Problems with the sub's enclosure, damn! (1 Viewer)

[Jones_Rush]

I have just got my new 3c/f sealed box from the carpenter, big problems!!!
The carpenter somehow drilled the screw holes not with complete alignment to the Shiva screw holes. Most of the holes fit but some don't. The T-nuts are already inside. What should I do now ?
I thought to close the current holes, leave the T-nuts inside ('cause I can't get them out now) and drill new holes between the current. My problem is that I am afraid that I'll miss again (the procedure for drilling the holes at the carpenter's workshop seemed ok at that time, we put the Shiva on the baffle board and made pencil marks at where the screw holes were, I don't understand why we missed). The other thing is that I'm not sure I can use T-nuts anymore. When we first inserted the T-nuts we used a hammer and knocked quite hard for it to get in, this was back when the baffle was not connected to the box, now when it is connected, I don't know how I can insert the T-nuts, a hammer will be quite difficult to use in this situation.
Without T-nuts I will ruin the MDF, won't I ?
On top of all this, I am not sure I like this sub's bass quality, I used a sealing caulk and sealed the driver to the baffle (it worked quite good, there are no air leaks at all from the driver's sides) I laid the sub on its side, so the plate amp will be on the top (since I didn't screw the plate amp to it's place I thought to use gravity to keep the amp in its place), I played some songs with bass and I I didn't like what I heard. The bass was not clean, even though I only put the volume knob 1/5 way up, every time there was a demanding bass note, the driver seemed like it's bottoming, now I know this is a sealed sub, but If this is the sound, I'm disappointed.
I hope I just run into the wrong conclusions and when the sub will be completely finished I'll like it.
I will try to post some pictures of the box tomorrow .

 

[Jack Gilvey]

http://www.svsubwoofers.com
Just kidding. Sounds like an imperfect seal, probably around the amp.

 

[Dan_D]

hahah
yeh any leak will cause possibly more problems then you think. seal that amp up and secure the sub and see. Also did you add the stuffing if you planned to do so?
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[DanWiggins]

Jones,
What happened was either one of two things:
1. Non-perpendicular holes (off-vertical will misalign the bolts)
2. Driver moved during marking.
To avoid the first, use a deep-throat drill-press, or a brace/alignment jig for the drill. For the second, I use two screws to hold the driver still, and mark the others. Then you can use the marks and the screw holes to place the T-nut holes.
Dan Wiggins
Adire Audio
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[Jones_Rush]

Thanks for all the help.
Dan,
How will I be able to insert the T-nuts now?. As you know, T-nuts need a hammer knock to insert them in (aren't they?). Now that the box is already glued, I will have to work with the hammer through the 12" driver hole (and the braces), is that practical ?.
I once saw a picture of someone (I think it was Patrick Sun) who drilled the screw holes through the driver itself when it was on the baffle. This way you will always get perferct alignments, do you recommend this way ?
(Gilvey, I wasn't laughing)

 

[Patrick Sun]

Yes, that would be me drilling the holes while the driver was in the driver hole.
Is the driver hole flushmounted? If not, that you should get a small C-clamp and squeeze the t-nuts into the inside of the front baffle.
Here's what I would do to fix this situation:
1. Put the driver back into the hole, and ignore the present holes, and concencrate on drilling in the new holes that should be positioned in between the existing old holes. You may as well drill the holes with the driver in place (be carefull you don't drill a hole in the driver's cone!). Don't forget to seal up the old holes - wood filler would work, or caulk.
2. Once the holes are drilled, position the new t-nuts in the new holes from the inside. (I hope you had the carpenter put in that layer of plywood so that the t-nuts have something to dig their teeth into). Use the c-clamp to slowly squeeze the t-nut into the inside part of the baffle. When you get the t-nut squeezed halfway, put in one of the mounting screws to check on the alignment of the screw with the t-nut. Once you are satisfied with the alignment, just keep turning the clamp screw until the t-nut is in place. Do this for all 8 screws.
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PatCave; HT Pix; Gear; DIY Mains; DIY CC; Sunosub I + II + III; DVDs; Link Removed

 

[Greg Monfort]

Hammering in T-nuts isn't the proper way to install them. They can become misaligned, or worse, damage the baffle material. They should either be pressed in, which can be done with a 'C' clamp, or use the appropriate machine screw with a flat washer to pull it in.
GM
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Loud is beautiful, if it's clean

 

[Jack Gilvey]

(Gilvey, I wasn't laughing)

Rush, lighten up, it'll come out just fine. Enjoy.
Here, have a smilie on me:

 

[Dustin Haug]

Do what Greg said and suck the T-Nuts into the wood using their bolts, this works great. You may still be able to get the old ones out, if so you could probably patch the whole with some bondo and silicon. Don't panic, just take your time and things will work out just fine.
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My DIY sub page

 

[Dan M~]

Sounds like someone mentioned c-clamp installation already. Try removing the old t-nuts buy screwing a long bolt into them and tapping with a hammer. Slow and easy with it. Then put a piece of tape over the hole from the back side and fill the hole with wood putty or a mixture of epoxy and saw dust. Sand flush so the driver flange does not rest on a "bump". Sounds like you have a good cabinet but ANY AIR LEAK at all will cause problems. So seal that amp well and give it another try.
Good luck,
Dan
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-Dan M~
My Small Collection

 

[Vince Bray]

The bad hole thing happens. I once used screws too big,
and it was just impossible to get the alignment right.
Another way to handle the T-nuts which is absolutely
bulletproof ( i have had t-nuts come loose with the driver
still screwed in and it's NOT fun ) is to break off the
little teeth completely. Push the t-nuts in by hand.
Then cut one rectangular 1" x 1.5" piece of 1/4 inch ply
(the good stuff with no voids, or paraply). Now the
confusing part. Using a forstner bit the size of the t-nut
flange, drill a recess just deep enough so the wood will
glue directly to the baffle but clear the t-nut flange,
about 1/16" deep. Offset this recess toward the edge of
the wood block so that it overlaps the edge, and removes
part of the edge. The reason for the offset is that the
t-nut is usually very near or overlapping the edge of
the woofer cutout and this prevents the block from
blocking the woofer cutout. Glue the blocks on.
Now you have mechanically fixed the
t-nut to the baffle, and if you did it right, almost sealed
the back of it. I say almost because the offset of the
recess leaves a void on the inner surface of the woofer
cutout. Fill this with silicone.
A picture would really help here...

 

[Nathan Bower]

You dont use a hammer to install t-nuts?
oh
well uhm when I "INSTALLED" mine, I put some glue on the underside, picked up a 6 pound hammer and smashed the sh!t out of them untill they seemd unable to go in any futher.
Then again I was installing straight into mdf. perhaps its easier with softwoods.
Never had any problems... NHT 1259. I had some alignment issues on a different speaker though. On the holes with mis-alignements I just used some japaned steel screws instead - driven in at an angle.
HTH,
N

 

[Jones_Rush]

Well, I need to install the T-nuts straight into the MDF also, no softwoods on the baffle, just a 1.25" MDF board.
Can a 'C' Clamp push a T-nut through bare MDF ?

 

[Geoff L]

Rush,
Alot of ideas here for you, huh. Dont get to excieted, sounds as though it's long way from being screwed up. No pun intended.
As stated before, rotate driver so as to have clean mdf, to as many if not all holes. Then trace out 3 holes with pencile even spaced around the driver. Remove driver. Then take a fine point center punch, prefer spring loaded type, and center it on the traced holes and punch. I usually do three to start evenly around the driver. Then take a smaller drill bit than is required for your hole and drill the three pilot holes. When doing it by hand take your time to try and drill straight. I know, YA RIGHT.
Follow up with drilling the same pilot hole with the proper size for your T-nut. Once you have the three of these done check to make sure alinement for holes drilled looks good buy setting driver back in. If the holes are little of is ok, key word a LITTLE.
As to the T-nut install, yes they will go into mdf, but much harder than the softer woods. If your 3 pre-drilled holes line up good with the driver, should be no problem right, I leave the driver out at this point, install T-nut and build up washers that fit screw good, thread together and tighten firmly. The pressure will draw the teeth into the mdf.
"Prefer to do it this way in case you slip while tightning, I know im not the only one to put a hole in a driver"!
Check below as sometimes one tooth will be close to or just over the edge of the cut out and this is ok, it will still draw up. I prefer a good cordless drill with proper attachments for this as hand power sucks.
Once all these 3 are done, remove screws and check fit driver again. If all looks good, trace and follow what you did all over again for the rest. Take your time and all will be good.
As to your old holes you end up not useing, all the suggestion above will work fine. I prefer two prt wood expoxy filler.
Dont let it get you down Rush, Think about all you've learned allready. The next DIY will be a piece of cake....
Oh, and as someone else said, "pounding the shit out of them" can work, but not recommened!
Geoff
(edit)
If the T-nuts are scareing the shit out of you, "dont feel as though your the first", you may consider course thread drywall screws. They get a bad rap, as if removed over and over they have tendncy to strip. Found they do a fine job holdig even in sealed designs. Just pre-drill for them and shake a little baby powder or corn starch on them before assembly. Before mounting the amp a little sealer on the back side if they break threw the interior. Though I have never had a leak either way. Has worked fine for a number of my first projects...
Just another idea if the T-nuts are getting you down.

 

[Dean Cooper]

Personally I HATE using T-nuts for MDF, I use inserts that you screw in with a allen key. Here is a link to a better description and picture of what Im talking about. http://www.stafast.com/products/inserts.html
you can get them at you local hardware place and IMO much simpler to install into MDF and work exactly like T-nuts.
Good luck, and I'm sure youll be fine in no time.
Dean

 

[Geoff L]

Dean,
Looks like these coulb be the new norm once many see them. Look to be a piece of cake with these and strong too. Will be giveing these a try with next design.
Do they also come in varying sizes?
Thanks for the link.
Geoff...

 

[Dean Cooper]

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Do they also come in varying sizes?
Geoff...
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Yes they do, I would say that there are more options of what you can get with these than T-nuts.
Dean

 

[Phil Olson]

I just finished a dual sealed tempest a month ago. What I did was cut 1"x1" squares of 1/4" plywood, drill them and hammer the t-nut into them.
I then slathered them with glue and used the screw holes in the end cap to tighten them against the MDF, (using the screws as clamps, in essence).
This worked like a charm so there is no reason you couldn't easily do the same now.
Also, for drilling the holes, I laid the driver in the hole and GENTLY drilled 1/4" holes about 1/4" deep. I used a portable drill with low torque so that it wouldn't 'get away' from me. Once that was done I removed the driver and took the end cap over to my drill press, using the 1/4" deep holes as pilots.
You can get a real deal on drill presses at Home Depot nowadays. Unfortunately, since you already have the end caps mounted, you'll just have to be carefull drilling perpendicular. I think you can buy an attachment at Home Depot that will assist you in holding the hand drill perpendicular so you might want to invest in one of those.
Hope this helps,
Phil

 

[Hank Frankenberg]

Like Dean, I always use the hex drive, threaded inserts. Be careful threading them in so they go in perpindicular to the surface. I like to glue a piece of 1/4" oak over the hole area so that the insert is threaded into the oak, then into the MDF. That makes for a better hold for the inserts' external threads. I spread some epoxy on the insert's external threads also. Never have had a threaded insert come loose.
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