HELIOS Speaker Kit

@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 !  

@rop45 , it is not just bass! Reproducing bass requires a woofer to take long excursions. The smaller the woofer to longer the excursion. The Helios is a two way speaker with a woofer that is running higher and a tweeter running lower to get to the single cross over point. The woofer is really a mid woofer. The long Bass excursions cause Doppler distortion of everything else the woofer is reproducing. If you do not know what Doppler distortion is google it. Transferring the lowest frequencies to another driver gets rid of the distortion entirely and increases the headroom of the system. For full range and two way speakers the improvement is quite dramatic. Less so for 3 way systems. 

Have fun building them and good luck with the project.

@milostyn

In general, you are correct, but I am hoping there is MAGIC in this design that defies rational explanation!  :).  Designer has stated the distortion is so low on this speaker that he could barely measure it - like he has never seen before.  Also, that it is likely best speaker he has designed over 20+ years.  Thank you for the well wishes!

Helios in the House!  Speaker kit arrived but I was still waiting for my Baltic birch, so I decided to build "test" boxes.  Found scrap pallet with 7/8" thick plywood from Italy! 30"x75" one sheet.  Dreamed up an equilateral triangle shape for the cabinets.  Made (4) triangles, approx 24" on each side.  These are side panels for cabinets.  One of these on each cabinet has the PR centered in it.  Next, spent $38 for (2) 1"x12"x72" pine boards - paint grade - multiple pcs joined together.  Outside dimensions were true, actual thickness 11/16".  Cut the boards into (6) pcs @ 21"5/8 overall length, both ends mitered at 60 degrees, so reducing the length of the side that faces to inside of cabinet to maybe 20"?  I can't remember.  I know the volume is exactly 1.2 cu ft so that would be a way to verify everything.  Alternating butt joints allows 3 pine boards to make front baffle, back & bottom in a perfect triangle.   Chose to buy a $200 pin nailer (and glue) rather than an elaborate system of clamps, ha!  Hey! I will use it again sometime?!  So the pine boards make the triangle, the 7/8 ply is glued on each side.  The plywood then trimmed to fit, and later rounded over.  PR recessed 3/8" into the 7/8" plywood.  Tweeters recessed 3/16 (+) into the 11/16 pine front baffle.  Woofer is NOT recessed, I was thinking 7/16" recess into 11/16 was cutting out too much.  Have to screw the woofer down to SOMETHING.  Dimensions down from top of cabinet match Meniscus drawing.  My cabinet width is about 2 inches wider, but it is what it is.  Two 5/16" holes drilled for the "Big Posts" on the back.  Jasper Jig for Router was amazing.  When you have to change back and forth to several different diameters and have confidence they will be accurate, worked great.  My last cut for through hole on tweeter was not possible because my router base interfered with Jasper holes.  That could be due to me using a router with no Plunge functionality?  Finished with jigsaw.  So the moral of the story - I love my test boxes even though I understand 11/16" pine board with no bracing and no damping material is the WORST possible material to choose for a speaker baffle!!  Just remembered I did add small piece of oak 3/4x2x12 between woofer and tweeter cutouts, but not much bracing.  Next post will be sound evaluation...