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Thread: Altec Custom VOTT Somethings

  1. #61
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    it appears the cut-out for the horn is wider than the horn thus leaving a couple narrow openings each side of the horn. Is this then considered the way they vented the speaker within the design?


    All of Altecs enclosures that followed this muddled model are really from the time when pre-TS parameters were codified ( early-mid 1970s ).

    The "large horn cut-out approach is not the way to deal with the realities of tuning a Bass Reflex enclosure.

    Again, it's an obsolete approach.


  2. #62
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    Quote Originally Posted by Earl K View Post


    All of Altecs enclosures that followed this muddled model are really from the time when pre-TS parameters were codified ( early-mid 1970s ).

    The "large horn cut-out approach is not the way to deal with the realities of tuning a Bass Reflex enclosure.

    Again, it's an obsolete approach.

    So seal that off in favor of adding a actual port/vent?

  3. #63
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    Quote Originally Posted by Drugolf View Post
    So seal that off in favor of adding a actual port/vent?
    I am watching for Earl's reply with much anticipation. I have wondered about this. I would like to seal those gaps and add a back or bottom facing port. I am not sure how much collector value I would be ruining by cutting a hole in the back, so I could make a new back piece entirely. For a bottom port option, my Malibu cabinets have a trim piece on the front and sides that elevate the actual cabinet bottom off of the ground. It would have to be calculated to see if that's enough air volume to do the job. That would be a permanent change though!

  4. #64
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    Quote Originally Posted by Drugolf View Post
    So seal that off in favor of adding a actual port/vent?
    Yes, seal it off and add a calculated ( & verified by an impedance sweep ) port .

    Any other ( unexpected or un-accounted ) holes in the enclosure raises the box tuning ( Fb ) .


  5. #65
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    Quote Originally Posted by Earl K View Post
    Yes, seal it off and add a calculated ( & verified by an impedance sweep ) port .

    Any other ( unexpected or un-accounted ) holes in the enclosure raises the box tuning ( Fb ) .

    Okay what I think I am going to do is do some testing using the original box, but with a baffle I will build that is more in keeping with the Malibu design. I will zero in on ports for it now that I am starting to understand how to determine all of that, at least on paper. The cabinet is a little larger than the original Malibu so I will have to play around with that too, which may be a good way to determine if more internal volume is a good thing.

    Richard in my parameters WINISD thread suggested I could drop the tuning down since the 411A FS is pretty low at 18.31. I will poost a drawing of the baffle once I get it drawn up. One with the 811 horn, the other with my new Emilar horn.

  6. #66
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    Okay, here are some baffle configuration options for using the existing cabinet for now. Baffle is 34.5H x 23.75" W. The first two identify the cutout for the 811 horn within the baffle. I would probably set that back so the front of the horn is at the front of the baffle. the 3rd option shows a Emilar bowtie horn mounting on top and using the entire cabinet for just the 414A's. 8.0 CF of volume.

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  7. #67
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    Quote Originally Posted by Drugolf View Post
    Okay, here are some baffle configuration options for using the existing cabinet for now. Baffle is 34.5H x 23.75" W. The first two identify the cutout for teh 811 horn within teh baffle. I would probably set that back so the front of the horn as at the front of the baffle. the 3rd option shows a Emilar bowtie horn mounting on top and using the entire cabinet for just the 414A's. 8.0 CF of volume.

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    I'd go with the third pic ( horn on top ).


  8. #68
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    Quote Originally Posted by Earl K View Post
    I'd go with the third pic ( horn on top ).

    Agree on that. The look goes back to the original LMCo. Iconic 2-way 800 cycle woofer to a horn monitor, and hasn't been improved on since. Some performance gain, though, may be obtained by baffling the horn.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  9. #69
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    Quote Originally Posted by speakerdave View Post
    Agree on that. The look goes back to the original LMCo. Iconic 2-way 800 cycle woofer to a horn monitor, and hasn't been improved on since. Some performance gain, though, may be obtained by baffling the horn.
    When you say baffle the horns, are you thinking a front only open baffle type structure? Does that add additional stability for resonance purposes, or just a little more wingspan?
    I've worked on it already a little. A bit more challenging cut-out of course and for it to look good I think it would be best as a front mount so the cut doesn't have to be perfect and is hidden behind the lip. I could dial in the cut-out and do it with a CNC to get a great cut if that makes a big difference.

  10. #70
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    Quote Originally Posted by Drugolf View Post
    When you say baffle the horns, are you thinking a front only open baffle type structure? Does that add additional stability for resonance purposes, or just a little more wingspan?
    I've worked on it already a little. A bit more challenging cut-out of course and for it to look good I think it would be best as a front mount so the cut doesn't have to be perfect and is hidden behind the lip. I could dial in the cut-out and do it with a CNC to get a great cut if that makes a big difference.
    Not a horn expert, but, yes, I think the way the horn is terminated can affect the presence or not of resonances. Also loading and pattern control in the cutoff region. And being bolted to a wood baffle will help damp vibrations in the horn body. The LMCo. horn was tar-filled I believe.

    A flat "false front" baffle would do almost as much as having the horn in the box.

    I like the horn on top for a couple of reasons. One, I guess is the industrial chic aspect of it-- having the works showing. Mounting the horn to the baffle and securing a heavy CD (more of a problem with large format) inside the cabinet is a lot more work. Also, I don't think having the horn projecting through the baffle/grille plane looks that great, except when done as well as the Eames's did it. I also like smooth looking fully enclosed speaker systems, and so do spouses. With the Emilar EH800 that is easily achieved, except of course, for the tricky cut for the horn. Putting it in the cabinet would give you the advantages mentioned above with regard to baffling.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Got some things done here. Fabricated a new baffle to use with the original cabinets from old Khorn front panels that I recently removed to build new ones for. 3/4" plywood. Went with the straight evenly spaced vertical alignment for the 414A cut-outs with the 2 ports flanking in the middle. Rear mount and using inset nuts so I can remove the woofers easily enough later as needed.

    The horns will be mounted on top so in the end the cabinet volume is 9.1 cf before subtracting anything for the drivers etc, so I am using a little less for my modeling in WinISD. I am ready to put this all together so here are some graphs for 35hz tuning and 40hz tuning with the 4" round ports. What looks better? Any thoughts on what I might want to adjust? The port length on the 35Hz is 3.6". On the 40hz it is 2".

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    Also, here are two of the 414A woofers with the new surrounds and gaskets. The goop is white before application but becomes clear in a few hours.
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  12. #72
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    Ultimately the tuning you go with has to interact nicely with your room acoustics & ever-present room modes > therefore its impossible to predict which of those 2 curves will be best for your particular circumstances.

    That said, I like flexibility with box tunings > therefore I would want to know what happens ( or what the predictions say ) if I were to block one of two ports ( stuffing the ducting with foam for instance ).



    BTW, you're the first poster that I'm aware of ( almost anywhere ) that has replaced his own linen-based surrounds on a woofer ( so I'm really impressed ).

    Nicely done!


  13. #73
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    Yeah, I am thinking I start wit the longer ports and go from there. Can try stuffing one, then making them shorter and so on. The 4" ABS is the least of my worries. Got a lot of variables to play with including bracing and insulation yet too. The cabinets are basically 1.5" thick with a 3/4" pressboard box inside a 3/4" ply box. Front to back bracing I think is the best addition at this point for sure.

    I was surprised not to find anything out there on installing new surrounds on these so I am gad I found what appears to be a good product to give it a go with. Otherwise the option to do a complete re-cone has is negatives including cost so I am hoping for good results doing this. Won't know until I run them through the paces and maybe do some measurements. They look fine though. If they fly off after the first few big bass notes, I guess we'll know.

    I am heading out of town on Spring Break for the rest of the week so it may be a couple before I get back on this. Meanwhile i picked up a pair of 416-8A woofers to put into the mix somewhere with a build.

  14. #74
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    EDIT: Finding it very difficult to source this material. See new thread.

    Zeroing in on my insulation choice. Looks like the Owens Corning unfaced 703 product is ideal. It has a PCF of 3.0
    Here is a graph showing the sound insulation results at various thicknesses. Should I stick with the 1"?

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  15. #75
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    The 1" non-shedding unbacked fiberglass I've used is sold under the Wrap-on label. They used to deal direct, but I believe now they prefer to go through B.E. Atlas, a jobber in Chicago. Atlas will take a credit card order over the phone. 800 305-4393.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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