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GM's MLTL with 416-8B
This build thread documents an MLTL cabinet build for Model 19 drivers, the Altec 416-8b, 811 horn w/802-8g. I also plan to incorporate a Heil AMT1 air motion transformer as a "super tweeter".
Discussion about this project began in this thread awhile back. The response curves of the "Model19.long" and variants are referenced there. The reason for delay on this are multiple but lets just say that life and different priorities got in the way.
For background: The foremost design goal in this build is to elevate the position of the woofer to accommodate my listening space and my belief that the woofer is placed to low in the original design. A stimulus to the build was the state of the clone cabinets I had that came with the Model 19 components, they were built with fir plywood and Formica finished baffles. They were not destroyed but given to another local Altec aficionado that has more patience and the ability to improve upon them. The MLTL alignment also provides for a lower box tuning and is in line with how I like bass presentation.
I do have a drawing done in Google Sketchup but don't know how to change the file extension to accommodate posting it up in this forum. Anybody that knows how to do this and could pass along the information, gets a big gold star.;)
Dimensions of the enclosure are 52 3/4" H x 21" D x 30" W. Enclosure volume is 16 1/2 cu. ft..This is basically the original Model 19 footprint with the height extended as per GM's modeling. GM also had a larger MLTL model along the same dimensions with enclosure volume of 19 cu. ft. but the additional volume of the largest enclosure doesn't offer that much more for the additional volulume so 16.5 it will be.
Note: I made a poor choice regarding materials when embarking on this, purchasing what I thought was a good grade of Birch Plywood from a local lumber superstore. Those sheetgoods had many voids and the plies were found to be of some other species. Buyer beware. I returned those sheets and am now using standard Baltic Birch, 5' x 5' sheets, 13 ply, purchased from a local hardwoods supplier and was able to check the origination of the product. These are the real deal.
I have sorted sheets at this point and will be cutting them to dimension, today. I'll try to keep this thread updated with my progress. Anyone with tips and tricks regarding the construction is invited to post up their thoughts and keep me from making any mistakes.
Thanks, again to GM for doing the modeling and consulting on this, I hope my efforts prove up to the level of his design.
http://www.hostboard.com/forums/hbmc.../2011/03/3.jpg
http://www.hostboard.com/forums/hbmc.../2011/03/4.jpg
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Re: GM's MLTL with 416-8B
You're welcome! As long as there's no air leaks it should perform as predicted if the driver's specs are close enough, and if not, then normally vent tuning can compensate. The rest then is just cosmetic. ;)
GM
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
GM
You're welcome! As long as there's no air leaks it should perform as predicted if the driver's specs are close enough, and if not, then normally vent tuning can compensate. The rest then is just cosmetic. ;)
GM
My usual procedure for sealing the cabinet is to use an adhesive on the interior seams, something along the lines of PL400, Liquid Nails, etc.. Since these panels are rather large, I will probably rip some small strips as corner gussets out of hardwood. Preliminary plans on bracing are to use vertical window pane type of braces and secure them into dados in the panel interior surfaces. I will try to keep the bracing towards a smaller dimension and largish cutouts so that I don't chew up too much realestate inside the cabinet. Any tips or caveats as to the bracing are welcome.
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
westend9
I do have a drawing done in Google Sketchup but don't know how to change the file extension to accommodate posting it up in this forum. Anybody that knows how to do this and could pass along the information, gets a big gold star.;)
The easiest method would be to export to an image file:
File -> Export -> 2D Graphic
I'm following this project with interest, in particular the bracing suggestions, as I am planning a (yet another) 604 MLTL build in the near future
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Re: GM's MLTL with 416-8B
Nice looking ply. Bet is was $$$
The results will be worth it, tho.
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Re: GM's MLTL with 416-8B
Yes, this is my preference too. With this stuff I don't bother with any corner reinforcement even with butt joints. All it really does is create HF 'hot spots' that can't be easily damped except externally.
High aspect ratio cabs have the majority of its acoustic pressure along its length, so boards ~70% of its axial length long glued on edge down its length is desirable and offset by acoustic or golden ratio so that they average out any resonances rather than sum. Tops and bottoms would be done the same and for large width x depth such as these, some more boards randomly scattered down its length with one vertical one to tie all six sides together to ensure it can't 'breathe'. Done right, one can use it to brace/support the woofer too. If you're set up to drill myriad random size holes to minimize weight/internal net Vb losses, one can just make an offset 'X' frame with a driver notch out.
From this we see that typical window braces aren't all that great for pipe designs from a technical POV, but if you use them at least embed them well into the sides to minimize pipe action losses along its axial length as well as space with using an acoustic or golden ratio.
GM
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Re: GM's MLTL with 416-8B
Westend9, Good Luck with your project. I see your in good hands with GM !! ;)
I finally got my woofers back from GPA after 2 months, so I'm back working on my cabs again. :D
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
Panomaniac
Nice looking ply. Bet is was $$$
The results will be worth it, tho.
Not that bad with a Contractor's discount;) MDF would have been my other choice but I hate the dust and it's lack of structual strength. FWIW, my lumber salesman was out a couple of weeks ago after I had the BB in the shop and told me they have a void free veneered plywood that is less expensive.
Quote:
Originally Posted by
GM
Yes, this is my preference too. With this stuff I don't bother with any corner reinforcement even with butt joints. All it really does is create HF 'hot spots' that can't be easily damped except externally.
High aspect ratio cabs have the majority of its acoustic pressure along its length, so boards ~70% of its axial length long glued on edge down its length is desirable and offset by acoustic or golden ratio so that they average out any resonances rather than sum. Tops and bottoms would be done the same and for large width x depth such as these, some more boards randomly scattered down its length with one vertical one to tie all six sides together to ensure it can't 'breathe'. Done right, one can use it to brace/support the woofer too. If you're set up to drill myriad random size holes to minimize weight/internal net Vb losses, one can just make an offset 'X' frame with a driver notch out.
From this we see that typical window braces aren't all that great for pipe designs from a technical POV, but if you use them at least embed them well into the sides to minimize pipe action losses along its axial length as well as space with using an acoustic or golden ratio.
GM
Very interesting. I will try to adhere to the Golden Ratio, then. Even though I had been thinking about corner gussets running the full vertical length and possible exterior trim embellishments on the corners, I guess I'll forgo those and use the adhesive only.
When you advise to use boards of "70% of axial length" is this in the vertical axis? IOW, if the interior vertical dimension was 52", I would place a small cleat (board) that is 36" or so, vertically, onto the interior side panel? Is it a good idea to stagger these from the bottom and top?
If material allows, I may use an x window brace as I believe it is the most ridgid way to tie all the panels together. Your advice about keeping the edge of the pane cutouts toward the side to minimize pipe action is noted (if I'm understanding you correctly). Lacking the material, I'll certainly install cross bracing to the single plywood center brace.
I plan to double the bottom and top panels. I have added to the all of the panels vertical dimensions so that volume isn't decreased. One panel of the doubled panels will fit inside the four vertical panels. This should also offer to square up the carcass. I will add a few small cleats if necesary, to tie the top and bottoms to the other braces and panels.
One thing I have been thinking about and I should know this is: where do I position the woofer? Is there any special or advantageous height that I should adhere to? My initial thinking is to get it as high as possible to mate well with the top-riding horn and increase the length of the TL. Advice, please?
This is all very cool, I'm quite excited to get it all together and take the Altecs for a run. I'm glad I have this board and GM to navigate.:thankU:
Figured out how to export the Sketchup file but it is not scaled, I'm learning.
http://www.hostboard.com/forums/hbmc.../2011/03/6.jpg
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
Altec Best
I finally got my woofers back from GPA after 2 months, so I'm back working on my cabs again. :D
Cool! I sent you a PM the other day, but hadn't heard back. I still haven't installed the HF phragms yet, the XO caps were trashed in the strike too. It even oxidized all the wiring from the amp. Thankfully, the electronics except for one tube in the pre-amp and woofers seem OK..............
GM
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Re: GM's MLTL with 416-8B
Well, a thick bead of PL400 is a pretty decent gusset all by its lonesome. I lay it in with a caulking squeegee..............
Correct, you want stiffeners running along the longest axis, same as a horn.
I use 1x3 boards on edge or similar size scrap plywood.
There's no real advantage to vertically staggering them and if you get them too close to one end you create a 'hot spot'.
Well, you're creating offset 'X' frame braces with the lumber ;), but if you prefer to make all those extra cutouts that's fine too. Me, I was always in a time crunch and never had any effective dust control system, so tried to minimize cutting as much as practical.
If used, minimizing how much they protrude in the airstream along the walls is to *maximize* pipe action.
Unless the bottom is raised up off the floor, doubling up the bottom is a waste of time/materials and even then, bracing is sufficient since all the pipe's pressure is concentrated at the closed end (top) and why the panel bracing is along its axis.
Except for the full length vertical brace to tie the top, bottom and all four sides together there's no need for any more tie bracing, i.e. the object is to not have any bracing near any corners as these areas are already self braced by having glued joints as well as unbraced areas too small to resonate with any consequence.
There is a mathematically 'perfect' position along a pipe's length to place the woofer for smoothest response, though while a good point, I disagree with MJK's axial length 'L' x 0.349; instead using a different formula that includes the pipe's cross sectional area (CSA), but never having compared the two, I don't know if the differences seen in sims using his software are audible except possibly with the most minimal of internal damping.
Regardless, since your HF horn is on top, unless you sit really far away, like > 25 ft, then placing the woofer right up at the top of the cab is best overall and it also maximizes pipe action, ergo max vent damping.
Yeah, believe it or not, I get excited every time someone builds cabs like I learned to do so long ago. By age 22 when I did my first pipe horn designs, I was already pretty jaded WRT to high performance/SQ sound, but these took them to another level of BLH-like without all the extra bulk/woodworking, yet with the smoothness of low Qt sealed with none of 'boom'/'flabbiness' of the BR cabs of the day.
Of more interest to me though was that such alignments caused much greater improvements with 'el cheapo' drivers and I'm glad that now with MJK's software, the various TLs and their mass loaded (vented) variants are the de facto alignments for so-called 'full-range' drivers and their woofer + super-tweeter variants.
For this we have RCA's Harry Olson's circa 1949 MLTL design for his LC-1 'full-range' driver to thank, though he just called it a reflex, and the college student working at Altec that mentioned it to me when I toured the plant that year.
GM
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Re: GM's MLTL with 416-8B
Thanks, GM, for iterating what must seem to you, like school yard stuff. I've never built an enclosure of this size so construction techniques need to be learned. Thank God, I have enough of my faculties still in place to absorb most of it. And, thankfully, there are still a few souls left on the Planet that are helpful.
I'm beginning to understand that anything that will not diminish the pipe action, WRT braces should be part of my focus. If I think of this as an aerodynamic exercise, removing as many surfaces that would cause an eddy or disturbance to the "airstream" would be good. Do I have a handle on this?
I do have adequate dust collection systems and cutting or machining lumber (and thereby creating sawdust) is also part of my everyday life. I tell customers, when creating sawdust, that it is not dirt and happens to be the main constituent of floor cleaning products. This is not always received as good information.:rolleyes:
I will do some calculations WRT as-built volume with braces added. I did size the first panels with a doubled top and bottom panel in mind but could easily forgo the doubled bottom. Removing the inset bottom panel will add about a .25 ft.^3 to the volume so it does have merit in that regard.
Thanks, also, for sharing your experiences at the advent of TL speaker design, priceless information, IMO. I have a pair of single driver BLH's and the designer reached the conclusion that much of horn's reinforcement was due to TL action and not from the horn, itself.
FWIW, I could not have picked a better time to launch on this project since we are caught up in a late winter storm that is making travel a struggle. It has been raining and snowing since last night and the roads are miserable. Staying in the shop and keeping the wood stove fired is a good priority, today.
Picture of woofer cutout marked---44" center from bottom of baffle.
Quote:
Originally Posted by
GM
Well, a thick bead of PL400 is a pretty decent gusset all by its lonesome. I lay it in with a caulking squeegee..............
Correct, you want stiffeners running along the longest axis, same as a horn.
I use 1x3 boards on edge or similar size scrap plywood.
There's no real advantage to vertically staggering them and if you get them too close to one end you create a 'hot spot'.
Well, you're creating offset 'X' frame braces with the lumber ;), but if you prefer to make all those extra cutouts that's fine too. Me, I was always in a time crunch and never had any effective dust control system, so tried to minimize cutting as much as practical.
If used, minimizing how much they protrude in the airstream along the walls is to *maximize* pipe action.
Unless the bottom is raised up off the floor, doubling up the bottom is a waste of time/materials and even then, bracing is sufficient since all the pipe's pressure is concentrated at the closed end (top) and why the panel bracing is along its axis.
Except for the full length vertical brace to tie the top, bottom and all four sides together there's no need for any more tie bracing, i.e. the object is to not have any bracing near any corners as these areas are already self braced by having glued joints as well as unbraced areas too small to resonate with any consequence.
There is a mathematically 'perfect' position along a pipe's length to place the woofer for smoothest response, though while a good point, I disagree with MJK's axial length 'L' x 0.349; instead using a different formula that includes the pipe's cross sectional area (CSA), but never having compared the two, I don't know if the differences seen in sims using his software are audible except possibly with the most minimal of internal damping.
Regardless, since your HF horn is on top, unless you sit really far away, like > 25 ft, then placing the woofer right up at the top of the cab is best overall and it also maximizes pipe action, ergo max vent damping.
Yeah, believe it or not, I get excited every time someone builds cabs like I learned to do so long ago. By age 22 when I did my first pipe horn designs, I was already pretty jaded WRT to high performance/SQ sound, but these took them to another level of BLH-like without all the extra bulk/woodworking, yet with the smoothness of low Qt sealed with none of 'boom'/'flabbiness' of the BR cabs of the day.
Of more interest to me though was that such alignments caused much greater improvements with 'el cheapo' drivers and I'm glad that now with MJK's software, the various TLs and their mass loaded (vented) variants are the de facto alignments for so-called 'full-range' drivers and their woofer + super-tweeter variants.
For this we have RCA's Harry Olson's circa 1949 MLTL design for his LC-1 'full-range' driver to thank, though he just called it a reflex, and the college student working at Altec that mentioned it to me when I toured the plant that year.
GM
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
GM
Cool! I sent you a PM the other day, but hadn't heard back. I still haven't installed the HF phragms yet.
Darn I didn't see it.I'm sorry GM, I had a look at it.You replied to an email I sent February 3, :eek: No wonder I had trouble remembering what it was about that was 7 weeks ago ! :D ;). Just Kidding you explained the last month were more health oriented. How are you feeling now ? I Hope Well ! It is always nice to see you on the boards.When I don't see you for a while I know your not feeling well.And that is Beat ! I'm glad to see up and around ! :lollipop:
I hope you get a chance to check those Frams out soon ! As I'm really curious as to how they sound.You don't hear much about those models too much.
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Re: GM's MLTL with 416-8B
Took some time, today, between errands and moving snow, to finish the cuts of all the panels except the interior braces. Looking at this stack of goods and imagining the final aspect of the boxes, if this speaker thing doesn't work out, I might drill some holes and ship myself South.:D
I will do some light trimming on the table saw and then proceed to vent and driver cutout. The original description of this MLTL design was to use a vent the same size as the original Model 19 and that would be positioned close to the bottom of the cab on the front baffle and centered, I would presume. I have the woofer cutout marked at 3" below the top edge. That will allow me to get a bolt into the frame of the woofer underneath the doubled top panels without too much trouble. I have established the diameter as 14 1/8" as per Altec's spec sheet.
One thing that is nagging at me is what I'm going to do for access to the interior and to provide for future vent modification. The latter isn't that critical as I am thinking of more than a few workarounds should that be necessary. I know GM advocated cutting the front baffle and that would certainly allow provision for access and vent mods but I am very reluctant to do that, mostly for cosmetic reasons. Would it be possible to use the bottom as an access port if I went to somewhat extraordinary measures to insure there is a tight seal at that point? I'm thinking of a neoprene or butyl high tech gasket material and through bolt the bottom panel into cleats or window pane of one the doubled bottom panels to accept the exterior bottom panel. Would I be better off, functionally, by using a purpose built access port in the back panel?
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
westend9
The original description of this MLTL design was to use a vent the same size as the original Model 19 and that would be positioned close to the bottom of the cab on the front baffle and centered, I would presume.
One thing that is nagging at me is what I'm going to do for access to the interior and to provide for future vent modification.
Would it be possible to use the bottom as an access port if I went to somewhat extraordinary measures to insure there is a tight seal at that point?
I presume also since I don't remember which of the many m19 variations I've done is the one you're referring to.
Yeah, a removable bottom is probably the best alternate since the sheer weight of the cab bearing down on the gasketing ensures a great seal. FYI, my gasket of choice is either NEMA 5/12 (dust/rain tight) or 3R (rain proof) Neoprene since one can drill through it and will self seal around bolt/screw threads. Not particularly cheap, but I've rotated the 515's individual baffles many times over the decades and still no air leaks as best I can tell, and this is with just large wood screws that are obviously not as hard to remove/replace as they once were.
GM
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Re: GM's MLTL with 416-8B
Whoops, your design for this iteration is discussed here.
In post #13 the sizes of the cabinet are discussed and the simulated responses of the stock 19 and two sizes of variants are in post #15. I am building the MLTL 19.long, the 16 cu. ft. model (we should, at some point, maybe give this a name ).
I will follow your experienced advice on the gasket material, I have access to just about everything. There will be some minor engineering and machining on the seal area. I plan to break out the router and table to cut dados and ease edges and so forth so cutting a dado to accept a gasket will only mean a bit and fence change.
Right now, I am squaring up the panels on the table saw. I still have the interior panels to cut, including the vertical window pane brace. For the support for the woofer's magnet, I was planning to cut the brace to fit around the magnet, recessed from the magnet > 1/8" to accept a strip of felt and to allow for shimming. Is this the usual way? I had planned to make two more window paned vertical braces to tie to the side panels. I think I can get away with this if I substantially reduce their area, i.e. mostly cut out.
An alternative would be to add hardwood cross braces from the center brace to the side panels. These cross braces could tie into other vertical bracing on the side panels. The vertical braces on the side panels could be dado'd to accept these cross braces and that would make for a good, secure joint. It is also a lot of time to do it this way. Another thing I've seen with panel bracing, mostly in older designs, is to position the braces on an angle across the panels.
Back to the saw!
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Re: GM's MLTL with 416-8B
OK found the sim and since no one has built one yet I've changed its name to 'Westend'. :D
Yes, though I use scrap Neoprene.
Yes triangulating panel areas really stiffen them up, just try to bend a triangle, but not a good plan for stiffening up TLs as we don't want the turbulence they would create.
GM
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Re: GM's MLTL with 416-8B
Lol, I like the name! I feel like I'm in the ranks of H. Ford, A. Bose or the much more revered T Crapper.:D
I am about to cut braces and two panels for the top and bottom. That will pretty well chew through the last of five sheets of plywood for those that are keeping count. At 65lbs/sheet, the weight of each cabinet, just the plywood, is 162.5 lbs.. I have an appliance dolly.
BTW, GM, no traingles will be forthcoming, I want this to be like the leading edge of the Darpa.;)
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Re: GM's MLTL with 416-8B
OK, we now have all of the panels ready for routing a dado to accept braces. Rather than chronicle in this Forum, the techniques used, I've posted a parallel thread at Audiokarma that shows some detailed processes of the cabinet build. I'm not going to leave the experienced Altec guys in this forum without build specifics but thought the Audiokarma crowd would benefit more from the tool usage and such.
Last night, after sweeping up, I decided to investigate further the Golden Ratio and how I could use it for the bracing. I actually went through the proof of the theorem to better understand how Phi is calculated. Since digesting the mathematics, I've come up with some numbers for brace lengths and placement.
My initial thoughts on bracing were to build "X'd" window pane braces, one to run vertically that would tie the front and back panel together and also support the driver motor. The other window pane brace would be halved to join the first brace and also run vertically, to join the side panels to the center brace. This would, in effect, tie all of the six sides of the cabinet together.
After reading GM's advice on keeping the disruption of sound waves to a minimum and the fact that I have burned through most of the BB plywood at hand, I've decided to keep the first driver supporting brace and to use a smaller vertical brace inset into each side panel. I will use three cross braces that will tie the vertical side panel braces into the central window pane brace from each side. This will also bring all six sides together and allow for the least turbulence inside the cabinet. All of the bracing will be inset into dados because it is easy to do and allows for the most effective joint.
The attached picture shows some detail of the dado and the insetting of a brace piece.
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
westend9
My Favorite plumber ! And his most famous invention the "Crapper Valveless Waste Preventer" :D
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
westend9
OK, we now have all of the panels ready for routing a dado to accept braces.
If you cut a dado in the middle of the panel, you have just reduced the stiffness of that panel. A better way to attach the brace is to use pocket screws and glue. Also, much easier than cutting a dado.
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Re: GM's MLTL with 416-8B
Yeah, for pipe designs there ideally should be no horizontal cuts or wide joints since the majority of the pressure waves are vertical and no sense in adding any more HF 'hot spots' than necessary, so as I previously noted, vertical boards boned on edge and maybe a screw or two (or air staple if one has the luxury) to hold it in place while it sets with tie boards to bind them together horizontally and one running the full vertical length to tie together all of them plus provide some driver support/mass loading. That, or use a vertical 'X' frame to 'kill all the birds with one stone'. One example: http://homepage.mac.com/tlinespeaker...aps-211010.pdf
I always did the former to use up scrap or used stock found at work sites or at the curb. I built a lot of cabs that had braces made from scrapped concrete former boards.
At one point I wound up with many hardwood closet rod, so made 'X' braces by tying them together with safety nut wiring with some PL400 as a bit of extra security because I had the appropriate tool. Today, I wonder if inexpensive tie wraps/PL400 or similar might not work just as well.
Anyway, I didn't own a router until some years after my peak building 'career' and frankly have only played a bit with the two given me, so while I can marvel at what some folks can do with them, it's just too much extra time for too little real benefit at the casual DIY level for me to bother if I ever get the chance to resume speaker building when butt joints and the occasional glue/screw block clamped with two or four picture framing clamps suffice. I shake my head in wonder when I see a complicated superstructure of varying size clamps to hold a simple rectangular cab together. I am big on diying jigs from scrap to streamline construction though, so I guess to each his own.
GM
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
Vint_age
If you cut a dado in the middle of the panel, you have just reduced the stiffness of that panel. A better way to attach the brace is to use pocket screws and glue. Also, much easier than cutting a dado.
There are adherents to different methods, and lacking the testing required to assess the merits of different joinery, I'm going with what I know works best for me. The underlying question of the structural integrity of these two methods would be: Does using fasteners and not creating a 1/8" dado have more structural integrity than cutting the dado and insetting the brace into the panel? I'm thinking there isn't much difference.
Quote:
Originally Posted by
GM
Yeah, for pipe designs there ideally should be no horizontal cuts or wide joints since the majority of the pressure waves are vertical and no sense in adding any more HF 'hot spots' than necessary, so as I previously noted, vertical boards boned on edge and maybe a screw or two (or air staple if one has the luxury) to hold it in place while it sets with tie boards to bind them together horizontally and one running the full vertical length to tie together all of them plus provide some driver support/mass loading. That, or use a vertical 'X' frame to 'kill all the birds with one stone'. One example: http://homepage.mac.com/tlinespeaker...aps-211010.pdf
I always did the former to use up scrap or used stock found at work sites or at the curb. I built a lot of cabs that had braces made from scrapped concrete former boards.
At one point I wound up with many hardwood closet rod, so made 'X' braces by tying them together with safety nut wiring with some PL400 as a bit of extra security because I had the appropriate tool. Today, I wonder if inexpensive tie wraps/PL400 or similar might not work just as well.
Anyway, I didn't own a router until some years after my peak building 'career' and frankly have only played a bit with the two given me, so while I can marvel at what some folks can do with them, it's just too much extra time for too little real benefit at the casual DIY level for me to bother if I ever get the chance to resume speaker building when butt joints and the occasional glue/screw block clamped with two or four picture framing clamps suffice. I shake my head in wonder when I see a complicated superstructure of varying size clamps to hold a simple rectangular cab together. I am big on diying jigs from scrap to streamline construction though, so I guess to each his own.
GM
Thanks for your reply about the bracing, GM. I believe we are on the same page as to the bracing and general construction techniques. Initially, I was going to build the bracing very close to the linked Pensil 12 cabinet. I changed my thoughts about that when considering the benefit and material use of the side to center brace window pane, combined with the obstruction they would cause to the pipe effect.
Instead, I am using two horizontal members joined to each side brace to tie to the center brace. It is, in some ways, more work, but I'm only doing this build once so I can rationalize the extra joinery required.
I'm fairly new to using a router but the ease of some operations make it a have-to-have tool for me now. It is like the advent of the battery powered screw guns, the epiphany being, "how did I get along without this sucker?"
I am just about done with the bracing, only needing to machine the center brace and ease some edges. Standby for pictures of a myriad of clamps.
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Re: GM's MLTL with 416-8B
I've done just about all of the router work, cutting the dados that accept the bracing and cutting out the hole for the woofer. Next will be tackling the center brace so I will tempoarily mount a woofer to get clearances around the woofer and establish good measurements for the magnet cradle. I still have to cut the vent openings, also. Should I position the vent in about the same relationship as the woofer, i.e. about 3" from the bottom of the front panel?
http://www.hostboard.com/forums/hbmc.../2011/03/7.jpg
http://www.hostboard.com/forums/hbmc.../2011/03/8.jpg
http://www.hostboard.com/forums/hbmc.../2011/03/9.jpg
http://www.hostboard.com/forums/hbmc...2011/03/10.jpg
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Re: GM's MLTL with 416-8B
I was able to put off making the central brace for just a bit by getting into fashioning an access hatch in the bottom of the cabinet. I cut an inner panel out and am saving the cutout. It will be edged with felt and bolted to the exterior bottom panel. The bottom panel will bolt into T-nuts that are inserted into the inner panel. To insure that the bottom is sealed, I routed a channel into the bottom of the inner panel and have an EPDM "D" shaped gasket that will afford a good seal between the two panels. The gasket should compress just enough to fill the channel when the two panels are bolted together.
http://www.hostboard.com/forums/hbmc...2011/03/11.jpg
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http://www.hostboard.com/forums/hbmc...2011/03/13.jpg
http://www.hostboard.com/forums/hbmc...2011/03/14.jpg
Bottom surface of inner panel:
http://www.hostboard.com/forums/hbmc...2011/03/15.jpg
The doubled bottom panels together:
http://www.hostboard.com/forums/hbmc...2011/03/16.jpg
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Re: GM's MLTL with 416-8B
I eased all of the edges of the braces on the router table, finished up on the SAH (subsurface access hatch) and cut the vents, today. This alignment called for the stock vent size of the Model 19, 11" x 2 1/2". I hemmed and hawed about where to position the vent, having read in another thread GM remarking that "near or at the bottom" is a good location. I left myself some wiggle room and cut the vent in at 2" above the front panel bottom edge. This is 1 5/16" above the cabinet inner bottom panel. That should leave me enough room to lengthen the vent, should it be necesary.
http://www.hostboard.com/forums/hbmc...2011/03/18.jpg
http://www.hostboard.com/forums/hbmc...2011/03/19.jpg
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Re: GM's MLTL with 416-8B
I am templating the center brace, any caveats......? I plan to leave a little over 1/4" of space between the driver cradle and the back of the woofer. I will shim this space to load the driver into the cradle.
http://www.hostboard.com/forums/hbmc...2011/03/23.jpg
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Re: GM's MLTL with 416-8B
OK, I believe I have a workable template for the center brace. I marked out the area where I thought the brace should not be cut to insure the most structural integrity. Using the information from GM's linked cabinet drawings, the Pensil 12, that "30-50% should be removed", I marked out the cut outs. I chose to use a diamond rather than circles since circles would be way to much time and expense in router bits. That, and I can't cut a circle worth a d*&^ with a jig saw.
The area directly behind the woofer could possibly have a bit more cut out. I will take a look at that area when I have wood cut and not working off cardboard. When I have all the cut outs made, I'll ease all of the opening edges with a roundover bit.
Am I forgetting anything?
http://www.hostboard.com/forums/hbmc...2011/03/24.jpg
http://www.hostboard.com/forums/hbmc...2011/03/25.jpg
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http://www.hostboard.com/forums/hbmc...2011/03/27.jpg
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Re: GM's MLTL with 416-8B
How do you plan to support the driver vertically?
GM
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
GM
How do you plan to support the driver vertically?
GM
Hey, GM, I don't think it shows up that well in the pictures of the cardboard template but I cut an opening (a cradle) that will be 1/4" larger than the magnet. There are two small corners that will support the magnet and the back of the magnet will be loaded against the center brace with a shim. Attached is a picture of the cradle cutout transcribed onto the yet-to-be-cut center brace. Do you think it needs more support that this? I could make two half "rings" to attach to the brace, holding the magnet very securely.
I am trying to keep everything non-essential out of the inside of the cabinet. Last night, I did some calculating using numbers for the area displaced by the center brace that were a bit optimistic. My new calculations give an internal box volume, calculating for everything in the cabinet, including the 416, to be between: 16.323 -> 16.466 cu. ft.. I believe this is very close to the original design criteria of 16.4 cu. ft.. I did not calculate the roundovers on bracing nor the air spaces in the frame of the woofer into the calculations, extracting the volume by a solid cone of it's measurements.
Anything I am missing in the build, so far? Do you think the vent placement wil be allright? I know it might need to be adjusted as to the room or the performance of the woofer. One last question, please, about stuffing the line. I've read some folks have used sheet fiberglass (OC 703 or similar) with good results but are there any other materials I might use for the stuffing?
Thanks for all your help so far. I would be lost on most of this without guidance.
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Re: GM's MLTL with 416-8B
Greets!
You're welcome!
No, I missed the 'step' in the cutout.
Not really, just stick some thick enough felt or similar pads on the 'steps' to snug it up.
At 16+ ft^3, a couple of 10ths off either way isn't audible.
I guess not other than I don't see any provision for easy vent tuning. It's location is fine.
Yes, this is my insulation of choice same as Altec after the asbestos laced Celotex was outlawed. Many manufacturers, DIYers use polyfil and the material properties MJK uses in his software with lamb's wool being considered the Rolls Royce of speaker damping.
Then there's open cell foam now that they've learned how to keep it from dissolving over time. I've experimented with open cell sleeping pad since it's so cheap at the local Wal-Mart, K-Mart, Cloth World or similar 'big box' discount stores. No doubt there's other materials out there and seems to me I read something awhile back about 'green' ground up T-shirts or jeans or some-such, so with each of these having radically different damping coefficients, you would have to experiment to find the optimum amount.
Just don't use closed cell foam..........
GM
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
GM
Greets!
You're welcome!
No, I missed the 'step' in the cutout.
Not really, just stick some thick enough felt or similar pads on the 'steps' to snug it up.
At 16+ ft^3, a couple of 10ths off either way isn't audible.
I guess not other than I don't see any provision for easy vent tuning. It's location is fine.
Yes, this is my insulation of choice same as Altec after the asbestos laced Celotex was outlawed. Many manufacturers, DIYers use polyfil and the material properties MJK uses in his software with lamb's wool being considered the Rolls Royce of speaker damping.
Then there's open cell foam now that they've learned how to keep it from dissolving over time. I've experimented with open cell sleeping pad since it's so cheap at the local Wal-Mart, K-Mart, Cloth World or similar 'big box' discount stores. No doubt there's other materials out there and seems to me I read something awhile back about 'green' ground up T-shirts or jeans or some-such, so with each of these having radically different damping coefficients, you would have to experiment to find the optimum amount.
Just don't use closed cell foam..........
GM
Thanks, I feel like I'm on the right path with the bracing, cabinet volume, and such.
The linked Pensil 12 cabinet literature states, "Adding this bracing can be as much work as the whole rest of the cabinet but really helps to get the last bit of performance..." and I can agree with work assessment, I just drilled 42 --9/16" holes in one brace and had to stop to let the drill cool off.
I will weigh my options on the type of stuffing to use. If I can source the 703 sheet fiberglass, that would probably be my first choice.
I don't mind recutting the vent to a larger size or adding vent length should that be necesary. I may want to do some cosmetic treatment to the outside of the cabinet so covering part of the vent, also, would not be that big of a deal.
I am thinking of building a frame to aid in the assembly of the cabinet. Maybe a square of 1 x 4 with slots cut in two pieces so that squareness can be adjusted and dimension changed to accomodate any discrepancies of the cut panels. I think I have all the dimensions correct....;)
Thanks, again for your time with this.
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Re: GM's MLTL with 416-8B
West, Looks like your moving right along ! :2thumbsup: :coffeedrinker:
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Re: GM's MLTL with 416-8B
You're welcome!
Yeah, and why I used individual scrap pieces and 'wired' them together. Much easier, quicker for me.
OC 703 or similar (AKA duct board) is made primarily for insulating heating/AC ducts, so at least in my locale can usually be bought from an installer; or in my case I lucked up and scored a pick-up truck full of 2x2 ft squares of it for the cost of hauling it away from a local installer that had a large, specialized contract go sour.
Another time I cruised past a different installer and got a bunch of large sheets of it with aluminum foil backing out of their dumpster, large enough to give me a ~ lifetime supply of replacement under hood insulation liners. Wire, in my experience, it can be bought by the pound for just a little more than scrap value from a reclaimer.
Again, an adjustable picture framing jig is all you need. You can make it using four store bought clamps or routing out blocks of wood mounted up on an old interior door left at curbside. Now you're ready to 'rock n' roll' with just a couple of sawhorses for 'peanuts'.
GM
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
GM
You're welcome!
Yeah, and why I used individual scrap pieces and 'wired' them together. Much easier, quicker for me.
OC 703 or similar (AKA duct board) is made primarily for insulating heating/AC ducts, so at least in my locale can usually be bought from an installer; or in my case I lucked up and scored a pick-up truck full of 2x2 ft squares of it for the cost of hauling it away from a local installer that had a large, specialized contract go sour.
Another time I cruised past a different installer and got a bunch of large sheets of it with aluminum foil backing out of their dumpster, large enough to give me a ~ lifetime supply of replacement under hood insulation liners. Wire, in my experience, it can be bought by the pound for just a little more than scrap value from a reclaimer.
Again, an adjustable picture framing jig is all you need. You can make it using four store bought clamps or routing out blocks of wood mounted up on an old interior door left at curbside. Now you're ready to 'rock n' roll' with just a couple of sawhorses for 'peanuts'.
GM
My soul is singing and everything seems right in the world when I discover that I am not the only recycler/reclaimer on the planet. The stuff that is landfilled in this country is unforgivable, IMO. My main occupation is in the construction field and we are noted for landfilling a large percentage of materials, estimated 15% of what is brought on site is disposed of for a residence. This week, I reclaimed two aluminum 8' gear rack sides and associated hardware. I will certainly focus my recycling efforts on the HVAC crews for the duct insulation because of your descriptions.:D
The door use is just about what I had in mind, something to offer a jig for panel assembly because the panels are so large. I have a lot of lumber around and many clamps so I could build an assembly jig with no material outlay.
I am finishing up on the center braces and will post up some pictures of the finished braces when complete.
Edit: Well that was one task that was easier than I had assumed. I bought some new blades for the Bosch jig saw and had at it. I routed all of the edges except the woofer cradle with a 3/8" roundover bit and gave it a quick sanding. The layout and templating took twice as long as the actual task, lol.
http://www.hostboard.com/forums/hbmc...2011/03/28.jpg
I am now considering what I will do by way of a jig for assembly. The snow is just about gone so my stacks of boards are appearing in the back fourty. FWIW, GM, I still have a couple of thousand feet of 1 x 8 redwood plank that was once a fence around a McDonald's parking lot. They had half the parking lot full of the fence when I arrived and a quick question to the manager and the fence became mine.
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Re: GM's MLTL with 416-8B
Made a couple of clamping jigs to ease the assembly procedure, nothing fancy, some scrap I had from this and other projects.
I started the glue-up with the side panel braces. I'm using Garret-Wade's 202-GF glue on recommedation from my BIL, the furniture builder.
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Re: GM's MLTL with 416-8B
I glued five sides of the first speaker and the braces in, today. The small clamping jigs I made worked out well. I had two snafu's: the center brace was too long, I took the measurement of the length from the wrong panel, I guess. A saw fixed that. Also, I nearly premanently glued in the bottom hatch. Luckily, I remembered that I had spread glue on the center brace where it meets the bottom panel. I unscrewed the hatch and set it aside.
I filled all the joints where the panels meet with PL400 construction adhesive. No air leaks in this cab.
Tomorrow, I will get some stuffing in the cab and glue on the front.
http://www.hostboard.com/forums/hbmc.../2011/04/1.jpg
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
westend9
My soul is singing and everything seems right in the world when I discover that I am not the only recycler/reclaimer on the planet.
Yeah, there's a few of us around, though probably the world's majority reside in Japan. Like many of my generation, I was raised to be a recycler up to a point, but when I became aware of what they were doing at the J.A. Pan, Co. back in '66, it really 'lit a fire under me' on the subject.
Only 15%?! That's really low compared to my locale, though in the past decade it's gotten better. Until legislation makes it a huge finable offense that gets tacked on to property taxes if they fail to recycle, the average American isn't going to bother. Heck, around here if you want the city or county trash collectors to pick-up recyclables you have to pay via property tax assessment for the privilege even though they get paid by the reclaimers!
I really wonder why I bother though. I mean just one illegal alien or otherwise 'indifferent' family around me dumps more recyclable paper, cardboard, glass, plastic at the curb for trash pick-up in a week than I reclaim in a couple of months and there's many thousands of them in a ~5 mi. radius.
Looks nice, but I swoon at the thought of spending so much time on woodworking I can't see. Different strokes............
A Mickey D's with a Redwood fence?! Don't recall ever seeing such a luxury at any 'fast food' emporium around here. The only Redwood I've scored is [7] 1x8x96" rough sawn planks that's been collecting dust in the shop for right at 34 yrs now. Now that I know I'm probably stuck where I am till I'm good as gone, guess I ought to use it up on that fireplace I'd considered way back when now that firewood, as expensive as it is now, is cheaper than electrical or natural gas heat around here.
GM
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
westend9
I'm using Garret-Wade's
202-GF glue on recommedation from my BIL, the furniture builder.
Interesting, wasn't aware of a glue with such properties. Will come in handy for a couple of furniture repairs I need to do.
Thanks!
GM
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Re: GM's MLTL with 416-8B
Quote:
Originally Posted by
GM
Yeah, there's a few of us around, though probably the world's majority reside in Japan. Like many of my generation, I was raised to be a recycler up to a point, but when I became aware of what they were doing at the J.A. Pan, Co. back in '66, it really 'lit a fire under me' on the subject.
Only 15%?! That's really low compared to my locale, though in the past decade it's gotten better. Until legislation makes it a huge finable offense that gets tacked on to property taxes if they fail to recycle, the average American isn't going to bother. Heck, around here if you want the city or county trash collectors to pick-up recyclables you have to pay via property tax assessment for the privilege even though they get paid by the reclaimers!
I really wonder why I bother though. I mean just one illegal alien or otherwise 'indifferent' family around me dumps more recyclable paper, cardboard, glass, plastic at the curb for trash pick-up in a week than I reclaim in a couple of months and there's many thousands of them in a ~5 mi. radius.
Looks nice, but I swoon at the thought of spending so much time on woodworking I can't see. Different strokes............
A Mickey D's with a Redwood fence?! Don't recall ever seeing such a luxury at any 'fast food' emporium around here. The only Redwood I've scored is [7] 1x8x96" rough sawn planks that's been collecting dust in the shop for right at 34 yrs now. Now that I know I'm probably stuck where I am till I'm good as gone, guess I ought to use it up on that fireplace I'd considered way back when now that firewood, as expensive as it is now, is cheaper than electrical or natural gas heat around here.
GM
You're absolutely right on all of this, GM, it seems like a drop in the bucket (the recycling efforts) when you look at what others pitch to be land filled and the leaders of our communities, for the most part, make some of it ridiculously difficult. I look at recycling as both a personal mandate due to my past activities and as an economical alternative. Who knows, maybe some of it wears off on others and that couldn't be a bad thing.
The detail in the cabinet construction also falls under the "personal mandate" thing, as well, I guess. If nothing else, it helps hone my woodworking skills.
The McDonalds fence was certainly a windfall, it's nearly impossible to find clear Redwood at any lumber yard around here. If it can be found, the price is very high. There was nothing wrong with the fence other than the paint was peeling from it and I'm guessing the bid from a painting contractor to repaint it determined the outcome. If you have some good plank, consider it an heirloom, lol.
Quote:
Originally Posted by
GM
Interesting, wasn't aware of a glue with such properties. Will come in handy for a couple of furniture repairs I need to do.
Thanks!
GM
Yes, my BIL swears by this adhesive and for the little time I've used it, it seems to have excellent adhesion and strength. An inadvertent placement of a clamping spacer and glue squeeze-out combined to make for quite a bit of tugging to release the clamping block. I would say it is quite similar to Titebond III but has more solids in the mix. When I filled my quart glue bottle from his gallon container, we had to mix the settled solids from the bottom of the gallon container.
I was out and about, this morning, looking for sheet fiberglass but couldn't come up with any. A learned employee at one of the lumber super-stores told me that Owens Corning will only distribute it through their distributor network and won't sell any to the generic super-stores. I picked up a roll of R-13 and thinking that it was what was in the original Model 19's and might be a good substitute. If it doesn't meet the requirements, I'll pull it out and put in something else in the future. I'm planning on placing the insulation behind the woofer on the back panel, 1/3 down from the top, across the top panel, and on the side panels, down the same 1/3. This is the current plan unless I hear different from you. I might peel a little fiberglass off so that the dimension is reduced from the 3 1/2" standard to about 2" or so. That is YTBD. Let me know what you think on this because I have no idea about densities and such.
Thanks, again, for your time and knowledge.
Edit: Thinking of how I could incorporate a bit of our shared recycling interest in this, I present: The hatch guide rails, made from the aforementioned McDonalds fence.
http://www.hostboard.com/forums/hbmc.../2011/04/6.jpg
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Re: GM's MLTL with 416-8B
Some more progress was made, last night. I stapled the R-13 fiberglass into the cabinet, installed foam srtips on the driver cradle, attached the front panel, and felted the bottom hatch cover.
There was a little problem with fitment between the front panel and the rest of the carcass. I had installed a T-nut in the channel for the center brace and a dry-fit showed some interference. The Dozuki made the necesary small cut in the center brace for clearance. Another dry-fit and this time the front panel passed the paper-won't-slide-under-starightedge test. It is sure a good feeling when the last panel falls in place with a resounding thump!:D
Earlier, I had promised pictues of a large number of clamps being used and here it is:
http://www.hostboard.com/forums/hbmc...2011/04/11.jpg
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http://www.hostboard.com/forums/hbmc...2011/04/14.jpg
http://www.hostboard.com/forums/hbmc...2011/04/15.jpg
I will attach the 416 in a little bit to make sure everything fits up well and then remove it for the finishing process. Before finishing, I'll launch into assembling the second cab.
GM, do you think the R-13 is going to make the grade or should I immediately remove it in favor of the 703 style? I'm pretty sure I can get that style of sheet fiberglass but not on the weekend. The R-13 wouldn't go to waste since I use it for other construction jobs.