Cab rehab for 3015

morebass! · #1 05-20-2010, 09:34 AM

I’ve been looking for inexpensive lightweight cabs for my 3015 drivers and haven’t had much luck so picked up some used PA cabinets on Craigslist that are about the right size.

http://pro-audio.musiciansfriend.com...FQ855wodxhYLNA

Don't laugh -they were $65 for the pair because one was blown and I’m taking out the drivers and horns. I’ve estimated the gross internal volume at 3.25 cu.ft. Subtracting 0.3 -0.4 for the driver, ports, bracing, and scoop handles gets me into the right range for this driver. But as you’d expect the construction is pretty weak - all 5/8” mdf/pressboard or whatever you call it and only one brace made out of the same stuff going from front to back semi-dividing the woofer area from the horn area. The two ports are 3” in diameter and extend about 3” into the cab. There’s also a rectangle where the horn was that I can either close off or convert to a shelf port. My questions are:

1) How should I brace? Some ideas: a) more front-to-back braces, maybe 4 of them at points where the drivers attach to the baffle; b) 1/4 round in all the corners glued and screwed; 3) diagonal braces along the back and sides. I’m wondering what is most weight efficient.

2) How should I port? I have no experience with modeling software that calculates this. I know Passinwind suggested modifying the TL606 plans to a 3” shelf port for these drivers. I can try to duplicate that since the cab volume is about the same. Or add another tube port and match the surface area and depth of the TL606 w/ 3 “ shelf port. Or is there more to it than that?

3) Where do you get T-nuts?

Any help is appreciated.

singlemalt · #2 05-20-2010, 10:37 AM

Subscribed.

Once you get them opened up take some pictures so we can see what's in there.

Looks like a cool project, for $65, you couldn't buy the materials for one cab project for that.

From the picture in the link, I think I would flip it upside down and treat the horn area as the port. Cover the round ports to take them out of the equation.

If you have the TL-606 plans, look at how they did the port shelf and runners, that will brace up that area.

I'd do one as a trial and get the bugs worked out. One TL-606/3015 does it for most of my gigs and all practices.

T nuts at most hardware stores, check your driver to see what size screw fits in the hole. 1/4 20 might be too large. But before you do that, can you get into the cab from the back? OR, can the front baffle be removed? If so, a washer and aircraft nut would do.

T nuts can be a hassle. I use a C clamp to press the fangs in, and then, either a small screw or a scrap of plywood with hole drilled in it, glued and stapled, keeps the t nut from getting pushed back in.

What have you got for tools? I would think that narrow crown staples would hide in the rat fur, you could glue and staple braces. I don't think 1/4 round in the corners would do much. Probably a combination of the TL 606 and greenboy's fEarful bracing to cut down on vibration. I used 1"x pine or fir scraps ripped to whatever width, 3" for port runners, maybe 2" for corner bracing.

Winisd is the program, I shoot my numbers over to Passingwind and he tells me if its a go.

Good Luck!

rpsands · #3 05-20-2010, 10:47 AM

For drivers as light as 3015s, if the baffles are plywood I would just add plywood backing (PL premium to hold it on) to each screw hole and use Recex screws instead of T-nuts.

I'll never touch T-nuts for Neo drivers again

singlemalt · #4 05-20-2010, 10:55 AM

Yeah, I didn't want to cop to it, but I just used sturdy rough thread screws to mount the the driver. Just as a test to see if it mattered, and so far its been no problem. They don't weigh anything and there are eight mounting screws.

I used T nuts with 1/4 20 machine screws to mount the grill.

Since the OP is looking to beef up these cabs, a plywood backer would do nicely.

morebass! · #5 05-20-2010, 11:06 AM

Thanks for your input guys. Sorry I can't provide a picture as my camera is in the shop. But there's nothing to see. Just 6 pieces of 5/8 pressboard and the one brace which is front-to-back 5/8" x 6". There's a crossover at the jack and a pole mount on the bottom - both will be removed. Can't tell if the sides are screwed, dado'ed, glued or what. There's no way to get in through the back. It seems pretty solid though, given the material used. I'll get a cell phone shot tonight.

Toolwise I have a table saw, staple gun, drill, cheap jigsaw, pipe clamps, wood glue and hand tools. I can rip some nice 3/4" maple flooring I'm trying to use up for braces. It's very strong and very heavy so I won't use much.

The baffle is pressboard and that concerns me. Maybe some pieces of maple or plywood placed behind the baffle at each point where the speaker is attached would do it. I think I'll put at least one more front-to-back brace in there.

I like the shelf port concept for three reasons 1) the added bracing; 2) they look cool; and 3) I don't have to cut a perfect circle

rpsands · #6 05-20-2010, 11:08 AM

Another thing I have experimented with us using poplar dowels (3/4" or so) as front to back bracing and as speaker hole backers. They are super light and very stiff, and not too pricey. Adds a lot of front to back bracing and gives you something to screw into

You can get round or square dowels quite cheaply from Lowes. I use the square ones as corner bracing.

If the MDF baffle is removable I'd remove it and get someone to cut you a 1/2" birch plywood baffle. Just my 2 pence. IF it's not, then just put some kind of backing on the screw holes and you're fine.

morebass! · #7 05-20-2010, 11:18 AM

Quote:

Originally Posted by rpsands

...I use the square ones as corner bracing.

Please elaborate on your corner bracing. Does it extend along the entire edge where two pieces come together or just in the corners where 3 pieces come together? This was what I was thinking of using quarter round for.

rpsands · #8 05-20-2010, 11:22 AM

I put a 1/2" or so square dowels along every seam (e.g. in every corner). With my 3/8" cab build it was basically required to have anything to screw into.

rpsands · #9 05-20-2010, 11:24 AM

You can see it pretty well there. I used full 1" dowels for the baffle backing and the plywood bracing from front to back lined up with the side screw holes of the speaker.

Mo'Phat · #10 05-20-2010, 11:26 AM

I like the idea of taking out the horn and using that space as the port...covering up the round ports, or installing a decent tweeter for some zing. I find the 3015 to be just fine in the highs. I slap, play with a pick and everything else that one would normally assume I'd need a horn or tweeter for.

morebass! · #11 05-20-2010, 12:12 PM

Quote:

Originally Posted by rpsands

You can see it pretty well there. I used full 1" dowels for the baffle backing and the plywood bracing from front to back lined up with the side screw holes of the speaker.

Some good ideas there. I may do the same for these.

FYI - I ran across some info on wood density.
(103 kg/m3) , (lb/ft3)
Maple 0.6 - 0.75 , 39 - 47
Poplar 0.35 - 0.5 , 22 - 31
Fir 0.53 , 33
Pine 0.35 - 0.6 , 23 - 37
Oak 0.77 , 47
Birch 0.67 , 42

Poplar can be half the weight of maple!

4Mal · #12 05-20-2010, 12:15 PM

mdf... gleck. I think the first thing I would do is load up a 3015 in one cab as the cab is now with the horn loaded and all. Reuse whatever came with the cab for speaker mounting. Disconnect the horn I guess. Then fire it up and listen to it. That might be instructive.

I might be inclined to see if I could retrofit a real baffle board. Section the old one out, fabricate some bracing in a similar manner to the TL-606 and glue & screw to that. You could then adjust it size wise for a traditional shelf port and go from there...

Sectioning the old baffle out might be a little tricky near the edge so ... leave say a .25" piece all around the outside. then mount your baffle bracing behind it and extending out say an inch from the cab sides. The glue you use to mount the baffle should seal it up well enough.

Note that there is a removalble hatch on the back baffle of some of Jorg Schroeder's cab's. The 21012 fer instance. That might come in handy for tuning if necessary.

I spell "Tee Nut" as "Hurricane nut". Hurricane nutz suck way more than Tee nutz and in this case that is a good thing...

singlemalt · #13 05-20-2010, 01:23 PM

I'd test the staple gun on the maple. It might be a bitch to drive staples into. You could use 1/2 marine ply for bracing ala Greenboy's cabs. Anything will do. Its a prototype.

The pictures above look great, better still if the top fit inside and was captured, but with a good joint the lid will do the same thing, prevent wracking.

I usually have the back completely captured, top and bottom held by the sides, and the baffle set in to hold the front edge from wracking. I use biscuits and glue, some staples, held back from the edge so I can round over, and lots of clamps to get everything square.

Some of my clamps are quick grip bar clamps, they can be reversed to push things against the inside of the cab and hold it while I staple from the outside. Keeps me from shooting my fingers if I get a "shiner".

The best cab build leave you with all you fingers!

morebass! · #14 05-20-2010, 03:10 PM

Quote:

Originally Posted by 4Mal

...Sectioning the old baffle out might be a little tricky near the edge so ... leave say a .25" piece all around the outside. then mount your baffle bracing behind it and extending out say an inch from the cab sides. ...

Are you saying to make the baffle flush with the existing MDF baffle? Not sure i can cut straight enough with my jig saw to make even a semi-tight fit. How about setting the new baffle inside of the old baffle so the new baffle would be between the old baffle and some new bracing? That might put the magnet pretty close to the input jack. It's a pretty shallow cab.

morebass! · #15 05-20-2010, 03:12 PM

Quote:

Originally Posted by singlemalt

...
The best cab build leave you with all you fingers!

Amen to that.

morebass! · #16 05-21-2010, 10:44 AM

I’m hoping to get something put together for a gig Saturday night so I’ve got to get going on this tonight. First of all I’ll need to get a decent port. I’ll close off the tube ports with a piece of plywood that should stiffen the baffle somewhat then I’ll go with Charlie’s TL606 plus 1” port recommendation (looks like it comes to 44.25 sq. in x 2.5” depth). The Nady’s horn is supposed to be 5x15 (I’ll verify the horn hole size tonight) so I may not have to cut the baffle to make something workable. Or it may be easier to cut a new shelf port. I'll use some plywood or maple to adjust the port size and achieve the 2.5" depth not to mention stabilize the baffle. That may be as far as I get by Saturday. If I have time I’ll put some front-to-back braces behind the screw holes in the baffle. That way I can use some longer screws and not rely entirely on the pressboard to hold the driver. I’ll screw the braces in from the back too. Would like to get both cabs ready by Saturday night as the gig will be in a big room.

morebass! · #17 05-24-2010, 07:34 AM

In a mad dash for the finish line I managed to get one cab ready by gig time Saturday. I ended up using 5x17x3/4" plywood going across the baffle between the driver and the port and to support the shelf port top. I also used 1/4" ply scraps to cover the old port holes and pole stand hole which also improved strength. The shelf port ended up at about 45 sq.in. which was Passinwind's recommendation. I was running out of time so I didn't do anymore front-to-back bracing as planned. I messed up the jack and ended up going straight from speaker cable to driver. Nor did I get the driver attachments improved. Lastly I forgot to put in damping material until it was closed up at which point I stuffed some in throught the port. Amid significant chaos due to my kids being kids, I tested it for 2 seconds and threw it in the car and took off. It looks pretty rough as I didn't have time to paint the ply. Given all this I wasn't expecting much. I brought my 1x10 Epifani along thinking I might have to rely on that.

To my surprise the rehab sounded great! It thumps low better than my mesa (2xTL606) did. I used both the rehab and the Epi and was a happy camper. Despite the fact that the rehab was blowing past my knees and the Epi was on the floor angled up at me the rehab seemed much louder. My B1500's EQ ended up with Bass at about 7, mids and high mids cut to about 3. Pretty scooped - but it sounded full, deep enough for 4-string, not boomy, and sat in the mix perfectly. The mesa 2x15 could get louder of course but I have to say the rehab cab sounded better for this particular room. Since the internal volume is pretty close to the Mesa's it must be the bigger port size that's doing the magic.

On the to-do list: 1) open it back up and staple some damping material in there; 2) Add backing to screw holes and install driver with T-nuts (couldn't find Recex screws or hurricane nuts; 3) put a real jack on it; 4) paint it black (you devils!); and 5) do it all over again for #2.

Thanks to all who have helped. I'll get some pictures when the camera is back from the shop and I've prettied it up some.