(Yet ANOTHER) DR250 Build Thread!

[Bill Fitzmaurice]

Back at home now, so no sketchup. When I tried to measure it, I just deleted the rest of the cab panels, leaving only the one I wanted. That way I could easily measure any dimension I wanted to. It sounds like you are actually inside the cab in sketchup... I cannot work out how to do that... as soon as I need to move a bit to get a better view, my centre of rotation is always somewhere totally different and I seem to end up rotating around the tweeter array 3objects to the left

The rotation will be around the entire content of the project, not just one small portion. The way to work with a de-construction is to click and drag on just one of the individual models, copy it, then paste it into a new project. Then when you pan it will be around just that one object, not all of those in the full model. This also insures that you won't inadvertently erase something in the original file.

[escapemcp]

Aah! Thanks for that Bill. That makes sense. I managed to avoid using Sketchup for the OT12s and T30s, but I fear that I will need to use it for these.

The problem that caused all of this need for Sketchup was that I had drawn out the first piece and cut the 2 parallel cuts, but now on the bit of wood, I had to cut the 2 angled cuts. There seemed to be 2 options... the red or the blue line. The red would mean that the 2nd side is smaller, and the blue makes the 2nd side bigger.

NOTE: The top and bottom parallel angles not shown, as you can see from my bad drawing that I've already cut those.

The pieces are now cut anyway, but it would still be good to know if I've got any sanding or excessive PL use to come

Oh, and back to sketchup quickly... if I measure this very piece that I am having the issues with, I just get the rough measurement (e.g. ~8"), so I have no idea if the bit I am measuring is smaller or bigger than 8". Any ways to measure this more accurately please?

Thanks for all your help!

[Bill Fitzmaurice]

Oh, and back to sketchup quickly... if I measure this very piece that I am having the issues with, I just get the rough measurement (e.g. ~8"), so I have no idea if the bit I am measuring is smaller or bigger than 8". Any ways to measure this more accurately please?

There's no point in having better than 1/16" accuracy measuring off the model because the material in the model is exactly 1/2 inch thick, while the wood you're using isn't. If it says approximately 8 inches then 8 inches is close enough.

[escapemcp]

Arrrghh! Thanks Bill for your reply, but I'm still unsure of whether to cut inward along the red line or outward along the blue line. Anyway, it a moot point (until next time) as I have already made the cut and moved on.



Made some good progress (as you can see). I have stopped using my circular saw for these small bits as I couldn't use the sled (due to the angles and size of the pieces). I have been using a mitre saw and it's been so quick compared to the measure, screw sled to wood, check measurement and then cut routine that I have to go through when using the circular saw. With the mitre saw, I just line up the piece using the laser, clamp it down and saw away. I don't even bother using the mitre on the saw, as that involves having to use trig to work out the angles. It has made my pieces much more accurate.

I have also discovered that my circular saw is 2 degrees out For a 13 degree cut, I actually need to dial in 15. Now that I have discovered this, I can see my builds only getting cleaner The horn sides were cut before I realised this error and this is why you see the clamps on the pictures - they bring everything into alignment with the throat divider (which I know is correct).

Along with my usual Euro-PL (Everbuild Lumberjack Glue) in tubes, I have purchased a big bottle of the glue in liquid form. It's pretty runny, which makes it only useful for gluing on the flat, but it's pretty cheap for the amount you get. I have set up a test piece to see whether it is as strong as normal 'gel' PL. I will probably use it for other stuff than the DRs, although there might be a few simple joins that this gets used for. Here's what I am on aboot:



Testing the glue:


Finally, I bought some saw blades off eBay (v.v. cheap) from some bloke who seemed to be selling lots of stuff from hos workshop. I got sent these:

I'm pretty sure I don't want to be using these for my DRs, but can I possibkly ask what these non-kerf blades are for. I'm pretty worried about using them, as without a kerf the blade could easily get caught in the wood and kickback or worse. Are these for saw tables with a riving knife?

Thanks for listening. Stay tuned for more soon.

[billkatz]

So did you use the blue lines? I"m pretty sure that's right.

The compound miter saw seems like the perfect tool for those cuts - it's a challenge to jig those cuts on a table saw.

[escapemcp]

I'm now home where I can go down and measure the horn of my DR - which is just a few steps past that. The outside (smaller side) is 8".

Ooh, hang on, that's the answer. Didn't spot it before Thanks Bill.

[escapemcp]

So did you use the blue lines? I"m pretty sure that's right.

Um... I forget! I will have to take a look tonight, but as everything is all glued up, it's probably too late now. I think when I have to cut the whole assembly down, that should hopefully cover up any problems Thanks again Bill, I didn't pull the info from your original message (above) as I must have been high or something!!

Moving on... urethane foam for the throat fillers: does anyone have any tips or suggestions on where to get this please. I am thinking of that expanding stuff, but I am not sure if that is right.

[Tom Smit]

Insulation foam board, perhaps? Maybe you can find a piece of scrap at a building site, or at a lumber yard.
Another option is to make it from wood.

[escapemcp]

Oh, that's easy. So it's just something that is non-porus? I may have some flight case blastazote (or whetever it's called) foam left. I'll probably use that if no-one sees a problem with this.

[rogerc]

... urethane foam for the throat fillers: does anyone have any tips or suggestions on where to get this please.

From a skip! There's always odd bits of foil backed yellow board around

[escapemcp]

Good progress today (& yesterday evening - I never got round to posting a build log for that). I managed to make the throat filler out of some plastazote foam I had lying around from a flight case build. I checked that it was closed cell by blowing into it. I remember making the cut-outs in it for the CDJs and mixer and wondering if it was worth saving it. Glad I did as the cutouts have now provided me with both my laser flightcase's insides along with these throat fillers. I have worked out that I can JUST make the fillers for the next DR... provided I make a clean cut... the fact that these are angled is what has allowed me to shoehorn them onto a 10"x5" piece, it's almost millimetre perfect! I am glad as I want the cabs to be as identical as possible.

I am at the stage now where I need the driver in hand. Looks like I am going to have to bite the bullet and get one. I will be gluing on the top and bottom before I get the driver, as I can still access the driver area with them attached, but then it's all stop until I get the 2510.

When I checked all my angles this morning after gluing on the baffle last night (Friday), I discovered that I had a 4° angle insted of 3° (between the baffle and the 'letterbox' pieces). When I was building OTs, I would have let that slide, but I am getting more accurate in my work now and it annoyed me. I used my 3° sled and cut it to size - perfectly 3° now. The 3° sled is just the normal sled I had left over from my previous build, but recut with a 3° angle - I figured I'll need quite a few 3° cuts on this build. The edge was very wobbly before the cut where I had kept catching it (how??!) whilst cutting, so the new cut has got rid of all of those undulations.

I checked my liquid PL mentioned previously, and it's good stuff. Certainly usable on the horizontal joints, but it's so runny, you wouldn't want to use it on much else.

Anyway, here's some pics for you all (clickable):


The top and bottom are not glued yet, they are just there so I could see what it looks like. I did start gluing the base on, but after 2 mins, I realised that the butt cheeks were not cut out. I could have cut them from the other side, but as the 5 min PL was only 2/5ths hard I separated it and scraped off as much gloo as I could. That's when I decided I had done enough and called time. You can also see that the throat fillers are glued in place, but there is no spacer as yet.

Can I possibly ask someone to post a pic of the sort of screws they use to mount the driver. I am unsure what to use. Is it possible to use tee nuts instead of the screws? I prefer the solidity of tee-nuts, although I do know the screws will work.

Very happy with the progress after 2 evenings and 1 day. I was never expecting the speaker to be this far along. It's so good to be back building again and smelling birch every time I go into the garage. I want the build to last as long as possible as it is so enjoyable... this has meant that on this build I am taking extra time and care to ensure that everything is bang on. OTOH I also want the build to be done quickly, so that I can hear them!!

[Tom Smit]

4mm x 40~60mm hex-head screw will be plenty. If it's a heavy driver like a Lab12/15, then 5mm dia. would be better. Use a hex-head because a socket will stay on the head, rather than a screwdriver slipping off and poking the cone.

Screws are plenty to hold a Lab12 when a spacer ring is used on top of the baffle, so you should be fine using screws.

[escapemcp]

Thanks Tom for the info

Day 4 and I'm flying on this build now. After yesterday's mess up of trying to attach the base before the butt-cheeks were cut, I started by building myself a jig for my jigsaw to cut the cheeks. Managed to secure the jigsaw in place on a bit of wood by using blocks around the base and then drove a screw in to it for my pivot point. I started the cut on my DR's base ... it started diverting from the line almost immediately. Upon testing on a bit of scrap (which is what I should have done in the first place), I discovered that the jigsaw blade was bending (quite severly) on the cut. I should have thought of this as the same thing happened when I attempted to build a jigsaw sled. In the end I cut out the cheeks by hand and after a quick touch with the sander, they look pretty good.

I did as much as I possibly could without blocking driver access. I therefore added in the extra butt cheek reinforcement half way down the back along with the rear cleats. I only just remembered just in time that I have a pocket screw jig now... you can see where I used it on the half moons in the first pic (below).



I also started the next cab. Nothing much to report here, except for that my technique is improving fast!! All the joins were better than 1/32" perfect Here's where cab 2 is now up to:


All in all a good day. Thoroughly enjoyed myself today. As I am so far ahead of where I thought I would be, I think I'm going to have to drop a ton (£100) on a 2510 driver tomorrow or I'm going to have nothing to do in a few days.

I will get the 2nd cab to the state of the first, and if the driver has not appeared by then, I think I may well start on the tweeter array. I have the jig left over from the OTop build, but I think I am going to build another, as I was never totally happy with it. It chops tweeters to the wrong height, which means that I have 14 tweeters in my Otops, rather than the normal 12. Now I could reuse it and build a 24 tweeter array in the DRs (an extra 2 high), but I think I would be better served by building a new one with my new-found skill and patience!

[escapemcp]

It's all been pretty quiet on the DR front the last few days. I have had a lot of calls from people wanting their computer fixed, so I have been snowed under doing that. At least it adds a bit of money into the kitty, which is now running v.v. low after buying a 3010MB today

A guy was selling a pair on eBay for £140 each + £10 P&P. I have therfore bought one of the 3010s off of him, and he is holding the other one back for when I get the money together. I actually almost missed this good deal, as I was under the impression that the HO was the one for the DR250... thank god I follow the mantra - re-re-re-read the plans, as it was upon a reread that I saw that it was the MB and NOT the HO. 2 seconds later I was on eBay checking if the two matched, as I suspected that they did - SNAP. When the universe lines itself up right in front of your eyes like that, you just have to walk that line.

As for the cabs themselves, I have just managed to mark out the top and bottom pieces, and the horn assembly is good to go, so tomorrow I will start with the butt cheek and top hat cut before gluing the top & bottom on. AGAIN, I'll have PCs to fix tomorrow night, so if I can get as far as I have mentioned, I'll be happy.

Just waiting for the postman in anticipation now.

Sorry for the boring update.

[escapemcp]

In my previous posts, I totally forgot to say how I made my throat fillers. I was running out of Plastazote, so had to cut them as a partial circle. To do this I marked up the piece of foam like so:



The dotted lines are lines/edges that you cannot see. On bits of card I created 2 circles of the required dimensions and then 'cut' the 2.5" bit out the centre of them (simply by drawing a line of the required width).

I then lined up the edge of this line with the edge of the bit of foam, and traced around the edge. I then flipped over the foam after tracing in the centre line (pictured) and drew the other circle on the other side. As the centre line is obscured, I actually made a couple of marks to either side of the centre line where the edge of the circle would be and used that to line it up. I could have cut a hole in the card circle also in order to get the correct alignment.

Once I had it all drawn out I could cut it with an exacto-knife extended as far as it would go. Once you get the right angle, it's pretty easy... just keep checking that both sides are hitting their lines and keep the exacto knife at the same angle.

My cut was made all the more difficult as I had to squeeze in another filler out of the bit pictured above. This meant that the 2 fillers actually touched each other along the 'slope', so I had to be very accurate when cutting that bit. If I had enough foam, I am sure it would have been a whole lot neater.

As for last night, I have managed to get the top hat cut and the horn assembly mounted onto the second base, as well as most of the glue removed from the horn area. Looking forward to getting home tonight, as I have a whole evening to get stuff done. I should have a decent update in about 12 hours.