BillFitzmaurice.info

I've been enjoying my autotuba for a number of years and now its time to start building again. I've had the drivers for a few projects collecting dust however pesky little things have been holding me back. Little things like losing my house twice due to floods, numerous surgeries and then to top it off I broke my right hand really good last summer. Well as luck would have it there seems to be a dwell in my misfortunes so I'm going to leap into this build before disaster strikes again.

My main goal is to replace/decimate 2 SRX728 boxes we have at the club. They did us well over the last 9 years however it wasn't until the kids started showing up with their PK rigs that it became apparent how weak they are, especially really down low. Knowing how much more articulate horns are over front loaded boxes, tubas I believe are my answer.

[spl width =650&height=450&fmin=20&fmax=120&dbmin=85&dbmax=125]T60W15DLab12+12,T45W24DLab12+12,T60W30DLab12X2+6,JBLSRX728+9[/spl]

In that chart I'm comparing 4 lab12 loaded tubas vs 2 srx728's. I added 3 dB's to the srx's because they can handle 80 volts ( 1 dB penalty for compression) vs 50 volts for the tubas. I know the SRX's can take 160 volt peaks in a live setting, but with EDM sine waves, 80 v is as high as they go safely. I'm really surprised by the T45 graphs. That peak at 35hz is astounding! If I were building subs that needed to be mobile then those are what I would build. However, this will be for a permanent'ish install, so go hard or go home, T60's it is!

My hardest decision was whether to go 4 slims and build them into the stage or not. Although it would be a super clean look, I'm hesitant on not being able to move them around or being able to add more to the pile if I need more output. In our club we have a major (+16 dB) resonance at 45 hz and being able to put the subs at the right spot in the no-go zone really helps with that as pulling 45hz out with EQ takes the life out of the music. They'll be in the way now on top, but at least I'm not committed to one spot and can build more if necessary for more output. That decision might come back to haunt me because now "artists" may insist on moving the subs to where they "look" better during shows. I guess you can't win them all.

I really wanted to go 39" wide dually's, but that dream was crushed as soon as I realized that my crosscut sled doesn't go that wide and with 5x5 sheets, cutlist tells me there wouldn't be efficient use of wood.

So with all the decisions made, 2 dual T60's @ 29" width it is!

First day was spent getting the table saw in order. After being underwater a year and a half ago for a few days it was in pretty bad shape. I took a belt sander to the top and a file to the miter slots and it cleaned up pretty nice. A few pits here and there but still very usable.



I figured a tune was in order so I took out my square and went to town.
First step was to check the fence, looks square to me:



Then I ran the square down the miter slot to check if the fence was parallel. It was a little off but a half turn on an adjustment screw got things back into place:



Blade looks square:



Next I checked to see if the blade was running parallel to the miter slots. I put my square in the miter slot and scored a mark on the square with a lucky tooth on the blade:



Then I rotated the blade to the back remembering the lucky tooth and checked to see if the mark lines up with the previous one:



Hard to see but the score mark lined up perfectly. After putting on a new 80 tooth blade I decided that now we are in business .

Off to the lumber store to buy 12 sheets of 5x5 1/2" Baltic birch. $40 a sheet, not too bad.



I made a sled out of MDF and an oak pushbar. I rounded over the top so that it is more comfortable on the hands and used oak runners glued in place.



I put a little chamfer on the bottom of the pushbar for a place for stray bits of sawdust to sit so the work piece would sit flush without bits of dust holding it away.



Using the table saw I cut 10 strips of birch ply about 3.5" wide by 60" length. I screwed 2 sets of 5 together and roughly marked out 5 lines. I raised the blade to half the height of the strips and using the sled I cut 5 slots in each. I just cut, moved the piece over a bit, then cut again until a scrap piece of ply would just fit into the cuts.



Taking out the screws and a little assembly and voila, my collapsible cutting table emerges:



Made the circular saw sled:



And finally glued up some strips for guideboards and then clamped them to a straight edge:



All that took 1 sheet of 5 x 5 birch ply, a 2' x 4' piece of MDF and a 4' length of oak.

I spent the next day getting the rest of my tools in order, shopping for bits I needed, etc.

Day 3 I cut out the top and bottom pieces, marked out the layout and cut the access covers out. I also cut down the ply to the sizes listed in the plans.



Test fitting the first panel before I glue:



... and that is as far as I got.

lookin good corona! I'm dying to hear your impressions once fired up.

Proper setup is half the battle. Nicely done.

Made some progress:

I cut out the baffles, mounted the drivers, checked for rub then ran a 27hz tone at 15v for 12 hours. They are very close to their final destination in the picture:



I mounted panels 1 and 2 and am just test fitting panel 3 before gluing:



I'm building 2 of these so after I screw up the first one I can then repeat my mistakes on the next:



If you look closely at the top box, bottom driver hole, I started that hole in the wrong spot, you can see where PL saved the day on the bottom left of the driver hole. With the baffle backer board and PL, it is a strong fix so no worries there. I never did that on the second box so maybe I am getting the hang of things.



After reading about another member mounting the braces first I decided to do the same. I cut them out, sanded them all the same size then mounted them using a newly acquired Kregjig. Man that is one quick and nifty tool. Took about 4 minutes to drill 4 holes in all six braces. Another 4 minutes to mount them. I drilled the holes on the bottom side so you can't see them. That was by mistake as it was hard to mount the bottom brace with the holes on the bottom where I can't see.



That's where I left off but I'll leave you with a few more pics:

Woofer porn:



Good thing Harley isn't watching:




This is only 2 days !!! Any tricks to have this disease gone by Friday??

hifibob wrote:lookin good corona! I'm dying to hear your impressions once fired up.

Me too!!!

LelandCrooks wrote:Proper setup is half the battle. Nicely done.

I think you are right. Things are starting to go pretty smoothly now.

Re: diseased hands...

No tricks to get rid of PL, except for a pumice stone (and that isn't that effective). In future, get latex/nitrile gloves and put them on whenever you even think of going to grab a tube of PL. Probably best to keep them on for a while after too... I've stuck my gloveless hands in squeeze-out enough times

escapemcp wrote:Re: diseased hands...

No tricks to get rid of PL, except for a pumice stone (and that isn't that effective). In future, get latex/nitrile gloves and put them on whenever you even think of going to grab a tube of PL. Probably best to keep them on for a while after too... I've stuck my gloveless hands in squeeze-out enough times

I have a box of those blue gloves. Working with them is like doing the other thing with those on; no feel at all although I'm paying for it now. I have to work Friday night upstairs with 350 customers . Maybe 6 hours in a hotub will work, it does for some of the "other" diseases, lol.

CoronaOperator wrote: I have a box of those blue gloves. .

I use the clear (well almost) ones. They are thinner and allow for good touch and feel. Pretty much leave 'em on throughout the gluing process. Change 'em often. No need to scrimp - they aren't that expensive.

Did some more work today:

I glued up panel 6, it was a breeze with the braces installed already. There was some warp in that panel and having the braces to screw/brad to really made that easy to deal with. I only had to put a guide board on the bottom where there was no brace. I should of just cut out an extra brace and temporarily put it in place.

Panel 7 was a different story. Without braces in that spot dealing with a bit of warp was a nightmare. I eventually managed to get it into place after a bit of .



I installed two speakon connectors in the mouth. I used a jasper jig (the big one) on the router and made two - 2 1/4" holes, then rounded them over with a 3/8" roundover bit. I made backer pieces out of scrap wood and drilled a 1" hole in them for the speakon then glued them in place.




Here is the other side. Not pretty but nobody will see in here as I am doing a full top.



I cut out some more braces then clamped them together and sanded them smooth. I used the Kreg jig again to make some holes, marked the panel, then installed the braces.



I was running out of time for the day so I decided to put some more braces on!



Funny thing is I was stressing about the braces the whole time as I remember with the autotuba, it was the hardest part of the build ... and then came the Kreg Jig Jr! You guys really have to get one of these. I can't speak highly enough of it. I would say I have less than an hour cutting and mounting ALL the braces in the build so far. Mounting them first also increases my confidence that the horn path is the correct dimensions as well and that any warps in the upcoming panels will be a breeze to deal with.



Last picture of the day. I think I can finally see some light at the end of the tunnel.

I really do like the 'braces first' method of construction that you (and others) have used. It seems like it is going to make for a more accurate build. Yoink... idea stolen for next build.

RE: Braces first....

Just make sure you test fit and mark their location well. Putting them in second you can slide them home. Putting them in first, they could be off a smidge and move the panel quite a bit. I put mine in first on my THT, but mocked each panel up and marked them all before gluing the braces down.

Nice looking build!

escapemcp wrote:I really do like the 'braces first' method of construction that you (and others) have used. It seems like it is going to make for a more accurate build.

Or not. If they're not perfectly placed the next panel will be out of kilter.