You're talking about power. It's 10dB for loudness.

Wikipedia:

A 3 dB increase in the level of continuous noise doubles the sound power, however experimentation has determined that the response of the human ear results in a perceived doubling of loudness for approximately every 10 dB increase.

Btw.. that wasn't tuned or anything, i just turned up the volume until it sounded like ass, 3/4 volume. I'm sure i could have tuned it to a speciffic frequency and taken measurements at a better place then the glovebox.





Next week or the week after I'll be checking a manufacturer's install of audiometeric equipment and I might have another opportunity to use this bad-mamma jamma. Any recommendations from experienced SPL competetors would be appreciated. It will take a few minutes to figure out where my tuning sits, but how can i be sure I don't blow my speaker out of it's suspension?

 

good to know man...i just remember from an electronics class about 3 db is double but thats cool 10 for loudness...what i did man was to get some "peel and seal" stuff at lowes its like dynamat but at a fraction of the cost, just double layer the bottom of your trunk and and the sides and back of it...also you can take the top cover off your hatch and layer that with the peel and seal stuff...anything to keep the sound in...make sure your car is as air tight as possible...keep me posted

 

yea, a decibel is simply a unit used to express a relative difference in power or intensity, a bel itself (named after Alexander Graham Bell) is not a unit of power, rather a logarithmic (not linear) difference between power, intensity, voltage, current, etc.

dB's are just most commly used to measure sound intensity (loudness), since one dB is (very close to) the JNF, Just Noticeable Difference in sound intensity.

the decibel law is 10log Intensity / Reference Intensity, but since sound intensity is proportional to the square of pressure, the equation you see in 9th grade is

10log Pressure^2 / Reference Pressure^2 = 20log Pressure / Reference Pressure

Reference P is usually .0002 microbars, as you all (turbo guys) know SL pressure is 1 bar (dyne/cm^2)

So increase your output intensity (in the case of sound Pressure difference) by a factor of 2 and you have gone up 3dB.

4x intensity = 6dB
10x intensity = 10dB (or 1 bel)
100x = 20dB
1,000x = 30dB
10,000x = 40dB

by the time you get to the pain threshold of 120dB (for most) the sound intensity is something like 1 trillion times the reference intensity.

 

with a crappy db tester I think I hit around 140-150 with my 3 10s... but not sure if that was my subs or my-mids/highs putting the spl up that high =P... just wanted to see house loud my car was and still sound great

 

I was able to hit 144.3 db with one 12" kicker L7 solo baric a few years ago. Running on a 500x1 watt JL amp.

I then hit 146.7 with 3 of the same subs in a massive SPL ported box running on 2 1200x1 kicker amps. With just 2 solo baric 12's, and one 1200x1 going to each, I hit 147.5. Just proves that to increase the db by 3, you need twice the surface area of sub and at least twice the power. I don't think the kickers were putting out a full 1200 each, but the JL was definately putting out at least 500. Rule of thumb is for real power, you need to pay a dollar a watt. So if I paid 600 for a 1200 watt amp, it likely only outputs 600 watts you know? If you are paying less than half of the wattage rating on your amp, it definately doesn't output what it is rated at.

But people that heard it swore it had to be louder. I cracked my windshield (I watched it crack during a demonstration I was giving) and anyone other than me that was in it with it all the way up instantly covered their ears and rushed out. LOL.

Good times, shook the car to hell though. Not to mention my hearing is permanently damaged from it. Do heed warning to the stickers that come with your subs that mention the permanent hearing loss.

 

definantely man...one reason i stopped listening to the bass...as far as the amp and dollars thing goes...i think it really depends on the ohms you are running at and what brand of amp....you can get a orion 600d for like 250 online and i know that definately puts out the power its rated...if your looking into amps look for the consumer electronics seal of approval.

 

I'm talking max, not RMS. I don't have RMS details for my amp or speaker, just max 1400 and max 1200. The fuses are rated at 40A each, so I know that it has the capabilities to draw nearly 1200W before blowing the fuses. I have no idea what the RMS is. It looks like the values you were talking about were mixed.

Your watt-dollar rule is completly fubar. You can go ahead and spend that ammount.. Amps are not hard to make nor are they expensive to manufacture. The only reason they don't make 20,000W car amplifiers is there is no market for them. Noone has the alternators to run them. Amps will sell for whatever you will buy them for. The class A/B/C amp technology is 70 years old. If i took 10 days out of my life i could create a 10,000W amp that had perfect fidelity.

You'll get quite a different price at a local store which has to have a front then a remote warehouse.

 

check out hifonics, they have an amp thats rated up to 10k i think...anyways i agree with not spending 1 dollar per watt