Speaker Guru's needed.... - Page 2

crazyray · 11-21-2002, 02:54 AM

Well, Out is partly right...

The "F" at the end is intended to indicate this sub is for "free air" use. This means it was designed to use the trunk of the car as the enclosure, a very large sealed enclosure. A free-air system consists of woofers mounted to a board attached to the rear deck or placed in the trunk against the rear seat. The trunk acts as the enclosure housing the subwoofer. Free-air systems save space and have flat frequency response. The woofer must be specifically designed for free-air use, and the trunk must be airtight for the best results.

http://www.crutchfield.com/S-lkKvEwX...p?i=130TSW254F

Placing these subs in a box, even one as large as the 1.5 cubic feet each that Out has suggested, will result in very boomy bass with poor extension (no deep bass).

OuTpaTienT · 11-21-2002, 03:51 AM

Well actually it's not me that's right or wrong, it would be that site I linked to. (If it were my information then it'd be completely wrong.)

Seems like a good site. And with all the other good info they give, it's too bad they're wrong about this. Hmmm. Go figure.

JayMan · 11-21-2002, 04:21 AM

Hmm.... ok then.... there is no way that i could easily do the "free-air" thing with my car tho....

Bah, i think i'll just leave it the way it is....

Altho its currently got no dampening material inside the thing, just a plain ol sealed enclosure.... Whats a good, cheap dampening material to use? I know we used to use old quilts/blankets in the bass drums @ skewl, would something like that do the job for this?

JayMan

JayMan

JayMan · 11-21-2002, 04:22 AM

Hmm would a ported box or sealed box be closer to the "free air" thing?

JayMan

crazyray · 11-21-2002, 07:13 AM

I'd suggest selling the subs on EBAY.

http://www.the12volt.com/caraudio/boxes1.asp

The closest you can get to the correct set-up is a LARGE sealed box. A ported box will not work with that model. (To give you an idea how large...they were intended for about 10 cu ft.)

In case you are interested, the spec that gives it away is Qts...these subs have a very high Qts (.765). The version intended for a small sealed box is a "low Q" design, usually .4 or lower.

If your car has a rear deck with openings for 6x9 speakers, a wood baffle can often be fabricated and the subs mounted to it so that they blow through the openings where the 6x9's would be. See the link provided above.

BTW, car audio is rife with more utter BS than any other area that I am familiar with. Many products are of poor quality and grossly overpriced. If you decide to buy something else I'd be glad to help you avoid some of the common traps. For now, there is nothing you can do with those subs that will give satisfactory results short of a free air (also called infinite baffle) setup. You should not have paid more than $60 each for those. For that $120 you can buy a single 12" Shiva, place it in a ~1.5 cu ft sealed box and kick the heck out of your friends' $300 subs. Really.

JayMan · 11-21-2002, 07:59 AM

Nah i aint gonna sell the subs. I don't have the time, nor $$$ patience to sell & buy new subs.

I'm happy with the way they are now, but was curious if it could be made better.

Anyways, we've already worked out that its not ideal having these in the enclosure, but anyways, would it be worth putting some dampening material inside or not?

JayMan

JayMan · 11-21-2002, 08:00 AM

BTW, i probably could mount them in the rear parcel tray, except for the fact cutting the metal there is illegal here in australia.

JayMan

dunbar · 11-21-2002, 08:52 AM

Proper enclosure porting can improve sound, certainly, because it allows the speaker to travel freely at lower frequencies, thus you'd think the opening helped the low end response. A speaker in a sealed box would have to pull on the sealed chamber, which will restrict the movement of the cone. BUT.... if the box was designed by some competent designer, the decision was made to use a sealed box with a certain driver (speaker). Opening a sealed box without considering the impact that opening will have on driver performance usually results in failures in the performance of the speaker and enclosure team. Xmax is a critical parameter here: Jayman posted the Xmax as '8' I'm assuming that is not 8 centimeters nor 8 inches but 8 millimeters. I would strongly advise against driving that 8 mm rated driver at more than maybe 20W input power if it is in any old (arbitrarily designed) open enclosure: the cone will travel easily to its maximum limit at lower drive levels, which means that higher drive levels beyond that 20W limit will possibly permanently damage the structure of the speaker (cone, basket, spider). Even if nothing permanent takes place, the banging of the cone against its mechanical limits would introduce mechanical harmonics into the cone vibration, where proper use would not have such problems.

OuTpaTienT · 11-21-2002, 09:30 AM

Now you're sorry you asked aren't you Jman? hehe.

To answer your question, I would say yes to the baffling. I don't know how much good baffling does in a woofer/subwoofer because it probably doesn't do much to stop the low frequencies, but it wouldn't hurt. Generally baffling is always a good AFAIK (there's obviously others here that know a hell of a lot more than I). When your speakers produce sound they are obviously producing pressure waves that are radiating from the cone to the listening environment. But the driver also produces pressure waves (sound) from the backside of the cone. And these waves you want to kill if possible. Baffling helps absorb that unwanted sound.

dunbar · 11-21-2002, 10:36 AM

Quote:

Originally posted by OuTpaTienT
But the driver also produces pressure waves (sound) from the backside of the cone. And these waves you want to kill if possible. Baffling helps absorb that unwanted sound.

Well, sorta. The reason you do not want them delivered to the ear is that the usual path to the ear will put the wave from the front of the cone alongside the wave from the back of the cone..... but those 2 waves are going in opposite directions and they would just eat each others energy before the wave ever reached your ear..... you would lose sound that way, so yes, you'd want to avoid unintentional wave cancellation. avoiding cancellation needs some design effort.

But for those who seek a real treat, investigate a folded horn..... that is a sort of port which redirects the rear wave in such a way that the 2 waves are joined to each other in proper phase, in effect doubling the energy which reaches your ear, compared to a sealed enclosure which, in essence, attenuates 100% of the rear wave!