Raidho D-5.1

But Wait, There’s More!

Equipment report
Raidho D-5.1
Raidho D-5.1

“New and improved” components can be found everywhere in high-end audio (and everywhere everywhere else, for that matter). Generally speaking, most of them are improved—maybe not a whole lot or in every regard, but usually enough to justify contemplating an upgrade.

The new version of Raidho’s D-5 flagship, the $225k D-5.1, isn’t one of these.

Despite the modesty of that measly “.1” added to its moniker, the D-5.1 is in key ways one of the most dramatically improved speakers I’ve heard—right up there with the Magico Q1 (compared with the Magico Mini One/Two) and the MartinLogan CLX (compared to the ML CLS/CLZ). Indeed the D-5.1 is so much better—and so different—than the D-5 that its presentation will initially require some “expectation adjustment” from those of you used to the dark, distant, hard-hitting, ravishingly lovely and realistic Raidho sound.

To refresh everyone’s memory, the D-5 was the first Raidho flagship to use vapor-deposited (over ceramic) diamond/carbonite diaphragms in both the midrange and the bass—the stiffness and linearity of which were claimed to exceed that of other cones. As was the case with Raidho’s excellent, now-discontinued C-4.1, which the D-5 superseded, these midrange and bass drivers were mated with Raidho’s superb single-ended ribbon tweeter (IMO, one of the finest treble transducers in the high end) in a three-way D’Appolito array comprising four 8" woofers (two on top and two on the bottom of the D-5’s beautiful, exceptionally svelte, dual-front-ported cabinet), two 4.5" midranges (one above and one below the central ribbon tweet), and the sealed ribbon itself in the middle of this WMTMW configuration.

Because of differences in transient speed, resolution, sensitivity, and radiation pattern, seamlessly mating a ribbon (or an electrostat) with a cone driver has always been a tough order. (Some would say impossibly tough.) But in the D-5 Raidho managed to execute it as well as anyone has, thanks in part to the lower-amplitude breakup modes of the new diamond/carbonite cones and in part to a little crossover trick that folks often play when pairing quasi-line-source drivers with point-source ones. To wit, to disguise differences in radiation pattern, speed, and resolution and to eliminate the upper midband/treble roughness of residual breakup modes, Raidho built a trough into the region where the diamond midrange crossed over to the ribbon tweet. Happily, this broad smooth dip in frequency response (which is quite measurable) fell precisely in the area where the ear is most sensitive to sounds (and therefore least affected by a lowering of volume)—the so-called “presence range” between about 1.5kHz and 8kHz. To balance out this trough and further tailor the presentation to our hearing, Raidho built a broad rise into the bottom octaves, where we are least sensitive to sounds (and most affected by volume level), producing a “designed-for-the-ear” balance that was anything but flat but which, was, nonetheless, ravishingly sweet, beautiful, and lifelike on most recordings.

However, as I pointed out in my original D-5 review, all was never completely well with Raidho’s flagship. It is one thing to claim that your speaker has a built-in frequency response that is “designed for the ear”; it is quite another to stick such a speaker in an average listening space, where room modes cause sizeable dips and peaks in speakers that measure flat, much less those that are (deliberately) engineered not to measure like a ruler.

In particular, in my room (and in other venues where I’ve heard it play) the D-5 simply had way too much bass. While the broad plateau and double-digit peak at port resonance that are built into the D-5 in the low frequencies could and did add visceral excitement and sensational impact to many recordings (such as my 15ips dub of the mastertape of Michael Jackson’s “Black or White”), they could also grotesquely distort the sound of something as simple as Norman Keenan’s standup bass on MoFi’s great reissue of Sinatra at the Sands. It all depended on where the instrument was playing and how long that tone was sustained. If, as is the case with the Sinatra recording, a bass fiddle had substantial energy around 50–60Hz, the combination of port resonance and elevated overall response would produce a peakiness so substantial it could literally make my room ring. In addition, the trough in the presence range further darkened timbre and greatly reduced immediacy, throwing vocalists and instrumentalists who should have been front and center a yard or so behind the plane of the speakers. At the same time, thanks to the bass-range plateau, drumkits, doublebasses, Fender bass, timps, and other low-pitched instruments sounded more forward than they should have. In short, when it came to staging and imaging the D-5 was anything but a “fidelity to mastertapes” kind of speaker.

As noted in my review, I did everything I could in the way of passive room treatment to fix the port problem, and while I could reduce its effect I could never eliminate it. (Synergistic Research’s Vibratron, part of its ART system, helped substantially with the presence-range issue.)

At this point you may justifiably wonder why I stuck with such a flawed speaker, much less used it as a reference. The answer is that above and below port resonance, the D-5 was so realistically powerful, well defined, and hard-hitting in the bass that I could live with the occasional aberrant G#1, A1, A#1, or B1, while the sonically attractive concomitant of the speaker’s recessed presence region was greater stage depth and image focus and less room interaction (i.e., brightness) in the upper-mids and treble.

Do not forget that the D-5 was (and is) an extraordinarily high-resolution loudspeaker with an uncanny ability to tease out little nuances of timbre, dynamic, and texture that other speakers simply don’t reproduce. When you combine that resolution with tremendous dynamic clout, unexcelled transient speed, simply gorgeous tone color, and a butter-smooth treble, you get a level of excitement, beauty, and realism on well-recorded music that becomes, in the words of my friend and colleague Andre Jennings, “addictive.”