Are two subwoofers really necessary?

I'm currently in the process of replacing the stock system in my 996. I was under the impression that a single subwoofer can handle the bass output for a decent system, but it seems that the majority of the speaker packages come paired. Is there a gain from running two subs instead of one?

In general no. One should be fine. Generally even when people have two they are enclosed and work together as one. I would listen to the sound and if it sounds good and gets as loud as you want I wouldn't worry about it.

I have one jl 10w3 and it is more than enough.

2 Subs are definitely not necessary, although in my 996 I had a custom box built with 2x 6" JL 6W0s put in and it sounded great and looked totally factory--I was told that any larger subs would require the rear seats to be taken out and a Sub mounted in the seat...I didn't want to do that so I went with the 6s. With an Amp and good speakers all around, it sounded really good, just if you listen to a lot of Rap it won't pick up the lows as well. In my VW and BMW, I had one 12" woofer and it was plenty...you certainly don't need 2 woofers, but if you are interested in doing what I did with the 6s, let me know and I can send you pics of the box [it is trimmed out to match a black interior car and the woofers you would put in it are down firing [so you can't see them from above]

It depends on the power and the particular woofer used. One good one and good power may be better than 4 cheap speakers and insufficent power. It may help to go to several stereo shops and get several ideas. Listen to different equipment.

Thanks for the info - I'll most likely be putting a single 12" in a truck box and laying it flat behind the rear seats.

I like this installation by Car Audio Innovations : More info here .

Can you show me the picture of the sub box you built with the two JLs in it? I'd like to make one myself. Thanks. - Phil

I have 3-6.5" woofers (JL's). No problem with the box fitting. WOOFER LINK Smaller woofers will have tighter response, but not as deep a sound. IMO, If you listen to rock/country go for 3 smaller woofers; if you listen to rap, go for one big one. As a point of reference - 1-12" woofer = 113 sq. in. of cone area, and one 10" woofer is 79 sq. in. Compare this to 3- 6.5" woofer which has100 sq in. of cone surface and 2-8" woofers which has 101 sq. in. You can see that the box size for one 12" 2-8" and 3-6.5" should be pretty close - and the total cone area will be as well. And, be sure to get speakers with the right impedance for a multi-speaker setup. Your amp will probably like a 4 ohm (or maybe 2 ohm) setup. So plan your purchase accordingly. -td

I've got 2 eclipse titanium 12's laying around my garage that aren't going in my car.........

It depends on the diameter of the cone, size of the coil and magnet. If they are sufficiently large with a clean strong amp, you can easily get adequate sound out of a single subwoofer. In the case of the factory Bose, they use a single woofer in the case of a Boxster, Cayman or 911 Cab due to space limitaions in the center floor. They use 2 speakers in the rear box on coupes due to the small size the area permits for the cones.

I have a Infinity basslink in my car, has tons of power and it is just a single 10" woofer with a 10" passive radiator (they are back-to-back). It comes with a built-in 200 watt RMS amp. Very small unit that fits behind the top of the rear seats and the rear deck of the car. About $350