Re: Help! Speaker cab on the fritz!
B2D said:
How could I have blown it?!?!
The cab will handle 135 watts and I run a 100W Legacy with an attenuator through it... and nothing other than my amps have ever been used through it! I haven't even gigged it with the current speaker setup.
Ehhh...let's go back to school shall we?
When you crank up an amp and make a noise the speaker responds by moving in and out, one complete movement is called a cycle and there are thousands of 'em per second. A real world example that everyone can relate to would be A440. In this case, the speaker (or tuning fork, guitar, piano etc) will vibrate 440 times in one second and that produces the note that we hear, put that through an amp & speaker and the speaker will move in and out 440 times in one second. The louder the amp is the farther the throw on the speaker is and if the amp is clipping and sending square waves out, the speaker will actually go out and stay out and come in and stay in and this of course happens
thousands upon thousands of times in matter of seconds. Granted, the nature of the beast is that square waves usually happen only with solid state amps and
not tube amps but the effect is the same.
That's why when dealing with solid state amps in the audio world you always want to overrate the speakers to the amp, not the other way around. Running a 500 watt amp with a 300 watt speaker is good because you'll hear the speakers start to give up before the amp clips. But running a 300 watt amp into 500 watt speakers is bad because the amp will clip and send a square wave to the drivers, you’ll never hear the speakers giving up until they actually do. Tube amps are another matter because generally, they don't create square waves and we call the ‘distortion’ warm or phat or whatever you want to call it.
Anyway...
As the speaker is making its round trips in & out the glue & magnet in the voice coil get hot. Get it hot enough for long enough and they can start to melt which will obviously change the sound. If & when they melt enough...POOF!!!
No more speaker.
There are a lot of other things that can cook a voice coil; anything from damage to the speaker surrounds, volume, and ultra or sub sonic frequencies which are things you can't hear but are still being produced or reproduced by the chain...Whammy pedals & effects are great for creating some of that stuff. Hell, one time I cooked an amp by using a buffer box that's designed to boost a guitars signal so you can use a 100' feet or longer cable and not have any sonic degradation. Well, a byproduct of the design was a 75kHz tone which is so high up there dogs probably can't even hear it...but it cooked a Bogner and 4x12 cab with Weber's so there 'ya go!
Now, to see if you cooked a speaker you need to have access to the front of it which usually means taking it out of the cabinet. Lay the speaker down and put your fingers in a circle around the dust cap (the center of the speaker) about halfway between the cap & the surround, or outer part of the driver. Push gently but firmly and listen to the sound of the speaker. If it makes a rubbing and/or clicking sound the speaker is dead. If it makes no sound at all then the speaker is probably A-ok and the problem lies elsewhere.
Hope that helps a bit,
