How much air space do I need for an FI IB3 subwoofer ?

[rr14]

Hi all,
I have a boat with a jl audio 12" infinite baffle subwoofer installed in my boat. The boat is a cat with a mid cabin and front bow seating. The JL woofer is firing into the mid cabin via double layer mdf setup with the air space under the front bow seats which is the left pontoon(not sure if that's the right terminology as I'm newer to boats).

My JL says it needs over 3 cu ft. With the fi ib woofer, it doesn't really say how much space they need(unless I missed that). I'd guess the more the better, but how much it too little for music only? I have a 500 watt jl m series amp. I'm thinking of at least going up to the 15" if not the 18" to get as much as I can out of one woofer and 500 watts.

[ThomasW]

The Fi IB3 drivers aren't intended for use in small sealed boxes.

This forum is for large structurally integrated infinite baffle subs for HT use, not small sealed boxes. Your best bet is to go to a one of the car audio forums, they'll have the answers you're looking for.....

[rr14]

Dec 6, 2020 10:11:10 GMT -7 ThomasW said:

The Fi IB3 drivers aren't intended for use in small sealed boxes.

This forum is for large structurally integrated infinite baffle subs for HT use, not small sealed boxes. Your best bet is to go to a one of the car audio forums, they'll have the answers you're looking for.....

I'm currently using a jl audio infinite baffle woofer in the setup currently. It is not a sealed box. It is infinite baffle setup where I am using a pontoon style long storage area as the speaker box.

Is there a formula or way to figure out approximately how much airspace I should have behind this(minimum). I could approach the car audio guys and they'll say "I don't know, that's a HT sub". Thanks!

[ThomasW]

The Adire Shiva White paper talks about an IB sub
being 4 times Vas, and says that's where Qts = Qtc.

If we run the numbers to calculate the closest
reasonable box volume where Qts = Qtc, we need to increase the box size to 25
times Vas. With a box volume 25 times the Vas, then the Qts and Fs will be
raised only by a factor of 1.02.  One can safely say at this point Qts =
Qtc.

Now a volume of 25 times Vas is impractical for
most people's installations, as a compromise we use 10 times Vas as our
baseline.....

Note that the 10 times Vas although recommended
isn't etched in stone. Why?  Well even the smaller 4 times Vas volume IB,
will have better SQ as compared to a standard small sealed box. This is a
function of there being less 'box' induced colorations

[rr14]

Dec 11, 2020 20:33:44 GMT -7 ThomasW said:

The Adire Shiva White paper talks about an IB sub
being 4 times Vas, and says that's where Qts = Qtc.

If we run the numbers to calculate the closest
reasonable box volume where Qts = Qtc, we need to increase the box size to 25
times Vas. With a box volume 25 times the Vas, then the Qts and Fs will be
raised only by a factor of 1.02.  One can safely say at this point Qts =
Qtc.

Now a volume of 25 times Vas is impractical for
most people's installations, as a compromise we use 10 times Vas as our
baseline.....

Note that the 10 times Vas although recommended
isn't etched in stone. Why?  Well even the smaller 4 times Vas volume IB,
will have better SQ as compared to a standard small sealed box. This is a
function of there being less 'box' induced colorations

Thanks! That is the info I was digging for. It’s been at least 5 years since I read it and couldn’t figure out where it was!