Sub size and SPL question

[BringDaBoom 10+ year member]

I kinda have the feeling the answer/s will be a "it depends", so if it is please explain.

You have Sub A and Sub B. Both are of the same type (I.E. SPL, SQ, SQL, etc), and will be powered by the same amplifier providing the same ammount of power to each.

Sub A is a 10"

Sub B is a 12"

Each is in a sealed box built to the specs of the sub.

Question 1.) The 12" should displace more air, thus having more SPL, correct? Logic would say yes, no?

Question 2, the real question depending on the answer to 1.) : If you have a specifc model sub (be it a 10", 12", 15") that is said to displace the same ammount of air as two specific model smaller subs, then given the oppourtunity to place that larger sub in it's optimum enclosure (For the sake of argument, let's say sealed), it shoud match the SPL of the two smaller ones (put in their optimum enclosure also sealed), provided they are fed the same power, correct?

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[tom4info 10+ year member]

dude you lost me at question #2

 

[audioholic 5,000+ posts]

In a sealed environment, displacement (Sd * xmax) reigns supreme. Get two systems running sealed that dispalce the exact same amout of air, have same enclosure alignment etc, and yes output should be approx the same. Given the same listening environnment etc as well of course...

Im afraid if I attempt to get any more generic than that I will be over generalizing.

 

[BringDaBoom 10+ year member]

In a sealed environment, displacement (Sd * xmax) reigns supreme. Get two systems running sealed that dispalce the exact same amout of air, have same enclosure alignment etc, and yes output should be approx the same. Given the same listening environnment etc as well of course...
Im afraid if I attempt to get any more generic than that I will be over generalizing.

No, that's perfect. And I agree.

So in essence...a single sub rated to displace the same as two smaller subs (given all the equal parameters you listed) should produce relatively the same ammount of out put, correct?

-NOW- How about ported? (again, giving both the same parameters, I.E. same port design, port tuning, specifed for each sub, same power, etc)

 

[audioholic 5,000+ posts]

No, that's perfect. And I agree.
So in essence...a single sub rated to displace the same as two smaller subs (given all the equal parameters you listed) should produce relatively the same ammount of out put, correct?

-NOW- How about ported? (again, giving both the same parameters, I.E. same port design, port tuning, specifed for each sub, same power, etc)

Air displacement specs will not tell you the whoole story. You are ignoring speaker efficiency now, to name one problem.
As for ported, dont even try to go there. Porting the enclosure adds too much complexity for us to try and make such generalized statements and still hope to remain accurate. Excursion becomes a much less important factor, and thermal power handling becomes much more important. Now add to that the compexity of an infinite number of box sizes/tuning combinations, firing directions, etc etc... and it quickly becomes obvious its too complex an issue to say 'will sub A perform the same as sub B given this one same shared perameter'.

 

[skadude016 5,000+ posts]

No, that's perfect. And I agree.
So in essence...a single sub rated to displace the same as two smaller subs (given all the equal parameters you listed) should produce relatively the same ammount of out put, correct?

-NOW- How about ported? (again, giving both the same parameters, I.E. same port design, port tuning, specifed for each sub, same power, etc)

you start getting in to way to many variables honestly. but in theory yes it should be the same as sealed. but that is theory not real application

 

[audioholic 5,000+ posts]

you start getting in to way to many variables honestly. but in theory yes it should be the same as sealed. but that is theory not real application

Not true. Ported and sealed applications highlight and stress different design aspects of a speaker. As I said above, linear displacement potential becomes a much less important figure. Where as in sealed applications that, plus system efficiency, are just about all that matters (beyond environmental effects).

 

[Immacomputer 10+ year member]

You can't really compare sub A to sub B in a ported enclosure without including enclosure A and enclosure B in which there are an infinite amount of configurations for each like Audioholic mentioned. You also have to look at the port area as it will be creating the majority of the output around tuning. Also, when you are around tuning, the motor force of the driver chosen is going to play a large role in output. At that point, it's all about how well the sub can drive the enclosure into resonance and how well the enclosure can drive the cabin into resonance.

 

[BringDaBoom 10+ year member]

I understand. Thanks alot for the explanations guys. Much appreciated

 

[hoxie08 5,000+ posts]

i got confused //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[skadude016 5,000+ posts]

Not true. Ported and sealed applications highlight and stress different design aspects of a speaker. As I said above, linear displacement potential becomes a much less important figure. Where as in sealed applications that, plus system efficiency, are just about all that matters (beyond environmental effects).

im talking about in theory in a perfect enviroment. if sub A (12) takes 1000rms to reach full potential. bot B subs (10's) take 500 rms each to reach full potential. and everything is perfect in theory they should be extremly close in output. although the 2 10's would have a slight cone advantage. but we all know theory has been disproven time and time again.

so yes we do agree that in a real application there are way to many variables to even begin to figure out which A or B woofer(s) would be louder //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[audioholic 5,000+ posts]

im talking about in theory in a perfect enviroment. if sub A (12) takes 1000rms to reach full potential. bot B subs (10's) take 500 rms each to reach full potential. and everything is perfect in theory they should be extremly close in output. although the 2 10's would have a slight cone advantage. but we all know theory has been disproven time and time again.
so yes we do agree that in a real application there are way to many variables to even begin to figure out which A or B woofer(s) would be louder //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

There is more to it in a vented envorinment than simply efficiency of the speaker. And in a ported box there is almost no such thing as the amount of power input to reach full potential. Remember, thermal issues will become a problem in a ported box long before mechanical failure becomes an issue.
I understand what you are trying to say, but again its just to simplified to apply to any real-world situation. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[skadude016 5,000+ posts]

There is more to it in a vented envorinment than simply efficiency of the speaker. And in a ported box there is almost no such thing as the amount of power input to reach full potential. Remember, thermal issues will become a problem in a ported box long before mechanical failure becomes an issue.
I understand what you are trying to say, but again its just to simplified to apply to any real-world situation. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

ya I hear ya.

if its any consolation to the OP alot of street A guys use 2 10's in there setups and seem to do well. //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif