Open Baffle Epiphany!

Discussion in 'Speakers' started by cptnCanada, Jan 7, 2014.

  1. Porkloin

    Porkloin Oscar Heil Groupie Subscriber

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    Sort of an artist (mis)conception of what I have in mind: AMT Nuevo.

    AMT_FifthRow.gif
     

     

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  2. essNeff

    essNeff Active Member

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    This picture is much clearer. Thanks!
     
  3. Poultrygeist

    Poultrygeist Addicted Member

  4. Porkloin

    Porkloin Oscar Heil Groupie Subscriber

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    Interesting read. I had heard the words "push-pull" used regarding the pictured woofer assembly, and the article explains why.
    It also pointed out that I haven't invested enough thought time into the dimensions of the baffles and the timing of those waves traveling around from the back. I was just envisioning a couple of upside-down omnidirectional drivers, similar to the Ohm line, but it looks like I'm trying to plagiarize a Linkiwitz W-Frame incorrectly.
     
  5. Roscoe Primrose

    Roscoe Primrose New Member

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    Location:
    Virginia, USA
    Slot loading increases driver Qts, so you'll want to look for a driver with a Qts more like 0.6-0.75 for this application....

    Roscoe
     
  6. Poultrygeist

    Poultrygeist Addicted Member

    Interesting steam punk look of these near baffle-less speakers

    [​IMG]
     
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  7. perceval

    perceval New Member

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    3
    Hello all,

    I found this place while surfing the web. Pretty cool.

    So, I figured I'd show my OB setup as well. :)

    The are a construction of stone, aluminium and plywood layered to create a very un-resonant and rigid baffle.
    The stone is called Blue Barracuda quartzite, and it's only 6mm thick. So, no, they are not as heavy as you would think, they each weigh about 20-25 kg.

    And yes, they do sound as good as they look. :)

    [​IMG]
     
  8. mkane

    mkane AK Subscriber Subscriber

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    How did you cut the holes in the stone?
     
  9. darkblue94

    darkblue94 It wasn't me. Subscriber

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    It would be nice if we could see them in order to judge for ourselves just how good they look. :confused:
     

     

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  10. perceval

    perceval New Member

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    They were done by CNC water jet cutting.

    Oops... sorry. I used the hosting from another place, but I guess if you are not registered there, the picture won't show.
    Hopefully this will work this time:
    [​IMG]
     

    Attached Files:

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  11. Samokan

    Samokan AK Subscriber Subscriber

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    Very nice. Please let us know the process in creating it.
     
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  12. Poultrygeist

    Poultrygeist Addicted Member

    Speaking of resonance some folks go to great lengths in their OB construction to prevent it. In my experience it can be a problem at high volumes when the baffles become audibly excited.

    Fortunately I listen primarily to acoustic jazz at levels that rarely exceed 80 dbs so it's never been an issue.
     
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  13. darkblue94

    darkblue94 It wasn't me. Subscriber

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    Damn, they are good looking. :thumbsup:
     
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  14. perceval

    perceval New Member

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    3
    Thanks! I do like them a lot!

    With the layering of 3 different materials, there is no resonance, no "excitation" of the baffles. So, it's purely driver-driven music. :)

    Construction?
    Well, pretty simple.

    I found a slab of stone I liked. It's called Blue Barracuda quartzite.
    The slab is cut to dimensions, then cut down to 6mm thick on what looks like a huge table saw.

    IMG_20170610_083332.jpg

    Then, the thin stone rectangle is laminated to honeycombed aluminium. It provides support to the stone so it doesn't crack when doing holes later.
    The two layers are sent to the CNC water jet cutting, where we cut the holes.

    IMG_20170610_091932.jpg

    Back home, I laminated another layer of 15mm plywood and assembled the whole thing, adding a frame to make them stand.

    IMG_2739.JPG

    The drivers are the TB W8-1772, and a local 15" driver with the highest Qts I could find. It's actually a "full range" 15", hence the whizzer cone. I could've cut the whizzer away, but I thought they gave a balanced look with the 1772 whizzer. So, they are purely aesthetic.

    XO is active with a miniDSP HD. I keep the signal cleaner by using the USB input, staying digital. I was then able to try different XO curves, at different XO frequencies. After a lot of tryouts, A/B listening, the very best was a Harsch XO, which is a 4th order on the woofer, and a 2nd order on the full range, at 300Hz. I might try to go passive, but sourcing components will be harder and expensive! There is also some EQ applied, as the 1772 is far from a ruler flat driver, but when nudged here and there a little, it really starts to sing.

    All in all, quite the fun experience, and they do draw looks when people come into my house. Then, they want to have a listen.... and fall for that gorgeous OB sound.

    OB-BLUE FR.jpg
     
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  15. valvenator

    valvenator curious bystander, serious procrastinator Subscriber

    I would definitely have to agree. You could start your own speaker line with something like that!
     
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  16. mkane

    mkane AK Subscriber Subscriber

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    More Tang Bands. This time 1808's. Notch applied and there quite nice. DSC_0204.JPG
     
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  17. Samokan

    Samokan AK Subscriber Subscriber

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    Hi ‘mkane’ whose design are your speakers?
    I’m currently using the h-frame and would like to explore other designs. Thanks
     

     

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  18. sam3217

    sam3217 New Member

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    My first ever experimental attempt at 2 way OB sound after many iterations and playing with various full range drivers mostly 8' and 12". Since I started playing only the full range drivers, the attempts of adding a bass driver with an active crossover always mitigated the midrange magic so I had to think of a different way of playing the bass. It may sound silly or immature but it eventually came out really good. No compromise from 17K and well below 40Hz of room response. My idea was to drive the full range with no filter by tube and bass driver active amplified, solid state. The baffles are 30"X50", 18mm ply, mounted by 2'X2" solid wood chassis, held by steel brackets with hefty nuts and bolts. Full range driver is 100dB, 8 ohms and rolls off coz of baffle width below 100Hz and 97dB bass driver fed from a Miller & Kriesel sub amp crossed at 120 Hz and gets speaker level input from the Dynaco ST 35, which is driving the full range driver. The setup enables me to sometimes switch off the bass and just enjoy the FRD. Prior to my above experiment, I never knew that similar OB setups have been attempted with no filter driven FRDs in a 2 way. Nelson Pass slot loaded OB looks very interesting.

    [​IMG]
     
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  19. Poultrygeist

    Poultrygeist Addicted Member

    Nice! Sounds like we're following the same recipe. Welcome to AK.
     
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  20. sam3217

    sam3217 New Member

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    4
    Poultrygeist, I just noticed your profile picture and in there the OB FRD sitting atop of the WE bass bins ( I call them horn loaded OB or inverted box) That was my first iteration of 2 way OB with the rear of the bass driver open instead of sealed, to have true dipole bass. The bass was amazing with just one in a 2.1 mode but adding a second channel had serious room interaction problems.
     

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