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cab watt rating and head watt question


zinzin

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Originally posted by GCDEF



Underpowering a speaker can cause it to rip itself apart? How?


Does that mean you should avoid playing quietly?

 

 

I will get specifics if you want.

My friend is a live sound guru, and explained it to me once years ago. Frankly, I didnt pay attention because of anything Im always overdriving my cabs...

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Originally posted by No Soul

nahh, youre fine. When you crank the amp you are bound for some speaker distortion. Its actually worse to severely underpower a speaker

 

 

 

NOT TRUE. Only with Hi Fi or PA speakers do you want to have clean headroon as their horn drivers and tweeters (in the case of hi fi) are easily damaged with clipped power. This is NOT the case with guitar speakers which can easily handle distorted clipped waveforms (of coarse since we all love overdrive!). For guitar its generally BETTER to have speakers rated at almost twice the amp output IF you are going to crank the amp fully. Why? Because a fully cranked tube amp generally will produce almost twice its rated output. A 30 watt amp may put out 40-50 watted fully cranked. NOW if your going to run it conservetively then a 30 watt cab may be ok. HTH Bob

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Originally posted by No Soul

nahh, youre fine. When you crank the amp you are bound for some speaker distortion. Its actually worse to severely underpower a speaker

 

aren't you severely underpowering a speaker when playing on 1:confused:

 

or is like severely underpowered considered 10 watt amp to 50000 watt speakers.

 

now im confused :mad::confused:

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Originally posted by rockon1000




NOT TRUE. Only with Hi Fi or PA speakers do you want to have clean headroon as their horn drivers and tweeters (in the case of hi fi) are easily damaged with clipped power. This is NOT the case with guitar speakers which can easily handle distorted clipped waveforms (of coarse since we all love overdrive!). For guitar its generally BETTER to have speakers rated at almost twice the amp output IF you are going to crank the amp fully. Why? Because a fully cranked tube amp generally will produce almost twice its rated output. A 30 watt amp may put out 40-50 watted fully cranked. NOW if your going to run it conservetively then a 30 watt cab may be ok. HTH Bob

 

 

Bingo.

 

Live sound guys use the "don't underpower the speaker" guidline because they typically want as much volume as they can get but don't want to send any PA power amp disortion to the speakers. That's it. This of course doesn't apply to guitar.

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I say a thirty watt cab should handle a thirty watt head no problem. Vhoholic ( fellow formite) always played his 100 watt plexi head into Marshall 4x12 greenback 100 watt cab with no issues. Though he did use a Variac. Maybe you should too.

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Originally posted by Roccaforte Amps



So, to the thread originator, a 30watt cab on a 30watt amp is OK provided you're not running the amp on 10 at all times.

Doug

 

I always assume it is going to be cranked and recommend a cab will a higher than amp output rating. :)

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Originally posted by Roccaforte Amps







matching impedances doesn't protect a high power speaker from being burnt out by a low power amp.

 

 

You should qualify that statment. A low power amp won't burn out speakers. The distortion produced by to turning up a low powered amp to the point of hard clipping may, but low power by itself is harmless.

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Originally posted by Roccaforte Amps








I already did earlier:


FWIW FYI,

a 10watt amp clipping is more harmful/dangerous on a 100watt speaker than a 50watt amp.


The reason? Hard clipping in small amplifiers produces heat that can toast even the highest power voice coil.

 

 

Although IMO the point is somewhat moot as any tube amp will produce more than its rated output cranked (hence the need for speakers rated more than the amp ) I am curious why a 10 watt tube amp produces more "hard clipping " than a 50 or 100 watt tube amp when fully cranked. There are after all many who prefer cranking smaller tube amps for power tube distortion/saturation at less than ear bleed volumes. I have never heard they were more stressful to speakers than their larger brethren.

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