Passinwind
I know nothing.
- Dec 3, 2003
- 23,077
- 46,035
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- Designer/Toaster Tech @ Passinwind Electronics
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Watts; the worst measurement unit ever for amp output?
- Thread starter nukes_da_bass
- Start date
In virtually all cases, watt ratings are derived from voltage measurements. From an engineering standpoint, it works if you understand how it is measured, and the limitations of the methods being used.
Converting it to "watts" with no explanation or qualification is where things go downhill.
Converting it to "watts" with no explanation or qualification is where things go downhill.
Louder is not necessarily better.
You and I agree about this… However, even though I think the best sounding amplifier ever in the whole entire world is the Ampeg Portaflex B15, I would not try a modern world gig with one I'm not as much of a man as Jimmy LOL
I am learning things from this thread, however. I don't think I've ever seen the statistic "voltage swing" in a specification sheet Will33....sounds like that would be a good statistic for amplifier manufacturers to list!
Passinwind
I know nothing.
- Dec 3, 2003
- 23,077
- 46,035
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Dig that, Bro. I use a 1000 watt amp for coffee shop and winery gigs, for real.
To use the voltage swing ( is that RMS, Peak or PeakToPeak) is a problem as the standard(s) is 1 watt into 8 ohms at 1 metre. That gives approx 2.83V. One of the sensitivity standards quotes this as a voltage for measurement of sensitivity. However if you use this for a 4 ohm speaker you get a 3dB sensitivity improvement for the same model on the 4 ohm model.
Then you have the problem of where on the cone you measure the 1 metre from. You and I would take the front of the driver chassis but some manufactures. Measure from some point on the cone. This could make a difference in distance of say 10cm (4" approx).
One of the things you can check is the official power consumption figure on the back of the amp. If it says 100 watts on the back where the voltage and current ratings are shown, it Cannot output more than 95 watts assuming a really well designed Class D amp.
You'll find the voltage stuff in datasheets for real poweramps, pro sound type stuff, with qualifications for how they were arrived at, etc.
You'll find lots of stuff in there you'll never see for a typical bass amp/musicalIstrument amp.
Not saying they need to lead their advertisements with the nerd stuff, but it'd be nice if they had a page of hard data at the back.
Musical instrument amps are voiced to sound a certain way, distort on purpose, etc. Their goal is rarely clean/flat from 20-20k, but you can still measure and publish all that stuff.
You'll find lots of stuff in there you'll never see for a typical bass amp/musicalIstrument amp.
Not saying they need to lead their advertisements with the nerd stuff, but it'd be nice if they had a page of hard data at the back.
Musical instrument amps are voiced to sound a certain way, distort on purpose, etc. Their goal is rarely clean/flat from 20-20k, but you can still measure and publish all that stuff.
If you prefer, Mr. Munji, sir, it's my opinion that my Eden E300 T lacked the presents and punch of my mesa 400+ also.
It wasn't my intention to set this up as solid-state versus tube-. It was more like watts versus other types of statistics and metrics.
I think I've just been Munji'd!
Mr. Foxen
Commercial User
Done properly its measured at 4m and then corrected to account for not being a perfect point source.
Standards for measuring audio gear is not really a problem. The industry has defined how to do that. The problem is, manufactures hire a lot of creating writers to characterize how their products perform. This can get mighty confusing.
The problem is how does a player know which amp is best for them? Your ears might tell you if you have a chance to audition or hear a piece of gear. Getting to know an amp and how to dial it in can take time. If your are patient, eventually you figure it out. Often it takes more time than you have with a simple demo. Some people are impatient and if the amp doesn't give them what they are looking for right away, they move on. Otherwise it comes down to buying and selling gear, looking for that elusive holy grail of tone. Some people are lucky and they easily find what they like, for others it's a lifelong quest.
The problem is how does a player know which amp is best for them? Your ears might tell you if you have a chance to audition or hear a piece of gear. Getting to know an amp and how to dial it in can take time. If your are patient, eventually you figure it out. Often it takes more time than you have with a simple demo. Some people are impatient and if the amp doesn't give them what they are looking for right away, they move on. Otherwise it comes down to buying and selling gear, looking for that elusive holy grail of tone. Some people are lucky and they easily find what they like, for others it's a lifelong quest.
That is really easy............
Every amp would be rated at 0db @ any range, because amps do not put out db's - speakers do.
I am tempted but the Pint of Fursty Ferret in front of me calms me to the point that I can resist the taunts of the evil thermionic trolls.
Now that is a tube I can defend!
dB ratings at any distance would be totally dependent on the speaker cabinet being used.
Not quoting you to say you don't know what you're doing or anything like that, just using it as a way to start the post.
There are plenty of folks on here with much, much more knowledge and experience than me who could expound on this.
Just to strip things back to the very most basic of levels, ignoring for now the thousands of other things involved in amplifier design.
At it's "core" per se, an amplifier is not a "watt generator" but rather it is a "voltage multiplier".
Take for a minute the "battery test" we use on speakers (search there here anybody who doesn't know what it is)........when you put the battery across the terminals one way, the cone moves outward, lets call this "positive voltage". When you reverse the battery and put it across the terminals the opposite way, the cone moves inward, lets call this "negative voltage". This is what an amplifier does, really, really fast.
The 9 volt battery will make the cone jump further than a 1.5 volt battery (typical AAA, AA, C, D, etc.). The more powerful amplifer (the one that can produce more "voltage swing...positive to negitive and back again) can also make the speaker move farther (play louder) than the smaller amplifier (the one with less voltage swing) just like comparing the 9 volt battery to the 1.5 volt battery.
This same principle goes all the way back to the beginning.....your metal strings vibrating back and forth over the pole pieces in your pickup (which is also magnets wrapped in wire). That vibration makes a very small "voltage swing" which the amplifier then multiplies....or "amplifies" into a larger voltage swing. That voltage "swinging" back and forth from positive to negative and back again is what makes the speaker move in and out to produce pressure waves in the air to produce sound our ears can hear.
"Watts" never enter the picture anywhere in this whole business from beginning to end. They are rather a measurement of heat....heat that the speakers voice coil must get rid of somehow without burning itself up.
The "watts" vary with the impedance of the speaker load the amplifier is "driving" or "pushing".
X amount of volts into 8ohms = X watts
X amount of volts into 4ohms = more watts
X amount of volts into 2ohms = even more watts
It's Ohms Law. The amount of "voltage swing" the amplifier is doing is the same in all 3 of those cases.*
* = in theory it would double but oftentimes doesn't quite all the way double due to other losses in the circuitry/design and/or the ability of the power supply to "keep up", etc.
Tube amps use an impedance matching transformer on the output to stabilze this. That is why they can put out the same "watts" into various impedances. When calculating their "power", you still use voltage swing. Without "swinging" voltage, the speaker wouldn't move.
Now.....somebody else poke that full of holes and bring up one or more of the many thousands of variables.......shouldn't be too hard.
Of course. And no amp manufacturer would list anything but their own branded speaker cab as a measure of DB out of, but they COULD state "this amp puts out xx DB at 30 meters into our blah blah brand 4x10 which has a sensitivity rating of Y".
"Watts" never enter the picture anywhere in this whole business from beginning to end. They are rather a measurement of heat....heat that the speakers voice coil must get rid of somehow without burning itself up.
Well, there you go making my point even better than i could. Watts are a terrible rating system for amplifiers.
If i buy a heater or a stove i will look for a unit which measures heat
Well, there you go making my point even better than i could. Watts are a terrible rating system for amplifiers.
If i buy a heater or a stove i will look for a unit which measures heat
Just another thing to think about.. Watts for amplifiers are figured as DC watts into a fixed resistive load. They are not computed into a reactive load such as a speaker. What I am trying to get at is if you measured the DC resistance of your 8 OHM speaker it would measure (I think) 5.73 ohms. The actual reactive impedance is 8 OHMS which varies as frequency changes. I would think that when certain amps are plugged into a speaker they don't perform at the power they were originally spec'd at due to the nature of the reactive load (speaker) ... also some companies spec their amps at 5 or 10 percent THD (as previously mentioned) so you need to look at all of this to get an accurate assessment of power. I used to calibrate power amps and rf amps and they all calibrated using a resistive load.. We used to call it specsmanship by all the amp companies.!!
If you want output voltage, just calculate it from the rated power and load resistance.
That's what was actually measured to begin with anyway (typically). And that value
will tell you no more or less than the wattage did.
Also amps are power amps. And not all the output is heat; if it was you wouldn't hear
anything. A portion is converted into acoustic watts, depending on the cabinet
efficiency.
.
That's what was actually measured to begin with anyway (typically). And that value
will tell you no more or less than the wattage did.
Also amps are power amps. And not all the output is heat; if it was you wouldn't hear
anything. A portion is converted into acoustic watts, depending on the cabinet
efficiency.
.
