# Amp output & speaker power rating



## greco (Jul 15, 2007)

This is something that is not clearly understood by me. Please forgive me if the question is very basic and the answer is just as simple. I just had to ask.

If a speaker has a power rating of (say) 50 watts and one uses an amp of (say) 5 watts max output, will the speaker never deliver the full "tonal" potential that it is capable of ?

I'm not specifically talking volume here, but the ability to drive the speaker the point that one obtains the "best" of what the speaker can offer.

Is there a "rule of thumb" for this ? (i.e, it is best not to use a speaker where the max power rating is more than twice the max. wattage output of the amp...or whatever).

I hope these questions make sense...LOL

Thanks

Dave


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## greco (Jul 15, 2007)

26 views and no bites !!


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## mhammer (Nov 30, 2007)

All speakers (and amplifiers) have what is referred to as a "linear operating range". That is, a zone within which the speaker (or amplifier) delivers its intended optimal characteristics. Since speakers are essentially a modified piston, possessing a certain amount of inertia, it takes more than the tiniest bit of amp output to make the speaker move freely and respond as equivalently as it can to all frequencies. Ina great many instances, it can take a watt or more of power to make the speaker operate in this "cruising" range. For some speakers, the linear operating range can require much more than that. I used to own one of the early model Peavey Classic amps in the early 70's, and the speakers were annoyingly different at band practice levels vs gig levels. Totally different-sounding speaker tat often sent me running back to the amp to change the EQ from what had been appropriate at practice.

The linear operating range has not only a lower limit, but an upper one as well. When the cone and coil move too far (forward and backward), they can become less mechanically stable and diverge from their intended characteristics. Moreover, the "shock" of a sudden intense transient can result in vibrations in the cone itself. Use of paper, hemp, or whatever, can dampen that to some degree, but it ain't perfect. It is also the case that speakers with alnico magnets, rather then ceramics, can have slightly different characteristics at the extremes of movement. From what I understand, this would be partly responsible for the slight compression that alnicos are reputed to have.

For the most part, though, unless we are talking about 18-inch woofers intended to survive 300W, you can expect anything in the 8-12" range, that is rated as capable of handling 20-100W to be either in, or very near, its linear operatng range with 1-2W of power applied (this excludes sub-woofers, which can often possess very different characteristics). Do I know this for a fact? No. However, published efficiency ratings are taken at 1 meter with 1W applied and I strongly doubt manufacturers would want their products to not show up on the radar in terms of efficiency until 10W were applied. So, my guess is that they aim for cruising speed to kick in somewhere near 1W. Keep in mind that does not mean the speaker will be *loud*. But it should mean the speaker reproduces all the frequencies it is capable of at that power level.

Now, keep in mind that what guitarists like in a speaker is not its ability to reproduce all frequencies equaly, but rather the manner in which it behaves at higher volumes, and breaks up. I know of no rating system that aims to identify breakup point or sweet spot; particularly since pushing a 5W amp to its max would make it hard to know what part of the breakup is the speaker, and what part is the amp.

Does all of that make sense?


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## greco (Jul 15, 2007)

Thank you, Thank you, Thank you......YES, everything makes sense. 

After what you have explained, I have sent my question(s) to Eminence to see what their response would be. 
They have responded to my questions very quickly in the past.

It seems that this question was not as basic as I had thought.

Cheers

Dave


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## starjag (Jan 30, 2008)

mhammer said:


> Does all of that make sense?


It makes sense to me too. However, is the break up point always the sweet spot? Given what you stated, the sweet "spot" of a speaker could be rather flat and the speaker could operate in its "cruising" range over a wide volume range. But what if the break up point is your desired sweet spot? I hope I am making some sense


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## greco (Jul 15, 2007)

starjag said:


> ...... However, is the break up point always the sweet spot?


Thanks for the response starjag...interesting questions you raise.

I'm *guessing *that the sweet spot (for most players) is going to be just slightly following the break up point.

What do you think?

Cheers

Dave


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## parkhead (Aug 14, 2009)

Pa is different from Guitar 

for guitar 
You can get a 50 watt speaker to sound good with 3-5 watts 
you should not exceed the power rating of the speaker ie running a 25 watt greenback with a 30watt amp will cook it 

sensitivity is the key issue here 
when underdriving a speaker make sure you are using a good quality efficeint speaker with a lighter cone 

in some cases super high powered speakers ie 400 watt pa spekers might not move much with a 5 watt signal 

For PA 

you want to exceed the power rating of the speaker by a factor of 2 
provided you have good PA boxes with a protection circuit 

the extra wattage gives you headroom 
and decreases the likleyhood of distortion
the extra wattage will trip the protection circuit if you overdrive the box 

if you underdrive a 400 watt pat speaker with a distorted 50 watt pa amp
your the distortion will blow up the speaker and the protection will never trip 

Back to guitar speakers 
I often use 5 watt champ type amps with 
ev 12L 200 watt speakers and all sorts of celestions 

since these designs have effcient voice coil gaps that can work with the lower signal level of 
the small amp 

Speaker Wattage is a little bit of a misleading measurement since it is really just 
a measurement of the wattage at which a steady sine wave will make the voice coil melt and fail 

speakers have been going up in wattage over the years due to better heat dissipating glues and hi tech heat management techniques ...

however, cheap speaker designers raise the wattage rating by increasing the voice coil gap 
this allows better cooling but also decreases sensativity and efficiency 

I always campare efficeincy numbers when choosing guitar speakers all else being equal 
the higher effieciecy speaker will be louder with the same amp 

For example I swap out the 95 - 97 db efficent speaker in a 15 watt Traynor Guitar Mate for a 102 db 
vox celestion or Evm 12l
to match that same (sound power (db)) increase with the original speaker I would have to 
double the amps power 2x, and use a 60 watt amp 
every 3db increase in efficiency is equal to a power doubling 

I've used a Valve JR 5 watts with this type of speaker and it is as loud as a stock guitar mate 


With PA setups I look at the effieciency numbers as well since you can get BIG sound with an average small portable PA if you choose speaker boxes with higher efficiency drivers 

the best example of this is the old elite E600 or new e210 speaker box, a good portable pair of these tops will outperform most installed club systems and will Kill outdoors with the right sub support 

with full power applied those tops will push 128db 

hope this helps 
despite what I said about the importance of over powering PA speakers
If I had to do a gig with an 800 watt box mixer and be loud and clear I'd grab the most efficeint tops I could find 
again a 3db better speaker box is like a power doubling in actual sonic output 


p


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## greco (Jul 15, 2007)

*Parkhead* QUOTE "when underdriving a speaker make sure you are using a good quality efficeint speaker with *a lighter cone*" END OF QUOTE

Do the speaker companies usually indicate the "cone weight"/density (or whatever they might refer to it as) of their various speakers ?

Thanks for the detailed response.

Cheers

Dave


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## parkhead (Aug 14, 2009)

Nope your best measure to look at is the sensitivity measured in [email protected] 1 watt /1 meter
this will give you an idea of how much motion 1 watt can induce in a cone 

Celestion and emmience will give you this measure 
for years EV would not 
I suspect that was because with only 1 watt the ev speaker was not performing well at that spec

and EV would be an example of a speaker with a heavy cone & probably has a little more inertia to overcome 
with low powered signals 

For under 5 watt amps I would look at speakers like the Blue dog or vintage 30 

have a looks at these specs 
this is the emminence EVclone 

99.2 at 1 watt 
http://eminence.com/pdf/deltapro-12a.pdf

This is the super high powered version 
the kappa pro 

notice that as the power goes up the 1 watt sensitivity is going down 97.6
http://eminence.com/proaudio_speake...ink=KAPPAPRO-12A&speaker_size=12&SUB_CAT_ID=1

Then you have this the red fang with 103db @ 1 watt 
http://eminence.com/guitar_speaker_detail.asp?model=REDFANG&speaker_size=12&SUB_CAT_ID=4

the red fang will sound best in a low powered amp 

at least 2x as loud as the kappa with only a couple of watts 

Indirectly you might conclude that the fang has the lighter cone & reacts better to a smaller signal 

P


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## greco (Jul 15, 2007)

This is the response I received from Eminence. BTW...they were very quick to respond.

_Hi Dave,

Well, guitar speakers are typically very efficient.....meaning it doesn't require a bunch of power to push them effectively or to make them play loud. Sure, some speakers may sound "better" when pushed to their limits, due to break-up characteristics or natural compression, or the fact that your tube amp sounds "sweeter" when you crank it up. 

Another thing to understand is that our power ratings are basically just a thermal limit. In a lot of cases, there's really no good technical answer as to the "best" power for a speaker. It's often better to use good sound judgment. For instance, a particular 12" speaker may be rated at 150 watts or whatever, and won't actually blow if you put that much to it, but does it still sound musical and retain its good qualities with 150 watts on one 12" speaker? 

I hope that makes sense.

Thank you for using Eminence....we greatly appreciate your support! _

Parkhead...Many thanks for your post and for the links. This is all making more sense to me.

Cheers

Dave


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## Rugburn (Jan 14, 2009)

I know you like the cleaner sounds Dave. With that in mind, I think you'll be happy with a speaker that has higher power handling abillities. There's little doubt that a 50 watt speaker can still sound great hooked up to a 5 watt amp, but there won't be any real speaker break-up or distortion. Part of what makes little Champ-type amps sound the way they do is the smaller speaker. In the latest issue of GP Jeff Beck talks about his live rig. He uses a late 50's Fender Champ miked into a PA. All those Marshall heads are just for show. Conversely a 5 watt amp into a 4x10" cab is a different beast. Lots of air being moved and a big bottom that an 8" speaker can never deliver. My friend has a Ragin' Cajun in his Gibson Skylark and it sounds kind of dark. According to the Eminence site this is a very sensitive "bell-like chimey" speaker, but it's rated for 75 watts! I think his amp is rated for 10-12 watts. However, he can push that sucker as hard as he wants and it stays pretty tight and buttery.

Shawn


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## mhammer (Nov 30, 2007)

Both Parkhead's and Eminence's replies to this query make (you'll pardon the pun) eminent sense. Kudos to both.


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## greco (Jul 15, 2007)

"eminent sense"...great pun....nice way to end the thread.

Many thanks

Cheers

Dave


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## Bevo (Nov 24, 2006)

Great informative topic!


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