quick disconnect vs. soldering

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by 56_Special, Feb 25, 2006.

  1. 56_Special

    56_Special Member

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    I'm planning to install two speakers in a new cabinet. Is there any reason to prefer soldering the speaker wire directly to the lugs as opposed to using quick diconnect female spade connectors? The quick disconnects look to be more convenient, and frankly, the idea of soldering near speaker cones worries me a bit...what if some solder drips onto the cone?
     
  2. John Phillips

    John Phillips Member

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    Put a rag under the terminals while you're soldering :).

    Push-connectors can and do come loose, or when they get old, corrode and make poor contact (actually this sometimes happens where the wire is crimped into the connector, as well as between the connecter and the speaker - there are two possible failure points in each connection).

    If this happens when the amp is cranked, you might well blow the output transformer. Soldering is just better.
     
  3. Matt H

    Matt H Guest

    except that amateurs are less likely to make good soldering joints in the first place... the wire/lug mechanical connection is what needs to be made well, the solder is just there to keep it in place- not provide the electrical connection... and it's a pain in the rump for quick speaker swapping (taste testing)...

    as for corrosion- yes, after about 20 years this might be an issue... then you replace the push on connectors and it takes three minutes.

    there are two sides to every coin. for every advantage of one, there's an advantage of the other.

    as i've also pointed out before- think about the speaker plug/jacks you're using- guess what? the push on connects provide better contact than those do... *ahem*

    not to mention almost every production amp comes with push on terminals...

    yadda yadda yadda...

    i don't really think one method is better than the other, they both have strengths and weaknesses. I'm really just playing devil's advocate here.. the best answer is: "whatever you do- do it correctly and check it every so often".
     
  4. SeanF

    SeanF Member

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    I never solder 'em on if I can help it. Crimp the spade terminals to make sure they make good contact, they'll be fine.
     
  5. amper

    amper Member

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    Ever take a look at th wiring harness for your car? In most cars, you'd be hard pressed to find soldered connections, even under the hood (exposed to the elements and contaminants) with high current connections. As long as your crimp is done well, everything should be fine.

    The only good excuse for using a soldered speaker connection is that with a tube amp, you never want to run it into an infinite impedance (open circuit), so if your quick connect falls apart, you're in trouble.
     
  6. slider313

    slider313 Silver Supporting Member

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    Cars don't have an output transformer pushing 420 volts to a dead short(no load) if the speaker connection fails. I always remove the clip ons and solder to the speaker.
     
  7. amper

    amper Member

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    Guitar amplifiers don't push 420V out of the OT secondaries. In any case, it's the current that's the rub, not the voltage.

    In a typical OT, say one that steps down a 5000 Ohm primary to 8 Ohms, you've got a 625:1 turns ratio, so that 420V on the plates is coming out at less than a volt, but where your plate current might be 150 mA (give or take), it'll come out as 90+ amps (for a 63 W output, or so).

    Unless my math is wrong...and of course, this doesn't account for OT inefficiencies.
     
  8. The thing about soldering to speaker lugs is to make sure to use a good
    high-wattage iron (a soldering gun is best), good rosin core solder, and
    flux, which automatically cleans the corrosion off the lug during the
    soldering process. There shouldn't be any problems with a solder joint like
    that. There are solder joints from the '50s in old radios and TVs made like
    that that are still going strong.

    If you try to use a soldering pencil usually used for printed circuit boards
    on a speaker lug, you will almost certainly make a cold solder joint which
    will break, come loose, or become intermittent. A soldering pencil doesn't
    put out enough heat to properly solder a thick hunk of metal like a speaker
    lug.
     
  9. 56_Special

    56_Special Member

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    Thanks to everyone for all the input! If I were to use quick connects, what size? In other words, what is the size of a standard speaker lug?
     
  10. Shea

    Shea Member

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    I have a hunch the reason for that is because if vibrations cause a connection to shake loose, it would be preferable to have a quick connect terminal slip off than to have a soldered-on wire break at the joint. Fixing it will be easier (just put the connector back on), and if the connector is insulated then you have some protection against shorts as the wire flops around.

    But I do think quick connect terminals can work fine for speakers. Overall, I agree with Matt H. I've done it both ways.

    Shea
     
  11. amper

    amper Member

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    I should have mentioned that the only speakers I have with quick connects are connected to a solid-state amp. If one comes apart, nothing bad will happen to the power stage. All my tube amps have soldered connections.

    Oh, and I agree on the big soldering iron note. Those little pencils will only lead you to melt the insulation of your wire trying to heat up the joint. Please don't ask me how I know...
     
  12. SeanF

    SeanF Member

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    the ones for 16 - 18 AWG work fine.
     
  13. donnyjaguar

    donnyjaguar Member

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    Lugs are cheap cheap cheap! You can buy a lot of crimp-on lugs for the cost of one forfeited speaker. And having been the boss on an electronics production line (never again) I can assure you its quicker to terminate with lugs than solder every time.

    That said, I use crimps on vintage amps and solder on my own creations.

    Someone said soldering gun. Put that gun in the garbage and get a proper iron - or irons. Guns have no method of regulating the temperature of the tip. The tips don't last and there's not enough thermal inertia to solder anything of any size. They also get dirty which causes the temperature to be too low thus ensuring a piss-poor connection. Get yerself A 45Watt big tip and a 25W little tipped iron and you should be in great shape.

    DJ
     
  14. TubeAmpNut

    TubeAmpNut Member

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    Your math is a little wrong. 90A would smoke your speaker wires. ;)

    Calculating current load on speaker wire is as simple as I=sqrt(P/R). So if you had 100Watts-RMS into 4Ohms, then I = sqrt(100/4) = 5A. The same power over 16Ohms is 2.5A.

    If your curious, I'll tell you how to get RMS PWR.

    BK
     
  15. amper

    amper Member

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    Ah, I must be off on my transformer theory, then...

    Ah yes, a transformer transforms impedance by the *square* of the turns ratio...so instead of a 625:1 turns ratio, that should be a 25:1 turns ratio, so 420 V in is 16.8 V out, 150 mA in is 3.75 A out and 16.8 * 3.75 = 63 W (actually VA, but who's counting?)
     

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