Bend radius of 1/4" (6mm) MDF

[Ed Zeppeli]

Hi all,

I'm working on the design phase of a 15" woofer module which will have curved sides. I only need a radius of 27" (686mm) and am wondering if the MDF will bend to that radius. I will use a three-ply laminate and want to avoid kerfing.

It is unusually difficult to find this information on the net.

Does anybody here have experience bending MDF without kerfs?


Thanks much,

Warren

[Wagner]

How thick? Your laminations?

Good luck bending (and having it hold) any MDF of any thickness without kerfs

I really don't think you can in a shop with any real control (can be done industrially with a press)

Got plenty of bowed MDF shelves out in my garage though!

Can't wet it either

Thomas

[Ed Zeppeli]

Well I'm pretty sure that if I purchased a 4 x 8 sheet of 1/4" mdf and picked it up by the middle there would be a considerable bow to it. Basically I'm wondering if that bow could be 27"r.

Unfortunately my nearest supplier would have to order it in otherwise I'd just check it in-store.

I'm planning on 3 layers for 3/4" plus veneer.

Thanks

Warren

[Wagner]

Well I'm pretty sure that if I purchased a 4 x 8 sheet of 1/4" mdf and picked it up by the middle there would be a considerable bow to it. Basically I'm wondering if that bow could be 27"r.

Unfortunately my nearest supplier would have to order it in otherwise I'd just check it in-store.

I'm planning on 3 layers for 3/4" plus veneer.

Thanks

Warren

Note what I actually said:

How thick? Your laminations?

Good luck bending (and having it hold) any MDF of any thickness without kerfs

Thomas

Well, 1/4", sure it'll bend.

A circle with a radius of 27" doesn't tell me anything, what's the arc's length going to be?

Whether you can pull it off or not would be determined in a large way by the length of your sheets and grade of MDF (the really dense stuff's not going to make it obviously)

Too many unanswered variables in your question; no one at your store that can tell you about the specific product you are considering using?

[Ed Zeppeli]

Just regular 1/4" Medium Density Fibreboard; the thickness of which was mentioned in the title of the thread. Arc length shouldn't matter but here's a rough of what it'll look like.



The dimensions on the left that got cropped out are 23 1/2" and 9 1/2". The sides will be one piece but the dimensions indicate where the arc begins. On top will sit a SAM1HF.

[Wagner]

The arc is going to matter depending on what you have in mind to jig it up to make your panels

1/4" will make that bend degree wise but you'll have a fair amount of waste

It's that transition point from straight to arc that concerns me; why the aversion to a light score there?

[LarryM]

Hi Warren,

My crossovers were divided into 3 sections; LF mounted in bottom backside of cabinet, MF below the 435al and HF below the 045ti. They are CC'd, battery mounted on the back next to the SpeakON connector.

I reused some of the components on the SAM1HF crossover. Many coils and resistors are the same values as the 1400 array. I think a couple of coils had to be unwound a bit. Resistors were either the same wattage or more.

The parts were really a pain to remove from the PCB. The board is plated on both sides and thru-holes too. The copper seemed like it was 2oz, but I may be wrong on that. Basically, you need a high wattage iron.

[JeffW]

That's nice work!

[Ed Zeppeli]

Nice indeed. I was just going to use the internal SAM1HF crossover with an analogue crossover for the bottom end until I get a good DSP to go full active. I never did see any technical information on how the Array crossover differed from the SAM1HF other than anecdotal 'voiced for home theatre' comments.

What is the distance between the bottom of the horn and the top of the woofer? (if you don't mind)

Anyway, excellent project and thanks for sharing.

[LarryM]

From my venture into curved surfaces:
Last year I built a 1400 array with a 4.2cu ft volume and slightly curved sides. I too was vexed with how to curve plywood. I tried 1/2" bendy plywood, but it is so flimsy and full of voids, I gave up on that idea. Instead I constructed a trapezoid out of 18mm Baltic birch and to create the curve, cut thin strips of varying thickness to fill in the sides. The top and bottom plywood is cut with the correct curve. Strips fill in across the curve, positioned for the correct fit. If the strip was too thin or thick, I just made another one. The covering was 1/8" Baltic birch glued and nailed down. For the SAM1HF to get the sharp curve, I used 1/8" bendy ply although I had to search the poor quality sheet for the best section.

I too would like to have used the 2216, but the LE14 works fine. I am happy with the results.

In your case, cut the side as two separate pieces. For the curved portion, lay the strips as I did to create the slight curve you need. Cover with 1/8" plywood or whatever you desire.
A few photos attached; side, looking down through the bottom and finished view.

[Ed Zeppeli]

Nice looking project Larry and thanks for the information. As you can see in my picture above my baffles are already cut to the contour so I will have to try getting the bend with laminated layers of MDF. 1/4" may work and 1/8" will definitely work but that's a lot more layers.

What are you using to crossover your Array clones?

Cheers,

Warren