OK, so here goes……
I have been planning something like this ever since Troels published this design. I knew that it would be quite an effort to better what I built last time and cost considerably more, but I just couldn’t resist the size of those bass drivers!
I posted some of the following on DIYaudio as a homage to Lynn Olson’s “Beyond the Ariel” thread for the inspiration that it gave me, and I’ll repeat some of it here so you get the picture and where I’m coming from.
My current speakers were built in 2018 (30mm B/BB birch ply heavily braced and damped 230 litre cabs with Faital 15PR400 and HF146 HF drivers, crossover 3rd Order electrical at ~800Hz) which originally had JMLC425 horns. They are similar to the design that was discussed on that thread some time ago (15” Bass/Mid PA driver and 1.4” exit CD) with the GPA/Altec and Radian drivers, but with European drivers that are more easily obtainable in the UK and not to mention considerably cheaper. I played it safe with the choice of drivers, took some tips from others by trawling the various forums, got traces of measurements from multiple sources and simulated extensively before I took the plunge. When the cabinets were built, I took my own acoustic measurements and used VituixCAD to model the crossover. All the usual stuff.
They were a revelation to my ears, and I found them preferable to the Tannoy Windsors they replaced which sounded too overly refined and polite (being polite here - that old Linn advert comes to mind LOL). Both of us also prefer them to my previous Lowther based speakers and conventional cone/fabric dome hi-fi floorstanders.
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However, since then both of us in the household have found that we still get listening fatigue, and whilst the sound is brilliant, it is just a bit too much excitement. They do all of the music we like excellently (Mark Knopfler, Norah Jones, Tracy Chapman, Pentangle, Roger Waters, First Aid Kit, Carcass (!) etc, they are detailed, they have that big sound that we like, they work well with films/games/DAW/TV etc as well as music, and they are absolutely mesmerising with Nightwish (Floor Jansen is a Goddess!). So there is much that is good about them, and we will never go back to the conventional HiFi stuff. But it’s just this one main issue.
I’ve experimented with equalisation with the convolution filter in HQ Player etc, messing with the crossover and remeasuring (I have measuring microphones, ARTA, REW, even a specially made measuring trolley with a boom arm jig that I machined that can do angles (polars), that I can put the speakers on to take them outside and measure if needed) to get a fix on what’s going on, but whatever I try, I can’t seem to shake it. I point the finger squarely at the CD (the Faital HF146). I could change it, but I feel as though the compression driver is crossing too low. Not that it can’t technically do it, or I’m pushing the envelope. Using this sort of CD (1.4” exit) down to 800Hz at domestic listening levels (especially a UK living room) is not exactly pushing it. It might be fashionable (in some circles) to go as low as you can in these setups, but I have concluded I just don’t like it. Having experimented with other CDs, I’ve heard the same thing when going low (below 1.5kHz). Joseph Crowe does an excellent video on YouTube, demonstrating this with one of his projects and I can hear exactly the same thing there. On the forums, there are quite a few people who say the same thing about similar designs with compression drivers in general. I suppose it comes down to personal taste in the end.
I pretty much know we are on the right track with the PA drivers for HiFi type thing, mostly direct radiator (we don’t have space for big front loaded horns and they are just too ugly and imposing – we do have some limits), but I suppose we need that extra refinement. I did design the current speakers with an option in mind for putting an 8” midrange driver like a BC 8PE21 or something similar (TG has one with the 18 Sound 8NMB420). But when I tried to simulate in VituixCAD, it just didn’t seem to gel and get a suitable enough result (impedance, sensitivity) to go with the 2A3SE which we both adore.
Plus, I like those huge 18” bass drivers!
So here’s my plan. TG’s “The Loudspeaker”. Are they too big for the room? Maybe…….
That’s part of the fun!I admire Troels and I greatly respect his designs. Whilst his designs are a package, like IPL Acoustics used to do, there are couple of things that I have to do differently for practical and financial reasons. Taking one of his designs and modifying it is a lot safer than having to buy a load of drive units for a 4 way project, building test boxes, voice everything into something coherent by mix and match and still run the risk of getting into an almighty pickle. That sort of activity is way beyond my means at the moment, and frankly, I’d rather not get that involved at this time either. If it’s good enough for him to have built a second pair of them for use as his reference speakers with his experience, that says enough for me.
TBC
Following the inevitable fallout, I ordered some plastic calipers. Sensing an opportunity out of this catastrophe, I ordered some 10.5um domestic aluminium baking foil on Ebay and subsequently changed the diaphragm (the standard is a 15um composite which looks like aluminium/kapton film which I weighed on an analytical balance at 0.0235g - the new 10.5um one is 0.0210g). This gave it a bit of a lift in sensitivity above 9kHz when measured but exacerbated the variations in response lower down. They will be crossed over at about 8.5 – 9kHz, 3rd order electrical, so that doesn’t really matter. The CSD waterfall plot also checked out ok. I tested the other ribbon, which was still in it’s box untouched, and discovered it had no output, so I returned that one to Caroline at Willy’s HiFi to be replaced, which they did promptly.
Impressively big. And that must be a small fortune of birch ply.
