I taught myself a lesson today; good idea learned from experience

Hey All, I am maing a set of speakers for a friend similar to those found on this webite;
http://cardersound.tech.officelive.com/PurchaseInfo.aspx .
The dimensions (inches) are 72 tall, 12 wide, and 18 deep and I am using 3/4 inch cherry ply with cherry edging. There is a lot of edging in this project ( either 3/4 or 1/2 inch thick, depending on where it is used) and the first time I had to flush trim the edges I built jigs for the tall and wide side pieces (18 x 72). This was time consuming but I had an abundance of MDF to consrtuct the tall and wide jigs. Anyway, today I was about to build some more jigs to trim other panels. Since the panels were all the same height and width I thought "why not use each panel as a jig for its complementary panel". I made a sandwich using short scraps of cherry ply as filler, leaving enough space for the bearing guided flush trim bit to clear. Binding all four bords together at one time using handscrews I was able to rout most of the edges with one set up while still providing a very wide and stable surface for the router to glide over. It took a few minutes to rearrange the boards to get the edges that were not routed in the initial set up. This is the first time I had tried this but I was pleased that I did not need to make a new jig to support the router. I may try this later on when I have to make other projects with repeating patterns. Oh, by the way, Happy Chanukah to all of my Jewish woodworking friends. Marc
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Marc... check out this guy:
www.solen.ca
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Hey Robatoy, I was not able to display the page, but the Live Search told me they sell speaker components. I'll try them out at work today. Thanks, Marc

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And they sell complete kits. You build the boxes. All of them first rate audiophile quality. High efficiency aircore inductors, non polarized capacitors, wirewound resistors, First class crossovers of varying roll-offs right down to 24db/oct Linkwitz-Riley.(sp)
Madisound is also a good source for parts. They sell Morel drivers which are amongst the world's best. None of them are cheap, but assembled in a good design a $ 1K investment will give you a linear speaker of high power handling and very low distortion. Something you'd have to spend 4 times as much to equal it. http://www.madisound.com /
One thing about boxes. To stop the speaker box walls from resonating there is only one formula that works. Heavy and rigid. Mass is the only thing that stops acoustic energy from exciting speakerbox panels. Bracing can have good results if done in the right place. (Think sound post in a violin.)
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On Mon, 22 Dec 2008 05:22:24 -0800 (PST), Robatoy

...once upon a time my brother and I talked my dad into a $1200 (1966 bux) front for stereo equipment...2 speakers, an amp and a turntable. The speakers were Wharfdale W-80's...sand-filled cabinets IIRC...I sold 'em to a friend in the mid-70's and to this day he won't let me forget it...mass, brother.
cg
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You can also try parts-express.com . They sell speakers,enclosures and have a large DIY forum.
marc rosen wrote:

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I just run a mill file down the edge, cutting the excess banding with the side teeth and smoothing the edge with the face of the file, 3" to 4" with each stroke, more of a sawing motion rather than a draw file stroke. It's cutting right when the "burr" curls into a roll as you go. Cleaning up both sides takes about the same amount of time as measuring out the banding and ironing and rolling it tight. I just built six 7' tall bookcases of cherry ply this way, 31.5 lineal feet of banding on each. After the fact, I think *maybe* a special fence on the router table would have been helpful. Maybe next time if ever.
Hold the file handle loosely in your dominant hand, the end of the file between thumb and fore finger of the other hand, extending the tips 1/8" or so past the file so they act to hold the file off the plywood face. Wrap some duct tape around the end of the file to prevent any chance of mishap. Lead with the handle end by about 10 degrees, stroking mostly downward the full length and forward a couple of inches, keeping the file almost parallel to the board face, riding on the finger tips of the other hand.
For me, there won't be a "next time". Plywood shelves sag more than I like. They really need at least an inch of hardwood edgeband rather than simple edging. And I'm all for pre-finished ply after this. 3 coats of shellac and wax sucked up 3 lbs of flakes, for over 1600 sq ft and 4 full days of hand sanding, brushing, waxing, and polishing. In planning, I somehow missed the fact that each bookcase has almost 70 sq ft of surface that needed finishing.
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Hey Mike, Thanks for the suggestion of the file. I'm not sure if that would have been a benefit to me because some of these edges need to be jointed to accept a perpendicular mating edge and/or be exposed on the same board. By the way, I'm not familiar with a "mill file" but I just looked it up. I think I would not have the patience to properly dress all of the edges with that. nonetheless, I appreciate your suggestion. I still don't know how I will finish these as the customer has not decided (lacquer vs poly urethane vs shellac, etc) but I'm hoping the sanding and polishing won't drive me nuts. Marc

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"marc rosen" wrote:

SFWIW, there are two (2) common files, "Mill Bastard" and "Flat Bastard" with the flat bastard having the more coarse checkering.
Many years ago was taught how to flush trim laminate with a 10" flat bastard file when you couldn't get a router in place to do the job or it just wasn't a big enough job to grab a router..
Also quite useful to break and edge.
Buy several files, they get dull in a hurry when working with laminate.
Lew
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Ah - finally a subject I know something about.
I looked at the pix. They're certainly gorgeous looking boxes but I have a number of reservations about method and materials/. I presume you're well committed to what you've already done, so don't change that for Gordz sake but if you don't mind me airing my thoughts.. Basically if I were to build another pair for myself, these would be some of the consideration
Firstly, I'm not convinced about the notion of full range drivers, Impossible to move a sufficient air mass with a small cross-section, impossible to get responsive high frequency with a large cross section, basically. There are ways round this but they are compromises, of course, and always introduce non linearity, That may not be unpleasant and may well be a preferred choice if you like excitement more than pedantic accuracy - e.g. disco-ey rock rather than choral works... However.. I've not seen any frequency specs on the site, so assume that the 42 Hz is a 3dB cut off but have NO idea of the graph shape which I'll also assume to be very lumpy
They are quite light for their size, This would be a problem with an enclosed box or a reflex design, but these are horn-loaded, and so the _acoustic_ impedence is extremely low (nothing to do with electrical impedence, O.K.?) Not much energy is stored in the mechanics of the system,. It doesn't build up enough "breath holding" to suffer as much from panel resonance as more traditional designe. Nevertheless, I would still avoid natural wood for the panels (first choice would be flooring type chipboard - NOT mdf or ply) with plenty of lateral cross bracing which would kill any panel resonance without adding too much mass. I'd use ply for sound-reinforcement/public address speakers because of its durability.
Flush trim..
I know you''re all excited about having done a nice job of it... leave it that way. It'll be fine.
but If I were doing it all again I'd go for round-over of the largest radius I could fit. Sharp edges introduce diffraction. I can hear it quite clearly on mine if I move around much. It's not as bad as it could be as the baffle boards are carpeted and set into hardwood edging and the main surfaces are fabric covered, not veneered. They sound absolutely fabulous, but IF I ever move to a bigger house again I'll recut the baffle boards in block laminate "butcher block" round the edges over and veneer the sides. That way the sound can't get "snagged" on any corners (yeah I know, and I know what **** is going to say, but it's a reasonable analogy :-) ) The surround port hole on the website designs gives me cause for concern because of its intrusive profile (yes, I know it's rounded but I think we need to minimize the necessary evils of having to have an enclosing box rather than bolt on something cosmetic which will likely introduce new problems.)
I like horns. I prefer front-loaded designs for their attack, but all horns are very very "fast" if a little "shouty" I have a nice pair of altec lansing copies loaded with 300w celestions, and they are THE loudest things on the planet short of a space shuttle launch. Great for vocals and (ahem) percussion but they need separate bass rigs to bring the lower frequencies up to their level, and _that_ requires huge volume of cabinetry and about 3k of engine, so the compromise is generally to put up with the lack of kerboom rather than lug a shed-sized bass unit around. It does the job, but it's not "hi-fi" used like that.
Now I know that that's a LOT more extreme than the horns in your application, but to a small extent, the same compromises apply. I think you'll have a slightly lost bottom end and the midrange will be faintly like shouting through cupped hands. Don't misunderstand, I'm not saying they will sound bad. I AM saying they are unlikely to be frequency-flat. If you want flat, you need to go for transmission lines, not horns, and they eat power, need to be massive, rigid and they will dominate a room completely. TLs tend to impose their sound regardless of environment wheras other designs tend to "excite" the room and their sound will change dramatically depending where they are placed. The most dramatic example of this that I can think of is the KlipschHorn, which is another rear-loaded design but it uses the corner of the room it is in as the "inside" of the exit mouth of its horn. "I am your father, Luke!" rumble rumble rumble..watch all your windows fall out. Gorgeous things, but not really chamber music monitors.
Transmission lines.. Mine are (I think) 40 high, 13 wide and 18 deep and 110 lb each. I don't move them much. and I know someone who consider them "dull" - but that's from a guy with a Technics system that he plays with the loudness control on at all volumes.
I don't think your project will sound "dull" I think they are "objets d'art" rather than hi-fi components, though and that's not necessarily a bad thing. I am an ex hi-fi junkie. It was pretty obsessive, once upon a time but I'v calmed down a lot since going forCDs and er, MP3s. Now I listen to old time radio and don't care about the bandwidth.
Yeah, I'm waffling again but this is stuff I'm comfortable with, whereas I can't tell one end of a jointer from a jack. I'd have been rubbish in the war as a plane spotter.
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Hey Bored Borg , (you should change that to BOARD) Thanks for your comments. This is a project for a friend of mine who provided some detailed palns (including cutlist ) and lot of peripheral info on what materials to use. (He is a bug audiophile and has longed for a set of Frugel Horns for a while.) A few local speaker builders recommended MDF but my friend said playwood was the way to go. I'm sure you are aware of the extensive pathway inside these boxes. Your comment about rounding over the edges makes me think if that should also be done on the interior boards too. I'm still a long way from completion so any changes that the customer wants can take place. When it does get done I will find a way to get some pictures up somewhere. Thanks again for your comments. Marc
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MDF is by far the better choice over plywood, especially in a transmission line design. You need the flatness and stability of the material to be able to get a good fit between the side panels and the partitions. MDF is also a lot 'deader' that plywood.... and cheaper. Then, when the whole thing is done, clad it in some sturdy paper- backed veneer and have at it. What most Frugalhorn aficionados don't get, is that the single-drive cone throws a lot of high frequency energy back into the pipe. When you do a swept spectrum analysis you will see the comb-filtering effect of that. In a transmission line design, one should never push the woofer past a wavelength equal to half its circumference...of the actual cone that is. In a TLS design, you are pretty much forced to look at a 3-way design with the midrange seriously isolated from the 'pipe'. (And when you get into a tapered line, you better know your stuff. The dimensions are highly critical.)
I always get a kick out of the audiophiles who proclaim linearity "down to 20 Hz". Little do they know that they need a 60-foot room to develop one full wave at 20 Hz. Just about all the bass we experience in an enclosed room is 'effect'. I also love those clowns who try to shove a 101 piece orchestra, tympani's and all through an 8" driver...101 people, blowing and bowing and banging and plucking all at the same time.... reproduced with a 'real' 100 watt amplifier. OR, better yet, Eddie Van Halen's 20,000 watt PA stack, faithfully reproduced through a pair of iPod nubs. YeeHAW!!
Okay.. I'll shut up now.
r
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wrote:

Edge diffraction is quite visible when you do 30 and 60 degree off- axis linearity measurements (anechoic chamber). What many people don't realize, is that the off axis crap, is what fills the bulk of your room. That is the stuff that that comes flying back at you from your walls.
..and *I* should have read your expos about horns, etc. before I rambled on about TL designs. I had a pair of TLS 50's (white dot B 200 KEF woofer in a massive cabinet.) Then I yearned for a pair of TLS 80's, with that horrid B 300 odd-shaped wooftah... just to get stuck on Spendor BC 3's with a pair of Rogers LS3-5a in my bedroom. Naim amps, of course. I was happy until Peter Walker's ELS 63's hit the market. I was sold...gone..swept up.
Then I got tired of the screwing around with subs, active cross- overs,.. and hooked up with Dynaudio, and built many speakers. I still love the craft, but no more 'audiophiling'.. that's a frickin' disease.
Oh... and yes, I do like the 'crack' of a Klipshorn..*S* I even liked the Decca Ribbon horns...but liked them better with the horns cut off. Yup, pair of Klipshorns, BIG tube amp..and a Decca cartridge. Well, slap my granma.
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I just spentabout 40 minutes writing a long detailed reply to everything in this thread and wife pulled the main power switch to the house. Something to do with Chritmas tree lights or... something. Total f***** techno-ignoramus !!!!!!!
so sorry, I haven't got the heart to go through it all again just now
I'm off on out-of-town happytime (!!) in a couple of hours, so I'll bid you all a Merry Yule and festive Annus renewus.
Talk at you next year.
Be Good !!
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