Portable Speaker

Updated 30 June 2019

For a while now I’ve been looking for the ideal portable speaker to use with my wind controllers. I’ve bought a few (LG FH2, Nyne Rebel, Sony SRS-X2, Harman Kardon Onyx Studio 4), and while they all have their nice points, none of them really met all my requirements.

I’ve been playing with some concert bands, and what I needed (apart from good sound quality) was:

  • Reasonably small size (Sony, Harman Kardon)
  • Good volume (LG)
  • Ability to determine how much battery life is left (Nyne)
  • 1/4″ input socket (LG)

So, I decided to build my own. It looks like this:

Components

The components I chose were:

Drivers

Dalton Audio DS135-8 5″ Designer Series woofer. It has an 8ohm impedance and can put out 50W over a wide range of frequencies that are well matched to the patches I play on my wind controllers (mainly orchestral instruments). I wasn’t sure if I would need a tweeter, as the woofer range was pretty good (up to 7KHz). I decided to include one as the required enclosure volume meant that there was room for it. I used a 25mm Titanium Dome tweeter.

Amplifier

I chose this amp:

It’s a TPA3116D2 100W mono. There’s a review of it here. It gives good performance and will run on a range of voltages up to 24V. Because I added a tweeter, I included a off-the-shelf crossover set at 3800Hz:

Battery

I chose to use a Ozito 18V Li-ion drill battery. Why? Well, they offer the best storage per dollar, they recharge fast, and I have a few of them for my power tools! I decided that I didn’t want an on-board charger, as a single charge will last quite a while, and if I needed more, I can just take a spare battery.

Building the Enclosure

I decided to use a sealed enclosure, rather than a vented one. Sealed enclosures are typically smaller than vented ones, and I wasn’t after really deep notes (vented enclosures enhance the bass notes). The Dayton Audio site recommended 0.07cuft for a sealed box, which gave a f3 (the frequency where the response drops off at 3dB per octave) of 113Hz (that’s about A1 – the A just over an octave below middle C). The lowest parts I play often are the bass clarinet parts, which go down to E1 below that A, so to have the response drop off about that point wasn’t too bad.

I built the enclosure out of 12mm MDF, glued and screwed it together, and made a mesh cover for the drivers out of plastic gutter guard (!).

I 3-D printed a box for the electrics, which included a battery voltage display, the amp board, an on/off switch, the volume control (I had to un-solder the potentiometer on the amp-board to use a full-sized pot), and the audio in sockets. I also included a 5V adapter to run my Line6 wireless audio receiver.

I also 3-D printed a connector for the Ozito battery, and bolted it to the side of the enclosure.

Photos

The front view
The back view showing the electric enclosure and the battery connector
It can stand on its end
The Line6 receiver attached with Velcro

Results

I’m pretty happy with the sound – the speaker is well matched to the frequency ranges I use. It doesn’t have the deep bass that I get with my LG FH2 speaker, but that is three times the size and it’s vented. Nevertheless, the bass performance is still quite acceptable. The unit is not super light – it’s 4.6Kg with the battery and Line6 receiver attached, but it is easily carried. The volume is more than I need, and is easily louder than the equivalent orchestral instruments. I can get ~106dBA at 1m. The batteries re-charge in 20 minutes. I don’t know about battery life yet, but my calculations say it will be 4+ hours, and with the ability to take a spare battery for quick changes, battery life is not an issue.