Legacy Audio Xtreme XD Subwoofer Review

A word about amplification

I’m not totally sold on Class D amplification. I was able to review and test several Class D designs and none of them was superior to the better Class A/B or Class A amps. The group’s strong point was macrodynamics, but I found better clarity, richness and microdynamics from more traditional designs. I admit that in the past two or three years some new hybrids and updates have surfaced, so I plan on revisiting Class D soon.

Having said that, when I discussed the design of my concept speaker, the Whisper DSW, I was firm about it having no onboard amplification. I have heard how significantly the amp influences not just macrodynamics but tonality. I wanted complete control over the three sets of driver inputs, bass, midrange and treble. Do I believe amplifier choice influences the sonics of a subwoofer beyond dynamics? Yes, I do. Do I believe that if one could put a Class A/B amp into a subwoofer assembly it could sound superior? Absolutely, but that it is far from a guarantee. The Vandersteen subs used a “plate amp,” not Class D, but they had their own particular sonic weaknesses.

If a large subwoofer is going to use Class D, it had better be way big on power, which is precisely what Legacy has done. I recall using Jeff Rowland’s MC-606 Multichannel Amp sporting 1,000wpc with each of its Class D channels. I still remember the absolute tungsten grip the amp had on the bass drivers of the Focus SE. Transients were shotgun quick and brutally forceful. The XTREME XD sports the same 1,000wpc spec which is for me a powerful inducement to let the Class D thing ride. Honestly, with the previous Class D amps, I concluded I would not accept their performance holistically long term. But when only 150Hz and below is Class D, I can make it work. You would need to have heard LF bass with both types of amplification to make a big deal of it. Most purchasers of the XTREME when hearing it will likely conclude, “What was Schroeder talking about? This is glorious!” I am quite sure that if you haven’t had opportunity to compare the two methods, you won’t be pining for one over the other.

Why, then, tolerate Class D in a subwoofer? Simply because demands for practicality often overshadow the Nth degree of improvement in performance. I know, I know, I said overkill. If I had endless bucks to play with to get two massive outboard amps, and four extra outlets in my room having an additional five feet of width and 8 feet of length as well as additional cabling, I would encourage Legacy Audio to make a version of the XTREME XD with outboard amplification. That would be completely overkill-worthy. I will not speak for Legacy Audio, but they have done designer speakers for customers, including subwoofers, so I think the odds would be good that they might set up such a subwoofer system for an insistent customer.

Touching base on the bass, I very much enjoy synthesized and electric bass. If you are putting in subs, you may as well obtain one which can do justice to the musical expression of the low end, or shall I say XTREME LF? Unless you are stuck in the backwaters of contemporary music, you will be encountering a lot of supplementary LF bass. Anyone who wants to experience the music as the artist and engineer intended will need to have serious subs. It matters not whether I play Jonathan Butler’s mournful love songs, Peter White’s spacey Smooth Jazz, speaker-bustin’ Bass Addiction or a titanic sound track like the one from the movie Titanic, you need a serious LF generator.

Listening impressions

I will share more impressions of the XTREME XD with the Whisper DSW “Clarity Edition” speakers when I write up my Super-Review System article, but for now I will share my explorations of it with the Kingsound King III ESL and the Daedalus Audio Ulysses, the latter of which are recently published. The King IIII article will follow soon, as it is so thoroughly inspiring and a worthy predecessor to its forerunner that it will not be difficult to expound upon its virtues.

The Ulysses is a fine example of a well-crafted classic dynamic speaker, and it showcases not just good electronics but superb craftsmanship of cabinetry. It is a less powerful speaker than the Whisper and not quite as nuanced on the top end, as the new Legacy Air Motion driver set, with which my Whisper DSW was outfitted, outclasses dynamic mids and tweeters entirely. It is, however, a wonderful expression of traditional higher efficiency floor standing speaker design. I spent time with the superbly integrated supplementary BOW (Bass Optimization Woofer) modules containing a 12” paper cone woofer in a sealed cabinet for Left and Right channels. This is not really a true subwoofer, but rather an actively crossed dedicated woofer; it was not designed to be used with other speaker systems. Consequently, the integration of the BOW with the Ulysses was exquisite, absolutely seamless. Could the XTREME XD settle in with the Ulysses as perfectly?

The short answer is, no, it did not, nor should it be expected to. Consider that from the crossover to the speakers everything was tuned to help the BOW excel. I, however, was not intent on purchasing the BOW, as my goal is to have a subwoofer which can integrate well with any speaker system, not just one. I ran the XTREME XD with the Ulysses with great effectiveness, though I only had a couple weeks to dial it in. I have no doubt that with more time I would have discovered a setting which would have gone far in erasing the BOW’s superior coherence.

The things the XTREME XD did superbly that the BOW will never do, is an utter sense of ease in deep bass territory. While the BOW made the Ulysses sound more solid, the XTREME XD made it sound far larger. The base of power grew much greater when the Legacy subs were in use. They also were plenty quick, and at no time did I sense a lag due to their size. I especially preferred female vocals with the Ulysses and XTREME XD as Carly Simon, Joan Baez, and Tanita Tikaram among others carried more chestiness and less throatiness. The extra low frequency energy provided by the XTREME XD helped the Ulysses remain grounded and easy on the ears even when powered by solid state electronics.

The Kingsound King II, a gratuitously capable panel, presented a challenge for these huge 15” drivers. ESL speakers are quick, but the King II is noticeably faster – yes, even faster than “regular” ESLs. The low end is blisteringly fast with no overhang. The speed of the bass response is so quick it sounds strange at first, until you realize that it is far cleaner while still hitting the same notes that sounded bloated by comparison through dynamic drivers. I wouldn’t dream of trying a Vandersteen with them; it would be an exercise in futility. But the 1,000 Watts of Class D pushing the Legacy with its rapid transients caused it to keep up – barely. I had to dial it back to run below 50Hz, because anything higher would begin to obscure the King II’s bass. This is not a criticism of the XTREME XD sub, as any decent sub would make an absolute mess of the bottom end. It takes an overkill sub to even make it past the starting line with the King III.

One of the overkill features of the XTREME XD is the “Dynamic Braking System” which keeps the sub’s driver in check. As explained by Bill, “The XTREME XD employs a second voice-coil which utilizes shorted back EMF into an optimized circuit… back EMF generated by the driver reactance can peak as high as 50 volts, thus bucking the desired current input to the woofer. Legacy discovered in 1989 that this reactive voltage can actually be harnessed to greatly improve transient behavior, making the cone position correlate better to the input signal. The driver exhibits much less overshoot, resulting in a quicker decay with reduced ringing.” Without such a quick stop system a sub would trounce the delicate musings of the King III like a bully stomping a flower garden!

My instinct was to take the crossover point way down, as I said previously. However, I also had to feather the level to get the subs to just barely be perceived. There was no pushing the envelope here, as the moment the subs started crunching notes the delicacy of the King II’s bass was overshadowed. Once the proper settings were reached the King III, just as the Ulysses, took on an impressively massive character. That the XTREME XD could keep up is a miracle in itself, as there would be precious few subs able to handle integrating with that kind of ESL bass.

Tonally and dynamically, attention should be paid to the power cables used on the XTREME XD. Initially, with the King III the Xindak FP Gold, an old favorite, was used. Normally I use a perfectly consistent set of power cables, but when the ESLs are in operation with more complex (higher number of components) rigs, I simply do not have enough power cables. One would think that eight power cables might be enough? No; I need ten of them on occasion.

When I had rebuilt the system to introduce the King III for a first listen, I made it more streamlined and actually had two Clarity Cable Vortex power cords in the back of the room. After some days of hearing the King III solo, I introduced the XTREME XD subs. Yet there was something missing, a degree of richness missing in the bottom end. Then I noticed the cables and rushed to insert the Clarity Vortex. As expected, the problem was resolved and warmed up enough to further improve the Class D internal amplification.