3Rutu5 Micro Boombox

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Guys, I've finally decided to use the ND65-4'S for good after seeing where I went wrong the last 2-3 times.

2* ND65-4 drivers
BSC - 4 Ohm resistor, LW18-50mh inductor
2.1 Hi-Fi Class D amplifier Board
Bluetooth receiver from china

Enclosure 0.047cuft (internal)​​​ each, 20mm port 100mm long tuned to 70hz (F3 @ 60hz). Lined with generic waddling. Made out of 12mm dressed pine, using two pieces (1200x80x12 and 1200x140x12). The box construction was a bit lazy and just glued the pieces together and then ran around with a flush router bit and a sanding block. Turned out better than expected. There is something therapeutic about sanding by hand with a block, quite enjoyed going through the grades getting that cheap pine looking fine. (first set of photos pre sanding obviously)

Power is using a 3S BMS, 3*18650 batteries.

Did a dry run all working, but had to disable the battery as I'm still trouble shooting the error, but runs great off 12v. Pulled apart to paint and got a bit creative with some clear adhesive used to cover kids books, print and a scalpel and tried the spray paint alternative. Not.everyones cup of tea and I stuffed up the mouth, but confident in a.easy fix considering I have to give it a clear coat.

The speakers sounds really good, no distortion at Max power and glad I gave them another chance. There is enough bass for the portable application and quite impressed considering the size of the box,

I'll put up the finished pics over the weekend


Spray paint and stencil. Needs a sand in a few spots to get rid of the bleed, which was me being impatient. Next up clear coat and assembly


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Finished product. hot glued the drivers inside but will screw once i get a screw or option that wont go through the timber. Pulled the 3S battery system out, will investigate into why it wasnt holding charge, sure it is user error. Also need to clean a bit of the hot glue off the left driver, but apart from that, really happy with how it all tuned out. No distortion at all, but i did notice at max volume the sound would randomly cut out, which happens around the 6min mark in the video, but not sure if this is referred to as "clipping" so changed the input voltage to 18v on the wall pack and it may have eliminated it, it was a noticably louder sound with the modification.

using tomzarbo 's Micro B guide i've hardwired the audio input from the Bluetooth board to the amp and installed a 2 volts LED light on the rear which turns on when powered up. No real ground loop, except for a very very very mild hum when sitting idol, which i think my pc speakers may do when on but not used. My wife didnt even notice it.

Uploaded a soundtest onto youtube, using royality free music and just picked due to having bass and not normally the style of music i tend to listen to. with mild internal lining I really like how this little thing sounds and extremely happy that i didnt do what i first wanted to by throwing them in the bin 12 months ago. They are a nice little driver, albeit 65mm (ND65) is a bit of a stretch as this things are 2 inches in size and the 2.5inch size is more like an external measurement.


I will apologise in advance, i do not have any fancy recording gear, just a Google Pixel 2 XL which has been smashed to hell, but seems to have turned out ok, maybe just a bit bass'ier in real life.


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