Low watt amps + High wattage speakers = ???

strumminsix

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4,196
Hey gang! I have a Pro Jr coming in this week thanks to a fellow TGPer. She has the original speaker (USA made so guessing Eminence?) and was contemplating popping in some other speakers and testing. I have 2 I can use:

- Jensen neo (but would have to unsolder, etc, etc
- EV Force 10 (just waiting for something to happen!)

Then I started wodnering if an amp pushing out 15W can properly mate with a 150W speaker.

Rationale beyond "just try it, dude" is that I know with a PA if you significantly under-power a speaker it causes cone rub which leads to all sorts of trouble....

Thanks!
 

Stevie_j

Member
Messages
76
Rationale beyond "just try it, dude" is that I know with a PA if you significantly under-power a speaker it causes cone rub which leads to all sorts of trouble....
It will work fine, under-powering speakers will do no harm, a speaker is never amaged by too little power, just by too much. The argument is that when you have a speaker matched to the RMS power of the amp, when you clip the amp, you can provide 2x the RMS power to the speaker because you have raised the average level of the signal due to creating something approximating a square wave.
 

strumminsix

Member
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4,196
Steve, an old friend who was trained and certified sound engineer stated that underpowering a speaker can cause rub (maybe I got coil or cone wrong). He said without the enough power the speaker doesn't follow it's designed path of movement leading to fluttering which causes rub. He said it's very similar results to over powering but your ears will hear over power power first but you'll never know when it will strike.

Mind you his specialty was PAs (national acts) but said similar principals applied.


(lost track of one another years back or would ask him directly)
 

Dale

Member
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10,312
I have never seen a speaker designed for an amp die due to too little power. I am not saying it can't but I have never seen it and never talked to someone personally who saw it themselves either. I have run my Killer Ant thought speakers from 50W to 150W for many many hours. It has never hurt one. The Blues Jr I had came with a 50w speaker. It never seemed to die. I have put a fair number of hours though both those. My 12w-18w 5e3 d has been running a C-Rex (50w) for a couple years it has never killed the speaker. I just do not really see it.

I do know you may not see much (probably no) speaker break-up. So if that is important to your sound that will be missing from it.
 

strumminsix

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4,196
Thanks, Dale! Real world experience is always better than theoretical or super cautious planning. Maybe reality is that it takes a much higher rated speaker with a much lower output then what we are talking about for guitar amps!
 

GCDEF

Silver Supporting Member
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28,165
Steve, an old friend who was trained and certified sound engineer stated that underpowering a speaker can cause rub (maybe I got coil or cone wrong). He said without the enough power the speaker doesn't follow it's designed path of movement leading to fluttering which causes rub. He said it's very similar results to over powering but your ears will hear over power power first but you'll never know when it will strike.

Mind you his specialty was PAs (national acts) but said similar principals applied.


(lost track of one another years back or would ask him directly)
Your friend is wrong. There's no such thing as underpowering a speaker. What do you think happens when you turn the volume down? That's just one of those goofy internet myths spread by people who know just enough to get it all wrong.

As to your original question, as long as the speaker can handle the amp's rated power, you'll be fine.

Here's a pretty good article from Peavey.
http://www.peavey.com/support/technotes/poweramps/HOW_MUCH_POWER.pdf
 

strumminsix

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4,196
Well I'll just STFU then say thanks to each of ya!

BTW - my buddy never logged on to the internet at the time. I am guessing that this myth was around before TGP :) However, learning about a poweramp spitting out TWICE it's watts when hard clipping makes me believe why this myth seemed logical in application.

Thanks so much for the link it answers so many questions!

Now, onto another stupid question: does a guitar speaker sound better with rating nearly matched or just different?

Figure I'm already looking like a fool might as well get this last one covered before hiding my head in the sand!
 

GCDEF

Silver Supporting Member
Messages
28,165
Well I'll just STFU then say thanks to each of ya!

BTW - my buddy never logged on to the internet at the time. I am guessing that this myth was around before TGP :) However, learning about a poweramp spitting out TWICE it's watts when hard clipping makes me believe why this myth seemed logical in application.

Thanks so much for the link it answers so many questions!

Now, onto another stupid question: does a guitar speaker sound better with rating nearly matched or just different?

Figure I'm already looking like a fool might as well get this last one covered before hiding my head in the sand!
Nearing its rating you may get some compression and some speaker distortion. I don't care for that sound myself, but some people do. Bottom line though is you really can't tell much about a speaker's sound or performance by its wattage rating.
 

5150user

Member
Messages
1,503
15 Watt Amp + 150 Watt Speaker = A setup that will have no speaker breakup, and the speaker should last a LONG time. Expect something akin to more clean headroom, due to no speaker breakup.
 

strumminsix

Member
Messages
4,196
Thanks guys! Usually when I like an amp it's because it's clean and can breath.

For Twins I usually bias them a little hotter so they can breath!

I do not really care for speaker compression (see breath) nor do I find speaker distortion all that musical!

Thanks so much for all the help here!
 

vashuba

Silver Supporting Member
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1,670
so by breakup, it that the tube overdrive? i have a fender musicmaster and need to replace the speaker. came across a deal on a jensen c12k 100w. will that not do this amp justice?
 
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6,116
I'm more concerned about speaker efficiency than power handling.
Especially with low power amplifiers and 12" speakers.
GIVE ME ALL YOU GOT!:banana
 

fetishfrog

Member
Messages
9,252
Steve, an old friend who was trained and certified sound engineer stated that underpowering a speaker can cause rub (maybe I got coil or cone wrong). He said without the enough power the speaker doesn't follow it's designed path of movement leading to fluttering which causes rub. He said it's very similar results to over powering but your ears will hear over power power first but you'll never know when it will strike.

Mind you his specialty was PAs (national acts) but said similar principals applied.


(lost track of one another years back or would ask him directly)
I think there's a measure of truth in this. If you under power a PA speaker, you may run the risk of the following scenario: As you begin to push the PA to the desired volume, you increase the risk that the power amp will run out of headroom and begin to distort, sending some rather 'speaker unfriendly' distortion and transients down the line. This could potentially damage the speaker in question. Jay Mitchell or DC1 could probably shed a more educated light on this than I could though.
 

daddyo

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11,797
I think there's a measure of truth in this. If you under power a PA speaker, you may run the risk of the following scenario: As you begin to push the PA to the desired volume, you increase the risk that the power amp will run out of headroom and begin to distort, sending some rather 'speaker unfriendly' distortion and transients down the line. This could potentially damage the speaker in question. Jay Mitchell or DC1 could probably shed a more educated light on this than I could though.
So if the power amp distorts and issues forth "speaker unfriendly transients," why would a speaker with a high watt rating be more susceptible to damage than a speaker with a low watt rating?
 

strumminsix

Member
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4,196
fetishfrog - from doing a MST (metric shhhht ton) of reading today I am gathering it looks like this: under powering is fine until you distort the poweramp. At that point you have 2 risks: square waves get or power peaks both which can kill your speaker.
 

fetishfrog

Member
Messages
9,252
So if the power amp distorts and issues forth "speaker unfriendly transients," why would a speaker with a high watt rating be more susceptible to damage than a speaker with a low watt rating?
I don't think it would. I do think if you had speakers that were rated lower, you'd be less likely to want to push them hard. It's the 'these speakers can take it' approach that costs you.
 

Stevie_j

Member
Messages
76
So a full page of discussion to arrive at the conclusion that my post was right.

To the OP, just because someone is good at mixing and tours with world class acts doesn't mean they know all the the theory, I work as a sound engineer at all levels of gigs from bars to stadiums (wish I got the top acts though, I've only been working pro for 3 years so I still have loads to learn and get hired by support acts, so I still have loads to learn.)

Anyway, some of the touring engineers are lacking in theory, I usually pick their brains to learn more if they will have time for me. Most of the time it's enlightening, but I've had the odd ones that ******** and ones that flat out admit they haven't a clue.

If you want to learn from a sound engineer, go talk to a system tech. They may not look as cool because they don't stand behind something that looks like a spaceship, but they shure as hell need to know their stuff.
 




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