Raidho (pronounced "Ride-o") Acoustics is one of Denmark's foremost high-end loudspeaker-makers. In its facility at Pandrup near the west coast of the Jutland peninsula, it fabricates and assembles all of its own drivers. The only items not fashioned on-site are the beautifully finished lacquered cabinets, which are built to Raidho’s order in China.
The company is jointly owned by its brilliant chief engineer Michael Borresen, co-designer and sales manager Lars Kristensen (also associated with the Nordost Corporation, whose top-line wire, Odin Reference Supreme, harnesses up Raidho C Series loudspeakers), and the Dantax Group led by John Jensen (once owner of the Danish driver-manufacturing company Scan-Speak).
According to Borresen, there are great advantages to having the financial resources of a company like Dantax at his disposal (and having its joint manufacturing facilities on-site). Chiefly, It has allowed him to go wherever his imagination takes him when it comes to driver/loudspeaker experimentation and design. If he can dream it up, he has been able to make a prototype and actually listen to it. "Never underestimate the importance of play" is one of Michael's mottos.
Borresen's imagination has already led him to the invention of several unique parts (made at the Raidho facility): a quasi-ribbon tweeter with incredibly low distortion, high resolution, and broad bandwidth and power-handling; several sizes of aluminum-ceramic-oxide/aluminum/aluminum-ceramic-oxide sandwich-cone drivers (used as midranges, mid/basses, and woofers in various Raidho speakers); and a brilliantly engineered neodymium magnetic drive system, called Ceramix, in which super-powerful neo-magnets are arranged vertically in a push-pull configuration around an ingenious dual voice-coil.
“People tend to look at a cone with a massive, conventional neo-magnet,” Borresen said vis-à-vis his Ceramix magnet driver, “and think, ‘Oh, that’s going to sound great,’ when in fact that magnet is preventing the driver from doing what it wants to do. Drivers are push-pull devices. They move forward and back, and when that backwave hits the flat face of the huge magnet attached to the basket, it is reflected back into the driver’s diaphragm, distorting its sound.
“Our vertically arranged magnets virtually eliminate the reflection of a rear faceplate, greatly reducing this distortion. Plus their push-pull configuration and dual voice-coil distribute flux more evenly around the entire diaphragm. That is why our drivers do not sound compressed or nonlinear, although linearity itself is a complex subject.
"For instance, people assume that if a speaker measures flat at a certain SPL it sounds linear at all SPLs—and that if SPL measurements look flat at a given SPL it means all drivers with those measurements sound the same. But this isn’t the case. The frequency content of an FR plot is simply the sum of its contents, not the contents themselves.”
To prove his point, Michael took me to a test bench in Raidho's Pandrup facility where five midrange drivers made of different materials from paper to polypropelene to carbon were arrayed. He then played back a test sweep through each one while measuring its response on an FR analyzer via a precision microphone. In almost every case the averaged FR curve looked flat in the driver’s passband, and yet the sound that each driver produced was audibly different. One had a slight “whizz” to it; one a throaty gargle; another a silvery brightness; another a dull hollowness. Looking more closely at the FR plots, you could see that the little harmonic peaks and valleys that are flattened down when sixth-octave averaging is applied were, in fact, markedly affecting the character of the sound. “Each frequency,” Borresen said, “contains a multiplicity of parts, and it is the parts that form what we hear and what we understand. We’ve spent six years here at Raidho researching which designs have the least-audible signature, the highest fidelity to all the parts that make up a note."
The proof of any audio technology, of course, is in the listening, and on this score Raidho has an excellent track record. Its C 1.1 mini-monitor, for instance, is widely considered one of the world's highest-fidelity compact speaker. However, a two-way, no matter how excellent, isn’t as challenging to design and build as a large multiway, and it was Raidho’s new, nearly seven-foot-tall, 363-pound flagship, the $140k C 4.1 three-way, seven-driver floorstander that I’d chiefly come to Denmark to audition. To cut to the chase, judging from what I heard in Pandrup Borresen’s technological innovations and insights are just as valid “super-sized” as they are “pint-sized.” Indeed, the C 4.1 is, IMO, likely to vie for the heavyweight title of "World's Highest-Fidelity Full-Range Transducer."