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Build Thread: SR71-inspired Center Channel

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  • arlis_1957@yahoo.com
    replied
    Re: Build Thread: SR71-inspired Center Channel

    if your avr is crossed low, i think youll notice a big difference. nice build. nice of john to help out.

    Leave a comment:


  • djg
    replied
    Re: Build Thread: SR71-inspired Center Channel

    The grille should cancel any psycho-acoustic effects from looking at the asymmetrical layout. And keep fingers out too.

    Leave a comment:


  • lunchmoney
    started a topic Build Thread: SR71-inspired Center Channel

    Build Thread: SR71-inspired Center Channel

    So I'm building a center channel to compliment my SR71 mains (see zaphaudio.com for info on the SR71's), as the Tritrix MTM center I'm currently using with them just ain't cutting it. Nice though it is, it's not on par with the SR71's, and I'm looking forward to a center channel that matches the SR71's better.

    Since an SR71 Center Channel design does not exist, Zaph (John Krutke) has very kindly helped me to design a center channel that should match the SR71 mains well.

    This will use the same drivers as an SR71, and a similar crossover design...

    However, I will stop short of calling it an "SR71 Center Channel", because although Zaph did help in designing the crossover, and gave me some invaluable advice for designing it, this speaker will not have the benefit of actually having been listened to and tweaked by Zaph... in addition, the crossover he designed is an approximation, certain component values will be tweaked once the speaker is in place, by me... in other words, this speaker will not have earned the right to be called an "SR71", a high accolade to be sure.

    Edit: We have a name: The Blackbird Center Channel... inspired by the SR71 Blackbird jet

    SEAS ER18RNX Woofer




    SEAS 27TDFC Tweeter




    Here are some images of the design. All 3/4" mdf. Note that the flange of the tweeter will be trimmed in order to get the tweeter as close as possible to the woofer. 2" Precision Port facing out the back. Outer dimensions are 21.75" wide X 8.125" high X 10.75" deep. Internal volume is .5 cubic feet, not including the sealed off chamber for the crossover (to the left of the tweeter). There will eventually be a grill over it for baby-proofing reasons, by sheer coincidence the PE 1 cu ft MTM grill is a perfect fit. The small panel on the back will be for accessing the crossover. In general, aesthetics are of no concern, as it will be buried in an AV cabinet, all that will be seen is the PE grill. Usual over-the-top bracing scheme that I like to use. I'm a firm believer in a lot of bracing, after hearing how nice my SR71 cabinets sound, which used a similar bracing scheme.




    One of the challenges with this design is that the speaker will sit inside of an AV Cabinet, with a 46" TV directly above it... so it's almost as though it's flush wall-mounted, with an infinite baffle. Here's a pic that shows the AV cabinet, the upper shelf in the middle is where the speaker will sit. The TV will sit directly above it.




    Zaph very kindly did an approximate simulation for me, with a crossover design that is similar to an SR71 but with much lower BSC... I must emphasize approximate, since how the cabinet and TV will ultimately effect how the speaker sounds is difficult to predict. I will be trying different values for the woofer inductor and tweeter resistor to dial in the right amount of BSC. There will definitely be a lot of trial and error going on here. Mike Z will be prodded with coffee, beer, and doughnuts to assist.

    As you can see, Zaph's approximated simulation shows quite symmetrical horizontal lobing, despite the assymetrical driver layout. Not perfect, but very close. This is quite consistent with the nearly perfectly symmetrical vertical lobing that SR71's exhibit, which is what made the SR71 a good candidate for a matching horizontal center channel.

    This design obviously challenges the notion that center channels need to be symmetrical. At least that is the hope, we shall see.



    Parts have been ordered and sawdust will soon fly. More pix as the build commences.

    Thanks for any comments!

    EDIT: Here is the final crossover schematic



    EDIT: Here is a dimensioned drawing of the final design

    Last edited by lunchmoney; 02-01-2011, 05:44 PM.
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