Questions on Free Air Subs

Anyone done or has be thinking of putting an 8" free air sub on the rear deck were the cut out is? Opinions?

Hey F1, I haven't installed a free-air (aka infinite baffle) sub in the new LGTs, however I have installed them in numerous other makes/models.

 

A typical sub has an enclosure to separate the front wave of the sub from the back waves, so its construction can be such that it utilizes the pressure generated in the enclosure to provide the pressure being forced out by the cone's movement (ie the bass that you hear and feel). FA subs, on the other hand, are designed with more rigid cones and tighter suspensions in order to compensate for the lack of "tuned" enclosure. If you were to just lay a sub on the floor and wire it up, no bass would be produced b/c the front and rear waves would just cancel each other out (similar to an A/C unit needing one side in, to cool, and one side out, to reject heat). So....A baffle is needed.

 

The most important thing to consider in installing a FA sub is that the baffle is "infinite", meaning that the panel that separates the front of the sub from the back (rear deck in this case) is rigid and free of any holes. This will effectively create an enclosure out of the trunk itself, obviously its never perfect as the trunk is not perfectly sealed from the passenger cabin.

 

All that said, a properly installed FA will provide slightly enhanced midbass response as well as audible frequencies in the lower register of the spectrum that the interior speaker simply can't produce. This is contingent on sufficient power and x-over settings of course.

 

FA subs will generally sound "looser" and a bit "duller" than a traditional enclosed driver. If your goal is to just round out the sound, then a FA sub will do the job, if you're looking to "boom" or feel the bass, you'd probably be left wanting.

 

A good FA sub in tandem with a factory sub will give you a sound similar to say a high-end Bose factory system with respect to the <300Hz range of the spectrum.

 

 

 

Simple terms: FA will sound nice for simple bass enhancement and accurate reproduction, but will not provide the strong reponse of an enclosed sub. Also, it allows for a little something extra without the loss of trunk space.

 

 

Hope that helps.......

Thanks for the info CSTMIZR.

 

My purpose is to generate full range of sound without the added weight of an enclosure. Not looking for the big boom. Here is my current setup:

 

4 - Arc Audio comp 6.5 speakers in the doors.

1 - 60X4 amp under the seat.

 

All 4 doors are covered with polyfoam dampening to create door enclosures, which makes a big difference in mid/bass.

http://www.imagestation.com/picture/sraid225/p28060952ff5501dfcdb04b4939c52e8b/e842f074.jpg

 

Plus I want to keep the same amp and bridge it off the rear channels to save weight and space. So based on your experience, you think I could get the results I need out of an 8" FA sub?

Well, I think you will get a reasonable increase if you deaden the rear deck and be sure to pay attention to all areas where the trunk and passanger cabin air volumes might connect. As for bridging the rear channels of that amp, you would then have to series wire your front and rear speakers to the front channels, or run the rears off of the head unit. Either scenario will produce diminished output from the interiors, so I would probably recommend purchasing a small amp for the sub (w/ built in x-over, 100watts mono) in order to isolate the sub and maintain the benefits of each interior comp set having its own channel on the amp.

 

The small sub amp might weigh like 5 pounds (at most) and can be mounted in the spare tire area. So, I say leave your current setup as it is, get a small amp and put in the 8" FA (get a good one if you can). This set up (tuned properly) should give you a subtle, yet rich, overall sound.

 

Let me know what you decide.

Right, the best way would be to purchase a smaller amp, which means additional wiring to the amp with the extra cost. And then again it depends on the FA sub that I could find, if the sub requires more watts than my amp can produce then I may go that route.

 

I'll have to play around with the 4 speakers being wired to 2 channels, and see how it sounds.

 

Thanks for the advice!

Anytime bro.

 

I'm interested to see how it works out and if you're satisfied with it, as I'm sure others here would be too. I believe you would be the first to do it, so take some pics and post a thread on the results if you get the time.

 

Good Luck!

I'll keep you posted as soon as I figure which sub to purchase.

if you do a search, other people have talked about this, and i know at least one has tried it. i was thinking about it, but decided to go another path. there is one or two people on here that make a really nice custom fiberglass enclosure, carpeted, that fits in that indent on the left and/or right side of the trunk, just behind the tail lights. they have ~ 1.0 cu feet off air, most people put a 10 in them. thats what i would get, but still tryin to find the $$. good luck though