Crossover Magic for the Dual-concentric Radian drivers

Mini-review by Noam Bronstein

I first met Frank Fazzalari at last year’s TAVES show in Toronto. A few things struck me immediately. Frank was a regular guy, an audio enthusiast with a sparkle in his eye. He was very personable and approachable. His pride and joy Coherent Speakers Model 10 sounded great and looked great…the room was abuzz with people while I was there. And a glance at his business card told me he also resided in my hometown.

radian-5215BeNeo-size375 IMG_0394

Frank and I continued to talk regularly after TAVES, and I learned that he’s been modifying Radian crossovers for quite a while – and using souped-up Radian dual-concentrics in his Coherent speakers. This was interesting to me because, a few years ago, my friend Scott Fraser called me and asked if I’d make a trip with him to check out a pair of Radians that were for sale in DIY Tannoy Stuart style cabinets. We made the trek, and Scott bought the speakers…I helped him get them home. The Radian 5215b turned out to be an intermediary stop along Scott’s journey from “Lowther guy” to “Tannoy guy”.  Subsequently he’s acquired Tannoy Monitor Gold 12’s, Monitor Gold 15’s, and three additional pairs of large domestic cabinets. Since we’re best friends, I’ve been a peripheral part of this journey: along with trips to have the vintage drivers checked out, I’ve also hauled cabs from Ottawa and Windsor, and acquired the spinal pain to prove it. In one of Scott’s innumerable moments of generosity, he decided that when I brought the Belvedere cabs from Windsor, I should become long-term custodian of the Radian-Tannoys – we affectionately refer to them as the Radiannoys.

IMG_5829 rad-xo

The beasts have been here a few months now, and in April, Frank came by to rip their guts out, replacing their crossovers with his much simplified units (pic above). But I’m jumping ahead.

For those who aren’t familiar, Radian makes many drivers, primarily for the pro audio market. The range of dual-concentrics include an 8″, 10″, 12″ and 15″ model, and these are upgradeable with Beryllium diaphragm tweeters and Neodymium-magnet woofers (the stock 5215b is a $600 driver. For the 5215BeNeo? Don’t ask). And of course, the large dual-concentric design is of great interest to a healthy number of audiophiles, i.e. all those guys using vintage drivers from Tannoy, Altec-Lansing, JBL, and numerous others. Now obviously, pro drivers and domestic drivers are in some ways like apples and oranges – they belong to the family we call “fruit”, they share a shape and size, but their uses and characteristics tend to diverge like the proverbial fork in the road. Domestic audiophile speakers tend to be “scaled” for use in an average sized room, with an average sized amp, at moderate listening levels, the focus being on refinement, and so on. Pro drivers like the Radians can typically be more edgy, capable of very high SPL’s (therefore high sensitivity), and, above everything else in their design brief, they need to be dead reliable.

What does all that preamble mean? It means that Radian have traditionally supplied these drivers to the pro market with crossovers designed first and foremost to protect the voice coils. Big, high power ceramic L-pad resistors, lots of filtering and inductance. It’s the audiophile’s equivalent of throwing a big blanket over your speakers – adding phase errors and any other type of colouration you care to name. But it allows Radian Audio’s people to sleep at night and still warranty their drivers against 500 Watts RMS. Max SPL of 130dB for these Dual-concentrics, you say? Yep, and that means you’re more likely to fry your Bryston 4B than burn up a Radian voice coil.

Long story short, as this is intended to be a mini-review (the first of several installments). People in the know (like Frank) have seen that the Radian drivers could be capable of superb fidelity, with the right approach. In the near future I hope to review Coherent’s Model 15 – having heard them at Frank’s place (driven by a 300B SET), I can assure the reader, they are outstanding transducers. For now though: if you own the Radian drivers, or know someone who does, I highly recommend giving Frank a call. His replacement crossovers, even the basic level 312 mod I have currently, completely transform the 5215B’s. It’s like night and day. And you hear it instantly. Most immediately noticeable was the bass response – it extended by 10-15Hz as soon as we powered on. But this is a top-to-bottom improvement, no one needs golden ears to hear it. It’s not like you have to listen for specific traits to convince yourself of the change – again, the most apt analogy is that the “old” (which wasn’t bad at all) now seemed like it was covered by heavy blankets, in comparison. In the near field, with one speaker done and the other still sporting its’ original crossover, the difference between them was incredible. If I hadn’t been right there watching, I might’ve wondered if Frank swapped the drivers themselves!

And this is just the first stage of upgrading – cap swaps are coming, expect to read MUCH more about this adventure in the weeks and months to come. One of the nice features here is that Frank’s XO is solderless! Meaning part upgrades are a lot less messy and time consuming. Meanwhile I am grateful to Frank for his expertise – and his willingness to put his crossover, and his name, on the line like this. It seems like a no-brainer, but clearly a lot of hours of trial and error are behind it.

These crossovers are currently available only through Radian Audio, or directly from Frank.


Radian Audio 312 Crossover, made by Frank Fazzalari

Contact:  Tel. 1-905-518-1240   Email:


Send a Donation

If you've enjoyed this content, consider supporting Wall Of Sound with a donation. It only takes a moment and will be greatly appreciated.

Related Articles

Search Wall Of Sound

Leave a comment

Your email address will not be published.