Garage - IB with FI 18's and VAS equation - Question and advice

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Hi,
Garage conversation costings arriving with a projected completion date this year all being well. I would like to ensure I have the VAS equation correct and seek advice on which of the two options would be the preferred or optimal route .

My vas equation

Single Fi 18, 381 Litres
X 4 Fi 18’s = 1,524 or 54 Ft3

54ft3 X 10 = 540ft3 volume required for an IB

Is that correct ? On the current working that it is I have the following options for my IB garage build

1) IB with 2 x Fi 18s at @ 8- 10 X VAS volume
2) IB with 4 X Fi 18’s at @ 5 X VAS volume

I am not sure what the best route would be and the difference between the two options would be from a listening perspective .

Any help, thoughts or ideas would be appreciated . I’m completely new to this and have been working towards an IB build for a few years now…however if the two options are both equally as poor(?) I have the option to scrap the IB build and go down more traditional routes
 
It may be a crude way of doing it, but have you tried modelling both options in Winisd? You can create a sealed box with the VAS you have for each option and that should give you an idea.
Splitting into two manifolds with 2 dual opposed drivers in each is likely to yield a better in room response and be kinder to your garage too. :)
 
I had not thought of that option, a good shout thanks. I'll work them and see what the results are.

The manifolds are built as the 2 dual opposed drivers with my plans to bolt them to the ground - though I should decouple from the ground ?

its a shame to loose the 'space' of the IB within the garage but I'm keen to give it a go, as its unlikely I’ll have another chance to try an IB.
 
It may not be a bad idea to bolt them to solid ground, if you can.

My manifolds were initially just screwed to sit on the joists above the room, but despite of dual opposed configuration I was surprised to see how much the whole ceiling shook. I've now braced the joists to the rafters above them. It's better but I still have to reach for the remote on bass heavy scenes. It just shows how insanely capable those IB18s are.

I first heard of IBs when I was 15, and it took me another 20 years to scratch that itch last year, so I know where exactly you're coming from!
 
Managed to model the two options, im not great at using WinISD and had to find the driver specs on line to create them.


The smaller VAS with 4 drivers performance looks pretty solid and the (slight) added Db over 2 drivers could be handy. There was some charts that did not produce anything which made me wonder if I had error'd somewhere. I think the reduction in VAS will mean that the build is not a true IB but should be significantly improved over standard 'box' builds.

I can bolt them directly to the ground, they can be directly into the concreate floor -maybe a layer of insulation between the manifold and the actual floor.

Having two pairs should provide a decent bass response , though I have some concern about null zone and the limited options on MLP options-well rather the lack of options. And there is no replacement for displacement
. :D
 
Having two pairs should provide a decent bass response , though I have some concern about null zone and the limited options on MLP options-well rather the lack of options. And there is no replacement for displacement
. :D

Exactly, not that you need the extra drivers once you notice how little they move to generate all that bass, but you only live once!

There was also a decent discount on bulk quantity when I placed my order with BladeICE last year.
 
Looking at the design options , my VAS will be X 7.

@puneet83 i've realised that I will have a 'front' door on the IB wall.... This had not crossed my mind before... i've some concerns about the door vibrating in the frame . i can make the frame/join weather proof , do you think that along witha door dampening will be ok?
 
Yes, I would suggest using some weather proofing tape to eliminate any potential rattles. It's a cheap and quick fix.

As I mentioned earlier, I was surprised with the movement in the ceiling with two dual opposed manifolds. This would be an even bigger issue if you were to just use that wall as a baffle for the drivers as a larger portion of energy from the drivers will get absorbed by the wall, unless you brace the heck out of it!
 

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