is 3dB, 6dB or 10dB double the SPL???

[Dan.]

Please participate in the poll, and select the one which YOU believe to be true.

[MC_Bob]

As far as I understand it, 3db = double the energy, 10db = double the volume percieved by the ear.

Fook knows the actual ratings/theory.

[Beb]

I've always thought 6db was double to the ear, or was it double SPL

How are you meant to measure double to the ear anyway

[WonkyJon]

3db=double the SPL - noticeable to the ear

10db=perceived to be 2x louder

IMHO of course

[Edgey]

So if I doubled my cone area and power are we saying 10db? Sorry just trying to understand

[jazzy639]

Taken from Wikipedia:

It is seen that there is a 10 dB increase (decrease) for each factor 10 increase (decrease) in the ratio of the two power levels, and approximately a 3 dB increase (decrease) for every factor 2 increase (decrease). In exact terms, the factor is 103/10, or 1.9953, about 0.24% different from exactly 2. Similarly, an increase of 3 dB implies an increase in voltage by a factor of approximately √2, or about 1.41, an increase of 6 dB corresponds to approximately four times the power and twice the voltage, and so on. (In exact terms the power factor is 106/10, or about 3.9811, a relative error of about 0.5%.)

I had always thought 3db = twice SPL/as loud

Certain websites say:

Interestingly, our perception of loudness is not the same as sound pressure level. Although the actual formulae
is somewhat complex, as a rough rule of thumb, an increase of 10db SPL is perceived to be approximately twice as loud.

[marko]

Originally Posted by Edgey

So if I doubled my cone area and power are we saying 10db? Sorry just trying to understand

no 3db, or there abouts.

[jazzy639]

Double power = 3db, double loudness = 6db (10db to our ears) I think

[Buju Banton]

Its 10!

Its a logarithmic scale as in 10 to the power of 3 blah blah
so its 10x10x10

so a system with a 10w amp will do a db level
you need 100W not 20W to make it twice as loud again (10db) (10x10)
you need 1000W to make it twice as loud again another 10db etc. (10x10x10)

Thats why power you need 10 times the power to get it twice as loud again

my 2p

[WonkyJon]

are you thinking of double the figure chap?
1,2,4,8,16,32,64 etc...

I hope I dont need 30,000watts to get 148db!
(of course, i may have misunderstood completely!)

[Buju Banton]

No, I was just using power alone as an example.

If you had a boggo sub and box etc and were doing 145db off 2k, to get a 155 you would need 20k without changing anything else.

Obviously thats why you build better boxes use spl subs and secrets etc because you cant just keep throwing power at it.

Perfect world example cos obviously you wont get 14.4V at 20,000W
Thats how I understand it.

EDIT: Its not double the power thats just 2x2, its x3 so its 10, 1000, 10000, then 10000 x 10000 x 10000 etc

2nd edit: Yeah double the power should give you a 148, but you would need 20k to do a 155!

Better explanation here cos I suck
http://www.phys.unsw.edu.au/jw/dB.html

[puggie]

double the power is +3db,

doubling power and cone area should give about 6dB (eg adding a second sub to an existing system if the amp will load down to half the impedance happily enough)

10dB is a percieved doubling of loudness, but it goes a bit funky at higher SPLs due to our ears sensitivity varies at different frequencies according to loudness (google fletcher-munsen curves if you want to know more).

[thejoose]

Originally Posted by puggie

our ears sensitivity varies at different frequencies according to loudness (google fletcher-munsen curves if you want to know more).

Its that sort of behaviour that makes people think that some tunes have bass lower than it really is (THATS LOWWWW THREADS FTL)

[puggie]

Originally Posted by thejoose

Its that sort of behaviour that makes people think that some tunes have bass lower than it really is (THATS LOWWWW THREADS FTL)

Yep you can usually lose the bottom octave of stuff and 95% of people will not realise if you do your processing right.

[captainobvious]

Doubling your amplifier power gives you a 3db gain increase.

[tdr]

SPL = 20 log x/y

Its measured like voltage - both are 'pressures' NOT powers

So twice the SPL = 20 log 2 = 6dB difference in SPL.

That is why adding a second identical sub adds 6dB to your SPL...

If you mean human perception of double the SPL then its 10 dB.

Amazing that 38 / 47 people got it wrong.

[Dan.]

Originally Posted by tdr

SPL = 20 log x/y

Its measured like voltage - both are 'pressures'

So twice the SPL = 20 log 2 = 6dB difference in SPL.

That is why adding a second identical sub adds 6dB to your SPL...

If you mean human perception of double the SPL then its 10 dB.

Amazing that 31 / 37 people got it wrong.

actually I knew the answer.... and your wrong
Adding another sub increases efficiency (twice the surface area) +3dB
If you are adding another sub and doubling the power (say 100 watts on each rather than 100 watts on one) that is another 3dB
hey presto we have 6dB

*nb this is theory, actual numbers in practice will be lower.

[blackjack]

oh dear once again TDR comes in and gets it WRONG!!!!!!!

this has to be one of the famous always asked questions and the answer is always the same

3db's is double the spl
10db's is double to the ear.

please dont try and argue this one TDR you WILL lose

[Buju Banton]

Gotta agree with dan.

I had 1 15" sub and 1 amp = 140.8db
then 2 15's and 2 amps = 146.3db

So 5.5db approx for double power and cone area based on Dans theoretical 6db.

(Both of these scores measured on the official dBdag TL sensor)

@Mr TDR. No offence chap, but if you keep arguing/disagreeing with everyone on here, then its only going to hurt your future sales. No one will buy anything from you no matter how cheap and everyone will be cautious with a view to warranties etc based on how your perceived by other forum members.

If you want to get anywhere start taking a leaf out of Chris@Axis book, he attends shows, smiles and LISTENS to his potential future customers hence more people turning to CDT and Atomic.

[mattcambs]

dB(in voltage terms) = 20log(V1/V2)
dB(in power terms) = 10log(P1/P2)

Combined dB = 10log([10^(dB1/10)]+ [10^(dB2/10)] + [10^(dB3/10)] etc, etc)

So adding two identical SPL sources gains you 3dB as others have said - just thought I'd show the equation.

The 10dB percieved doubling of loudness is a figure most acousticians agree on from doing experiments on large samples of people. There is no correct answer here, just for most people it tends to be about 10dB.

Seeing as this is a poll, the above is just my opinion!!!

[timreeves]

Originally Posted by blackjack

oh dear once again TDR comes in and gets it WRONG!!!!!!!

this has to be one of the famous always asked questions and the answer is always the same

3db's is double the spl
10db's is double to the ear.

please dont try and argue this one TDR you WILL lose

Sorry, you both lose.
there's SPL and SPL one's sound pressure level, the other sound power level.
you lot mainly seem to stick to pressure, whereas my lecturer uses power. IIRC in these circumstances 6db is correct for SpowerL and 3db is correct for SpressL

[mattcambs]

Originally Posted by Buju Banton

Gotta agree with dan.

I had 1 15" sub and 1 amp = 140.8db
then 2 15's and 2 amps = 146.3db

So 5.5db approx for double power and cone area based on Dans theoretical 6db.

That would be correct considering you doubled cone area (i.e doubled SPL) and also doubled power (i.e. added another amp).

[tdr]

Originally Posted by Dan.

actually I knew the answer.... and your wrong
Adding another sub increases efficiency (twice the surface area) +3dB
If you are adding another sub and doubling the power (say 100 watts on each rather than 100 watts on one) that is another 3dB
hey presto we have 6dB

*nb this is theory, actual numbers in practice will be lower.

It is well known that adding a second sub gives you a 6 dB gain

Twice the surface area AND twice the power - either via another amp or via half the impedance to same the amp.

So its exactly twice what you started with.

Also giving you twice the SPL = 6dB from the basic maths above so as I stated - those that said 3dB are wrong

[tdr]

Originally Posted by mattcambs

That would be correct considering you doubled cone area (i.e doubled SPL) and also doubled power (i.e. added another amp).

Just doubling the cone area does not double the SPL if you shared the same power between the 2 speakers.

Double cone area + same power = only a 3 dB gain which is not double the SPL.

[tdr]

Originally Posted by blackjack

oh dear once again TDR comes in and gets it WRONG!!!!!!!

this has to be one of the famous always asked questions and the answer is always the same

3db's is double the spl
10db's is double to the ear.

please dont try and argue this one TDR you WILL lose

Common mistake to confuse power dB with pressure (voltage / SPL)

Im not wrong.

Let me do the basic maths again in detail.

Lets say you have a car with an SPL of 2 Pascals.

You double the power and cone area by adding another sub and get a new SPL of 4 Pascals.

SPL gain = 20 log (4/2) = 6dB

Going back to the original question:

"is 3dB, 6dB or 10dB double the SPL???"

Clearly if you are talking about absolute values it is 6dB. Those that say 10dB are also correct if you mean perceivied doubling of SPL. 3dB is incorrect.

Originally Posted by mattcambs

dB(in voltage terms) = 20log(V1/V2)
dB(in power terms) = 10log(P1/P2)

Try quoting dB in SPL terms!

Originally Posted by mattcambs

Combined dB = 10log([10^(dB1/10)]+ [10^(dB2/10)] + [10^(dB3/10)] etc, etc)

Actually that formula would be corrrect - if we were talking about INCOHERENT radiating sources. However we are not.