Blown Speaker???

[yarrick19]

Hey guys,

I was micing up my dual rectifier today and decided to bring out my Mesa rectifier 2x12 cab that I haven't used for a while and give it a whirl. Volume knob on the dual was at about 9 o'clock - loud but nothing too crazy. When I fired it up I noticed that the sound was intermittently changing. It would go from normal sounding to a little quieter and 'differend' sounding. It did this for a little while so I went into the isolation booth and noticed that only one of the speakers was working. The other speaker was really quiet and was putting out some lows but no mids/highs from the dust cap area. I've never blown a speaker before... Does this sound like I have a blown speaker?

I took the back off my cab and all the connections looked solid. If its blown, I'm a little surprised since that cab is rated at 120 watts. :zombie:

 

[arv_foh]

Well there are several types of damage when you refer to a blown speaker...

if the speaker is truly "blown" (meaning the voice coil is shot) there will be no sound from the speaker at all.

if the cone or surround is damaged (ripped, torn etc) there will still be sound from the speaker but you might notice the speaker is farting out, or that the quality of sound coming from it is not what you expect

if you are not getting a full range of sound that could possibly be some sort of short or loose connection inside the speaker cabinet.

 

[Rhys Llewellyn]

To test if the speaker is actually blown, gently press around the edges of the speaker and if you hear a grinding sound, then yes, the voice coil has burned out or is damaged beyond repair and this grinding sound is bits of the copper wire come away from it's winding and will have to be replaced.

And yeah, what arv said if that's not the case.

* Oh and also power ratings down translate like that. It's all down to how much you actually move the speaker. So if you have an EQ pedal in there boosting too much bottom end, for example, then this could easily cause a speaker blow out at maybe even half volume.

 

[yarrick19]

All the connections in the cab seem solid. How would I go about testing for a short?

 

[Rhys Llewellyn]

All the connections in the cab seem solid. How would I go about testing for a short?

How is the cab wired?

Are you feeding two outputs from the head to the cab or just one?

All signs point towards a blown speaker. Have you tried pushing the speaker in to the voice coil gently? You can instantly rule this out then.

Or alternatively, grab a 9v battery, and connect it very briefly to the damaged speaker whilst it is disconnected from the circuit. It should be clear which is negative and positive. Connect the circuit briefly (literally just touch the terminals for a brief half second), if the speaker makes a pop and moves, then it is working.

If not, then it be fucked

 

[arv_foh]

All the connections in the cab seem solid. How would I go about testing for a short?

you need a voltmeter to do that

EDIT:

http://www.ehow.com/how_6860113_test-short-speaker-wires.html

 

[bryan_kilco]

I've heard of the 9V battery test before.

Other than that, good luck man! How would it be blown if it was working fine before, then just sat? I'm thinking of getting a Mesa 2x12 for smaller club shows to save my back and space...but they are like over half of a 4x12 in price!!

 

[yarrick19]

Thanks for the replies guys. It's officially blown. I picked up a digital multimeter and testing the resistance shows an infinate reading meaning the voice coil is melted or opened. Also did the 9v battery test and it didn't make a sound or move (I did this on the speaker that is still working and it made a pop noise). Time to pick up a new V30!