Free air subs

[PhilMorrison]

Right I built myself a flush mount enclosure for my Cerwin Vega 12" sub, it sits behind the passanger rear wheel arch. I have now completely givin up on the idea of ever gettin round to making it a sealed enclosure, so my quessie's are, are free air subs any good? and what 12" free air can I get for much cheapness?
to speed the neccesity for a replacement I have also managed to blow my Cerwin Vega, despite it being a supposed 1200w capable sub:rolleyes: but thats another story :D

[Stevecarter200]

Free air subs can be good if installed properly on a very solid baffle board and powered by a suitable amp. By suitable amp I mean one that has the same (or more) power output as the sub is rated for.

I believe they are fairly rare now compared to sealed enclosure subs but I think Kenwood do one at under £100.
The amp has to be the same power rating as the sub because there is no support/damping for the sub like there is with boxed subs so the control of the sub (frequency and throw) is entirely down to the amp.

What power amp were you using to run this 1200W sub? Subs can blow if the amp is under powered as well as over powered. This happens because the amp doesnt have the power to control the movement of the sub properly so the amp is trying to move the sub as per the signal from the source but the sub, due to inertia, is lagging behind the signal all the time. So the speaker coil is trying to move the sub in one direction but the speaker is actually moving the opposite way which burns out the coil.

[inFOCUS]

Blimey, didn't know that, i thought i would be alright with me under powered amp till i had the cash to get a decent one.

Thats a good excuse to go out and get a goodun now:D

[p.nicholas]

i'm running a 12"alpine sub which can be used as free air or enclosed off a v12 amp(can be pricey though)

[Daniel san]

The important thing to remember is that power doesn't kill a speaker, but distortion certainly will. It's always best to use an amp with a higher output than the speakers manufacturer states it can handle, you're just not going to use it all. Think of it like this: A lovely 1ltr Festa can do 90mph, but your even lovelier 200 can do it so much easier and is less likely to conk out on you! Power in reserve you see.:)

[Daniel san]

Btw Phil, JL Audio still make their range of Infinite-baffle subs. IB8, IB10 and IB12's. They start at about £120 for the 8" I think.

http://www.jlaudio.com/subwoofers/ib4.html

[PhilMorrison]

Cheers guys, I was (and still will be running) a V12 thats aparantly around 400wRMS. The reason, I managed to blow it was because, using the steering columb control I swapped from radio to CD, and while the CD was spooling, I clicked the volume up, it jammed and went to maximum volume, then Method Man kicked in, say no more :rolleyes: :D

[Si T]

any damage to the boot?:D

mine`s going into SQ Plus tomorrow for my gear to be filtted plus two diamond 10 subs in a box he`s building ontop of the fuel tank, will post piccies as soon as:cool: :cool: :cool:

[Diddn]

Be careful about how much power you throw into a free air sub.
Free air subs do not rely on the air in a box to act as resistance against the cone, it relies solely on the spider/damper around the voice coil, and the speaker surround (be it rubber or foam).
Whereas you can safely use an amp which a rated far more than what the speaker can handle, its a completely different story when running a free air sub.
Some subs are suitable to be used either as boxed or free air. If you look at the recommended power for these subs in each application, you'll notice that when run free air, the power rating is halved (or less) as compared to when its boxed.
Just a safety warning.