How do you get to +6db? You have one discrete thing producing an amount of sound, and pairing it with an identical thing producing the same amount of sound is precisely doubling the sound...
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Power vs Speakers
- Thread starter GuiTuber
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How do you get to +6db? You have one discrete thing producing an amount of sound, and pairing it with an identical thing producing the same amount of sound is precisely doubling the sound...
From Jim's link:
Definitions:
*Sound level or noise level is a physical quantity measured with measuring instruments.
*Loudness is a psycho-physical sensation perceived by the human auditory perception or the human ear/brain mechanism. That is not the same.
*We are told by psycho-acousticians that a level 10 dB greater usually means "double the loudness" or "twice as loud".
Doubling the sound is a vague term. True, +6dB is the SPL doubled, but we donlt hear it that way. Try it someday. Get two identical rigs. Run the first one, and get out in front and listen. Have your guy turn on the second one. The bass guitar will sound louder, but not a whole hell of a lot louder, certainly not twice as loud. (And I'm ignoring acoustical interference of sound waves caused side by side cabs and other issues that make comparisons extremely challenging.)
Do you men twice as loud? It is generally agreed upon that human perception of twice as loud means +10dB of SPL, but again, there are caveats as mentioned earlier.
And how do you get 10dB more SPL? Lots of ways to do that, but merely doubling your watts and doubling your drivers does not.
Twice as loud, twice the volume, double the sound, etc., are all terms that we should really stay away from. They are too vague and subject to misinterpretation and confusion. All that matters and all that is measurable is SPL. It is the industry standard.
And with proper software, you can measure SPL across the frequency spectrum. I have a $40 calibration mic and freeware for my laptop to do that. Even smart phone apps are showing promise.
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My personal experience, (flushing thousands of dollars down the gas drain especially for the last 10 years) is that adding more speakers in the correct manner (appropriately matched in design, impedance and arrayed) initially is far more beneficial than adding more power to most setups.
I confess that I have fallen victim to over complicating things. I believe the OP really just wants to know how much of an amp he needs for what he does, and if one has more than one driver, how much louder is it.
Unfortunately, GC is a horrible place to try out bass gear. I suggest seeing if you can borrow or rent some gear before you make a purchase. Talk to dudes at live shows at bars too. Bassists love to be able to talk to anyone during their breaks about their gear.
Unfortunately, GC is a horrible place to try out bass gear. I suggest seeing if you can borrow or rent some gear before you make a purchase. Talk to dudes at live shows at bars too. Bassists love to be able to talk to anyone during their breaks about their gear.
As a general rule of thumb, I stop counting power increase when I reach half the rated power rating of the speaker system, figuring mechanical limits or power compression or something is going to "eat" that last bit. All speakers, including these long excursion "super woofers" will get thermal compression over time, even if their mechanical limits are out there. So, if you're already up to half power and need louder, add more speakers. If you're not using that much power, upping the volume could get you where you need to go.
Then there's the deal where most amps don't fully double power by halving impedance. Increase but not double.
Then there's the deal where more speakers, bigger baffle just sounds bigger/fuller, even though the overall loudness might not measure any more spl than using less speakers that can take more power.
Then, if you're not looking for totally clean tone all the time, some speakers sound more "musical" than others when they get pushed out of their clean territory and start to distort. In that case, one might benefit from using fewer and pushing them harder.
Lots of variables in there.
Then there's the deal where most amps don't fully double power by halving impedance. Increase but not double.
Then there's the deal where more speakers, bigger baffle just sounds bigger/fuller, even though the overall loudness might not measure any more spl than using less speakers that can take more power.
Then, if you're not looking for totally clean tone all the time, some speakers sound more "musical" than others when they get pushed out of their clean territory and start to distort. In that case, one might benefit from using fewer and pushing them harder.
Lots of variables in there.
From my understanding, I would disagree that "all that matters" is sound pressure level.
We take in sound with our ears and process with our brains. We make ordinal arrangement of the perception of the power or intensity of sound, and that is called its loudness. I'd argue that how loud amps are and relative differences in their loudness matter a whole lot in many discussions here. Having posters be able to gain and understanding of the relationship between relevant aspects of sound power (amp wattage, number of speakers, etc.) and loudness is of interest and benefit.
Not being vague, I was talking about doubling "a sound" (i.e., a specific sound). That sound is "the sound coming from a given amp that is powered on and is amplifying some signal." That is a sound with some loudness that need not be specified. For the purposes of the discussion that was ongoing, it doesn't really need any further definition.
It was questioned whether combining two of these sounds would be twice as loud as the one.
Given loudness, as expressed in decibels, my understanding is that doubling the power that is creating a given sound, whether by duplicating the sound's source (i.e., doubling it) or increasing the energy creating the sound in one source (i.e., doubling it) results in an increase of loudness described as 3 decibels.
Another poster answered that the increase in loudness from adding an identical sound to an existing one would be described as 6 decibels.
I was and still am curious to understand why that was. If I'm understanding you correctly, you're saying that duplicating a a specific sound results in a SPL increase of 6db?
position in relation to the speakers also factors in,
if i place a single 15 on top of my other 15, adjust no settings I have slightly less than double wattage coming from the amp due to halved impedance. Each speaker receives slightly less than when it was just 1 speaker. At 6ft tall 3 feet away this is a massive jump in volume. on stage 30 feet back in the audience the difference would be considerably less.
That's not how it works. If you double the speaker count with constant voltage you double the cone displacement. You can double the cone displacement by adding power instead, assuming that the speaker can take it, but you don't double the displacement with double the power. It takes double the voltage to double the displacement. Double the voltage is four times the power. Four times the power is 6dB. It's a pretty simple concept if you know Ohm's Law, but really confusing if you don't.
Which you would get with a solid state amp if you added a second identical speaker in parallel, would you not? Or am I not holding my mouth right?
Well, not all SS amps double their output going from 8 to 4 ohms.
Also wanted to be specific about the power having to double as well as speaker area doubling to get the 6db (which does not happen with tube amps).
You got the right ideas but your examples are all cockahoop.
Voices are completely out of phase. Maybe you do get a 3dB measurable loudness increase from one to two!
Twin amp combos will be well phase matched and using twice the power for resulting 6dB.
If anyone is staying to feel paranoid here is what to do.
Dial up the beefiest tone you will need, emphasis on need rather than desire. Rip into it. Earplugs compulsory. Listen for distress. Turn up until you get some. Then back off the volume knob,, never to return.
If you need every last decibel you can back off lows to get more low mids. Then another failure mode rears up. Thermal handling limit.
If turning up doesn't get much louder you are getting close. Turn back down a squidge.
Listen out for getting quieter by itself when you are going for gold. Failure is imminent, quit that and buy more rig.
Dial up the beefiest tone you will need, emphasis on need rather than desire. Rip into it. Earplugs compulsory. Listen for distress. Turn up until you get some. Then back off the volume knob,, never to return.
If you need every last decibel you can back off lows to get more low mids. Then another failure mode rears up. Thermal handling limit.
If turning up doesn't get much louder you are getting close. Turn back down a squidge.
Listen out for getting quieter by itself when you are going for gold. Failure is imminent, quit that and buy more rig.
Thanks, maybe if you correct my mistaken understanding at the point that it's occurring…I'll step through it, point by point to see where we differ…
As to sound power related to loudness in decibels, increasing sound power by a factor of 2 is stated as increasing loudness by 3 decibels, correct? Increasing power by a factor of 4 is stated as increasing loudness by 6 decibels, correct?
As directly to wattage and speakers related to loudness in decibels, sound power is not increased between one 10" speaker receiving 50 watts and two of the same 10" speakers receiving 25 watts each, correct? Down 3 for halving the power (each) and back up 3 for doubling the speakers.
Two ways to create a 2x power increase (so +3db) over one 10" speaker receiving 50 watts, would be to give that speaker 100 watts or give two of the same speakers 50 watts each, correct?
In the hypothetical of two identical amps, in the first amp, you have 4 speakers receiving 50 watts each. Double that is 8 speakers receiving 50 watts.
Why has the sound power increased by a factor of 4?
"sound increasing by a factor" is a non statement as it is outside of the terminology used to make the maths fit what we hear.
Bell Labs tested and tested. On average what was heard as twice as loud took ten times the power. They worked the description with the maths to transform SPL into a linear scale, saves a bucketload of graph paper.
Bell Labs tested and tested. On average what was heard as twice as loud took ten times the power. They worked the description with the maths to transform SPL into a linear scale, saves a bucketload of graph paper.
Most folks think in terms of watts, which is fine.
What amplifiers really are, are voltage multipliers.
Voltage squared divided by impedance equals watts.
Take for example my little 400RB. Hook a meter up to the outputs and it can push about 34 volts at 8ohms, which works out to about 145 watts.
Push the same 34 volts at 4ohms and it works out to about 290 watts.
The amp is rated 200 watts.
Why the discrepancy?
Power supply, and/or current capacity (and necessary limiting thereof) of the output devices like most (transistor) amps.
Music signal is A/C voltage, be it the little signal from your pickup or the big signal out the back of your amp.
What amplifiers really are, are voltage multipliers.
Voltage squared divided by impedance equals watts.
Take for example my little 400RB. Hook a meter up to the outputs and it can push about 34 volts at 8ohms, which works out to about 145 watts.
Push the same 34 volts at 4ohms and it works out to about 290 watts.
The amp is rated 200 watts.
Why the discrepancy?
Power supply, and/or current capacity (and necessary limiting thereof) of the output devices like most (transistor) amps.
Music signal is A/C voltage, be it the little signal from your pickup or the big signal out the back of your amp.
Where the wheels come off is at your doubling / splitting power contention. Doubling cone count is by itself more efficient at moving air. As it turns out, 3dB more efficient. Neeato!
The decibel measurement goes back to the invention of/standardization of, the early telephone system, as does the 1/4" plug and the standard width rack. This stuff wasn't originally designed for music gear, it just happened to work well there too, as far as standardization, mixing/matching/integrating various equipment, etc.
That's the basic misunderstanding. Doubling loudness is 10dB. That takes ten times the power. Doubling the cone excursion is 6dB. That takes twice the voltage. Double the voltage is four times the power. Doubling power doesn't double the cone excursion, it only increases it by 1.4 times, that's 3dB. If you keep the voltage the same but use two speakers instead of one you get the same 6dB that you would if you used one speaker with double the voltage.
