HELIOS Speaker Kit

Your cabinet thickness on most sides should yield quite an inert structure. The No-Rez is probably the best material to use for the CDL layer. I wanted to experiment with the Polyurethane because it was easily sourced at local Box stores. I applied it to the outside of the inner panels by troweling to about 1mm thickness and then securing the outer box (1/2 solid panels). Don't skimp on the internal bracing side to side as well as tying the center brace to the top and bottom panels. 

1) Vocals are really the strong suit of this speaker. They sound very much like the singer is present for both male and female. They raised the perceived level in space of the singer to a higher point in the room as if you are seated and the singer is higher than you on a stage. Almost an eerie sensation because they are there in the room with you! There really is no weakness, but they are darker (because of the warmer midrange) than my Dali Helicon's. Make sure you give plenty of break-in time before you evaluate the sound as they will improve over several weeks of use!  

2) Outer cabinet is 11Wx19Hx15D so 1.5CF I was told to not count the bracing in your calculation. 

3) I purchased Pangea DS400 20" stands. Perfect for my seating position.

Good Luck. I think you will be quite happy. What speakers do you have now?

Speakers now are Thiel CS 2_2 and Maggie LRS, which I am sure will be displaced by the Helios.  Historically, up until a month ago, I had home-built monsters that I designed along with some help from Madisound for the crossover.  Dynaudio soft dome and (2) 17cm mids per side, (1) Focal 12" woofer.  Absolutely awesome sound, only downside is approx 6 cubic feet measured to outside of cabinet, truncated pyramid shape. Taking a word from Jeff Foxworthy,  I USED TO COULD lift them a lot easier than I can now!  Memories of these is what the Helios has to compete with!  If I can get them built correctly, I think they will be up to the task, at least they will check several of the boxes.   Thank you once again.

@rop45, the Helios drivers are very good ones but even with a passive radiator that little woofer is never going to be a match for a 12" Focal driver. What I would do is build the speaker without the passive radiator (which will take redesigning the box) and cross over to  subwoofers  at about 100 Hz. 

@mijostyn 

I agree with you, but I don't have to match the bass output of the old ones.

if the Helios is better, or as good as my originals in 3 or 4 important categories, falls a bit short in the bass, but is still impressive for it's size, I will consider that a total success.  I just returned some REL subwoofers that sounded really great.  I am enjoying the open floor space.  :)

Trigger pulled !  Money is where my mouth is !  Helios kit on order !