ya'll need an equalizer for the subwoofer.
my room is 12ft x 13ft and i have two twelves that can thunder the room.. but i have used the equalizer to bring up the 20hz area and lower some of the 30hz area and lower much of the 60hz area.
if you run out and get a high powered subwoofer, you will probably see lots of high frequencies (40hz - 80hz) with only half as much at 20hz - 30hz (maybe less)
trust me.. you dont want a subwoofer that plays 40hz - 80hz too loud.
you will always turn it down because its loud enough to get you into trouble, but never turned up high enough to play some REAL subwoofer bass.
one good example:
you buy a new subwoofer and dont have any way to adjust the different frequencies.
now you listen to some rock music and the kick drum from the drum set is way too loud.
but you leave it way too loud because you want to hear the lower bass from bass guitars and/or special effects from movies or digital audio.
you'll be screaming the high frequencies so you can hear the lowest bass notes.
most subwoofers have a bass boost, but the frequency is centered too high (and the width is way too wide because it will bring up the 40hz area)
i'm not talking about comparing the quality of a setup to formula 1 race cars.
but you see lots of four cylinder vehicles with turbos and superchargers.
as usual.. you either buy a car and make it go faster, or you buy a new engine or performance parts to make it provide more power.
generally, if you want a fast car, you are met with a challenge.
comparing a subwoofer to formula 1 race cars would depend on the quality of the speaker and the quality of the amplifier.
buying a subwoofer can be compared to buying a car.
there are lots of people making the purchase.. but there are loads of people who arent buying anything for the car.
no sticker in the window
no front seat covers
no new rims
it remains stock and they are trying to race with 'em.
i know this isnt entirely appropriate, but people buy a car to travel faster than walking or riding a bicycle.
so if you are gonna go faster, might as well enjoy it while there isnt a speed limit.
a subwoofer can be too loud, but turning down frequencies of 40hz - 80hz can really allow you to turn up the subwoofer extra.
i mean.. turn down frequencies of 40hz - 80hz and leave 20hz - 30hz the same.. then raise the volume until 40hz - 80hz sounds like it did before you turned those frequencies down.
you should be pleasently suprised.
a lot can happen when you purchase a 'home theater in a box'
one complaint may be, the subwoofer doesnt play low enough.
but one huge compromise is a subwoofer that doesnt play very loud, but it plays very low.
see.. two twelve's with 100 watts each is enough for a 12ft x 13ft room
but that means one twelve will need 200 watts and a proper box size and port length.
less power will require you to turn the amplifier all most all of the way up and it will have to stay there if you want to match vocals of the reference 75dB
you can always use less power if you have a the right speaker box.
perhaps you need to read car audio forums, because they go fanatic about building the right box with the perfect port size/length.
some people tune the box at 40hz to play extra loud 40hz tones to win the loudest car contest.
other people tune the box at 30hz to get low.
and some people tune the box lower than 30hz to keep the subwoofer from moving in and out violently when playing the bottom of the audible frequency range.
cd's and dvd's and bluray discs have a frequency response of at least 20hz - 20,000hz
there is no reason why your speakers shouldnt play each one of those frequencies.
people who dont like large amounts of bass dont like subwoofers because they usually play too loud.
and the only way to turn it down and play low, you have to use the right speaker box size with the right port size/length.
just like some cars get the best miles per gallon at a specific mile per hour (and RPM)
subwoofers get their best output per watt at a specific frequency.. and that frequency is dependant on the box size and port.
mufflers are all about sound.. and if you cut the muffler off, the exhaust isnt really loud until you rev up the engine.
a subwoofer in a small box will play 50hz - 80hz really loud
the bigger the box, the less loud that frequency range will be.
this isnt 100% true though, because the speaker can be unique and might consider 50hz - 80hz as 'ugly' and wont play those frequencies.
but the same can be said about 30hz
if the subwoofer finds that frequency 'ugly' it wont play it without putting up a fight.
the speaker doesnt play very low.. but its not always because the speaker cant play that low, its because the box is the wrong size.
if you care to experiment.. get some wood from the garbage.
people throw away old drawers and computer desks and entertainment centers all the time.
a bigger box and longer port will allow the speaker play lower.
a ported box works just like a flute or clarinet or saxophone.
if you change the holes that the air blows out, you change the size of the air chamber and the tone changes.
dont let an extra loud kick drum ruin your subwoofer experience.
its like having a car with no muffler and you dont want to drive anywhere because its too loud.
**edit**
my main speakers play 38hz effortlessly.. so why would i purchase a subwoofer that says it can only go down to 38hz ?
the purpose of getting a subwoofer is to extend the frequency reponse.
i see the 12 inch version has sold out.
it has 173 five star reviews.
if you want movie explosions.. that can go as deep as 18hz
when the specifications are at 38hz .. the speaker cone will probably move in and out a lot, but you wont have much output.
the reality is, if you force that speaker to play much lower than it is intended.. you will probably make the speaker smack the magnet before you are happy with the output.
the box 'tune' is supposed to help the output like a turbo helps a car go faster.
this website will help you determine what the box is tuned at:
http/www.the12volt.com/caraudio/boxcalcs.asp
you can take the outside measurements and input them into the calculator.
then input the port size (how big around) and how long the port is + the size of the box = rough estimate of the 'tune'
this website also has a calculator.. but has some information to help you realize why the calculator is important:
http/www.bcae1.com/spboxnew2.htm