I'm inFInitely Baffled.

[James Bang 5,000+ posts]

i used some 1/2" weather seal. you can kind of see it (white) on the top right of this pic between the sheet metal and baffle:

 

[req 5,000+ posts]

has to be a sealed back from the front. it cant just be a sub sitting on a piece of wood. think a ginormous sealed box.

in all actually - REAL infinite baffle is 10x the size of the recommended sealed enclosure. (ie: 10x vas)

thank you james. exactally what i meant.

 

[James Bang 5,000+ posts]

So, on my way to school, I tried placing a square piece of eggcrate foam on the center of my dash.... and it sounds better. the soundstage felt more centered and higher WTF. Now i have to find a way to integrate some acoustic foam w/ my dash. more thinking to do.

it was one of these:

i wonder if they make very thin versions of 'em so I can stuff it under the mat...

 

[Immacomputer 10+ year member]

in all actually - REAL infinite baffle is 10x the size of the recommended sealed enclosure. (ie: 10x vas)

Well, not really. That's more of the acceptable version of an infinite baffle system in a car.

Real infinite baffle has no loading on the front or the rear of the cone. There should not be any air-spring in either direction which means a baffle piece that extends for an infinite distance in all directions. Basically a system with the front wave and rear wave completely separated and where Qts = Qtc and Fs = Fc. Where Qtc is the total Q of the sub and enclosure system and Fc is the point of resonance for the sub and enclosure system.

 

[req 5,000+ posts]

a lot of the sound nulling performance from the foam has to do with the little protrusions of the foam, not actually being foam itself.

just thought id let you know //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

but comperman, 10x vas is an accepted PRACTICAL (in house) idea of infinite baffle, its not a rule that is set in stone, and yes - no loading on eaither side of the cone. but its impossible to have a "infinite baffle" that extends to infinity and has zero resonance.

so, 10x vas still works //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[Megalomaniac 5,000+ posts]

are you going to carpet that birch baffle?

 

[req 5,000+ posts]

i hope it covers it in vynl.

 

[JonJT 10+ year member]

has to be a sealed back from the front. it cant just be a sub sitting on a piece of wood. think a ginormous sealed box.
in all actually - REAL infinite baffle is 10x the size of the recommended sealed enclosure. (ie: 10x vas)

thank you james. exactally what i meant.

Its not 10x Vas, its when the Q of the alignment equals the Qts of the woofer. Some woofers don't 10x Vas airspace behind them to achieve this (for all practical purposes).

 

[James Bang 5,000+ posts]

I may step up to vinyl. carpet may be a lil dull. also, the carpet i have is not a perfect match to my factory carpet

 

[req 5,000+ posts]

Its not 10x Vas, its when the Q of the alignment equals the Qts of the woofer. Some woofers don't 10x Vas airspace behind them to achieve this (for all practical purposes).

yes, i understand this, but please explain how you measure that? //content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif

 

[Hintzyboy 5,000+ posts]

I just read through the whole thread and I just have to say wow.

On the whole IB thing. I may be getting a new car soon and may want to do something crazy with my current, beatup truck. Would it work if I made a sort of blow-through IB? Like cut a hole in the rear wall of the truck and the front wall of the bed, then seal a baffle to the cabin wall? That way, the front and back would be isolated, and the woofer would really have ininite space behind the baffle. I can't really get anything for the truck, so doing something crazy like this might actually happen lol.

 

[Immacomputer 10+ year member]

yes, i understand this, but please explain how you measure that? //content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif

Well, you can calculate it using limits but the only way to measure it would be to measure the Qts and Fs while it is in the setup.

You can calculate the box volume but it actually approaches infinity. You can see it by this equation solved for Vb:

If you take the limit as Qtc approaches Qts, you will see that the squared quantity comes closer and closer to 1. As it approaches 1, Vas is divided by an increasingly small number. This sends Vb to infinity. Thus, the limit of the box volume (Vb) as Qtc --> Qts equals infinity. So basically, you can never really have any infinite baffle environment.

In the second equation shown, you can see that as Qtc --> Qts, then the ratio of Qtc/Qts comes closer and closer to 1. That means that the resonance of the speaker in free-air (Fs) approaches the resonance of the enclosure/sub system. As we have already seen, as Qtc --> Qts, Vb goes to infinity so then Fc approaches Fs and as we can see from limits, Fc = Fs in a pure IB environment. To find out how close you are, you can plug and chug your numbers into those equations.

A simpler way would be to use winisd alpha and keep changing the Vb until Qtc = Qts and the Fc = Fs. 10x vas is widely accepted because of how close that those numbers get to each other; basically it gets to the point where you're not really worried about it and the percentage off that you're going to be will probably be less than the tolerance of the materials used as well as power compression and the change of T/S parameters.

 

[req 5,000+ posts]

well. in short - hell yes.

in long, you will have to find a way to isolate the rear end of the speaker from the elements. your best bet would be to get a wide W-like gasket, if you have seen any other blowthrough projects you will know what i am talking about, you put this between the wall of the cab and the wall of the bed to stop moisture ect from getting down between the bed and the cab onto the work area.

then you will have to build some kind of seal behind the speaker - id assume you could make a sort of sealed enclosure like a normal blowthrough and then put a nice thick layer of goretex over a 'port' on the back side of the box so that it is open to the environment - but closed to the elements. the only thing i would worry about is humidity.

the only practical way of doing said project would be having a taneau (sp?) cover over the bed i think.

/edit

computerman,

so how do i measure the volume of my trunk //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

i realize this is all possible on paper - but real life performance does not always reflect mathmatical calculations in the subwoofer world //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

i am not saying you are wrong, because this is not the case, im just saying ... well... i dont know what im saying //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

i just try to stay away from those kinds of calculations //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[Megalomaniac 5,000+ posts]

Are you using the same horns as james, req(andy?)?

 

[req 5,000+ posts]

kinda.

i have CD2 comps with mini horn bodies, iirc he has fullbodies and cd1 pros?

well. i guess not even close haha.