Field-coil drivers are among the 'dream components' of many high-performance audio aficionados due to their more powerful motors, and the constant flux field density from their power supplies.

Second generation Audio Note (UK) field-coil drivers.

This allows field-coil drivers to track an audio signal with more accuracy and precision, which provides big benefits in terms of dynamic response (and articulation) across the audio spectrum, improved resolution, faster response, more natural sound quality, more live-like presence, and just generally higher performance in every regard, than is possible with even the best permanent magnet drivers. 

As most of you know, back in the early days of audio when cinema R&D money was flowing into driver development, high-performance field-coil drivers were relatively common, like the Lansing 801B driver shown in the photo below.

Lansing 801B field-coil design that the 802 series drivers evolved from.

However, due to cost constraints, and the desire to decrease complexity for mass production, the higher-performing field-coil drivers finally gave way to the simpler, lower-cost, and lower-performing permanent magnet drivers.  

In enthusiast audio, where high-performance is king, and cost and complexity are secondary concerns, there is a move back towards field-coil drivers to achieve the ultimate in loudspeaker performance.

When I was visiting Audio Note (UK) back in 2019 Daniel Qvortrup showed me the prototype field-coil drivers that were under development (below) ...

Audio Note (UK) prototype field-coil drivers.

... and the cabinets they built for them (below) ...

Cabinets for the prototype Audio Note (UK) field-coil drivers.

... which eventually resulted in the prototype Audio Note (UK) field-coil loudspeakers, which you can see in Peter's home listening room in the photo below.

Prototype Audio Note (UK) field-coil loudspeakers in Peter Qvortrup's listening room.

I was quite excited about the possibility of field-coil loudspeakers, and quite a few of you expressed interest in those early prototype Audio Note (UK) field-coil loudspeakers that I mentioned a couple of years ago (HERE).

The covid pandemic and the resulting supply chain issues slowed the development of the prototype Audio Note (UK) field-coil project for a while, but they've been back at it, and now have next generation prototype Audio Note (UK) field-coil loudspeakers developed that have been wowing listeners lucky enough to hear them.

Andy Grove asked me if I'd be interested in hearing more about the latest generation of Audio Note (UK) prototype field-coil drivers as they proceed towards being available as a production item.

Of course I said, "Yes!"

Here's what Andy had to say:

"Hi Jeff,

We’ve done a lot of development work on our field-coil speakers since those early prototypes you saw in our R&D department (below). 

First generation Audio Note (UK) prototype field-coil drivers.

Early on, we built a ‘is this going to work?’ prototype of the field coil "E" using off the shelf materials, which sounds tremendous, but you can almost cook your dinner on the magnets they get so hot!

Still, it did prove the concept works, and it went some way to proving certain hypotheses we’d aired as to why and how a field-coil driver could sound better.

To be honest, it’s been a long and often frustrating journey to get where we are today, what with covid and the tragic situation in Ukraine. The cumulative effect of both has been devastating on our supply chains.  

Still, we soldiered on and have made solid progress and are close to a living, breathing production version!

As of today, I’m satisfied with the latest iteration of physics and materials, so now it’s down to fine tuning the power supplies and ensuring the finished speaker is going to be rugged enough to be shipped (given the weight of the drivers) and, of course, that they will work reliably for many years of listening. 

Latest generation of prototype Audio Note (UK) field-coil drivers.

The pictures I sent are of the latest ‘beta’ prototype F.C. woofer and tweeter.

They use the latest diaphragms and suspensions, in common with the Alnico E, but the magnets are completely new field-coil designs.

Note the iron sand castings of the magnet structure on the field-coil woofer.

Prototype field-coil woofer.

What you see of the magnet structure externally are iron sand castings, developed with a foundry in England’s “Black Country” - an area renowned for its steelworks and being one of the birthplaces of the Industrial Revolution.

These are machined and then heat treated to precipitate carbon, and lock the iron into its ferritic crystalline phase. 

Photo from the foundry.

Photo from the foundry.

Inside is a copper coil, of course, and the pole, which is inside the coil. It’s a two-part modular design, in the photos both parts are heat treated German ultra-pure iron, as is the top plate.

The modular pole design means we can swap out the business end of the pole, I call it the cap, the part which forms the inside area of the magnetic gap where the voice coil sits. So, once we’ve got the base version dialled, we’ll look at working on even more interesting versions with silver field coils and exotic material pole caps.

Prototype field-coil tweeter.

The face plate of the tweeter has to be much larger due to the size of the magnet, as you can see. At present we are using the same basket as the standard E bass unit, we need to make tests with an additional strengthening ring and, if that doesn’t work, we’ll design a new chassis. 

Prototype field-coil tweeter.

In the pics the face plate is polished stainless and the basket chrome. I chose those as they stand out and mark these as different from the regular drivers.

In production we'll offer those finishes and more, such as Jet Chrome and Mocha Gold (from Lamberts London, a specialist metal finishing company).

Enjoy your weekend!

Andy"

Thanks, Andy, for sharing with us your progress on the Audio Note (UK) field-coil loudspeakers project! 

Wow, what a cool project!

Here's a couple of photos of the prototype Audio Note (UK) field-coil loudspeakers that were shown at the Munich HiFi show.

Prototype Audio Note (UK) field-coil loudspeakers that were shown at the Munich HiFi show.

Close-up of a prototype Audio Note (UK) field-coil loudspeaker shown at the Munich HiFi show.

As the Audio Note (UK) field-coil loudspeakers proceed to their production phase, I'll keep you posted on any new information I hear about them. Exciting times!

As always, thanks for stopping by, and may the tone be with you!