Box fabrication question

samhain

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I have the parts express ultimax 18 CNC machined sub box. The outer pre-cut hole is a maximum of 18” 3/8th’s which is the perfect size for the ultimax speaker. A different speaker has caught my eye in the FI HT3 18 but it needs a hole of 18” and 4/8th’s. It’s a tiny bit bigger of 1/8th of an inch or 3.175mm.

How would you go about increasing the size of the outer hole so it’s perfect all the way round for a slightly bigger sub. It’s so close but 3mm means the sub won’t sit flush with the hole.

Would an even sanding with the hand all the way around the hole do it or is it more complicated?
 

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You could easily sand/file that small amount off but the neater way of doing it (if you care about that) is with a router and appropriate bit. Is the baffle designed to fit the UM18 recessed or flush mounted?

Edit: just noticed your picture :facepalm: If you mean that the recess for the driver is too small to seat the FI then the only way to open it out (without looking like a dogs dinner) would be with a router.
 
The actual hole for the body of the subwoofer to go through is big enough. It’s the flush mount edge that’s 3mm too small
 
A router with a rebater bit is the only way i can think of doing the job properly but more importantly, have you modelled the FI driver in that size enclosure?
 
Yes it a good match up, more output but takes/needs more power
 

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