Retirement Speaker Build

Discussion in 'DIY' started by SirReal63, Jul 5, 2018.

  1. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country
    Hello AK, I thought I would do a little documentation of my current speaker build.

    I have always been an admirer of the JBL 250 series, the shape, elegant lines and size has always made me appreciate the style and art of Greg Timbers. I have lusted after these for a long time, but other financial responsibilities and the gypsy like atmosphere of my career made it impractical to buy a set of them, complete with the sub. I had a hard enough time moving my 1983 Genesis 210's which I faithfully did until 2007, and regret letting them go every day since.

    I do not really want to deal with getting an older set of 250's and having to rebuild them back to better than new condition, which I would insist on. So I examined what I liked the most about them, it was the elegant shape. I decided to go way beyond my abilities and design my own. I thought I had a clue on how to do this, then I figured out that the more I learned the less I understood, and the more I must learn. I have changed my design several times now, and hopefully I have it figured out. (I bet I have to change things again before I am happy)

    Lansing Heritage (audioheritage.org) is an amazing place with more information than I would have thought possible. I was able to get the exact dimensions, drivers specs, crossover specs, internal bracing and everything I did not need, but without them I doubt I would have started this.

    With the help of many resources on the web, I made my design.

    The base is 24" wide and the top is 12.5" wide, the short leg is 48" and the long leg is 49.25 giving a 48" tall speaker that is 12" deep. Originally I had designed it to be 53" tall instead of 48" but it meant a lot of wasted veneer and added nothing to the acoustics.

    I did not take any pictures of building the box, there are plenty of those out there.

    After the box was built and partially braced, I noticed an issue, the base had a sharp transition on the sloped side. I made it the way I did to help prevent the issue the 250 had, the veneer coming off the bottom.

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    Veneer does not like sharp transitions, so after a lot of thinking I decided to sand it off to remove the sharp transition and allow the veneer to follow the contour.

    I ended up with this, my veneer guru approved it.

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    A shot of the woofer area and the bracing. This cavity is 2.5 cu. ft. with two 2" ports, one facing forward and facing back and tuned to 30 hz. I hope I do not need to add any more bracing, but I know it is possible. I was able to stand on it with my 190 lbs and had no deflection.

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    The upper part of the cabinet.

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    The cabinets after filling, sanding, shellac and finish sanding, ready for veneer.

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    The veneer is flat cut Teak from Veneer Factory Outlet, Bob is a great guy, he answered my questions and took more time with me than I expected.

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    The drivers are not JBL or even high quality drivers, but the specs indicate they should work well together.

    The tweeters are Eminence APT 200 horn loaded drivers, they will be crossed to 3500 hz and above. There will be an L-Pad to attenuate as needed.

    The mids are Faital Pro 6FE100 limited to 3500 hz on the high end and 100 hz on the low end. This should work well as the faital's get peaky above 3500. There will also be an L-Pad to attenuate as needed.

    The high and mid will be wired in parallel to get to a 4 ohm load.

    The woofers were a challenge and they get replaced. They are GRS 12SW-4 and are really a subwoofer but do reach 700 hz, they will be crossed to 500 hz and below, these are 4 ohm. I chose them because they were a perfect fit for 2.5 cu. ft. and 30 hz. They were inexpensive so if I have to change them I can. I suspect I will not have to.

    The parts layout.

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    The rear panels are in two parts and will be held in place with 1/4-20 SS bolts and insert nuts to allow easy removal.

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    The crossovers are cheap Dayton parts, which is ok, the long term goal is to use an active crossover. I have this set up for a bi-amp system but with the bridges it can play with a single amp at 8 ohms.

    The amps I chose are simple and inexpensive, the mids and tweets will run off a Sonance 260x3 at 4 ohms which will send about 50 watts to each speaker. The subwoofer will be run off a Sonance 275x3 at 4 ohms which will send about 120 watts to each. I really like these amps, they are bulletproof and over built. They are designed to sit in a closet and be forgotten, the auto on feature is great and they are stable down to 2.7 ohms. After hours of use they are barely warm.

    The pre-amp is an Outlaw Model 950 which was not my first choice but I am happy with it and the price was unbeatable.
     
    Last edited: Jul 5, 2018
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  2. shelly_d

    shelly_d Not An Audiophool

    Messages:
    6,371
    Location:
    Alameda CA
    I'm sure these will look great and doing it yourself ALWAYS sounds great:bigok:

    Have fun with it.

    Shelly_D
     
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  3. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country
    Thanks, it has been fun but the real fun comes with tuning. This all got started because I have a shelf of car speakers, all new, that have never been installed. I thought it would be fun to use them and build a set of speakers for my shop, then it blossomed into this. The wife is happy, I am staying out of her hair. :D
     
  4. KingBubba

    KingBubba "Too Much Stuff"

    Messages:
    9,441
    Location:
    Brooksville, Fl.
    Interesting project. I personally would never consider undertaking a project as big as that. You are indeed brave and smart. I hope they give you great enjoyment.
     
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  5. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country
    Not long ago I would not have either, but after taking on building my own 3500 sq. ft. two story Barndominium this was like a vacation.
     
  6. TudorTurtle

    TudorTurtle Well-Known Member

    Messages:
    620
    Location:
    Upstate and Downstate NY
    Regarding the veneer, does your guru have concerns about "seam popping" where the mdf top and base meet the the baffle?
     

     

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  7. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country

    No, the only area of concern was the sharp edge that was sanded off. Do you see something that needs to be addressed?
     
  8. TudorTurtle

    TudorTurtle Well-Known Member

    Messages:
    620
    Location:
    Upstate and Downstate NY
    I'll reply in full later today when I can get off the phone and onto a laptop, where I can grab the pic and explain better.
     
  9. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country
    Ok, thanks. All of the edges were sanded smooth and flush, the both boxes were coated with shellac and sanded twice, final sand was with 220. The substrate is about as perfect as it can be for PSA. If I need to fix something, now is the time.
     
  10. TudorTurtle

    TudorTurtle Well-Known Member

    Messages:
    620
    Location:
    Upstate and Downstate NY
  11. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country
    Have you had this happen to you? What am I missing? I am always grateful for advice.

    The edges are sealed and perfectly flush with the baffle. The PSA is adhering to the shellac and not directly to the edge of the MDF.

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  12. TudorTurtle

    TudorTurtle Well-Known Member

    Messages:
    620
    Location:
    Upstate and Downstate NY
    Yes.
    It is/was due to the shrinkage and expansion of the MDF. IIRC, the MDF had more change on the flat side than edge-wise. I also had the cabinets in a region that was VERY dry in winter and then humid in the summer. The cabs were sealed like yours. As soon as my cabinet making buddy (a full time pro) saw them he warned me about seam-popping, and 8 months later, there it was. I'd edge-band the top and bottom edges, and then the minuscule change in dimension will never be seen.
    Ask your guru if he thinks I'm off-base, and follow his lead.
    All good,
    TT
     
  13. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country
    I can see that happening. I have a message in to my guy, will heed all warnings. I have a 250' roll of Teak edge banding as well but should have enough scrap to keep the grain direction consistent.

    I am also mostly sealed on the inside of the box and this is Texas, climate controlled year round, the mini splits never turn off. :D

    Thanks for the heads up.
     
  14. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country
    My veneer guy isn't concerned, he said in a climate controlled environment there should not be any moisture movement beyond the normal interior humidity, which in our case is not high and fairly constant. Time will tell. I will go back and finish sealing the interior, that should help slow down and absorption, just to be safe.

    The good news for the day is the Teak arrived! Veneer Factory Outlet did an awesome job on selection, there is a 2x8 sheet on top of the 4x8 and the look and color is consistent between the sheets. You may not know there is a smaller sheet on top of a larger unless you look very closely. Overall, I am impressed.

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  15. slimecity

    slimecity Super Member

    Messages:
    2,588
    Location:
    New Zealand
    Does shellac seal the MDF? Those edges look like they need to be sealed better so a glue (that sticks the veneer down) will stick better to them.
     
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  16. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country
    Yes, it seals the MDF and provides a good surface for the adhesive. The edges are an optical illusion, they got two coats with as much as I could get on the edges, the flash makes it look like bare wood, but it is not.
     
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  17. 7.62

    7.62 Gearhead Subscriber

    Messages:
    1,333
    Location:
    Las Vegas
    I admire your woodwork, it looks really nice. Saw your other post in a different forum. Looking forward to seeing the rest of the build come together.
     
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  18. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country

    Thanks, it has been a lot of fun.
     
  19. gdmoore28

    gdmoore28 Super Member

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  20. SirReal63

    SirReal63 New Member

    Messages:
    37
    Location:
    Texas Hill Country
    Cabs have been veneered, only a couple small hiccups. First coat on Danish Oil is on the fronts, I think it will look just fine.

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