What is Loud? How Much Power Do You Need?

Greetings Dynastar Fans:

I notice there is a lot of hub-bub with the discussion of loudness vs. power ratings on guitar amplifiers

both tube amplifiers and solid-state amplifiers.Let’s look at this SPL chart as Let’s look at this SPL chart as a starting point:

Hmmm.. Somewhere I recall my mother shouting in the orange zone. I should not have door bell ditched my home three times in a row. Okay…. so back to this.

One day we were putting on an Aileron amplifier clinic at a local music store, and as we were blaring the amp at high volume, it surprised me that one of the sales guys said “Wow that’s only 12 watts!?”

Believe it or not, low power does not mean low SPL (Sound Pressure level). Most consumer audio equipment like stereos are in the 8-25 watt range and are PLENTY LOUD!! You see it’s not just the amplifier power that counts. It’s also the efficiency of the speaker cabinet. Meaning how much SPL can a speaker generate for a given amount of power fed into it. YUP… PA System cabs range in the 92-105Db range.. That’s a pretty good spread…

So without going super boo-foo techie on you, note that the next time you hear something louder than it was, you probably had a 3Db increase in SPL’s. To achieve that, you need to double the power output dissipated into the speaker every time you want to hear you playing louder.

So check this out.. Let’s say I have an amp that has a power output rating of 10W. If I want to double the SPL for that power rating, I would have to now dissipate 20W… But wait.. what if want to get another 3Db of SPL? Ahh then it goes to 40W… you see it’s exponential (Oooh yuck math).. Another 3Db? 80W.. then 160W.. etc… now we’re past what most guitar amplifiers can output in terms of power…

Don’t get me wrong … 100W is loud if you are playing at a full 100Watts, but most of you are not,

unless all the volumes are turned up full blast, and your striking your strings as fast and hard as you can. Just not gonna happen in the real world. The power levels are all peaking as notes are played. This is why it is very interesting that even a measly baby 5W amplifier can sound pretty decent, and get you that power amp overdrive that many desire. Ahhh.. that’s a tone advantage.

Also important is how well the power supply section is designed in the amplifier. A weaker power supply will yield a sagging choked tone when you strike power chords, but a strong one will give you the loud drive you need on demand. Both playing “Feels” are desirable. We serviced a vintage Fender Champ amplifier the other day that was probably rated at 6W. What a great overdriven sound.

Now at our last amp clinic, we could easily get several attendees to hold their ears closed, with such low power… Not a surprise at all if you understand the relationship between power, SPL and cab efficiency. Don’t look at an amp, and simply say.. “oh that’s not enough power”.. Play it, and evaluate it. There are pluses and minuses to high powered vs. low powered amps. Cost, weight, early signal break up, etc… Remember a low powered amplifier can also be externally amplified via PA system. That can give you the advantage of getting power amp crunch/overdrive at high volumes for your audience.

Dynaman…