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"Bang Box" build thread

I wanted to build a portable boom box for work. I work in an engine test lab so the engines and emissions / supporting equipment is quite loud 80-89db in my console room. So i wanted something that would top out spl in the mid to upper 90's before breakup. 

Build / design goals

Have a funny name :) haha! Really the goals were simple keep it under $150 total. Consume less benchtop / toolbox / desktop space (less that my milwaukee jobsite radio), improve SQ and low end. Lastly, hopefully impress people at work and get them into speakers. 


Tang Band W3-2141 3" paper cone full range $33 each

Tang Band W5-1138SMF 5-1/4" Paper Sub $32


I upgraded the PSU to a 12v 5amp supply i had instead of the 12v 3amp it comes with. This amp was cheap price wise and appeared to have a ton of adjustability. It has tone controls for bass and treble on the L/R (-10 to +10 (probably not true)), a volume pot for L/R, a frequency cutoff for the sub and a seperate volume control for the sub. I have used the amp or gotten to measure any drivers at this point but im getting close. Perhaps i can get by without a crossover or just cutting the LF signal to it. Ill know soon if i can do that or not. 

Lepai LP-168ha-21  (2x40w and 1x68 sub). ($28)

1.5" X 9" port (PVC) for sub port X1 qty

Everything from like 7" to 10" should work in this enclosure. 

4" X 6" PVC  enclosures for FR drivers X 2 qty

I recessed a 1/2 thick plywood insert in tbe back of the pipe and recessed it into the baffle by about a 1/4 inch. Its approximately 1 liter internal volume.

The enclosure 

Approx 12 liter enclosure. (1liter for each driver, so approx 2 liters total + the 1/4" thick pvc sealed) and that leaves 9-10 liters for the sub (minus the external dimensions of the 1 liter cabinets with are 1/4" thick pvc. Its roughly 17wx8.5hx8.5d

Current minor holdup:

I'm currently looking for a more elegant way to install binding posts or something because I need to run 3 pairs of wires through the back of the cabinet. My thoughts are using a piece of plexi glass and just route out enough meat of the cabinet to have that I can attach binding posts (I have a ton of binding posts but they are like a bit less that 1/2 thick or something so they can't get through 3/4" thick mdf. I could disassemble them and use a forstner to rebate them into the cabinet by like 1/2 or something.  here are the binding posts I have

Lastly I bought this to wire them but I doubt I will use it. It says it's 14 AWG  but there is no way it is that 14, I got both 14ga and 16ga but the 16 seems like 20ga or 22ga and the 14ga seems like 18ga at best. For this power level maybe it's not necessary to use legit 16 or 14gauge but I have extra so maybe ill use it instead.

Ill get pics uploaded tonight after work. 



  • Hey Mike, do you have measurements of the W3?
  • Not yet, i used manufacturer specs....but ill get them once the box is together and post everything. I want to break them in for atleast like 4-6 hours before really taking any measurements. I really hope to make enough progress to get them going by the end of the week. 
  • If you really already spend 8 hours working in an environment that is as loud as you say it is you are already at the limits of noise exposure without hearing loss.  Anything above 85db is potentially harmful.  Be careful.

    Most of the small digital amps that I have measured put out about half the power the manufacturer rates them at before the start to clip. That should still be plenty with the drivers you picked.

  • It is 88db at the equipment source. I sit about 15 feet away so it tapers off but we monitor the level for our safety and i get yearly hearing tests. So far barely any change from when i started in 2001. I do wear hearing protection at times and when i will be listening to music it will be when its quieter or working on the engine. 
  • I clamped the front baffle on and installed drivers to check out the amp tonight. I was a long night and im off to bed now but whats frustrating is i had the crossover for the sub set to 50hz and its still playing guitar and vocals. Im not certain why its doing that. The sub enclosure if sealed at the moment i havent drilled the holes for the port. The tone controls work well but the sub frequency does not. The sub is clipping and i cant tell if its because its playing too high, has a small air leak or the amp cant power the low end. Im using the 3 amp power supply instead of 5amp.

    Im kind of confused now. Ill regroup with some shut eye but if anyone has suggestions let me know  
  • Why no pictures?  Come on Mike!
  • Lol it looks like its stairing at me!!!
  • Wall-eeeee! Ill let these play a few more hours after work tonight and get some dats (in box (sub is sealed at the moment but will be ported)) and FR measurements on the full range drivers. I can do measurements with tone controls normal, -10, +10 for both treble and bass to see what the actual output does. I can hear a significant difference messing with them so it actually works. The sub not cutting off is a big problem though. I might need to add a few crossover parts to this build if that sub crossover doesnt work. I was thinking about trying about 120hz for the sub and full range drivers. I need to try the bigger power supply as well.

    I wont be posting until late tonight/tomorrow i hit my stride at 1-3am now on second shift. 
  • Hope you get that amp to work. This has me thinking about a garage addition.
    ............. could you hum a few bars.
  • This is the Dat's inbox for the W3 Full range drivers They are a direct overlay for both drivers. In 1 liter sealed pvc tubes internally.

    This is the Bass Tone control Knob adjustments for the W3 full range driver ranges
    (-10, 0, +10). This function actually does work. I'm not 100% certain why the top end dip's off like that but I will try with a real amp tomorrow night or something.

    This is the "TREBLE" Tone control Knob adjustments for the W3 full range driver ranges
    (-10, 0, +10). This function actually does work as well

    This is the Near Field and Farfield of the W3 Full range driver no EQ for bass / treble

    This are the Dats data for the TB_ W5 5-1/4 sub

    This is the Sub cut off frequency pot test. I changed it in increments from 200-hz to 50hz. It really didn't change much at all. Also, I can barely add any power to the sub without it making a weird noise.

  • Well crap, I plugged the sub into the left channel instead of the sub output and it doesn't make distorting noises now. I don't know whats up with this thing but it's useless without the sub feature.
  • Sounds like you may have received a bad amp
    deadhorse - leviathan - harbinger - shockwave (wip)
  • Well, i ordered this amp to see how this goes. Nobsound® Tpa3116 Hifi 2.0 Channel Stereo Digital Amplifier Treble&bass Mini Amp

    I used a tiny dayton amp and my apa150 and it works perfect but the amp is almost as big as my boombox lol. 
  • Also, im finding it pretty frustrating with this class d china boards finding out which is good or bad. I have bought about 6 or 7 and only 2 have been worth it. The cheap $30 15w dayton brand black enclosed unit is actually good. 
  • What psu did you use a 24v 3amp? I just ordered the one you suggested too. 
  • I've been using a 12v, 5A that has been working fine. It gets louder than I need it to be without distortion. I intend to try a 19v, 5.6A laptop supply I have available. FYI - This is also powering a mini boombox with 2 4'" Peerless in parallel on the sub side and ND90's flanking a Tymphany tweeter in an MTM set-up on the flanks. In retrospect, this arrangement hardly needs a sub, but, ...why not?  =)
  • Mike your builds are always fun to watch.  Your woodworking craftsmanship is outstanding, especially considering that you've only been in this for like what, 5 years??  Awesome, but sorry to hear about the amp.  If you want to test an Indeed TA2021S for a 2ch mini boombox, let me know.  I've got a couple sitting around doing nada.
    My signature goes here
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