Power vs Speakers

[GuiTuber]

Which gives you a bigger boost in volume, double the power or double the speakers?

If doubling the power is only good for 3db, what would you get if you went from one 15" speaker to two, with the same power?

BTW: I did a search and couldn't find anything. But then, maybe I just didn't use the right phrase.

 

[Bass_Pounder]

Same +3db

 

[SunnBass]

More speaker surface area will give a more noticeable change than adding wattage.

 

[CL400Peavey]

Same +3db

this.

 

[Coolhandjjl]

Going from one driver to two drivers does more than add SPL. How you position the cab affects what the crowd hears. If they are vertically aligned, you increase dispersion above 500Hz or so. If they are positioned horizontally, you increase ground coupling, good for reggae.

 

[mbelue]

Also getting another driver up nearer your head will make it more intelligible to close. The mids/highs won't be blowing past your knees.

Doubling power will only give you +3db of loudness IF your speaker can handle it. Might just turn into a farty mess.

 

[drpepper]

Same +3db

Yes. This.

...but the math behind sound power/loudness requires that all other things be equal...as a practical reality, they rarely are.

In real-world scenarios, like someone looking to either add a cabinet to an existing rig or replace their head and keep using the same cabinet, all other things aren't going to be equal; impedance, output wattage, speaker power handling aren't going to be the same.

Also, the math for loudness increases corresponding to wattage increases assume the same system...going from 100 watts to 200 watts in system A results in +3db, but going from 100 watts in system A to 200 watts in system B may not result in a 3db increase between system A and system B.

 

[Jazz Ad]

Also adding a speaker typically brings down impedance, thus making the amp deliver more power.

 

[chris_b]

IMO more speakers is preferable.

Your amp will give out more power which will increase your volume, but IME more speakers gives you better tone. Which is definitely better.

 

[Rick James]

If you double power you get 3dB if your speaker has the excursion to handle the added power. If you add a second speaker the total cone displacement is doubled, that gets 6dB if your amp can handle the halved impedance.

 

[Bass_Pounder]

If you double power you get 3dB if your speaker has the excursion to handle the added power. If you add a second speaker the total cone displacement is doubled, that gets 6dB if your amp can handle the halved impedance.

Just to clarify............

Doubling speaker area gives +3db
Doubling wattage provides +3db

To get +6db, you need to be doubling speaker area AND doubling wattage at the same time.

 

[Jim Carr]

Q: What do I do to double the perceived loudness of a sound?

3 dB? 6 dB? hmmm.... neither.

The perceived loudness of the sound depends on several factors: the amplitude, the sound pressure level, the frequency, and the time behaviour of the sound. A typical question on the internet: "Is 3 dB or 6 dB double the loudness?" The answer is: "It is neither 3 dB, nor 6 dB − it is closer to 10 dB".

A Worthwhile summary is here: www . sengpielaudio.com/calculator-levelchange.htm

I broke the above link because it displays a lengthy quote. Just delete the blanks around the ".".

 

[tonemachine]

Yes. This.

...but the math behind sound power/loudness requires that all other things be equal...as a practical reality, they rarely are.

In real-world scenarios, like someone looking to either add a cabinet to an existing rig or replace their head and keep using the same cabinet, all other things aren't going to be equal; impedance, output wattage, speaker power handling aren't going to be the same.

Also, the math for loudness increases corresponding to wattage increases assume the same system...going from 100 watts to 200 watts in system A results in +3db, but going from 100 watts in system A to 200 watts in system B may not result in a 3db increase between system A and system B.

Nobody ever asks "is 3db" significant or insignificant. It seems to be implied that it is insignificant but isn't db some sort of exponential thing where "a little really is a lot."

Good explanations, by the way, to all who pointed out that adding speakers will more than likely allow the amp to pump out more wattage... laymen can then see that it usually doesn't take a whole bigger amp or many more speakers to get a whole lot more volume.

Simply stating db changes of 3 is over-simplifying things as far as practical/perceived loudness changes go for guys who dont understand basic loudness changes in the first place. I was there not long ago so I know that the clarity is appreciated moreso than a number frequently regurgitated but few actually understand!

 

[AstroSonic]

A 3 db difference is an 'obvious', but far from overwhelming change in volume. However, it can make a big difference in sound quality. If the target spl is held constant and a cab with 3 db higher sensitivity is used (or a second one is added) the amp can be turned down so that it is no longer heavily overdriven. Likewise, if the cab was being overdriven, adding a second cab cuts the power to the original in half (it divides between the 2 cabs), allowing it to sound better, last longer and reduce thermal compression - gets you a couple more db.

Doubling the volume requires a 10 db increase. If this is done with power (instead of adding a cab), a 10x increase in power is required.

Nobody ever asks "is 3db" significant or insignificant. It seems to be implied that it is insignificant but isn't db some sort of exponential thing where "a little really is a lot."

Good intuition! A small change is db equates to a small change in volume, but a large change in power.

 

[ashtray]

So if I have a 200 watt 4x10 combo, and add a second identical 200 watt 4x10 combo, this wouldn't give me twice the volume? (+3 for doubling wattage, +3 for doubling speaker area = 6db gain)

I guess that begs the question: just what is the definition of "twice as loud"?

 

[Jazz Ad]

dBs/sound levels are a relative logarithmic measurement, doubling it makes no sense.
Typically +10dB is said to double perceived volume but since perception is different to anyone, it really is senseless.

 

[drpepper]

So if I have a 200 watt 4x10 combo, and add a second identical 200 watt 4x10 combo, this wouldn't give me twice the volume? (+3 for doubling wattage, +3 for doubling speaker area = 6db gain)

I guess that begs the question: just what is the definition of "twice as loud"?

Interesting, especially in that it brings up a math element that's usually missing from these discussions…distribution of wattage between speakers…hmmm. Anyway, that aside, loudness is the perception of sound power/intensity, so "twice as loud" would be defined as what someone would say is twice as loud. It's been determined through study that sound power needs to increase by a factor of approximately 10 in order for a sound to be experienced as twice as loud.

I think that the best explanations for me move away from watts and speakers. Using the sound of one normal speaking voice as one unit of sound power can be a good one. Two identical people speaking at the same time (so twice the sound power and 3db louder) is not twice as loud as one person. It's easily discernible as being louder. It's as loud as…two people talking at the same time. To think of more precise doubling, think of copying and pasting a track in a DAW or NLE timeline.

I believe that would have to be the same thing with two identical amps and the increase in loudness would be defined as +3db.

 

[Jughead6]

I'm no expert, but I get a little bit miffed when people talk about "only a couple of decibels".

The acoustic engineers at my workplace talk about sound pressure levels and sound power levels. Decibels are used to measure the ratio of two sound pressure levels or two sound power levels. Basically you divide the base 10 logarithm of one SPL by the base 10 logarithm of the second SPL to get a ratio of how much louder the first SPL is. The result is not linear, so a ratio of 3 dB does not sound like a lot but means there is twice as much pressure/power in the sound waves.

How humans perceive this increase is pressure/power is a different story. Humans tend to be more sensitive to higher frequency sound, which is why we bassists need considerably more power than our guitar playing brethren just to be heard.

But 3dB is still a LOT. And workplace safety laws are now recognising that 8 hours exposure to 85 dB(A) can be literally deafening.

 

[Rick James]

Just to clarify............
Doubling speaker area gives +3db
Doubling wattage provides +3db
To get +6db, you need to be doubling speaker area AND doubling wattage at the same time.

The speaker area isn't what matters, the area times the excursion is. That's called displacement. If you double the speakers parallel wired without changing anything else the displacement doubles and that gets 6dB. The power doubling is automatic, because the amp will give the same voltage into any impedance, and the current doubles when the impedance is halved by the parallel wiring. You just have to make sure that the amp is rated to handle the halved impedance load. The only way you'd get only 3dB by doubling speakers is if you turned the volume down.

So if I have a 200 watt 4x10 combo, and add a second identical 200 watt 4x10 combo, this wouldn't give me twice the volume?

It would give you 6dB. It takes 10dB to get twice the volume.

 

[Coolhandjjl]

But it is difficult to compare and test this stuff. One brand of a 2x12 does not automatically imply it can output more SPL than another brands 1x12. Speakers are rated with a term called 'efficiency'. IOW, how much SPL will it produce with 1 watt measured 1 meter away with an SPL meter in an anechoic chamber. An efficiency rating may be something like 100dB. But those ratings are always suspect, because even if two cabs have identical efficiency ratings at 500Hz, they may be very different at 100Hz or 50Hz. So some cab manufacturers provide measurements at those lower levels, and some a complete graph of the entire frequency response with the SPL measurement. And some do not. And that's just at 1 watt. What happens at high wattage distortion-wise?