# (Amp1 X Watt) + (Amp2 X Watt) = ? watt

Discussion in 'Amps and Cabs [BG]' started by NoiseNinja, Jan 8, 2017.

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1. ### NoiseNinjaExperimental-psychedelic-ambient-noise-drone

Feb 23, 2011
Denmark
It probably have been asked before, but couldn't come up with any useful search terms that lead me to an answer, so here we go:

What would the result be?

Or specified a bit more:

If we are assuming you run your bass out two amps and cabinets at the same time, both amps does not only have equal watt technically but are also playing equally loud

How many watt would you effectively gain by this, contrary to just one of the amps?

Let's say they both are effectively pushing 100 watt through similar cabinets, just to come with an example.

I know this probably would make more sense to measure in decibel, but as I am not well versed in exactly how decibel works, how much 1 decibel actually is, and if perceived sound level works exponential or whatever, a number in watt would personally give me a better idea of what kind of output I should expect.

Last edited: Jan 8, 2017
2. ### Jazz AdMi la ré sol

Theorically, doubling the power gives you a boost of +3dB, assuming the speaker can handle the extra power and has a somewhat linear response.
Practically, you will get a drastic loss of volume when both amps go south. One does not plug 2 amps into the same cab. It's an electronic sin.

3. ### NoiseNinjaExperimental-psychedelic-ambient-noise-drone

Feb 23, 2011
Denmark
I did say similar cabinets, not the same cabinet.

Either way I found the answer.

And I am a bit embarrassed to admit I found the answer in an old thread started by myself with almost the exact same headline.

What do you know, I must be getting senile.

Anyway the correct answer is that you do actually double up the watt doing so, so in my example it would give a power equal to 200 watt, which again in the concrete example I gave give an increased volume perceived as +6 decibel compared to only running one amp at 100 watt.

Well, at least according to someone who seemed knowledgeable in the previous thread, for all I know he might have made it up

4. ### Rick JamesInactive

Feb 24, 2007
New Jersey
He was right. This brings up the recurring theme that watts don't matter, because we don't hear watts, we hear decibels. How many decibels we hear is based on the displacement of the speakers, and how much air the cones displace is based on the voltage applied to them. In this case two amps providing the same voltage to two speakers results in twice the displacement as one speaker, which gives a 6dB increase in output. You would get the same 6dB if you doubled the displacement of one speaker, which takes a doubling of the voltage applied. That's a quadrupling of watts, as opposed to only doubling watts with two speakers, showing again why you can't use watts as an indicator of loudness.

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5. ### Nev375

Nov 2, 2010
Missouri
100 watts + 100 watts = 200 watts. That might mean something to the electric company's billing department, but it means nothing in terms of volume.

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6. ### NoiseNinjaExperimental-psychedelic-ambient-noise-drone

Feb 23, 2011
Denmark
So 200 watts coming from two 100 watt amps with similar cabinets and turned up equally, would still be quieter than a similar 200 watt amp pushing a similar cabinet?

7. ### ZooberwerxGold Supporting Member

Dec 21, 2002
Virginia Beach, VA
Two cabs will move more air than just one.

Riis

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8. ### NoiseNinjaExperimental-psychedelic-ambient-noise-drone

Feb 23, 2011
Denmark
I might as well reveal the reason why I ask.

I am pondering on copying my usual approach when recording "clean" bass through my sound interface running one tack clean and one track with a slight touch of chorus, reverb and a subtle low grit on as well.

I have a setup at the moment where I run the Line Out of my main amp, a 130W Trace Elliot through the Line Out, post EQ, into a 345W active 12" PA speaker with disabled horn, just to be able to get more of the same in case 130W isn't enough.

But what I am think of doing instead is running my Trace Elliot clean and then conect the PA speaker I got to the Tuner Out, so I just get the straight signal from my bass and signal chain before the Trace into the PA speaker, and then run a slight bit of chorus, maybe a tad of room reverb too, and then Behringer V-Tone Bass BDI21 with a bit of low grit on in between the Tuner Out and the PA speaker.

9. ### beans-on-toastSupporting Member

Aug 7, 2008
Wattage sums. But there are potential complications.

If the amps are the same, they will be in phase. If they are not the same, there MAY be a phase issue. If this is the case, it can be corrected by wiring one cabinet out of phase relative to the other. This is as simple as switching two wires in the cab. You want all the speakers moving outward on the leading edge of a positive going input wave.

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10. ### delta7fred

Jul 3, 2007
England
What beans says.

If when you run both rigs the bottom end seems less than one on it's own try reversing the phase (swap the connections on one of the speaker leads) of one cab, doesn't matter which one.

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11. ### agedhorseSupporting MemberCommercial User

Feb 12, 2006
Davis, CA (USA)
Development Engineer-Mesa, Product Support-Genz Benz
Note that the 3dB contribution to SPL increase due to the acoustic coupling (increased displacement) from doubling the number of speakers only applies to very closely spaced speakers and at low frequencies only. As the spacing increases, the contribution decreases because of destructive cancellation.

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12. ### BassmanPaulInactive

Them destructive cancellations getcha every time! LOL

Edit: Getcha is like gotcha only different!

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13. ### Downunderwonder

Aug 26, 2009
New Zealand
Your chorus will usually cause a phase mismatch in a clean blend as the returned chorus signal is reversed phase.

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14. ### agedhorseSupporting MemberCommercial User

Feb 12, 2006
Davis, CA (USA)
Development Engineer-Mesa, Product Support-Genz Benz
Chorus doesn't have to be inverted polarity, but there will be a modulated phase element because of how chorus works.

15. ### Downunderwonder

Aug 26, 2009
New Zealand
I didn't word that very well. Afaik most chorus pedals output a signal which is inverted from their input.

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16. ### 5StringBlues

Feb 26, 2009
Here we are...
What?

17. ### Downunderwonder

Aug 26, 2009
New Zealand
Which what?

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18. ### SactoBassA retired civil engineer who likes all-tube amps!Supporting Member

Jul 8, 2009
Lake Havasu City, AZ
Huh?

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19. ### ZooberwerxGold Supporting Member

Dec 21, 2002
Virginia Beach, VA

Riis

20. ### 5StringBlues

Feb 26, 2009
Here we are...

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