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Ideas for BT Boombox with a difference....

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  • Ideas for BT Boombox with a difference....

    The attached image is the Sharp QT-37 boombox, one of which I owned years ago and thoroughly enjoyed (and yes, my own was red too!). It used to accompany me almost everywhere, including the beach (which of course led to me learning a lot about its innards as I had to open it every month or so to clear the sand out. At home, I'd disconnect the speakers from the center console and set them wider apart for better stereo imaging.

    Unlike most other boomboxes of the time, this one had one little "trick" that helped the user to obtain a nice wide stereo image when it was set up for use at home - the speakers are detachable, and were connected to the center "console" by 1~2 ft cables that were wrapped up on spools behind each speaker and connected to the console via 3.5 mm phone connectors.

    For this year's project, I'm considering building something that's a bit of a homage to the Sharp QT-37 (i.e. keeping the detachable speakers and the bright red/black angular look), but at the same time dealing with some of its deficiencies. In particular, it had no BT connectivity, little bass to speak of and those 3.5 mm phone connectors were a bit problematic - connectivity got spotty with reuse). The speakers themselves were technically 2-way, but the little piezo tweeter hidden behind the chrome thingy really did not add much to the overall response of the speaker, which was a little on the bright side. The center console did have a "tone" adjustment which could be used to bring the brightness down somewhat. The extra brightness actually helped a bit when the boombox was left on the ground rather than mounted on a table or something higher.

    So, my ideas so far:

    1. Go a little larger, the aim being to fit a bass module into the center console, using a PR to reduce ingress of sand or other crap into the unit.
    2. Electrical connection of the speakers to the center console done via whatever is used to physically connect the speakers to the center console (no more 3.5 mm jack). The speaker cables will be left home when I'm taking it to the beach, etc.
    3. For use at home, some means of securely connecting external speaker cables from the center console to the speakers that did not take up a lot of room on the unit (e.g. no "banana jack" or speakon terminals)
    4. Proper "2-way" speakers. I'm thinking ND16s for the tweeters, I haven't decided what to use for the main speakers or the subwoofer yet. Main speakers x-over at around 100 Hz.
    5. Battery-powered of course, with the use of rechargeable batteries. I haven't decided if I want to include the recharging in the unit or allow the batteries to be removeable for recharging purposes. I will probably go for the former, because
    4. I want the finished unit to be as water-resistant as possible. I'm not going to be dunking it any pools, but it should be able to withstand the occasional splash or spilled drink, so for example the use of paper-coned drivers is likely out of the question.
    7. I'm aiming for a high-quality tough finish for the unit. Maybe just go by one of the car-repair shops and have them put a few coats of red paint on the finished unit.

    So, that's where I've reached for the moment. Any ideas you have about how best to accomplish this build will be very welcome!

    (the second picture is for scale, and not that's not me. That's SWMBO about 5 years before we tied the knot :-). Lots of good memories from that time in my life, so ...)
    Brian Steele
    www.diysubwoofers.org

  • #2
    Seems to me is they will 'slide together' like most detachable speakers, you could place metal spring contacts at the bottom of the slides. When attached, the speakers connect this way.

    Honestly, I see Speakons as air and water tight, and obviously the best choice for cabling to the speakers from the central unit if detached. I suppose a pair of retractable power cords cut and used as 2-pole wires secured to the rears of the speakers or inside the central unit could suffice for connection.

    For durability sake, metal cones and dustcaps will resist UV better than others, and take the possible problems you cite. I feel a santoprene surround would be better than NBR, or maybe a polymer impregnated cloth like prosound or the 4" GRS. Neo magnets would help in the weight category. Would prosound coaxes like the B&C 5FCX44 suit? Usable in about 5 ltrs. An extra fabric grill (or 2 layers) inside the outer metal grill may help keep sand out better.

    Half inch ply and professionally truck-bed-lined exterior (Line-X?) would likely be the most durable, and they can likely do that in red.

    Later,
    Wolf
    "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
    "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
    "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
    "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

    *InDIYana event website*

    Photobucket pages:
    http://photobucket.com/Wolf-Speakers_and_more

    My blog/writeups/thoughts here at PE:
    http://techtalk.parts-express.com/blog.php?u=4102

    Comment


    • #3
      Marine grade plywood to help resist the humidity changes.
      Truck bed liner for protection, It might be kinda thick and textured for sliding the speakers on to the center box.
      Li-ion batteries with charging jack
      A pair of vertically oriented screws for speaker connection. Use a hurricane nut inside the enclosure. Straps, like for biampable speakers, when they are attached. Cables for detached.
      I'd take a look at car and marine speakers, something that's intended for use in a harsher environment. Don't forget coaxials.

      A handle that your significant other can comfortably use. She can carry the boombox while you carry the cooler of beer

      Comment


      • #4
        Originally posted by Wolf View Post
        Honestly, I see Speakons as air and water tight, and obviously the best choice for cabling to the speakers from the central unit if detached.
        Oh, Speakons are great connectors. The main issue I'm seeing with their use here is simply the size of damned things. They will be huge compared to the size of the unit, and especially when compared to the size of the speakers. I'm thinking of going with simple keyed molex connectors instead. They're small and should provide a secure connection.

        I'm looking for the perfect sliders for the job at the moment. "Perfect" would be metal sliders, to ensure maximum electrical contact between the central unit and the speakers, and high durability of course.

        I really want to keep the "2-way" look, so I'm not really considering coaxes at the moment. Implementing a good speaker grille might be a problem though, so I might end up reconsidering that, as it might just be easier to re-purpose the grilles provided with car audio speakers. The speaker boxes are going to be small and sealed, aiming for a Qtc of 1 or higher and hopefully use active HP filtering at Fb.

        Brian Steele
        www.diysubwoofers.org

        Comment


        • #5
          Steve Meade has a magnetic box terminal, this unit here:
          http://www.wccaraudio.com/1-channel-neo-terminal.html
          I suspect something like this on a smaller scale would not be too difficult to rig up.

          Comment


          • #6
            Aah beach sand. It gets everywhere. Yes, even there. Ask her.

            I think the first issue is to decide the format: 2.0 or 2.1 boombox. From there, you can select from a number of known, DIY 2-way speaker designs where the finished product has received accolades for it's sound.

            Second issue is power, on several levels. You should stick with 4 own drivers as they get twice the watts out of an amp for a given battery supply voltage. That's why all car drivers are 4 ohms given the standard 12 V auto system. And the battery supply voltage will dictate max power out to the drivers (not the "labeling" on the amp).

            For a 2.1 boom box, Paul Carmody's Isetta design has received many great reviews and there's at least a dozen builds here and on the PE's project gallery to peruse. There's a great 2.1 BT amp available at PE that's commonly paired with the Isetta design. The only issue I see with that design is you'll need a 5S Li-Ion battery pack for a nominal 21 Vs into the amp. PE sells a 5S battery management module (just add 68650 cells (another dissertation purchasing batteries when you get that far). Add a 24 V power brick to charge the unit and to run on wall power when AC is available. Using a 12 V battery will limit output, especially with the Tang Bang W5-1138 woofer's lower sensitivity. An alternative to the Isetta is using the The C-notes or Overnight Sensations with a sub in the center. While those designs are 8 ohms, they'll outplay the single ".1" sub SPL wise (the 2.1 amp's controls will allow volume matching).

            For a 2.0 box, again look to existing 2-way DIY speakers but limit your choices to 4 ohm designs. You can use the same amp, just ignore the ".1" output. Or provide the ".1" output on a connector in the back to connect a passive sub when desired. And my recommendation on needing a higher voltage battery stands as well.

            You'll be limited to BT and 3.5 mm jack as inputs. So without a CD or cassette player, the only openings on the box will be the port(s) for the bass reflex enclosure. Use the box material of your choice, just seal it well with an appropriate water proof finish. Just avoid any woofer with a phase plug with an opening in the center (sand in motor drive).

            A little overkill for your needs but here's my rendition of beach boom box. I love seeing some 500 people standing with hands on hearts when I play the Star Spangled Banner in the morning at 106 dB

            Oh, and make it serviceable. Salty beach air tends to degrade things over time.


            Click image for larger version

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            Comment


            • #7
              Super cool idea. Seems so obvious now that you mention it - something with either two or even just one detachable speaker so you can have better area coverage. One could possibly modify a Blast Box or MK Boom for this.

              Maybe consider construction out of plastic. I have been playing with PVC a bit lately and it is easy to work with. You can get 3/4" thick 'boards' up to 10" wide and 12feet long from Lowe's, HD, etc. for very reasonable prices.

              How about using a speakon connector to actually mount the speakers to the main unit? Just plug them right onto each side. Then possibly a compartment in the main body for a pair of 1m cables when they are detached? I have not played much with speakon connectors so I don't know for sure how well they would hold the speakers to the main body - might need some neo magnets to supplement them?

              Comment


              • #8
                Neo-connectors...
                I'd wondered about how to do that, and now it makes sense. Big Box or PE sell Neo ring magnets. The connector could be either the ring or the center, depending on your methods.

                The french cleat type of speaker hanging system might provide a metal slide system.

                Later,
                Wolf
                "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                *InDIYana event website*

                Photobucket pages:
                http://photobucket.com/Wolf-Speakers_and_more

                My blog/writeups/thoughts here at PE:
                http://techtalk.parts-express.com/blog.php?u=4102

                Comment


                • #9
                  Permanent connections via speaker wire as long as you want them. Out the sides of the main module. To the matching sides of the speakers. Depressions in the sides of the main module for room to stow wires for a flush fit. Cleats in the depressions to wind the wire.

                  Hardware: lift off or twist off hinges in front, latches in back.

                  lift off hinge at DuckDuckGo

                  metal latch at DuckDuckGo

                  Comment


                  • #10
                    Or hinges in back and neo magnets in front. Might need a grip of some sort to break the magnets apart depending on strength.

                    Comment


                    • #11
                      Originally posted by djg View Post
                      Hardware: lift off or twist off hinges in front, latches in back.

                      lift off hinge at DuckDuckGo
                      Ooh, I like the idea of the lift off hinges. Using two for each speaker could possibly provide the needed electrical connection needed to the amp as well,if I go with the "leave the cables at home" option.

                      Brian Steele
                      www.diysubwoofers.org

                      Comment


                      • #12
                        Originally posted by Brian Steele View Post

                        Ooh, I like the idea of the lift off hinges. Using two for each speaker could possibly provide the needed electrical connection needed to the amp as well,if I go with the "leave the cables at home" option.
                        That's a good idea, the connection via the hinges.

                        I used these latch couplers to hold the lid on my boom box for transport. I needed a fail safe method to hold the cover on. When I tried the hinge approach, they sometimes released during transport. The latches only release when you operate them.

                        Either way, get stainless steel for use in the salty beach air.

                        Comment


                        • #13
                          I used a small plate with a slot on the bottom of each side of the amp, and tabs on the speakers to secure the bottom, and some small latches on the top.
                          I decided to keep the 'source' separate, I use a sbc dac combo.
                          Click image for larger version

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                          • #14
                            Originally posted by Wolf View Post
                            Neo-connectors...
                            I'd wondered about how to do that, and now it makes sense. Big Box or PE sell Neo ring magnets. The connector could be either the ring or the center, depending on your methods.

                            The french cleat type of speaker hanging system might provide a metal slide system.

                            Later,
                            Wolf
                            What you'll find with the magnets is they hold very strong when pulling them apart. But they'll slide away from each other very easily.

                            Click image for larger version

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                            • #15
                              I agree with Mike,

                              Neo is super strong, but they need to be aligned really well. If they're off a bit, they really loose their ability to hold. I had a subwoofer grill that I slightly mis-alligned the neo magnets on and it has always wanted to 'kick-off' with a mild bump because of that.

                              You guys have some good ideas going on here by the way. I just wonder how you can keep beach sand out of the thing without keeping it in shrink wrap the whole time. I like the idea of using the hinges as a electrical connection as well; that's ingenius!

                              BTW, thanks Brian for making me look up what SWMBO meant.

                              TomZ
                              *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                              *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                              *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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