1 vs 2 subwoofer modeling +\-3 question - AVS Forum
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post #1 of 6 Old 06-12-2014, 05:58 PM - Thread Starter
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1 vs 2 subwoofer modeling +\-3 question

I'm a bit confused. When I model a ported box from tsp from the sub driver, I come up with a +\- 3db measurement much lower in hz than if I model 2 of the same driver. Does my SPL increase in this case, but my +\- 3db separate further? Is it better to build two separate enclosures for the 2x12" subs? Right now, this is for a home theater. The original sub was a 2x12 klipsch rw12 drivers with an 18" passive radiator. It is currently setup as a 2x12 triangular sub, sealed.

I have no issues trashing my previous configuration and starting new boxes if needed.
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post #2 of 6 Old 06-12-2014, 06:19 PM
 
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I'm a bit confused by the wording of your question... If you add a driver (doubling displacement), you get a 3 dB increase. If you double the power, you get a 3 dB increase.

So say you have 1 sub, 1000 watts, 100 dB.

2 subs, 1000 watts is 103 dB,

2 subs, 2000 watts is 106 dB,

4 subs, 4000 watts is 109 dB,

8 subs, 8000 watts is 112 dB, etc.

if you're talking about the - 3dB (f3) point, if you add another driver and don't change the box size, then it basically is halving the volume of the box, which will make it have a worse -3dB (f3)point.
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post #3 of 6 Old 06-12-2014, 06:32 PM - Thread Starter
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Quote:
Originally Posted by JWagstaff View Post
I'm a bit confused by the wording of your question... If you add a driver (doubling displacement), you get a 3 dB increase. If you double the power, you get a 3 dB increase.

So say you have 1 sub, 1000 watts, 100 dB.

2 subs, 1000 watts is 103 dB,

2 subs, 2000 watts is 106 dB,

4 subs, 4000 watts is 109 dB,

8 subs, 8000 watts is 112 dB, etc.

if you're talking about the - 3dB (f3) point, if you add another driver and don't change the box size, then it basically is halving the volume of the box, which will make it have a worse -3dB (f3)point.
So the f3 point of one 12" "a" driver is the same as f3-3db of two 12"a" drivers, correct?
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post #4 of 6 Old 06-12-2014, 06:40 PM
 
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yes, the f3 will be the same, but it will be at a higher SPL (either 3 dB or 6 dB depending on power). With the extra SPL, it allows you to EQ more, to get a flatter response.

edit: like bill says below, the box volume per driver has to stay the same.

Last edited by JWagstaff; 06-12-2014 at 06:43 PM.
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post #5 of 6 Old 06-12-2014, 06:41 PM
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If you put two drivers into the same size box as one then f3 will go higher. You have to make sure you keep the box volume per driver the same. If you model two drivers with constant power sensitivity will go up by 3dB. Model with constant voltage (assuming parallel wired) and sensitivity will go up by 6dB. You'll usually get a better result with drivers in separate cabs, allowing placing them apart for smoothing of room response. The main reason for using two drivers in one box is if they're opposed, to keep the sub from dancing at high power levels.
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post #6 of 6 Old 06-13-2014, 02:30 AM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post
If you put two drivers into the same size box as one then f3 will go higher. You have to make sure you keep the box volume per driver the same. If you model two drivers with constant power sensitivity will go up by 3dB. Model with constant voltage (assuming parallel wired) and sensitivity will go up by 6dB. You'll usually get a better result with drivers in separate cabs, allowing placing them apart for smoothing of room response. The main reason for using two drivers in one box is if they're opposed, to keep the sub from dancing at high power levels.

Thanks guys, answers my question perfectly!
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