Altec MLTL with Model 19 drivers

Discussion in 'DIY' started by westend, Mar 22, 2011.

  1. westend

    westend Audiopile Subscriber

    This thread will document a large MLTL enclosure using the Altec 416-8b. The design of the cabinet was done by GM, an Altec user and installer with many years of experience in audio and a damn fine individual. The initial design considerations were discussed here on Todd White's Altec User Board. To summarize the goals: Raise the height of the woofer to accommodate my listening space and to improve upon the low position of the original Altec Model 19 alignment.

    I will be using the Altec 811 horn and a Heil AMT1 tweeter on the top of the enclosure. The cabinet dimensions are 52 3/4" H x 30" W x 21" D, volume is 16 1/2 ft.^3.

    Preliminary sketch using Google sketchup (without true scale, I'm not that good with the program, yet):


    Note: At one time I bought six sheets of Birch plywood from my local lumber superstore. These turned out to be full of voids and the interior plies were probably not the same species. They were returned and 13 ply, 19mm Baltic Birch in 5' x5' sheets were purchased from my local hardwoods supplier.

    I am about to start cutting and am sorting sheets. I'm going in.....:D

    Attached Files:

  2. Russellc

    Russellc AK Subscriber Subscriber

    Ah, finally the Altec project cometh!:thmbsp:

  3. shawnra

    shawnra New Member

    good on ya for getting the real deal, the Baltic Birch. It pretty amazing stuff most of it comes from Russia. In Canada all most all of it is imported through Thomes Canada and they have a great detailed explanation of how this stuff is made on their website. Pretty interesting read. They also specialize in importing Aircraft plywood and I've often wondered about using it for a set of enclosures. Too expensive though. Here's a link to the importer

    Those sheets are pretty heavy so don't strain yourself Eh!
  4. ejfud

    ejfud Audio Pinhead

    Nice Lance. I'm excited for you to get this going.

    Please don't bring back those ugly old fake Model 19 cabinets you took from me a while ago or I'll have to sick my wife on you.

    Any thoughts on mounting the horn to a baffle to help dampen them?
  5. doucanoe

    doucanoe Registered Audio Abuser

    Looks like your off to a good start Lance!

  6. djnagle

    djnagle Member

    Looking forward to seeing this develop Lance. What are you using for the 811 driver? What crossover?
  7. westend

    westend Audiopile Subscriber

    Those cabinets went to another local AK'er that has more time and patience then myself. Please, don't let the wife at me!:D

    Initial plans are an adjustable sled w/ mounting baffle. I found that I was not hearing any of the infamous ringing when the front flange of the horn is securely bolted to wood.

    Thanks Ron, at least it's a start.

    I have been using 802-8g's with the original light aluminum 'phragms. I am already thinking about different hornage. I've been using active crossovers and don't know why I would change that, they just work so well.

    F*&k, I need a sheet crane, you're right they're heavy. The only way to deal with that is to start cutting!:D
    These sheets would probably be a grade "B" according to the grading scale from Thomes. I do have access to some marine grade plywood but 1/2" dimension sheets 4' x 6', IIRC, are $110. They are made with phenoiic resin and are glassed on one surface. Heavy, straight, and expensive.
  8. diamondsouled

    diamondsouled Plug me into something Subscriber

    Great project!!! I love the great Heils. How are the diaphragms in yours? I have 5 pairs and when I hooked up a 4 a side array I found out that they were not all outputting the same SPL. What frequency are you crossing the Heils over at? I guess if it's high enough you wouldn't have to worry about any notching.

    This makes me wonder if I should sub a Heil into my Valencias some time to hear what they sound like in there. I'm using 2404 Cheeks right now. :yes:

    BTW what type of corner joint are you planning on using?


    Last edited: Mar 22, 2011
  9. westend

    westend Audiopile Subscriber

    Hey, Lar. The Heil pair I have seem very well matched, I've never measured them (don't have the gear yet) but they always seemed balanced. I plan to cross them at about 9Khz or so.

    I had pondered what kind of joinery I was going to use on these and expedience and practicality won the day. They will be butt-jointed with a ledger (gusset) in each corner. I have a lot of faith in Titebond III, I guess. Everything I've built using that adhesive is still together, including my sliding tool boxes in the truck which get a lot of abuse. I plan to embellish the exterior of the cabs when I have them all together. I have ideas, oh yeah.:scratch2:
  10. westend

    westend Audiopile Subscriber

    cutting tutorial

    Thought I would show this since I read about some guys having difficulty with cutting panels and they shy away from speaker builds or use Home Depot's panel cutter and the results aren't always good.

    Firstly, I have a good table saw, fence, and out feed tables, more than enough gear to cut these 5' x5" panels. I choose to cut them, however, using my trusty Makita 7 1/4" circular saw and a straight edge. Some folks will tell you that you can't get a good quality of cut with a circular saw and the pictures, here, should dispel that. I will be using the table saw when I have the panels cut to some smaller dimensions for good repeatability.

    As said, Makita 7 1/4" 5007NB (been dropped and thrown around for many years and keeps ticking), Freud Diablo 7 1/4" 48 tooth finishing blade with a very small kerf (1/16" or so), E Emerson 8' clamping straightedge, metal rule.

    After assessing the squareness of the panel, I mark my cut line, measure the distance of the saw blade tooth to the edge of the saw table (in this case it is close to 5 1/16" in.). The clamping straightedge is positioned back from the cut line the aforementioned dimension (5 1/16"). Adjust the saw until the blade will cut 1/16" deeper than the sheet. I use a piece of MDF under the sheet I'm cutting and it is a sacrificial table that is steady and doesn't impede the blade. Position the saw at the straightedge and push it down the sheet with the edge of the circular saw table against the straightedge. At about mid cut, I look to see if the cut is trying to close and, if so, throw a little wedge in there to keep the cut open. Take a look at the pictures and you'll see the results.

    This is an easy way to get accurate cuts in sheet goods and saves some laborious lifting and setup with the table saw.

    Attached Files:

  11. ejfud

    ejfud Audio Pinhead

    Only way to break down a sheet of plywood in my eyes. A circular saw and a good straight edge. Beatuiful cut line. That Frued blade is great. I've used this technique for many years. The only thing that's changed is I was given an amazing Festool circular saw/guide rail setup that makes quick work of this job.

    Keep the educational stuff coming Lance. I always learn from your techniques.
  12. jaymanaa

    jaymanaa AK Subscriber Subscriber

    Hey Gary, try a red diablo thin kerf wet lumber blade. They are like a lazer beam. I bought one for my skillsaw and now have them on the table and mitre saws.:yes: Frueds are good too though.:yes:

    OOPS, just noticed the Diablo in the post above. Didn't know they were made by Frued.
    Last edited: Mar 22, 2011
  13. ejfud

    ejfud Audio Pinhead

    I need a new blade for my table saw. I'll be heading to the home store this weekend. Thanks for the tip Jay.
  14. specialidiot

    specialidiot Break Glass, Smoke Lucky Subscriber

    Great project Lance, I'll be watching!

    Would you mind pointing me to your BB source? I have a little project in the works......
  15. Doc Zinger

    Doc Zinger New Member

    Looks like another great project, if I keep reading these DIY threads I might get the urge to shitcan my speakers and amps just to have the fun of building something else again.

    Saw something about horn damping, if your horns aren't exposed you might consider using Plasti Clay. I used on my 24" alum horns and on my Electro Voice tweeters and they are dead when you tap them, don't look so hot though.

    I also thought about using a rubber strip product that's used for waterproofing around windows/doors after install before siding. Home Depot has it, about 6" wide made by Grace, sticky on one side( sticks like hell after putting down) thought it might be good to line interior cabinet surfaces(about 1/8" thick) and cut down panel resonances seems like it would cost alot less than some of the producs sold for that purpose.

    Hope the panel wrestling match cut down went ok, once you get to the table saw the real fun begins.
  16. westend

    westend Audiopile Subscriber

    Festool...? :ntwrthy: Heck if there is anyone I know that can put a toool like that to use, it's you, Gary. I am actually thinking of making a "Poor man's guide system" out of a straightedge and an attachment on another circular saw. I need to run one of those German saws to see how slick it is.

    Yup, that's exactly what I have clamped in the saw, Jay. It cuts like buttah' and I just ripped a sheet of 60" nominal sheet and both pieces are over 30". That just saved me $70 because I need two 30" pieces.:yes:

    Gary, I haven't used it yet but all reports are this is a good one for ripping, the Freud Glue Line Rip, LM74R010 (attached). For all the different one's Ive bought, it's hard to beat the Forrest WoodworkerII.

    Not a problem, Youngblood's Lumber, 1335 Central Ave. Mpls., 612-789-3521. Tell them you have a business.
    It's worth a trip over there to just see what an old-time lumber yard looks like, there aren't many left. Don't get too attracted to the exotic hardwoods rack, it'll break 'ya. :D
    FWIW, the lumber salesman dropped by the other day and told me that they now have veneered furniture grade fir plywood that is void-free.

    Attached Files:

  17. audiozaz

    audiozaz rtfm!? - tl;dr

    Good tips on cutting, thanks! I can certainly put that to use with my 8¼" Makita!

    Looking forward to see this project develop as well, good luck!

  18. westend

    westend Audiopile Subscriber

    8 1/4", eh! That is good to see since those blades were uncommon and it has been problematic to find good ones to fit my Delta Sawbuck. Hopefully, they will be offered in the lumber superstores.
    Besides worm drive saws, the Makita, Bosch, and Porter-Cable are what I see used on job sites. They can take a beating and still cut straight.

    Marked the cutout for the woofer, this morning. The center ended up to be 44" from the bottom, a really good height for my listening space. But Damn, these are big cabinets!

    Attached Files:

  19. shawnra

    shawnra New Member

    good tips on ripping plywood and to think I've been using a piece of baseboard and some screws. Oh well! I too have been looking for a good blade for my skill saw and the one your using looks like a keeper, I'll give it a try. 44" is where I like the center of the high frequency driver to sit also, it seems to jive with most chairs and seating positions. at 16.5 cubic feet I would not call those cabinets big, I would call the enormous.
  20. westend

    westend Audiopile Subscriber

    Yeah, the clamping straightedges take a lot of alignment and misc. clamping out of the process. How many times I had the bottom of the saw motor hit a clamp, I can't tell you. I think Rockler had a set on sale, not too long ago. I have one of their 50" clamps. I also have a Woodcraft 99" made by E Emerson, it is a better product. They also offer a plate to screw onto your saw that has an extrusion that fits into the straightedge track. No wobble or deviance, probably. I plan to make my own, sort of like this.

    Yeah, big, real big! I am discussing bracing arrangements, ATM, with someone that has built more than a few of these and bracing will chew up a lot of time. I figure the worst I can do with these is get about the same sound as I had with Model 19 clones but in a better package. With the lower MLTL tuning I may get down into the 20's, we will see.

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