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  • Beach Wagon Build

    So over the past year I've built the TriTrix in a ported bookshelf and the Overnight Sensations, also ported. I'm currently building the AviaTrix MLTL towers for myself—the others were gifts for family.

    Of course I've told friends about how much fun it is, and my buddy gives me $160 cash to search Craigslist for parts, parts for a beach wagon with a cooler and sound system, plus spots for chairs, umbrella, etc. He rebuilt an old Lowe's gardening section wagon with inflatable tires to fit the cooler up front and the rear 2/3 for the sound system and related stuff.

    Plan is to run everything off a 12 Vdc automotive battery (or smaller, if need be). Sony headunit and four 6.5" coaxial speakers have already been sourced for $50, and I ordered a single 8" Dayton SD215A-88. I've been toying with WinISD alpha and have come up with this box:

    1.0 cu ft tuned to 43 Hz using a 10.25" long slot port (6" wide x 1.5" high). Ports edges will have a 1/2" round over.

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    It's the first time using it to actually design something myself... I wanted a good bit of boost because it'll be in an outside environment.

  • #2
    Re: Beach Wagon Build

    How much space do you actually have to work with?
    Brian Steele
    www.diysubwoofers.org

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    • #3
      Re: Beach Wagon Build

      I have a 24" x 20-3/8" external footprint to work with. Could probably go 15" in height before it starts getting too big.

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      • #4
        Re: Beach Wagon Build

        We used the T/s parmeters to design a box for the car speakers in my bike trailer build, f3 is just over 50 with a 2 db rise at 100hz. Doesn't sound to bad for not having a sub.
        "As you start traveling down that road of life, remember this: There are never enough comfort stops. The places youíre going to are never on the map. And once you get that map out, you wonít be able to refold it no matter how smart you are." -kermit the frog

        a good place to check out http://www.midwestaudioclub.com/

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        • #5
          Re: Beach Wagon Build

          Originally posted by JoshuaC2U5H View Post
          I have a 24" x 20-3/8" external footprint to work with. Could probably go 15" in height before it starts getting too big.
          So, basically around 1.6 cu.ft. net, which is going to turn out to be a bit less once you factor in things like the battery, the amp, etc. . Looks like you're off to a decent start with the SD215, though I do suggest leaving your options open. What are your plans to provide the rest of the audio spectrum?
          Brian Steele
          www.diysubwoofers.org

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          • #6
            Re: Beach Wagon Build

            Originally posted by Brian Steele View Post
            So, basically around 1.6 cu.ft. net, which is going to turn out to be a bit less once you factor in things like the battery, the amp, etc. . Looks like you're off to a decent start with the SD215, though I do suggest leaving your options open. What are your plans to provide the rest of the audio spectrum?
            I'm going all mobile audio since this isn't going to be playing in an environment where fidelity is primary target: Alpine headunit and four 6.5" round coaxial car speakers to take care of everything above 80 Hz or so (I'll play with the highpass built in to the headunit). They are going to be mounted basically anywhere along the exterior of the box—the subwoofer and its enclosure take priority, with everything else on the wagon being built around it. The compartment(s) for the battery and other gizmos (four-port 12 Vdc USB charger, etc) will be separate from the subwoofer volume.

            The build starts this Saturday, and the SD215A-88 is already ordered. I was looking for someone to double check what I had so far to make sure my excursion is within check—from the plots it looks like in nears its 6 mm Xmax at 57 Hz when driven with 80 W, which is the maximum size amp I'm looking to drive it with (whatever I can find on Craigslist).

            The frequency response looks okay to me with a 3 dB over reference at 53 Hz, then rolling off for an f3 of 38 Hz or so. The only plot I didn't show was my SPL, but if I remember from glancing at it, it was over >97 dB on all frequencies in-band. Being my first modeled box, I'm banking on using the amplifier gain to dial in the amount of subwoofer fill.

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            • #7
              Re: Beach Wagon Build

              Just in case you're open to options, how about instead of the head unit, you design around using an MP3 player as the source? Your amps can be those 2x50W class D units available from PE, and because this is all being squeezed together in one box, you could use simple 6dB/oct filters around 200 Hz between the SD215 DVC and the "main speakers" (consider 4" full-rangers for this purpose, with sensitivity rating below the SD215 to make the x-over work a bit simpler.
              Brian Steele
              www.diysubwoofers.org

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              • #8
                Re: Beach Wagon Build

                Josh, have you sourced a power amp yet? Your head unit will provide maybe 12 watts @ 4ohms per channel. Outside, that's not very loud at all. I don't know if your head unit will play USB sticks or MP3 files on CD-ROMs. Both are handy. A USB port will let you bring a portable USB drive with DAYS worth of music on it, and some head units will let you access the files automatically. I've seen audio trailers from motorcycle pulled to dual horse trailer sized (and "toy hauler" space in the rear of a normal RV trailer). Plan on a couple of big-dog RV batteries. Without anything going into them, batteries drain amazingly fast. (Long time RVer.) Two of the monster semi batteries will keep a small RV "off-grid" 7-10 days if you are super careful, drawing less than 1.5 amp/hour average. We're talking 100% LED lighting, no more than a couple of hours of laptop use for entertainment (music/video) a day, and the water pump. When they hit 10.1 volts, that's all there is. Suck 'em below that and you have to buy new ones. If you camp primitive,even a tiny 1 Kw genset whizzing away for 2-3 hours a day while you're gone seems like Heaven.

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                • #9
                  Re: Beach Wagon Build

                  Originally posted by Brian Steel
                  Just in case you're open to options, how about instead of the head unit, you design around using an MP3 player as the source? Your amps can be those 2x50W class D units available from PE, and because this is all being squeezed together in one box, you could use simple 6dB/oct filters around 200 Hz between the SD215 DVC and the "main speakers" (consider 4" full-rangers for this purpose, with sensitivity rating below the SD215 to make the x-over work a bit simpler.
                  I kind of wish I was thinking along those lines when I started, but I'm experienced in modile audio so I immediately jumped to that line of thought from the get-go. Maybe I'll build one for myself with some full range drivers and a sub. Thanks for the help!

                  Originally posted by Whitneyville1 View Post
                  Josh, have you sourced a power amp yet? Your head unit will provide maybe 12 watts @ 4ohms per channel. Outside, that's not very loud at all. I don't know if your head unit will play USB sticks or MP3 files on CD-ROMs. Both are handy. A USB port will let you bring a portable USB drive with DAYS worth of music on it, and some head units will let you access the files automatically. I've seen audio trailers from motorcycle pulled to dual horse trailer sized (and "toy hauler" space in the rear of a normal RV trailer). Plan on a couple of big-dog RV batteries. Without anything going into them, batteries drain amazingly fast. (Long time RVer.) Two of the monster semi batteries will keep a small RV "off-grid" 7-10 days if you are super careful, drawing less than 1.5 amp/hour average. We're talking 100% LED lighting, no more than a couple of hours of laptop use for entertainment (music/video) a day, and the water pump. When they hit 10.1 volts, that's all there is. Suck 'em below that and you have to buy new ones. If you camp primitive,even a tiny 1 Kw genset whizzing away for 2-3 hours a day while you're gone seems like Heaven.
                  Right now I have a used Alpine headunit with the aux input RCA cord coming out of the back that I got for $30 with remote and four poly cone Boss 6.5" coaxials for $35. I went for cheap because this box will be basically used as a nearish-field, outdoor beach wagon. It'll be within five to ten feet of the listeners most of the time, so cranking super loud is not a goal. Generally, design goals were to keep it under $200 total, full range playback using a subwoofer, and light so it can be pulled by his wife on the sand. The wagon will probably only go a few hours at a time, but I wanted to prolong whatever battery he decides on using... so I limited to one power amp for the sub and driving the speakers off the average 16-20 WPC from the headunit. I just don't think I'll be able to shoehorn in two separate amps while keeping airflow/cooling and weight in check. Main source will be a cellphone running Pandora or iPod plugged into the 3.5mm headphone aux jack we install. I appreciate all the suggestions!

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                  • #10
                    Re: Beach Wagon Build

                    OK, lots of people want 200 watts to the speakers (or more) and 400 watts to the sub (or more) and that eats battery power. On the kid hang-out Memorial Drive, the fancied-up Hondas sit there blasting giga-watt stereos with a half-dozen yellow-top Optimas being helped by double alternators with the engines using an up-idle switch.
                    You have reasonable expectations, but go to an RV parts dealer and buy a battery monitor (LED type). They run about $20 or less now and like mine in my RV trailer has 4 green LEDs for good battery voltage, two yellows for dropping, and BRIGHT red one for stop using battery power. It's shows the voltage based on the LED. On mine, the red LED lights up at 10.5 volts for safety. 4 Greens = 14.1 volts or better. If you go to Exide's or Interstate's web-sites, you can learn a ton about lead-acid batteries, the better lead/calcium-acid batteries.

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                    • #11
                      Re: Beach Wagon Build

                      Here's what we came up with:

                      Large 3/4" MDF enclosure that takes up the rear portion of the wagon with 6" of space left in between the enclosure and cooler for beach chairs, umbrella, etc. Subwoofer portion of enclosure is separate and is 1.5 cu ft with a 6" x 1" x 6" slot port to tune it to 36 Hz and an f3 of 30 Hz (not that it matters outside). Modeled with WinISD with an 80W input, shows 107 dB at 40 Hz, although the Xmax will be pushed a bit... good thing they're only $30 a piece to replace!

                      We used a medium-sized sealed 12V battery to run everything: Dual headunit and older Kenwood two-channel amp, ran in bridged mode (specs say 150W RMS x 1 @ 4 ohms, so I'm assuming around 75-80W RMS @ 8 ohms as I've wired the sub for), and four cheap Dual 6.5" coaxials. We also got a cheap 12V cigarette port with two USB slots for charging of phones or whatever, to be fused and wired directly to the battery on a switch. The 12V remote turn-on for the amp runs through a toggle switch so we can turn it off to save power. The side has a removable panel to access headunit/speaker/battery wiring and components... it's pretty tight. Kind of worried about heat, especially with it being used outside in the sun all day... maybe some vent holes?

                      Still have a few things to do like flush trim the top and bottom panels, a lot of wood filler and sanding, and finish paint + sealer (clear coat or poly)... my friend is still not sure how he's going to finish it.

                      ALBUM LINK: http://imgur.com/a/Ct64d

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                      • #12
                        Re: Beach Wagon Build

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                        • #13
                          Re: Beach Wagon Build

                          Sweet box! How much does it weigh? So you've got top and side firing co-axials?
                          -Mike

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                          • #14
                            Re: Beach Wagon Build

                            Originally posted by Alien_Shore View Post
                            Sweet box! How much does it weigh? So you've got top and side firing co-axials?
                            I think it's about 40-45 lbs loaded up, mostly the box and battery weight. Very realistic being pulled on the wagon, though it may sink a bit in the sand, haha. Might have to up the tire size/width a bit for some floatation.

                            It's just a sound box—no critical listening whatsoever, so we threw the speaker wherever we could (two out the back with the sub, two firing up with the headunit on top). It sounds good enough for a party machine. I do need to add a cap to each speaker though as they're getting caught up in the bass too much (no internal crossover built into the headunit).

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                            • #15
                              Re: Beach Wagon Build

                              Do the 2 co-axial drivers and the sub share the same space?
                              Don't worry, if your parachute fails, you have the rest of your life to fix it.

                              If we all did the things we are capable of doing, we would literally ASTOUND ourselves - Thomas A. Edison

                              Some people collect stamps, Imelda Marcos collected shoes. I collect speakers.:D

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