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Mini MEH out of wood


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Everythjng went so well with the k402MEH, and it sounds great, but I felt it would be nice to have one that was just a bit smaller for my surrounds (or if it sounds good enough use it for my fronts, and make a sub to go under it, and move the k402s to the surrounds). I also have wanted to build a wood version, so I decided to build a mini that is made out of wood.

 

I have a spare k402 that is just laying around in the garage, so I took it and modeled the short side of the horn. My intent is to make the horn square instead of rectangular to make it smaller...which I am thinking might work out better for smaller rooms and WAF.

I started with a piece of 1/8" plywood and cut it to the size required to go from the compression driver mounting flange to the  part where the mouth switches to a 90 degrees change. I then got some double stick tape and clamped it to theside of the horn. Next I started cutting small pieces of MDF with different angles to fit together like a puzzle. Once I had enough of them that matched and went from the flange to the mouth of the horn...I glued and clamped them to the plywood (still attached to the horn). I let it dry for a couple of days and then pulled it off of the horn. It was not exactly easy as I had used 3m double stick take and ran 2 strips the full length of the horn, but it came off undamaged.

 

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Step 2

I brought the wood to a friends shop and he cut the pieces to the exact size needed and squared them up for me. Next he showed me how to use the saw to cut the kerfs and demoed some cuts for me. Several hours later I had one sheet of 3/8" Baltic Birch plywood cut into 8 pieces and kerfed. Next I had my friend cut me some templates from the modeled piece I had made. I know now that we should have used both halves of the cut as I will explain later.

When I got home I made the jig and stupidly installed the pieces in a couple of inches thinking it would give better clamp clearance when in fact what it did was create a bow in the horn side! I then made a couple more pieces and installed them at the edges. I clamped up a horn piece and everything went well, until I went to glue the kerfs and notice I could not get into glue very well due to all the clamps required. I then decided I needed a top portion to due the clamping properly and have good access. This is where I  needed to have the exact pieces that would have been the 2nd side of the template cuts. I tried my best, but my cutting was not quite as good as I wanted so I made the jig anyway and used some scraps to shim the top part to get as perfect as possible for the bottom jig. It is about a fingernail thickness off at some points and perfect on the rest.

 

Now the next part is to make the horn thicker. Originally I was going to use Rocker prekerfed MDF and UPS managed to destroy or lose 2 shipments from Amazon to Laredo Texas. I decided to give them another try as I think they are actually the best option because...

1:  all perfect cuts

2: kerfs already cut so much time is saved

3: about $30 for enough to do 1 speaker horn 1/4" thick

 

What I am going to do is take the 1/4" (if It makes it) and add it to the woofer side of the horn (most likely just for the bendable part of the horn). If I need more strength were the woofers are I will add a layer of non kerfed MDF for the woofer area only.

 

Now what I did when I was gluing up is to use some old duck cloth to prevent my pieces sticking together but I will be using waxed paper from here on out.

Now gluing takes along time as the glue keeps settling in as it cures, and Bondo is much easier IMO and dries faster and is rock hard which is much better for getting the project done quicker too. Now if you go with Bondo and want to veneer the horn you will  need contact cement. My situation might have the horn sticking out like my larger MEHs, and if I do that I will most likely get some bendable plywood and use it only for the bent part of the backside of the horn which will be sticking out, and then I can veneer with peel and stick veneer on top of the plywood finish.

 

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  • NBPK402 changed the title to Mini MEH out of wood

Examining an OEM K402, if you pull a string from the center of the throat to the center of the mouth and measure the angle to the side panels, and then measure the angle to the top and/or bottom slopes, there is a big difference. You might need to calculate new angles for your square mouth horn project.

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  • 2 weeks later...
Examining an OEM K402, if you pull a string from the center of the throat to the center of the mouth and measure the angle to the side panels, and then measure the angle to the top and/or bottom slopes, there is a big difference. You might need to calculate new angles for your square mouth horn project.
Thanks, I made a quick one out of bendable 1/8" plywood, and it worked...I am making a jig that when the 2 square sides are in it... I will be able to trace out the other 2 sides to cut the angle (To be sure.) I hope to be that far by the end of the month. I just got some 2'x4' prekerfed wood off of Amazon, and it appears to be perfect for making the horns. I can try out a 1/4" horn and keep adding layers until I have the thickness I want.

I also am making a new jig that was cut on a CNC so my curves will be much closer to perfect.

Sent from my SM-T830 using Tapatalk




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I received some prekerfed 1/4" from amazon the other day, and I put it in the new jig...it appears to be much easier to get exactly the same as the jig is when bent. I can actually press it by hand fair,y easily to get it perfect, where as the 3/8" needs to be clamped very tight to get it perfect. We will see how it goes later this month when I start forming them. Cost wise for someone who doesnt have the ability to kerf the mdf...the preferfed is about $100 for enough to make 2 horns 1/4" thick.

This time we are going to try Bondo in the kerfs.

Sent from my SM-T830 using Tapatalk





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