New portable 2-way boombox build

[jdhill]

This will be my last project for a while, at least until the weather gets warm again. I've built a lot of boomboxes but none of them have been battery powered -- maybe they are more accurately called 'tabletop radio'. I wanted to give that a shot and also try something with a basic crossover.

The drivers are the ND65-8 and the ND16FA. The woofer plays full range and the tweeter is high-passed somewhere north of 3000Hz (I think?) using a 3uF cap and an L-pad. The box is tuned to around 60Hz using a 5" long port made from 1" PVC. The internal volume is about 210ci but with all the components the net is more like 180ci.

I'm using the Dayton KAB-BE battery boards, two of them wired in parallel using the included connectors, and some LG flat top 18650 cells. I was concerned about using them without one of the Dayton/Sure bluetooth amp boards, but I haven't had any problems so far. They're wired directly to the charging port and I added a voltmeter to keep an eye on the charge level. I am using a 19V supply for charging and the TA2024 amp and BT4.0 board are only rated to 15V, so the circuit disconnects the audio components when charging. This means it can't play when plugged in, but with ~5Ah on tap I hope it won't need to charge often.

I'm extremely pleased with the sound. The ND65 is a surprisingly powerful little driver. At the end of the day I'm not sure it even needed the tweeters, but the end result has been very satisfying.

I have more build pics if anyone is interested.

[ceiol]

beautiful work

amazing that those tiny ND65-8 drivers will play down to 60 Hz !

[Chris Roemer]

Too late now (prob'ly), but in general, 2 woofers playing diff. signals (stereo) should each have their own vented space. A driver (driven off air pressure - even sound) will generate voltage as it moves - much like a microphone. Looks great though. Same volume and tuning I used w/my "femtoneo" design (tweeterless). What the tweets add (mainly) is some HF dispersion, probably giving a much more "open" sound.

[Gordy]

I believe the KAB=BE boards have over/under charge protection. There is some script on the bottom of the board that outlines the specs. Maybe I am missing something but do the boards not have the over/under charge protection?

[tomzarbo]

Nice job! That's a nice looking project. I love the angled wood slats on the front, kind of artsy-fartsy in a good way. ND65's are pretty cool little buggers right?
TomZ

[nicholas_23]

Very nice , I like how you varied the shade and color on those front angled pieces 

[jdhill]

I believe the KAB=BE boards have over/under charge protection. There is some script on the bottom of the board that outlines the specs. Maybe I am missing something but do the boards not have the over/under charge protection?

As far as I can tell they do, which is a good thing because I am using unprotected cells. When I plugged it in the voltage display read ~10V (they were already partially charged) and over time it worked it's way up to 12V. The next time I looked at it, it read 19.2V, the supply voltage. I assume this was because the circuit disconnected the supply from the batteries once they were fully charged, and I was reading the voltage at the supply.

So far I've played it for about 2-3 hours at medium volume and it's still going strong.

Assuming I'm not doing anything boneheaded, this means the battery board can be used with any amp and still provide charge protection, which IMO makes it a nice value.

[Jamesbil]

Love this build! Hoping to do something similar, with the addition of an input jack and ability to charge phone via usb. What are the 4 buttons on the top?

[jdhill]

The four buttons are, clockwise starting with the rocker switch: audio power on/off; voltmeter display on/off; not a switch -- actually a spring-loaded cover for the DC jack; the volume knob.

USB charging would be easy, someone on this forum recommended picking up one of those panel-mount 12V usb chargers off the 'zon or some other site.

Input jack is a little trickier, you would have to wire a panel-mount jack to a 3PDT switch opposite the bluetooth board. I guess the tricky bit is more where to put all the wiring. Good luck!

[Jamesbil]

Can you give a little info on your crossover setup?

[jdhill]

There's not much beyond what I stated in the first post. The woofer plays full range, the tweeter has a 3uF cap in series along with an L-pad consisting of a 3ohm series and 6ohm parallel resistor. It's definitely not anything pro quality, half of it was parts I had on hand, but it sounds good enough to me.

[Millstonemike]

Really sharp design.

And thanks for confirming my guess that the KAB battery boards will manage the batteries without the KAB amp. Bit you do have to manage maximum charge current - something you would have to account for if using, say, a 24V Meanwell DC supply.