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My new Open Baffle Project

edited July 2018 in DIY
Yeah yeah I know!  I haven't even finished the Clinchers yet, but...

Some off you heard my little hybrid OB project that I took to Dakota last Spring.  They sported a vented ND105-4 for bass and a TC9FD run open baffle which covered everything else.  I was so impressed with the imaging, sound stage, and overall openness that I wanted to scale up and do another hybrid using much better drivers.  This time, however, it will be a 3 way as I felt that project was missing needed top end air.  I want to use only drivers I already have on hand.  I did some modeling with ABC Dipole and have my mid driver nailed down.  It will be the Tang Band W4-1320SIF bamboo cone driver.  I still don't know for sure what I'll use for the bass bin woofers or the tweeters.  I need to build the mid/tweet open baffle boards< and take a bunch of measurements of the mid to get my brain around the whole thing and figure out exactly how low and how high I want cross the mid.  I would really like to use my Beston RT002A dipole tweeters but I'm not sure that is possible yet.  I may end up using a regular dome tweeter that can play lower (because needed).

I was going to make some prototype baffles with cheap particle board but that takes the same amount of work as making them out of something nice enough to keep.  I was able to run to Home Depot yesterday and found a nice straight piece of poplar that had some interesting grain patterns.  So this morning I machined the the midrange openings.  I left enough room above it for any 4.10" round flange tweeter (i.e. RS28A or XT25) or the 4" square Bestons.

Here's what I have so far:

 

D1PP1NS7910Turn2
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Comments

  • Thinking out loud:

    If you had a neo driver how would that affect the rearward radiation of the mid?  There was some discussion about the Statements regarding this.  Can you use soft material around the rear of the mid, or tweet, to shape the rearward response as can be done on the front of the baffle?      

    Something different for the bass aka. open baffle for the bass woofers like the Carver Amazings, or have the woofers facing towards each other into ... is that called an H frame?  you know, something other than the regular cone in a box thing. 

    YMMV      
  • I would think the rearward radiation would be better (more similar to the front radiation) with the neo version due to less magnet obstruction.

    I have played around with OB bass.  My room just isn't big enough for two 15" woofers per side.
  • You don't really need 15's, I used the peerless 830667 and they worked great as long as you respect the Xmas they have. Good clean H frame bass.
  • I'm good with OB bass to 80 Hz or so.  After that I want some thump associated with pressurizing the room

     John H, thanks to JP I did get that email
  • edited July 2018
    Hi John!  I was hoping you would jump in.  My current baffle width is 14 cm.  The W4-1320SIF has a Fs = 75 Hz, Qts = 0.36, Sd = 57 cm`2, and Xmax = 3 mm.  I believe any woofers I have on hand can easily play up to 500 Hz if not higher.  My "unknown" is what tweeters I have on hand that can reach down to the constant directivity of these mids on this baffle.
  • For those playing with ABC dipole this is what I get.  That Beston can almost make the dipole null with constant directivity.  This is going to be nice.

    Silver1omo
     John H, thanks to JP I did get that email
  • That is exactly what I got from ABC Dipole.  Here is what I got from the Edge:


    Silver1omo
  • I am in the process of making a few cheap and dirty test baffles to see the effects of removing the Beston's square face plate and rear mounting it with a "roundover" wave guide.
    jhollanderThumperTom


  • fyi I set up a pair of 12's (Beyma 12BR70) as an open back / shallow U 14 ⅜ width 6 inch sides and keep going into minidsp file to lower bass level.   A bit unexpected was the feel of the bass in the room.  This measurement is at ~3 feet so it is picking up the rear wave partial cancellation, and yet the bass drivers have a lot of leg room.  

    Silver1omo
  • Bare in mind that these are very rough test baffles.  The router work was pretty much just free hand.  I can use blue painter's tape to bridge the gaps.  What I really want to see are the major response differences.  I little blip here or there can be chalked up to my half arse router work.
  • First I routered a 0.500" slot that is 2.500" long.



    I also did another baffle with a slot that is 5/8" wide and 2.500" long (not pictured).
  • The baffle on the left has a 1/2" round over.  The one on the right has a 3/4" round over:



  • The back side of the baffles need to be counter sunk:





  • The bench mark baffle will be the Beston RT002A tweeter with the factory face plate installed, mounted from the front, flushed in:


  • Never mind my free hand crappy opening...  a little blue tape will easily bridge the gaps...


    Nicholas_23Silver1omo
  • Bad ass , I like watching your builds 
  • Looks good.  I think a 45 degree chamfer might reduce some of the on-axis dip. 
     John H, thanks to JP I did get that email
  • I hadn't thought of a 45 chamfer.  Guess I'll be making another test baffle.
  • Do you have a thumbnail/table-edge roundover bit? That could work as well.
  • Ho about no waveguide and sans faceplate? That's how I intend to use my pair.
  • Wolf said:
    Ho about no waveguide and sans faceplate? That's how I intend to use my pair.
    So flush/front mounted?
  • Yes flush mount and no faceplate.  That was on my list as well.  BTW, you can test the 1/2 inch round over then cut the 45 chamfer and test again.  My test baffles have bondo, filler, cardboard, foamcore, and tape all over until I finally pitch them.
    rjj45
     John H, thanks to JP I did get that email
  • I've got this panel raising bit that I'm hot to try for a shallow waveguide.  Mostly to get a cool wood grain effect.

    https://www.yonicotools.com/products/raised-panel-cabinet-door-router-bit-set-3-bit-ogee-yonico-12335


     John H, thanks to JP I did get that email
  • an add'l thought; many slot loaded tw's have fairly sharp and flat verticals to promote horizontal dispersion, so mabe a very shallow 45 degree for the vertical cuts, and use the round-out for the top and bottom horizontal section of the slot...
  • Yup- just like this:

    Of course the 2 holes may need to be patched or taped over in back.

  • Kinda fugly without a faceplate IMHO.  Do you plan to do anything about the 4 tits sticking out?
  • I'd probably do a flat plastic faceplate if the FR looked good
     John H, thanks to JP I did get that email
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