Coaxial drive units Is it a path more speaker manufacturers should follow?

Technical editor Ketan Bharadia ponders the benefits of coaxial driver arrays in speakers

- 

I've just finished writing the review for Fyne Audio's new F701SP standmount speakers, which, as you will see from the review on page 72 this issue, earned five-stars. However, there is an aspect of their engineering that I think deserves greater discussion.

What Hi-Fi?s speaker testing procedure involves spending a great deal of time optimising their positioning in our 3 x 7 x 5m (hwd) listening room before any serious analysis takes place. After all, the performance of any model depends heavily on getting this aspect of the setup right.

The medium-sized Fyne Audio F701SP ended up around 80cm from the rear wall, and well away from the sides. There is nothing unusual in that. Most rivals deliver the best balance of tonality and stereo imaging when placed in a similar position.

However, during the process, we couldn't help but notice just how stable their stereo imaging and sonic character remain as we move around the room. I think the bulk of the credit for this consistency has to go to the speaker's coaxial driver array arrangement.

In Fyne Audio marketing speak it's called Isoflare.

While there are clear technical differences between Isoflare and KEF’S trademark Uni-Q system, both place the tweeter in the throat of the mid/bass unit, aligning their centres. This kind of coaxial driver arrangement works wonders for the consistency of the speaker's dispersion characteristics in all directions. It is an advantage that is easy to hear.

With conventional speakers, where the drivers are separated and spread on a front baffle, such consistency is never the case. Their tonality shifts notably as we stand up, sit down or walk around, and the soundstage tends to collapse into the closest speaker when the listener moves away from the sweet spot (in the centre). That doesn't happen with the F701SP or any of Fyne's speakers equipped with the Isoflare driver array, nor with KEF's similarly configured Uni-Q products.