RBH T-2 Set-Up

The RBH Sound T System is by far the largest speaker system I have ever reviewed and integrated into a home theater set-up. I was a bit overwhelmed by the amount of boxes that the delivery person brought to my front door when the system arrived. I quickly unpacked the system, broke down the boxes and stowed them away in my attic before the wife came home to avoid her seeing our home in disarray.

My room is a bit more challenging to get a system's bass response just right then this picture would lead you to believe. I have two strikes against me, vaulted ceilings, and a partly open front wall behind the main speakers to the kitchen/dining room area. The left speaker is coupled nicely a few feet away between two adjacent walls. However the right speaker side/back wall opens to another room creating asymmetrical bass loading that if the system is not set-up properly, can lead to bass anomalies usually in the form of suck outs or bumps at particular frequencies. This is why I am so adamant about variable phase/group delay control and/or inclusion of a PEQ for subwoofer amplifiers and processors.

Properly setting up the T-2 System, given my room dynamics and the speaker systems complexity and size proved to be a learning experience. I was fortunate to have Shane Rich on hand to assist in the set-up of this system and have tabulated my set up notes for the benefit of any potential future owners.

First you must decide as to how you plan on hooking up the 1010-SEN subwoofers to your A/V Processor/Receiver (AVP). The three primary options have associated trade offs, thus I recommend choosing which it right for your application and results in the least amount of compromises.

A) Line Level: Subwoofer output of AVP to SA-400 subwoofer amplifiers.

B) L ine Level: Main Channel outputs of AVP to SA-400 subwoofer amplifiers.

C) S peaker Level: Main Channel outputs of AVP to SA-400 subwoofer amplifiers.

The advantage to option A is that the user can retain subwoofer level control via their AVP after the system has been properly set-up.

This is particularly critical for a user that listens to all current multi-channel surround and music formats due to the inherent differences of subwoofer levels depending on format and actual recording. The downside is if the AVP is limited to a single or dual mono subwoofer output, you lose the ability of maintaining stereo bass below the crossover frequency of the T-1 satellites.

The advantage to option B is that you now have stereo bass feature and "always on" subwoofer level and control for all modes of operation. The downside is you lose the ability to adjust subwoofer level control via the AVP. In addition, some AVP's dynamically limit the LFE information when recombining that signal to the main channels in set-ups with no dedicated subwoofers, so be advised and proceed with caution.

The same advantages/disadvantages from option B apply to option C, except now you have speaker wires to contend with and cable dealers that may wish to sell you snake oil. I ultimately choose option A for my set-up since it represented the least amount of tradeoffs given my reference gear and room dynamics.

It takes (2) SA-400 amps (one per 1010-SEN subwoofer) to power the T System. Unlike most subwoofer amps which are Class D, the SA-400 is a true 400 watt Class AB/G design. While digital amps are not necessarily a bad thing, especially for subwoofers, I still often prefer the performance of a good old linear amp. In this respect, the SA-400 really delivered what seemed to be limitless clean power to the subwoofers with minimal heat dissipation. I suspect the fact that a good job of adequately heat sinking the output devices, combined with the multi rail Class G operation during high power demands resulted in a powerful amplifier that could be stacked with moderate ventilation and not melt nearby furniture or equipment. Heat dissipation was never a problem in my set-up, even during my extended loud, bone crushing Terminator 3 listening sessions.

The backpanel of the T System contains 5 way binding posts for both the Satellite and Bass Modules allowing for bi-wiring or bi-amping. In my set-up, I left the jumpers in place and connected the Satellites to the Denon AVR-5803 front channel amps and each Bass Module to a separate SA-400 subwoofer amp.

Ok, so now that I figured out the best way to connect the T System to my setup, it was time to figure out how to adjust the following variables for optimal playback performance:

A) AVP Bass Management

B) Subwoofer Amps (SA-400) Settings

Due to the unique design of the RBH Sound T System, much care must be taken to ensure proper integration of the T-1 satellites and 1010-SEN subwoofers. Since the T-1 satellites have a lower end extension of about 40Hz, one would normally consider this to qualify for "Large" setting with a subwoofer crossover in the 60-80Hz region. I was the one who originally thought this until LMS and Sencore measurements, as well as my ears, dictated otherwise. Thanks to my rather non ideal room, typical with most Floridian houses endowed with vaulted ceilings and open architecture, I had to do things a bit differently and rather unconventionally from what I normally recommend. In the past I used to scream about the disadvantages of high crossover settings when mating with large bass capable speakers due to localization of bass pressure waves and doubling of bass which commonly excites room modes. However, in my situation it was a must, and the very fact that I now integrated two subwoofers in different parts of the room seemed to quickly nullify my concerns. Since the room was now loaded in this fashion, it appeared to help average out the bass response making it easier to integrate with a higher crossover setting within the room. While my measurements at the listening position were starting to look good, there were still too many nasty room modes and suck outs that I could not live with. Because I had the subwoofers connected in parallel to the mono subwoofer output of the Denon AVR-5803 receiver, attempting to utilize the subwoofer group delay within the receiver was senseless. In order for group delay changes to be effective, you must have independent adjustment capabilities for at least one of the subwoofers in the system otherwise you are simply changing relative phase of the signal. At this point, I had to turn to adjusting the level and phase controls of the SA-400 subwoofer amplifiers to dial in a more optimal system bass response. Unfortunately the RBH Sound SA-400 amplifiers lack variable phase control and any sort of equalization or room correction. Thus the only tools these amps were armed with to manipulate subwoofer response for better room integration were: {0/180 Phase Switch, Defeatable Crossover, Level Control}. After an hour or so of playing around with these variables on both subwoofer amps, I settled on the best measurable response. Incidentally I managed to find a host of settings that allowed for very good bass integration with the AVP bass management set to "Small" for all speakers and 100Hz for the crossovers.

Without a variable phase control, I had to trick the right subwoofer into thinking I was changing its phase response by enabling one of the SA-400 amps internal crossovers to cascade it with the AVP 100Hz crossover. I would have preferred RBH Sound to include a variable phase control as opposed to a 0/180 switch in the amplifiers to avoid taking this step. RBH informed me that all of their newer integrated subwoofer amplifiers have this feature and the SA-400 is the last amp in their line up that will eventually get it. Lucky me :-( My band aid fix of using the cascaded crossover really worked well in my situation as I all but squashed the worst suckout to within -5 dB for less than 10Hz bandwidth (see Figure 4). However, yielding an overall good bass response came at a cost by bumping subwoofer level up a bit hotter than ideal causing a 10-15dB bump from 25-40Hz. This is something that I can live with since I do like my low end bass extension a bit thick. In addition, based on the Fletcher & Munson Curve for human hearing, our sensitivity in this frequency range could certainly use a little boost, not to mention most recordings are a little thin in this range. Ultimately I would have liked to smooth out this bump a bit with a Parametric Equalizer (PEQ) and expressed my disappointment to RBH Sound for the lack of its inclusion to their excellent SA-400 subwoofer amplifiers and suggested incorporating this feature in future designs.