Can someone school me in "free air" subs?
02-04-04, 01:57 AM
#2
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You can either use a woofer made for freeair. Which only a few brands still make. Or you can use almost any sub with a freeair enclosure. But you can only run half the power recommended for the woofer. There's no need for ports when doing a freeair enclosure.
02-04-04, 07:37 PM
#4
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Free air enclosure? WTF are you talking about?
When used freeair, there is no set power to give a sub intended to be used in an enclosure. Half the recommended power may very well be enough to damage the driver. For IB use, you want an overdamped driver (high Qts) for the best frequency response possible. A subwoofer taken out of a small or ported enclosure will most likely not be ideal at all and will probably begin rolling off before the lowpass point if used in a freeair environment.
When used freeair, there is no set power to give a sub intended to be used in an enclosure. Half the recommended power may very well be enough to damage the driver. For IB use, you want an overdamped driver (high Qts) for the best frequency response possible. A subwoofer taken out of a small or ported enclosure will most likely not be ideal at all and will probably begin rolling off before the lowpass point if used in a freeair environment.
02-05-04, 01:58 AM
#5
okay... what if i use the entire trunk as an enclosure and have 2 bass ports opening into the cabin from the deck?
the sub was taken from a pretty big enclosure (i would say just a bit smaller than the size of the trunk of the SC) of course that particular box had all kinds of channels inside it (looked like a maze) but it was pretty big none-the-less...
would this be feasible? Or should i just start looking for a free air sub?
the sub was taken from a pretty big enclosure (i would say just a bit smaller than the size of the trunk of the SC) of course that particular box had all kinds of channels inside it (looked like a maze) but it was pretty big none-the-less...
would this be feasible? Or should i just start looking for a free air sub?
02-05-04, 02:54 AM
#7
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Could you just tell us the make and model so as to eliminate speculation. If you don't know, post a picture and I'm sure one of us will figure it out. It sounds like it was in a ported enclosure, which means if it was designed with a ported enclosure in mind, there's a good chance it won't perform well IB...
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02-05-04, 08:04 AM
#8
If I can just reply to your request for more info about free-air subs...and to elaborate so that you understand what GaryDell is saying:
First, a speaker enclosure is meant to isolate the rear-firing wave from the front-firing wave of the speaker driver. A non-free-air sub is meant to be used in an enclosure that is nominally a specific volume, plus or minus a bit, that is designed to work with the driver's parameters and provide the proper damping of the speaker suspension, and allow for the best possible frequency response for that particular driver. In contrast, for a free-air, or infinite-baffle (IB) driver, there is no rigid enclosure. In a car environment, the trunk acts as the enclosure and separates the rear wave from the front wave. Due to the large trunk air volume, as compared to a smaller box enclosure, there isn't much damping of the driver's motion by changes in pressure of the air inside the trunk as the cone moves back and forth. Consequently, a driver that is normally meant to be used in an enclosure will flop around loosely and will tend to be overpowered with the same amount of power that would be used if it were in an enclosure, since it is underdamped. Needless to say, the speaker will distort easily and sound like garbage, and because of the lack of control of the cone's motion, the suspension can be easily damaged or the voice coil fried. A free-air or IB speaker will be designed to have more suspension control with no back pressure on it (from the lack of an enclosure). and will typically handle less power, just to keep things manageable and cost effective. However, there are some larger, beefier woofers that can also be used in free-air applications.
"Free air enclosure?"
Just gotta love that. I guess he meant with no enclosure.
First, a speaker enclosure is meant to isolate the rear-firing wave from the front-firing wave of the speaker driver. A non-free-air sub is meant to be used in an enclosure that is nominally a specific volume, plus or minus a bit, that is designed to work with the driver's parameters and provide the proper damping of the speaker suspension, and allow for the best possible frequency response for that particular driver. In contrast, for a free-air, or infinite-baffle (IB) driver, there is no rigid enclosure. In a car environment, the trunk acts as the enclosure and separates the rear wave from the front wave. Due to the large trunk air volume, as compared to a smaller box enclosure, there isn't much damping of the driver's motion by changes in pressure of the air inside the trunk as the cone moves back and forth. Consequently, a driver that is normally meant to be used in an enclosure will flop around loosely and will tend to be overpowered with the same amount of power that would be used if it were in an enclosure, since it is underdamped. Needless to say, the speaker will distort easily and sound like garbage, and because of the lack of control of the cone's motion, the suspension can be easily damaged or the voice coil fried. A free-air or IB speaker will be designed to have more suspension control with no back pressure on it (from the lack of an enclosure). and will typically handle less power, just to keep things manageable and cost effective. However, there are some larger, beefier woofers that can also be used in free-air applications.
"Free air enclosure?"
Just gotta love that. I guess he meant with no enclosure.
02-05-04, 11:08 AM
#9
tsw-w28c or something ike that.... (the sub is still at my friend's house) but we researched it last night... and it was listed under the "component" subwoofer category so...
okay i understand free air subs now
so what about my "using the trunk as an enclosure with ports" idea?
okay i understand free air subs now
so what about my "using the trunk as an enclosure with ports" idea?
02-05-04, 12:42 PM
#11
Trunk is too big to actually be an effective enclosure for non-IB woofers. Speaker's Thiele-Small parameters dictate the size of the enclosure. For sound quality, the metal car parts make poor enclosure walls, which ideally should be rigid and not prone to vibration.
Try punching the air by extending your arm in free air and trying to control where your arm winds up at the endpoint of its travel. (Disclaimer: make sure no one is nearby...) Very different than if you actually hit something, even something soft like a pillow. Weak analogy, but you get the idea. That's like what happens to a speaker that is underdamped. You need a speaker with very tight, controlled movement of the suspension, or you need an enclosure, if you plan on juicing the thing with any kind of power at all.
Try punching the air by extending your arm in free air and trying to control where your arm winds up at the endpoint of its travel. (Disclaimer: make sure no one is nearby...) Very different than if you actually hit something, even something soft like a pillow. Weak analogy, but you get the idea. That's like what happens to a speaker that is underdamped. You need a speaker with very tight, controlled movement of the suspension, or you need an enclosure, if you plan on juicing the thing with any kind of power at all.
02-20-04, 10:11 AM
#13
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engin_ear,
since it is obvious that you are an audio expert, i need your help in diagnosing my problem. my mark levinson sub seems to be rattling quite alot (usually at lower bass points). it seems that the bass is produced pretty clear but there is a rattle that is accompanied with it. i checked to see if anything is loose or if the cone had a tear but could not find anything. so, my question is "how do i verify if my speaker is "blown" and if it is, what should i replace it with? i noticed a lot of people have been discussing infinite baffle subs and from your explanation, i have a decent understanding of them. so, if my sub is damaged, should i get another ml sub or should i get an aftermarket ib sub? thanks in advance.
since it is obvious that you are an audio expert, i need your help in diagnosing my problem. my mark levinson sub seems to be rattling quite alot (usually at lower bass points). it seems that the bass is produced pretty clear but there is a rattle that is accompanied with it. i checked to see if anything is loose or if the cone had a tear but could not find anything. so, my question is "how do i verify if my speaker is "blown" and if it is, what should i replace it with? i noticed a lot of people have been discussing infinite baffle subs and from your explanation, i have a decent understanding of them. so, if my sub is damaged, should i get another ml sub or should i get an aftermarket ib sub? thanks in advance.
