what does this mean? it is written on the bottom of my sub on the magnetic part in big letters

FREE AIR USE / CHARGE LIBRE

does this mean it is a free air sub? that it can be used without a sub box enclosure around it?

basically yeah....build an MDF board that stretches across the back of ur seat...and TA DA....i have one and now im getting another one so i can keep my boot space

ive already built my box's but its handy to know for the future

Free air subs shouldn't be used in boxes and if they are they should be extremely large. Why did you purchase free air subs if you were going to be using boxes?

for starters mate, they were sold to me in box's, I didnt ask for free air ones, I hadnt even heard about them when I bought them and they say in the books that they sound best in a ported box

free air subs aren't meant to be in an enclosed box...but if its well ported it will work fine but with some restrictions. Since it is free air it seems to move more and requires more space to move the air around unlike enclosed subs which don't have as much excursion in comparison with free air of the same power rating. I think thats right...someone correct me if im wrong.

but it should be fine in a ported box...just don't pump it too much. might stress it out a bit

Free air subs have stiffer suspension due to not having the support of air suspension that a box would provide, so they have less output than their equivalent sealed version sub and require a huge box to sound how they should sound.

eb_guy... Did you buy them NEW in a box? Or second hand?

NEW

Free airs don't give less output because of the suspension stiffness, closed box speakers rely on the air pressure inside the box to provide the "stiffness" and control over the cones movement.
Generally free air speakers are more efficient then their sealed box cousins but generally don't handle as much power either. So a well setup freeair will go loud but require less power to do so than the small sealed variety which use a very heavy cone and loose suspension which requires much morepower to drive to generate the same volume level.
Obviously this is a generalisation and free air is very hard to do "properly" and free air drivers lend themselves well to a ported enclosure as well but not a small sealed enclosure.
Just remember there is no such thing as "free air" all drivers require an enclosure of some kind only the size and style changes!!!!!!

yeah but they say free air don't require a box because the box is so huge u might as well just use the boot.

set up is hard due to the fact that the positive sound wave of the front of the speaker cannot interact with the negative sound wave of the rear of the sub or else your sound will just cancel each other out if they do interact and u get s**t sound...so if its in a ported box it should be fine and if ur running it on the back of the seat you gotta make sure the whole wall is sealed properly so that the sound cannot cross over and cancel each other out....then again all this is also true for enclosed subs but are not that important since it its closed.

outlawxr6... My mistake. Just looked into it and most free air versions are about 1dB more efficient that their sealed equivalent.

phongus, you are right they do say the don't need a box and this is total bs as there is no woofers that can work in free air they all need some type of enclosure and if you think about it a small sealed enclosure and and a "free air" setup is differed only by the size of the enclosure say 20lt for the small sealed and 350lt for the free air.
You are right in what you say about sealing the front waves from the rear waves which is why I said about free air being difficult to do properly.


But!!!

If done properly free air can do something that small sealed generally won't do too well is to go lowwww, usually in a small sealed system the bottom end is very limited as this is a natural by-product of the box size as there was a graph aroud years ago done up by the same guys who gave us the Theile-Small parameters that we still use when working out box sizes and it sowed that frequency response is influenced by the enclosure size irrespective of the driver size. Now we have drivers that are meant for smaller enclosures and this is done by increasing cone weight and loosening the suspension and combining this with a small box it will work well, be nice and punchy but will roll off significantly in the lower octaves (which is fine for most music) much more notably than a good free air system (which is not normally as punchy).
Stone you are correct but some brands are even more noticable say 2-3dB and 3dB more efficient means the same output with half the power!!!

I forgot to mention also in a free air install anything in the boot affects the frequency response as it changes the box volume!!!!!

will putting a free air sub in a sealed box damage it or does it just impact the sound?

it won't do any damage i don't think but it will how ever restrict its capabilities. ported box will give u better sound then non ported....but yeah free-air should stick to LARGE boxes for them to work properly. mainly impacts the sounds since its restricted....not to sure if you would damage it...