12 Ga. Romex in speaker cab. Don't do it!

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by stump, Aug 7, 2006.

  1. stump

    stump Member

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    I picked up a 1970 Super Reverb about 8 months ago. The previous owner said that he "Blackfaced" it and, as a bonus, used 12 gauge solid core Romex Electrical wire for the speaker wiring. Being cautious about "mods" that others have done I inspected the board work, which was good and the speaker connections. The joints looked pretty solid. About 2 months ago the sound quality declined considerably. I put new power tubes in and rebiased. I was still getting strange harmonic overtones. Changed out the preamp tubes- same problem. Got busy and didn't take up the problem until last week. While playing through it the sound suddenly cutout. I immediately powered off and checked the fuses, tubes, etc. and then decided to pull the chassis. While removing tubes I noticed that one of the speaker wires had broken off of the joint. I rewired with 16 ga. stranded and the amp never sounded better. Fortunately I didn't toast anything and had improved tone. I believe that the reason stranded wire is used is so that it flexes under vibration. I've wired much Electrical machinery and have used stranded wire for this purpose. The original owner said that he read in a "well known" amp modification book that this would give a great improvement to the tone due to more signal hitting the speakers with less resistance. I hope that this is not true as I could have lost a great amp due to a bad idea. Maybe this will help someone else to save their amp from blowing up.
     
  2. donnyjaguar

    donnyjaguar Member

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    You are 100% correct. I would only use solid wire for audio if it were perhaps for a home installation in the walls.

    Like you say, any application subject to any vibration is not a good place for solid wires. General Motors used solid aluminum wiring in some of their vehicles in the early 1980s. I wasn't aware of this until a nice police lady gave me a ticket because all my rear lights were out. I fixed it myself easily enough but pleas to the local magistrate resulted in only a reduction in fine and a reminder to do my "circle check" before I drive away in my car. :(

    DJ
     
  3. Junior

    Junior Member

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    I experimented with this about 20 years ago, when the wire craze hit the audiophile world, and thick solid wire sucks tone. Very fine strands suck tone, too. You did the right thing, 16 ga. stranded is ideal.

    You are right about machinery, it's wired to JIC spec, and stranded wire is used because of the vibration. It's good practice to have the insulation butt up against the connector, as this will reduce flexing, but some QC guys want to be able to see if you nicked any strands. Foo on them. Crimped connectors are used because solder will crack from flexing before the wire will.
     
  4. stump

    stump Member

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    Junior,
    I considered soldering on spade connectors but the speaker tabs were not in the best of condition due to the 40 plus watts required to de solder the 12 ga. I'm sure that my joints will probably hold forever.
     
  5. dogfood

    dogfood Member

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    I'm on a job and have access to some 4/0 AWG, it IS stranded, do you think it will be large enough for my 8" speaker on my Gorilla amp? :D
     
  6. stump

    stump Member

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    That should increase the power and clarity at least 10 fold. Just be sure to use spade connectors or better yet car jumper cables for the solderless solution. :)
     
  7. Junior

    Junior Member

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    :rotflmao:rotflmao

    Just so others get the joke, the "strands" in that stuff are what? About 14ga. solid? It's around 1" thick, and if you have to make a tight bend, you use a piece of 6" pipe as a mandrel and a rubber mallet.
     
  8. fullerplast

    fullerplast Senior Member

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    There's nothing wrong with using solid core wire for a speaker if done properly. Your 12 ga wire did not break at the speaker terminal from speaker vibrations. People have been using solid core for years and it is not uncommon in the audiophlle world for speaker connections.

    Disclaimer: I don't use solid core or have any preference one way or another. It's just another choice, and perfectly safe done correctly. Don't use it where it would be repeatedly flexed. I wouldn't suggest it in an open back combo for example (unless done carefully), but in a cabinet where the ends are fixed there should be no problem at all. Strap it to the cabinet at a couple of places between the speaker and the jack and you are good to go.
     
  9. bettiefan

    bettiefan Member

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    Gorilla should have known better than to make compromises in their design by NOT using the 4/0 cable. For the least possible signal loss, use the thickest possible cable. :AOK
     
  10. Junior

    Junior Member

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    I've just done some "research" on the web, and can find no one supporting my dislike of Romex. I have none handy to repeat my tests, so I will yield on this point, but once I did hear a distinct loss of highs. (Otherwise, I'd likely still be using it because it looked so funky!) In retrospect, it may well be I didn't dress the ends properly (5-way posts can't really crush the solid wire to make good contact, as they can with stranded wire).

    I did find this rather amusing page from a McIntosh engineer:
    http://www.roger-russell.com/wire/wire.htm
     
  11. fullerplast

    fullerplast Senior Member

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    Good, interesting writeup and summary of various testing. Key excerpts:

    and:

     
  12. hasserl

    hasserl Member

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    That is good stuff. I like this quote:
     
  13. Junior

    Junior Member

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    My favorite anecdote goes something like this:

    An esteemed audiophile editor invited some friends over to hear his new cables. After they had settled in, he put on a familiar piece qand they all listened intently, commenting and congratulating him for assembling such an excellent system. Then, he knelt behind each speaker affixing the new cables and played the piece again. This time, they listened quietly, and when the piece ended they sat in stunned silence. "Simply amazing!" one of them finally blurted. "Such detail!" "So transparent!" "Like a veil was lifted!" They all chimed in, until finally some asked, "What are these new cables of yours?". The editor grinnned sheepishly. "Guys, I only pretended to change cables..." he admitted.

    True story.

    I don't understand... well, I was still a teenager when I realised how easily the ear is fooled. Admittedly, I've been at this longer than most of those guys, but seems to me they've had plenty of time, numerous opportunites, to realise the same thing. Yet they persist in promoting fancy wire, green pens, lacquer, wooden knobs... seems to me the term "golden ears" refers to the ability to hear a cash register ring.

    I do not belong to the "we can only hear what we can measure" camp, but jeez, a little common sense goes a long way. Then again, as someone's .sig says, "Common sense isn't that common.". :)
     
  14. doctorx

    doctorx Member

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    Christ, don't let this get around, next thing you know Eric Johnson will be rewiring his Marshal cabs with it.
     
  15. TwinandTwang

    TwinandTwang Member

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    If you are wiring for home audio installation in the walls you should use stranded wire.
     

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