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Unnamed micro boombox build powered by USB

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  • Unnamed micro boombox build powered by USB

    I've only been building speakers for a few years now so I'm still pretty new to the hobby compared to some of the veterans around here. My main goal was something that I could use as an external speaker for my laptop, and something portable I could use when doing my workout at home when our son is born. I wanted rich full sound in a portable, compact design. Volume wasn't a huge concern, but it needed to be loud enough to enjoy it. Cost must be kept minimal. Parts already on hand were the drivers and amp.


    Design notes:


    My original plan was to include bluetooth, but after side by side, back to back listening comparisons with an aux cable and my bluetooth module that I thought was pretty good, it was clear that the bluetooth module killed the clarity and depth in the high end. When doing back to back listening, it was more noticeable than I originally thought.

    I didn't originally plan for it to be USB powered, but after looking at cheap boost converters on Amazon, I decided to give it a go.

    I did a few builds previously with passive crossovers and then did an active crossover. The flexibility to make adjustments after the build is complete with active crossovers is a godsend. I don't think I'll ever do another passive build again. I debated briefly making a shaping filter for low end/BSC, then debated a miniDSP board but decided against it since it will inflate the cost. Being a single full range driver and always being played from my laptop, I decided that for my situation the best solution would be to use Equalizer APO. For Windows computers, Equalizer APO is incredibly powerful software, allowing infinitely variable system wide EQ and audio adjustments. I'm a firm believer that equalization does NOT destroy sound if you aren't overboosting and clipping. If you want 100 filters per channel, at any imaginable Q level, it can do it without a single complaint.


    Build notes:


    This is my first rear mount driver build, and in doing so, I was focusing on getting the driver centered and forgot to get the mounting screws perfectly centered (this drives me nuts, but it could be much worse)

    This is my first build using a plastic enclosure. I always avoided them because I felt it would give a boxy, hollow sound. It did. After lots of testing, I settled on a bit of poly fill at the internal end of the port, some stick on weights on all sides, and some internal bracing. After this, it sounded as good as an MDF enclosure.

    Getting the leaks sealed sucked. You wouldn't know at first, but after playing some low frequency sine waves, it was clear where, and how bad the leaks were. After sealing them all up, bass response increased significantly. Being into automotive work, I had some black RTV which I used to seal the faceplate/front baffle once I was sure the box wouldn't need to be opened again.

    I was worried that the voltage booster would introduce noise into the amp because it was so cheap, but it's dead silent when not playing with no clicks, pops, or humming. I set it at 12.25v.

    I upgraded the large caps on the Sure amp with 1000uF caps in hope to help offset the low power input, so it doesn't cut out when the kick drum hits since it will be low power input (low amperage).

    I originally had the power switch on the ground side, but found out that the amp was grounding itself through the audio cord when I had both power and audio connected to my laptop. Switching to hot side switching fixed this.


    Parts used:


    The 8.54" x 5.43" x 3.23" project box

    Sure 8w x 2 class D amp

    Dayton ND91-4

    Drok variable adjustable voltage booster

    1" x 4" speaker port

    1/8" aux jack

    Micro USB connector pre-attached to board for easy soldering

    Rocker switch for power


    Conclusion/final thoughts:


    I'm extremely happy with how this build turned out. The simplicity paid off in that it does exactly what I wanted it to, sounds great, cost was kept to a minimum, and it looks clean. An added bonus was that it's easy enough on power that it can be powered from my laptop USB jack, and even my phone! If I turn it up too much, bass drums cause it to cut out unless it's powered from a 2a usb adapter. Reducing the bass I can get more sound output from my laptop and phone power, but that defeats it sounding like a larger, full speaker. I still need to replace the feet on the bottom of the speaker with some black instead of dark brown, but that's not a huge deal.


    Explanation of my house curve


    Over the past few years, I spent a countless amount of time messing with house curves, in room response, and EQ. Getting a mic to measure response was the best decision I ever made. I can tune and tune and tune by ear, and get it sounding "just right" but then put on different content and something is too harsh, bass is too strong or weak, or the high end is lacking. After all this testing, this is what sounds best to my ears. From 100hz to 1000hz is flat, from 1000hz to 10,000hz it slopes down at -1.5dB/octave, and from 10,000hz to 20,000hz it takes a sharp upward rise. This went against everything I had always thought: "well a speaker that sounds like that must be way too strong on the high end and very fatiguing to listen to. It was quite the opposite. The highs are very smooth and strong, but not fatiguing in the least bit, and the rise after 10khz accounts for most peoples weak hearing after 10khz while increasing airiness and ambiance of the speaker. Bass below 100hz is tuned by using sine waves until all frequencies *sound* equal in volume, given the speaker can go that low at the frequency. Getting a curve that sounded "just right" to me was the most frustrating part of speaker building for me, but now that I know what sounds good to me and what it looks like when measured, it's much easier. Measurements were taken at 6ft, on axis, before and after equalization.
    Attached Files

  • #2
    nice job!

    looks like a neat project

    Comment


    • #3
      I find the need for these micro boxes myself. Very nice for the kitchen or back patio in the summer. Eveyone does BT now, but i have come to the same finding as you that most non BT amps sound better. I have a bunch of those sure tpa3110, there pretty decent with upgraded caps. Throw some Nichicon kz on them if you like the smooth sound your describing.

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