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Amp too powerful for cabinet


charic
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[quote name='owen' timestamp='1362694470' post='2003632']
It is not too many watts that does nasty things to cabs, it is too few being driven into distortion. I used to drive an NV610 with an 800w amp for many happy hours.
[/quote]

No it isn't. Otherwise valve amps would kill cabs all the time.

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[quote name='owen' timestamp='1362695791' post='2003664']
Sorry, would clipping be a better word to use than distortion?
[/quote]

same thing. Distortion is what happens to a waveform when its clipped. When you overdrive things, they are clipping. You get other sorts of distortion too tough.

Edited by Mr. Foxen
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[quote name='owen' timestamp='1362694470' post='2003632']
It is not too many watts that does nasty things to cabs, it is too few being driven into distortion. I used to drive an NV610 with an 800w amp for many happy hours.
[/quote]

That's basically true, but it depends on the clipping and on the cab.
Normally, clipping indeed creates a lot of extra amplitude in the high frequency area. Push that signal through a tweeter that is not designed to take it, and the tweeter may be ruined.

However, many amps have circuits to prevent this standard clipping, and many cabs lack the tweeter.

Without knowing this, I can also imagine cabs which have protective circuits or have tweeters that can handle the extra highs.


best,
bert

Edited by BassTractor
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You'll endanger your cab(s) far more by trying to drive them with an amp that isn't powerful enough than one which is (according to the bare specs) too powerful. Most speaker damage is the result of square-wave distortion which is what amps produce when they're pushed at or beyond their limits. If your amp is producing the volume you need whilst working well within its capabilities then happy days - technically you might be able to push the drivers beyond their excursion limits but with a good brand like a Berg I think you'll reach your desired volume long before that happens.

Just as an experiment I ran my old Eden 210 / 115 rig for a few gigs with a Camco Vortex 2.6 in bridged mono, which on paper produces around 2600w. The cabinets loved it, cleanest sound you ever heard, loud as you like and nary a hint of speakers complaining.

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[quote name='Wiggybass' timestamp='1362757376' post='2004376']
You'll endanger your cab(s) far more by trying to drive them with an amp that isn't powerful enough than one which is (according to the bare specs) too powerful. Most speaker damage is the result of square-wave distortion which is what amps produce when they're pushed at or beyond their limits. If your amp is producing the volume you need whilst working well within its capabilities then happy days - technically you might be able to push the drivers beyond their excursion limits but with a good brand like a Berg I think you'll reach your desired volume long before that happens.
[/quote]

All this is not true. Again, 50w guitar head into 300w 4x12, driven far into clipping. Also amplifiers can't put out square waves into cabs.

Edited by Mr. Foxen
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[quote name='dood' timestamp='1362758422' post='2004408']
Alex's BGM column for reading reference too. http://barefacedbass.com/uploads/BGM67%20Jun2011.pdf
[/quote]
Not to mention all the often lengthy threads that have covered this subject on this forum.

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The 'old school' rule was 2 x speaker watts for amp watts, to be 'safe', hence the 'double stack', 1 x 100w head, 2 x 100w cabs. Just a rule of thumb, though. It's also true that we (well, most of us...) knew f***-all at the time. No kw amps back then...

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Just FTR the Berg 6x10" is actually a 4ohm cab. Jim himself said it used 6ohm speakers. 6+6=12, 12/3=4. I [u]believe[/u] this was so it played nicer with tube amps, which lots of people use with the NVs.

Edited by Jack
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[quote name='Mr. Foxen' timestamp='1362758266' post='2004402']
All this is not true. Again, 50w guitar head into 300w 4x12, driven far into clipping. Also amplifiers can't put out square waves into cabs.
[/quote] Sorry, don't follow the reference - which bit of the guitar amp is / was being driven into clip - pre amp or power amp? Or both?

And why can't amps put square waves into cabs?

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[quote name='Wiggybass' timestamp='1362911648' post='2005993']
Sorry, don't follow the reference - which bit of the guitar amp is / was being driven into clip - pre amp or power amp? Or both?

And why can't amps put square waves into cabs?
[/quote]

Usually both for that famous Marshall brown sound.

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[quote name='Wiggybass' timestamp='1362911648' post='2005993']
Sorry, don't follow the reference - which bit of the guitar amp is / was being driven into clip - pre amp or power amp? Or both?

And why can't amps put square waves into cabs?
[/quote]

Any of it, doesn't matter, clipped waveform is the same.

Square waves require infinite bandwidth, and perfect cab behaviour (impedance, inductance etc.) and both amp and cab limit that. The limitations act to round off the square, limit enough and you bring it back to a perfect sine.

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[quote name='Mr. Foxen' timestamp='1362928638' post='2006289']
Any of it, doesn't matter, clipped waveform is the same.

Square waves require infinite bandwidth, and perfect cab behaviour (impedance, inductance etc.) and both amp and cab limit that. The limitations act to round off the square, limit enough and you bring it back to a perfect sine.
[/quote] Clipped waveforms might be technically the same but the massive difference in amplitude is what's relevant concerning potential speaker damage. The miniscule voltages in the preamp could never be enough to damage a driver, whereas a power amp driven into clip and / or oscillation will definitely damage transducers if left for long enough (and that may not be very long if it's a low-powered driver). Ask anyone who does recones, they'll tell you what kills drivers.

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[quote name='charic' timestamp='1362933098' post='2006371']
Wiggy, I would generally side with Foxen on these matter. Chap knows what he's talking about when it comes to amps :)
[/quote] I don't doubt it for a moment - but I say again, ask anyone who recones drivers (and I mean professionally) and every single one will tell you that almost all damage to cone transducers is the result of being continuously driven by power amps producing unintentionally distorted signals for extended periods. There's no mistaking the difference in the damage between this type of damage and that caused by over-excursion.

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[quote name='Wiggybass' timestamp='1362932171' post='2006358']
Clipped waveforms might be technically the same but the massive difference in amplitude is what's relevant concerning potential speaker damage. The miniscule voltages in the preamp could never be enough to damage a driver, whereas a power amp driven into clip and / or oscillation will definitely damage transducers if left for long enough (and that may not be very long if it's a low-powered driver). Ask anyone who does recones, they'll tell you what kills drivers.
[/quote]

Clipping and amplitude are entirely unrelated. Clipping limits amplitude if anything. Overpowering damages speakers, waveform bears no relevance.

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[quote name='Jack' timestamp='1362933534' post='2006375']
Wiggy, go plug your ipod into a PA speaker cabinet and really crank it up so it clips. See how long it takes for that horrendous case of underpowering to blow the speaker.
[/quote] Crank what up? The iPod or the speaker?

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[quote name='Wiggybass' timestamp='1362933632' post='2006376']
I don't doubt it for a moment - but I say again, ask anyone who recones drivers (and I mean professionally) and every single one will tell you that almost all damage to cone transducers is the result of being continuously driven by power amps producing unintentionally distorted signals for extended periods. There's no mistaking the difference in the damage between this type of damage and that caused by over-excursion.
[/quote]

If your reconer says that, you'd be better off finding a reconer who knows what they are talking about.

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