Are two amps louder than one?

[jerryjg]

 WithbBoth the same exact amps/speakers, and  both at the same volume level , useing two together, will it be twice as loud? I know there will be twice as much sound pressure level , right?  Does SPL equal volume? Thanks

[G._Hoffman]

Twice as loud? No.  I can never remember if it takes 6 or 12 times the energy to create double the volume, but I think it's six.  (It's been a long time since that college acoustics class.)

Yes, SPL is sound pressure level, which equates with volume, but two amps will not double the dB SPL.  The biggest change, though, is from having two speakers, and you'll get pretty much the same results by doubling the number of speakers.

But it will be louder, and noticeably louder.


Gabriel

[Geezer]

I use a stereo setup with 2x ~18w amps into a 2x12 stereo closed back cab, switching with an A/B/Y box.

Either amp on by itself gives "normal" volume, and both amps on at the same time gives a significantly louder output, but not "twice" the volume (as Gabe said).

Also, either amp run by itself into both speakers (18w into 2x12 speakers) is not as loud as both amps run into each separate speaker (18w into 1x12 + 18w into 1x12).

It really is quite comparable to a 36w amp.

[jjasilli]

Yes.  See www.guitarnuts.com   

The human ear hears vol in decibels which is a logarythmic formula.  For the human ear to perceive a sound as 2X as loud the sound needs to have 10X the energy.  Two amps = only 2X the energy, a far cry from 10X.  Doubling the output power (2 amps) yields a 6 dB increase in vol.  It is noticeable, but not overwhelming, as the prior posts say.

In actually you probably don't want 2X the volume.  To have the 2X the vol of an 18 watt amp, you need 180 watts!!! 

More important is the SPL of the speaker.  A 20 watt amp with a highly efficient speaker, say 101 dB, will be as loud as a 100 amp with an inefficient speaker in the low 90's dB!!!

[PRR]

> Are two amps louder than one?

Usually.
 
> will it be twice as loud?

Usually not.

> there will be twice as much sound pressure level, right?

No.

In the over-simplified case, twice the acoustic Power, which of course is 1.414 times the acoustic Pressure.

In a special case (small drivers closely coupled), two drivers may approach four times the acoustic Power, twice the acoustic Pressure.

> Does SPL equal volume?

At "normal" sound levels, it sorta does.

On an amplified-guitar forum, we often don't want "normal", we want LOUD. As SPL goes above ~~85dB SPL, your ear-muscle tenses-up, de-levers the little bones to the ear-drum. In this range, "twice as loud" (nominally twice pressure or 6dB) needs 8dB, 10dB, or more rise of SPL.

[Dynaflow]

 Perhaps a touch louder, but man stereo chorus and ping pong delays and vibe's sound really cool through two in stereo. Assuming you haul two, I typically did when we gigged except one bar which was two miles from my house. Amp goes down, improvise guys, I'll be right back, saved me and my other guitar player a few times. Backup amps are always a good thing, if your using two you already have it there, if both go bad, well then your in trouble probably anyway. Few bass players I have played with carried any sort of backup (better ones did even if its just a ampeg combo). But hey its a bass player..  ;D

Regards,

Dyna

[birt]

as others said it will be louder. i can tell from experience that if you use enough small power amplifiers it will get VERY loud (i participated in symphony 13 by Glenn Branca, we had more than 70 small combo amplifiers on stage. that was the first time i still had a headache while wearing my -25dB molded earplugs...)

[Frankenamp]

(... that was the first time i still had a headache while wearing my -25dB molded earplugs...)

Ummm, were they all in tune?

 ;)

[G._Hoffman]

as others said it will be louder. i can tell from experience that if you use enough small power amplifiers it will get VERY loud (i participated in symphony 13 by Glenn Branca, we had more than 70 small combo amplifiers on stage. that was the first time i still had a headache while wearing my -25dB molded earplugs...)

His wife, Reg, was one of my best friends when I was at Berklee!  Their getting married always struck me as really strange, in a kind of avant garde Edie Brickell/Paul Simon kind of way.  But don't tell her I said that - I'd like to keep my head it current shape.  She used to come over and subject me to hearings of his various symphonies, which was fine, but she did seem to want to play them at awfully high volumes.

Ummm, were they all in tune?

 ;)

Perfectly in tune, I'm sure.  There were just a few extra notes in the octave! 


Gabriel