Metronome with FE167e construction questions

[kyndig2]

After looking at numerous horn designs and deciding they were beyond me right now I am pretty set on building a set of Metronomes! I've settled on the Fostex FE167e as the driver due to price/performance considerations (buying a house this year, money is limited). Since these are my first speakers my experience is negligible. The only DIY I've really done is Headphone amps!

With all of the articles mentioning the Metronomes I'm assuming there are quite a few of these things around. Unfortunately I'm a software engineer, not a wood worker! The plans have been giving me some headaches... My attempts to make a model in SketchUp from the plans at Frugel-Horn have been mostly successful yet frustrating. I just can't envision the actual build process in the Birch Plywood to make this thing happen!

One of the main things that I'm stuck on is how to do the angles on the boards. I saw in the thread "My Metronome Experience" that he did some of his cuts on a table saw at 86.5 degrees. By my model in SketchUp the actual angle for sides of each main piece are actually a bit more than 86.5 degrees, but not quite 86.6. Will 86.5 degrees work just fine? Then there's the lean angle of each board that appears to be ~86.1 degrees. If I do the 86.5 degree cut on each of the 4 side boards I'm assuming that I can just lean them against each other and just make sure that the edges match up?

Next are the "feet". Trying to make them flat at the angle the boards will be leaning at is confusing me! Then there's the arches. It appears that each arch is going to the height of the bottom of the mass loading board with the port. Is this height supposed to be done when the board is at 90 degrees then lean it over? I'm also assuming that the top cap and the port board should just have their edges angled to about 86.5 degrees? I'm uncertain as to how to physically do that. There's also the fact that the height of the actual boards isn't very clear. The plans show the speakers having a total height of 64 3/8" but doesn't list the actual board length!

If anyone is interested in my current SketchUp model I'm happy to email it to anyone who asks. I just don't have a good file store area on the Net at the moment. I really want this project to go well so I'm very caught up in all of the minute details... I hate not being exact at this sort of stuff so any help in creating these seemingly awesome speakers will be greatly appreciated!

My main issue is obviously that I have extremely limited wood working experience! Fortunately I have a few friends who have made some small furniture that will be helping me with the actual cutting and assembling. The father of one of these friends was generous enough to offer his personal workshop for my use on this project. He's a manager at Lowe's and has a 2 story separate building for his work shop! I haven't actually been in it yet, but supposedly he has quite a nice selection of tools to use.

 

[lousymusician]

I think I posted this in the Metronome thread, but here's how I made mine with relatively few tools. The major cuts for the sides were made with a circular saw with a decent carbide plywood blade and an edge guide. The blade of the circular saw was set square for all cuts.

As a simplifying assumption, I took the 64-3/8" dimension as the board length and cut off my plywood sheet to that dimension. Then I drew out the first front side full size on the sheet. I struck a center line, marked off the width of the top and bottom centered on the CL, and connected the dots. I then very carefully clamped down my edge guide the proper distance from the marked line, measured it three more times to be sure, and made the first cut. The other edge was cut the same way, measuring multiple times before committing. Rather than laying out the next three sides, the first was used as a template to mark the plywood. The process was repeated for the sides. Again, all of the long cuts are made with the blade square to the plywood.

With all sides cut, I stood the pieces of one enclosure up in position with the aid of some masking tape. I used a sliding bevel to transfer the angles of the pieces to the floor to the table saw, and I cut the pieces for the tops to fit inside the pyramid.

I edge banded the fronts and backs with iron-on birch veneer before assembly, so that the plywood edges would be hidden and the veneer would be flush after gluing. I used biscuit joints along the long edges to aid in alignment during gluing. I did the arches by laying out the curve with a compass, cutting them freehand with a jig saw, and cleaning up with a sanding drum in an electric drill. (A router and circle jig would do a neater job!).

With the four sides and top glued, I had to level the top. The top plywood edges were square to the plywood faces, so once glued up they were tilted inwards, with the internal top flush with the inner edges of the plywood. 50 grit paper in a 1/3 sheet sander quickly leveled the edges down to give me a flat top. I then for cosmetics I cut a piece of thin poplar, glued it down to the top, and sanded the edges to match the angles of the sides.

I cut the bottoms on the table saw, again using a sliding bevel to transfer the angles. A little glue, and they were tapped into place with a mallet. Again, measuring three times before cutting gave me a good tight fit.

The feet were leveled out the same way as the top, with 50 grit in the sander and lots of checking to keep things flat. I then cut some blocks to glue into the corners (the small pieces had to be cut with great care on the table saw!), and installed carpet-piercing spike feet. The blocks and feet are invisible from the room, the speakers just 'float' a tiny bit above the carpet.

If I was doing a production run of Metronomes, no doubt I'd build taper jigs to do the long cuts on the table saw. For just the one pair, and with no time constraints, doing it 'the hard way' worked fine for me. I'm quite happy with the results. How you make yours will have to depend on the tools to which you have access, and whatever methods you're comfortable with.

I wonder how many Metronomes really have been built? I suspect it's still a pretty exclusive club!

Bill

 

[planet10]

The only really complete plans done for a Met are some i've done for the FE127 and i just recently did those. You can use them as a guide.

http://p10hifi.net/tlinespeakers/FH/download/FE127-Metronome-plan-301207.pdf

The angles in most Mets are small enuff that a hack like me would do it with 90 degree cuts, a file, sand paper, and a good gap filling glue (Chris doesn't let me build boxes anymore ) You can see that this is also how i did the sketchup visualization (i wouldn't mind a copy of your model -- why don't you post it to the 3D wharehouse?)

I think this is the approach Stephen took on the 1st one (and a round-over bit on a router)

The eiffel tower legs on the bottom are a specific style -- the same can be achieved a number of other ways.

dave

 

[kyndig2]

lousymusician: Thank you so much for the detailed breakdown of how you constructed your Metronomes! I believe that I can actually construct the darn things now... I'll continue working on my SketchUp model based on the original plans though. Tonight I will be sitting down with the two guys who offered to help me build the speakers so that we can make sure we know wtf we're doing.


planet10: Thanks for the link to the plans. Definitely the most detailed ones I've seen for a Metronome so far! I had looked at your site some but had overlooked those particular plans. Once I get a bit further with the SketchUp plans I will make sure to get a copy of them to you!


Oh yeah, also I wanted to bring up one other issue that I'm dealing with. Since I'm in the US I have a bit of trouble finding 18mm thick boards of Birch! The Lowes around here only has 18mm boards of "Luan"? or something like that. Everything else is in fractions of inches. I'm aiming at making mine out of 3/4" Birch plywood from Lowes and just making sure that interior dimensions are the same. I'm assuming that this won't cause much of a problem? If anyone can think of any problems with this approach please let me know before I screw things up!

Thanks for the help guys! Hopefully I'll have some construction pics this weekend? I have to check with my friends to see when we can begin work though.

 

[planet10]

Thanks for the link to the plans. Definitely the most detailed ones I've seen for a Metronome so far! I had looked at your site some but had overlooked those particular plans. Once I get a bit further with the SketchUp plans I will make sure to get a copy of them to you!

Actually until your post i had forgotten that i hadn't added these plans to the Met page. I did them up for a fellow in Slovakia building FE127eN Mets

Oh yeah, also I wanted to bring up one other issue that I'm dealing with. Since I'm in the US I have a bit of trouble finding 18mm thick boards of Birch! The Lowes around here only has 18mm boards of "Luan"? or something like that. Everything else is in fractions of inches. I'm aiming at making mine out of 3/4" Birch plywood from Lowes and just making sure that interior dimensions are the same. I'm assuming that this won't cause much of a problem?

That will cause no problems.

dave