This is actually a very simple transmission line, Dev, and dead easy to make. The speaker resides in the middle and there are two transmission lines going to exit ports at the base of each of the narrrow sides. Each transmission line is simply defined by a single partition that reaches from the base almost to the top of the enclosure. Thus, the sound goes up the enclosure, round the partition and then down to the exit ports. Couldn't be simpler. I ended up mounting the amplifier module in a separate box, so that I could adjust it along with the volume for the rest of the gear.