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

[Carl]

I still think it wouldn't take off...

[tommk3cab]

Originally Posted by Carl

I still think it wouldn't take off...

what about the petunias?

[Skeelsie]

Originally Posted by Carl

I still think it wouldn't take off...

The treadmill will make no difference, it's only effect would be the need to overcome the friction of turning the wheels. Unlike a car, the plane does not drive it's wheels. So the treadmill is a red herring.

[Carl]

Uh oh...

[tdr]

Originally Posted by TwoBlackLines

TDR why do you edit all your posts after being corrected lol! we can see it "last edited by tdr on xxx"

You would be correct if we were talking about doubling voltage. but we arent, we are talking about doubling the power.

erm we are talking about double the SPL. Last time I checked that near universally means Sound Pressure Level.

To double the SPL you need 4 times the power!

To those who said it means 'Sound Power Level' well actually there is no such thing. The correct term is Sound Intensity, which is the sound power per unit area.

Someone above mentioned that you wont actually get a 6dB gain in the real world - yes these are ideal world figures.

[timreeves]

Originally Posted by tdr

erm we are talking about double the SPL. Last time I checked that near universally means Sound Pressure Level.

And that makes you wrong, to double the SPL you need 4 times the power!

To those who said it means 'Sound Power Level' well actually there is no such thing. The correct term is Sound Intensity, which is the sound power per unit area.

And to acknowledge those above that mentioned that you wont actually get a 6dB gain in the real world, yes these are ideal figures.

which is actually used incorrectly most of the time

[tdr]

Originally Posted by timreeves

EDIT: with regards to the original question, if we're referring to a doubling in pressure as a doubling in dB-SPL then 6db is the correct answer. factoid.

And another ones gets it. We are getting there...

[micb]

As stated theory is one thing, real life is another!

In theory:

Double power to a system (without power compression) is 3db.

Double power and double cone area (with appropate enclosure as well) is 6db.


In real life testing has shown at lower levels before power compression you can gain more than 3db when doubling power.

In real life testing when you start compressing hard you only gain 1.5db and often even less.

There are plenty of other factors other than power compression, driver loading (both from other surfaces and changes your cabin i.e. windows), enclosure, aiming, frequnecy, power supply sag (both in amp and car), cabin flex, phasing, cancelation that come into play that throw the theory out the window so to speak.

[chrig]

TDR - Get yourself some SPL testing equipment, get yourself a few subs, get yourself a few amps (shouldnt be a problem getting either should it?) knock up a few enclosures, and then start testing your theory. Video / take pictures of your results and then come back and explain your theory with some real world figures to back it up.

Stop with all the ******** formule which really don't matter, what we care about is what happens in real life, in our cars, with the equipment we are spending our hard earned on. not what wikipedia says will happen. You give off the imperssion that you have had everything explained to you at some point, but that you dont actualy have any real world experience in the matter Show us that this isn't the case.

I'm sure people will admit they where wrong if/when you come back with some evidence, and not just maths

[Kineticz]

I think that if you double SPL, you get an extra 20hp coupled with bolting on the K&N yo.

[Buju Banton]

Originally Posted by Kineticz

I think that if you double SPL, you get an extra 20hp coupled with bolting on the K&N yo.

If I add a Vtec to my system, what dB will I gain dude? will it double?

[chrig]

from a vtec you only gain dB once it 'kicks in yo' at level 3 our of 5 on the Air conditioning fan level

[Kineticz]

I would expect to see gains in excess of 160db powering a 10" Sony Xplod in a 0.6cuft leaky box fo' sho'. So to your system Jim I would be aiming for around 175.2db if you fit vtec. If you turn the heater fans on and point them all towards the termlab you will force the sound pressure against the sensor.

[timreeves]

Originally Posted by chrig

TDR - Get yourself some SPL testing equipment, get yourself a few subs, get yourself a few amps (shouldnt be a problem getting either should it?) knock up a few enclosures, and then start testing your theory. Video / take pictures of your results and then come back and explain your theory with some real world figures to back it up.

Stop with all the ******** formule which really don't matter, what we care about is what happens in real life, in our cars, with the equipment we are spending our hard earned on. not what wikipedia says will happen. You give off the imperssion that you have had everything explained to you at some point, but that you dont actualy have any real world experience in the matter Show us that this isn't the case.

I'm sure people will admit they where wrong if/when you come back with some evidence, and not just maths

I'm sorry but imo you sound like an idiot.
if your gonna take this scoring high thing seriously i'm pretty sure it would be a damn fine idea to brush up on the physics side of things. Not just trial and error. He's also said that these are for idealistic reasons not what will happen. I think alot of people rely on what one other person has said as gospel, it may have been correct in some ways it's highly likely it isn't in others.

[TwoBlackLines]

I guess 50 people are wrong and TDR is right, then.

[chrig]

Originally Posted by timreeves

I'm sorry but imo you sound like an idiot.
if your gonna take this scoring high thing seriously i'm pretty sure it would be a damn fine idea to brush up on the physics side of things. Not just trial and error. He's also said that these are for idealistic reasons not what will happen. I think alot of people rely on what one other person has said as gospel, it may have been correct in some ways it's highly likely it isn't in others.

I never said there was anything wrong with having the physics correct, but its a waste of time knowing it all and not actualy using it isn't it or knowing how this works in real life? By actualy doing things and and seeing how things happen you gain a better understanding why and how this happens, especialy after you have learnt it on paper. well in my experience anyway.

Going in to big details about how something would work in a lab seems like a bit of a waste of time to me, I prefer to actualy test and see how things work in real life than learn about the maths behind it. Obviously too have a good understanding you need to have both parts experience and knowledge, but the experience is often the more usefull one, imo of course.

Each to their own i suppose, everybody has diffrent ways of learning and the use of formule (sp?) alone really does annoy me.... maybe thats why i'm no good in thermodynamics lectures

[Kineticz]

Originally Posted by TwoBlackLines

I guess 50 people are wrong and TDR is right, then.

IMO the poll has very little credibility in this discussion. 1 person could tell 49 people that it's 3db and they may all solely believe it is correct. Doesn't mean that it is correct.

[tdr]

Originally Posted by chrig

I'm sure people will admit they where wrong if/when you come back with some evidence, and not just maths

The original question is a mathematical one - double SPL is a 6dB gain. Real world or otherwise.

It is only the example I used of adding a second sub (with identical amplification) that wont give you exactly 6dB in the real world.

[mattcambs]

I've just done an experiment!

Using 2 identical 5" woofers and CLIOWin7 I have compared the frequency response (dBSPL) of 1 with the frequency response of 2 (placed next to each other connected in parallel). The output signal was reduced by 3dB when testing the 2 woofers in parallel so that for both tests only the radiating area has changed.

The SPL of the single woofer was made on axis at 16cm and the MLS signal gated so as to not include the room response. For the 2 woofer measurement the mic was placed centrally between them at 16cm from the centre of each cone. [the woofers were un-baffled]

With the 2 woofer measurement, the dBSPL above 1kHz is neglected because the microphone is off-axis. So: taking the region from 200Hz to 1kHz the difference is:



[I obtained the same result using a stepped sinewave output]

By my findings, if you double cone area you gain 3dB

[tdr]

Nice. And if you dont reduce the output level by 3dB presumably you get a 6dB gain.

[mattcambs]

Originally Posted by tdr

Nice. And if you dont reduce the output level by 3dB presumably you get a 6dB gain.

Indeed Which would be double the radiating area and double the power.

Not that this answers the original question exactly, because I don't think we have established what that was exactly!

Where has the OP gone? [maybe he fell asleep!]

[chiark]

Originally Posted by tommk3cab

what about the petunias?

I believe they thought "Oh no, not again"

[tdr]

Wasnt that the Whale?

[tdr]

Originally Posted by mattcambs

Indeed Which would be doub)le the radiating area and double the power.

I.e. adding a second speaker (with the same power as your first one.)

[John Dorian]

Originally Posted by Kineticz

I would expect to see gains in excess of 160db powering a 10" Sony Xplod in a 0.6cuft leaky box fo' sho'. So to your system Jim I would be aiming for around 175.2db if you fit vtec. If you turn the heater fans on and point them all towards the termlab you will force the sound pressure against the sensor.

Don't forget the cap has to be on backwards