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Discussion Starter · #1 ·
So, as I've been slowly mulling about with delusions of grandeur with what to do audio-wise with my car, I've begun to look in the direction of IB. Doing some reading and research, I haven't fully found information I was looking for. Maybe it's out there and I didn't look in the right places, maybe I overlooked it, or maybe it isn't out there.

Let's say I want to jump off the fence on the side of IB and go all-in. Let's say I've even settled on the brand, in this case Acoustic Elegance with their IBAU line. Now that that's out of the way, on to my question(s).

I have heard that for IB you want as much surface area as possible. Great! Let's look at (2) 15"s from AE for IB in my sedan trunk. How do I know my trunk is actually big enough to support twin 15"s in IB? This is where I was coming up short on info. Half of my Google searches were pointing me to home audio forums, which while still technically relevant, not helpful for car environment. I finally stumbled across a post where the poster said something to the effect of "you want your trunk volume to be larger than the speakers' Vas". Eureka! Finally some info I can research!

Looking at the specs of the AE IB15AU, it has a Vas of 387L. Convert that to cu-ft and I get about 13.7, or roughly 14 cu-ft. Each. So, if what that poster said is true, I need ~28-30 cu-ft of trunk space. Huh.

A quick tape measurement in my rear end points to about 19 cu-ft. Well, (2) 15"s are out. But, if I look at the AE IB12AU, it has a Vas of 160 L, converting to be 5.7, or roughly 6 cu-ft. Much more manageable to have (2) 12"s, again, if the above is true.

So, next up is... a single 15", or dual 12"s? Each 12", with Xmax of 18mm, should displace 251.8 cu-in of area, or just over 500 for the pair. The 15", on the other hand with it's Xmax of the same 18mm, should displace 393.4 cu-in of area. If my math is correct, the (2) 12"s have more displacement.

Now to the physical install portion. My rear seat does not fold down. The majority of the divider is a steel bulkhead. There is a ~10"H x 17"W pass-through when the rear arm rest is folded down. That's the only area for any appreciable sound to come through. The rear deck has (2) 8"s from the factory, but I'd remove those and seal off the upper deck. My thought is to create a "V" shape for the (2) 12"s to mount to, with the opening of the "V" attached to the pass-through. I really don't want to cut giant slots and reinforce the rear deck to hang subs from, as that's more work than I want to do.

So, first, sorry for the long read, but if you've made it this far, thanks for following along. Does any of this make sense? Am I off-base? On the right track?

Thanks in advance for any input from those of you well-versed in IB language.
 

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If you use identical drivers and they both receive the same signal they can share the same airspace... so as long as you don't try to feed a left stereo signal to one sub and a right stereo signal to the other, you should be fine with two AE 15's.
 

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So, as I've been slowly mulling about with delusions of grandeur with what to do audio-wise with my car, I've begun to look in the direction of IB. Doing some reading and research, I haven't fully found information I was looking for. Maybe it's out there and I didn't look in the right places, maybe I overlooked it, or maybe it isn't out there.



Let's say I want to jump off the fence on the side of IB and go all-in. Let's say I've even settled on the brand, in this case Acoustic Elegance with their IBAU line. Now that that's out of the way, on to my question(s).



I have heard that for IB you want as much surface area as possible. Great! Let's look at (2) 15"s from AE for IB in my sedan trunk. How do I know my trunk is actually big enough to support twin 15"s in IB? This is where I was coming up short on info. Half of my Google searches were pointing me to home audio forums, which while still technically relevant, not helpful for car environment. I finally stumbled across a post where the poster said something to the effect of "you want your trunk volume to be larger than the speakers' Vas". Eureka! Finally some info I can research!



Looking at the specs of the AE IB15AU, it has a Vas of 387L. Convert that to cu-ft and I get about 13.7, or roughly 14 cu-ft. Each. So, if what that poster said is true, I need ~28-30 cu-ft of trunk space. Huh.



A quick tape measurement in my rear end points to about 19 cu-ft. Well, (2) 15"s are out. But, if I look at the AE IB12AU, it has a Vas of 160 L, converting to be 5.7, or roughly 6 cu-ft. Much more manageable to have (2) 12"s, again, if the above is true.



So, next up is... a single 15", or dual 12"s? Each 12", with Xmax of 18mm, should displace 251.8 cu-in of area, or just over 500 for the pair. The 15", on the other hand with it's Xmax of the same 18mm, should displace 393.4 cu-in of area. If my math is correct, the (2) 12"s have more displacement.



Now to the physical install portion. My rear seat does not fold down. The majority of the divider is a steel bulkhead. There is a ~10"H x 17"W pass-through when the rear arm rest is folded down. That's the only area for any appreciable sound to come through. The rear deck has (2) 8"s from the factory, but I'd remove those and seal off the upper deck. My thought is to create a "V" shape for the (2) 12"s to mount to, with the opening of the "V" attached to the pass-through. I really don't want to cut giant slots and reinforce the rear deck to hang subs from, as that's more work than I want to do.



So, first, sorry for the long read, but if you've made it this far, thanks for following along. Does any of this make sense? Am I off-base? On the right track?



Thanks in advance for any input from those of you well-versed in IB language.
According to the specs, they should work fine in less than Vas equivalent airspace. 0.62 Qts is lower that the ideal of 0.707 so there is some cushion there. I don't know the formula to figure that out, but someone around here does. I say go with the 15's.
 
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If I'm reading it correctly, you're basically building a manifold which will have some vibration reducing properties. That's a good thing!

As far as Vas and the space of your trunk, people really shouldn't get hung up on whether it meets the home audio criteria of what's considered IB. As long as the modeled Qtc isn't raised to an undesirable level, performance will still be good. Remember, we have cabin gain which will boost the bottom end, so that must be taken into account

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Overthinking it. Make baffle slap those 2 AE 15s in and power them up. It will be far superior to anything you have ever had or heard.
 

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Box modeling suggests 44.88 cubic feet for two of those 15's for a Qtc of 0.707. That seems really huge but I can assure you that there are people currently running 2 IB 15's in trunks just like yours, with excellent results.
 

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Discussion Starter · #7 ·
...I say go with the 15's.
...Make baffle slap those 2 AE 15s in and power them up...
Thanks for the replies so far! Do you see any concern trying to force the output of the 15"s through an opening that's only 17" wide and 10" high? Couple of images, one of my trunk with my old-school Soundstream SS10R, and one I snagged from the web.



My thought would be to have the subs mounted vertically in a "V" shape firing through that opening. But, is that opening too small for (2) 15"s?
 

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Thanks for the replies so far! Do you see any concern trying to force the output of the 15"s through an opening that's only 17" wide and 10" high? Couple of images, one of my trunk with my old-school Soundstream SS10R, and one I snagged from the web.







My thought would be to have the subs mounted vertically in a "V" shape firing through that opening. But, is that opening too small for (2) 15"s?
Nope, looks just fine to me. Regarding the airspace, you need to remember that there is a lot of airspace hiding behind trim panels and there's most likely one or more vents to the outside.
 
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This is interesting...I read about and was considering a IB Manifold setup for my home AV with pairs of AE 18's in Manifolds!! For various reasons I have not done that yet.

For my car, I have a single 15" mounted IB against the Ski-Pass. I was thinking about how I could get a little more out of it and this Manifold idea seems great!

I can get another 15" and do that or maybe 2 18"AE and bolt that puppy up to the back seat! :D
 

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This is interesting...I read about and was considering a IB Manifold setup for my home AV with pairs of AE 18's in Manifolds!! For various reasons I have not done that yet.

For my car, I have a single 15" mounted IB against the Ski-Pass. I was thinking about how I could get a little more out of it and this Manifold idea seems great!

I can get another 15" and do that or maybe 2 18"AE and bolt that puppy up to the back seat! :D
I'm intrigued. Mounted in attic? Basement?
 

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I love my IB and I won't go back !
2 OnCore XW15"


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Infinite baffle is fun but if your seats don't fold down and they're steel and reinforced. I would highly suggest you don't try IB. A single small "hole" like a ski pass might act like a port.

The sealed side being the trunk and front side being the area between the sub front and the ski pass. The ski pass being the port.

It might work. It might not. Just be aware.


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Thanks for the replies so far! Do you see any concern trying to force the output of the 15"s through an opening that's only 17" wide and 10" high? Couple of images, one of my trunk with my old-school Soundstream SS10R, and one I snagged from the web.



My thought would be to have the subs mounted vertically in a "V" shape firing through that opening. But, is that opening too small for (2) 15"s?
Mmmm.... Holden.... Nice!
 

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Discussion Starter · #18 ·
Infinite baffle is fun but if your seats don't fold down and they're steel and reinforced. I would highly suggest you don't try IB. A single small "hole" like a ski pass might act like a port.

The sealed side being the trunk and front side being the area between the sub front and the ski pass. The ski pass being the port.

It might work. It might not. Just be aware.


Sent from my XT1710-02 using Tapatalk
Thanks for the heads-up. My other option, that I don't *want* to do (but isn't off the table), is to cut large slots in the rear deck and fab enclosures to hang 15"s in each one, but they'd have to be at an angle, as my rear deck isn't large enough to hold a 15" flat. Hell, I'd be lucky to fit a single 12" in the middle. See attached for yet another quick stick figure drawing.
 

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Discussion Starter · #20 ·
Mmmm.... Holden.... Nice!
Yup, to me the bowties just don't look right on the Chevy SS', so I did some of the badge conversion. Front and rear emblems, center caps, airbag, plus the trunk mat, and when I mount them the cargo racks have Holden logos on the key hole covers. Still want to do new stainless Holden logo door sill plates, and reflash my radio and DIC to swap from bowtie and blue to Holden and red. Need to disassemble the dash and sent components out to do that, though.
 
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