 ohms when the amp is cranked...
    Now for the punch line....It appears as though Marshall blew lots of OPT's in the early years and this was due to the fly-back , back EMF affect high voltages....well put a huge square wave on a transformer and see how it likes it when not properly damped...
    Now someone, probably not at Marshall, "corrected" the plate load to 3.4K for two tubes...and this would equivalently be 1.7K for 4 tubes.....Does sound familiar????? Now this would be perfect for KT66/6L6 tubes.... Now Marshall saving money jumps over to EL34 tubes and now the plate load is mis0matched again...But wait, 3.4K is not that bad of a mis-match for EL34 valves and in fact sounds darn good and it's pretty safe from fly-back currents....

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

    now, I'm not saying you guys are wrong about your amps, but I am saying there isn't anything wrong with mine...and it does put out around 100w cranked.

    regardless, private jacks are rated at 50w each, and 4 of them should easily handle my 100w amp


    cheers
     
  12. fakeox

    fakeox Member

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    "Now someone, probably not at Marshall, "corrected" the plate load to 3.4K for two tubes...and this would equivalently be 1.7K for 4 tubes....."

    I believe that was Mike Kojima from Kahlua Music in Scarborough Ontario.
     
  13. el34power

    el34power Member

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    hmmm interesting! that might explain why i smoked a private jack with my 2203 running on two tubes with the pre and master at 2:00. I didn't bother fighting much about it as i thought i was 100% responsible. The Private jack is rated at 50...100 peak!
     
  14. Roccaforte Amps

    Roccaforte Amps Member

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    I haven't had one failure, and none of the speakers
    that are out on tour have failed.
     
  15. Roccaforte Amps

    Roccaforte Amps Member

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    You can burn a 100watt speaker with a 10watt amp
    thats clipping hard, high frequencies will heat any speaker up.
    FWIW.
     
  16. Roccaforte Amps

    Roccaforte Amps Member

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    The "rookie" mistake they made,which is common, is that they used the wrong data sheet to derive the plate load....The GEC and RCA manuals show 6L6/KT66 plate curves at 250V screen.....if you plot a plate load at 450V on the 250V "screen" curves you get exactly 8K ...and if you look in the data sheets under KT66 "TRIODE" connected yo get 6.6K...
    Now when the plate load gets bigger...you get less clean headroom and therefore the output valves clip sooner...






    Wrong, when the plate load is lower, you work the tubes harder,
    they clip sooner.
     
  17. 62sg

    62sg Member

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    Same with me. Have not had any failures, either.
    John
    'StoneAge Custom Cabinets'
     
  18. 57special

    57special Silver Supporting Member

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    BFDR into Foxx Fuzz wa into Gauss speaker (400 watt )= me finding out how expensive it is to recone a Gauss.
     
  19. bolero

    bolero Member

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    well, what can I say? they've already replaced 2 defective speakers & this one just did the same thing


    back to my original question, does anyone have any advice on dealing with Eminence?


    I have 2 other cabs & have never blown any of those....


    you guys are reacting like it's my fault?

    I'm not even using effects: there's no way four new 50w speakers shouldn't handle that amp...and I triple checked the wiring in the cab
     
  20. Roccaforte Amps

    Roccaforte Amps Member

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    Nobody is saying its your fault. Why not contact Eminence directly, nobody but them can help you here.
     

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