Tom Mobley Posted June 24, 2006 Share Posted June 24, 2006 This will a multi-part article, I'm too tired to organize all the thoughts at once. I'll have some pics as it goes along. This project has been simmering for several months now. Originally they were to be Cornscalas, but that soon got lost in the shuffle. After many iterations they now are going together with double TAD 1601-A 15" LF drivers, JBL 2470 mids mounted on ALK Trachorns, JBL 2404 tweeters and Dean G crossovers in a custom Cornwall-based cabinet finished in figured Cherry veneer. The TAD drivers are 8 Ohm and will be wired in parallel. This was one of the sticking points of the original DBB design. We were going to use early Klipsch K-33 woofers, the square magnet style. Howsomever, two 4 ohm drivers in parallel present a difficult load, and Steve really wanted the efficiency gains of running parallel. A crossover design was created by people who know of such things, but it was going to be a little marginal. Also, problems arose finding 4 really nice virginal square magnet K-33s. One pair came up right away on ebay, but every set after that had issues of some kind. I was running multiple automatic ebay searches, but apparently it just wasn't in the cards. I recommended BECs new 15" woofer, but Steve wanted something a little more exotic. Looked at various thing, ended up at TAD. FS=28Hz, Q=.31, SPL = 97. Four of these ought to cook right along with Steve's 100 watt amps. JBL 2470 mids are selected. Several others were considered with TAD a strong contender. However, reading their spec sheets revealed that there were issues with claimed frequency response vs. recommended crossover points. They do have a driver that goes low enough and crosses low enough, but it's a 2" driver. ALK's Trachorns need a 1" driver. JBL it is. I'll show some pics of assembling these to Al's horns. Incidentally, Al's horns showed up as the most nicely packed audio gear I've ever received. JBL 2404 tweets were selected after some digging around. Beyma's were a strong contender but at the time of ordering Beyma USA had none and couldn't produce a dealer with a pair either. They claimed the latest run was on the loading docks at some port in Spain. Hello JBL. Anyway, it's 11:30, I'm tired and have to be at work at 6:30 for 12 hours so a couple sample pics will be uploaded and I'm going to bed. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 24, 2006 Author Share Posted June 24, 2006 Here's a comparo shot of a JBL 2470 and a K-55. I've seen guys claim that the JBL are only marginally better than K-55, but it doesn't look or sound that way to me. Cripes, first time I've posted a pic since the latest version of the forum software installed. How do you spell "ssssssllllloooowwww"? Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 24, 2006 Author Share Posted June 24, 2006 JBL 2404 vs. early K-77. Wow. The difference in sound quality is more pronounced than the comparative sizes suggest. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 24, 2006 Author Share Posted June 24, 2006 cripes, forum erroring out trying to post this: We are currently unable to serve your request We apologize, but an error occurred and your request could not be completed. This error has been logged. If you have additional information that you believe may have caused this error please report the problem here. anyway, try again: third try: a shot or two of the TADs. These things are nice. Really nice. But hey, for $725 apiece they ought to be. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 24, 2006 Author Share Posted June 24, 2006 front view Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 24, 2006 Author Share Posted June 24, 2006 and a piece of wood... Quote Link to comment Share on other sites More sharing options...
Def Leper Posted June 24, 2006 Share Posted June 24, 2006 I see the router sitting on top of the panel, but how do you cut those rectangular holes? Do you make a set of templates as guides? What tool do you use for the round holes? I'm familiar enough with using my router to know you're not doing it freehand. I'm asking because I've designed a pair of "sideways" speakers (side-firing woofer) based on the cornwall to use in my home theater system and I'm interested in some of the basic construction techniques used by someone who's done this before. That might be a good subject for a mini-article by itself. Even details that you might take for granted (like what type of router bit used to cut openings) would be helpful. Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted June 24, 2006 Share Posted June 24, 2006 Wow! If I only had the talent! Nice work, Tom! I'll bet these will sound incredible when done. Mike Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 24, 2006 Author Share Posted June 24, 2006 Def, I actually had the motorboards routed out on a friends CNC router. He owns a cabinet shop and has need for one of these things. I had to provide a detailed drawing so he could generate an AutoCad file with the dimensions. His machine doesn't route all the way through, it essentially digs a precision deep groove leaving about .025 of the back of the panel in place. Then I got them, flipped them over, drilled a 7/16" hole into the groove from the back and used a bearing guided straight fluted router bit to finish the cut and clean up the edges. I have a pic of that. His machine left a much rougher finish on the edges than I expected, ended up going over them several times from front and back to get things cleaned up nicely. Without the CNC machine I"m in the same boat as everybody else, using the typical router accessories available. I use straight edges to guide the router, I haven't used one of the compass type router base to do round holes yet, not looking forward to it either. Mike, there's probably a craftsman hiding inside you waiting to get out. Quote Link to comment Share on other sites More sharing options...
smilin Posted June 24, 2006 Share Posted June 24, 2006 Tom, Wow, now I am getting a woody[6]nice frikin components, hopefullywill equal, phenominal sound. Thnaks, looks like you are doing a fabulous job. Hope you get to hear them soon. BTW, how does the veneer look? Thanks again, I gotta get my room in order. [][H][6] Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 24, 2006 Author Share Posted June 24, 2006 Steve, I'll post a pic when I get home tonight. I can't get to the pics from work. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 24, 2006 Author Share Posted June 24, 2006 Here's a couple shots of the the veneer. It is a raw unbacked highly figured Cherry from www.certainlywood.com. Those who have seen previous projects by forum members will recall that this veneer is much thicker than the type sold already applied to a backing material. One thing I"ve learned is to make samples big enough to get a real idea what it's going to look like. This panel is 2' x 4'. Looking at this sample panel oriented as it is in the pic here's the rundown. The right end is a cookbook instant antique Cherry finish. Two dyes (American Walnut and Golden Fruitwood) mixed in a ratio, followed by a wash coat of shellac as sealer, followed by a black cherry stain, topped with a couple light coats of spray bomb Deft semi-gloss lacquer. Too dark for me, and it muddied up the figure (properly, Chatoyance). I'll pass on that. What's funny is it is exactly what it claims to be. right behind me as I took these shots is a 1906 Kranich-Bach 6' grand piano in, guess what? Cherry. It's a dead nuts match. Upper center is Cherry dye, wash coat, Cherry stain and spray lacquer. Not bad, still dark but not near as muddy. All of these have the Deft lacquer, it's very thin but helps get an idea of the final appearance. Center bottom is wash coat, Cherry dye and lacquer. Bottom left is shellac wash coat and Cherry stain with lacquer topcoat. It is really very nice, the pic really doesn't do justice. The wash coat prevents the stain from penetrating so much and muddying the figure. Upper left is just plain Cherry veneer with lacquer topcoat. This is really gorgeous also, but in general the public is trained to think of Cherry as a dark reddish color, which it is not naturally. I've learned that dye brings out the figure, stain brings out the grain but can muddy the figure. IOW, the usual series of trade-offs. The shellac washcoats are to keep the stain from over-penetrating. It's basically just a super blond shellac thinned 50/50 with denatured alcohol. Cherry can have varying absorbancy and get blotchy if colorants are used straight. Cherry also reddens and darkens over time, especially if exposed to direct sunlight. Considering the tendency of Cherry to darken over time I recommended the sample in the lower left of the pic to Steve. Washcoat, stain and lacquer. Since this is a custom build he gets to call it. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 25, 2006 Author Share Posted June 25, 2006 another angle, not as good a shot, but at least a different view. The forum software is killing the resolution and darkening the pics Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 25, 2006 Author Share Posted June 25, 2006 Def, here's the router pic I mentioned. I'm sure you're familiar with this type of deal. Worked great in this instance where all the heavy lifting was done by the CNC machine. Quote Link to comment Share on other sites More sharing options...
jwc Posted June 25, 2006 Share Posted June 25, 2006 Tom. Nice to finally see some results on this. I am a big fan of my dbb's. One thing. I am not worried about the the load of two K33's. Al thinks its more like a 3 ohm load when in parallel. I am beginning to believe this woofer loaded is 6 ohms. At Hope, my dbb's were running off VRD's w/o a hiccup. Sounded fantastic. I switched from the K55 to the 902 -8B's and also have the JBL 2404. The mid horn 511. The woofers are the new K33. Looks like you went with the ports under the woofer. Is it a corner cabinet or a square back end? jc Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 25, 2006 Author Share Posted June 25, 2006 the cabs are square back. I like what you did with the V backs, but Steve didn't want to be stuck with corner placement. I guess his room is not all that suitable. I should have more pics soon. Did those T-nuts show up? That sample bolt setup is a stainless steel buttonhead allen bolt. I use a lot of these on engines. they're nice for LS and Belle because I have allen head sockets that fit on a 3/8" drive extension. Make it easy to start the one on the other end of the cabinet, under the woofer. Quote Link to comment Share on other sites More sharing options...
jwc Posted June 25, 2006 Share Posted June 25, 2006 Tom, yes I got the T-nuts, thank you. I actually haven't opened them up to look at them but I will and probably get back to you on the EXACT use of them. Thanks for doing that little work for me. So tell me, what will be the height of that bass bin? I'm guessing 42"-44"? jc Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 25, 2006 Author Share Posted June 25, 2006 jw, The boxes are 48" x 25.5" x 22" O.D. They're a little smaller inside because of the double bottom. There's a separator for the individual boxes, port shelves and lots of 1.5" x .75" glue blocking. I never did think much of the 3/4" square glue blocking Klipsch uses, I doubled that too. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 26, 2006 Author Share Posted June 26, 2006 alrighty then. got time and energy to size these pics down some for posting. Straight up shot of the front of the box. the light spots up and down the sides are filled over screw heads. They go back into the 1.5" x 3/4" glue blocking. the triangular dark spots on the left side are just color in the grain of the oak faced plywood. Lots of work filling all the little low spots and holes. Every dam* one of them will telegraph through the veneer if not just about perfectly level. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted June 26, 2006 Author Share Posted June 26, 2006 another view Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.