Post will be updated to include more info soon. If you have questions about your Fusion-15 build feel free ask them here. Design goals and history: There were a few reasons for this redesign of the Fusion-15. The original used the SEOS-12 over the B&C 15PS76 while this proved to be a good combo there was a slight mismatch mostly visual between the waveguide and woofer. Without a flatpack for that kit it was never super popular this and Erich had priced it out wrong so he was actually loosing money with every kit sold. Then the B&C woofer was listed as discontinued on the B&C website and we worried about the availability of those woofers. The SEOS-15 was going to get made up in plastic so we decided to start fresh with that waveguide and look for a good woofer to pair with it. It was about this time that we wanted to try and keep the Fusion designs all using Eminence woofers, this was partially so that the fusion line matches but also due to the ease of availability. Eminence is not terribly far from Erich or PE and they are usually pretty good at keeping up with demand. The first choice was actually a bass guitar driver the CA154, it was a good driver with a nice frequency response that worked in the smallish enclosure (~3 cuft) that we were trying to shoot for. Downsides were that it was 4 ohm, we wanted to try and keep this design 8 ohm so that it could be easily powered by even low end AVR's without putting them into thermal shut down if they tried cranking the volume for too long. Another issue was that the woofer was too cheap, the total design cost came in right around the Fusion-12, it may have even been less. Erich sent me the 2515 to try and when I got the box I almost thought it was empty, the woofer weighs almost nothing compared to most other 15's. After running some tests I knew this was the woofer to use, frequency response was good, it worked ok in the small ported enclosure but the best part was the surprisingly low distortion. It was lower then the previous B&C and clearly better then the CA154. So the Fusion-15 v2 was born. The crossover on the v2 is much improved over the original design, the main focus was improving midrange detail and taming the somewhat aggressive top end. Overall I would say it has a much more balanced and detailed sound throughout most of the frequency range. With the larger SEOS-15 the crossover point was lowered to about 1000 Hz, with steeper slopes used on both drivers since it is pushing their safe frequency limits. My thoughts on enclosure design: The flat pack for this design which should be available soon is about 2.9cuft and with the included ports tuned to about 40hz. This is about the smallest size I would recommend for a ported enclosure with this woofer. It works well when crossing to subs at 60-80hz and with most using it like that there was no need to make a larger more expensive flat pack. However the 2515 itself can be used full range in a larger enclosure. I feel the most popular size if going with a custom enclosure would be a 4-6 cuft tower design, this would sort of look similar to the JBL M2 or their Synthesis S9900. That should be tuned around 40hz and I would recommend larger flared ports, either two or three 3" ports or a pair of 4" ports in order to keep port velocity and compression under control. A slot port could also be used. Feel free to ask enclosure size/port size&length details if you want to attempt something like that. Enclosure dampening: This is an important aspect for most designs, I recommend linings the walls with 2-3" of dampening. I used recycled denim in my enclosure when I designing this one. Be sure to leave the area around the ports open so that air can flow freely in and out of them, constricting air flow through the ports will reduce output around tuning frequency. Here is a photo of how the dampening in my enclosure looked: Here is an example crossover layout that you can use as a template, on mine I ran all the wiring on the bottom side of the board but there us no need to do that if you do not want to. The wiring and connections can simple be done on the top side where I have the connections traced out.