acg Posted December 23, 2014 Author Posted December 23, 2014 To give any that are interested how the outer profiles are calculated have a look at the graphic below. You will notice that the curved shape of the profile template (the hatched area) is different to the desired shape of the outside of the horn. This is because of how it will be cut, which you will see later. The profile template is cut so that when I get the grinder with the wood-carving attachment running along the 3mm acrylic template that I don't have to keep it square to the centreline of the horn...I can twist and rotate the grinder and take off every bit of MDF it can reach and what will be left is the exact desired outer profile of the horn. Simple!! 1
niss_man Posted December 23, 2014 Posted December 23, 2014 looking good Anthony. Can't wait for the pics of how it will be cut as I just cant figure it out yet.
acg Posted December 23, 2014 Author Posted December 23, 2014 All will be revealed shortly Simon (has got to work first).
acg Posted December 23, 2014 Author Posted December 23, 2014 Have just ordered a Dayton calibrated microphone, Focusrite Scarlett 2i2 soundcard and the DATS (used to measure impedance, T/S parameters etc. for the old loudspeaker drivers I am using and LCR for capacitors, chokes, inductors, resistors etc.). It's getting serious now!! Will have to read up on software like REW, Holmimpulse, Arta and the like. 1
Rob181 Posted December 23, 2014 Posted December 23, 2014 I had better leave now...feeling all horny... Will be watching with GREAT interest... Come on cows...eat more of that new green grass...
acg Posted December 27, 2014 Author Posted December 27, 2014 Made the first wood dust today, hooray! Did not get as much done as anticipated but messed around in the morning welding some reinforcement to take some wobble out of the lathe and then cut a couple of sheets of MDF finally settling on a protocol to do the cuts: use the circle jig to cut about a centimetre deep with a 6mm bit then finish the cut with the jigsaw. The circle jig is screwed to the centre of each circle and the router dragged around anti-clockwise. In hindsight the circle jig should have been made to take the big router (not the small router) which would have make the initial cut quicker, but we were going to use the big router to finish the remaining 25mm of cut which has now been tasked to the jigsaw. Today the outer rings for the Upperbass Horns were cut and...wow...they are big...and beautiful in their own way. By tomorrow evening one midrange horn should be ready for undercoat, if not both of them depending on how long it takes to fabricate a bracket on the lathe to accept the profile templates for cutting the outside design shape of the horns. No photos today, maybe some tomorrow. 1
Silent Screamer Posted December 27, 2014 Posted December 27, 2014 $88 per sheet delivered. I got three quotes and DMK were the cheapest by a fair margin. Didn't think I was going to save too much more on that price. Good service from those guys. DMK stands for? I need about 6 sheets of 32mm MDF delivered once I get my CNC finished in the new year.
hochopeper Posted December 27, 2014 Posted December 27, 2014 DMK stands for? I need about 6 sheets of 32mm MDF delivered once I get my CNC finished in the new year. I'm guessing - http://dmkforestproducts.com.au/
acg Posted December 27, 2014 Author Posted December 27, 2014 I'm guessing - http://dmkforestproducts.com.au/ That's them. Thanks Chris.
Sierra Posted December 27, 2014 Posted December 27, 2014 This is a huge project ... so much wood work involved ... How tall will they stand once finished?
Silent Screamer Posted December 28, 2014 Posted December 28, 2014 This is a huge project ... so much wood work involved ... How tall will they stand once finished? Based on the dimension on page 1 guessing roughly 2 meters tall.
acg Posted December 28, 2014 Author Posted December 28, 2014 This is a huge project ... so much wood work involved ... How tall will they stand once finished? Somewhere about 2m is pretty right. If I experiment with an Injection Channel then over 2m tall for sure.
acg Posted December 28, 2014 Author Posted December 28, 2014 (edited) Did not get much done today...lost most of the day to friends. Here are a couple of photos of a midrange horn ready to go on the lathe. EDIT: correct photos this time Edited December 28, 2014 by acg 3
acg Posted January 4, 2015 Author Posted January 4, 2015 Have been very much sidetracked by the festive season and my best intentions of knocking out some big days on this project were effectively scuttled by the lovely distraction of friends, an early departure for a beach holiday and the corresponding belated return. Will spend tomorrow morning finishing all the cutting for the six horns and then see where I can find time to further modify the lathe so I can turn them all into shape. Learnt a good lesson today...had been borrowing a friends jigsaw for the cutting (circa $100 Makita) but this afternoon had to buy my own. I got a $120 Bosch and OMG this thing absolutely flies...I had been taking about two hours to cut out a full sheet of rings with the Makita but the Bosch does the same thing in about half an hour...tools certainly ain't tools! 1
ben54b Posted January 4, 2015 Posted January 4, 2015 Fascinating project. Very interested to see how these will attach to the lathe and how you use your profiles. I happen to have a lathe in dads shed. Hmmmm Sent from my iPhone using Tapatalk
svenr Posted January 4, 2015 Posted January 4, 2015 What family of horn contours did you use in the design?
acg Posted January 4, 2015 Author Posted January 4, 2015 What family of horn contours did you use in the design? Tractrix for all three pair. Needed to keep the mouth area somewhat under control so L'cleach were ruled out early in the piece.
acg Posted January 4, 2015 Author Posted January 4, 2015 I should add that I modelled the horns in HornResp and used the export function to import the profile into AutoCAD where I fitted a spline and modified the mouth so that it terminated properly at square to the centreline (HornResp does not quite get this right). I believe that the mouth termination could be of some importance, especially considering JMLC's efforts.
Silent Screamer Posted January 5, 2015 Posted January 5, 2015 Have been very much sidetracked by the festive season and my best intentions of knocking out some big days on this project were effectively scuttled by the lovely distraction of friends, an early departure for a beach holiday and the corresponding belated return. Will spend tomorrow morning finishing all the cutting for the six horns and then see where I can find time to further modify the lathe so I can turn them all into shape. Learnt a good lesson today...had been borrowing a friends jigsaw for the cutting (circa $100 Makita) but this afternoon had to buy my own. I got a $120 Bosch and OMG this thing absolutely flies...I had been taking about two hours to cut out a full sheet of rings with the Makita but the Bosch does the same thing in about half an hour...tools certainly ain't tools! A Makita should easily keep up with a Bosch. Bet you weren't using the same blades for both cuts.
niss_man Posted January 5, 2015 Posted January 5, 2015 A Makita should easily keep up with a Bosch. Bet you weren't using the same blades for both cuts.I agree. Have both makita and Bosch power tools and have always thought the makita's to be slightly better. A new blade does the trick.
Guest Posted January 5, 2015 Posted January 5, 2015 Wow, OMG and respect! Big project there. Will be watching.
acg Posted January 5, 2015 Author Posted January 5, 2015 A Makita should easily keep up with a Bosch. Bet you weren't using the same blades for both cuts. I agree. Have both makita and Bosch power tools and have always thought the makita's to be slightly better. A new blade does the trick. Same blades. Looked up the specs: the Makita is 450w with 18mm stroke; Bosh is 620w with a fancy pendulum stroke (whatever that means).
acg Posted January 5, 2015 Author Posted January 5, 2015 The two towers are complete! Apart from the supports for each horn, all the cutting is done. You can see the Upperbass Horn face down including its backchamber on top of which, and facing up, sits the Fundamentals Horn. The glued Midrange Horns sit at the base of the towers. While I was stacking these in the shed I grabbed the trusty bathroom scales and took some weights: Midrange Horn: 10kg each Fundamentals Horn: 25kg each Upperbass horn: 167kg each Upperbass Backchamber: 17kg each There is quite a bit of MDF to trim with the lathe so we will see what these all come back to. Then add paint, drivers and the supports for each. I was hoping for about 150kg for the UB Horn so that I have options stacking the channels on top of each other. Time to go measure the lathe so I can design a castor attachment that can handle the two larger horn pairs. 5
EV Cali Posted January 5, 2015 Posted January 5, 2015 (edited) Makita and Bosh both make good tools but your specs point to the Bosch being the better of these two. The pendulum stroke relates to the blade pulling back from the material on the non cutting stroke ,allowing the dust to clear and not clog up the blade . Just seen the pictures .In the words of DVP, Wow . Edited January 5, 2015 by EVcali
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