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Product Review

RBH AC-5T Floor-Standing Tower Speakers

Part I

January, 2004

Colin Miller




System Type: Tower
Frequency Response: 50 Hz - 20 kHz ± 3 dB
Sensitivity: 87dB (2.83V @ 1 Meter)
Power Handling: 150 Watts
Drive Units: Tri 5 1/4" Polypropylene Woofer
1" Fabric Dome Tweeter
Tweeter Protection: Yes
Crossover Frequency: 200 Hz, 3500 Hz
Crossover: 12dB/Octave
Impedance: 6 Ohms
Colors: Black, Silver
Dimensions: 8"W x 39 3/4"H x 10 1/2"D
Weight: 35 Pounds (each)




I guess this would be classified as a follow-up review. Follow up means two things. One, it’s addressing a topic pretty much already covered. Secondly, it gives me a pretense to offer up a slipshod account of the topic, and keep it short. Considering I tend to have a real problem keeping it short, maybe this is a good exercise for me.

The Towers

I can start out with the obvious. The AC-5T tower is an extremely handsome figure. The soft dome tweeter and 5 ¼” polymer woofers look nice, but the finish, build, and curves are impeccable. Aside from the additional woofers on the bottom and the tower enclosure, the only difference compared to the AC-51 is that the port is on the front, as opposed to the rear port on the AC-51. I will say that the AC-5T’s tower form looks a little more majestic, complementing the tall, slim profile with a tactful rounded base. My parents longingly commented on how attractive they were, careful to imply that my other speakers were, in comparison, utilitarian and ugly. Thanks.

The AC series I had reviewed before was a heck of a setup for very little money. Four small AC-51 ‘bookshelf’ type speakers for left and right channels in the rear and front, an AC-525 center channel, and an AS-10 downward-firing subwoofer filled out a very complete, well-rounded loudspeaker system. While it is certainly possible to do better, the performance/dollar ratio was, in my opinion, exceptional. The original review set was to include the AC-5T tower speakers for the front, but that changed at the last minute.

I don’t know how it happened, but somewhere and sometime Joe Hageman, who represents RBH’s PR firm, convinced me that a ‘follow up’ review with the towers might be a good idea. After receiving the review samples, it popped into my mind that even my overly verbose habits might not be up to task when it came to providing any kind of useful comment. After all, the AC-5T towers are pretty much the AC-51 ‘bookshelf’ speakers with a taller cabinet and a couple extra woofers, meaning pretty much the same voicing, dispersion characteristics, and general character of sound. In this case, that’s a very good thing, particularly if you intended to integrate a pair of these towers into a 5.1 or 7.1 setup, but it doesn’t leave room for a whole lot of additional comment. However will I make myself sound like an expert without a whole bunch to say?

Sure, the towers will give you more bass extension and potentially greater power handling if used in a full-range capacity, but who in their right mind uses loudspeakers in a full-range capacity anymore when they’ve likely got, or should have, a very good subwoofer?

I then remembered, me.

Prior to signing onto the sub/sat philosophy, I had owned several full-range loudspeaker systems, used primarily for two-channel music listening, but also adapted into my system for movies, both with Pro Logic and 5.1 playback. As much as sub/sat systems make a lot of sense for multi-channel, and even two-channel playback designed from the ground up, the ‘full-range’ pair of loudspeakers are often a staple ingredient in many audio systems. In my case, the last iteration of towers were really good, in terms of quality of deep bass, and while a good subwoofer would handle bass better, the reason I converted to sub/sat was because Infinity didn’t make a matching center channel for the Renaissance line, or for that matter any of the very similar IRS products, which are of exclusively two-channel stereo heritage. Also, I didn’t have the time to make one out of the replacement driver/crossover components I had acquired. Prior to my M&K S-150, and later my S-150P setups, I opted to do without a center channel rather than use the closest alternative, the Kappa Video Center.

The antique system I assembled for my parents had quasi full-range speakers as well, without a subwoofer, and even with archaic Pro Logic decoding could whip the pants off of any ‘Home Theater In a Box’ solution, or high-priced acousticube/bass module (wannabe sub) systems.

The truth is, although a subwoofer/satellite approach is probably the most cost-effective and practical way to get high-performance sound for the dollar spent, if the budget doesn’t include a line item for a really competent/fantastic subwoofer, the reality is that you’re better off without one. Poor subwoofers, whether expensive or cheap, call attention to themselves and their boom, detracting from both the musical and cinematic experience. They may provide more bass, but not better bass, and while having a sub is a nice novelty in itself for the short term, a subwoofer below par
becomes more of an irritation than an asset as time goes on.

Following that line of thinking, an economical pair of ‘tower’ loudspeakers began to make more sense, particularly for those building a system on a budget. Start with a pair of towers to get most of your foot in the door to outstanding sound quality, and then add center/surround/subwoofer as finances/fiancée allow. The sensible task to pursue, then, was how well these speakers worked by themselves, and whether they were a viable solution for discriminating listeners who required the whole package in a single pair.

I’m happy to say, they did quite well.

The Listening

Piano, even when not using the lowest notes, is a very demanding instrument. While listening to Arthur Rubinstein playing Polonaises No.4, Op40, No.2 in C minor, I got a pretty good feel for the speaker’s range and balance.

On the side, while I’m not really supposed to get measurement insight prior to the listening evaluation, I did get a peek at JJ’s quasi-anechoic measurements before the wedding. In fact, I witnessed JJ repeating the process for my benefit. If one were to look exclusively at the on-axis quasi-anechoic frequency response, you’d think that these speakers would sound a bit bright, with a tilted up slant towards the top-end of the spectrum. Having seen this before I actually listened to the speakers, it might be tempting to save face and suggest that my listening coincided with that version of reality (because of course my hearing is indeed that darn good) and that the speakers were overall a little bright-sounding. Well, that wasn’t my experience. On the surface, these conflicts might imply either that I have broad high-frequency hearing loss, I have a bias towards thinking that bright is neutral, or that the measurements are bogus. I don’t subscribe to any of that. So, how can I consolidate my belief in the validity of measurements and my own listening experience?

A single quasi-anechoic frequency response measurement can give us a very good idea about the on-axis frequency response of a loudspeaker. However, while a single on-axis measurement may tell us quite a bit about any really nasty peaks or dips originating from driver/crossover/baffle problems, a single measurement cannot tell us much about the total power response of the loudspeaker, one of the best indicators of a loudspeaker’s overall tonality in a listening room. With direct-radiating type loudspeakers, such as these, where the majority of the sound is directed forward, even if the dispersion is extremely smooth, wide, and even, eventually there comes a point where the higher frequencies become directional, radiating exclusively forward, if not pretty much straight ahead, and the lower frequencies do not.

That means with a direct-radiating speaker, if the power response is actually balanced, the on-axis anechoic (or quasi-anechoic) response will be tilted to look bright. Were we to listen to these loudspeakers with a well-balanced power response without the benefit of a room boundary, for instance, in a parking lot, they may indeed sound bright. However, put into a real room, it might work out just right, and in fact probably much better than a similar design balanced in reference to only the direct, on-axis response, which in comparison would be ridiculously bass heavy unless in the middle of a very large room with lots of bass absorption. And so, with the qualification that I was not listening in a very immense room, albeit on the large side, I stand by my assessment, and JJ’s measurements as well.

But back to Rubinstein. The Piano’s wide range and dynamic content are a terrific test for listening to full-range reproduction. The typical go to test is often synthetic explosions, pedal notes on obscure organ fugues, or what not. The piano, being a physically immense and resonant instrument, creates low-frequency ambient content just by virtue of mechanical operation inside a large resonant cavity. Some of the most ridiculous bass I’ve heard in recorded music has been when Tori Amos pumps her piano pedals during her more intimate single recordings. Because of the way the microphones were placed, some of the tracks have low bass so exaggerated that it makes the room shudder, not that these AC towers were ever going to make the room shudder, but you get my point. Low frequency content not only pertains to music, but the sense of spaciousness in which that music was created. Piano is a very spacious instrument, by virtue of sheer dimensions, and so I shall proceed with feeling justified.

Rubinstein’s piano sounded very natural overall - by far the most critical element in sound reproduction. If the speakers are voiced so as to add commentary for the sake of excitement and interest, they often call attention to the sound reproduction, not the content. It’s a great way to make your products stand out for customers in a chain store who often have yet to decide what they really want in a loudspeaker, let alone have a vague idea what they’re listening for. It’s also a great way to get that customer to buy a different loudspeaker a few years down the road. Good economics, arguably a successful business model, not a good loudspeaker, questionable ethics. Perhaps I should stress that this did not apply in this instance. The AC-5T towers seemed neither overly emphasized nor withdrawn in overall presentation, a feature that makes for a great long-term relationship.

I might have liked a little more openness on the very top end, though I wouldn’t trade the smoothness in that range to accomplish it, a common swap many designs make while cheating their way to the perception of high-frequency extension, using treble drivers with a peaky response at the very limits, most often of the cheap metal-dome variety, and sometimes of the expensive metal-dome variety. Don’t get me wrong, you can get a smooth-sounding metal dome tweeter, but the less natural-sounding variety are often deliberately selected for their coloration. On the other hand, you can also get an atrocious-sounding soft dome or ribbon tweeter, showing that no design method has a monopoly on sonic deviance. But I digress.

The very bottom region of the AC-5T Towers’ bass reproduction wasn’t capable of the infrasonic expansiveness that conveys much of the size of large instruments, or even the very limits of the audible range, nor did it ever threaten to pump the room in any manner appropriate for a rave party. On the other hand, it was suitably full-sounding, without booming or otherwise coming across as congested, chesty, or over-dramatically kicking its way around. And, the limits in extension that caused the AC-5T tower to fall short of the awesome experience that is true full-range reproduction weren’t obvious. If you knew what to listen for at the very bottom octave and below, these speakers wouldn’t pull the wool over your eyes with any kind of parlor tricks, but I never thought to myself that the bass performance was ever any kind of impediment. As I don’t tend to like the bass quality of many speakers designed to obtain bass extension by use of a port, this is saying something substantial about the abilities of RBH’s engineering team.

I popped over to Stan Getz and Kenny Barron with "Stablemates", offering not only piano but also saxophone to taste. I noticed that with Getz’s saxophone, the AC towers did have a hint of emphasis in the upper midrange, but that emphasis seemed marginal, if not downright subtle, and for speakers in this price range, entirely acceptable. While, like their smaller cousins, the AC-5T towers didn’t have quite the level of refinement in the middle of the spectrum as far more expensive, ‘reference caliber’ loudspeakers, they did quite well, and with Getz’s saxophone laid out a whole bunch of texture, imparting an almost tactile feel of the instrument.

When it comes to their application for movies, in respect to bass extension and pounding capability, the AC-5Ts aren’t going to give you anywhere near the frightening, entirely seismic sensation of an M&K MX-5000 mkII playing the bombing run in "Pearl Harbor", or for that matter match the RBH’s own AC series subwoofer at bringing the entirety of heavy machinery into the home, such as during the beginning of "Fly Away Home". However, the bass reproduction can certainly provide a bit of rumble in the gut, and limitations in reproduction aren’t blatant. For those who aren’t hard-core infrasonic connoisseurs, the bass quality and quantity might be more than they’ll ever need.

Click here to go to Part II - On the Bench and Conclusions


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