RBH Sound SX-6300/R Tower Speaker Review

RBH SX-6300/R Tower Speaker Introduction

RBH Sound, based in Layton, Utah, is a manufacturer familiar to anyone who regularly visits the pages of Audioholics.com. Their products have long been a favorite with manyof Audioholics movers & shakers, including Gene, who’s main listening space fairly bristles with RBH Sound’s products. In this review we’ll be looking at the RBH Sound SX-6300/R floor standing loudspeaker. A relatively new product for RBH Sound, the SX-6300/R is a 3-way, bass-reflex system, sporting 6 (!) drivers bolted into a nicely built cabinet. The SX-6300/R is part of the new Signature SX series, which in turn, replaces the previous award-winning Signature Reference series. The "R" in the SX line designated usage of RBH Sound premiums Status drivers similar to the "Reference" designation from the Signature Reference line.  It has been a while since I’ve had a chance to look over & audition an RBH Sound product so I was curious to see what the new line was all about.

The RBH Sound Signature SX-6300/Rs arrived in two large shipping cartons. Each speaker was packed in a series of 5 styrofoam collars and covered in a cloth sock; a fairly common packing arrangement. Extracting the speakers from the cartons was quick & easy, especially for the speaker shown at the right of the left hand picture – the carton is such a wreck it’s actually held up by the Styrofoam blocks! The carton itself arrived pretty well beat up with large holes torn into it, (only) one of which is shown in the above right photo. I was pretty sure the speaker it contained would have been damaged as well, but it in fact it survived shipment unscathed, a credit to the design of the shipping carton and packing materials that protected it.  I was also told by RBH Sound that these were demo units used at various trade shows and to expect blemishes in the finish but they nevertheless appeared to be in excellent shape to me.

Let's take a tour of the new RBH SX-6300/R speakers from inside and out to see how these gems perform. 

RBH Sound SX-6300/R Tower Speakers Design Overview

    

The RBH Sound Signature SX-6300/R loudspeaker is a ported, 3-way, passive system. It features three 6.5” aluminum diaphragm woofers, two 4” midrange drivers (with phase plugs) and a 1” silk dome, liquid cooled tweeter sourced from ScanSpeak. As showing in the pictures above, all drivers are recessed (flush-mounted) into the cabinet’s faceplate and 3 of the 4 front edges are beveled, design approaches taken to help reduce the deleterious effects of HF diffraction.

The SX-6300/R is rear ported, featuring two ducts, each 3” in diameter and flared at their external end. The system is fed signal through two pairs of 5-way binding posts (located beneath the ducts on the back of the cabinet) equipping the system for both bi-amping and bi-wiring.

The SX-6300/R enclosure is constructed of ¾” MDF, with the exception of the faceplate which is 1.75” thick (very rare in all but the best speaker cabinets we've seen). The side walls are curved internally, braced and the cabinet is filled with stuffing throughout. Overall, the design employs many practices which counter structural and acoustical resonances.

The review sample provided came with the Matte Black Oak finish, the only finish currently available for the SX-6300/R. The grill cover was a tight black mesh cloth and woodframe construct that snapped into place by way of mechanical fasteners.. For all listening tests, the grill cover was removed.

The SX-6300/Rs also came with a 56-piece speaker outrigger kit that when installed provides for a wider support base than the towers themselves can provide. Substantial in construction, they don’t take more than a few minutes to install. The kit is complete and whether you have carpet, concrete or wood flooring, you’ll be good to go. Above left is a close-up of the hardware installed and at right is a photo of both towers with the outriggers installed.  The outriggers not only stabilize the speakers but they also class up their appearance as well.  

The Drivers

At the top of the driver collection (literally and figuratively) is the tweeter, which in this case is none other than the ScanSpeak D2904/950000.

It's a 1”, silk-dome, ferrofluid-cooled Danish-built driver. With a free air resonance of just over 500 Hz, a maximum mechanical excursion of ±1.5mm, and a maximum power handling capacity in the neighbourhood of 150W (as/ IEC 17.1) you have a tweeter that will play nicely – and cleanly – with the 4” midrange drivers found in the SX-6300/R. On top of all that, the D2904/950000 has a reputation for not being a driver likely to contribute to listener fatigue. In actual use it's a very easy tweeter to listen to.  In our experience we've found speakers using this tweeter to always sound nothing short of excellent but its rare for a manufacturer to use them since they are quite costly (over $130 each).

The tweeter and the two 4” midranges, arranged a la D’Appolito, as they are in upper section of the SX-6300/R’s cabinet, all sit within their own enclosure, separated from the systems trio of woofers by an internal bulkhead. At right is a view of the bulkhead as seen looking down through the opening normally occupied by the lower of the two midranges, seen above, left. Separating the drivers as was done here neatly solves a number of sound-muddying problems. As well, bolting the midranges in what amounts to a totally enclosed box provides for a natural 12 dB/Oct LF rolloff which a designer might, in some cases, make use of when working up a crossover network design.

The midrange drivers are similar in a number of ways to the woofers in construction with the exception of the phase plug, which in addition to smoothing out the HF response of the driver serves a dual purpose as an effective heat sink.

The low end is handled in the SX-6300/R by a trio of 6.5” aluminium diaphragm woofers bolted into each cabinet. The aluminium diaphragm of each trio is terminated by a half-roll butyl surround. The magnet structure is vented. Each trio of drivers share a pair of 3” diameter ducts which are bolted into the back of the cabinet. Electrically and acoustically, the drivers are paralleled.   It was quite obvious to me by now that RBH Sound employed some excellent, costly drive units in this speaker system.

The Crossover

The crossover for the SX-6300/R is affixed to the underside of the cabinet’s lower crossbrace, which in turn is located just above the lowest of the system’s woofers. The board itself is positioned component side down. The photo at right was taken by removing the speaker terminal and pointing the camera upward into the interior of the cabinet.

The crossover features a mixed bag of inductors, resistors and capacitors.

According to the manufacturer’s specs the crossover points are 100Hz (LF/MF) and 2.7kHz (MF/HF). Crossover slopes are 24dB/Oct.  The larger metal core inductors showing are likely a consequence of crossing over the woofer array which, with 3 drivers electrically paralleled, can present some pretty low impedance values.

The Backside

The SX-6300/R is rear ported almost directly behind the top and center woofers, with the exterior port only flared.  The 5-way binding posts are gold plated and recessed into the plastic terminal cup. Pretty straightforward. The top connectors feed the midrange/tweeter drivers and the bottom connectors feed the bass drivers.  The speakers come with gold plated jumpers for those not bi-wiring or bi-amping.

Front/Back View of RBH Sound SX-6300/R Tower Speaker

RBH Sound SX-6300/R Tower Speaker Listening Tests

Set-Up

As always, careful experimentation with location to determine just where the best zones for your speakers are located within your listening space is pretty much essential. These zones represent carefully chosen compromises that best support the speaker by acoustically interfering with it the least. Once the zones are located, fine tuning their location can further focus the acoustical image generated by the speakers. In this case, the SX-6300/Rs ended up being located 9’ apart, 4’ in from the back wall and 2’ in from the side wall.  They were auditioned toed in (focused at the main listening position with a laser pointer) and
with the grill covers removed.

All listening tests were conducted both with & without a subwoofer in two-channel configuration with the SX-6300/Rs set to “large” or “small” as appropriate in the A/V receiver’s (Denon AVR-3806) bass management.  Other gear used included a Toshiba HD-A35 DVD/H-DVD player, a Hafler DH-500 stereo power amplifier, a pair of custom built subs and the AVR/SX-6300/R connection was handled by some ordinary 10-ga speaker cable.

Listening Tests

CD: Dwight Yoakum – A Long Way Home
This CD is a great one for testing how well a particular system’s midrange/tweeter combination play together. On lesser systems Dwight’s voice sounds like its coming out his nose to the point its annoying if not downright funny. On the other hand, with a system like the SX-6300/Rs, the voice sits clear, warm, human and at the top of the mix – as it should. Track 4 (Yet To Succeed) is good for this, as is Track 9 (I’ll Just Take These). The acoustic guitar comes through in both tracks, solidly imaged with a sweet top end. The tracks also show off another nice aspect of the SX-6300/Rs capabilities: the seamless integration of the drivers. In some systems, there can occur moments when it almost sounds like each driver is striving to march to the beat of its own driver, each straining to head off in its own direction. In this sort of situation the resulting aural train wreck is an obviously non-musical rendition of the artist’s intention. Not so with the SX-6300/Rs! It's never obvious where the tweeter ends and the midrange begins. Overall the image presented was rock - steady stable, keeping everything clearly and cleanly placed across the soundstage. Percussion presented as clean, tight and very dynamic. Low-level detail was never lost in the mix; it was never the case where the tweeter & midranges were competing with the woofers for the listener’s attention. And when called to do so, the six 6.5” woofers could deliver a surprising visceral LF impact but only when called on to do so.

CD: Pat Metheny - Works
This is an older CD that nevertheless provides a number of tracks useful in assessing the subjective qualities of a loudspeaker’s performance. Track 2 ((Cross The) Heartland) is excellent for testing the ability of a tweeter to resolve the less than stellar extreme high end of this particular track. For the SX-6300/Rs it was a case of a tweeter being better than the source material being fed it! Listened to through a lesser system the ragged quality
of the tracks extreme high end will remain buried under the cheapo drivers sonic failings. But when played back through a tweeter the caliber of the Scan Speak D2904 and all is revealed – good or bad.

In all fairness Track 2 is a pretty dynamic track so we might be hearing a touch of tape saturation that doesn’t really show up elsewhere, especially on the quieter tracks. Speaking of which, the sheer musicalness of the quieter tracks, such as Track 3 (Travels) and Track 5 (It’s For You) is excellent for getting a sense of how well a loudspeaker can present some of the absolutely not measurable qualities, such as how well the system conveys the emotion, passion or joy of a particular track. Ironically enough, these utterly immeasurable qualities - that go far in defining the listening experience a consumer will have with a particular loudspeaker system - determine the very measureable value a consumer will place upon a system. It's this value that determines whether or not a particular system is worth the price to the consumer. The SX-6300/Rs performed like a window, allowing the listener to peer into the session that produced the track, conveying an authentic sense of the musicalness contained within it. The SX-6300/Rs have an uncanny knack for reproducing a musical passage without interpreting it, revealing all the weaknesses or strengths of the track, for better or worse. Sweet!

General Listening Tests

To put the SX-6300/Rs half dozen 6.5” woofers through their paces I got out the Crown SASS Microphone Demo CD and played back a number of well-recorded drum tracks. With the gain cranked, the drum kit in each if the tracks came through with a palpable realism that was genuinely exciting to experience. Especially outstanding was how cleanly the SX-6300/Rs rendered the transients essential to the sound of any percussion instrument along with the ability to fill the room with the chest-thumping acoustic power of the toms and kick drum. One thing for sure here – the S-6300/Rs love to soak up power, so heed RBH’s power recommendations (100 – 300W). The SX-6300/Rs handled the low end so well you could probably get away with not having a sub on hand for two-channel listening, though, as always, I recommend a sub should you use the SX-6300/Rs as part of a home theatre audio rig.

As compared with the recently reviewed Energy Veritas v6.3s, the SX-6300/Rs clearly had more bass output, which is exactly what is expected, given the SX-6300/Rs three woofers/cabinet vs. the Energy’s two. They also consumed more power, again to be expected given the addition of a 3rd woofer/cabinet. I also found that, subjectively speaking, the SX-6300/Rs were best set pointed directly at the main listening position, while the Energy’s sounded best pointed directly at the wall behind the listening position.

RBH Sound SX-6300/R Tower Speaker Measurements and Analysis

Impedance / Phase Measurements of the RBH Sound SX-6300/R Loudspeaker System

Above left are the impedance plots of the HF/MF section (red), the LF section (blue) and the entire system (black) of RBH Sound SX-6300/R review sample. Above right are the system impedance plots for
both speakers.

At the LF end of each system impedance plot we find a local minimum of just under 4Ω at 36 Hz, located between the two impedance peaks that are typical for a vented system. The frequency of this local minimum is a good indicator of the woofer/cabinet system tuning frequency.

At just under 530 Hz we find the review sample’s global impedance minimum of 3.2Ω. Based on this minimum the system can be loosely described as having a nominal impedance of 4Ω. 3.2 Ω is swinging pretty low, impedance-wise but at this 530 Hz minimum the impedance is almost purely resistive (1.2˚), so any competent solid state power amp should be able to handle the speakers impedance load. Having said that, If you enjoy listening at realistic playback levels, then heed RBH’s recommendation and power the SX-6300/Rs with an amp rated at 100W – 300W.

At right are the system impedance curves for both review samples. Presenting them in this way allows
for a quick comparison. Essentially, the closer the impedance plots match, the better. In this case, the curves closely resemble each other and indicate better quality control, system to system, and better matched performance between the speakers. The impedance moduli present no signs of any major mechanical or acoustical pathologies (e.g. panel resonances) being reflected back into the electrical domain.

    

RBH Sound SX-6300/R system amplitude response, 1m, on-axis, ~2.828 Vac (left); system amplitude response at 0˚ (Blue), 15˚ (Dark red), 30˚ (Purple), 45˚ (Gray), and 60˚ (Black) off-axis (right) normalized to the on-axis response plot. All plots 1/12 oct. smoothed for visual clarity.

Above left is the amplitude response plot of the SX-6300/R. All measurements were done outdoors. Measured sensitivity was 88 dB (averaged 300Hz – 3kHz, 2.828V/1m). On the right are dB spl amplitude response plots for the system on-axis (0˚ (on-axis); 15˚, 30˚, 45˚ & 60˚ off-axis, 200Hz – 20kHz.

The dips in response at ~ 1 & 3kHz are visually more obvious than they were sonically. The dip at 3 kHz is particularly not concerning. Why? At around 3 kHz our hearing is somewhat less sensitive to diffuse sound. Recording mics, on the other hand, are usually flat, response-wise, even when operating within a diffuse sound field. On playback there is perceived more energy in the 3kHz range than would have been the case had you been at the actual recording location. Given that (and the fact that the human auditory system is less sensitive to dips than to peaks) and all in all the sonic impression they left were minimal. The peak seen at around 115 Hz manifested itself mainly when listening to male voices, such as a radio DJ, where it would add a bit of midbass warmth to the speaker’s voice. Otherwise it didn’t seem to detract from the systems performance, even when listening to recordings of unamplified instruments (chamber music, harpsichords, etc).

    

Left: dBr comparison of both SX-3600/Rs amplitude response loudspeakers when measured 1m, on-axis, ~2.828 Vac. At right: dBr comparison of the system response with and without the grill cover.

The SX-6300/Rs had a remarkable ability to keep images within its soundstage rock solid to a degree that’s not often encountered in less than stratospherically-priced loudspeaker systems. Comparing the amplitude response of both speakers (top, left graph) offers one explanation for this particular talent. Essentially the amplitude response of one speaker was normalized to that of the other. Any differences would then show up as a value other than zero dBr. As can be seen by the plot the two systems matched very, very well. Excellent!

At right above is another dBr comparison, this time of the amplitude response of the system with and without the grill cover. If the grill cover had absolutely no effect on the system’s amplitude response, the dBr plot would be a straight as an arrow. In this case we see a great deal of variance in the 2 – 10 kHz range. Accordingly, all critical listening was done with the grill covers removed.

RBH Sound SX-6300/R Tower Speaker Recommendations

The RBH Sound SX-6300/R is system that will easily reveal any faults in the signal chain feeding it. This is not to say you’ll necessarily end up enduring an unsatisfying performance if you drive them with a less than top notch pile of gear in your equipment rack. On the contrary!  But if you’re keen on unleashing the SX-6300/Rs in all their sonic glory than the best upstream electronics your budget allows is definitely called for. It was surprising to hear the sonic differences that were apparent when trying the system with different power amps during recreational listening sessions.

The SX-6300/Rs were very easy to position in the listening space within which they were auditioned. Once the general zones of neutrality were ID’d it was just a matter minutes worth of fine-tune positioning to get them into their proper place.  As always, taking the time to correctly position your speakers in your listening space is highly recommended. If you’re going to use the SX-6300/Rs in an HT application, a subwoofer, equal in sonic strengths is recommended as well.

Conclusion

There’s not much about the RBH Sound SX-6300/R loudspeaker system not to like, though it would be nice if they were available in something more than the matte black oak finish. RBH did inform us they would be offering other finish options in the near future.  This was an easy loudspeaker system to get correctly positioned within the listening space and very effective at revealing sonic differences existing between different pieces of upstream electronics.  Their small footprint and phenomenal sound will likely score points with those audiophiles not having a whole lot of free floor space available. All in all RBH have done a fine job in creating what will no doubt be yet another successful product line. Job well done!

 RBH Sound SX-6300/R Signature SX Reference
MSRP: $3,280.00US/pair

RBH Sound
 382 Marshall Way,
Layton, Utah 84041
800.543.2205

http://www.rbhsound.com

About RBH Sound
RBH Sound’s goal is to produce the finest products in each category we manufacture. Sonic and build quality are paramount at RBH Sound. We are constantly searching for new technologies and improvements that will keep us as a industry leader. For additional information, visit  www.rbhsound.com

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
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• — Fair
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Metric	Rating
Build Quality
Appearance
Treble Extension
Treble Smoothness
Midrange Accuracy
Bass Extension
Bass Accuracy
Dynamic Range
Performance
Value