DCAudioDIY.com

DC Area Audio DIYer's Community
It is currently March 28th, 2024, 1:00 pm

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 72 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8  Next
Author Message
PostPosted: January 4th, 2018, 11:59 am 
Offline
User avatar

Joined: February 28th, 2013, 3:31 pm
Posts: 1780
SoundMods wrote:
tomp wrote:
HAL wrote:
Thanks for the tips.

Have a finishing shop that is going to paint them hot rod black as they are doing for my 6x12 cabinets.


I had an auto body shop paint my eggs with the same PPG black metalic paint that is on my wifes car. After seeing the photos of what he went through you don't want to try it yourself. To get a smooth finish across the glue joints he had to use something known as icing in the trade.


Otherwise known as "Bondo" or "mud."


I asked him if it was Bondo because that is one of my staples but he said no. It is some kind of white polymer. If you try to sand only it will not work. My final sand was 800 grit and it felt so smooth you would think it was glass. In fact he had to slightly rough it up to get anything to adhere properly. When you have wood and glue they don't sand at the same rate and you will always have very slight differences in the surface that feel like rippples at the interface. He said it would be visible in the finished job. Putting the icing all over gives a homogeneous surface for sanding. Here is a photo of the "white" egg.


Attachments:
Sees egg 2.jpg
Sees egg 2.jpg [ 425.41 KiB | Viewed 16330 times ]
Top
 Profile  
 
PostPosted: January 4th, 2018, 12:55 pm 
Offline
User avatar

Joined: February 28th, 2013, 3:31 pm
Posts: 1780
brombo wrote:
For open baffles glue is enough since the forces on the joints are not great. If you are using mdf for a closed box system in addition to glue I would use confirmat screws.

https://www.amazon.com/HighPoint-Confir ... B0031TGSB2

They are especially made for mdf.


I have given up on screws and use biscuits because the plate joiner cuts slots in the wood that accept the biscuits so there is no spreading force on the MDF. There are also no holes to fill and sand. I recently found another problem with screws. For years I have used MDF screws to hold drivers in the enclosures with no problems. With the eggs, using the same screws and pilot drill, after about two months I started to see small lines appearing in the finish of the eggs near the screws. I removed the drivers and noticed that the screws were causing the MDF to separate slightly. The same setup in the bass cabinets where the screws were inserted perpendicular to the surface has caused no problems. This is the first time I have fastened the driver into what is the end of the MDF since the egg is made of stacked cutouts from sheet stock. Apparently screwing into the end of the sheet is a problem.

I immediately removed all the screws to prevent the problem from spreading. I then purchased some EZLok threaded inserts so that I could use metal screws to install the drivers. I did not want any sideways force on the ends of the layers so I did a test on a scrap piece of MDF with incrementing size holes from a series of numbered drills. I found for these fasteners a "K" bit that is 0.281 left just enough wall material to allow the threads of the inserts to pull them into the holes with barely any wall contact.

To insure holding power. I coated the inside of the test hole and the outside of the insert with JB weld epoxy and screwed the insert into the test hole. The bottom of the insert had a small circle of masking tape over it to prevent the epoxy from entering the threads. After two days, I began a test to see at what point the bond to the insert would fail. I put a large washer around the insert to allow it to pull out of the hole and used a machine screw and washer to apply tension to the insert. I tightened it as far as I ever dared with a screw and it held. The next day I continued to tighten the screw with a ridiculous amount of force until the washer deformed. At that point the insert pulled very slightly out of the hole. Since that amount of force was totally over the top and far more than the screw was designed for I considered it a success and installed all the inserts in the new pilot holes. I'm including photos of the process. Time will tell how it works. but I would suggest caution when using screws into the edges of MDF sheets.


Attachments:
Screw hole problem_small.jpg
Screw hole problem_small.jpg [ 398.29 KiB | Viewed 16329 times ]
EZlok inserts_small.jpg
EZlok inserts_small.jpg [ 388.33 KiB | Viewed 16329 times ]
Hole size test_small.jpg
Hole size test_small.jpg [ 122.02 KiB | Viewed 16329 times ]
Top
 Profile  
 
PostPosted: January 4th, 2018, 3:30 pm 
Offline

Joined: February 28th, 2013, 3:31 pm
Posts: 363
Great technique Tom. On a recent work project I did a similar install, except I drilled oversized holes that I filled with thickened epoxy, allowed to cure, then drilled the epoxy with the smaller holes for the 10/24 threaded inserts. Installed the inserts with thickened epoxy as well. Hard to see in this photo, but there are inserts set in epoxy visible on that 1st board.


Attachments:
20160619_101857.jpg
20160619_101857.jpg [ 761.19 KiB | Viewed 16325 times ]
Top
 Profile  
 
PostPosted: January 4th, 2018, 5:12 pm 
Offline
User avatar

Joined: February 28th, 2013, 3:31 pm
Posts: 1780
Jim G wrote:
Great technique Tom. On a recent work project I did a similar install, except I drilled oversized holes that I filled with thickened epoxy, allowed to cure, then drilled the epoxy with the smaller holes for the 10/24 threaded inserts. Installed the inserts with thickened epoxy as well. Hard to see in this photo, but there are inserts set in epoxy visible on that 1st board.


That would probably work even better but as you can see from the photos I was very close to the front surface of the egg and I didn't want to chance marring the front.


Top
 Profile  
 
PostPosted: January 4th, 2018, 5:38 pm 
Offline

Joined: July 8th, 2016, 4:34 pm
Posts: 570
Attachment:
brad-hole-tee-nuts.jpg
brad-hole-tee-nuts.jpg [ 18.21 KiB | Viewed 16317 times ]
For flat panels you can use brad hole tee nuts. I use them to mount the 18 inch drivers for my sub-woofers.

http://monsterfastener.com/group/fasteners/nuts/tee-nut


Top
 Profile  
 
PostPosted: January 4th, 2018, 5:46 pm 
Offline
User avatar

Joined: July 24th, 2015, 4:17 pm
Posts: 1701
Location: Parkville, Maryland
I asked him if it was Bondo because that is one of my staples but he said no. It is some kind of white polymer. If you try to sand only it will not work. My final sand was 800 grit and it felt so smooth you would think it was glass. In fact he had to slightly rough it up to get anything to adhere properly. When you have wood and glue they don't sand at the same rate and you will always have very slight differences in the surface that feel like rippples at the interface. He said it would be visible in the finished job. Putting the icing all over gives a homogeneous surface for sanding. Here is a photo of the "white" egg.[/quote]


This is all good to know. I have a friend that runs a state-of-the-art body shop. Their work is impeccable. Should I need a big piece done I'll see if they're game.

_________________
Walt


Top
 Profile  
 
PostPosted: January 4th, 2018, 6:24 pm 
Offline
User avatar

Joined: January 13th, 2016, 9:14 pm
Posts: 787
The folks I work with did a great job on my first module for the bigger subs.


Attachments:
WP_20171117_006.jpg
WP_20171117_006.jpg [ 320.73 KiB | Viewed 16313 times ]
Top
 Profile  
 
PostPosted: January 4th, 2018, 8:47 pm 
Offline
User avatar

Joined: February 28th, 2013, 3:31 pm
Posts: 1780
brombo wrote:
Attachment:
The attachment brad-hole-tee-nuts.jpg is no longer available
For flat panels you can use brad hole tee nuts. I use them to mount the 18 inch drivers for my sub-woofers.

http://monsterfastener.com/group/fasteners/nuts/tee-nut


Yes, those work great. The problem in my case is the inside of the egg is not flat. Everything about this project was a major PITA. This photo will give you an idea of what the inside surface looks like. Also, since I did not know the exact location of the driver holes I could not install them before I closed up the egg.


Attachments:
Diffuser in bottom_small.jpg
Diffuser in bottom_small.jpg [ 96.78 KiB | Viewed 16307 times ]
Top
 Profile  
 
PostPosted: January 5th, 2018, 4:57 pm 
Offline
User avatar

Joined: January 13th, 2016, 9:14 pm
Posts: 787
Second flatpack box unpacked and getting ready for some glue-up and clamps. Was stored in the garage, so letting it warm up to room temperature first.


Attachments:
WP_20180105_003.jpg
WP_20180105_003.jpg [ 313.19 KiB | Viewed 16297 times ]
Top
 Profile  
 
PostPosted: January 6th, 2018, 7:55 am 
Offline
User avatar

Joined: January 13th, 2016, 9:14 pm
Posts: 787
Modules #3 and #4 completed and glue dried. Time for test fitting the drivers and make the wire harnesses.


Attachments:
WP_20180105_004.jpg
WP_20180105_004.jpg [ 257.48 KiB | Viewed 16287 times ]
WP_20180105_006.jpg
WP_20180105_006.jpg [ 308.8 KiB | Viewed 16287 times ]
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 72 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6, 7, 8  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 45 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group