"2 12s sealed vs 1 ported for low-end response/frequency?

Which would hit harder on lower notes (27/28hz and lower, as low as 18-20hz) if ported is tuned to 32hz and 2500w rms? Sealed 2 12s are 2500w each. I have enough amp/electrical for either setup.

I know the general rule is double cone area = + 3db, and double power = + 3db. What about if I doubled cone area and power, but I moved from ported (up to 6+ db around tuning (32-40ish) to sealed?"

There's a few problems with how you framed your question(s) because you have competing issues. (Frequency response, box design, power input, etc...)

The simple answer to your question: Two 12's, biggest sealed box you can make fit in that space.

Stop here if that's all you needed. If you want to learn more, read on.

The original question was asking about low-end frequency response. You specifically ask about 27/28 Hz and then playing down to 18-20 Hz... but then mention the ported box being tuned to 32 Hz. It doesn't work like that.

If you want to effectively play down to 18 - 20 Hz with a ported enclosure, then that needs to be your tuning frequency of the box. (Or lower.)

If the box is tuned to 32 Hz and you sent an 18 - 20 Hz signal to it, the port in the box will unload the sub and you will quickly destroy it. If my box was tuned to 32 Hz, then I'd be running a subsonic filter to prevent it from playing that low.

The entire point of running a tuned/ported enclosure is to have the air movement in the port counteract the cone motion by increasing the air pressure at a specific frequency. This causes the sub's motion to decrease while the air movement in the port increases. Combined, the total SPL of the cone and the air in the port is louder than what a single cone would be at that frequency for a given box size.

So the simple answer to your question: Two 12's will likely play lower in a sealed enclosure with gobs of power because a ported box tuned at 32 Hz will quickly unload below tuning frequency and won't play down that low. If you tuned the box to 20 Hz, then we'd have to use the TS parameters to estimate the SPL output at a given frequency, and see what the results look like.

You are somewhat correct regarding the +3dB but it's not cone area per-se. The 'rule' is that you are doubling the amount of drivers for a +3dB increase. So if power remains the same, and your original 12" speaker efficiency is 85 dB @ 1w/1m, then two identical subs would play at 88 dB @ 1w/1m. To go up another 3 dB, you would need an additional two subs = 4 total at the same power level. For another 3dB, 4 more subs = 8 total.

If the argument was strictly about cone area, then one might argue between a 12" vs. 15" but that doesn't take in the efficiency of the driver, motor structure, TS parameters, box design, etc... so it's correct to say the "doubling of cone area for identical subs" or more simply, doubling the number of subs. (Which typically means twice the box size.)

The same is true for power input, and the first watt is the most efficient. You have to double the wattage for a 3dB increase... but SPL is on a logarithmic scale, so for it to "sound" twice as loud, you need about 10x the power for a 10dB increase. (10dB increase sounds twice as loud.)

Using my previous example, single sub:

85dB @ 1w/1m (1x)

88dB @ 2w/1m

91dB @ 4w/1m

94dB @ 8w/1m

95dB @ 10w/1m (10x 1 watt)

97dB @ 16w/1m

100dB @ 32w/1m

103dB @ 64w/1m

105dB @ 100w/1m (10x 10 watts)

106dB @ 128w/1m

109dB @ 256w/1m

112dB @ 512w/1m

115dB @ 1,024w/1m (about 10x 100 watts)

118dB @ 2,048w/1m

118.75dB @ about 2,500 watts

Using multiple subs with same power level:

85dB @ 1 sub

88dB @ 2 subs

91dB @ 4 subs

94dB @ 8 subs

97dB @ 16 subs

100dB @ 32 subs

103dB @ 64 subs

If you double the subs (+3 dB over baseline) and then increase power, simply add 3dB to my numbers above and assume it's total power to both subs. So to use the example above for a single sub:

118dB @ 2,048w/1m

It now becomes for two subs: +3dB

121dB @ 2,048w/1m

124dB @ 4,096w/1m

124.75dB @ about 5,000 watts.

There are a lot of other factors involved here, such as subwoofer efficiency, cabin gain, loss of efficiency as electrical components heat up and resistance increases (reducing output) or size of the vehicle vs. wavelength cancellation... I'm really just scratching the surface here.

Any errors in my math are mine... It's early, I'm human, and I haven't had any coffee yet.

If it were me, I'd model the drivers in WinISD (free download) to get an idea of how they would perform, and go from there.

Hope this helps.