Wattage Importantness

[pickles]

The following is a quote from Invalid Link Removed
A University of New South Wales (Sydney, Australia) website.
******************
How big is a decibel?
...
One decibel is close to the Just Noticeable Difference (JND) for sound level.
... 10*log10(1.26) = 1, so to increase the sound level by 1 dB, the power must be increased by 26%, or the voltage by 12%.

What if the difference is less than a decibel? Sound levels are rarely given with decimal places. The reason is that sound levels that differ by less than 1 dB are hard to distinguish...
******************
I have seen other sources that quote 3dB as being just noticeable, so maybe I am splitting hairs, but it's difficult to imagine that the difference between a 500W amp and 1000W amp (with the same speaker system) is just barely noticeable.

What I meant is that 3db is the minimum output increase that will have a meaningful effect on your sound. IME, YMMV. Going out and buying an amp with a couple hundred extra watts (all things equal, same brand, etc) is not going to yield a satisfying volume increase. If you double the power and your cabs can handle it, you will hear the difference. Otherwise don't bother.

IME, if a 150 watt amp isn't cutting it, try 500 watts. If 500 isn't cutting it, its time to get serious or get your drummer to lay off. Ever since I got into the 1000 watt + club I've had a much better time getting the kinds of sounds I like (fat!) at volumes that feel good.

 

[Mark Reccord]

Great web site.

Yeah, the "it takes twice as much wattage to equal a mere 3 db change" thing is something oft-quoted, and is demonstrably true. What should be quoted along with it IMO and rarely is, is that the decibel scale is logarithmic. That means that while the difference between 3 and 6 db is barely discernable to the human ear, the difference between 100 and 103 watts is VERY noticeable. It's not a linear scale, and there's a huge difference between how much sound a 500 watt and a 1000 watt amp will put out (in decibels, anyway. Frequency response is, as has been pointed out, a diferent matter).

The audible difference between say 50 and 53dB SPL is exactly equal to the audible difference between 100dB and 103dB. That's why that scale is used. It is a logarithmic scale, but not in the way you're describing. Our ears have a logarithmic response to pressure so they respond in (what we perceive to be) a linear fashion to order of magnitude changes in pressure. The decibel scale is a way to compress the 7 or 8 orders of magnitude of actual sound pressures we can perceive into a scale of a couple of orders of magnitude. However, 3dB is 3dB no matter where on the scale your baseline is and is perceived as such. There is a 3dB difference between a 500W amp at full power and an (otherwise identical) 1000W one at full power. It's a noticeable difference but not anywhere near huge.

 

[WalterBush]

Okay, as I go running to read up more on psychoaccoustics, how does the "push" most of us like to feel in front of our amps measure with regards to percieved db level? I realize this is more a function of speaker cone area, not wattage, but it requires a lot of power to make speakers move enough air to be felt, and not just heard. Bass guitar is audible with smaller speakers and systems, but most bassists I know like to FEEL their bass when they walk a little ways from their rig, and that requires a significant amount of power. Since bass is not "felt" with the human ear, does this mean that the 2x power=3db of audible difference argument doesn't apply to the "earth-moving" qualities of a bass amp's power rating?

 

[Mark Reccord]

Okay, as I go running to read up more on psychoaccoustics, how does the "push" most of us like to feel in front of our amps measure with regards to percieved db level? I realize this is more a function of speaker cone area, not wattage, but it requires a lot of power to make speakers move enough air to be felt, and not just heard. Bass guitar is audible with smaller speakers and systems, but most bassists I know like to FEEL their bass when they walk a little ways from their rig, and that requires a significant amount of power. Since bass is not "felt" with the human ear, does this mean that the 2x power=3db of audible difference argument doesn't apply to the "earth-moving" qualities of a bass amp's power rating?

Nope, it applies alright but we do need more power at low frequencies because our ears are much less sensitive to them than they are to midrange frequencies (google Fletcher-Munson curves). The perception of feeling the bass is a function of the long wavelengths and the resonant frequencies of our bodies and that low frequencies also move a larger volume of air in the compression and rarefaction of the sound waves than high frequencies do. This leads to perceptible air movement.

 

[lowphatbass]

So if a 2 fold increase in wattage is just audible in terms of volume then why do my expensive cabs have a much higher power rating than my less expensive ones. Why don't they make them with 2/3's the power handling if its going to sound pretty much just as loud? It would take less expensive components, right? I'm NOT saying that this is why they're louder, but why make a speaker cab with such high power handling capability if it is not needed to achieve loudness?(I'm refering to EA VL208 and BE Q10XB-D) Is this so I can feel like I'm getting my money's worth?
I am going to "unbridge" and A B this theory, I'll verify proper ohm's matching and go for it if I can make a fair safe comparison.

 

[IvanMike]

The audible difference between say 50 and 53dB SPL is exactly equal to the audible difference between 100dB and 103dB. That's why that scale is used. It is a logarithmic scale, but not in the way you're describing. Our ears have a logarithmic response to pressure so they respond in (what we perceive to be) a linear fashion to order of magnitude changes in pressure. The decibel scale is a way to compress the 7 or 8 orders of magnitude of actual sound pressures we can perceive into a scale of a couple of orders of magnitude. However, 3dB is 3dB no matter where on the scale your baseline is and is perceived as such. There is a 3dB difference between a 500W amp at full power and an (otherwise identical) 1000W one at full power. It's a noticeable difference but not anywhere near huge.

+1

a 3 dB increase is a 3 dB increase, regardless of where you measure it. looking at the logarithmic graph for a difference in 50 and 53 dB will look exactly the same as the graph for a difference between 100 and 103 dB, or anywhere on the graph. no matter where you view it, or how large a portion you look at, it always appears the same.

same thing when it comes to a 500 watt amp and a 1000 watt amp. as long as they're from the same manufacturer (so the rating's the same) and put into the same speaker (so the response to the wattage is the same) the difference will be 3 dB, which ain't much.

Common sense will tell you otherwise, but common sense is based upon thinking in linear terms, not logarithmic ones. I remind my self of that as i pump 450 watts into my 15" bag end and just compete with a guuitar thru a 22 watt fender deluxe reverb amp.

 

[IvanMike]

So if a 2 fold increase in wattage is just audible in terms of volume then why do my expensive cabs have a much higher power rating than my less expensive ones. Why don't they make them with 2/3's the power handling if its going to sound pretty much just as loud? It would take less expensive components, right? I'm NOT saying that this is why they're louder, but why make a speaker cab with such high power handling capability if it is not needed to achieve loudness?(I'm refering to EA VL208 and BE Q10XB-D) Is this so I can feel like I'm getting my money's worth?
I am going to "unbridge" and A B this theory, I'll verify proper ohm's matching and go for it if I can make a fair safe comparison.

the advantage to the high wattage rating is more due to the cabinet's ability to handle large transient spikes when you're using a lot of headroom and a powerful amp. Headroom's just no darned good if you shred your speakers with it.

 

[WalterBush]

Nope, it applies alright but we do need more power at low frequencies because our ears are much less sensitive to them than they are to midrange frequencies (google Fletcher-Munson curves). The perception of feeling the bass is a function of the long wavelengths and the resonant frequencies of our bodies and that low frequencies also move a larger volume of air in the compression and rarefaction of the sound waves than high frequencies do. This leads to perceptible air movement.

Thanks for the google search hint--the actual mathematics of acoustic principles is something I'm admittedly weak on. Lemme make sure I've got this straight. Wattage IS important in a bass amp, because although the difference in 3db is audibly not much different (because the human ear doesn't hear the logarithmic db curve in a linear fashion) the human body will feel the difference in 3db as a logarithmic function, yes? Those 3db of difference between a 500 and 1000 watt amp make a MUCH larger difference when dealing with electric bass fundamentals, and how we feel them, rather than hear them, it would seem to me.
EDIT
Look, I'm not trying to argue with the fact that it takes 2x the power to equal a 3db change in volume, as it is silly to argue with hard mathematics. I'm sort of taking issue with the assertion that a jump from 500 to 1000 watts or 1000 to 2000 watts (I jump we made when putting a subwoofer in my band's PA setup) is not that significant when trying to push air and rumble the stage, and that difference of 3db midrange perceived by the ear is the same as the 3db difference your body percieves as 100hz (and lower) frequencies that make the human booty want to move . If I'm wrong about this, then I'd either like someone to explain where I'm reading charts wrong, or tell me how I can power a subwoofer louder than a guitarist for only 200 watts (twice the power of your average guitar head.)

 

[IvanMike]

The following is a quote from Invalid Link Removed
A University of New South Wales (Sydney, Australia) website.
******************
How big is a decibel?
...
One decibel is close to the Just Noticeable Difference (JND) for sound level.
... 10*log10(1.26) = 1, so to increase the sound level by 1 dB, the power must be increased by 26%, or the voltage by 12%.

What if the difference is less than a decibel? Sound levels are rarely given with decimal places. The reason is that sound levels that differ by less than 1 dB are hard to distinguish...
******************
I have seen other sources that quote 3dB as being just noticeable, so maybe I am splitting hairs, but it's difficult to imagine that the difference between a 500W amp and 1000W amp (with the same speaker system) is just barely noticeable.

very cool site. i think everyone should visit that and listen to the different sound clips of 3 dB difference, 1 dB difference, and .3 dB difference.

yes i could notice a teeny tiny difference in the 1 dB clips, but much more so in the 3 dB clips. even so, the difference in the 3 dB clips was still pretty small. and yes kids, no matter how loud or quiet the clips, the 3 dB difference always sounded the same.

 

[IvanMike]

Thanks for the google search hint--the actual mathematics of acoustic principles is something I'm admittedly weak on. Lemme make sure I've got this straight. Wattage IS important in a bass amp, because although the difference in 3db is audibly not much different (because the human ear doesn't hear the logarithmic db curve in a linear fashion) the human body will feel the difference in 3db as a logarithmic function, yes? Those 3db of difference between a 500 and 1000 watt amp make a MUCH larger difference when dealing with electric bass fundamentals, and how we feel them, rather than hear them, it would seem to me.

remember this, the 3 dB difference is a difference in sound pressure level, not hearing level. that sound pressure will apply to everything be it travelling thru a gaseous medium or solid. also the deal is that we do hear the 3 dB increases in a linear fashion. decibels represent points on a logarithmic scale in order for us to translate the logarithmic relationship of watts to SPL into a linear one that we can relate to. that's why we have things like audio taper pots, so we can affect something that occurs in a logarithmic fasion into an event that we can hear in a linear fasion.

 

[lowphatbass]

the advantage to the high wattage rating is more due to the cabinet's ability to handle large transient spikes when you're using a lot of headroom and a powerful amp. Headroom's just no darned good if you shred your speakers with it.

I guess my question is, "why use the powerfull amp?"
Yes, I use alot of power, live for headroom, and my middle name is "large transient spikes", but armed with "the formula" I should be able to do almost the same thing with much less wattage, and the speaker manufactures know this, right?

 

[Mudbass]

Look at it from an electro/mechanical point of view. A loudspeaker is at heart a simple linear motor and like any motor, the bigger and more robust the motor, the more power is required to drive it. Guitar players have the luxury of using light-weight motors and it doesn't take much juice to drive them, but bass drivers with their heavier construction, larger voice coils and increased linear throw are bigger motors and consume more power. And as large motors are apt to do, they also run hotter and lose a more power to heat. So if you got big motors under the hood, you gotta feed em and that means bigger amps.

 

[Joe Beets]

Which gets back to a point that is clear to most experienced bass players. A 350 watt combo amp is going to reach T.O.F long before a 2000 watt stack.

 

[pickles]

3db may be "just noticable" ... but if you were priviously "just quieter" than the drums and guitars, it makes all the difference in the world! Or if you were previously sounding good but occassionally clipping .... 3db or headroom will most likely clear that up and keep you from frying your speakers.

 

[IvanMike]

3db may be "just noticable" ... but if you were priviously "just quieter" than the drums and guitars, it makes all the difference in the world! Or if you were previously sounding good but occassionally clipping .... 3db or headroom will most likely clear that up and keep you from frying your speakers.

very very true. realisitcally, unless stewart and eden rate their watts differently (which they might) 3 dB of headroom is all i'm getting having switched my eden 400 amp (400 watts into 4 ohms) for a stewart (450 watts into 8 ohms per side) with the two 8 ohm cabs i'm using. but it makes a difference.

 

[billfitzmaurice]

3dB of headroom is almost worthless. Amps, and speakers for that matter, are usually rated by their long term constant output capability. If you're running your amp anywhere close to that figure then what keeps you from going into clipping on transients is the amps headroom, which is its short term peak output capability over and above its constant output capability. A high quality amp may have 10dB of headroom. Inexpensive amps tend to have only 3dB of headroom, which is marginal, unless you are running it at least 3dB below its long term rating to begin with.

 

[IvanMike]

i definetely agree that 3 dB of headroom is just about worthless, but adding 3 dB extra headroom to a system that already has 3 or 6 dB of headroom can make just enough difference to count. in the case of using my wt-400 i'm guessing i had about 3-6 dB of headroom most of the time. doubling the wattage gave me just enough breathing room to have a more acceptable level of headroom (6-9 dB?) ish

to be honest, it feels like the setup i'm using now has at least 10 dB of headroom, which is a definite impovement.

 

[d8g3jdh]

Perhaps your all forgetting that some people are old and have worser hearing, some people don't clean their ears enough, and some people just don't hear very well (like me)

Also, the angle of the cab would make a different, so would the acoustics of the room...there really are alot of variables when it comes to hearing