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Guest atilsley

Tannoy GRF-Rectangular Horn

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Guest atilsley

Just spent some time ligning up panels for a new Tannoy GRF.

This is the first time I've used lovely Euro Birch from Yates (Sydney), which is a very high quality, void-free 19mm ply.....the veneer is American Walnut.

I'll add additional braching over the original design.

Plinths are 50mm.

Top and side panels very well mitred by Mr Plywood...so no external joins showing...as the sides run all the way to the bottom.

Rear panels fully rebated in...so no trim there.

For front trim, I'll either use Walnut thin veneer glue on veneer...or look around for some thin solid wood.

Heavy for sure, perhaps 60Kgs each.....fun project.

Monitor Golds get ready.

Andrew

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Nice work Andrew.

May have to visit the lucky bugger getting those ;)

Cheers, Earle.

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Guest atilsley

Spent today drawing up the plans on the inside of one wall of each cabinet. Use small wooden blocks as guides for when fitting the panels. I allow a 1mm gap for the blocks to apply very strong poly glue. Blocks first put down with simple pva.

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Guest atilsley

Glue up continues...note how the poly glue expands forming a very strong and expanded hold. Obviously, you don't want this near visible joins...but for the internal horn panels, I lay it on.

The small white blocks you see half way up the back panel are to mount a brace panel later.

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Nice work Andrew.

Did the ply come with the Walnut veneer or was it custom pressed?

It makes sense to use a veneer that looks good with a simple oil finish as spray finishing these horns is difficult.

I built some with Macassar ebony veneer and finishing the horn sections was a pain using two pack lacquer.

Walnut is one of only a few timbers that looks really good oiled in my opinion.Livos works really well.

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Guest atilsley

The veneer is laid up by Yates, who import the Euro Birch ply.

I steer clear of lacquers, unless using a pro third party to spray paint...otherwise, it's Bees Wax (which can include a stain in it for even easier application). Plus, for these Tannoys, the ye olde approach suits.

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Beautiful work Andrew

I have another pair of 15" Monitor Golds that I just obtained that are looking for suitable cabinets.

That American Walnut looks a treat.

I hope the sound matches the looks.

Andrew

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Guest atilsley

Andrew

If in Sydney, why not visit in about one week with your drivers....? The high density ply and extra bracing should make this speaker sound a treat.

Be loving to your monitor golds....they deserve the best of homes...! Putting them in standard ported boxes is akin to testing a Ferrari on parramatta rd in peak hour.

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Guest atilsley

Not a lot of time spare today...so I glued up the plinths. I use PVA for the corners as this glue very easy to work with and clean up...don't want any nasty stuff on the veneer. I use Selly's poly Aquadhere for the corner blocks, plus for mounting to the base of the cabinet (along with long screws). I've drawn up all the circles for the baffle and rear panel cutouts...but will leave the routering to another day. On Sat, I'll have Mr Plywood attend to some more mitres.

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Guest atilsley

Today, I routered the holes for the front baffles, glued them up...plus glued in the rest of the main panels. Boy, tough job with router on the thin layered and heavy duty ply. Burnt out one router bit...and took about 8 individual runs to get through the 19mm ply. I mitred the bottom of the front baffle at 45 degrees, then mitred the corresponding bottom angled piece to create a clean join for the veneer.

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Edited by atilsley

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Guest atilsley

hi andrew,

is that magnet holder behind the cutout for the driver?

henry

Yes, the design is odd, in thatthe rear of the driver protrudes through the second panel. See here -

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wow, thats cool!. almost similar to ORION decoupled midrange mounting. it works both ways i think, keeping the length of the horn, and minimizing vibration coming out of the woofer.

great design.

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Guest atilsley

Final internal pieces added today, with sound deadening. Will glue up sides tomorrow and add plinths.

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Edited by atilsley

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I love these threads but don't always make a comment. I have made a few speakers myself, but don't really know what I'm doing :P

I am curious about the use of that lovely veneer inside the box where you will never see it again though! Seems like such a waste, when you could have used cheaper non-veneered material. Is it a SQ consideration at all?

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I love these threads but don't always make a comment. I have made a few speakers myself, but don't really know what I'm doing :P

I am curious about the use of that lovely veneer inside the box where you will never see it again though! Seems like such a waste, when you could have used cheaper non-veneered material. Is it a SQ consideration at all?

evening jake , veneer panels are always layered up equally so there is equal tension on both sides of the board otherwise you will get a cupping effect and the panel will distort in shape and you have to use the same material both sides or there will be an uneven movement. some furniture fnishers will apply a finish to the never to be seen panel internally so as to minimise movement in responding to moisture in the air as would be the case with a coating on one face and not on the other.

regards,g.

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evening jake , veneer panels are always layered up equally so there is equal tension on both sides of the board otherwise you will get a cupping effect and the panel will distort in shape and you have to use the same material both sides or there will be an uneven movement. some furniture fnishers will apply a finish to the never to be seen panel internally so as to minimise movement in responding to moisture in the air as would be the case with a coating on one face and not on the other.

regards,g.

Ahh, thanks Guru. I suspected there was a valid reason for it. Appreciate your explanation.

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Hi Jake, As Guru states and also my veneer supplier, it is there to keep the plywood in balance, although there is usually a perfect side and a not so good side so it pays to inspect the veneer sheet before cutting. If you have ever painted a free piece of board on one side only you can often see the cupping caused by the different surface tensions acting. I manufactured a Pair of Dallas II speakers for a customer using the same ply and methods, but used new cat litter for the voids except for the lower void where i used oven dried river sand. I found this keeps the upper weight down quite and lowers the centre of gravity in an attempt to make them more stable.

http://s78.beta.photobucket.com/user/redver/library/Dallas%20II%20Project

Regards, Nick

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