The Argos design is a compact 5" two way bookshelf using the Faital Pro 5FE120 and the Beston RT002A ribbon tweeter. This small bookshelf speaker is capable of more output then its size would suggest and exhibits excellent dispersion characteristics with a good directivity match at the crossover resulting in a wide sound stage and solid imaging. I actually purchased a pair of each driver over a year ago to start working on the design but only got around to it just recently. If there is enough interest I will consider making up some PCBs and/or CNC'd baffles for this design. Or it could possibly be turned into a kit on DIYSG. Edit: -PCBs here- Background: I'd been itching to try a ribbon design for a while and decided to go ahead and start with a simple two way bookshelf design. The only real goal for this design was was good price/performance ratio, as with most of my designs I like to stay with more value oriented drivers so that the final design is accessible to those who are on a budget. I started looking for a ribbon tweeter to use and the Beston RT002A caught my attention for it's ability to be crossed fairly low for a ribbon (2500Hz). I also liked the implementation on a shallow waveguide which I suspected would give much better control of horizontal directivity then flat surface mounted ribbons. With the tweeter selected I moved onto the woofer. I knew I wanted to stay in the 5 - 5.25" range in order to prevent too much beaming at the crossover. I've had my eye on on the Faital Pro 5FE120 for a number of years as it checks nearly all the boxes, very good sensitivity for a 5" woofer, decent xmax, high power handling, nice flat frequency response free of major cone breakup and has low inductance with a shorting ring in the motor as well. The only downside is it's bass extension is somewhat limited, a trade off of it's high sensitivity and ability the be used in compact enclosures. So no deep bass extension from this driver. The result: A speaker very impressive for it's size. The high power handling and xmax on the 5FE120 means you will be hard pressed to find it's limits on regular AVR power especially if crossed to a subwoofer. I find the woofer handled itself extremely well when pushed hard, I noticed no modulation of the midrange even under very bass heavy content being pushed to and perhaps a little beyond xmax. These won't wow anyone with their bass extension as it falls off below 60hz but it is enough to provide decent kick in smaller rooms with most music when used without a subwoofer. That said a subwoofer is recommended if you want full range extension. Now the RT002A doesn't have the best distortion performance I have seen from a tweeter but I don't find it too objectionable. It seems most of the harmonics are pushed up above the vocal range so this gives it a slightly grainy or sharper sound which again I don't find causes any listening fatigue the same way distortion in the vocal range does. Dynamics and transparency however are great and it seems to maintain composure better then many domes do which tend to get nasally and compress when pushed hard loosing their detail and separation. I found the sound stage to be excellent, the very wide and even off axis response helping there, imaging good as well. Overall I'd consider these to definitely be a step above my Nexus TM design in terms of output capability, dynamics and clarity while maintaining roughly the same footprint and cabinet size. Measurements: The waveguide of the RT002A shows excellent horizontal directivity control maintaining near constant directivity down the the crossover where it transitions fairly smoothly to that of the the 5FE120. Horizontal dispersion is roughly 130 degrees (+-65 degrees). I ended up with a mostly flat and even response which I found sounded best. There is slight rise at the top octave which when flattened seemed to take some of the life out of treble. This is similar to what I read others have found when using this tweeter and I suspect it has to do with that rise giving a more even overall power response since the vertical axis sees a reduction in output output in the top octaves off axis. There is a decent amount of BSC built in but it's just enough that the balance is not too dry when used free field and not to bloated when places near walls. Crossover: Since both drivers have a fairly smooth response the crossover topology is pretty straightforward, a simple 2nd order lowpass on the woofer and 3rd order highpass on the tweeter with a series resistor providing a little padding and contouring. Electrically the highpass on the RT002A is just above the 3khz range but the bump in it's frequency response on the bottom end pushes the acoustic center of the crossover down towards the 2.5khz range. This is also where I found the best phase relationship between these drivers. The actual forward lobe is pointed slightly upwards so the listening window for the flattest response is between directly on axis with the tweeter and about 10 degrees above axis, it's not a sharp cutoff above or below that window. Options: A 10uF cap can be substituted in for the 12uF, this will result in a flatter response in the 2-3k range. I did go back and forth on those parts quite a bit, the 10uF does give it a little more presence or detail in that part of the midrange but I found it to cause some music to sound more shouty. I like the more laid back open sound the 12uF value gave with a slight dip in that range. (differences are very subtle) The 12 Ohm resistor can be swapped to a 10 Ohm which will result in a slight increase in the treble range for more detail, or a 15 ohm which will result in a slight decrease in treble output. You could alternatively place a 75-80-82 ohm resistor in parallel with the 12 ohm which will equal ~10 ohms, or place a 3 ohm resistor in series with the 12ohm which will give you 15 ohms. Schematic: Xsim response + impedance: Box Design: The enclosure is 6.5" wide x 10.5" high x 8.5" deep. I used a 3/4" baffle and 1/2" for the rest. Internal volume is approximately 0.2cuft. I placed a pair of cross braces centered between the drivers going front to back and side to side. This cabinet uses the 1-7/8" x 5-5/8" flared port from parts express which results in a tuning of ~65hz. The port is placed on the back and is centered behind the tweeter. Cabinet damping should be light fill of the back half (stay behind the port) I also places some damping around the bottom half near the driver lining the walls. Cost: Drivers, crossover components and the port come in at just over $110 per speaker. I suspect a pair could be built for right around $250 including the materials and odds and ends especially if a coupon is used at parts express.