# Thread: Decibal Output Question

1. ## Decibal Output Question

If for example, a single 10" subwoofer with 350rms watts running through it put out 45dB... what woould the dB output be when another 10" sub is added with 350rms watts running through it also? Is it generally 2x the output in decibals or a little less...?

2. oops not 45 db.. that was just a random value... A more accurate dB for the 10" is 110.

3. If you could double your db's but just adding another 10" sub in there, you'd be the current db world record holder. The answer to your question is the increase would be a lot less than double.

4. its 3db more, double the input and you get a 3db increase

5. Originally Posted by Nic
its 3db more, double the input and you get a 3db increase
some one listened in physics

if i remeber,, u will double the pressure level

6. i have a phyics exam soon :S i wish it was on that stuff tho, its on quantum physics which is hell hard compared to f=ma

7. Good luck with your exam

8. thanks, i'm gonna need it :P

9. the general rule of thumb is that if you double your cone area you will double your pressure - meaning you will gain 3 db. Also, if you double your power you will double your pressure, meaning an additional 3 db.

but there is a point of diminishing returns here.

if you look at the SPL vehicles of a few years ago they all used a massive amount of subs and even more power. The gobs have power has stayed the same, but they are now realizing that you can get higher numbers with less subs and a better built box....not to mention a smaller vehicle (less air space to build pressure in)

contrary to what a lot of people think, competing in SPL can be a heck of a lot of fun!

10. yes. double cone area, double power, add 3 db. so a second 10 with a second 350 rms would yield a total of 6 dB on the meter..... max

I struggled with this for a long, long time. what it comes down to is that the meter is not a measure of air "pressure" but rather accoustic "energy". Or is it the other way around? Honestly, it doesnt matter.

the point of the matter is that the meter will read 6 dB (max) higher when you double your displacement. which is exactly what you are doing by adding both a subwoofer AND doubling power.

now, the funny thing to keep in mind is that because of this, while the relationship between excursion and power requirements is still linear, its not a 1 to 1 relationship! Thus, to double the excursion (remember double excursion is double the air motion and therefore a 6 dB gain on the meter!) keeping only one subwoofer would require FOUR times the power! Thus we see that the rule of double power for a 3 dB (max!) gain holds true! assuming the cone of the woofer can actually travel that far!

last thing to think about is, why make the distinction between energy and pressure? well, doubling the excursion IS just a 3 dB gain! in pressure (or is it energy? Honestly, it doesnt matter). Thus, we need double the power AND double the cone area to get our 3 dB gain! but the meter will read 6 dB (max!) up.

get it?

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