broken connection in speaker cab

frankensamurai · 10-26-2009, 09:44 PM

I just acquired a '74 slant cab. The wiring did not look original to me -- it is only red, but the seller assured me it was. I didn't really believe him, but it was a good price so it didn't matter too much. He warned me after I bought it that "the wiring was short" so to be careful when I opened the back panel. Well, I was careful, but I wanted to check the cone codes. As I was doing so, though I was only using a very small amount of pressure, one of the connections to the speakers snapped loose. All of the cables are soldered together, and the piece that snapped off was part of that. Now I get no sound out of either of the speakers on the right.
Frankly I wonder if it had broken before and this guy had just managed to jury rig it somehow.

I have no knowledge of wiring cabinets or doing any soldering, or any electrical systems at all. My question is -- will I need to re-solder that? (Or have someone do it?) Is there an easy fix? Should I just have the whole thing rewired anyway? Because it seems like whoever wired it did a poor job of it, at least on this part.

American Viking · 10-27-2009, 01:11 AM

Yeah, you definitely need to rewire that. Word to the wise, when taking the back off of any cabinet, always unscrew the jack and take it off.

Another important piece of information you need is to never operate your amplifier with a cabinet that has incomplete or damaged wiring. You will cause severe damage to your amplifier!

When a wire comes loose like that, the impedance of the cabinet has changed, when an amplifier and a cabinet have a mismatched impedance the output transformer is going to fry as impedance matching is the relationship between electricity and distribution. If the transformer is sending current with no place to go, it arcs and shorts windings within the transformer and can also take other components with it when it dies.

Search for Impedance Matching in this forum.

Here are links for your wiring project, you do not need a tech to do this. It is really simple.

Wiring a 4 X 12 Speaker cabinet
Jumbo Sunshade - Speaker Wiring Diagrams

Here is one link that discusses the importance of impedance matching among other things.
Amp problems? Ohm questions? Amp blowing up for no reason, READ ME!

Before and after wiring, it is always best to check the impedance with a multimeter or ohmeter. One can be purchased for as little as $10. Check all the speakers individually first off, as a bad speaker will result in a reading of infinite (open circuit) or 0. Once completely wired together, check the final load for proper resistance, or impedance. To get the final load I just plug a cable into the cabinet, positive lead to the tip of the plug and neutral to the jacket or sleeve. Any reading on a meter will typically be 2ohms less than actual impedance. ie. My 16ohm Marshall cabinets read 14.4.

American Viking · 10-27-2009, 01:13 AM

This stuff is insanely easy once you get a slight grasp on it. Got any questions just ask. I was intimidated by this stuff once.

10-27-2009, 01:11 AM	#2 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 1,510	Re: broken connection in speaker cab Yeah, you definitely need to rewire that. Word to the wise, when taking the back off of any cabinet, always unscrew the jack and take it off. Another important piece of information you need is to never operate your amplifier with a cabinet that has incomplete or damaged wiring. You will cause severe damage to your amplifier! When a wire comes loose like that, the impedance of the cabinet has changed, when an amplifier and a cabinet have a mismatched impedance the output transformer is going to fry as impedance matching is the relationship between electricity and distribution. If the transformer is sending current with no place to go, it arcs and shorts windings within the transformer and can also take other components with it when it dies. Search for Impedance Matching in this forum. Here are links for your wiring project, you do not need a tech to do this. It is really simple. Wiring a 4 X 12 Speaker cabinet Jumbo Sunshade - Speaker Wiring Diagrams Here is one link that discusses the importance of impedance matching among other things. Amp problems? Ohm questions? Amp blowing up for no reason, READ ME! Before and after wiring, it is always best to check the impedance with a multimeter or ohmeter. One can be purchased for as little as $10. Check all the speakers individually first off, as a bad speaker will result in a reading of infinite (open circuit) or 0. Once completely wired together, check the final load for proper resistance, or impedance. To get the final load I just plug a cable into the cabinet, positive lead to the tip of the plug and neutral to the jacket or sleeve. Any reading on a meter will typically be 2ohms less than actual impedance. ie. My 16ohm Marshall cabinets read 14.4. __________________ -I'd rather be a good liver than have one...

10-27-2009, 01:13 AM	#3 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 1,510	Re: broken connection in speaker cab This stuff is insanely easy once you get a slight grasp on it. Got any questions just ask. I was intimidated by this stuff once. __________________ -I'd rather be a good liver than have one...

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