mounting an AV15: T Nuts?

Discussion in 'Home Theater Projects' started by LanceEAR, Feb 4, 2004.

  1. LanceEAR

    LanceEAR Agent

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    A couple of questions:

    1) Are Tee Nuts the best way to mount an AV15 to MDF?
    2) My plan is to mount the driver down-firing. Any problems with that?
    3) What should I use to get an air tight seal around the driver? I've found threads about weather stripping but is there a particular type that works best?

    TIA!

    -Lance
     
  2. Ronnie Ferrell

    Ronnie Ferrell Second Unit

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  3. LanceEAR

    LanceEAR Agent

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    Thanks for the links.

    Are the threaded inserts similar to screws? ie: one piece vs Tee Nuts which require two pieces (Tee Nut + Screw)

    Also, why do you recommend against using tee nuts?

    Thanks,
    Lance
     
  4. Brian Bunge

    Brian Bunge Producer

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    Lance,

    A threaded insert still requires some sort of bolt to mount the driver. The difference is, with a threaded insert, it actually screws down into the MDF and cannot tear out like a T-nut's "teeth" can. The insert has a hole in the middle just like a T-nut that is threaded to accept some sort of bolt or machine screw.
     
  5. Ronnie Ferrell

    Ronnie Ferrell Second Unit

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    I do not recommend using t-nuts with MDF because the teeth/prongs of the t-nuts will not hold in MDF. T-nuts work well in real wood and plywood, but not MDF.

    If you are set on using t-nuts, be sure to glue small pieces of 3/4" plywood to the back of the MDF baffle where the t-nuts will go. Drive the t-nuts into the plywood and use longer bolts. (there's someone around here that has pictures of this, but I cannot find them right now.)


    rf
     
  6. LanceEAR

    LanceEAR Agent

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    I'm not set on anything yet but I know I'll have problems somewhere along the line and need to remove the driver.

    As for glueing the plywood onto the MDF, I actually saw that picture which prompted my question. Now I can't find the link either.

    Thanks again.

    Anyway, I now understand the differences and the threaded inserts sound like they will work better. Any idea if the threaded inserts are avail. at HD or Lowes?
     
  7. Ronnie Ferrell

    Ronnie Ferrell Second Unit

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    yes and no.

    Yes they have threaded inserts but they do not have "knife" like threads which hold well in MDF. They would not be any better than using wood screws IMHO. The ones in the link I posted above work really well and are pretty cheap. McFeely's is a good company.

    Here are some build photos of the McFeely's threaded inserts I used. Notice the deep threads on the outside that hold in the MDF.

    [​IMG][​IMG]
    [​IMG][​IMG]

    [​IMG]
    [​IMG]
    Those last 2 are of the inside of the baffle. I have it flipped over on the sub.

    Here is what it looks like from the "driver" side of the baffle:
    [​IMG]

    rf
     
  8. Denis P

    Denis P Extra

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    I've mounted 4 AV15's in an IB setup using round head screws (#10 I believe). I'm using plywood so it's a different situation. Eight #10 coarse thread screws provide a lot of holding power, even in MDF. If you mount the drivers so that the back of the flange is against the baffle, you don't have to worry about a seal. The AV15's have a rubber seal/trim ring that will seal it.

    Regarding T-nuts: They work very well so long as you mount the flange on the inside of the cabinet. There is no way you are going to have a problem until you pull the flange through your cabinet and completely destroy it. If you put the flange on the outside, of course the teeth will pull out. The teeth are intended to stop the T-Net from turning not to stop it from pulling out. I've had no problem with T-Nuts and they will definitely provide a stronger connection (using the flange on the inside) than threaded inserts IMHO.

    I've used threaded inserts and have had limited luck in MDF. If you don't drill the hole exactly the right size - not too big, and carefully screw it in perpendicular you can easily chew up the MDF and it will pull out. For those who have had good luck - I'm happy for you. I won't be trying them again.
     
  9. Ronnie Ferrell

    Ronnie Ferrell Second Unit

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    Denis, Sounds like you have never had a t-nut back out of MDF when trying to unscrew a driver mounting bolt. Just the slightest bit of pressure can push the t-nut out of MDF. (i.e- the pressure you have to exert to get the screw loosened in the first place.) When this happens, unless you have hand access to the inside of your enclosure,(i.e- plate amp hole in a sub) it's very hard to extract the driver. I've heard horror stories of guys totally screwing up a driver trying to remove it from an enclosure after having a t-nut back out on them. Now if you do have access to the T-nut after it has dislodged and is spinning in the MDF, it's a piece of cake to fix.

    Glad you have not had this problems with T-nuts in MDF before.

    My experience is the exact opposite of yours. I'll never use T-nuts in MDF again and will stick with deep course thread inserts or course panhead screws. If my only choice was normal Home Depot run of the mill threaded inserts (not deep threaded) then I would choose #8 or #10 course threaded screws. Not the normal tapered wood screws from Home Depot, but non tapered pan head screws (see link above). They are course threaded like drywall screws with a pan head instead of flat. These screws are good for numerous removals in MDF. Then if you do strip out the MDF, just rotate the driver an inch or so and drill new screw holes.

    One other thing I shound have mentioned about the treaded inserts-- Make sure they also have a back flange like t-nuts. The ones without a back flange do not work well at all in MDF.

    rf
     
  10. Owen Bartley

    Owen Bartley Second Unit

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    OK, let me see... That might have been me, although I saw someone else do it first, which is where I got the idea. Check my sig for pics.

    It seemed to work out alright, given the fact that I don't plan on opening it up any more. (I did once after it had set in for a while to refinish, and had no problems). The main issues I had were:

    1. I didn't use a router and jig to cut my driver holes, I did it by hand so they were a little uneven. I had to use the plywood backing on some where the T nut wouldn't bite properly.

    2. It was awkward to fit them in around the driver and amp, and since I used glue for extra strentgh, that can get messy too, you have to be careful.

    In the end it turned out ok. But Ronnie, your threaded inserts look about 800 times cleaner than mine and I think I'll give them a try next time. I'm a little ashamed of the inside of my box. :b It should be pretty like yours.
     

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