Two identical amps twice as loud as one?

[postjob62]

I hope some of you more tech savvy folks here can help me with this.

Logically, it seems to me that if you ran two identical amps (let's say Deluxe Reverbs) at the same time from one guitar, the resulting SPL at the middle of the room would be twice as much as just one of the amps by itself. If this is true, since twice the volume is available, wouldn't there also be twice as much perceived headroom? I know you wouldn't be changing the breakup point of the amp, but just before that point wouldn't you have twice as much clean volume as only one?

I understand that doubling the power in an amp yeilds only a 3 db volume increase, which is "just barely noticeable". But here we're not just doubling the power; we're putting two separate combo amps in the same room. I just can't make it compute that it wouldn't be twice as loud.

I'd sure appreciate someone knowledgeable commenting on this.

[maestrovert]

it wouldn't be twice as loud, but would be moving twice the air....

perceived doubling of the db/spl requires exponential acoustic power increases, whereas adding an amp to your setup is just adding an amp...
kinda like the mathematical difference between say, 5 cubed(=125) vs five plus five plus five(=15)....

hope it helps....

[postjob62]

Originally Posted by maestrovert

it wouldn't be twice as loud, but would be moving twice the air....

I'm not being arguementative, just ignorant. Help me understand why that would be twice as loud.

[Dacious]

If you were in a small box and fired up the second amp, it might be twice as loud. But in reality going from 22 watts to 44 watts is only going to increase perceived volume by a small amount. You would spread that sound out over a larger area before the soundwaves attenutat because of pushing their way past the air mollecules, but at any one point within that area it wouldn't sound much louder. A little, not much.

This is because your ears work on a logarithmic scale, not a linear. So doubling power only leads to a small increase at the ear. To double the 'perceived' volume you would need six amps, not two.

Because of a doubling of speaker area you will hear more, in fact just doubling speaker area on one amp would likely give you a similar perceived increase in sound to two whole amps.

There would be more headroom with the second amp, beacause there would be more of everything. 3db doesn't sound like much, but it is noticable.

[11 Gauge]

The best way that I know of to observe this is to go to any restaurant or bar before it gets busy.

Take a sound meter with you, just so you can have some numbers to back up your perceptions.

Say there's one loud drunk guy at the bar. Now add his drunk buddy - and they're both yakking at the same time. Annoying? Yes. Twice as loud? No.

But as the night moves on, and more people roll in, it will get steadily louder, even if many of the people aren't screaming at each other. Some places get loud enough to completely drown out the music or game on the plasma screen...

...At that point, check your meter. I'd be willing to bet that it'll be over 92 dB - which is friggin loud.

All those bodies, moving all that air, and the SPL goes up in a way that even 5 people shouting couldn't match.

[aznrambo481]

Your ears are logrithmic... that's why they have "audio taper" pots. "linear taper" doesn't sound linear because you your perception. Therefore, double the power wouldn't be double the perceived loudness. You need more amps (GAS fuel for sure )!!!!

[11 Gauge]

Originally Posted by Dacious

If you were in a small box and fired up the second amp, it might be twice as loud.

I think that this is what throws a lot of people, especially guitarists.

In our case, the "box" is a pair of headphones, and we're listening to our favorite tunes, with a guitar somewhat panned to the left and another to the right...

...With the sound emitting straight into your ears, you get the perception of much more volume.

I've also seen a lot of guitarists over the years who stand right in the line of fire of their 2X12, 4X12, 8X12 setups, to get the full power and glory. I've always preferred to stand off-axis, so I can turn it up a bit more and not go deaf, AND take advantage of any good room acoustics that might be present (but are usually rare).

Even loud sound disperses very quickly - air is a poor medium for sustaining it. Whales have got us beat when it comes to efficiently making loud music.

[Jimo]

I remember reading (I think) where The Greatful Dead hooked up about 50 champs at the same time and it was a huge sound. I've lost a few brain cells since then...anyone remember this article?------------ JIMO

[fauxsuper]

When I had a Fender Princeton Reverb years ago, I had a friend with another one. We A/B tested the two amps with another buddies Vibrolux Reverb. The two amps together were almost exactly as loud as The VR before they started to distort. Interestingly, the perceived loudness was greater the closer the two amps were to each other. I think the speakers were acoustically coupling to produce a little more bass when they got closer together.

The best description of the volume difference between one and two amps is probably "noticeably louder". But that's about it. If one DR is just barely drowned out by your drummer, two of them probably won't be. If, on the other hand, he just obliterates you, you probably need a twin. (Although that wouldn't be twice as loud as two DR's)

[postjob62]

I appreciate all the replies, guys. I've asked this same thing other places and gotten similar answers. I guess I shouldn't let my inability to understand the answers get in the way of my believing them to be true. I can grasp why doubling the power of one amp only yields an appx. 3db sound increase; I can also grasp why using two 1x12 cabs with an amp is not louder than the same amp with one 1x12 cab (just more dispersed). It just seems that adding a second complete combo is entirely different than just doubling the power of a single combo, but you folks tell me no. So much for my logical thinking.

It might help to explain my reason for asking. Imagine having a particular combo amp that you love everything about, except you wish it had a little more headroom. My theory was, why not just bring two, and voila!-you've doubled your sound output at the saturation level you like, effectively doubling your clean headroom.

Except, of course, it appears my original premise is flawed.

[popthree]

Originally Posted by postjob62

Except, of course, it appears my original premise is flawed.

maybe not... it might do exactly what you really want it to do...make the sound you like, only louder... apparently not 'twice' as loud, but i'd guess, definately noticeably louder.

[Slow Reflexes]

Originally Posted by postjob62

...I can also grasp why using two 1x12 cabs with an amp is not louder than the same amp with one 1x12 cab (just more dispersed). It just seems that adding a second complete combo is entirely different than just doubling the power of a single combo, but you folks tell me no...

50W through 1 speaker isn't gonna be any louder with two of the same speakers. You already know that.

100W is only 3db louder than 50W through the same speaker setup. You already know that.

Essentially, going with the two 50W combos is exactly the same thing as doing both of the other changes - you have 100W going through 2 speakers instead of 50W through 1 speaker. Same result however you want to arrange the tubes and transducers.

[postjob62]

Originally Posted by Slow Reflexes

50W through 1 speaker isn't gonna be any louder with two of the same speakers. You already know that.

100W is only 3db louder than 50W through the same speaker setup. You already know that.

Essentially, going with the two 50W combos is exactly the same thing as doing both of the other changes - you have 100W going through 2 speakers instead of 50W through 1 speaker. Same result however you want to arrange the tubes and transducers.

Bingo! I think your name might suit me better than you! That I can grasp.

Guess now I need to figure if the difference that it does make would be enough to be worth pursuing.

Thanks Slow Reflexes.

[Dacious]

Doubling speakers will provide more output - not quite double but pushing more area will project more.

Another way is: if you had a stock worn original speaker, fit a more efficient new speaker. A 33 watt Vox AC30 with two Celestion Blues is as loud or louder than a 100 watt Twin Reverb with Emis - the Blues are 105 db SPl, the Emis maybe 95. You get 10db with the Blues, = 3 times the power.

Running a pair of DRs with Cel Blues would be loud - probably louder than a Pro or Vibrolux Reverb with stock ceramics.

This is why very high efficiency speakers are so expensive. Even some Emi 12" alnico low-wattage, moderate price speakers are very efficient, up around 98-100db. They'd kill old Utahs or Oxfords for output. Same with EVs or JBLs - they increase headroom too, because they don't break up with low wattage through them.

[johnhe]

Mathematically, in theory, adding another identical noise source increases the sound power level by 3dB. Runnign 3 identcal noise sources increses the level by 5dB and running 4 increases it by 7. These are approximate figures, and an acoustic engineer would need to perform more precise calculations based on the actual noise spectrums.

However: in reality, I run two Blues Jnrs at identical settings. To be honest, running both amps together doesn't increase the sound that much. However, it makes it much easier for me to hear myself, since I have more spread of sound. There is certainly a noticeable increase in volume to my ears in using two amps, but it's limited.

Now, coincidentally, I also happen to have a 30W Classic 30. That amp on it's own through 1 x 12" speaker is sooooo much louder than both Blues Jnr's running together.

I prefer the 2 x Blues Jnrs - I'm not commenting on Blues Jnr's vs the C30. I'm just saying that two amps are louder, but not that much louder than one.

For example, if one 15W amp just was not cutting it volume wise for you in your bands onstage setup, I would not personally recommend adding a second 15W amp. Assuming that you'd been through your stage set up (i.e. try pointing the amp at your head - much cheaper than buying a new amp!) then a larger amp will make much more difference to your volume.

[1293]

Using a mono program, pan the balance knob on your stereo from one side to the middle. There's your difference.

[e-merlin]

I've had this question for a long time as well. I suppose it could be settled with a dB meter.

Seems to me that two whole identical combos would be more than 3dB louder than one. You have twice the power (3dB) an extra identical speaker (3dB) and accoustic coupling between the two speakers (3dB). I'm sure I'm forgetting something in this equation, but that is a pretty good increase in volume if I'm right.

[popthree]

seems like 2 people yelling would be twice as loud as one person yelling. i know 2 kids are more than twice as loud as 1....

[postjob62]

Originally Posted by popthree

seems like 2 people yelling would be twice as loud as one person yelling. i know 2 kids are more than twice as loud as 1....

I guess this has been my problem in understanding. The facts seem to defy everyday logic...

[tommyc]

I use two Epiphone Valve Juniors together and two are louder than just one , maybe not twice as loud but it is louder , maybe we percive the extra fullness produced by two amps as loudness .

[maestrovert]

Originally Posted by postjob62

I guess this has been my problem in understanding. The facts seem to defy everyday logic...

let's say you have a 50 watt amp turned up a bit and you're getting a measured 90db....
if you then add an identical amp, at the same settings and pushing the same 90db, the resulting
volume increase would not equal 180db....

Some relevant info <-- scroll down to "loudness"

more relevant info

[davidge1]

Im wondering if these explanations are not taking into account the fact that amps are somewhat directional. In a club, the percieved volume of your amp by people in the crowd has a lot to do with where they're standing...if your amp is on one side of the stage and someone is standing on the other side of the stage, they obviously wouldn't hear it as well. I would think that having an amp on each side of the stage could make a much bigger difference in how well people can hear you...even if technically speaking, it isnt much louder.

[postjob62]

Originally Posted by maestrovert

let's say you have a 50 watt amp turned up a bit and you're getting a measured 90db....
if you then add an identical amp, at the same settings and pushing the same 90db, the resulting
volume increase would not equal 180db....

Some relevant info <-- scroll down to "loudness"

more relevant info

Maestrovert, thanks for those links. Quoting the first link under "loudness" as you suggested, I find this:

"The judgment of relative sounds is more or less logarithmic, such that a tenfold increase in sound power is described as "twice as loud". The just noticeable difference in loudness varies from 3 dB at the threshold of hearing to an impressive 0.5 dB for loud sounds."

Again, not being arguementative but just trying to learn, would you qualify a Fender Deluxe Reverb at max clean a "loud sound" in the spirit of the above quote? If so, would the ear's ability to hear a noticeable difference then be in the 0.5 db range instead of the often-quoted 3 db (which according to the above only applies to sound at the lower threshold of audibility)?

If true, would that explain why the perceived difference in two amps vs. one amp seems to many to be greater than "just noticeable" even if not doubled?