Epi. Vol. Jr 5watt amp

[Bruce / Mission Amps]

Where is it written that doubling the power to a speaker is a +3dB increase in SPL?
And even with that, how much louder do we hear something that has an increase of 3dB sensitivity per watt?
I can never find this stuff when having a conversation with anyone.

[Enzo]

Why use a 50 watt speaker for a 10 watt amp?

If you had a shelf to hang on your wall, and it weighed 10 pounds, would you look for a shelf bracket to hold it up with a 10 pound rating, or would you look for something stronger?

Personally I wouldn;t look for a speaker that was just barely able to handle the power of my amp.

[Enzo]

A quick look in my Sound Systems for Worship book put out by Yamaha has on page 28:

"When you double the power of a signal, you increase the level by 3dB. When you double the voltage, you increase the power four times, which (is) a 6dB increase."

3dB louder is 3dB louder. ALL ELSE BEING EQUAL the difference in loudness of a 3dB more efficient speaker is the same difference made by doubling the power to the original speaker. 3dB is not much.

SO many people have the idea that a 60 watt amp is twice as loud as a 30 watt amp. it isn't. And that amazing 5 watt amp that sounds louder than expected through a larger cab? 5 watts would be half as loud as 50 watts.

[olddawg]

Why use a 50 watt speaker for a 10 watt amp?

If you had a shelf to hang on your wall, and it weighed 10 pounds, would you look for a shelf bracket to hold it up with a 10 pound rating, or would you look for something stronger?

Personally I wouldn;t look for a speaker that was just barely able to handle the power of my amp.

That would be a great analogy if a speaker was a shelf bracket. The 4X10 cabinet that I use is rated at 150 watts. I run this little 5 watt amp head through it and it sounds great. It pushes more air, has better projection, and has much more low end response. I doubt if I could use the amp in a club situation with a live drummer without it. It would be too wimpy through a tiny, tiny speaker no matter how efficient or what the power rating was. If I had to load it as a combo I would put the biggest cone speaker that I could fit into it.

[olddawg]

A quick look in my Sound Systems for Worship book put out by Yamaha has on page 28:

"When you double the power of a signal, you increase the level by 3dB. When you double the voltage, you increase the power four times, which (is) a 6dB increase."

3dB louder is 3dB louder. ALL ELSE BEING EQUAL the difference in loudness of a 3dB more efficient speaker is the same difference made by doubling the power to the original speaker. 3dB is not much.

SO many people have the idea that a 60 watt amp is twice as loud as a 30 watt amp. it isn't. And that amazing 5 watt amp that sounds louder than expected through a larger cab? 5 watts would be half as loud as 50 watts.

That was exactly my point. A 100 watt amp in theory is only twice as loud as a 10 watt amp. I know the math. I have been an ET for 30 years. However, as a head a VJ sounds great through a 4X10 cab to me. Much better and much more usable than through a single small speaker. That said a dimed Twin Reverb or a dimed JCM 800 always seems much more than two times louder than any 10 watt amp to me also.

[Enzo]

dawg, I was responding to the original poster, who was all concerned he needed to find a 5 watt speaker for his 5 watt amp - or whatever. My shelf bracket analogy was in support - pun intended - of using a speaker that could handle larger amounts being a good idea.

Forgive me if I am wrong, olddawg, but you seem to be reacting to my post in defense mode. I was actually agreeing with your points and supporting them. We have no disagreement I know of. Though I admit I had no idea you were an Extra Terrestrial.

[olddawg]

I had no idea you were an Extra Terrestrial.

That's funny. We might as well be from another planet anymore. No worries. An unfortunate reality of the internet is that people sometimes sound more serious in their post than they want to appear. I am in no way offended and have great respect for your vast experience, knowledge, and willingness to spend your valuable time to help and advice. This wattage, speaker, apparent volume conundrum has always baffled me because my personal experience does not always jibe with the math. The caveat, I guess, is the all other things being equal clause.

Cheers

[Enzo]

That is a very large clause.

[Carlsoti]

I've got a slightly modded EVJ that I use with my MIM strat. I recently picked up a Orange PPC12 for less than half off the original price. The speaker is rated at 60w. I think the three together sound great.

[OC75]

Without doubt....
My hotrodded ValveJr. amp plugged into it's combo speaker, is a 2/3....Same amp plugged into the 2x12 is a a solid 8. I suppose we could try to split hairs, but the facts are, these small amps respond well to having more/larger speakers to push. It really opens up a nice tone.

[Rick Erickson]

I'll throw down my $.02 worth here:
An amplifier doesn't care how many speakers it drives or how many watts they can handle. All it sees is an impedance at it's output terminals. If the impedance is correct it delivers it's maximum amount of power to the load. If the impedance is incorrect than the amp delivers less power than it is capable of and other bad things can happen due to the mismatch of the power tubes impedance to the reflected output transformer primary impedance. If the speaker(s) can't handle the amount of power the amp delivers to them they will likely fail. A speaker that can handle 200W is not necessarily a louder speaker than one that can handle only 15W. Every speaker has it's own unique tone - just like different amps, guitars and pickups each sound unique. A speaker that is very efficient won't necessarily sound "better" than a less efficient one, just louder. The only way to find the "right" speaker for your combination of amp, guitar, cabinet and playing style is to try various ones until you hit on a good one - just like trying out pickups in your guitar...

RE