Altec 2 Way Build ala JELabs - 802/32/414

Discussion in 'High Efficiency' started by marantzfan, Mar 8, 2018.

  1. marantzfan

    marantzfan Administrator Staff Member

    I've mentioned in a few places around the Haven that I'm starting to acquire parts to build the 2 way Altec project that the esteemed @je2a3 mentioned in his blog here:

    http://jelabs.blogspot.com/2014/01/altec-2-way-horn-system-redux.html

    And also in subsequent blog posts since then as well.

    So far I have got a pair of the 32c horns and a pair of 414z which are currently in Bill's capable hands at Great Plains Audio. The last pieces needed will be 802/808 drivers, cabinets and crossovers.

    I want to follow the recipe as closely to the letter as I can with one exception. I simply can't have exposed wiring and crossovers; they'll have to be mounted internally.

    So, 1st question, with the 614 cabinets, am I giving anything up if I mount the horns to the baffle, move the woofer down and change the port shape to accommodate. Perhaps either two smaller round or triangle shaped ports?
     
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  2. StevenZ

    StevenZ Active Member

    This should be interesting
     
  3. J-ROB

    J-ROB Senior Member

    Actually, I think it would be better to mount the horn in the cabinet, driver pointing down, for the simple reason that the major HF lobe of that horn is slightly above the center line of the mouth. You can hear it by moving up and down in front of a playing 32.

    The JE means of mounting shoots the highs toward the floor by 10 or 15 degrees. But JE just moved into a new house and may not have chairs yet, so it all works out. i did it too and it is not that bad but having the driver pointing down in a box will illuminate your head with highs better, perhaps.

    The problem is that the 414 probably won't fit between the driver on that bent horn and the cabinet wall, so there will need to be significant vertical separation of the 414 and 32. if the 414 is mounted too low in the cabinet, then you will not be in the beam of that driver at higher frequency.

    It's a balancing act. Stands might help solve the dilemma. Measure twice, cut once.
     
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  4. TubeHiFiNut

    TubeHiFiNut Administrator Staff Member

    Good luck with this build, my friend.

    Very exciting stuff. :)
     
  5. je2a3

    je2a3 Junior Member

    Heed Joe's advice above regarding mounting the 32 horns. That explains the mounting configuration found in the WE753, Altec 15, A8 and the floor monitors.

    Except this...?

    [​IMG]

    But I've seen these used as near-field monitors mounted above the console.

    Take note that my original crossover was voiced for the older aluminum voice coil 20275 diaphragm. Chances are you'll probably be using the later copper voice coil diaphragms from GPA, to my ears best to run the 414s full range like I did here. Or make it J-Rob style 1.5 uf PIO + L-pad, simplest!
     
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  6. TubeHiFiNut

    TubeHiFiNut Administrator Staff Member

    I'm grabbing one A8 (hopefully) this week. Interesting speaker.

    Hopefully I'll find another one soon! :)
     
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  7. One of the benefits of the 32/802 combination is that it can blend so well with a large paper cone woofer like the 414 or the Jensen P15LL, and to my ears the blending is best when the horn is mounted on the same front baffle as the woofer. I tried the 32 briefly suspended in free air above the woofer cabinet (as shown on JE's website) but it was not as coherent and seamless as when the horn was mounted on the front baffle. Perhaps this is due to the better support provided by the front baffle mounting or perhaps it's due to diffraction issues or something else. But for me it makes the most sense to mount the woofer and horn on the same front baffle. I mount the woofer on the rear of the baffle and the horn on the front surface. The bend of the horn faces down so it is pointed to the woofer magnet.

    In general you should keep the woofer and horn as close together as reasonably possible. I did this by making a hole for the horn first, attaching the horn in place with the 802 driver, and then experimenting with the woofer positioning to get them close, but not so close that you can't remove the 802 driver while the woofer is in place.
     
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  8. marantzfan

    marantzfan Administrator Staff Member

    That’s what I’m looking at doing as well. Do you happen to have any picture of the baffle (front and back) to see how you oriented everything?
     
  9. ICTWoody

    ICTWoody Junior Member

    This thread is really helpful as I move forward on my projects. Thanks guys.

    - Woody
     
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  10. ICTWoody

    ICTWoody Junior Member

    Could someone built an adjustable sled for the horn when mounted outside the box to adjust its angle? Basically, when it was mounted as JE has, then couldn't you just "lay it back" more to bring that lobe up?

    - Woody
     
  11. J-ROB

    J-ROB Senior Member

    Yeah, and that is what I did.

    Well not exactly an "adjustable sled"...it was a bit more ghetto than that, as one could imagine. At one time, I used two Riga
    Sprat cans to get the desired launch angle.

    rigasprat.jpg
     
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  13. TubeHiFiNut

    TubeHiFiNut Administrator Staff Member

  14. J-ROB

    J-ROB Senior Member

    Wrote this up a bit at AK, but I have a pr of 4 cu.ft. 753 inspired cabinets set up for WE 728B and an optional removable "horn board" to stick in a 32 horn if I feel like it.

    IMG_2361.JPG



    728stuffing.jpg

    Right now I'm auditioning an Altec 3000 tweeter cut in at 8kc, which is working real well.

    IMG_2393[1].JPG

    728B is a full range 12", unlike the 15" Jensen in the original 753C. Goes higher than a 414 too. Outstanding driver.

    This cab needs a bit more damping. Very slightly boomy and there is a notch at 400hz which suspiciously has a half wave length of the depth of the cabinet, signalling a reflective cancellation issue. I might hang a thick piece of felt down the center.

    The best 753 version is the early 753A, which is a three way with a 752A horn tweeter, like a PM 597A. Rare stuff.

    i would rate 753C as an OK (score 6/10) WE speaker. It's nice. Not the most mind blowing of the late 40s WE line though.

    The killer WE speaker of that era is the WE 757A rating 9.6/10 for the gold. 728B with aluminum 713 driver and WE bent horn, slant cab like a 618. Mounted on the wall, the driver points upward so as to put the listener in the HF hotspot. One of the best ever. Salectric heard these at Rocky when I demoed them at that show.

     
  15. Yes, I did hear the pair of 757a speakers that Joe had at the 2011 RMAF. Easily the best sound at the show. Joe, I will have to take your word for where the 753 ranks in the WE pecking order. I have never heard true 753s, only modern builds using new cabinets at Deja Vu Audio. However, Vu had a real nice OB speaker at the store last year that has a 15” Jensen, WE 713b in a WE 32, and an Electro-Voice tweeter crossing in at 10K, that was mind-blowing as far as I was concerned. In fact, hearing that speaker is what led me to buy my present speakers from Vu—-15” Jensen in OB, YL Acoustic midrange horn crossing in at 700 and supplemented on top by EV T350 tweeters crossing in at 10K. I love the sound! They don’t aim as high as the 713 speaker but they do share some of the same DNA.
     
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  16. Redboy

    Redboy Knobophobe

    Sutherland Felt, Joe @J-ROB...

    http://sutherlandfelt.com

    Ronan turned me on to this outfit. If you need felt, they've got felt.

    Kinda like Spatula City, but different.

     
    Last edited: Mar 9, 2018
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  17. Redboy

    Redboy Knobophobe

    We're gonna need pictures to go with this post, you know?
     
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  18. Sure, I will post a photo tomorrow.
     
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  19. Audionut

    Audionut Next Round Is On Me

    Honest greenhorn question (please remove the tomatoes from the cans if you decide to throw them); how does a bent horn affect imaging when the sound waves bounce out of a 90? Should not a straight horn be superior/ideal?
     
  20. IMG_5912.JPG IMG_5913.JPG
    Here are two photos of my open baffle speakers that use a 15" Jensen woofer, YL Acoustic midrange horn, EV tweeter. The photos were taken at the Deja Vu Audio store before the speakers were delivered to me.
    The speakers lurking behind mine are the Jensen/Western Electric 713 speakers I mentioned in a post yesterday. The front baffle of the WE speakers is 32w x 59h. Mine are a svelte 29w x 47h.
     
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