Acoustic Sounds

REL Acoustics


REL Acoustics S/812
By: Ken Redmond

January 22nd, 2024



The REL Acoustics S/812 Sub Bass Line Array

The Next Dimension in Bass

My relationship with subwoofers began in the late 70s while making my rounds at the Palmer House Hotel in Chicago, back then one of two summer Consumer Electronics Show high performance audio hotel sites. The other was the nearby Blackstone. The main show was at the giant McCormick Place Convention Center.

I walked into the Janis Audio display room, where owner/designer John Marovskis had set up a demo of his new Janis W1 subwoofer and Interphase crossover/amp. I anticipated that John would play music showcasing the subwoofer's contribution to the overall sound that focused on bottom-octave bass when he unexpectedly played a solo piano selection and skillfully used the subwoofer to enhance the sound. Even though the music selection did not have bass notes that specifically required a subwoofer, adding it made a noticeable difference, enhancing the piano's realism by more accurately reproducing its tonality and physical weight and adding a sense of space.

Thus, my journey with subwoofers began, and I quickly discovered that most were designed for cinema use, making them unsuitable for critical music listening. They often did more harm than good. I clung to my Janis setup until I encountered a pair of Vandersteen 2Wq subwoofers and added them to my 3A Signature speakers.

The Vandersteen combo provided 90% of the sound quality at 60% of the cost of the Vandersteen Model 5s I lusted for but could not afford—a very appealing value proposition that will rear its head again later in this review. 

During the 2000s, Home Theater gained immense popularity, which led to the emergence of a large subwoofer market. At that time, we sold at my store a considerable number of Velodyne and JL Audio subwoofers. Nonetheless, I continued to use my 2Wq's.  

I always struggled with the concept of adding a generic crossover, typically found in most powered subwoofers, to my high-end two-channel speaker system. My speaker system' crossover had been meticulously crafted with great care and precision to achieve the designer's intended sound, which was the sound I selected. To me, it didn't make sense to insert a crossover that impacts the sonic performance of my main speakers. When you adjust high and low pass filters to blend your main speakers with a powered sub, you essentially take on the role of a speaker designer. This task can be challenging for many people, and over the years, it has often resulted in poor outcomes that have given subwoofers a reputation for being "difficult."

I avoided using the subwoofer's crossover and let the main speaker system produce sound with the voice the designer intended. Then, I would "feather in" the bottom octave or two of bass to achieve full-range sound. Although this method also has its issues, it was my preferred approach.                                                                                                

Enter REL Acoustics around 2015 

My first conversation with John Hunter, REL Acoustics President and Head of Acoustic and Physical Design, was to discuss the possibility of selling REL subwoofers at the company I was managing. With our focus on Home Automation and Home Theater, we were selling a lot of JL Audio. After an hour-long, in-depth conversation, we mutually concluded at the time that REL would not be a good fit for us. Our company had plans to expand into a two-channel audio division, and we both agreed that would be the time for us to revisit my request. However, in our first conversation, I was impressed by John's expertise and his emphasis on subwoofer usage for two-channel music reproduction. He described REL's approach of "augmenting" the bass of the main speaker system instead of replacing it, which aligned with my perspective. To that end, REL refers to their woofers as Sub Bass Systems, not subwoofers. 

You Always Remember Your First 

While visiting RMAF 2019 (Rocky Mountain Audio Fest), I learned about the AMG Viella Forte turntable then distributed by Musical Surroundings. I headed to the exhibit room where local Denver A/V dealer Soundings, was showcasing the turntable. I noticed in the room a pair of Vienna Acoustics Liszt speakers, accompanied by three REL subwoofers stacked on either side. It was my first introduction to a "REL Six Pack" configuration.

During one listening session, someone pulled out a rare edition of a Led Zeppelin album to play, and the subsequent listening experience remains etched vividly in my memory. What I heard from the REL six-pack that day was much more than what I was experiencing with my two subwoofers. As the music started, I was expecting to be overwhelmed by the six 12" subwoofers playing, and while the deep bass was predictably impressive, what floored me was the depth and size of the sound and the recreation of the recording space.

Vienna Acoustic Liszt floor-standing speakers are not large speakers. However, combined with the REL six-pack, I heard sound quality I would have expected from a multi-hundred-thousand-dollar system typically found in the downstairs ballrooms. There's that value proposition again. 

Fast forward to the 2023 Florida Audio Expo, where Acora Acoustics showcased their reference VRC loudspeaker ($219K), declared the best sound in the show by virtually everyone who heard them. As I listened to the VRCs, my mind drifted back to the RMAF 2019 REL six-pack experience and I wondered what impact adding a REL six-pack to my Acora SRC-2s would have. While I had no illusion that it would turn my SRC-2s into VRCs, I wanted to experience how far up the ladder it would take me.

I touched base with John Hunter, who graciously agreed to send me a REL S/812 six-pack. Before I go further, let me tell you about it.

 REL S/812The REL S/812 

The S/812 resides at $3299.99 ($3499.00 on 2/1/24) and occupies the "sweet spot" in REL's subwoofer lineup that ranges from $499.00 to $10K each. It features a lightweight ContinuousCast™ 12-inch aluminum cone and a die-cast alloy driver basket. An aluminum cone driver can experience back wave distortion due to air movement behind it. REL strengthens and stiffens the cone's rear surface by adding a strategically placed, lightweight carbon fiber backing. This prevents the back wave from interfering with the main bass launch and by lowering bass distortion helps to improve overall sound quality.

REL S/812The S/812 also features a 12" down-firing carbon passive radiator employing REL's latest extreme long travel design, featuring a variable stiffness suspension. REL calls this its SuperProgressive™ radiator. The design's goal is for the the subwoofer to behave like a sealed box at low level but when there's demand, make it capable of delivering the 19Hz output of a 14" design.

REL AcousticsThe S/812's NextGen 5 amplifier boasts 800 watts continuous power output with 1000-watt peaks.  Connection options to suit various set-up needs include Neutrik Speakon high level-input connectors, low-level RCA stereo inputs, and separate XLR and RCA LFE input connections. There's also a high-level Neutrik Speakon output that can "daisy chain" multiple subwoofers.

REL highly recommends inputting high-level power amplifier speaker terminal outputs rather than low level preamp outs. The amp's output signal, REL claims, more closely resembles what's seen by your main speakers, providing the sub with the same sonic and electrical characteristics, including the amplifier's propagation delay. The result it a better blend and thus better integration between the subwoofer and main speakers, regardless of your power amplifier's design, be it tube, MOSFET or whatever. To make that connection REL provides a lengthy Neutrik Speakon—multi mini-spade terminated cable.

One of two toggle switches sets "Always On/Standby" and the other either "0" or "180" (degrees out of) Phase. Three variable knobs with but a single dot on each adjust level, LFE level, and crossover frequency. More helpful would be reference markings on the knob sides and level/crossover frequency gradation indications silkscreened onto the plate. REL's "count the clicks" adjustment methodology would be more convenient if the potentiometer clicks had a more definite feel.

REL's "secret sauce" is in their Perfect Filter design, said to extend the extreme low end bass frequencies, while simultaneously opening up air and delicacy in the middle and high frequencies. Specific information about the REL Perfect Filter is held close to the vest, but John Hunter provided the following when I asked him to explain the concept.

"As to the Perfect Filters, this is an all-analog circuit that lifts and extends output below 30Hz (Serie S)  in order to deliver more "perfect" low bass. It extends and increases the delivery of deep bass without engendering the mechanical/robotic sonic signature and slight delay of DSP.

 As with everything we do, these circuits are carefully evolved, shaped and listened to carefully in order to ensure that the positive aspects of producing rich, very extended deep bass are realized without audible degradation. The result is a filter that is responsible for greatly increasing the qualities of our Serie S and T/x models as well as our HT range of home theatre models. Each filter is developed and tuned for each specific model and they are a significant piece of the puzzle we had to solve in working to deliver a huge upgrade in sound from our previous models while keeping the cost increase reasonable and retaining our signature fast, natural sound." 

A deeper dive into REL's Perfect Filter can be found in the following video.

REL offers an unparalleled collection of instructional videos about bass, subwoofer/speaker setup, and room tuning. Even if you don't own a REL sub bass system, it's worth investing your time on their website. Just click on the Articles tab to find the videos. I suspect you will learn something that will help you with your system.

The subwoofer, measuring 17 inches wide by 17.5 inches high and 20 inches deep and weighing in at 75 pounds is available in two colors: Piano Black lacquer and Gloss White. Both impressive-looking finishes use eight coats of lacquer. Chrome-finished handles make it easy to move the subs around. Also included is a well-constructed grill that, unlike many manufacturers' offerings, is obviously not an afterthought. Very stable rails replace the usual four feet and provide both more stable support and an attractive "floating over the floor" appearance.

 S/812The Setup 

As luck would have it, Clay Parker, REL's Southeast Regional Manager and sub-bass system setup guru, lives about five hours from me and offered to shepherd me through the REL six-pack setup. Upon arrival of the palette holding the six cartons, I was instructed to unbox them, plug them into my AC power, and turn them on without setting/hooking them up. REL recommends letting the amplifiers charge overnight before set-up and calibration. The setup procedure that Clay walked me through was very similar to John Hunter's excellent video below. I could do no better explaining it.

If you don't have the time to watch John's explanation of the six-pack concept in the first five minutes of the video, it's essential to understand that it involves each layer of subwoofers doing a different task, and each subwoofer being individually adjustable to ensure optimal performance. The six-pack concept is NOT about six 12" subwoofers stacked atop one other all doing the same thing. I lived with a speaker system much like that for about three years. My Infinity IRS Beta loudspeakers had four 12" drivers in separate left/right columns all doing the same thing.

Infinity IRS BetaThe REL sub-bass line array is a wholly different approach. Clay Parker explained it to me this way:

In the movie "Jurassic Park", when the T Rex stomps on the ground, the impact is felt in three different ways. The bottom subs convey the initial blow to the earth, the middle subs spread out the aftershocks, and the top subs help convey the size of the area by conveying low-frequency ambiance cues.

Translate that concept to a kick drum, upright bass, or organ in a cathedral, and you start to understand the contributions the REL stack makes to the fundamental note, the overtones, and the decay.

Let's Listen 

After setting up and adjusting everything, I took some time to listen to music for a week or two before conducting a thorough evaluation. I wanted to ensure that my impressions weren't simply due to the large scale of this upgrade, rather that I could identify multiple areas where it made significant improvements.

My audition plan was to listen carefully to three different configurations to evaluate the impact the REL subs had on different music pieces. First, I would listen to the music only through my Acora SRC-2 speakers without subwoofers. Next, I would add the left and right bottom subs. Finally, I would listen to the music with all six subs playing.

Mark Levinson Acoustic Recording SeriesTo commemorate the moment I first heard the Janis subwoofer I chose to make Jazz at Long Wharf my first critical listen. Recorded by Mark Levinson in 1977, it showcases a jazz trio's live performance at the Long Wharf Theater in New Haven, Connecticut. Levinson utilized minimal microphones to capture the sound of the piano, upright bass, and drums. It is a simple, well-recorded live session in a theater setting, similar to my many experiences attending Jazz Trios at the LSU School of Music. It opens with the trio, then breaks into solos, then back to the trio finale. 

To provide an insightful review of my experience with the REL six-pack, I believe it would be more beneficial to share the raw comments from my written listening notes instead of a polished, wordy version. The experience of the REL six-pack is not just about its impact on any specific part of the frequency spectrum but more about the overall feeling it produces.

Here goes: 

No Subwoofer

Has the feel of 70s "Japanese Jazz" that is technically exemplary but lacking in soul, Pace, Rhythm, and Timing ( PRaT)

Foot not moving

Drums feel more closely miked and "smaller."

It feels like a recording of the session offered up on a stereo

The recording was presented between the speakers with good depth.

 Sounds like a very good stereo system playing a good recording.

Not much "magic" 

Two Subs added

The piano tone improves and sounds more realistic regarding the space it occupies on stage. The drums set has a more profound attack and better dynamics in deep bass and rim shots.

I still feel the boundaries of the listening room.

Now, it sounds like artistic musicians playing with much better interplay and expression.

I still feel like I am listening to a recording, albeit a much better one spatially and dynamically

Six Subs added


Now I feel like I am AT the recording session and have all the feel of sitting at the LSU music hall.

Listening room walls disappeared.

The Acoustic bass took control and is not buried in the music but stands out on its own and drives the music.

Dynamics are life-like, with outstanding rim shots and musician interplay.


Sheffield Labs "Harry James and His Big Band"

Let's take it up a notch and add more instruments with Harry James's The Foot Stomper from the Sheffield Labs Comin' From a Good Place album. 

No Subwoofer

Overall smaller sound

Sound like musicians are just going through the motions, maybe the first take of the morning

For God's sake, get these guys some coffee!

The back left and right of the soundstage are truncated. 


Two Subs added

The piano regained its position on the left side and increased in size and tone.

Considerable more depth, width, and space

The trombone tone is more life-like with richness and "blat."

Instruments starting to separate in location and timbre. 

Six Subs added

Acoustic bass is now anchoring and driving the music.

Instrument interplay is illuminated... It sounds like we have seasoned musicians playing who know each other.

NOW we got SWING!

Trumpet dynamics are much more balanced and correct.

Toe tappin' PraT.

Big Band! 

I intentionally highlighted these music selections to convey the positive attributes of the REL six-pack in areas other than their ability to move a lot of air. Adding the REL six-pack to my speakers significantly improved in both examples the sound quality and listening experience . The soundstage became broader and deeper, and the imaging had a more 3D quality with increased solidity of individual instruments. The bass notes were more defined, had a faster leading edge, with improved pitch definition and were well-integrated in time and space, resulting in an elevated music experience. The dynamics also increased, and the sensation that the music coming from different loudspeakers dissolved.

I was anticipating improved sound quality after installing the REL six-pack. However, I was impressed by its significant enhancement in recordings like these. The increased dynamic expression in all the instruments caught me off guard.

In 2005, Gary Koh of Genesis Advanced Loudspeakers was the first to expose me to the concept that bass overtones impact upper frequencies. He explained how it increases dynamics and can have a significant tonal effect on the treble. At the time, it seemed counterintuitive, but now it makes sense.

The REL stack added an openness and airiness to the synthesizer in Hans Zimmer's soundtrack from Interstellar. While two subwoofers easily reproduced the fundamental bass and moved a lot of air, as many subwoofers can, adding the REL six-pack to the Dreaming of the Crash cut was frankly stunning. The first two minutes are filled with sounds of wind and thunder, and I could almost feel the wind in my listening room. The thunder sounded realistically distant and rolled deeply through the room. The buildup that started at about 2:40 was mesmerizing, and by the end of the cut, I had been transported to a place that had a solitary, desolate feeling. Using just two of the REL subwoofers did not take me anywhere near that place.

Let's Move Some Air 

You can't have six 12" woofers and over six thousand watts of power sitting in your room and not want to punch the accelerator.

I wanted to try Company by Hedegaard, one of the ceiling tile loosening songs Acora used to demo their VRC loudspeakers at FLAX 2023.

Hedegaard "Oblivion"Using only my Acora SRC-2 speakers, I was very pleased with how well they handled the extremely low frequencies. Then I added the REL six-pack; the only listening note I wrote was "Stupid Good" with a smiley face. As expected, the sound filled the room; it rattled everything that was loose and, oddly, never sounded "loud."

What impressed me even more was how closely it resembled my FLAX 2023 Acora VRC experience, which put a $mile on my face. 

I conducted auditions of the three different configurations for two months and noticed that my notes were becoming repetitive. There was no question that the REL six-pack had a clear and overwhelmingly positive, consistent impact on my system. 

Here is a summary of how the different configurations "stack up"

No Sub = Smaller soundstage, less instrument definition/separation, and interplay with less dynamic expression.

Two Subs = Larger "feel" to the music with more profound fundamental bass impact and larger soundstage dimensions. The bass ambiance is still missing, and the music still sounds like it is being "stuffed into your room."

Six-Pack = Life-like "feel" to the music with superb dynamic expression, instrument definition/separation, and interplay. Listening room boundaries disappear, and instruments within the soundstage take on a more realistic density. You are transported to the recording venue/session.

REL six packLast Word(s…) 

While this section is titled "Last Words", I can summarize the impact the REL six-pack configuration had on my system in just one word: transformative

When we discuss the stereo soundstage, we refer to it as a three-dimensional entity with width, height, and depth perspectives. We attempt to visualize the outlines of instruments with palpable breadth and focus within that space. However, the truth is that the soundstage is an illusion created by invisible musicians, and the sense of "reality" we desire is a product of our imagination. The REL six-pack helped move my mind closer to that sense of "reality." 

As you move up most speaker manufacturers' product lines, you get better bass extension. Of course, there will also be improvements in the crossover, drivers, cabinet, etc., but you primarily pay for a more significant and impactful sound. However, sometimes, you may find the cost to climb a rung or two on your speaker manufacturer's ladder to be cost-prohibitive. For instance, in my case, the cost difference between my excellent SRC-2s and the VRCs is $171,000. Well out of my reach, much like when, in the '80s, I lusted after the Vandersteen 5a's.

But like the Vandersteen 3A Signature/ 2Wq subwoofer value I mentioned earlier in the review, the addition of 20k of REL subwoofers has allowed me to get 75% of the Acora VRC sound at 35% of the price—a value proposition I can consider. 

Having sold thousands of pieces of equipment and personally auditioned hundreds, I am hard-pressed to think of an individual component that has had a more significant overall impact on moving me closer to my personal Audio Nirvana than the REL six-pack configuration. Admittedly, the look is an acquired taste. Still, if you are contemplating a speaker upgrade and have room to add them to your system, I would suggest arranging a demo.

But be careful… As John Hunter is fond of saying. "Once you hear a six-pack, it is hard to unhear it."

I would agree. 

REL S/812   $3299.00 each …..  $3499.00 each as of 2/1/2024



Front-firing active driver, down-firing passive 


12 in. (300mm) long throw, Continuous CastAlloy™ cone structure, die-cast alloy chassis


12 in. (300mm), Carbon/Carbon flat cone structure, steel chassis 


-6dB at 19 Hz 


High-Level Neutrik Speakon, Low Level (2) RCA, (1) LFE RCA, (1) LFE XLR 


High-Level Neutrik Speakon, (1) LFE RCA or (1) LFE XLR


800 watts (RMS)


NextGen 5 Class D


REL AirShip II (sold separately)

Protection System








220-240 volts, 110-120 volts for certain markets


5 Amp 220 volts operation, 9 Amp 120 volts operation



17 x 17.5 x 20 in. (432 x 445 x 514 mm)


75 lbs. (34 kg)


Piano Black Lacquer, Gloss White Lacquer 8 coats

Supplied Accessories



Yes (10 Meters Nominal)




Manufacturer Information


REL Acoustics America

800 Addison St.

Berkeley, CA 94710

(510) 990-6005


  • 2024-01-22 05:06:26 PM

    Ronan O’Gorman wrote:

    Aloha Ken thanks for a wonderful review! I own a pair of REL T9i and my experience has been exceptional. Although on a much smaller scale to the "Six Pack" I paired them with the KEF LS50 META speakers and subsequently with Watkins Generation 4 speakers . I used the suggested track from the soundtrack to "tune in" the RELs. I use the REL Arrow wifi connects. The pairing with the Watkins Generation Four speakers is remarkable. The sound is rich, warm and expansive. For some reason I never achieved the same beautiful sound with the KEFs! I live on Kauai and I just auditioned a pair of Vandersteen Treo CT speakers from Stereo Unlimited in San Diego. Bruce and Ray set up the listening with the REL's and that same beautiful sound is present. They have just arrived in Kauai! The key for me is that the RELs do not sound boomy or bass forward, they just make a great pair of speakers sound remarkable. Thanks again for such a wonderful review. Every morning I click on the Tracking Angle and mahalo to Michael and the team for exceptional, insightful and honest reviews!

    • 2024-01-24 12:19:21 PM

      Ken Redmond wrote:

      Hi Ronan.... Thanks for checking in with us from Kauai. I visited there many years ago and loved it. I have to believe everything sounds just a bit better over there in that beautiful setting. Mahalo.... Ken

  • 2024-01-23 12:03:52 PM

    bwb wrote:

    The dial in process is fascinating, but seems to me so complicated that the odds of someone who has never done it pulling it off successfully on their own is close to zero... So did he come in and assist or did you do it yourself with remote support?

    In the video it looks like he is dialing it in at the sub. Don't you need to go listen at the listening position to hear what is happening as you make each click?

    • 2024-01-23 12:58:47 PM

      Gary Saluti wrote:

      Sounds like the "Perfect Filter" that John describes is the same concept that Vandersteen uses on their Quatro, Kento and Model 7.

    • 2024-01-23 07:16:58 PM

      Ken Redmond wrote:

      Clay came in to provide guidance, but you make a good point. Having an assistant at the back of the subs making the adjustments while you listen would be very beneficial. While it seems complex, once you get the two bottom subs dialed in, the upper four go much faster. The first sub is the key and we spent about an hour locking it in position. then about three hours on the entire subwoofer stack setup.

  • 2024-01-23 03:47:38 PM

    Jim Shue wrote:

    As a long time REL owner (stereo T7is) this is an effing AWESOME review! Ken knocks it out of the park again.

    Also John Hunter is the real deal in my books - he knows his stuff and unlike many in the industry has never wavered from supporting his customers at the highest level!

  • 2024-01-23 04:20:26 PM

    Silk Dome Mid wrote:

    I have a couple of nice SVS subs, but this is just a bit beyond anything I could afford or fit in my house. The divorce would be an added expense, and I might need to reinforce my foundation and buy the houses on both sides of mine. My favorite feature of the RELs is the handles. All midsize and larger subs should have them.

  • 2024-01-23 05:20:11 PM

    JACK L wrote:


    "To me, it didn't make sense to insert a crossover that impacts the sonic performance of my main speakers" qtd K Redmond

    Agreed. Subwoofer's job is for the bass enhancement of the main loudspeakers, not to replace part of it. Yet soo many brandname subs come with its own X-over network to replace part of the main loudspeakers. Noo good !

    Again posted here before, I think & in some other audio journals, mine is a 2.3 stereo system: KEF 2-way standspeakers + 3 active subs (L, R, L+R). All the 3 subs hooked up directly to the dedicated subwoofer outputs of my tube phono-premp. Simple & easy. No additional electronic x-overs involved. Very affordable price yet they work like magic for some 7years now.

    To better the sub performance, all my 3 subs are each placed on a wooden base on steel spikes under it - sorta 'floating' on the floor. Such arrangement is critical for any subs as to drain away the box vibrations into & dissipated by the floor below.

    This is specially crucial if the floor is wooden (like most residence in northern America). Any sub box always vibrates with built-in the woofer(s). This kinetic physics.

    To further reduce the sub wooden box vibration, I placed a massy wood block on top of each sub. Such added mass does help reduce the sub box vibration even further.

    My subs sub-bass sounds soo much cleaner & gone the boom than without the added mass on their boxes.

    My 2.3 stereo system rocks my 700 sqft basement den up to 105dB(C) peak SPL as measured with my digital sound level meter on playing my LPs (e.g. from the soundtrack: "Uranus" from "The Planets", a DGG digitally mastered LP).

    No way I could enjoy just phenomenal sound effect without subs !

    JACK L

    • 2024-01-23 05:55:26 PM

      Silk Dome Mid wrote:

      Isn't there a crossover built into the subwoofer output of your phono-preamp? There usually is. These crossovers are sometimes adjustable, sometimes fixed in the general area of 100 hz. Otherwise, the subs will continue to produce output well into the midrange area.

      • 2024-01-23 08:27:41 PM

        Silk Dome Mid wrote:

        The crossover in the preamp would of course be a low-pass crossover. I know you are running your main speakers full range, without any crossover except the ones built into them. Not having a low-pass crossover for the subs would allow them to produce sound above 100 hz or so and substantially muddy the sound of the system.

        • 2024-01-24 07:28:21 PM

          JACK L wrote:


          With my experience in handling 3 subs (L, R, & L+R) as posted above, please make sure do not place yr sub direct into the floor, particularly if it was wooden. The vibration of the wooden floor caused by the sub box only mess up the bass so reproduced.

          Even many brandname subs makers overlook such problem. As I posted above, make sure yr sub is placed on a rigid base with spikes to 'float' it over the floor below. The bass comes out much cleaner & less boomy.

          JACK L

      • 2024-01-24 07:12:48 PM

        JACK L wrote:


        "Isn't there a crossover built into the subwoofer output of your phono-preamp?" qtd Silk Dome Mid

        No. Just full audio spectrum out.

        Just use the built-in low-cut filter built in the subwoofer. Less electronics to mess around, better be the sound. This is physics.

        Careful adjustment of the low cut sub built-in low filter & the volume will do the job right.

        JACK L

        • 2024-01-25 12:56:47 PM

          Silk Dome Mid wrote:

          Thanks for the clarification. Doesn't a "low-cut filter" cut the lows? Do you mean a "high-cut filter"?

          • 2024-01-26 02:33:12 PM

            JACK L wrote:


            "Doesn't a "low-cut filter" cut the lows? " qtd Silk Dome Mid

            Sorry, I meant "low-pass filter" or hi-cut filter. My fingers often move faster than my brain.

            JACK L

            • 2024-01-26 04:53:50 PM

              Silk Dome Mid wrote:

              Same here. In one of my earlier comments I wrote "crossover" when I meant "filter". So it goes...

        • 2024-01-25 01:30:43 PM

          PeterPani wrote:

          I use a tubed preamp with stereo-output only. Tried subs ans sounded more ambient. But in the long run I got the feeling that the line output to the subs messed around with the line output to the tubed power amps. I did not try it again. I got the feeling it is to complex with a pure signal to part it to subs.

          • 2024-01-25 09:19:26 PM

            Ken Redmond wrote:

            Good ears Peter!! This is the issue I had many years ago when I tried to use my preamp to drive a powered subwoofer. I could write a whole paper on this. If your preamp has dual outputs and they are not individually buffered ( most are not), when you parallel the subwoofer input ( typically 10K ) with the preamp output, you are "showing" the subwoofer amp to the preamp, and it impacts the sound. I always heard that. I will credit Vince Glabo with MSB for explaining what I heard. MSB offers a Sub Isolator that keeps your preamp from "seeing" your sub amp if you must use the low-level signal to drive your subwoofer. Of course, this is avoided by using the high-level subwoofer input as REL recommends.

            • 2024-01-26 02:49:26 PM

              JACK L wrote:


              "you are "showing" the subwoofer amp to the preamp, and it impacts the sound" qtd K Redmond

              Yes. Very few, if any at all, pre-amps come with "buffered" sub output.

              My situation is different. The all-triode tube phono-preamp is my design-built 7 years+ ago, with L & R full-frequency range signal output dedicated for low-level active sub inputs. It does not affect the output level of the phono-preamp at all.

              So no additional built-in LF filter in my preamp for the sub at all. Least electronics to the sub purere is the sub bass !!

              JACK L

            • 2024-01-26 03:15:33 PM

              JACK L wrote:


              "Of course, this is avoided by using the high-level subwoofer input as REL recommends." qtd K Redmond

              Yes, "Great minds think alike" or again, I should say "Great ears listen alike' !

              I never like what REL's recommendations to its customers to use the power amps to drive the loudspeaker high-level inputs of its subs. REL claims bigtime using the power amp to drive the sub via its loudspeakers hi-level inputs will produce more 'seamless' bass effect to the main music.

              The reason is so basic: the signals come from the power amps are always contaminated by the harmonic, intermoduation & phase distortion & noise (e.g. hum) generated by the power amps themselves. It is the distortions from the power amps mess up the sub bass, making sound more "seamless" to many. Distortion is so addictive !

              In fact, I am having a huge debate with Paul McGowan of Copper Magazine & a few loyal REL followers these few days: Hi-level loudspeaker inputs vs low-level RCA inputs of an active sub, inculdiong REL.

              I told them I never use the loudspeaker hi-level inputs of my 3 subs (L, R , L+R) from my power amp due to the distortions of output signals. I only use pre-amp signals to drive the RCA low-level inputs of all my subs.

              This is physics !

              JACK L

            • 2024-01-26 03:37:59 PM

              JACK L wrote:


              "Of course, this is avoided by using the high-level subwoofer input as REL recommends." qtd K Redmond

              If we read between the lines of REL's recommendation using the loudspeakers hi-level inputs instead of RCA low-level inputs of REL & any other makes of subs, the hidden agenda of such recommendation is: marketeering & profiteering !

              Since only very few, if any at all, pre-amps come with buffered sub outputs, the only way is to use the loudspeakers hi-level input driven by the power amps direct. An ready stand-by alternative !

              This easy alternative surely saves the helpless hassle of many sub owners & to generate more sale for REL as well.

              REL even reportedly claims there is not distortion coming out from any power amps that can affect the bass at all !!!!!!!!!

              My goodness! ALL active devices produce various forms of distortions. This is electronics ABC. Sorry I just can buy such sales pitch given my decades career electrIcal engieerinng discipline.

              JACK L

            • 2024-01-26 04:04:28 PM

              JACK L wrote:


              "If your preamp has dual outputs and they are not individually buffered ( most are not), when you parallel the subwoofer input ( typically 10K ) with the preamp output, you are "showing" the subwoofer amp to the preamp, and it impacts the sound. " qtd K Redmond


              In fact, since I started installing subs for my stereo systems some 7 years ago, I design/built an external FET buffer (high I/P impedance to match my tube phono-preamp & low impedance O/P to match the I/P impedance of the RCA low-level sub inputs.)

              I though it should work OK in theory at least but it is not that OK sonically after a few months using it. So I took out the external buffer & hook it up direct without any buffer. The music comes up sooo much better & more musical !!! Such without buffer arrangement is up to day. Musically no problem.

              After all, the volume level of my phono-preamp works independently from the output level of my sub out anyway !

              No pain no gain ! We all learn from trial & error.

              JACK L

  • 2024-01-23 05:24:57 PM

    Jeff 'Glotz' Glotzer wrote:

    Great, fun review! I have stereo REL T7x's for my Magneplanar 1.7i's and they are absolute blend and natural fit. Stereo is def the way to go, but I imagine for those well-heeled, 6 packs are an absolute blast.

  • 2024-01-24 02:33:22 PM

    tim davis wrote:

    I would love to see/hear a shootout between this sub system and a pair of Danny Ritchie's Triple Threat open baffle servo subwoofers priced @ 4,150 dollars US total for the 2 plate amps & 6 subs & dual flatpack kit enclosures.