Wattage? 10w+10w vs 20w ?

[Odedi]

Hi,
So this subject is a mystery to me.
Firstly, Is Wattage an indication of volume output?
Secondly, When an amp states that its 10w+10w, does it actually equal 20w?
I read somewhere that 10w + 10w is still 10w.

I also read that when you go up the wattage, the relation is not linear.
For example if I have an 30w amp, and decide to get a 60w amp, the volume output wont be actually doubled.

Would love some clarification,
Sorry if I mixed some stuff here. As i said, my knowledge here is minimal.

Thanks!

[jonfields45]

10+10 watts equals 20 watts, but that will be only be 3 dB louder which is often not very noticeable.

Our hearing is logarithmic so that we can hear the tiger crouching in the jungle and the local volcano eruption with the same ears.

10log(power) is the formula for decibels and to double the number of dB you need power^2, which you might perceive as twice as loud.

[Bob Womack]

That is to say, you need ten times the amount of wattage to double the volume level, all other factors remaining equal. A 200 watt amp can sound twice as loud as a 20 watt amp, if they are measured the same.

Speaking of which, for years the standard for rating power amps was called RMS, or Root Mean Square. RMS value was roughly one-half of peak power. An amp rating expressed in RMS was pretty dependable. Then amp manufacturers convinced the FTC to allow other methods, and things got grey and hard to gauge.

And, on the other issue, 10+10 watts tells you that the amp is a stereo amp. A 20 watt amp delivers 20 watts in mono to its speaker array. A stereo 10+10 watt amp breaks up the speaker array to two groups fed by two different amps, each feeding 10 watts. The difference in loudness will be minimal but the stereo amp can reproduce stereo effects.

Bob

[Odedi]

That's interesting.
So are there other factors that affect the volume output?

From my personal story,
I want to get a 60w fishman LBX mini charge for busking,
Instead of my 10w+10w(on batteries) roland ac-33, because on max volume it's still hard to hear out there.

Someone told me here that the fishman is much louder.
But according to the watts formula, there isnt a big db difference.

Also I had the Cube street which is rated 5w+5w , yet it was a lot more powerful than the 20w Roland AC33.

[jonfields45]

Originally Posted by Odedi

That's interesting.
So are there other factors that affect the volume output?

From my personal story,
I want to get a 60w fishman LBX mini charge for busking,
Instead of my 10w+10w(on batteries) roland ac-33, because on max volume it's still hard to hear out there.

Someone told me here that the fishman is much louder.
But according to the watts formula, there isnt a big db difference.

Also I had the Cube street which is rated 5w+5w , yet it was a lot more powerful than the 20w Roland AC33.

We have been discussing amplifier power rating, not sound pressure level. You need to look up SPL specs for those products to properly compare.

SPL is the gold standard of professional audio but even it is only truly useful to compare products from the same manufacturer (where the same methods were likely used for measurement). You will be shocked that products with twice the power don't get close to the 3 dB you might expect in extra SPL.

I've owned the AC-33 and the LBMini Charge and the Charge is perceptible much louder. Likely the tiny speaker drivers in the AC-33 are not very efficient.

Also, Roland is using a power rating methodology for their battery products much different than Fishman which produces inflated numbers. I am pretty sure Bose does not even publish power numbers for their S1 as they are not very useful numbers these days for comparison.

Bottom line you need to try these things in-person and be prepared to return an item that fails.

I think this is a classic funny power story. QSC doubled the power going from the K to the K.2 products (but the +3 dB SPL is not there!). I can't think of a single AGF review that says they seem louder. But, the bigger fan needed to keep the more powerful amp running if you actually pushed it is noticeably louder and routinely reported as unacceptable on the AGF. Useless extra power destroyed the quiet room usage for those products.

[Odedi]

Originally Posted by jonfields45

We have been discussing amplifier power rating, not sound pressure level. You need to look up SPL specs for those products to properly compare.

SPL is the gold standard of professional audio but even it is only truly useful to compare products from the same manufacturer (where the same methods were likely used for measurement). You will be shocked that products with twice the power don't get close to the 3 dB you might expect in extra SPL.

I've owned the AC-33 and the LBMini Charge and the Charge is perceptible much louder. Likely the tiny speaker drivers in the AC-33 are not very efficient.

Also, Roland is using a power rating methodology for their battery products much different than Fishman which produces inflated numbers. I am pretty sure Bose does not even publish power numbers for their S1 as they are not very useful numbers these days for comparison.

Bottom line you need to try these things in-person and be prepared to return an item that fails.

I think this is a classic funny power story. QSC doubled the power going from the K to the K.2 products (but the +3 dB SPL is not there!). I can't think of a single AGF review that says they seem louder. But, the bigger fan needed to keep the more powerful amp running if you actually pushed it is noticeably louder and routinely reported as unacceptable on the AGF. Useless extra power destroyed the quiet room usage for those products.

Thank you for the clarity!
I initially thought that "W" equals "Power" which equals "Loudness".
That could be a marketing strategy to lure some people in.

[RedJoker]

Or, think of the horsepower in a car. Sure, more horsepower might be faster but that depends on the tires, the gearing, the suspension, etc. All things being equal, more horsepower is better. But drop 1000HP in my Honda Civic with it's worn out suspension, old all-season tires and I'm still not going down the track very fast.

Side note, 1 HP = 745 Watts. Can we all agree to list our PA systems in horsepower?

[Bob Womack]

And hen there is speaker efficiency. Squirt 20 watts into a speaker mounted in an infinite baffle and you get one loudness. Squirt 20 watts into the same speaker mounted in an acoustic suspension cab and you drastically reduce the efficiency and thus the volume output.


Bob

[James May]

Originally Posted by RedJoker

Or, think of the horsepower in a car. Sure, more horsepower might be faster but that depends on the tires, the gearing, the suspension, etc. All things being equal, more horsepower is better. But drop 1000HP in my Honda Civic with it's worn out suspension, old all-season tires and I'm still not going down the track very fast.

Side note, 1 HP = 745 Watts. Can we all agree to list our PA systems in horsepower?

I can agree to that. But it means I'm going to need 10 horses in order to sound twice as loud as one horse.

[shufflebeat]

Originally Posted by James May

I can agree to that. But it means I'm going to need 10 horses in order to sound twice as loud as one horse.

Good logic.

Can we then agree that 10hp (horse power) is equal to 1hc (hungry child)?

Also worth acknowledging that some amps like PA power amps are designed to sound clean and work efficiently while others (guitar amps) can be designed to imbue character to the tone, sometimes deliberately using "inefficient" components and circuits.

[Mr. Jelly]

Here is a way that I looked at it. For live sound not recording. I don't know where I picked it up from. For a person to hear an increase of volume it takes approximately 3db of an increase. To increase the volume via an amp by 3 db you have to double the wattage. So to increase the volume of a 10 watt amp by 3 db you have to go to a 20 watt amp. Or two 10 watt amps. To increase an additional 3 db you need to go to a 40 watt amp. And it continues to 80 watts for an additional 3 db and the 160 watts for another 3 db.

[srbell]

Speaker efficiency is a major factor. When you see the wide variances in speaker efficiency (usually spelled out as a certain db for a watt of power at a given distance) you'll realize just how important it is. There can be many db differences, which would require huge differences in power to get the same volume from.

[Peter Z]

Another vote for effciency as the most important factor in the game.

There are hornloaded speakers with 110 dbm @ 1 watt and there are speakerss that spec 80 dbm @ 1watt.
And there you have the logarithmic thing again that jonfields mentioned: It means the speaker has to be powered with 1000 watts to get the same volume the other speaker produces with just 1 (one!!!) watt.

[Br1ck]

If you were ever to have told me I'd be running a 3 watt amplifier in my home stereo system, I'd have told you you were crazy, but here I am with a single ended triode amp into a horn enclosure rated about 105 DB efficiency.

It has also become the norm that for marketing, amps are rated at peak power. So take the 300 watts, halve it, then halve it again and you get 75 watts, but how can you sell that?

So efficiency and to some extent speaker size dictates loudness, then you need to take in the quality sound your gear puts out running flat out. You really need to try it in the real world.