Yikes, I think I Blew my Cab!

[maddog]

Nope no burnt smell and as far as I can see with a flashlight (I have the speaker out now) the wires from the male prongs on the back of the speaker basket go into the cone and are fine, I gently oulled on each one and they are attached to something in there but thats all I can see. this dogs beat enough so I'm just going to get a new speaker for now.


thanks for the education guys.. Taj

Did you try moving the cone by hand?

 

[Tajue17]

no I didn't but I'm not sure what you mean , I'm guessing your saying to try to move it when theres a signal going through it?

 

[Oldtoe]

No. He means take the grille off the cabinet (if present) and physically push the cone inward with light pressure by hand. It should move freely. If there's a scraping noise, it's toast.

 

[maddog]

no I didn't but I'm not sure what you mean , I'm guessing your saying to try to move it when theres a signal going through it?

Taj,

Facing the speaker, place your hand on the center of the cone where the dustcap is. Your hand should be spread open with pressure on your fingertips and palm. (Think of palming a basketball) Gently push against the speaker making sure to keep an even distribution on the cone. It should yield with a bit of pressure although there will be some resistance. Do this with no signal.

If it won't move, strummer is probably right in that the VC is stuck in the gap. Also, feel for any scraping while the cone is moving. You need to make sure to keep the pressure distributed so it will travel in the intended path, straight back and forth. If you feel any scraping, you've probably got a melted VC.

It still bothers me you got no sort of burnt smell. The blown speakers I've dealt with usually have an odd burnt/melting odor.

Just wanted to check once more (please bear with me):
1) The head works fine?
2) The patch cable works fine?
3) There is no fuse on the cab?

 

[Oldtoe]

The 12" driver that had a melted voice coil in my Bergantino cabinet had no smell, FWIW. Took me a while to figure out what was going on, as a result. Must be fairly well sealed.

 

[maddog]

The 12" driver that had a melted voice coil in my Bergantino cabinet had no smell, FWIW. Took me a while to figure out what was going on, as a result. Must be fairly well sealed.

Thanks Ben. Noted for future reference. Don't want to be sending Taj on a wild goose chase.

 

[BigBallz]

1. What Does "Clipping" Mean and Why is it Bad?
Clipping usually means that the maximum output of the amplifier is being exceeded and the tops of the signal peaks are being "clipped" off. During these times the cones of the loudspeakers are essentially receiving a DC signal. This means that most of the energy from the amp is heating up the voice coil instead of moving the cone. Usually loudspeakers fail or burn-up because of this heat. (aka. Thermal Failure) You should also be aware that any clipped signal in the chain can blow a loudspeaker even if the amplifier isn't at full output. Most loudspeakers fail because they are driven by too small an amplifier. The power ratings for a loudspeaker are only valid for unclipped input signals. So, to avoid problems, always operate your gear safely below "clip level".


2. How Much Power do I Need?
In general the bigger the amplifier the better. Once you reach an amplifier's maximum output, you cannot get anymore out of it. Push the amp input signal any harder and your output will be distorted. It is also true that most speakers will handle momentary peaks far in excess of their rated power handling, if these peaks are clean. (not clipped) SBAL speakers are so efficiently designed that you could easily use as little as 10 watts for certain applications. We would recommend however that you have at least a 400 watt per channel amplifier ( 8 Ohms). This will allow you to get more out of your system and provide you some safety margin in the event you need it. (headroom)

http://www.soundbridge.com/support.htm


This should clear up any "misconceptions" to what burns up a speaker. Hope this prevents anyone from damaging their speaker(s) in the future.

 

[AnthonyD]

Question re: active/passive inputs relative to this discussion...

When high output/volume is necessary, I'm beginning to think that using the "passive" input with the amp set at a moderate level makes more sense (and safer for the speakers) than using the "active" input and needing to crank the amp a bit more...

Am I on the right track or have I completely missed something!?

 

[shamus63]

Question re: active/passive inputs relative to this discussion...

When high output/volume is necessary, I'm beginning to think that using the "passive" input with the amp set at a moderate level makes more sense (and safer for the speakers) than using the "active" input and needing to crank the amp a bit more...

Am I on the right track or have I completely missed something!?

I'm interested in the answer to this one, as well.

 

[Tajue17]

now theres some good info... okay I'll look into Eminence speakers instead of carvins .. which reminds me, thanks Maddog for the link above. Taj

 

[Mobay45]

now theres some good info... okay I'll look into Eminence speakers instead of carvins .. which reminds me, thanks Maddog for the link above. Taj

Check www.avatarspeakers.com. They sometimes have some good specials on raw speakers. Click on the "Scratch, Dent & Overstock" and it will take you to the special deals.

 

[BigBallz]

OK...let me give you guys some info. I am speaking in GENERAL TERMS. Lets say a music man bass, whict is ACTIVE puts out 1/4 volt. I don't know it's exact output, the schematics don't list it. And a PASSIVE bass puts out 500 microvolts, again..JUST guestamating here.

What you have in modern amps are two different inputs One, "normal" and that would be for passive, 2nd input "Active" and that would be for your "active" aka "preamp" basses.

Most amps, the only difference, is a resistor between these two inputs to drop the voltage of the signal from the active bass, as not to overload the preamp of the amplifier.

Now, my SVT does not have a "input limit light"...so I have to be carefull when using the regular input with my M/M. Other modern amps have an input limit light as well as a "Master limit light".

On an amp with a limit light on the input, go right ahead and use your active signal bass in the normal channel...just keep your input limit light in a "flickering" mode. You just want to see it flicker...not constant.

Remember, when you use the -15db, or "active" input on your amp...you are sending a weaker signal to the preamp, that's why you have to turn it up more. Now, when you turn up your amplifier to amplify that weaker signal, you are turning up ALL the noise in your preamp, cable, bass and any rf around you.

So, if you can SAFELY use the "normal" input, always choose it over the "padded" or -15db input.

 

[strummer]

Long time ago, but still...

I have had speakers fail because too short or too long tinsel leads. Too short,and they were stretched so that the solderign into the voice coil got yanked and the coil wire proke mechanically.
Too ling, and the actual tinsel leads connected, shorting the signal path.

 

[tadawson]

The other possibility is a thermal failure than then became mechanical. Voice coil overheating can cause the coil to sag, and then drag on the pole piece. Play it this way long enough, and the friction will cause a total break in the coil, and no output whatsoever . . . . . and this is a pretty common failure mode. In a multi driver cabinet, it would be a lot harder to hear a failing driver compared to being alone, and the drag need not be that severe - it may sound fine right until it dies. (I had a PA bottom go out this way - sounded fine and then "click" - gone. Not much friction on test, but on recone, the old voice coil had an obvious hotspot the size of a pea or so, which was riding on the pole until it failed catastrophically . . . . fortunately, about 5 minuted from the end of the gig . . . .)

For those debating active vs. passive inputs, as BigBalls was stating, basically gain is gain . . . if you use the padded input and then turn up the input gain, the result is identical to just using the unpadded input from a gain standpoint, assuming that neither is clipping . . . which should be pretty easy to detect by either ear or a clip light on the head. The other thing that still kills me are folks who say things like "I couldn't be driving it that hard, I was only on 5". Well, guys, the knob position is pretty much UNRELATED to how hard you are driving, other than to raise and lower the level. Once again, it is all about gain structures. A hot input signal with a high front end gain can drive your power amp to clipping at pretty much any master volume setting . . . it's not like the throttle on your car, where maximum power out is limited by the knob . . . . And since the EBMM active preamps are quite hot signal wise, this is really easy to do if you don't pay attention. For this kind of stuff, clip indicators on the power amp section of bass gear (like on PA amps) would be really handy, but then, the amp builders would probably sell a lot less replacement speakers.

And a last note, on the clipping/DC thing. Once again, as others have said, clipped signals are essentially DC for the period of clipping. The impedance of a speaker (4, 8, or whatever ohms) is a function of both the coil electrical resistance and the interaction between the cone/coil in motion and the magnetic structure (back EMF). That's why if you measure an 8 ohm speaker with a meter you see something more like 5 or 6. AC signals see the full 8, DC sees the 5 or 6 . . . . and coupled with the higher power of a clipped signal in the first place, also causes the clipped signal to produce far more heat than an unclipped signal of exactly the same strenght. No magnetic interaction, no back EMF, no cone motion from DC equals pure coil heating. Speaker ratings also are a bit of a variable. I don't know if it was in this thread or not, but someone made a comment that "a speakers rating is not what it can take constantly". Well, it depends on who's speaker and what rating system. I have used a LOT of Electro Voice gear over the years, and while on paper, they used to look to be lower power rated than a lot of their competition, a closer look at the ratings revealed why. EV used the RS-426 spec from the EIA for power testing, which states that a driver must be able to sustain the load for a minimum of 8 HOURS. The test signal is broadband noise, and in the case of the classic EVM-15B, was broadband from 40 to 318 Hz, and sloped off at 6db/octave above and below. The test signal was sent to an amp with a constant power level set to the rating of the driver (200w in this case) and a peak of 9db above that, or 1600 (yes, you read that right - 1600) watts in this case. And once again, the driver must have been able to survive this for 8 hours minimum to get a 200w rating. And then there is the voodoo/bulls**t home audio market where a 200w driver means 200w for 6 nanoseconds submerged in liquid nitrogen, on the dark side of the moon . . . . . (yes, I think most consumer gear is mis or fraudulently rated . . . ). But it does explain why pro stuff will take a hell of a lot more abuse than "consumer" gear with much higher printed ratings. The trick with our bass gear is to figure out exactly how it was rated . . . . .

- Tim

 

[AnthonyD]

...And then there is the voodoo/bulls**t home audio market where a 200w driver means 200w for 6 nanoseconds submerged in liquid nitrogen, on the dark side of the moon...

Hysterical!

Thanks for the education guys - this is good stuff!

 

[BigBallz]

The other possibility is a thermal failure than then became mechanical. Voice coil overheating can cause the coil to sag, and then drag on the pole piece. Play it this way long enough, and the friction will cause a total break in the coil, and no output whatsoever . . . . . and this is a pretty common failure mode. In a multi driver cabinet, it would be a lot harder to hear a failing driver compared to being alone, and the drag need not be that severe - it may sound fine right until it dies. (I had a PA bottom go out this way - sounded fine and then "click" - gone. Not much friction on test, but on recone, the old voice coil had an obvious hotspot the size of a pea or so, which was riding on the pole until it failed catastrophically . . . . fortunately, about 5 minuted from the end of the gig . . . .)

For those debating active vs. passive inputs, as BigBalls was stating, basically gain is gain . . . if you use the padded input and then turn up the input gain, the result is identical to just using the unpadded input from a gain standpoint, assuming that neither is clipping . . . which should be pretty easy to detect by either ear or a clip light on the head. The other thing that still kills me are folks who say things like "I couldn't be driving it that hard, I was only on 5". Well, guys, the knob position is pretty much UNRELATED to how hard you are driving, other than to raise and lower the level. Once again, it is all about gain structures. A hot input signal with a high front end gain can drive your power amp to clipping at pretty much any master volume setting . . . it's not like the throttle on your car, where maximum power out is limited by the knob . . . . And since the EBMM active preamps are quite hot signal wise, this is really easy to do if you don't pay attention. For this kind of stuff, clip indicators on the power amp section of bass gear (like on PA amps) would be really handy, but then, the amp builders would probably sell a lot less replacement speakers.

And a last note, on the clipping/DC thing. Once again, as others have said, clipped signals are essentially DC for the period of clipping. The impedance of a speaker (4, 8, or whatever ohms) is a function of both the coil electrical resistance and the interaction between the cone/coil in motion and the magnetic structure (back EMF). That's why if you measure an 8 ohm speaker with a meter you see something more like 5 or 6. AC signals see the full 8, DC sees the 5 or 6 . . . . and coupled with the higher power of a clipped signal in the first place, also causes the clipped signal to produce far more heat than an unclipped signal of exactly the same strenght. No magnetic interaction, no back EMF, no cone motion from DC equals pure coil heating. Speaker ratings also are a bit of a variable. I don't know if it was in this thread or not, but someone made a comment that "a speakers rating is not what it can take constantly". Well, it depends on who's speaker and what rating system. I have used a LOT of Electro Voice gear over the years, and while on paper, they used to look to be lower power rated than a lot of their competition, a closer look at the ratings revealed why. EV used the RS-426 spec from the EIA for power testing, which states that a driver must be able to sustain the load for a minimum of 8 HOURS. The test signal is broadband noise, and in the case of the classic EVM-15B, was broadband from 40 to 318 Hz, and sloped off at 6db/octave above and below. The test signal was sent to an amp with a constant power level set to the rating of the driver (200w in this case) and a peak of 9db above that, or 1600 (yes, you read that right - 1600) watts in this case. And once again, the driver must have been able to survive this for 8 hours minimum to get a 200w rating. And then there is the voodoo/bulls**t home audio market where a 200w driver means 200w for 6 nanoseconds submerged in liquid nitrogen, on the dark side of the moon . . . . . (yes, I think most consumer gear is mis or fraudulently rated . . . ). But it does explain why pro stuff will take a hell of a lot more abuse than "consumer" gear with much higher printed ratings. The trick with our bass gear is to figure out exactly how it was rated . . . . .

- Tim

ALL excelent points indeed. The more we know as players, the better we can control our sound.

 

[strummer]

The trick with our bass gear is to figure out exactly how it was rated . . . . .

- Tim

Thank you for a very informative post.

How do we find out how it was rated?
I know what i do with amps: I just measure them with my PowerCube
But how to go about it with speakers? Can't fry speakers just for fun...
What are the different power handling specs and what exactly do they specify?

 

[tadawson]

The biggest problem is that to a certain extent, the speaker manufacturers are able to devise any rating scheme they so choose. One of the reasons I have always been fond of EV, is that they publish their rating methology, at least historically, in EVERY product data sheet that uses it. If a bass rig is using "standard" speakers, such as Eminence, I would hope that Eminence would document how they rated them for power handling, but there is no obligation. On the "custom to us" type of speakers, I don't know what you will get, since although they are made for Bass rig mfg. X, they are build by speaker company Y. Since they are a custom, the speaker company may refuse to give you that info, and since the bass rig mfg. did not design the speaker themselves, they may not know. THATs when it gets interesting . . . . . . .

Anybody that claims to use the EIA RS-426 spec (like EV) I would trust the ratings of. That is one seriously brutal test . . . . . but gives lower numbers than other ways, and since "11 is always better" seems to be the norm for most musicians, an honest rating with RS-426 will not sell as much gear as "Fred's rating system" which gives a much bigger number . . . . Now, if we could just get rid of all the lying, sleazy marketing pukes, then maybe we would be on to something . . . . .

- Tim

 

[BigBallz]

if we could just get rid of all the lying, sleazy marketing pukes, then maybe we would be on to something



good luck

 

[tadawson]

Hey! A guy can dream, can't he?

- Tim