This article appeared online May 2002, AudioRevolution.com
RBH Compact Theater CT-5/CT-7BH MC Series
By Richard Elen
Utah-based RBH Sound has been around for a while: last year was their 25th anniversary. In the time they've been in business, they have produced some formidable loudspeaker systems, notably the impressive Signature Series. Now they have turned their attention to the needs of home theater listeners who have limited space, addressed with the release of the "Compact Theater" series. Though the new design is diminutive, RBH has managed to include the same design standards – and solid, durable materials, notably aluminum – that are utilized in their more up-market products. The result is a very satisfactory combination of high-quality audio and practicality that will suit the home theater and home surround audio listener who wants something way beyond your average grotty little satellite speakers (believe me, you do).
The system arrived in two boxes. One contained the MS-8.1 powered sub, a near-cube a little over a foot wide on all sides. The other carried four MM-4 mini monitors, each about seven inches tall, plus the 11-inch-long, four-inch-wide and four-and-a-half-inch-high C-4 center front unit. All the units feature solid, impressive and hefty die-cast metal enclosures, and are available in either black or white. The whole system exudes solidity and suggests that whatever it’s going to do, it will do it well. The price for the 5.1 system is $1,099; the 7.1 system is $1,349.
Installation and Operation
Installation was really easy, mainly because I already have a 5.1 system set up, so the cabling was already in place. There are two versions of the Compact Theater, incidentally, the CT-7 with six mini-monitors plus the center and the CT-5 (which I had). You can upgrade from the latter to the former by adding two more mini-monitors. The aluminum-coned MM-4 "mini-monitor" speakers and the C-4 center channel speaker have large, gold-plated screw binding posts. They are recessed in quite a small space, so it’s a little fiddly to get the cables in there, but it was not too much of a problem. The posts will take hefty cables fairly easily.
The powered sub is the most complex unit by quite a lot (with the MM-4s, you just connect the cable and you’re done). The ported enclosure includes a 200-watt amplifier driving a pair of eight-inch aluminum-coned drivers, one facing the front and the other facing down (it stands on four sturdy plastic feet that keep it a couple of inches off whatever surface it sits on). A rear panel power switch selects off/on/auto. Auto powers up the amp when a signal is sensed, after which it stays on for some time after the signal disappears, a sensible feature as most people will probably stick it out of the way in the corner. Also on the rear panel are the inputs and outputs, as there are two or more ways of driving this unit. It can be hooked up to systems which have no specific sub output by taking the front L-R pair signals either at line level or at speaker level into the sub box and then out again. For this purpose, there is a pair of RCA connectors for line-level left and right in, and another pair for out, plus four sets of binding posts for left and right high-level I/O. Three controls complete the rear panel: a level control, a phase knob, and a crossover frequency control variable between 50 and 160 Hz. In my case, I fed the line-level sub output from my receiver into the left line-level input and went on to the next thing.
The eight-ohm monitors feature a four-inch aluminum woofer and a one-inch tweeter. The center front unit includes two of the four-inch drivers (presumably parallel, as the unit has a four-ohm impedance), insuring that this channel, so important for movie dialogue (though of variable utility in a music listening situation) is taken care of properly. Remember that with mono sources, this speaker may well be handling everything above the crossover frequency on its own.
Once you have the speakers set up, you need to check that they are connected correctly, set their levels, and above all ensure that your receiver’s bass management is set up right. This is really important for anyone who does not have a room full of enormous full-range speakers. In my normal system, I have a powered sub and a pair of JBL 4311 studio monitors in the front (which I tell my system are "large") and JBL TL-series center and surrounds ("small"). In the case of the CT5.1 system, I had to tell the receiver that all the speakers were now small and that a sub had been added.
The purpose of bass management, as I so often tell people, is to make sure that any bass on any channel (not just the LFE low-frequency effects channel) is fed to any speaker that can handle it: the LFE is not the "sub-woofer" channel! In this case, the only speaker that can handle bass is the subwoofer. Get this wrong, and your system will sound thin and weedy. Get it right, and the system will spring to life.
With bass management correctly configured, I went on to test the speaker levels. For speaker testing, you can either use your receiver’s built-in test feature, if it has one, or use one of the many DVDs that include a set-up track. All of 5.1 Entertainment/Silverline’s DVD-A/V discs have one, for example. The usual format is to play pink noise out of each speaker in turn, allowing you to adjust the level of the speaker that is currently playing so that they all produce the same volume. Of course, they never do. Room position, for example, will vary the apparent level. Even perfectly matched speakers like these, for the same reason, never sound the same. So you do it by ear the best you can, unless you prefer to use a dB meter -- I have one, and I still prefer to do it by ear. It's virtually impossible to come up with a better method of setting up a sub, and you almost always need to tweak it on program material for best results.
Something you will also have in your receiver, probably, is a means of setting the crossover frequency between the sub and the rest of the system. The important thing here is to make sure that everything matches. In the case of the CT-5.1 system, we know that the mini-monitors are alleged to have a decent response down to 100 Hz. We also know that the sub’s crossover goes up to about 160 Hz.
The theory of a sub is that bass is not directional, so it doesn’t matter that you have a single source of bass end in the system. It also doesn't particularly matter where it is, because bass isn’t localized. I am not entirely happy with this conventional wisdom, but let’s assume it’s true for the time being. You therefore have two things to balance here. If you set the crossover frequency too high, you will be pulling frequencies out of the monitors into the sub that are high enough in frequency to be used in localization, so you could lose some of the directional information in a recording. Set it too low, on the other hand, and you could be giving those little monitors frequencies lower than they were meant to handle. This risks possible distortion and certainly a "hole" in the frequency range of the system between the crossover frequency and the lowest bass the monitors can reproduce at a decent level.
If you were running your front speakers through the sub, as you can with this system, it would be a bit less complicated, because you could feed full range to the front left and right speakers (tell your receiver’s bass management that there is no sub but that the front speakers are large, which should make all the bass come out of the front left and right channels) and then tweak the crossover knob on the sub until you get a smooth response. In my case, where I was using the sub simply as a sub, fed with a line level input from the receiver’s sub output, I had to be more careful, so I decided to set the powered sub’s crossover to its highest frequency, 160 Hz. This ensured it would get anything sent from the receiver. I then used the receiver’s crossover setting to choose the frequency at which bass signals would cross over from the monitors to the sub. My guess was that the best frequency would be somewhere between the highest frequency of which the sub was capable (let’s say 160 Hz or so at this setting) and the lowest frequency the monitors could handle (say 100 Hz or higher). So I went for 120 Hz initially, and messed with it later.
Music and Movies
The next thing to do was to play something and have a listen. I started with Alan Parsons’ DTS CD On-Air, because it includes a gorgeous instrumental with a hefty bass end on "Cloudbreak" that would be good for setting up the sub level. Well it certainly did that: the bottom end on the track came through loud and clear and easily enabled me to get a better setting for the sub level. There was a fine punch to kick-drum beats and a full and rounded bass sound. I also noticed that the top end was very crisp and clean and that surround localization was exceptional. This is what you would expect from small speakers that behave more like point sources and "smear" the image less than units in which the drivers (or cones thereof) subtend a significant angle. I was, however, conscious of the fact that the bass was all at the front of the room – in the corner, no less. My system is set up kitty-corner (at about 45 degrees to the walls) to minimize standing waves, and my sub is in the corner behind the TV. My normal system, however, also puts bass through the main front pair, bringing the bottom end out into the room more. This, coupled with the fact that there is absolutely no bass in the surrounds, made me more conscious that the bass was more center front than usual, albeit this is perfectly reasonable, as that’s where the bass is panned.
Despite the improved imaging I was noticing over my regular system, I also know that conventional 5.1 mixing techniques do not really allow for anything like accurate localization outside the front stage. Around the back you get something, but down the sides of the speaker array there is virtually no serious localization unless you turn your head. There are ways around this, however, that have been known for years, and there are now high-definition discs out there that use them to great effect, notably the award-winning Swing Live album from Chesky Records. The Ambisonic technology used on this album permits accurate localization almost anywhere in the room. I used the SACD version, playing the 4.0 mix that is in the hi-res multichannel area of this hybrid disc.
Sure enough, the ambience and acoustics of the New York jazz club in which this outstanding album was recorded leaped from the speakers, which in fact disappeared from consciousness, especially with eyes closed. This is something that few if any regular 5.1 recordings can achieve, where sounds tend to get sucked into the speakers, except for those across the front stage. I would suggest that what you want from this kind of recording is for the technology involved to disappear and take you to the venue, and that’s just what I experienced, despite the fact that my speakers, while in a respectable ITU arrangement (a pro audio standard for 5.1 speaker setup) for movie sound, are not ideally positioned for music listening (I would prefer a rectangle of some kind with me in the middle). A good surround recording played back correctly can literally overlay the acoustic of your listening room with the recorded acoustic environment – so much so that you are transported, and that’s just what happened here.
Talking of movies, I brought out "Oh Brother, Where Art Thou" on DVD, and set it up for DTS 5.1 replay. Obviously, a 5.1 movie soundtrack uses the center front extensively for dialogue, and in this case also for several of the (mono) pieces of music used in the film. Here, the extra oomph of the C-4 dual-woofer unit came into its own, with very clean and full performance, coupled with excellent intelligibility and accuracy.
I then played a DVD-Audio disc, Les Brown and his Band of Renown 1936-2001, "Session #55," expecting that some of Jane Monheit’s excellent vocals would provide another kind of test for the center channel. Not so: like many 5.1 music albums, the CF on this disc is very muted (presumably it’s just quietly there so that consumers don’t get worried it’s broken) and the front stage relies on traditional stereo’s "virtual center" for more integrated overall localization. The album sounded great, with a very lively mix and a smooth sound overall, enhanced by the cleanness of the top end on the RBH monitors. Again, front-stage localization was exemplary.
More or less anything I played on these speakers sounded good. The bass was firm, smooth and rounded, very much like the source material (in cases where I’d heard the material in the studio), and there was no lack of power. The MM-4s and the C-4 exhibit negligible audible distortion even if you push them – I played "Galliarde," the first track from the CD version of Dutch rock band Trace’s 1974 first album, at high level and only annoyed the neighbors: the RBH system didn’t even squawk.
I do have, however, a couple of niggles. Given the complexities of setting up a surround system at the best of times, I would have liked the manual to have given rather more detail than was provided by the few pages, most of which were largely descriptive and did not contribute a great deal to configuration. In particular, the use of the high and line-level "pass-through" modes, which could be of great benefit to users with simpler receivers or separate amps, was not discussed, despite the fact that people with simpler systems could probably do with more help, and there was nothing on configuring bass management in this mode or the "direct" mode I was using. Hopefully my comments above will help people set up this system. Similarly, the setting of the sub crossover frequency and phase was not dealt with. The phase control, incidentally, can be used to configure the sub for the acoustic environment it’s in. Depending on the location, the best bass can be "dialed up" experimentally with this control, and you would want to tweak it, for example, if you decide to point the sub into a corner rather than facing forward. At some setting, the bass will peak, and that’ll be the setting to use. (Don’t move the speaker to set it – reach around the back or whatever).
I did have some trouble finding the best crossover frequency setting. It seemed to me that perhaps the high end of the sub did not cross over smoothly to the low end of the monitors, probably a combination of my room’s acoustics and the small size of the mini-monitors, with a tendency to leave a "hole" at all the settings I tried. The MM-4s are probably down 3 dB by the time they get down to 100 Hz, and the sub may be rolling off by then on the way up, too. In theory, though, there should be enough overlap to get this to work – and perseverance furthers, as they say in the I Ching. It should also be noted, however, that this could simply be a difference in approach between the RBH system and my normal, much older and rather more studio-oriented setup, especially as JBLs are known for a tendency to develop a strong mid-range. Of course, you get used to almost anything when it comes to speakers, and after a couple of weeks listening daily to the RBH system, I just came to regard it as normal, so the apparent hole is imaginary. And for most people, a slight tendency towards "boom and tizz" will be fine. I expect I will find the JBLs unusually middly when I return to them!
Apart from those minor gripes, this is a fine speaker package. The speakers are extremely well built, solid, hefty and impressively made. The localization from these mini-monitors is excellent, and the apparent physical similarity to computer multimedia speakers should not be allowed to mislead you. This is a serious surround speaker system, including when we come to the bass end, which is plenty powerful enough for anything you will want it to do.
Providing excellent sound and physically compact, thus easy to position in a living room as opposed to a special listening or media room, this system would in fact also be great on a computer with a 5.1 sound card – the speakers are shielded to avoid magnetizing your TV or monitor.
In a competitive market, this $1,100 RBH 5.1 system is a logical step above fantastic offerings like the Energy Take 5.2 and the Monior Audio Brozne package (both priced at around $800 for a 5.1 setup). The build quality and component choices are improved because of the higher price tag on the RBH. Sonically, the RBH is heads and shoulders above mass market speaker systems, including the almighty Bose. While you can’t really saunter into the local outlet store or shopping mall to buy RBH speakers, they are worth the extra effort to find a dealer and get an audition.