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Enlarging a speaker mounting hole.

Discussion in 'Amps and Cabs [BG]' started by kurosawa, Aug 27, 2012.

  1. I need to open up a speaker mounting hole in a 3/4" thick plywood baffle, from 13 7/8" to 14" in dia. That would be taking just 1/16" off all the way around the circle. What's the cleanest way to do this? The plywood is very splintery.
  2. Hi.

    A router. Without a doubt.

  3. Hopkins

    Hopkins Supporting Member Commercial User

    Nov 17, 2010
    Houston Tx
    Owner/Builder @Hopkins Guitars

    You will need a template and a pattern bit.
  4. seamonkey


    Aug 6, 2004
    A 1/16" piloted rabbet bit, followed by a flush trim bit.

    Or x brace a half lap and use a circle cutting jig to re-cut the hole.
  5. experimental bassist

    experimental bassist

    Mar 15, 2009
    Well, I've done this quite a few times, making an older cabinet accept a modern front loading driver by opening the baffle mounting hole a little bit.

    No doubt templates and jigs would be great, but I just took a die grinder with a flapper wheel and went around the hole evenly until it was big enough for the speaker basket to drop in.

    Easy enough to do.

    Good luck.
  6. Is the baffle flush or recessed?

    Assuming a flush baffle, use a Jasper jig and router.
    Screw a piece of scrap stock diagonally on the inside between two opposing speaker mount holes.
    Draw scribe lines between two pair at 90-degrees to find the center point.
    Drill a 1/8" hole at the center point for the Jasper jig.
    Using a 1/4" up-twist bit in the router, enlarge the hole to 14".

    If you have a recessed baffle, this could still be done, but a much longer 1/4" cutting bit is required.
    You will have to create a plane-parallel platform for the router to ride on.
    A 1/8" drill bit is long enough to center the Jasper jig.
  7. Recessed. And, failing to recognize any of the terminology, I can see I'm not in Kansas any more.
  8. otherclef


    Aug 10, 2011
    Since its only a 16th...if you dont have any power tools. your easiest and cheapest all around way would be to go and get some coarse sending blocks and evenly apply elbow grease until you get where you need to be.
    Should take no more than 15 mins.
  9. Stumbo

    Stumbo Wherever you go, there you are. Supporting Member Commercial User

    Feb 11, 2008
    Cali Intergalactic Mind Space - always on the edge
    Song Surgeon slow downer software- full 4 hour demo
  10. Elbow grease is always the last resort.
    Working exclusively in baltic birch, I find hand sanding time consuming and tedious.
    Especially taking down 3/4" material.

    A Dremel tool with sanding drum might make this easier, but certainly more prone to "oops".
    Be sure to wear a face mask, especially if the baffle is particle board.
    A portable box fan to blow the dust away is a plus.

    Be sure to draw a precise circle at the expanded size so you do not remove too much material.
  11. OK, thanks, I'll make a little jig to draw the larger circle by dragging it around the ID.
  12. If you use the scrap method I outlined above, this will find the center point for you.
    Create your jig with a center point, then locate the jig on the scrap center point.
  13. Because I own no router, maybe I would be as well off drawing a line 1/16" outside the hole using the existing hole as a reference, then use a rasp to reach it. I only wish I hadn't impatiently lined the cab before taking delivery of the speaker and finding the problem.
  14. Considering the mess, it would be faster to remove the lining first.
    The amount of cleanup time getting chunks and dust out of the lining is a lot more than just taking it out.

    Draw whatever guide works for you.
    A rasp will do the job just fine.
    Speaker holes do not have to be anywhere precise, as long as they don't leak.
  15. will33


    May 22, 2006
    I do a lot of this type of trimming stuff just freehand, but you gotta have a steady hand, preferably 2 steady hands, or you could easily make a mess of things. A rasp as mentioned, preferrably one with a rounded edge, looks kinda like a halfmoon from the end, would get it done pretty neatly without too many sore muscles. Handtools also eliminated the "one slip/major problem" of going the powertool way.
  16. JLS


    Sep 12, 2008
    Emeryville, Ca
    I setup & repair guitars & basses
    I'd go with a rasp, too. You probably won't have to take the full 1/8" off the 3/4" dimension, if you're lucky. Tilt the rasp.
  17. Thanks! Will do all. Ordered hurricane nuts, larger dia. 10-32 x 1.25" cap screws, washers. Screws are threaded all the way up to the head.
  18. SBsoundguy


    Sep 2, 2011
    Los Angeles
    Router, Dremel, or possibly a rotozip (go easy on the bit).
  19. Zooberwerx

    Zooberwerx Gold Supporting Member

    Dec 21, 2002
    Virginia Beach, VA
    I was going to suggest a Dremel with ext. cable and small drum sander...I think I have about a hundred floating around the bottom of my toolbox. The ext. cable / handset allows more control as you can rest the side of the hand on the surface as you work...kinda like a dentist with a drill. I suspend my Dremel from the top hook of a recycled IV pole to maximize freedom-of-movement.

    BTW, to the OP: you're close enough to borrow mine if you'd like.

  20. Yes, on the plus side for rotary power tools, they're less likely to splinter the splintery wood.

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