Why did my speakers blow?

[Downunderwonder]

I agree with Munjibunga. What fries speakers is distortion from the power amp OR sending the speaker frequencies it can't reproduce. It's physics. The energy has to go somewhere. If energy (low frequencies from the amplifier) reach the speaker from the power amp can't be reproduced by the speaker, they turn to heat, and unfortunately that process happens in the voice coil of your speaker.

The other most common scenario is distortion from the power amp of your rig. If you push an amp past what it can reproduce, you get distortion. It doesn't matter how much power. You're more likely to blow a speaker with an underpowered rig, because you're more likely to get in situations where you push the hell out of it to keep up with your band.

precious little in there is agreeable to Munji or me or anyone who understands the underpowering myth for what it is. See the amps sticky.

 

[Vince Klortho]

...

The other most common scenario is distortion from the power amp of your rig. If you push an amp past what it can reproduce, you get distortion. It doesn't matter how much power. You're more likely to blow a speaker with an underpowered rig, because you're more likely to get in situations where you push the hell out of it to keep up with your band.

Not a trace of truth here. If it were true every guitarist and bassist who used a fuzz box or an amp with built-in distortion would fry speakers constantly but in reality it is not common. Distortion itself does NOT blow speakers.

 

[ThisBass]

I agree with Munjibunga. What fries speakers is distortion from the power amp OR sending the speaker frequencies it can't reproduce. It's physics. The energy has to go somewhere. If energy (low frequencies from the amplifier) reach the speaker from the power amp can't be reproduced by the speaker, they turn to heat, and unfortunately that process happens in the voice coil of your speaker.

The other most common scenario is distortion from the power amp of your rig. If you push an amp past what it can reproduce, you get distortion. It doesn't matter how much power. You're more likely to blow a speaker with an underpowered rig, because you're more likely to get in situations where you push the hell out of it to keep up with your band.

That's exactly why some players like me do like tube amps.
sorry, couldn't resist, but indeed my favorite amp is the 70's svt head, and this beast overlods the power amp pretty nicely, just to get sufficiant noise on stage with "smallish" 212.

 

[agedhorse]

What fries speakers is distortion from the power amp OR sending the speaker frequencies it can't reproduce. It's physics. The energy has to go somewhere. If energy (low frequencies from the amplifier) reach the speaker from the power amp can't be reproduced by the speaker, they turn to heat, and unfortunately that process happens in the voice coil of your speaker.

The other most common scenario is distortion from the power amp of your rig. If you push an amp past what it can reproduce, you get distortion. It doesn't matter how much power. You're more likely to blow a speaker with an underpowered rig, because you're more likely to get in situations where you push the hell out of it to keep up with your band.

Naaah, looks like you have taken little bits of truth and turned it into a couple of inaccurate conclusions.

1. Distortion by itself does not fry bass guitar speakers, though it can damage tweeters. A heavily distorted signal contains more power than an undistorted signal which might result in the speaker being OVERpowered. Distortion can damage tweeters because distortion is nothing more than the addition of higher ordered harmonics which shift the power density profile (versus frequency) of the signal, thus OVERpowering the tweeter.

2. (Low) Frequencies that can not be reproduced by the speaker most often result in excessive mechanical displacement, and thus OVERpowering the speaker because a speaker's mechanical power handling decreases quickly below the F10 of the speaker. Heat is an entirely different aspect of failure, and in all speakers, most of the signal gets transformed to heat even in the best of conditions. A speaker that is 5% efficient (pretty high) converts 95% of the signal to heat.

3. You are FAR more likely to damage a speaker from OVERpowering, exceeding either its thermal or mechanical limits. For bass guitar applications, it's usually the mechanical limits that are encountered first. This matches what I see coming in from the field.

 

[Old Garage-Bander]

In the approximately 49 years that I've played bass, I have not damaged a driver. And I frequently use amps that supply MANY more watts than my speakers can handle. I avoid damaging the cabs by not overdriving them -- it's as simple as that!

One of my current rigs of choice includes a Peavey IPR2-5000 into three 350 watt cabinets. Even though this amp is capable of producing thousands more watts that my cabs can handle, I can pretty much guarantee you that I won't damage my drivers with this amp (unless the amp malfunctions, of course).

Just be careful!!! Keep the volume and EQ reasonable, and your gear should last a long, long time!

By the way, I'm not posting to drive you crazy -- that's just a side benefit!

Sorry, the crazy part is my own inner demons. You don't control that. But I'm glad to know you do control your volume. Thanks for helping with my sanity.

 

[Old Garage-Bander]

Being a veteran speaker wrecker, I can't comment on the technical side of "how" BUT, I can offer:

Parts Express

You'll want the exact model number and specs from the cabinet & speakers originally installed to replace correctly.

I DO use the direct box and have the PA help move the bass around (you may too). In many situations, unless you want to bring extra cabinets, you'll need PA support because the guitars & keys & vocals (oh yeah, the drums) all travel a lot easier through the atmosphere than bass does...and your bass tone needs a certain amount of fidelity to give it ooomph, tone and presence.

I have a spare set of 2 x 10's ready to go having replaced drivers a few times now inspite of my best efforts to 'control' the situation.

P.S. IF you're bass is active, be v e r y mindful of you overall volume.

mmmmmmmm... I like Parts Express.

 

[Old Garage-Bander]

Not a trace of truth here. If it were true every guitarist and bassist who used a fuzz box or an amp with built-in distortion would fry speakers constantly but in reality it is not common. Distortion itself does NOT blow speakers.

But isn't distortion as an effect, like from a fuzz box, different than distorting an amplifier by overdriving it?

 

[middy]

Back on topic. The OP said he kept the eq flat, but the VPF was "normal". What do you mean by normal? All the way counter clockwise is off. Halfway up is quite a bit of high and low boost...

 

[R Baer]

As others have mentioned, the cabs "wattage" is actually their thermal rating; mechanical failure due to over excursion is still possible under "safe" power.

My DB750 puts out 750 watts at four ohms, but due to the lack of built in HPF I can easily blow apart any commercial cab rated for 1200+ watts (810, 412, etc.) with the gain and master both well below noon and without even boosting the bass....

Agreed. Definitely worries me as a cab manufacturer to see a new breed of amps hitting the market putting out 1000, 1200, or more watts. And of course, when these guys blow a driver, it will be the old "Honest, I was just playing a coffee house gig at a fairly quite volume when it blew". There's gonna have to be some new rules if all the amp manufacturers start going down that path. Personally, it doesn't make sense for me as a manufacturer to put out a head that will blow the crap out of your cabs, but that's just me. Yeah, it's great to have all that "headroom", but saying that you want to have all that power on tap but won't use it, is a bit like saying you drive a Corvette, but never slam the pedal down every now and then just for fun of it.

 

[MDBass]

Agreed. Definitely worries me as a cab manufacturer to see a new breed of amps hitting the market putting out 1000, 1200, or more watts. And of course, when these guys blow a driver, it will be the old "Honest, I was just playing a coffee house gig at a fairly quite volume when it blew". There's gonna have to be some new rules if all the amp manufacturers start going down that path. Personally, it doesn't make sense for me as a manufacturer to put out a head that will blow the crap out of your cabs, but that's just me. Yeah, it's great to have all that headroom, but saying that you want to have all that power on tap but won't use it, is a bit like saying you drive a Corvette, but never slam the pedal down every now and then just for fun.

Most newer amps have built in HPF's to help avoid this...hardly anyone really wants to be sending much information below 50Hz to either their amp or FOH anyway.

A more unified watt rating system wouldn't hurt though, even within brands...I had two TH500's daisy chained via the FX loop for awhile, pushing 500 watts a piece into 4 ohms cabs, and even though the DB750 is rated for 100 less total output watts in the same setup it had exponentially more headroom.

 

[Munjibunga]

Thanks for checking in. You bring wisdom to the conversation. It seems that many of those who profess to use overly high power amps with significantly underrated cabs, either fail to know they have to keep them turned down, or fail to pass that information along to others. Sure it can be done, but with great caution. If someone "accidentally" cranks your 500 watt amp up to 11 without your knowledge, your 200 watt cab will suffer. Then someone reads that high power amps with low power cabs is OK. But if they do not understand the caveats, then trouble is afoot. I'm glad you finally brought some sense to that whole conversation.

Well, I'm usually only about a hundred or two watts over the cab rating, and I don't play in loud bands.

 

[marmadaddy]

Lots of good information in this thread, thanks everybody. I'm thinking the most likely cause was pushing too much low end. I'm going to invest in a good HPF.

As to the "you should have heard them complaining" comments: I use in-ears so I wouldn't have heard it. The amp was there as a stage monitor for the other guys in the band.

 

[Vince Klortho]

But isn't distortion as an effect, like from a fuzz box, different than distorting an amplifier by overdriving it?

No, they are essentially the same things.

 

[adivin]

"Why did my speakers blow"?

They needed the money. Ooooh.

 

[R Baer]

Most newer amps have built in HPF's to help avoid this...hardly anyone really wants to be sending much information below 50Hz to either their amp or FOH anyway.

The key word here is most. Some will, some won't. Also, just because an amp has a HPF, that doesn't mean it's implemented in way that will be effective. All depends on the engineering. My guess is that most manufacturers don't want to loose too much in the deep lows and are setting their HPF around 30Hz or so with a very steep slope . Will that offer enough protection from a 1200watt amp when you've had a few beers and cranked the bass and volume up? Maybe. Maybe not.

 

[Jim Carr]

Lots of good information in this thread, thanks everybody. I'm thinking the most likely cause was pushing too much low end. I'm going to invest in a good HPF.

As to the "you should have heard them complaining" comments: I use in-ears so I wouldn't have heard it. The amp was there as a stage monitor for the other guys in the band.

Weren't the other guys in the band using in-ears, too?
This scenario would make any amp vulnerable to "pushing too much low end," no?

 

[B-string]

Agreed. Definitely worries me as a cab manufacturer to see a new breed of amps hitting the market putting out 1000, 1200, or more watts. And of course, when these guys blow a driver, it will be the old "Honest, I was just playing a coffee house gig at a fairly quite volume when it blew". There's gonna have to be some new rules if all the amp manufacturers start going down that path. Personally, it doesn't make sense for me as a manufacturer to put out a head that will blow the crap out of your cabs, but that's just me. Yeah, it's great to have all that headroom, but saying that you want to have all that power on tap but won't use it, is a bit like saying you drive a Corvette, but never slam the pedal down every now and then just for fun.

I most always appreciate your posts. The bold is my latest pet peeve though. Headroom is only headroom if it is usable. If you can blow your drivers with 1,000 watts (average signal) and you have a 3,000 watt amp you still have only 1,000 "watts" of headroom. I have god knows how many lightyears of headroom right now, if I step outside. Inside the ceiling is about 8 feet so in reality I have only 8 feet of "HEADROOM". What you can not use is not headroom it is wasted potential.

 

[R Baer]

I most always appreciate your posts. The bold is my latest pet peeve though. Headroom is only headroom if it is usable. If you can blow your drivers with 1,000 watts (average signal) and you have a 3,000 watt amp you still have only 1,000 "watts" of headroom. I have god knows how many lightyears of headroom right now, if I step outside. Inside the ceiling is about 8 feet so in reality I have only 8 feet of "HEADROOM". What you can not use is not headroom it is wasted potential.

Totally agree. I was being a bit sarcastic and should have put the words "headroom" in quotes, because it's the word everyone on TB uses to describe the reason why they want so much power for their rigs. Don't want to derail this thread with this topic though. My only point originally was to say that it's easy for even a moderately powered head to damage a speaker cab and even more so with todays higher and higher powered heads. It's not as simple as just saying my head puts out 400w and cab is rated at 400w, so I should be fine.

There are other factors at play. Most cab power ratings are based on the driver manufacturer's power rating, which is the thermal rating of the coil. Basically, how much juice you can feed the voice coil before it burns up. This rating has nothing to do with how much power it takes to push your drivers past their maximum excursion point and damage the driver.

Lot's of other factors to consider as well. Things like the high pass filters on the amp make a difference. Some amps have ones that are effective and some don't. There's also plenty of amps out there that don't use one at all. Is the amp's "flat" setting actually flat? Many amps already have a low end bump built into the preamp, so turning up the volume is doing more than just making it louder, your'e also adding low end. Are you cranking the lows? Slapping? Playing a 5 string tuned down to A? Using an octave pedal, envelope filter or other effects? All these thing will turn that just right wattage rating on your amp into speaker killers, due to exceeding the excursion limits of your drivers.

And let's not forget technique. At NAMM, I've repeated watched players who can fart out a cab with the volume on say 2 or 3, while other players with excellent right hand technique can raise the volume to 6 or 7 without having the cab break a sweat. Technique alone can make a huge difference.

 

[Bob Lee (QSC)]

This could occur with only 1.5x the power required to achieve Xmax depending on the suspension compliance.

It will also depend on the frequency of the signal. X volts into a driver at 500 Hz, for example, will cause far, far less displacement than the same voltage at 50 Hz.

 

[Bob Lee (QSC)]

I agree with Munjibunga. What fries speakers is distortion from the power amp OR sending the speaker frequencies it can't reproduce. It's physics. The energy has to go somewhere. If energy (low frequencies from the amplifier) reach the speaker from the power amp can't be reproduced by the speaker, they turn to heat, and unfortunately that process happens in the voice coil of your speaker.

The other most common scenario is distortion from the power amp of your rig. If you push an amp past what it can reproduce, you get distortion. It doesn't matter how much power. You're more likely to blow a speaker with an underpowered rig, because you're more likely to get in situations where you push the hell out of it to keep up with your band.

No, the loudspeaker simply receives and responds to a signal. It cannot discern what is clean signal and what is distortion. Clipping creates distortion that adds harmonic content, but it can also obliterate much of the higher frequency content in a complex original signal. There is no universally correct answer to whether it increases or decreases the higher frequency content; it depends on the individual situation.

You cannot blow a loudspeaker by underpowering, but by clipping an amp you will make it put out more than its power rating would suggest is possible.

The core cause in blowing loudspeakers—whether through overpowering or overexcursion—is simply trying to do too much with too little.