Wattage.
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Posted on Jan 09, 2008 06:29 pm
Rob Stemple
The Czar of BS
Member Since: Dec 31, 2007
I know in my last post, I stated that wattage means nothing. I realize, to an extent, that this is both true, and not ture. So, I wanted to take the time to clear that up. Wattage by definition is , the amount of energy required. And by using Ohm's Law, we can find how to slove for wattage in several ways. But, that is not what this post is about. This post is about giving a clear understanding of what watts means to us in this industry. Wattage means two different things to two different devices. To an amp, it refers to the amount of energy supplied. To a speaker it refers to two seperate things, the amount of energy it takes to run the speaker. And, how much it can handel. With an amp, it's pretty obvious what the corraltion is. Wattage is the energy it is producing at a givin ohm load. Voltage squared divided by resistance equals watts. Speakers are receiving power. So, for them it translates into heat. How much heat they can disapate. When you look at your speaker box, it gives you a watt rating. This rating is the max amount they can handel continuosly. Some times it is written as RMS (Roots Means Squared). Continuous, and RMS ratings mean, you can run your speaker all day, and all night, with out a problem. Sometimes, there is a "Peak" rating as well. This menas that your speaker can handel a very quick burst of higher wattage. At what ever the Peak rating is. To exceed these ratings will result in damage. By going inexcess, you are over heating the voice coil of your speaker. Which will result in perminit damage. So, when someone tells you that they have a 500 watt system, you see how meaningless this is. 500 watts to what? One driver in the box, the whole box is 500 watts? The amp is only 500 watts? Wattage does not equal volume. So, to refer to your system in wattage, will not tell anyone about your system at all. I hope this helps you understand a little more about your systems. If you need more assistance on this matter, I will be happy to give a more indepth view of it.
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Jan 09, 2008 06:37 pm good comments.
Often in the car audio industry (esp. the el cheapo stuff) they quote their amps as being 1000 WATTS OF PURE POWER INTO TWO CHANNELS...
when in reality it's 250 x 2 RMS power.
I do have a question though, what if you have speakers that can say, handle 100 Watts, RMS, but you have an amp that will put out 200 Watts, RMS.
Will you blow them eventually if you keep the volume down, or is it just when you crank the amp you're going to melt voice coils?
Jan 09, 2008 07:59 pm Good question! Buy lowering the volume you lowering the voltage. So, looking at the formula of volts squared divided by resistance. You can see we are lowering the wattage. So, yes you can run a 200w amp on a 100w speaker. And yes, when you crank it, your raiesing the voltage, and will damage the voice coil.
Jan 09, 2008 08:14 pm Forgot to add some information. Another thing you can do is add some speakers in series. This will add resistance and reduce wattage.
Jan 10, 2008 02:00 pm Ahh, so the voltage is lowered! makes sense. Thanks!
TadpuiI am not a crook's headMember
Since: Mar 14, 2003
Jan 10, 2008 03:02 pm I've done a lot of reading on forums about guitar cabinets and perceived volume. Here's the way I've come to understand it, maybe this applies to other types of cabinets/power sections as well:
A 100-watt amp will only be slightly louder than a 50-watt amp.
A 100-watt amp will only be twice as loud as a 10-watt amp.
A 100-watt amp and an 80-watt amp will be almost indistinguishable in loudness.
Of course this is taking out all of the other variables that affect perceived volume in guitar cabinets like:
- speaker efficency
- cabinet design
- gain structure/circuit design
Also for tube amps, you usually get more loudness per watt than solid-state amps provide. A 100-watt tube amp will be waaaaay louder than a 100-watt solid-state amp.
Raw wattage is usually only part of the formula, but this definitely gets you thinking about how much power you'll probably need when it comes to choosing a gigging amp.
But pure volume isn't the only factor for choosing a gigging amp. Clean headroom is a big deal as well. If you want a dynamic, punchy sound at high volumes, then you'll need considerably more wattage than if you play with lots of distortion.
For instance, a 5W tube amp is generally loud enough to keep up with a drum kit in a practice or small gig situation. But it could probably only do so if it were cranked all the way up. Anybody who's played through a tube amp knows that when the master is cranked, the power section breaks up and distorts (in a good way). If you wanted to play at that same volume with no breakup, you'd need considerably more wattage so that you can stay within the amp's range of clean headroom.
Jan 10, 2008 03:04 pm [quote]A 100-watt amp will only be slightly louder than a 50-watt amp.
A 100-watt amp will only be twice as loud as a 10-watt amp.
A 100-watt amp and an 80-watt amp will be almost indistinguishable in loudness.[/quote]
****** audio-metric system...
BeerHunterwww.TheLondonProject.caMember
Since: Feb 07, 2005
Jan 10, 2008 03:06 pm I'll share with you what I know about wattage....
40 watts of tube power is plenty loud!
TadpuiI am not a crook's headMember
Since: Mar 14, 2003
Jan 10, 2008 03:10 pm Hahaa BH you're right! Especially if that 40 watts is coming from one of those Fender HotRod DeVille or Deluxes! Those things are some of the most efficient 40-watt amps on the planet.
I think that the Vox AC30 takes the cake though. Its a 30-watter that could probably keep up with most 100-watters!
And dB I know what you mean...the whole logarithmic scale makes my head spin.
CptTrippsCzar of Turd PolishMember
Since: Jun 20, 2006
Jan 10, 2008 03:14 pm 50W of tube for this guy!!
Jan 10, 2008 05:35 pm I wanted to reply to Tadpui on his post. Yes you are correct about the coralation of watts. Here is the key. For every 3 db you double the volume, for evey 10 db you double the power. This formula affects the input voltage. Finally translating into wattage. This is where you see the input sensitivity rating on an amp. Most guitar amps have the same input sensitivity from either 1 or .707 (.707 is RMS). Depending upon where you turn you volume knob to, is determening how much your preamp is putting the input voltage. 0 - 1 volt. (Unity) So, input, affects the output, which effects wattage. Now,let's say you have an amp having a rating of 100 watts. Does this mean that it will never exceed 100 watts? No. Depending upon the input sensitivity, you most definitly exceed 100 watts. This is where the differance between tubes and solid state comes in. Solid state is a transistor. The transistor will only amplify so much before it starts to flatten the wave. (Clipping) Tubes, will keep going until they burn out. Instead of clipping, you get distortion. And this is why you see the come back of the tube amp. The more you drive the input, the more the tube trys to deliver the output.
