DCAudioDIY.com

DC Area Audio DIYer's Community
It is currently March 28th, 2024, 5:50 am

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 ... 8  Next
Author Message
PostPosted: September 24th, 2019, 9:15 am 
Offline
User avatar

Joined: February 28th, 2013, 3:31 pm
Posts: 1780
brombo wrote:
These screws work well in MDF if you drill the appropriate hole -

http://www.leevalley.com/en/wood/page.a ... 41315&ap=1


Those would probably work well if you were screwing into the flat section of the MDF sheet. I have never had a problem there. The problem is when you screw into the end of the sheet as I did on the layered egg construction. Behind those holes which were created with a pilot drill was the interior opening of the egg. Therefore there was only a little over an inch of material. Although I never had a problem before it made me realize how close to problems I had been in the past and decided against wood screws. When mounting drivers on the flat surface of the inside of an enclosure I always glued backup pieces of scrap MDF to increase the thickness of the wood at the mounting surface to prevent splits. There is no need for screws for the main assembly if you use biscuits and with them no need to fill surface holes. Also, with driver mounting the machine screw inserts allow many insertions and removals of the screws without having problems with holes enlarging as is often the problem with wood screws. Lots of different methods that work depending on the individual situation.


Top
 Profile  
 
PostPosted: September 24th, 2019, 10:26 am 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
To follow up, designers of knock-down furniture made of MDF have more control over the design of joints, grade of MDF, backed up against assembly and stress tests in the lab in order to refine what will work reliably given the jointery demands. As DIYer trying to get it to work right first time (so it does not have to be re-made), need to be more wary of endgrain spltting, which cheaper MDF grades (like the Georgia-Pacific MDF) that one gets from Home Depot. Many MDF & Particle Board construction screws that claim to require no predrilling really only work cross grain, not end-grain. Even pre-drilling endgrain will cause splits since the fibers are so much weaker in tension than compression. That many of these screws are flat-heads means you are driving a wedge into the grain.

Agree that the best solution is use biscuits, dowels, etc. with glue for endgrain joints in MDF, or use wood battens glued to the MDF if you need to have a removable panel (screwing into the batten, not the MDF). Nothing else is reliable enough to hold without potentially destroying the work.


Top
 Profile  
 
PostPosted: September 26th, 2019, 8:23 am 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
Nails as registration pins worked great. The pictures show the clamp extenders I made for gluing the top and bottom on the enclosures. Worked like a charm.

Looks like this weekend I start patching, sanding, and sealing the cabinets.

David


Attachments:
20190925_164538.jpg
20190925_164538.jpg [ 605.13 KiB | Viewed 11230 times ]
20190925_172958.jpg
20190925_172958.jpg [ 752.92 KiB | Viewed 11230 times ]
20190925_164548.jpg
20190925_164548.jpg [ 752.92 KiB | Viewed 11230 times ]
Top
 Profile  
 
PostPosted: September 26th, 2019, 9:35 am 
Offline
User avatar

Joined: February 28th, 2013, 3:31 pm
Posts: 1780
Very cool idea with the clamp extenders. Another one of the many fixtures you need to build with a complicated project. Glad the nails worked.


Top
 Profile  
 
PostPosted: September 30th, 2019, 9:28 am 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
Router Fun!

I patched and routed out the edges of the cabinets over the weekend. For patching I used Bondo wood filler. The pot time on this is a few minutes, had to mix up a couple of batches just to do the face of one speaker cabinet. However, it sanded down nicely and really holds a good edge, better than any other wood filler I have used. For routing, I used a 30 degree bevel bit on the front (and back) baffle, and 45 degree on the top and bottom edges. Need to do some hand work to cut faceted corners. Should start final filling and sealing of the raw MDF edges later in the week.

David


Attachments:
20190930_061125.jpg
20190930_061125.jpg [ 934.59 KiB | Viewed 11180 times ]
Top
 Profile  
 
PostPosted: September 30th, 2019, 11:33 am 
Offline
User avatar

Joined: February 28th, 2013, 3:31 pm
Posts: 1780
Looking good. That bondo filler is what I also used on the eggs. Great stuff.


Attachments:
PICT0299_small.jpg
PICT0299_small.jpg [ 67.32 KiB | Viewed 11176 times ]
Top
 Profile  
 
PostPosted: September 30th, 2019, 11:41 am 
Offline
User avatar

Joined: February 19th, 2017, 9:43 am
Posts: 530
Clever clamp extenders. Impressive project, looking forward to hearing them.

_________________
I have too much stuff - https://www.pleasebuymystuff.com


Top
 Profile  
 
PostPosted: October 4th, 2019, 8:30 am 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
I took the day after my birthday (Wednesday) off to work on the speakers (being stuck in a 6-1/2 hour meeting on my birthday was no way to enjoy it). So I patched, sanded and finally applied shellac as a sealant on the raw MDF. Used wax-free clear shellac (Zinsser Seal-Coat). The MDF really soaked up the shellac, I went through a quart of the stuff, with two coats on each of the MDF edges and a single coat on the flat surfaces. I could have used another quart, I think. After it dried, I sanded the surfaces down with a 180 grit sanding disc, and they turned out pretty smooth.

I decided to use Duratex to paint the cabinets, based on my satisfactory experience with it on a another project. It drys and cures super hard, and tends to cover-up minor surface imperfections. I like using a fine foam roller to apply to get a relatively smooth (matte) surface rather than the highly textured surface used on road cabinets. I bought a gallon of white spray grade (based on reports of it being easier to apply with a smooth foam roller) and tinted it to a blue-grey color using concentrated Cal-Tint lamp black and blue liquid tints that I picked up on Amazon (I have lots left if anyone wants to experiment). I just added equal amounts of the black and blue tints to get the desired color. After thoroughly mixing with a drill powered impeller (trying to avoid splattering the paint all over), I let it sit a day. Last night I painted the first coat on all but the back surface of the speakers. Really easy to get a smooth (fine textured) surface with no overlap marks. This is the initial coat, which will probably be sanded down before applying the next coat.

David


Attachments:
20191004_051427.jpg
20191004_051427.jpg [ 1.5 MiB | Viewed 11121 times ]
20191004_051453.jpg
20191004_051453.jpg [ 1.66 MiB | Viewed 11121 times ]
Top
 Profile  
 
PostPosted: October 10th, 2019, 3:09 pm 
Offline

Joined: March 12th, 2013, 11:12 am
Posts: 738
Can't wait to hear these! Color looks very cool! I went back and did a big double take while looking at the impedance and phase curves. Usually in my field, when you see something that good, it is a result of fraud! :D


Top
 Profile  
 
PostPosted: October 10th, 2019, 6:39 pm 
Offline

Joined: February 28th, 2013, 1:19 pm
Posts: 914
Just finished with all the painting as of a day ago. Working on the crossovers (done, actually) and wiring harness. I hope to start assembly of the speakers on Sunday, finishing over the next week. So expect to have them in the system by next weekend!

Now need to go down to the basement and cut and tin lengths of Cardas 15.5ga litz for the internal wiring. Will use a smaller gauge for the tweeter, however, the terminals are pretty fragile looking.

David


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 ... 8  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: Google [Bot] and 32 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