HELIOS Speaker Kit

I forgot to mention that these are not at all efficient! Probably in the 83-85db range. I tried to power them with a 60wpc Tube Amp and that didn't go well at all! They didn't come alive until I hooked them up to my Mark Levinson 585 and now they sing. 

I just completed the Helios build this month. I went a little overboard with cabinet bracing (I went off scrip from Javad’s design but basically the same). I built basically a box within a box with 3/4" Baltic Birch inner box and bracing, and 1/2" solid wood outer box with a constrained layer damping material sandwich between the boxes. The goal was to create as inert an enclosure as possible. The results were quite good with the knuckle rap test showing the cabinet is as dead as any that I had knocked on (subjective impression) outside of a Magico (aluminum) or Alta Audio (Damp-hard, whatever that is!). I went with the highest spec components that were on offer at Meniscus which came to about $2200 and probably another $500 for the cabinet materials.

The sound after some break-in is exceptional! I have recently auditioned the new B&W 800D4 range (all of them) and I am struggling to say that the B&Ws are better! The Helios is not as bright as the B&Ws but with stronger mid-bass energy. The Beryllium dome is quite honest. If the source material is shimmery, then this tweeter will reveal that. If the source is laidback the presentation will be such. I would not go so far as to call them laidback, just true to the source material. Like any speaker then can be changed to suit by the Amplification of choice. The bass and mid-bass is the speaker strong suit especially for a standmount. They turned out to be easily good enough to replace my Dali Helicon 400s which are a quite good speaker. These speaker absolutely disappear in the room! The imaging is as good as the Magico A3s with a rocksolid center stage, with vocals placed slightly higher than I'm used to in my room and solidly behind the front wall. If imaging is your thing, you won't be disappointed! My bias is not based on the fact that I built them as I was really wanting them to not be as good as they ended up because I really wanted a commercial brand to be better, but that is not at all the case here....

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?

@rop45 Glad to hear your Helios kit is living up to the hype!! It’s always refreshing and reassuring to know that I wasn’t crazy when I fired mine up and realized they were better than some $10K commercial speaker designs I have heard recently. Keep us posted on the final build. I used either a 19” or a 21” Pangea Audio stand for mine and it definitely smooths out the tweeter response and widens the soundstage. Vocals should be centered just above the tops of the speakers which a very spooky affect that gives the impression of a singer elevated on a stage with you in the first or second row! Truly magical!

@mijostyn You are correct that the Helios crosses the woofer higher and the tweeter lower to overcome the usual challenge of a 2 way design using a larger woofer for bass extension at the expense of linearity. With that said, Jeff Bagby has managed to overcome that challenge with careful use of the PR to control woofer excursion while also adding a little to the low bass response which with my setup, the sub comes in at 40hz and is barely noticeable because the Helios digs quite deep before needing help! Jeff said he tested them to 113db and the distortion was so low that it boarded on immeasurable! That is why you use a $500 tweeter and $400 bass driver.