Infinity Beta Series Speakers: 50 Towers, C360 Center, ES250 Surrounds, and CSW-10 Subwoofer Part I February, 2005 Colin Miller


When I think of Beta and Infinity, I think IRS Beta, as in Infinity Reference Standard Beta. Those with a connection to the vintage years of Infinity, during the times of Arnie Nudell and Cary Christie, populated with EMITs, EMIMs, and L-EMIMs, along with various other iterations of different-looking, planar ribbon drivers, will remember that the ‘Beta’ version of the IRS family was a kind of little bother of the massive IRS. Compared to the IRS, the IRS Beta was a much more practical animal.

The IRS took up huge amounts of floor space with a tall line array of EMIT tweeters and EMIM midranges mounted into a curved baffle about 4 feet wide. That line array was then complemented by a tower of six 12”, servo-controlled woofers. Double that arrangement and you had a stereo pair. The last version of this setup, the IRS-V, went for about $60,000 a pair. That's money now, and back then, it was real money.

The IRS Beta was a scaled down implementation of the same idea, but with a single EMIT tweeter, single EMIM midrange driver, and a couple of L-EMIM mid-bass drivers, all mounted to operate in a dipolar fashion, each channel complemented with four servo-controlled woofers. The pair of woofer towers and upper range arrays sold for a mere $12,000.

Fast forward to the recent past, and Cary Christie’s last project with Infinity, to the best of my knowledge, was a scaled down, even more practical IRS implementation, the IRS Epsilon. The basic layout was similar to the Beta, except that all drivers were in a single cabinet, the EMIT/EMIM/L-EMIM drivers were slightly updated, and there was a single 12” servo-controlled woofer, and instead of dipolar operation, the planar ribbon drivers directed the majority of their output forward, more like a direct radiating speaker, almost, making it a much more practical speaker to place. Price on those was about $14,000 for the pair.

At one time my heart was set on the Epsilons, but due to constraints of money and living arrangements, I eventually ended up with Infinity Renaissance 90s, much like the IRS Epsilon in terms of the basic character, but with a dynamic driver for a mid-bass, and a 10” Watkins woofer instead of a servo-controlled 12” woofer. They were still nearly 4’ tall, and kicked tail while taking names, given the right kind of juice, particularly with deep, tight, sometimes astounding controlled bottom-end performance. However, compared to their heritage, they were virtually bang-for-the-buck mini-monitors at a rock bottom price of $3,600/pair.

And there it seemed that Infinity, as I had come to know it, was coming to an end. There was a sputtering of the old guard with the IRS Sigma, essentially an Epsilon with a conventional woofer and a Renaissance 90 mid-bass, but with increased rear output from the rear tweeter and thumpier, higher Q bass that seemed to me a grab at novelty for the sake of attention. At that point, Infinity started to Harmanize, and we saw Composition Preludes with Home Theater voicing start to become the company’s main focus. Now, sure, they were good products, and immediately following Composition Overture 1s were some cool little mini-monitors with powered 8” woofers, but they weren’t along the lines of what interested me originally, and I followed other options.

So, when I heard about the Infinity Beta series, I was intrigued to see where things had gone. Companies as large as Harman have the resources to pretty much do what they want, should they choose to do so. As Infinity innovation can benefit from the Harman umbrella just as easily as suffer from it, I had a personal inclination to accept an invitation to have a full 5.1 setup take temporary residence in my home. It would have been nice to have still had my Renaissance 90s for comparison, but alas I had released them to a friend to eventually land some M&K S-150P active monitors for the LCR front channels years ago. I don’t regret the course taken, but I occasionally miss those beautiful, quasi-monolithic Ren 90s.

I should admit that ever since experiencing Revel Ultima Salons, properly set up in a good room a few years ago, driven by a Meridian 800/861 front end and some Wavestream Kinetics amplifiers, I’ve had a profound respect for what a Harman company could do, given the resources and freedom to excel in the high-end market. Still, Infinity as a brand is no longer positioned for the upper end of the audio market, but rather what one might refer to as either mid-level or upper entry-level. Still, I had attended a couple of talks by Dr. Floyd Toole, who works for Harman, and who had convinced me that the majority of what defines a good loudspeaker need not require exotic drivers, extreme build quality, or otherwise esoteric measures, but could simply be accomplished by solid, grounded, well-tested design. While I certainly benefited from elaboration of details and examples of measurements showing why this was so, it also coincided with my personal experience, in that I had gradually become disillusioned with the more ‘tweak’ and elitist philosophies to which I had previously subscribed, and so perhaps it was time to check back into Infinity, not to relive the glories of the best products I remembered, but to see how they had come along in their new found direction.

Upon Arrival

The Infinity Beta series does not have the exotic techno-oriented appearance of the classic Infinity designs. Still, they do seem quite sensibly shaped, and very solidly built, and at a casual glance they certainly do have a certain cool factor to them.

The packing isn’t extraordinary. No double-boxed or crated arrangements, just Styrofoam on both ends and a little plastic to keep spilled sodas in the warehouse off the merchandise, but it worked well enough to get the speakers to me in fine condition. One of my cats quickly remedied that achievement by knocking a surround speaker off a 3 foot counter, but the construction was solid enough such that the only damage was cosmetic, a slightly bent corner and a grille with snapped posts. I look forward to getting the bill!

The cosmetics, though nice and modern, are not this speaker’s finest selling point. The surface is very obviously a vinyl laminate, and the seams are on the rough side. However, in terms of where it counts for sound, the enclosures are entirely adequate, with nice solid construction. A definite upside is that you no longer have to take out a second mortgage to own a full set of Infinity speakers, and that will please a lot of consumers.

Due primarily to panel size, the subwoofer and surround enclosures were the most inert to knuckle knocks, followed by the center channel, and then the tower speakers. I should note that while knocking on a loudspeaker enclosure is a good rough test to check out the enclosure’s damping and bracing, it’s not really any kind of accurate indication of how much the cabinet will contribute, or not, to sonic colorations (such as added harmonics, blurred transients, etc.), that would make the sound more ‘boxy’, etc.). This is because drivers mounted on the front baffle radiating sound into the loudspeaker enclosure will not energize the enclosure panels in the same way as a knuckle impact from an entirely different location. But it’s still fun to bang on the box.

The midrange drivers and tweeters for the towers, center, and surround speakers are built into what Infinity calls a "Constant Acoustic Impedance" baffle. That’s a fancy way of saying wave-guide.

In the more common approach of dealing with diffraction, if it’s dealt with at all, the tweeter gets mounted flush to the front baffle, so to minimize any edges the sound waves would ‘see’ as they rolled across the front surface of the loudspeaker. Then, to address the edges of the cabinet that could potentially cause diffraction artifacts (when a wave suddenly encounters a change in boundaries, it can essentially ‘bounce’ and radiate out from the edge of the surface, creating secondary launches from the speaker,) we might see either foam/felt to absorb the portion of the waves that could become problematic at the edges, or radius the edges of the enclosure in the hopes that the transition is more gradual and minimizes the diffraction reflection. However, while a modest radius helps, if you really want to avoid diffraction by curving the edges, those curves need to have a radius in the span of multiple inches, far more than the mass production of affordable ‘box’ speakers allows.

My Renaissance 90s addressed this by having relatively wide baffles, on the order of 18” or so, that built in a gradual curve into the grille, a piece of solid MDF with a slight curve on the end, meeting the edge trimmed by solid wood with a roughly 2” radius on each side. The really wide baffle with the gradual curve meant that most of the treble that would otherwise hit an edge wouldn’t. And, because of the relatively large radius at the edge, whatever made it that far would transition into the different acoustic impedance fairly gradually. It was a fantastic way to address the issue, though the build requirements for the enclosure were prohibitive for cost-effective mass production.

What a good wave-guide does is apply a similar approach, but instead of starting with a flat baffle, mounts the tweeter (or sometimes midrange) driver inset into the enclosure behind the plane defined by the outer boundaries of the front panel, so that the baffle is actually concave, somewhat like a horn, but less extreme. Then, that surface is shaped to provide a more gradual transition in acoustic impedance so that the baffle actually intentionally and carefully controls the wave launch.

According to Infinity, "The wave-guide is used to match the directivity of the tweeter to the directivity of the driver below it (mid in the Beta 50 and C360, woofer in the ES250). The primary benefits are controlled dispersion both on- and off-axis, improved directivity integration with the other drivers, and enhanced audible acoustic headroom. Also, regarding the CMMD technology (see three paragraphs below), the ceramic material is deep anodized (grown on) to an aluminum core and makes up 40% of the diaphragm. It is not really damping stuff or material on the aluminum cone. Both the CMMD cone and process are patented. This is something special. As you know, the goal with any driver whether it is a traditional dynamic driver or an electrostatic panel is to control unwanted flexing or bending of the diaphragm material. CMMD does this very well. They are incredibly pistonic and push the first breakup mode of the cone well beyond its operational range."

If done well, the wave-guide can minimize the diffraction artifacts that would otherwise smear time response and rough up the frequency response in the top end, as well as control dispersion to a degree, much in the way that horn-loaded drivers can avoid much side and ceiling/floor reflections by directing sound away from those boundaries from the get go. While I don’t know if this degree of wave guide would qualify as a horn, it is a bit ‘horny’ in that respect.

While skirting this subject, I would interject that while the consumer market, and even the professional market, has seen a whole bunch of honky, nasal, harsh-sounding horn-based loudspeakers, if the horn is designed well, the sound quality need not suffer for it, and may even substantially benefit not only in dynamics, but many other attributes that us audiophiles lap up. The JBL K2 S9800SE loudspeaker is a great testament to that notion. However, that is a mighty big if, as it’s a whole lot easier and probable to design an inferior horn than the other way around.

All driver diaphragms are constructed of a material that Infinity calls "Ceramic Metal Matrix Diaphragm", or CMMD. We can just say metal drivers with some damping stuff on it. A property of metal drivers most desired by those who choose to use them is their rigidity. Because of their stiffness, compared to diaphragms made of more flexible material, metal drivers can put off cone ‘breakup’ until higher frequencies, operating in a more ‘pistonic’ fashion that many consider a theoretical ideal. However, one concern with metal cones is that when they do reach their breakup range, they can ring sharply and heavily, resulting in a sharp response peak a dragging out transients at that frequency.

It is conceivable that the fancy damping material portion of these metal cones substantially reduces that problem, if not eliminates it, but I have a suspicion that the nice fat butyl surrounds on the midrange and woofer cones, themselves a highly damped material, don’t hurt the damping of the cones either, and may be even more significant than any ‘ceramic matrix.’ Even then, with such a driver, we would expect that a good crossover would prohibit any significant content beyond the driver’s optimal range, and as such avoid the brunt of the ringing issue from the start. And, when it comes to tweeters, if you can push the breakup range beyond human hearing, that’s a nice solution too!

I would again like to spin off and interject that a flexing diaphragm is not necessarily bad, so long as it doesn’t mean standing waves on the diaphragm. After all, I’ve heard some pretty decent electrostatic panels, and if their membranes didn’t flex, they simply wouldn’t work, would they? In fact, a controlled flexure of a cone speaker can actually widen a cones dispersion pattern at higher frequencies, which if you’re trying to get the most range out of the driver without ‘beaming,’ can be a really good thing, but I digress too far, again.

Go to Part II

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