Two Amps / Twice As Loud?

Lee Baucum · Post by **Lee Baucum** » 13 Apr 2006 9:26 am

At one venue we play at, once a year, the building is so huge that I would take both my Evans FET-500 and my Nashville 400. We don't mic our instruments, so with the two amps I could really fill up the room. I would set the amps side-by-side and angle one a bit to the left and the other a bit to the right. I can understand that this is pushing a lot more air and dispersing the sound better, but is it really twice as loud?

Kind of like hanging two motors on the back of a boat. If a 100hp motor pushes the boat at a top speed of X knots, will two 100hp motors push it any faster?

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Lee, from South Texas
Down On The Rio Grande

Mullen U-12, Excel 8-string Frypan, Evans FET-500, Fender Steel King

Larry Strawn · Post by **Larry Strawn** » 13 Apr 2006 9:36 am

Lee,,
Can't say about the two amps,, but the boat motors??? NO!! lol..

Larry Bell · Post by **Larry Bell** » 13 Apr 2006 9:45 am

Probably not
LOUDER, but not twice as loud

I'm not sure that's what you really want anyway. Without sound reinforcement (micing), one amp is very directional. You blow them away on one side and the other side barely hears you. With two amps pointed as you describe, you will fill the room up better. In some ways, an extension speaker oriented as you describe might help, but not as much as two separate pre and power amps, plus speakers.

I bet you'd need three or even four 200W amps to really register twice as loud on a dB meter -- but that's just a guess. I'm sure there are electronics gurus who can give you the equations. It's kind of a moot point since twice as loud would probably mess up everyone's hearing -- ESPECIALLY YOURS.

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Larry Bell - email: larry@larrybell.org - gigs - Home Page
2003 Fessenden S/D-12 8x8, 1969 Emmons S/D-12 6x6, 1984 Sho-Bud S/D-12 7x6, 1971 Dobro, Standel and Peavey Amps

Post by **Dave Mudgett** » 13 Apr 2006 9:52 am

The answer is no - at any given spot, neither the actual nor perceived volume level will be anything like double. Volume goes up more like a logarithmic function of power than a linear function, giving diminishing returns for linear increases in power.

One may get significantly better distribution in a large room by doing what you suggest. The volume may also be somewhat louder in places where there is overlap. But there is also the potential problem of phase cancellation between the sound waves created by each source, which can work against this.

Greg Cutshaw · Post by **Greg Cutshaw** » 13 Apr 2006 9:54 am

Going from 200 to 400 watts, doubling the power, is only a 3 decibel change in the sound power level, barely perceptible! Going from 200 to 2000 watts, 10 times the power happens to be a 10 decibel increase and would sound twice as loud.

speaker power decibel calculator

It could be since you are spreading the sound in more directions that some people in the audience see a huge increase in the sound with two amps versus one. Also the amps' sounds can vary by frequency as the phase shifts in the sounds from the two amps are added. Best case they add and you get the benefit of both amps, worst case they could be totally out of phase and cancel yielding zero volume at some frequencies at some locations in the audience.

Greg

Mike Brown · Post by **Mike Brown** » 13 Apr 2006 11:21 am

It would take ten times the power to make it twice as loud. Two amplifiers would make it noticable.

Ernie Renn · Post by **Ernie Renn** » 13 Apr 2006 11:35 am

Lee;

Just don't point them both at yourself. If you do then you'll likely get some cancellation. You don't really notice it, but you'll be playing at a comfortable volume and really be playing a lot louder than normal. I've done this. For a while if we had a big stage I'd put one on each side of me. With a light stereo chorus it'd sounds really enormous, (like a pair of twin 15" headphones.) But, I also play guitar and stood up and walked away from the amps and it came on like gangbusters. It'd cancel out about a fourth of the sound.

Additionally, I played a show on PBS that was stereo. They put mics on both amps and I was on the tape in stereo. I played Buddy's version of Elton John's "Blue Eyes." The sound in the TV studio was great, but when the show came on, I was barely there. The two amp thing had cancelled me out.

I'm probably repeating myself here. Just thought you should know what can happen.

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My best,
Ernie

www.BuddyEmmons.com[This message was edited by Ernie Renn on 13 April 2006 at 12:48 PM.]

Lee Baucum · Post by **Lee Baucum** » 13 Apr 2006 12:50 pm

When I played through two amps, I left all my settings as usual. The overall volume never sounded any louder than when I was playing through just the one amp. It just sounded "bigger". I wasn't using any stereo f/x units. I just wanted to try to reach everyone in the hall.

Now, about that boat and two motors thing. Maybe I need to ask that question on the Small Boat Forum.

Gary Glisson · Post by **Gary Glisson** » 13 Apr 2006 1:30 pm

I don't think it really makes it any louder (most of the time the band is usually telling the steel to turn down anyway) but the secret to 2 amps is using your effects to make some beautiful stereo chorus and delay. keeping the people wondering how your get such a great sound , why your steel sounds so much better than the last band they heard with a steel
atleast thats my goal!

CarterD-10 8+5 two Evans FET 500 LV, Hilton digital sustane

Donny Hinson · Post by **Donny Hinson** » 13 Apr 2006 1:44 pm

My experience is that it probably takes four amps to sound twice as loud. I've often heard the (engineer's) debate about it taking 10 times the power in an amp to really be twice as loud, but I don't find that to be the case. From my own point of view, a 200 watt amp sounds easily twice as loud as a 50 watter.[This message was edited by Donny Hinson on 13 April 2006 at 02:45 PM.]

Lee Baucum · Post by **Lee Baucum** » 13 Apr 2006 1:57 pm

Donny said:

From my own point of view, a 200 watt amp sounds easily twice as loud as a 50 watter.

If that is true, why is it that when one 80 watt amp isn't enough for a large venue, two 80 watt amps is? I've read numerous posts on this Forum about using 2 Nashville 112's when playing in really large venues. What is being gained, volume or dispersion of sound?

Greg Cutshaw · Post by **Greg Cutshaw** » 13 Apr 2006 2:06 pm

Donny, lots of people would agree with you! The ear does not hear all frequencies the same as it's sensitivity below 100 Hertz drops rapidly and high frequency sounds are greatly compressed.

The 10db, 10 times the power equals twice the volume statement refers to Sound Pressure Level(SPL) in newtons/square meter and refers to the actual force imposed by the sound. Thus a 10 db increase in power doubles the SPL.

Well before that point it is likely that a person listening to the racket would think, "wow, that's twice as loud". The statement is subjective, the SPL reading is not.

Greg

[This message was edited by Greg Cutshaw on 13 April 2006 at 03:07 PM.]

Tony Prior · Post by **Tony Prior** » 13 Apr 2006 2:16 pm

it's more of a PRESENCE thing than anything else..

When I use two amps, N400 and Sess 400.. I use one basically for stage presence and the other as more of a monitor aimed slightly sideways across the bandstand...

Is it loud ? Sure , but thats not the intent. One amp directed with no obstructions straight out is the intent.

One of the biggest amp issues I see with Steel players is that they place there amps directly behind them so the volume appears very loud..but the sound has to pass thru the body of the Steel player and basically the initial surge of volume stops at our backs.

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TPrior
TPrior Steel Guitar Homesite


[This message was edited by Tony Prior on 14 April 2006 at 01:22 AM.]

David Doggett · Post by **David Doggett** » 13 Apr 2006 2:41 pm

I think I agree with Donny and Greg. Using two amps pointed in the same direction (assuming they are in phase) is definitely louder, but not twice as loud. Twice as loud would be like going from 5 to 10 on your volume knob (if it is linear), or maybe going from about 3 to 10 on a nonlinear volume knob like Fenders have. With the addition of a second amp, it seems like about 30% louder, like your volume knob can go past 10 to about 13 or 14. Twice as loud would be like your volume knob can go from 10 to 20. I'm thinking that would take about 4 amps.

It's all very subjective. Not only does it depend on the frequency, but also how close you are to the amp. For someone in the front row, if your amp is on 10 and very loud, even a few more decibels will sound a lot louder and get painful, especially in the mids and low highs. For someone in the back of the room where it is not very loud, a few more decibels wont sound much louder. I think several of us are saying about the same thing. If I remember my Freshman physics correctly, the decibel scale was set up so that 1 decibel is the smallest perceptible change in sound. I think it works out so that what seems twice as loud (whatever that means) is about 10 decibels. (Disclaimer: as usual, it only sounds like I know what I'm talking about, this is really just a bunch of guestimating off the top of my head - or from the seat of my pants - maybe not much difference

)[This message was edited by David Doggett on 13 April 2006 at 03:43 PM.]