REL Acoustics Ltd., Stentor III Sub Bass System

REL Acoustics Ltd., Stentor III Sub Bass System


Frank Peraino

9 October 2002


10″ Big Ten Volt Driver (long throw)
Super ARM™ loaded cabinet
Enclosure Volume: 70 liters
Frequency Range: 12-100 Hz
DC Coupled, 300 watts RMS, 600 watts peak
High & Low-Level Two Channel Balanced and Unbalanced Input Connections & Neutrik Speaker-Level Inputs
Dimensions: 27.5″ W × 23″H × 17.5″D (65 × 59 × 41 cm)
Weight: 133 lbs.

REL Acoustics Ltd.
North Road, Bridgend Industrial Estate
Bridgend, CF31 3TP, Untied Kingdom

US Importer:
Address: 2431 Fifth Street
Berkeley, CA 94710
Telephone: (510) 843-4500
Fax: (510) 843-7120

We Don’t Need No Stinkin’ Boomboxes!

Alright, I am willing to admit right up front my bias against and preconceived notions of subwoofers prior to my first exposure to the REL ST series of Sub-Bass Systems-namely, for anything other than home theater applications, I was not a subwoofer kinda guy. My previous experiences with subwoofers left me with the opinion that subwoofers either imposed themselves on fuller range loudspeakers or did not blend seamlessly enough with monitors to seriously consider them a valuable asset to any good system. To me, a subwoofer’s benefit was outweighed by its burden. That is, until I heard what the REL Stentor III did for a set of Sonus Faber Grand Pianos and, eventually, what it did in my system.

My friend and fellow reviewer at the late Ultimate Audio, Rufus Smith, one day related to me his experiences with a REL Stadium III that I found completely antithetical to my experiences with subwoofers. So when I found out that Allan Haggar of Sumiko was going to be demonstrating the REL Stadium III and Stentor III at Overture Audio in Ann Arbor, I decided to make the 30 minute trek down the road to see if Rufus was on to something or just having a senior moment (sorry buddy). REL and Sumiko both call the REL ST Series of products “sub-bass systems” as opposed to subwoofers – a moniker I was about to learn was certainly appropriate. When I arrived, it was about an hour from closing and Allan graciously offered to stay past hours to give me a private demonstration. Allan asked if I preferred hearing the smaller Stadium or the larger Stentor, and I chose the bigger, much beefier Stentor (it’s a testosterone thing). What followed caused me to rethink my old biases against subwoofers.


The REL line of sub-bass systems is equally comfortable doing duty in either two-channel or home theater application. However, this review is limited to two-channel use. The Stentor III is a 133-pound, beautifully veneered piece of furniture with a dark glass top that exudes first rate fit and finish. Yet the Stentor III is not just another pretty face and, in this instance, form follows function. Inside the Stentor III you will find a powerful 300-watt built-in amplifier (50% more power than its predecessor, the Stentor II) with a self-limiter to protect against overload and an improved die-cast frame 10″ Volt driver. The enclosure is an ultra rigid enclosure that incorporates REL’s proprietary “Super Acoustic Resistive Matrix” (ARM) loading which, in essence, is a series of chambers leading to the port that re-matches the driver in a somewhat similar way to a transmission line. The effect is an enclosure that produces bass with extension, depth and impact completely out of proportion to what you would expect from a single 10″ driver. The Stentor III is stated to extend down to 12 Hz (-6 dB).

The Stentor III, like its siblings in the ST line, incorporates a system of crossover and gain controls and varied inputs which allows the user a flexibility that should suit almost any room and allow the seamless integration with almost any speakers. Adjustments include a coarse and a fine gain control, a combination of crossover frequencies ranging from 22 to 95 Hz as well the ability to reverse phase. The inputs include low-level unbalanced RCA inputs (e.g., for subwoofer out or preamp outputs), an unbalanced high-level input via Neutrik Speakon connectors for signals directly from the speakers terminals of your amplifier(s) and high and low balanced inputs, also via Neutrik Speakon connectors.


Set-up may be confusing depending on whether you have been advised by the dealer, who has probably been trained by Sumiko, or if you then choose to read the operating instructions by REL, which differ from that suggested by Sumiko. Since Allan Haggar of Sumiko, conducted my Stentor III audition as well as my home set up, I will briefly describe their philosophy. Allan started with the Stentor III in the front corner with the control panel facing the sidewall. Using the soundtrack to Sneakers with its repetitive deep bass line, Allan first set the proper phase by switching the phase setting to determine which setting produced the louder bass. That done, he started moving the Stentor III out diagonally from the corner, listening for the greatest output and deepest extension. From there, he began adjusting the coarse and fine gain controls to determine when the Stentor III began to impose itself on the main speakers. Finally, after that adjustment had been made, we began the rather slow process of adjusting the crossover setting and the fine gain control to reach the most seamless integration between the Stentor III and my main speakers. In my system, the Innersound Eros MK-II has a 10″ transmission line woofer which extends to 24 Hz, so we ended up with the Stentor III crossed over at a low 23 Hz to allow it to “come up” under the Eros woofers-truly acting as a sub-bass system. I should also point out that the Stentor III was being driven off the speaker terminals of the Eros’ bass amp/crossover. Since the REL does not insert itself in the signal path, my Eros are then still running full range. The result, as I will explain was nothing short of amazing after we finally dialed in the Stentor III. Although this set up process can be tedious and lengthy, it will pay dividends that make the benefit easily worth the burden. At first, I felt that I was not able to hear some of the subtle differences in placement and phase setting that Allan heard. However, it was VERY easy to hear when the Stentor III locked in at the end when we switched between 23 and 25 Hz or when we went one click up on the fine gain control. Today, after having had the Stentor III in my system for a year, I can easily hear the difference one small increase in the fine gain control makes and how that small increase in the fine gain throws off the balance and integration of my system.

Nothing Up My Sleeve — Presto!

Before describing the sound of the Stentor III in my system, I thought it would be helpful to describe what I heard in the dealer demo that made me explore this amazing sub-bass system. About a year ago at Overture Audio in Ann Arbor, Michigan, I heard the Stentor III demonstrated with Sonus Faber Grand Pianos in a fairly large and untreated room driven by Linn electronics and the venerable Linn Sondek CD-12. Before strutting the Stentor’s “bass” stuff, Allan asked me to listen to a solo classical piano piece by Evgeny Kissin, first sans Stentor III. Reportedly, the particular cut he played had virtually no information below 70 Hz. Thus, theoretically, the Stentor III, which was crossed over at either 23 or 25 Hz and was being driven off the speaker terminals of the Linn amplifiers, should not have added or subtracted much of anything to the selection. So much for theory. The sense of space and venue with the Stentor III engaged was so much more realistic that I would not have believed it if I hadn’t heard it myself. In fact, to make sure my brain wasn’t playing tricks on me (or that Allan wasn’t some sort of audio David Copperfield), Allan sat on the Stentor III while I manned the CD-12 remote and he would engage and disengage the Stentor III (without telling me which was which) as I would repeat the track on the CD. It didn’t take any one with a golden ear to easily pick out when the Stentor III was engaged-it was that much better with it in the system. Obviously, this was an effective demonstration approach and one that left me very eager to hear what the Stentor III could do with information well below the 30 Hz level. It did not disappoint!

Bass is the Place

After this demonstration, I requested Sumiko allow Allan to set one up in my system, which he graciously did. After set-up and break-in, I was able to appreciate just what a sub-bass system was and what it could do (and what it shouldn’t do). In my system, the Stentor III, as it did in the earlier demonstration in Ann Arbor, dramatically increased the sense of venue, improved the air and space around an instrument or performer and simply gave me a greater sense of what transpired in the studio or at the event. I must admit that even if this were all the Stentor III did for my system, it would be worth its asking price. However, what the Stentor III did for my full range Eros’ and my system’s bass performance made this a no brainer. I should note that the transmission line woofer in the Eros is no slouch in digging deep and doesn’t leave one feeling like he isn’t hearing deep bass like a monitor does. However, the Stentor III crossed over at 23 Hz and supplementing the Eros woofer did something I did not expect. Yes, I expected deeper bass extension, more impact and weight (which the Stentor III delivered in spades), but what I did not expect was that even with all those improvements, the bass was now tighter and more articulate.

To give you an idea of some of the music I used to gage this effect, I played a fabulous CD by bassist Brian Bromberg entitled Wood [A440 Music CD 4001]. For any fan of jazz acoustic bass, this CD is required listening and has spectacular solo cuts of “Come Together” by Lennon/McCartney and “All Blues” by Miles Davis. On the first cut, “The Saga of Harrison Crabfeathers,” Bromberg’s 300-year-old Matteo Guersam bass was so rich, so full and so woody sounding, that I could feel it in my soul as well as my gut when he rattled his strings. Some electric bass lovers may think an acoustic bass sounds anemic or recessed when hearing one played backed on a home system. However, if you have ever heard a good acoustic bass in a small live venue, they extend much deeper and have more impact than may be evident in many recordings or on many home systems. With the REL Stentor III, Brian Bromberg’s bass was anything but anemic. It had all the impact, body and depth without any smearing or bloat. The Stentor III equally improved electric bass performance. Every bassist, from Béla Fleck and the Flecktones’ energetic Victor Wooten to Abe Laboriel to the inimitable Francis Rocco Prestia of Tower of Power, was closer to the real thing. Their bass lines were more clearly delineated, more impactful and deeper with the Stentor III. Not only bass, but also kick drums, church organs, tubas, trombones and baritone saxes had greater visceral impact with the Stentor III. However, the icing on the cake was that every instrument, every voice, every nuance of the recording had a greater degree of focus and airiness-a much improved spaciousness, openness and, at the risk of redundancy, sense of venue and magic that they did not have sans Stentor III. With the Stentor III in my system, I heard a greater sense of ease, the Eros sounding even more unforced and effortless. Soundstage depth and, to a lesser degree, width was also improved. With such seamless integration, I heard none of the typical unwanted by-products normally associated with subwoofers that I had come to expect – e.g., decreased purity and clarity (usually from the sub’s internal amp/crossover that is placed n the signal path), poor integration with the main speaker and bass boominess and bloat.

At $5,000 the Stentor III is not cheap, but considering what it did for my system and what it can probably do to yours, for many music lovers, the improvements will justify the price of admission. But be warned, the Stentor III is not going to be able to show its stuff (nor will you be happy) in typical subwoofer type two-channel applications where it is used to compensate for bass-challenged speakers or where it is crossed over too high so as to intrude on the main speakers. Used as supplement to your main speakers and set up properly, the REL Stentor III will blend seamlessly with almost any speaker and will improve not only your systems’ bass response, but it will improve your system in areas you may not have previously associated with subwoofers! I liked what the Stentor III did for my system so much, I bought not one, but two Stentor IIIs. My highest recommendation!

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One thought on "REL Acoustics Ltd., Stentor III Sub Bass System"

  1. Be interesting to hear how the stentor performs compared to more modern subs like SVS

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