What actually determines volume power? Is it watts?

dman77

For every 3 db SPL increase in output volume requires a doubling of the amplifier watts being used. So if your speaker sensitivity is 88 db, which means that it takes 1 watt of amplifier power to drive that speaker output to 88 db at 1K Hz measured 3 feet away. It will take 2 watts to drive it to 91 db, 4 watts to get to 94 db, 128 watts to get to 109 db and 256 watts to get to 111 db and that is before we consider the effects of the inverse square law which states that you will loose 6 db of SPL for every doubling of distance from the source.

To answer your question more directly, it’s a combination of amplifier power, speaker sensitivity, source level, room size, music type (low frequencies will eat more power than high) and I’m sure there are other factors I don’t know about. A 200 watt amp is a 200 watt amp and will drive a speaker close to the same volume regardless of price, but a better amp may do it a little cleaner, with better low end or  better peak output, etc. etc.

My 48 watts/ch tube amp creates the same amount of volume as my 250watt/ch ss amp ( that doubles down to 400 watts/ch at 4 ohms). The reason has to do with the ability of the transformers and the amount of current delivery to my speakers. Not wattage. 

So what spec do I look at instead of wattage?

Depends on your speakers.

What are you playing?

The issue may be the speaker / amp matching and knowing your speakers would help.  Your speakers may be out of dynamic range or they may have a difficult impedance profile. 

Assuming you had easy to drive speakers, and they were not even a little stressed, then Wattage would help you understand how much more you needed.  Doubling of power = 3 dB SPL.  Doubling perceived volume = 10x the power, and 10 dB louder.

OP:

Lets simplify.  If you feel you are "almost there" with your current amp and you are looking for a reason to upgrade, go ahead.  However if you feel there's a big gap between how loud you can play and how loud you want to play the math isn't in favor of a 2x power difference being your solution.

It's also possible your amp has plenty of juice but it's your speakers which are compressing and reaching their thermal and/or mechanical limits.  They do have limits. 

So, if you feel you have a big gap between where you are and where you want to go, it's more likely to be solved by higher efficiency speakers.

Have fun shopping!

Erik

Hello dman777.  By now, you have waded through a lot of anwers to your question. They are all pretty good. Let's talk first about speaker sensitivity. A speaker rated at 84 db (we assume the ratings are honest) will play 6 db softer than a speaker rated at 90 db. It will take four times the power to drive the 84 db rated speaker to the same volume (loudness?) in the same room. A 94 db rated speaker would need only one tenth the power to play the same loudness as the 84 db rated speaker.

The advertisements don't tell you that, but it's true. Do you have some input device with meters on it to indicate the strength of the output signal. Watch the needles dance. A 10 db increase calls for ten times the power from an amp. A 20 db increase call for 100 (Yikes!) times the power from the amp. Amps that double their output power into four ohms verses what they put out at eight ohms have pretty hefty power supplies. A two ohm rating at four times the power output indicates a really strong power supply. Check the ratings of tube amps verses solid state amps. Also look at the distortion percentages at rated power. Tube amps are often rated with maximim power at 10% (harmonic) distortion. Solid state amps are often rated a so much power at 1% distortion. Tube amps can seldom double their output power into a 4 ohm load verses an 8 ohm load. All of this means that when the drum goes BOOM! an amp is called upon to put out a lot of juice in a hurry! Can the amp do it? You want an amp that never has to sweat. An amp rated at 100 watts that has to put our 150 on occasion (not even a 3db difference in apparent loudness) will sound less pleasant than the same input with the same speakers in the same room, with a 200 watt rated amp and not have a problem at all. The more efficient your speakers are, the happier your amp will be. I hope this helped. Enjoy the music!