GeeDeeEmm's Altec Speaker Project

Discussion in 'Speakers' started by GeeDeeEmm, Aug 12, 2018.

  1. Money, money, money. I can say the word repeatedly, but I never have enough of it. That's why my Altec project took so long and involved all kinds of machinations to bring it all together. But I finally ended up with the A7 gear I needed: 416Z woofers (from Valencias, the cool ones with second-gen 16" cast frames and first-gen Alnicos); green 511B horns; green 802D drivers. The components are much prettier than the acres of mahogany that hide them from view. Oh, and a pair of Beyma CP21F slotted super tweeters for sweetness.

    The 6.5 cubic foot ported corner enclosures are a product of the usual online calculators and yield an F3 of 42Hz. Minimum panel thickness is 1.5" with some panels running 2.5" of back-breakingly heavy MDF. Each cab with components installed weighs just over 200 lbs. All visible panels are covered in striped mahogany veneer. They stand 49" tall, 39" wide, and 25" deep.

    Crossover is a two-way second-order Linkwitz/Riley at 800Hz. I used custom-wound 14 gauge inductors and motor run capacitors. An Altec-designed 30923 CD attenuation/eq network is incorporated into the horn leg. This circuit dramatically attenuates the mid frequencies between 1000-6000Hz and eliminates the infamous "shout" that is the bane of these driver/horn combinations. What remains is a beautiful, smooth response without any hint of edginess. The super tweeter horns are incorporated on a separate leg with a simple condenser at 10kHz - just as the 802Ds begin their own gently progressive 6-12dB/octave rolloff.

    Altec Cabs w Veneer and Oil 001.JPG Decals Installed 001.JPG Altec GRILLS 007.JPG Altec Complete 015.JPG
    The results of this build far exceeded my expectations and are by far the best speaks I've built so far. They are completely free of the "horniness" usually associated with horn systems, and the bass response is robust and perfect for the pop/rock/jazz music that I listen to. I haven't taken time to do any measurements on them yet, and I'm sure I'll be shocked by what I find. But for now the sound is all that matters, and these have rung my bell. The Altec engineers knew what they were doing.

    Next project? Don't know, yet. I have a couple more Altec 416s and some recently acquired Emilar EC175 drivers to play with. All I know at this point is that corner cabinets are the way to go when space is at a premium. Speakers this size don't exactly disappear into the room, but the space taken up in the corners would otherwise be taken up by some other type of clutter, and I'd rather these would be the clutter!

    Thanks for looking at this abbreviated summary of my one-year-long building project.

    Last edited: Aug 14, 2018
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  2. Thermionics

    Thermionics Post Whore In Training

    These are amazing!

    Do you have photos in your listening room with the super-tweeters in place?
  3. Celt

    Celt Peanut Head

    Most excellent! Would love to hear them!
  4. Thanks, guys.

    Amazingly, in the wealth of photos I took of this build, I never took a pic of the super tweets in place. They reside just above the woofer on the motor board behind the grill. I'll try to remember to take a picture of my "listening room" (nothing more than one end of my bedroom) and of the super tweeter in place.

    Thermionics likes this.
  5. Audionut

    Audionut Next Round Is On Me

    Great build and color scheme!
  6. Wntrmute2

    Wntrmute2 Junior Member

    Great work! I'm interested in your crossovers as I'm trying to get that circuit incorporated into my N800-F clones. Pics and/or schematic would be appreciated. Did I mention they look great!
  7. marantzfan

    marantzfan Administrator Staff Member

    Wow, those are really special. I love the attention to detail!

    Really like that you decided to display those green horns as usually those are hidden behind a grill.
  8. I chose to use a very basic, second order (12dB/octave) Linkwitz/Riley crossover. It's very easy to calculate at the DIY Crossover Designer Website:

    All you have to do is enter your speaker impedance and choose the network type, and the site will give you a complete schematic. My drivers are 16 ohm and the woofers are 8 ohm. Here's the network I used:

    [​IMG]Parts List
    C1 = 6.22 uF
    C2 = 12.44 uF
    L1 = 6.37 mH
    L2 = 3.18 mH

    Your components will vary if your speakers are of different impedance than mine, which they probably are.
    Here's a picture of mine:

    Altec Crossovers, Stage One 004.JPG

  9. Very nice looking speakers!

    Do you have a diagram of the 30923 eq network that you can post?
  10. Indeed. altec 30904.jpg
    The 30923 network is the upper portion of the schematic. Disregard the lower portion, which is a Zobel network intended for a different speaker. This is for the 8 ohm version. If you need the 16 ohm version, let me know. The 30923 circuit is wired after your crossover and before the L-pad on the tweeter leg.

  11. Thank you!
  12. Wntrmute2

    Wntrmute2 Junior Member

    Very straightforward. Could you show how you tied in the attenuation circuit?
    Actually I have a 16 ohm HF driver and 2 414-16s in parallel which gives me 8 ohms like yours.
  13. Altec Experiments 001.JPG

    Since your horn is 16 ohm also, you can simply use the same values I did, If you'd like. The 16 ohm version of the 30923 network is as follows:

    C1 - 3mf
    R1 - 7.8 ohms (7.5 is fine, too)
    R2 - 13 ohms (12.5 is fine)

    Of course, you can also use the crossover components that best suit you. For example, air coil inductors, film conductors, "better" capacitors, yadda, yadda.

    Happy to help as far as my limited knowledge goes.

    Wntrmute2 likes this.
  14. Wntrmute2

    Wntrmute2 Junior Member

    Helpful. Thanks!
  15. You're welcome. In case it's not exactly clear, all I did was take a direct feed from the high frequency output, thru the 30923 network, and to a separate horn output labeled "equalized." That way, I have the ability to go direct from the crossover, or thru the 30923 and to the horn.

  16. Wntrmute2

    Wntrmute2 Junior Member

    Gotcha. Great build. I love the exposed horn. I may try and do the same. 20180213_101557.jpg

    TubeHiFiNut likes this.
  17. Goodness, you have beautiful gear, neatly arranged, nice room. I like that.

    I can think of several schemes in which you could make a grill that would showcase those horns in that cabinet. They look great, already!

  18. SPL db

    SPL db Junior Member

    Wow! Those are outstanding! Would love to hear them one day. Where did you get the Altec label for the horn enclosure?
  19. Thanks, SPL. I'm humbled by your props.

    To me, it's the little touches that really give a build its finished look. The Altec badges and decals are available for about $20 on ebay. The badge, I think, came from Spain and took forever to arrive. The decals were from . . . somewhere??? Can't remember. There is also a gentleman in the USA on ebay that will make custom decals for very reasonable prices. I've used his decals on several items. All you have to do is send him a photo of what you want, what material you want it on, and what size you want it. He uses your information to print more decals and make them available for sale. Can't remember his name right off hand, but you'll see his decals for horns, drivers, electronics, etc on the 'bay. Search for "Altec Decals."

    SPL db likes this.
  20. SPL db likes this.

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