(Yet ANOTHER) DR250 Build Thread!

[88h88]

It's been a while since I checked on this thread, you're going great guns man, good work.

[Tom Smit]

Aiden, if you were to drill one hole for your PVC pipe (drill bit only, not with the hole saw), this would give you a marker for measuring. You could then measure, mark and drill guide holes from the back side. With the guide holes complete, you now have a straight line down when drilling from the front.

[billkatz]

If you have a drill press, also take a look at hifibob's alternative to nacelles. He doubled up the supports and then used pocket screws.

[escapemcp]

If you have a drill press, also take a look at hifibob's alternative to nacelles. He doubled up the supports and then used pocket screws.

I thought of this very idea last night!!

[rodney]

alternative to nacelles.

This would be an interesting thread of it's own.

[escapemcp]

Last night's progress:

One side on:



And the other:



I tried using the countersink + drill technique to make a hole for the small (10mm (3/8")) PVC pipe, but it didn't really work. Tonight I am going to try using my pocket hole jig. I was thinking about it last night, and I reckon those pocket holes are about the same size as my PVC pipe. If I could create a jig to hold the Kreg mini in place then that could solve all my problems. I've got plenty of 24" radius offcuts that I can use for this. If not, then I think I'm looking at dragging the whole array module into school and using the drill press. I'd rather NOT use the drill press method, as I may well not have access to it when I build the next couple of DRs (notice I said when and not if ). It would be annoying to have to use a different method on cabs 3 & 4.

That's about it for last night. I spent quite a while tidying up PL from previous work and also applying bondo, and we all know how much fun that is!!

[escapemcp]

alternative to nacelles.

This would be an interesting thread of it's own.

There's not a lot of love for those nacelles Admittedly they are the easiest method of attachment (and hence why they are in the plans), but this is one of the joys of DIY... if you don't like it (and you have read the plans to understand exactly what they do), you can alter it

[escapemcp]

Last night I was hoping to get the side on. As the cab is not totally square , I was hoping to use the sides to pull it into alignment. This meant that I wanted to use the 30 minute PL - mainly for strength, but it would also allow me time to get the alignment right. The plan was to apply the PL, then stand on top of the cab (as that lines it all up) and then debut the new brad nailer to hold everything in place whilst the gloo sets. I did notice a warp in the centre of the panel, so first job was to clamp that out:



Then I grabbed the PL, only to discover that the plastic had broken along the line between the top of the tube and the 'nipple' that you screw the application tube to. As a fix, I have attempted to epoxy the hole. To give it even more strength, I then epoxied the application tube onto the previous layer of epoxy on the hole:



I'm hoping that this will hold, although I reckon it's only 50/50 whether it will. I wanted to let the epoxy set hard, so I gave up on the idea of fitting on the side last night, and moved onto the tweeter array.

First I marked up the holes on the underside:



Then I drilled them...:



...all the way through:



This now gave me something to aim at. To further aid me, I inserted a screw into the hole on the sheath side, and cut a bit of pipe to the rough angle:



This then allowed me to mark up where the hole in the sheath should go:



I could then measure the extremeties of the hole from the trailing edge of the module and then mark up the whole module. The 2 lines in the previous pics are the result of this.

Then it was onto actually cutting the hole. I discovered what I thought was the perfect dremel attachment for this:



So with my 'dentists drill' attachment...:



...I proceeded to 'sand' the hole bigger:



Whilst this worked reasonably well to start, it soon started making burning marks. The sawdust was adhering to the sanding stone and making it smooth, and trying to sand with a smooth object just ain't gonna work (unless you are trying to start a fire)! This was the result on the first hole though:



I needed another plan, and having made the first hole allowed me to test a few things. I realized that I could use the drill to go straight through the sheath (perpendicular):



Once through, I could then start rotating the drill upwards, and that would create my channel for the PVC pipe:



In order to make sure I was on target, I used the hole through the tweeter array back as a guide for the brad point of the drill bit. It's kind of hard to see the hole in this picture, but it's there:



Once the brad of the drill was rotating in that hole and the drill was vertical, I knew that the required hole had been made. There was a tiny bit of splintering on a couple of the holes, but I cannot imagine that you wouldn't get some splintering even on a drill press. For the other side, I may clamp a scrap bit of bendy ply over the top of the hole, and that should eliminate the splintering

So after making 5 holes, it was time to break out the glue gun. It was hard getting to some parts of the tubes 'inside' the array, so I just gooped it on and let it run down the tubes. They are now totally encased in hot-melt, and not going anywhere The 'neat' side looked much better though:



A quick demonstration of how tight the screw/PVC pipe combo is:



There is no glue in the way of that screw, I took the screwdriver to it, and then it just fell down the hole. I was thinking of inserting a couple of pins just into the sides of the pipe. The screws could then never come loose when removing the array. This could work out to be a lifesaver if any work ever needs to be done 'in the field'.
OMG... just accidentally hit the power button of my PC and it shut down. Upon reboot Firefox restored my session and unexpectedly, saved all of this post! I wasn't looking forward to typing all this in again!! Thanks FF (& try doing that with IE )!!

Back in the garage it was getting late, so powertools were a no-no. I was going to sand the PVC flat, but instead I used an exacto-knife to cut off the extra pipe and glue. I used it at full length and bent it against the sheaths to get the cutline flush to the outside. This left a perfect looking hole/pipe combo:



If I had taken the sander to it, it would have probably caused the glue to re-melt (does hot glue do that?) and end up all over the sandpaper. The exacto knife was the perfect tool for the job in this case. As Bob Ross said "We don't make mistakes, we just have happy little accidents".

Tonight I will complete the tweeter array holes, and hopefully get at least one of the sides on. Then tomorrow it'll be the other side and soldering up the tweeter array, and then, FINALLY, I can fire these up and hear what all the fuss is about! Thank god it's the weekend, so I can play with it all I want (and at the volume I want )

[escapemcp]

Tonight's progress:

Managed to get the sides on. In order to straighten up the cabs, I applied PL, then put the side on and then stood on the side whilst I fired lots of brads into the joins to hold it squarer than it was. It's still a little wonky (1/8" off), but this cab was always a little off. The other one is much closer to square and should end up totally square by the time I am finished Side by side they both look identical and the angles are the same, but the bottoms touch whilst the tops don't.

Here's the cab with the sides on:



I also managed to get the array module finished. I then drilled the holes required for attachment to the main speaker and checked that everything was ok:



Everything was going well so far (a bad sign!). I then attempted to install the driver. 3 bolts went in fine, but the 4th just kept on jamming. I checked the bolt just by itself and sure enough, it still jams. I am guessing that some glue has ended up on the thread I was thinking of purchasing a thread cutter, but I don't think I have clearance to be able to insert it into the insert nut straight. The only option I have therefore is to back the insert nut out of the hole, and replace it. It won't be easy due to the lack of access back there, but I reckon it should just be possible. Thank god I'm a scrawny sod, which means I can just about squeeze my hand into the area behind the baffle. Hopefully with a new insert nut, I'll be back on track. That's a job for tomorrow though, as I was pissed off when I discovered the problem with my nuts. Doing anything in a pissed off mood is always a bad idea(!), so I'm going to sleep on it and attack it tomorrow.

I've also discovered that I need to PL some wooden blocks in behind where the array mounting screws go through the 'uprights' (to which the array module attaches). At present the screws go all the way through the wood, which means a non-airtight seal - not that this matters too much because of the tuning holes in the driver chamber. The extra stock will mean that the screws can bite into more wood, which will in turn provide a more secure mounting for the array module. The screws I am using don't have the best thread on them, so any extra help they can get could save the wood from 'stripping'.

So tomorrow may well be the day that I finally get to hear what all the fuss is about Can't wait, although I will NOT be rushing to complete it asap - when it's done, it's done and not before

[Grant Bunter]

Nice variation on a theme

My tubes were larger, because I was intending to use hex headed wood screws to pull the module to it's supports. The hex part itself measured 5/16".

While tightening up, they stripped out, so I inserted T nuts.

The older than mine style DR's relied on a sealed array. This version relies on the backing plate to seal the driver chamber. Even with ports, I'd be inclined to get the best seal possible.

Keep up the good work mate, you're getting close.

I'll be really interested to hear your side by side comparison of DR's Vs Otops...

[escapemcp]

Nice variation on a theme

Yeah, I always liked your variation to the nacelles. I did want to secure the array module with no visible sign on the outside (by having to remove the tweeter array to get to the attachments), but upon investigating, I couldn't find a good enough way. I therefore stole your method

While tightening up, they stripped out, so I inserted T nuts.

That's what I have been slightly worried about. May have to alter this then!!

The older than mine style DR's relied on a sealed array. This version relies on the backing plate to seal the driver chamber. Even with ports, I'd be inclined to get the best seal possible.

Yeah, that's what I figured

Keep up the good work mate, you're getting close.

Many thanks. About to start today, so hoping for some noise out of them at some point

I'll be really interested to hear your side by side comparison of DR's Vs Otops...

I know!... I saw you post a few days ago wondering what they are like. I'll try to post a video with some HQ sound at some point (I'm suprised no-one else has done this). The only problem is that I only have a Berry ECM8000 measurement mic, which needs phantom power, but I have nothing that can supply the PP (other than the DEQ and DCX! ). I may well get a little mini mixer or a condenser mic at the start of next month, so I'll be able to do the recording then - I guess the mixer would be the better option, as the ECM8000 will be flatter than any condenser mic.
Right... off to the garage I go

[escapemcp]

Grant,

Just looked at the pics of your tubes. You went much closer to the edge of the module, which I am wishing I had done now. One of my screws only just bites into the 'uprights' behind the tweeter module back (due to the half moon cutouts). I had to drill an angled pilot hole into the upright to ensure that the screw didn't just splinter the wood. I'll post a pic tonight to demonstrate this. Thanks for the method though... much better looking than the nacelles. I have also proved that it is possible to do these without a drill press... You just need lots if hot melt and bondo instead!!

[escapemcp]

Sitrep:
Managed to get the insert nut removed and a new one installed. Took over an hour to change that sucker!! Testing the removed nut shows that the bolt won't go all the way in... I think the thread is cross cut, although it's hard to see. So glad I went with the 3010MB now - a 2510 has 8 bolt holes rather than 4 and if it was one of the nuts right at the side of the speaker that had stripped, I am struggling to see how I could have ever changed it!! I guess that the top and bottom bolts would also be a bitch, as the horn throat would get in the way so you wouldn't be able to insert an Allen key into the nut 3010MB FTW

Quick question:
How much of a gap so I need to leave in the foam around the driver vent hole? What about the driver chamber tuning port?? I assume that if I cut the foam to the same size & shape as the tuning hole, it would effectively increase the length of the port.

Thanks, pics to follow later on this evening.

[Grant Bunter]

I would leave a gap in the foam behind the vent say 5-7.5cm squared. That vent has to breathe.

I cut the foam around the ports tapering away some, like cutting the foam at a 45 degree angle.
Firstly to let the port do it's thing, and to cut down visible foam.

Regarding the nacelles, I said it in my build thread, and I'll repeat it:
The method we have both used isn't a solution per se, as that suggests a problem.
I ended up doing what I did, simply because I couldn't physically make the nacelles happen.
I understood the concept perfectly, but when I put a block of wood/nacelle up to the module sheath, I couldn't picture how to make it look like what I saw in sketchup.
So I came up with another method.

Having seen others do nacelles perfectly still hasn't helped me with that...

[escapemcp]

I would leave a gap in the foam behind the vent say 5-7.5cm squared. That vent has to breathe

Hmm... when I ask questions on this forum, I really should check to see if someone has answered before ploughing ahead!! This was how I ended up doing it:



The reason for the large gap for the vent in the array back is due to the fact that I had a bit of egg-crate foam that when chopped in half, fitted perfectly into the area I needed to fill. I will add in a few bits tonight to provide a bit of a closer fit. In the picture above, you can see some areas where I had to give the foam a hair cut to allow me to fit the driver, and you can also see that it is all wired up - the tweeter connector block is hidden behind the foam, but you should get the idea.

Yesterday's job was wiring up the tweeter array. I didn't want to just solder up all the tweets, like I did with the Otops, but rather I wanted to test all the tweets and then solder them up. Here is my tweeter testing apparatus:



First, I tested them on the polarity-o-meter:



Out of just over 20 piezos, I found one that was the wrong polarity. I was also hoping to test for tone and volume, but all the tweets sounded slightly different, and my brain couldn't remember what any sounded like except for the last one tested. They all sounded like they were roughly the same though, so I continued:



This was testing for capacitance. Annoyingly I could not test for this using the probes, so I had to tin a wire which I then inserted into the slot marked Cx (you can see this wire running between the red & black terminals of the DMM). Is it normal that you have to jerry-rig DMMs like this to get a capacitance reading? The average reading was 190nF, the maximum was 220nF and the min was 170nF. I was only measuring to 2 significant figures., as I had no requirement to be any more accurate. The real reason for this accuracy though was that using the 20µF scale on the DMM meant that the 'pip' noise that the tweeters made when connected was louder - this was especially handy when the connection wasn't fixed on either end of both wires. I had to connect the wires until I heard the 'pips'. Once I heard the noise, I knew it was all connected and that I could take a reading. I couldn't remember what the capacitance values meant for the actual response of the piezos (I think Leland commented on this once), but as I was only checking for 'outliers' it wasn't a massive problem.

So at the end of this process, I had 22 tweeters marked up with their capacitance values:



It was then onto soldering up the array. I opted for the highest capacitance value tweets in the centre of the array (I assumed that these were the most sensitive, although listening tests didn't reflect this!) and the capacitance values then reduce towards the top/bottom.

Net result:


The new soldering iron makes quick work of this! It's so nice having the proper tools for the job

So now what the tweeter array was completed, I just had to fit it into the module (it didn't fit of course with the wires - sandpaper solved this issue!) and I could then test

I ran the 4 core from the back of the DR into the crossover in the nearby Otop and wired it all up. First impressions were that something was wrong - it sounded all anemic I discovered this was because the bass was turned down on the channel I was using on the mixer Second attempt was still not that great. I tested with a sine sweep and discovered a horrible rattling sound coming from the 3010. I thought that it may be due to crap collecting in the area behind the surround. Used the hoover, but nothing was there. I knew that the driver had to come out - something greatly simplified with the new 'bendy extension driver thing'. A minute later, I discovered the cause: when I had been nailing the side on, some brads had missed their targets and fired through the side and into fresh air. I had cut these off with a pair of snips and a couple of these had found their way to the front of the driver. They were sticking to the driver due to the magnet and then rattling like hell. I reassembled the box, and finally was getting a decent sound out of my DR. They are much flatter than the Otops 'out of the box', but I couldn't really tell much more about them as I could only listen to them on very low volume - it was 11:30pm at this time as the world cup final had delayed me a little I will give it some welly when I get home tonight and let you know what I really think of these

Here's how everything looked at close of play last night:



The more observant of you may just be able to notice that the cab isn't quite completed yet - I wanted to avoid rushing any jobs just to hear them for the first time. TBH, I haven't really been rushing on these like I did on the first T30 and Otop, so maybe I'm maturing (perish the thought!) and slowing down in my old age - or maybe I'm reminding myself the odd corner that I cut on those first cabs, just to hear them - nothing major, but it still slightly niggles me that I know I rushed the flanges on the first T30 and Otop.