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I have an old school (like 1970) Jarguar (yes with the "r") cabinet with Marshall Loudspeaker speakers.

I cannot find any information about these speakers or the cabinet at all on the internet. I think it was only made in the '70's but it has be a beaut until recently. I was a fool and assumed this was an 8 ohm cabinet and thus plugged it into my 8 ohm output of my Line 6 DT50 amp. Which worked great until a couple of weeks ago. Now my amp is in the shop and the cabinet does not work. I get very little volume out of it and even after taking the speakers out and hooking them up directly they are not right at all. They sound puny and crackly, all four of them. Is it possible I blew all four speakers simultaneously? They don't rub and the resistance reads 6.2 on all of them. I would really like to get this cabinet working again. Before I took it apart I was getting only 0.1 ohms reading at the jack and 3.2 ohms at the speakers. So I assumed there was a short somewhere but there is no evidence of that. Any help would be appreciated

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    Don't assume that measuring a speaker nominally rated at 8 ohms with an ohmeter should give you 8 ohms - the story with impedance is a bit more complicated than that. I also think that hooking up a low impedance speaker to an amplifier not designed to handle it would be a special case of "shortcircuiting the amp" (or "almost shorticircuiting it" with a resistor), which would in theory have detrimental effect on the amp, not on the passive element, YMMV, though.
    – Some Dude On The Interwebs
    Mar 21, 2015 at 9:31
  • Taking the drivers out to hook them up individually to a known working amp is not a good idea and also doesn't help much with troubleshooting. What happens if you hook the whole cabinet up to a known working amp? Nothing? Bad sounds? Some drivers working and some not? If you have a 4 ohm output on another amp that would be an ideal test just in case. Ah you said "very little volume". What is the test amp like?
    – Todd Wilcox
    Mar 21, 2015 at 12:45

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One test is to attach a small battery - 1.5v is fine - to each speaker. The cone should jump either in or out on contact. This is mainly for checking the polarity of each speaker, so that they can be connected in series or parallel properly. Connect each individually, not while in circuit. It will tell whether a speaker is still responding, although if you're only getting a whisper from each, it does sound like bad news. Pushing the cone back and forth silently shows the voice coil is not damaged.

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