Wow, that's it? I was expecting to see much more interest in these. The review made me think that the strange design was their strongest point since it lacked much of the expected excitement that I feel for my DIY speakers.
I noticed the tweeters have been changed on newer models and I can't say if it was based on price or a continued evolution in overall sound. Either way going from a 1st class driver like a real Heil then going to a long horn compression driver (of which I would never think is better no matter who makes it) seems to me to be based on cost and availability. I was just looking on AliBaBa site for Heil transformers and the good ones start at around $700 each! So chances are slim that these are going to use the best available and for some reason (just my gut) I can't help but think there may have been something that happened legally by using that brand name as the description of the actual driver and quite possibly just the design should have been referenced and the actual makers name if it was never disclosed.
Now I could very well be wrong but why would you do such a drastic change to the best part of that speaker. Secondly it doesn't appear that there were any other changes made but from what I've read he spent 2 years designing this model as his flagship. I can relate to that after my similar experience making my speakers but I went with electrostatic panels and crossed mine at 600Hz - 800Hz overlap with an active crossover and 2 big amps.
I haven't read up on the back horn bass system yet but I'm skeptical that a single 4" is up to the task of matching the Heil? From my own tests I concluded that I would be using nothing less than 2x 8" drivers but they would likely be of a high quality heavy duty design with a cost close to $200 each. The other option for 8" drivers was to run 4 lesser quality drivers per side in a isobaric configuration or a bipolar with 3 in front and 1 in back. So I'm with him on the need to reinforce the rear output with the Heil but not with the horn tweeter. So this is where I'm confused they took 2 years to get this design perfected, then ditched it instantly and made no changes to the design and doesn't mention that the rear output needs 3 feet off the back wall to work properly. If you have been involved with speaker design trends and read why people come up with so many contrasting thoughts on this hobby, you'll notice everyone thinks that the sound out the back will smear the overall sound (yes I know it's complete BS and can only be known when certain useless tests are used (as a way to get you to spend more money for no reason)) unless you are incoroerating a tweeter like the Heil or an open back electrostat.
Even with the complimenting design you'll hear some say that rear waves are just killing the sound, so why would a new company use that idea when right now the talk is to avoid it at all costs? I'm not agreeing with this I'm just bringing up this point to try and figure out how he transitioned to a front only radiating horn with a 60 degree dispersion but kept the rear radiation bass output that's running all the way up to 2kHz! I could see if it was crossed at 200Hz how this would not impose much of a problem, but once you pass 1kHz you need to have the tweeters rear output to fill in for a smooth transition.
If the idea is to keep the cabinet size down and still get low bass (I don't consider 42Hz as low) I can name several drivers that can outperform that design with the same dimensions in a sealed cabinet and I also know that there is a need for a bipolar bass output if you run the Heil and cross it up high. He also concluded he needed sound damping material behind the tweeter on the top of the cabinet to stop reflections but he's using the back wall to reflect the bass and tweeter anyway!
I have found 2 quality 8s one forward and one aimed backward has a much smoother output as plotted hundreds of times by myself. I also added a front firing 12" (sealed) to the mix and realized 24Hz flat up to and beyond my crossover point with overlap. The overlap is the key to perfect transition no matter what size drivers you use. Sweeps look great if the larger woofer is up higher and close to the panels.
I have not completed my cabinets yet since I'm still looking for my final woofers. I have decided to run an array of panels (14 per side) but I haven't tested if I should run them along 1 side or both sides of the woofers. I'll leave them room to move horizontally for wider dispersion with each facing a few degrees alternating for testing it might not matter but there's nothing posted officially showing anything like what I'm doing. I know for sure mine will put this to shame at any volume and will go far beyond what would ever be needed to play back realistic volumes. I can place my speakers anywhere in my room and get near perfect response. One last point, I have done some testing with 10" monitor audio drivers and made a few different designs, one used a front and rear ported cabinet that I could plug the holes and test 3 ways, front port, rear port and sealed. Even with the rear radiating panels I found little difference in overall sound and tests confirm there's little change in RTA plots. I also made one with a 113" long port that's 2.06" x 9.75" with a 1 cubic foot volume for the driver mounting area with both the driver and the port facing forward with the opening as close to the driver as possible. I had smoother results in the typically hard to calm areas around 200Hz and a slight gain at 24Hz. It wasn't enough to justify the extra work and size. I am not using those speakers now and found sealed cabinets for 12s and bipolar mounted 8s to be far superior in overall sound.
My own conclusion from my last 2 years has been very different than what he's saying but I'm also never going to have any speakers that stop at 42Hz now that I'm used to hearing easily down to 20Hz with a -6db from 24Hz running at reference.
No special treatings, no BS bass coupling double talk, no difficult placement, and for those that think the spread of the woofers makes a huge problem with transition haven't spent time testing this rumor themselves, just because someone came up with this based on 50 year old speaker design and sharp crossover slopes doesn't mean it is true when using modern woofers with overlapping crossover points. Testing, testing and more if your own testing will show how wrong most ideas can be, the rumors of such awful ideas and new terms is simply a way to get you to get the upgrade itch. Without it how could they get your cashm
Useless test programs that do nothing but destroy the sound are all the rage, you'll spend plenty before you realize that after it's done and you run a different testing program it'll tell you a completely different result, which is right! Probably neither, once you remove that DSP you'll find huge improvements instantly. Tests are good for finding approximate limits to individual drivers and for finding crossover points then finding obvious peaks but you need to run several different tests with several different mics to confirm each result, you'll find none will match exactly but you can see where a big problem might exist.
This is all my own feelings and nothing I have said here is to be taken as proving or disproving the quality of these speakers, I agree on some ideas but am suspicious of some things that have changed. I don't know the man but do live in a near by location, so meeting him might not be out of the question.
I'm not selling my speakers and I don't claim to hold any acoustic sound degrees nor use any design programs to reach my conclusions. I believe that physical testing is the only way to know for sure what the results will be. If you only make 1 cabinet design as your program tells you, how do you know for sure that it's the best or even if there's any huge difference between designs that make it worth bothering with? From my tests I found using a quality driver is the key to building any speakers, better drivers are usually more forgiving and will have less swings in resistance less limitations due to resonance, volume size tends to be less important and have better cooling (less coil issues) other benefits are off acus response but for lower tones this is not a huge problem. You can spend thousands on raw drivers and get no better sound than you can from finding used stuff that have blown tweeters or bad cabinets for pennies but this only applies to quality drivers that have tried and true real life proven to be good results. Older woofers need not be included in this formula!
