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MARTELLO-2, a mini-tower from a single 2' x 4' for EL-70/CHR-70
I still have a pair of EL-70's looking for a new home and my sister wants some small speakers (narrow baffle not too tall) to flank her TV with. So I've decided to draw up a small-tower based off planet10's micro-tower series of ML-TLs. This will be for a single driver.
My local hardware store carries sheets of 11.5mm thick birch plywood in 2' x 4' handy panels. So the design for one speaker must fit on such a sheet.
I will double up the front baffle around the driver since it needs enough thickness to allow for the driver rebate, have enough depth for the mounting screws and be stiff.
Lots of bracing for stiffness given the use of only 11.5mm plywood.
For aesthetic reasons the front edges (sides & top) will be mitred, the rest will use simple butt joints.
The design will also work with the CHR-70 so that if one of her dogs destroys the EL-70 drivers there is a current-production driver available to retro-fit (with some minor adjustments).
I still have a pair of EL-70's looking for a new home and my sister wants some small speakers (narrow baffle not too tall) to flank her TV with. So I've decided to draw up a small-tower based off planet10's micro-tower series of ML-TLs. This will be for a single driver.
My local hardware store carries sheets of 11.5mm thick birch plywood in 2' x 4' handy panels. So the design for one speaker must fit on such a sheet.
I will double up the front baffle around the driver since it needs enough thickness to allow for the driver rebate, have enough depth for the mounting screws and be stiff.
Lots of bracing for stiffness given the use of only 11.5mm plywood.
For aesthetic reasons the front edges (sides & top) will be mitred, the rest will use simple butt joints.
The design will also work with the CHR-70 so that if one of her dogs destroys the EL-70 drivers there is a current-production driver available to retro-fit (with some minor adjustments).
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fabricate with the bottom panel mounted on cleats to accommodate easy replacement of the port assembly if you need to swap drivers
of course you already thought of that
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😀
Chris - yes good idea, cleats on the bottom allow for tuning of ports and stuffing and all that whatnot. Of course changing drivers affects the driver brace too.
I'll be taking a saw to a pair of ply sheets this weekend if all goes well !
Sounds fun! I also get that same plywood in 2'x4' sheets for small speaker projects, from Home Depot. More expensive than buying larger formats, but ideal for appartment dwelling with no real room for a stock of wood.
IG
IG
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Yes, very handy these panels. They also fit nicely in my car and are easy to handle. My MARTELLO (first version is a small desktop model) was designed to use these sheets, I get a pair of them from one 2' x 4'.
Great project. I will follow with interest.
However, quick glancing and excited waiting for the thread to load made me think that you were making a speaker from a single 2"x4". 😀 I gotta see this...
Those should sound very nice.
However, quick glancing and excited waiting for the thread to load made me think that you were making a speaker from a single 2"x4". 😀 I gotta see this...
Those should sound very nice.
build the driver braces for the deeper magnets, and add filler blocks if swapping to CHR/Ps IIRC, EL70 is approx 1/2" (13mm?) deeper than the CH's
I think this is based on the P10 MicroTower series, link to the full plan set is temporarily broken - when fixed should either be
frugal-phile.com/...microTower-maps-150909.pdf
or Dave can edit with new URL
When i was fixing the link i tool the opportunity to upload a version of the plans with a few minor updates:
http://frugal-phile.com/boxlib/microTower-maps-290412.pdf
dave
http://frugal-phile.com/boxlib/microTower-maps-290412.pdf
dave
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Here's how I might cut the parts from a single 2' x 4' sheet.
Note that with the mitre joints I will cut them at 45 degrees out of the sheet. This means that the parts can be sized differently (larger) than if I were to make a straight cut and then make the 45 degree edges afterwards (which would waste wood). Maybe this sounds complicated, but it's not - it just means you can scale the depth of the box slightly (1cm) depending on how you cut the pieces out and the size of the kerf of your saw. For me, the kerf is 2mm and things work out nicely as you can see. This is preliminary, the main pieces are good but I may use some of the left-overs to decorate the 'feet', create some cleats for the base, add some internal bracing pieces or whatever.
p.s. if you plan to use the planet10 drawings some versions of them have a formula for calculating the length of the port - the formula is not applicable to the MLTL that is described in this thread.
Note that with the mitre joints I will cut them at 45 degrees out of the sheet. This means that the parts can be sized differently (larger) than if I were to make a straight cut and then make the 45 degree edges afterwards (which would waste wood). Maybe this sounds complicated, but it's not - it just means you can scale the depth of the box slightly (1cm) depending on how you cut the pieces out and the size of the kerf of your saw. For me, the kerf is 2mm and things work out nicely as you can see. This is preliminary, the main pieces are good but I may use some of the left-overs to decorate the 'feet', create some cleats for the base, add some internal bracing pieces or whatever.
p.s. if you plan to use the planet10 drawings some versions of them have a formula for calculating the length of the port - the formula is not applicable to the MLTL that is described in this thread.
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Here are the basic dimensions, front view on left, side view (right facing) on the right. The port tube is not shown and I plan on a bit of trial and error to finalize it - but the design size is 50mm diameter PVC pipe, 14cm long. The driver support brace is shown in earlier posts as having a semi-circular cut out to clear the driver magnet - in reality this wants to be shaped so as to support the magnet and brace it to the surrounding box panels. I may decide to make a semi-circular clearance shape like shown, install it along with the driver and then install an adjustable piece to brace the magnet, to allow for different driver options after construction is finished.
Remember, the exact depth of the box (width of side panels) will depend on how the mitre joints are cut. Plywood thickness is 11.5mm.
Remember, the exact depth of the box (width of side panels) will depend on how the mitre joints are cut. Plywood thickness is 11.5mm.
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well I haven't found it easy making the 45 degree mitre cuts using a hand-held circular saw with pieces clamped on a workbench in my driveway, using a bag of salt for additional ballast. Most the pieces are now cut but test fitting shows that the mitre joints are not going to be precise enough for strong air tight results. Fortunately, I have a 45 degree edge trimmer bit for my hand-held router so I can clean up the edges - but it may be a bit laborious. This is what DIY is all about ! 😀
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the sides are lined up with the front baffle and the corners taped to hold them in place - then the glue is placed along the faces of the join and the sides are folded up to 90 degrees - the tape clamps the corners whilst the glue dries
the difficulty comes when gluing on the tops, I don't have clamps of the right size so we use the old standby, salt bags...😀
the difficulty comes when gluing on the tops, I don't have clamps of the right size so we use the old standby, salt bags...😀
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I nearly lost my mind doing some mitres this summer. You are brave to even try with a skill saw!
Kyle
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