How do you blow a Speaker?

[Shango66]

It doesn’t happen much, only twice in 30 yrs but this past weekend I blew a 100w speaker with an amp running on about 50w max.
Last time 20 yrs back..I blew 2x Celestion Blues in a Vox ac 30.

my question is, why would these speakers burn out when they are made to take more punishment than I’ve been delivering at the time.?
here’s a pic of Jensen 100w Neo 10” with what appears to be burnt out (amber) wires in the cone.

 

[kbold]

Were you distorting/clipping the signal?
DC or a signal with a DC component, such as a clipped signal (speaker sees a portion of the signal as DC) will burn out a speaker quicker than a clean signal.

 

[bebopbrain]

A 50W amp is rated for producing a clean 50W sine wave. Fully distorted, the output is a 100W square wave. In both cases the signal at the speaker has the same amplitude (same peak voltage), but the square wave has SQRT(2) more RMS voltage and RMS current. Power is V*I so you get twice the power. It is impossible to get more than twice rated power unless the rating itself is wrong (conservative).

It is possible that the speaker failed at lower power. Is so, disregard.

 

[Shango66]

Clipping...distorted?
No more than a TS9 with dials at 12 noon.

 

[Peegoo]

You certainly can cook a voice coil at a power level lower than a speaker's rated capacity.

Oftentimes the culprit is playing with too much feedback, which causes limited travel of the speaker's cone forward and backward.

A speaker's voice coil keeps cool via cone excursion, which pumps air in and out of the gap occupied by the voice coil former. If the speaker is producing high frequency oscillation, the cone barely moves and the voice coil heats up, melting the adhesive and causing the coil to drop from the former.

Another cause of a blown speaker below the rated capacity is DC leaking into the signal via the output transformer. DC forces the cone to one excursion extreme--forward or back--and locks it there in position; that turns the voice coil into a heating element. And the rest (and the speaker) is history.

 

[nickmm]

Square waves from clipping... something came apart.

 

[Weazel]

How do you blow a Speaker?​

No teeth.

I am so very sorry. Really.

 

[Dacious]

At a studio my friend worked at, they had bass boxes with 20 year old 1000 watt speaker combined which were regularly blown - after people started doing slap bass. The old cabs didn't have a crossover and horn. Bass speakers don't like short sharp transients and it overheated the voice coil when funk became a 'thing'. High frequency is more than the voice coil trying to move the 'motor' and cone.

A 50w RMS speaker will normally support a 50w RMS amp. But you can blow a 200w speaker by driving enough square wave through it. Hit it with enough boost or distortion it's very easy. Square wave looks like a dead short to the speaker - it tries to move both ways at once. You can also get inaudible hi frequency feedback happening.

The Blues are 15 watt speakers but a fullbore healthy AC30 pumps out 36 watts. Very common to blow them in normal usage - along with tubes, flaming transformers, burning resistors...... Afterall, it is pommy electrical 'engineering'.

 

[printer2]

One way I blew a speaker was to plug it into a 120V socket. It only lasted a few seconds but boy it sure was loud.

 

[GlideOn-Designs]

People forget - A speaker has a finite level usage to it before it no longer performs as desired or reliably.

Especially combo amplifier guitar speakers from the 60s or 70s after decades of continued use/abuse and exposure to humidity and the elements.

 

[VintageSG]

As others have put already, square waves can be absolute buggers. The acceleration time is minimal and a heck of a current builds in the coil. There's the 'hold' at the plateau, then the rapid switch to full 'opposite' current. There's the mechanical lag at each point, and the current build can easily exceed the coil's handling, even at or below it's rated power.
Any DC component adds to the issue.

 

[Wally]

It doesn’t happen much, only twice in 30 yrs but this past weekend I blew a 100w speaker with an amp running on about 50w max.
Last time 20 yrs back..I blew 2x Celestion Blues in a Vox ac 30.

my question is, why would these speakers burn out when they are made to take more punishment than I’ve been delivering at the time.?
here’s a pic of Jensen 100w Neo 10” with what appears to be burnt out (amber) wires in the cone.

View attachment 1002309

I 8nstalled a pair of the Jensen Neo’s 8n a BFTR for a pro when the speakers were introduced. He wanted to reduce the weight. The next time I saw the amp about 6 months later, he had a pair of Celestion Neos inthe amp. I asked him what Happened, and he said the Jensen Neo’s blew. I wanted to hear the amp, so I plugged it in. After a few seconds, I asked him how long the Celestion had been in. He answered the question, and then I asked ‘when did the one of the left start rubbing?’ He had not heard it...and he was not happy. Surely other people have had better luck, but based on his experiences I am gunshy.
maybe they hold up better in lower powered amps???

 

[brookdalebill]

About 35 years ago, my Peavey Mace had no difficulty at all popping a pair of nice EV SRO’s.
It had nothing to do with me.
I might have been a little, uh, LOUD.

 

[Wally]

About 35 years ago, my Peavey Mace had no difficulty at all popping a pair of nice EV SRO’s.
It had nothing to do with me.
I might have been a little, uh, LOUD.

Well, if those were coffee can SROs, they were out-matched by that Mace, weren’t they. Iirc, those were just over 30 watts RMS with a peak handling of 60 watts.
Now, if they were the later ‘SRO’ speakers with the big, flat magnet, those were 300 watts….but still they could fail.

 

[63 vibroverb]

I wore out a Jensen Neo 12-100 fairly quickly in a Music Man combo amp. Only lasted me about a year and a half.

 

[ahiddentableau]

You plug a 50watt marshall into a single 20W speaker. Ask me how I know!

 

[Fenderbaum]

 

[Wildeman]

Well, if those were coffee can SROs, they were out-matched by that Mace, weren’t they. Iirc, those were just over 30 watts RMS with a peak handling of 60 watts.
Now, if they were the later ‘SRO’ speakers with the big, flat magnet, those were 300 watts….but still they could fail.

I have those coffee can one's in my 100w Twin, they sound fantastic but I'm careful not to turn the amp past 5/6. They are old and outmatched by the amp for sure.

 

[2L man]

If there is sign of overheating on those wires the voice coil must have got much hotter because they are wound tight and heat concentration load comes higher?

Jensen recommend amp power only half what the loudspeaker power rating is and only 1/4 what musical power rating is which is confusing approaching stupidity