Dayton TCP115-4 Woofers, ND16FA Tweeters and KAB-250 amp. I Built this over a weekend for my brother though not entirely in this form. It originally started with a pair of Eminence Alpha-4's for the woofers as I had them on hand. Those woofers ended up being too sensitive for the tweeters to give a balanced sound up even with a high Q highpass adding some boost to the tweeter level. The Alpha-4's also had almost no real bass extension so the sound was quite dull and midrange weighted I felt it was lacking any real life. So I went looking for another woofer to use and it just so happened the TCP115's had an identical frame diameter, modeled well in the enclosure volume and were 4 ohm so they were the clear choice. I must say they worked out really well, have full sound and great bass for their size and matched up to the ND16's nicely. The crossover is around 2500hz which might seem a little low for the ND16FA but it seems to handle it just fine for the volume levels this can reach with the 50w/ch amp. Electrically the high-pass knee is at 4000hz so I am not worried about cooking the tweeters. Simple 2nd order filters on each driver, 6 parts total (per side). The enclosure measures 12" x 8" x 8", around 0.2cuft, tuned to ~60hz using the 1-7/8" flared port that parts express sells. I built the box from a couple edge glued poplar boards I had handy and finished it with two coats of tung oil. -BOM- This doesn't include random build materials for the box or hardware/wire/damping etc. Also no power supply or the battery board/batteries (which is optional though I used one here). -Measured on axis frequency response- Measurement is gated so the bass looks like it rolls off early. I chose to leave the slight rise in the top end to give a flatter power response as I know the listener won't always be directly on axis like a conventional pair of speakers. It works well as the sound is well balanced and detailed when off axis but doesn't sound too bright directly on axis either. Overall really happy with this one, nice size, impressive bass response and can pump out decent volume for it's size.