The BaSSlines (Lamda TD12H, B&C6md38, Peerless HDS)


  • Member
    dlneubec on #301

    John asked me to post a thread on this design here some time ago and I finally got started on the construction. I heard this open baffle design (pictured below) by Jeff Bagby/Jim Salk at the inDIYana event in April. I thought they were perhaps the best speaker I’ve heard, stunningly clean, smooth, balanced and unrestrained with a great soundstage. They were very much “live” sounding. I was so impressed with them that I’ve been inspired to try and recreate my own version of it. I’m hoping for sensitivity in the 92-93db range. I believe Jeff said his design was about 93db.

    Here is what Jeff is using in the Salk design, according to what he told us InDIYana:
    12” Lambda TD12H ($259ea.), crossed at around 450hz.
    6.5” PHL 6.5″ mid (1120 is the available equivalent) midrange ($159ea.), crossed at 2.7khz
    Morel MDT33 tweeter ($149ea.)
    http://aespeakers.com/drivers.php?driver_id=6
    http://estore.websitepros.com/1736754/Detail.bok?no=48
    http://www.madisound.com/catalog/product_info.php?manufacturers_id=141&products_id=570

    For those who have not seen it, here is the Bagby/Salk design.

    Goals:
    My goal was to create a little smaller speaker (higher SAF, you know;)). My concept is about 16” wide at the base, tapering to 7” wide at the top and is about 42”-43″ tall. I’m thinking of doing the woofer bafflesout of laminated solid hardwood, 1.5″ thick. The idea is to laminate them from 1″x2″ hardwood stock laid flat and stacked vertically. I will mix a second hardwood as shown strictly for aesthetics. The open baffle section will be a mix of 1/2″ Lexan with a contunaction of the same laminated hardwood as a bacer for mounting the drivers.

    I’m also considering mounting the woofer, midrange and possibly the tweeter from the rear, leaving 1/2″ wood between the driver and the baffle face. I would use a 1/2″ round-over on the edge. The tweeter,in effect, would have a shallow, 1/2″ deep waveguide. This serves to boost the low end output by about 3db over a broad range centered around about 3kHz. When equalized out in the crossover, it will allow the tweeter more headroom and lower distortion at the low end and also help in countering the rising response of the Peerless HDS at the upper end. Mounting the woofer from behind lessens the visual impact it has on the design. Of course, I will be doing some measurements to see just what effect this will have on the drivers natural frequency response before making a decision to use this kind of mount with any of the drivers. Below is a mock-up of what it is planned to look like.

    Drivers:
    The drivers of the Salk/Bagby design run in excess of $1100/pair. I would like to reduce that where possible, while losing little in either sensitivity or sound quality. Here are the drivers I’ve come up with to use, with an all passive crossovers at about 450 and 2500hz.

    Woofer:
    Lambda TD12H 12”, 93db: $468/pair (link above)

    Midrange:
    B&C 6MD38, 96db: $92 ea.
    http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=294-651

    Tweeter:
    Peerless HDS 810921, 93db: $78
    http://www.madisound.com/catalog/product_info.php?manufacturers_id=143&products_id=1744
    I pcked up two of these for $55 before the price went up.

    The B&C 6MD38 seems to be well thought of, has very similar specs and published FR. Zaph has recently tested it and “it looks like a drop in replacement for the PHL” (Jeff’s words, not Zaph’s). The total driver cost will have been reduced to about $762/pair, and though still very expensive, is about a $340 savings.

    The TD12H is in a 55L box. I’m using a slot port, exiting at the bottom rear of the box. Tuning will be such that the F3 will be about 35hz. It will put out over 110db at 100watts and not be even close to Xmax. I’m trying a new box deisgn that uses red oak ribs dadoed into the walls combined with simple cross braces for panel resonance control. According to my calculations, it will use about 17% less space than an equivalent window-brace type design.

    I’ve done some diffraction modelling in BDS. Here are the results for the two drivers:

    In addition, I’ve done some diffraction simulation and dipole simulations in John k.’s ABCDipole and in the Edge. Attached are the diffraction and then dipole simulations from ABCDipole:


    Below is a graph from the Edge model showing dipole and diffraction results.

    Here are some results on woofer/midrange floor bounce nulls.

    Construction of a prototype is ongoing and I will post some photo’s next.


    Member
    dlneubec on #3561

    Here are some construction photos:




    Member
    dlneubec on #3562

    Here are more photos. The slot port will be removable until a final version of the designis complete so adjustments can be made. Also, I will be able to pull it out and finish it separately, or possibly make it out of hardwood.




    Member
    dlneubec on #3563

    And three more.




    Member
    dlneubec on #3564

    This brings us up to date as of last weekend. FYI, the baffles are test baffles. The finished ones will be laminated hardwood and Lexan as planned. The box has been glued up (except the top). The woofer baffle will be removable. Here you can see the cross bracing implemented, including a “filler brace”. This brace will be glued to front of the cross brace and have speaker gasket material on its face. It will physically connect to the back of the woofer. This will essentially connect the woofer to all four sides, to distribute vibrations and reduce motor movement. Nxt up are to add a small dowel, top to bottom, through the slot port (to control panel resonance in the top slot port wall), add front face cross braces that will be used for mounting threaded inserts for the baffle removal and pack the space between the ribs with insulation.

    When the top and baffle are clamped on, the box does indeed sound quite dead, from a knuckle rap perspective. I have no other way to test it. Of course it will be even better when the top is glued on, the filler brace fully implemented and the final version of the port glued in.

    You can see the woofer mounted from the back, 1/2″ inset, with 1/2″ roundover. I plan to cut a steeper chamfer on the top of the woofer baffle, probably 30º or less. That’s all for now!




    Member
    dlneubec on #3565

    These speakers are almost complete. I hope to have the finish wrapped up in the next week or two and then will make final crossover tweaks, if any, and publish the completed design. I used a small spare room we have upstairs to do the finishing in, since it is easier than doing out in the garage this time of year. I etched the logo on the Lexan with by hand with a dremel using vinyl stencils (that John here at AE speakers did for me, thanks John!) as a guideline.

    There is a more complete build thread here:The BaSSlines

    Thanks for looking.






    Member
    simon5 on #3567

    Very fine work !

    I hope you will like the sound of them, the build quality is nice and the look is awesome !

    Can you do a close up on the logo ? 😀


    Member
    dlneubec on #3566

    Thanks!

    I’m extremely happy with how these sound. They are the best I’ve done. Before I started on the veneer and final finish, I had these in an all mdf version with a couple months of listening and crossover tweaking in.

    The TD12H woofer is simply the best I’ve heard. It is clean, accurate, goes plenty deep for music in a pretty small box and very dynamic. I had this speaker at a DIY meet in its prototype stage back in November and it received great reviews. The guys were amazed by the TD12H.

    I’ll see what I can do about a logo closeup.


    Member
    dlneubec on #3568

    They are finally complete! Below are the final details for the BaSSlines design. I’m extremely pleased with the results, which I believe are my best effort so far.

    Included below is the crossover schematic, the simulted frequency response, the simulated polar response from 500-3500 in 500hz increments, the parts list (using all PE available crossover parts) and cost estimate for the pair, not including the lexan, the hardwood, mdf or veneer and finishing supplies and a photo in our main room.






    Member
    simon5 on #3569

    Great work ! Kinda complicated crossover, but if it does the work, that’s what counts ! 😀

    You did an awesome finishing job.


    Member
    PUREAUDIO on #3570

    WOW…. That is awesome looking i love the design. Ive been wanting to build a set something like that for years buy just dont have the time (maybe one day). The craftmanship of the woodwork is second to none, love the two tone.

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