Does a REL subwoofer make the speakers' job easier?

@johnson0134 

Just a follow up! 
Did you eventually add the REL dual subs to your system. If yes,  then how  was your first-hand experience of adding the REL subwoofers to your system and how it changed the sound for you and any recommendations! What models of REL did you add?
Thanks.

I was amending my above post, and ran out of time before fully completing my thoughts.

As we know, a continuously-variable phase control is very uncommon on subwoofers. All the control on the Rythmik subs does is provide either no delay, or up to 16ms of delay. 16ms of delay does exactly the same thing as moving the sub 16 feet back in space (approximately; sound travels at about one foot per millisecond).

Audiophiles have long had to move their sub(s) around, searching for a location in the room where the sub and main speaker seem to best "blend", where the sub doesn’t sound separate from the loudspeaker. That effort involves two completely different issues: 1- the phase relationship between sub and speaker; and 2- the interaction of sub and room. Unfortunately, the two are often in conflict with one another; the best location for one issue is the worst for the other. That’s one reason integrating subs with speakers has always been such a hit-and-miss proposition.

The worst place to locate a sub (or speaker) is where the room is creating a "mode": either a resonant mode ("’room boom") or a null ("suck out"). What a continuously-variable phase control allows one to do is find the best location in a room in regard to the sub being in a non-mode location, and to then use the phase control to align the sub in time with the loudspeaker, rather than moving it physically (to a location where a room mode exists).

Room modes are completely a function of room dimensions, and you can see where the modes are most likely located in your room by putting its dimensions into one of the room mode calculators easily found on the ’net. Place your sub(s) where room modes are at their lowest level, then use the phase control to align the sub and speaker. An elegant solution to an old problem! ;-)

Unfortunately, it’s not that simple; the long wavelengths of low frequencies (often longer than the rooms dimensions)---upon reaching a room boundary---reflect back into the room, meeting other waves and combining with them to create an increase in response (when in phase) or a null (when out of phase) at the location where the waves meet. It can therefore be a complicated mess, one difficult to completely resolve. A continuously-variable phase control is but one tool to use in addressing the issue of sub/speaker/room integration. It's therefore no surprise that many critical audiophiles have never been fully satisfied with the results of adding subs to their loudspeakers. For them, Richard Vandersteen has done the hard work for you. Just buy his Model Seven or Kento Carbon. ;-)

@gladmo: I time after after time see and hear people laud REL for their high-level connection design. Well, Brian Ding provides both high-level AND line-level connections in the non-XLR/Standard Size versions of the plate amp of his Rythmik Audio subs (the face plates of which are clearly pictured on the company’s website)..

But he also includes a continuously-variable phase control, which he labels "DELAY". It provides from 0 milliseconds of delay (0 degrees of phase rotation) to 16 milliseconds (180 degrees of rotation), and anywhere in between. The phase switch included on other subs (providing either 0 degrees of rotation or 180 degrees)---including on all RELs’---is a complete joke, of very little practical value. And is in fact an insult to one’s intelligence.

The notion that a sub doesn't require a continuously-variable phase control because a sub is either in phase or is not is a bizarre one. If your cross-over frequency is centered at, say, 100Hz, both sub and main speaker are reproducing that frequency (the high-pass and low-pass filters creating a slope---a decline in output---of the drivers involved). If the wave from both reaches the listening position at the exact same time, their combined output creates a flat frequency response (when well designed and implemented ;-). If a 100Hz tones reaches the lp with the waves from the sub and main speaker completely out-of-phase (180 degrees of phase rotation, or delayed in time 16 milliseconds, commonly referred to as opposite polarity), the two waves will combine to create a deep null in the response. A smaller degree phase mis-alignment will create a shallower null. This is not opinion, it is a fact, one of course well known for a century by all loudspeaker designers. Speaker designers have to provide the same phase alignment between the bass woofers and midrange drivers in their full-range loudspeakers, so as to create a flat frequency response. The alignment between a sub and a loudspeaker is no different. Why WOULD it be?!

@hilde45 Thanks for the note! It seems there is a lack of common knowledge on how phase adjustment is performed with a variable phase adjustment.  Maybe I'll write one up on that too.

If I were the type of person to give for-profit businesses the benefit of the doubt regarding what seems to be neglectful, I might think there could be something related to the high level connections that Rel likes to include. I'm not an electrical engineer with expertise in audio electronics design, but maybe there's something innate there with matching phase? In other words, if you use the option for your sub to tap into your power amp outputs or your speaker wire signal, does that automatically align the phase of your sub to within 180 degrees of your speaker woofers, thereby providing some justification for the two position phase switch they use? I highly doubt that is the case, but it's something that has crossed my mind as to why Rel and others others have lacked variable phase adjustment controls for so many years, and still do, even on some really expensive products. Even if that were so, there's a lot of people that want to use the line level inputs, and they should be able to have variable phase adjustment like Rythmik provides... And these companies themselves should provide education on how exactly to perform the adjustment process.

@gladmo I hear you and @bdp24  has written a post on subs for the Ages. Really fantastic.

REL is clearly a good product and they have a very vocal and earnest fan base. As I said, I love my REL sub. BUT, as mentioned in bdp24's post, the ability to adjust phase in a variable way is an absolutely crucial feature for anyone without a dedicated listening room and the dozens of hours it takes to get a sub without variable phase placed. I agree it is just ridiculous for REL not to include this feature.

+1 @hilde45

It continues to blow my mind that big sub manufacturers like Kef and Rel don’t even have a phase dial for exact phase matching. Only two opposite settings? It’s simply bizarre to me. Apparently there’s consensus out there there only the tiniest percentage of people are actually aware of how impactful precise phase adjustment is for integration with loudspeakers, having learned through experience with using precision phase adjustments.

Rel hi level is incredible. Using Rel for over 22 years still have my Rel stentor 3,s with Extremas. In bedroom using two real 9x with Tannoy mini,s incredible

@johnson0134

Once you have added the dual subs to your system, It would be helpful, for the benefit of all,  if you could post your first-hand experience of adding the REL subwoofers to your system and how it changed the sound for you and any recommendations!

REL subs are support for lower end extension and do not provide a crossover to your main speaks, as others here have clarified. I think there is more debate on two vs. one sub and placement. Hearing where bass comes from is the issue -- it's impossible below certain frequencies, which are the frequencies the sub produces. REL recommends putting a sub at the place in the room where it maximizes low end extension at your seat. Hopefully that spot works in one's room. My experience is like @tantra4 in terms of integrating. The phase switch has always been adequate. Bass does change if you move your seat around the room in and out of of nodes. So you can play with seating position as well. Have fun experimenting!

In answer to the original question, a sub can make the main speaker job easier if it is crossed over with high and low pass filters (full crossover). This way the mains are not receiving bass frequencies and can deliver cleaner upper bass and midrange, depending on the main speaker configuration (2way, 3way)..

But the issue of phase and delay has been mentioned. Phase is not really proper time alignment, it is really just putting a late signal in phase, in fact usually making it even later.

Also be aware every sub probably has a few ms latency due to the electronics, cabinet design and impulse response of a large driver). I gather manufacturers are not eager to share this info. To compensate, it is necessary to delay the mains, not the sub. I have done this. One of my subs has 12ms latency, but it is still very nimble responsiveness (it is not sluggish when time aligned correctly)

In my system, there was quite noticeable improvement from even a 6ms adjustment, 12ms is obvious to me and frankly messes with the music timing let alone the acoustic interactions/cancellations.

With all this in mind, the approach promoted by REL to use high level inputs seems fundamentally flawed. Be wary of the marketing the REL dealers use.

Thank you for taking the time to write a response, everyone.  As someone who has never used a sub before, I am really grateful. I am pretty much set to buy a pair of REL subwoofers (picking them up in a few days) and will keep in mind the information you gave me here. Thanks again!

+1 @bdp24 

Thank you, bdp24, for the best brief subwoofer tutorial I've ever read. I made a screen shot of it for my now extensive file. It's humbling how much some of you know, and really understand, about the technical side of this hobby.

FWIW, I've got an NHT SubOne in my system, and it has the high-pass filter option attributed here to the Vandy, Hsu, and other designs. I find that connecting with this option does indeed improve the sound of the system as a whole—I presume for the reasons bdp24 so clearly articulated. However, the NHT also has a two-position phase switch, and I've found that engaging this (so, 180 degrees out of phase) also helps very slightly: it improves the integration, so that the overall sound calls no attention whatsoever to the sub while enriching the presentation in subtle but important ways. Perhaps I just happen to have the sub placed where "16 feet" of electronically simulated distance is just right. Or maybe I'm just not that critical a listener.

I'm with @bdp24  for sure:

So the Rythmik phase control allows one to position the sub where one wants it in the room (so as to avoid locations where room modes exist---peaks or nulls, a consequence of room dimensions), the phase control then used to align the sub with the main speakers. I would not own a sub without a continuously-variable phase control. The 0/180 phase switch is a joke, far too crude to be of much value in a high performance hi-fi system. IMO.

I did extensive measurement in my room with 3 subs to get the bass within 4 db from 20 to 400 hz. The adjustable phase was indispensable to doing this.

Phase can be a somewhat complex matter, but in the case of subs it is not. The phase switch on most subs gives only two options: either the signal is left as received, or it is rotated 180 degrees (the phase is flipped, i.e. reversed).

The phase control included in the Rythmik "standard size" plate amps is not a 0/180 switch, but rather a continuously-variable rotary knob control, providing from 0 degrees of phase rotation (no delay) to 180 degrees of phase rotation (16 milliseconds of delay). In 16ms sound travels approximately 16 feet (one foot per ms), so setting the Rythmik phase knob control to 180 degrees/16ms does the same thing as moving the subwoofer back 16 feet, but does it electronically instead of physically.

So the Rythmik phase control allows one to position the sub where one wants it in the room (so as to avoid locations where room modes exist---peaks or nulls, a consequence of room dimensions), the phase control then used to align the sub with the main speakers. I would not own a sub without a continuously-variable phase control. The 0/180 phase switch is a joke, far too crude to be of much value in a high performance hi-fi system. IMO.

As for the REL subs making the speakers’ job easier: as others have already said, the REL (and almost all other dubs) provides no filtering for the loudspeakers, so they and their amp(s) still "see" a full range signal. Not relieving the main amp and loudspeakers of having to reproduce low frequencies is to ignore one of the benefits of using sub(s). Bass frequencies "eat" far more of the power an amp creates than do higher frequencies; if you remove low frequencies from the signal the main amp receives, far more power will be available to the loudspeakers, and it will be lower in distortion. Removing the low bass duties from a loudspeaker will allow it to play louder, and with less distortion, especially true with planars.

As you read in an above post, Vandersteen offers a high-pass filter to remove bass from the signal sent to the main amp when using his subs; HSU does too. But you can easily install a simple 1st-order (6dB/octave) filter on the input jacks of your main amp; it consists of a single capacitor, the value of which is dependent upon the frequency at which you wish to crossover from your speakers to sub, and the input impedance of the amp. The formula to find the correct cap value may be found on the ’net.

Another route to take is to install a separate electronic crossover in your system, in-between your pre-amp and the amp for the speakers. A benefit of using a separate x/o instead of the Vandersteen or single-cap filter is that the x/o frequency is usually adjustable. If all you need is a 1st-order filter, the old Dahlquist will work okay (especially if you replace the original parts with higher quality ones), and can be found used for a coupla hundred bucks. Really good x/o’s provide adjustments for both frequency and slope (6/12/18/24dB/octave, 1st/2nd/3rd/4th-order). Pass makes a great one, but it of course ain’t cheap. Nelson Pass offered a cool little one in his First Watt line (model no. B4. Get it? ;-), but it is no longer available assembled, only as a DIY kit.

By the way, though REL is most well known for offering a high-level sub connection, the non-XLR versions of the Rythmik plate amps do as well, along with low-level (which REL does not).

I've run my main speakers full range with a couple of RELs for years and it sounds great. "Classdstreamer" answers his own question with 'my REL sub does perform super well in its system." Subs don't need to have adjustable "gradation" as things are either in phase or not. REL owners rarely wonder about that. It's simple, and easy to see phase adjustments work with RELs. Good subs add that bit of reality where low frequencies exist (as in the actual world) so main speakers can seem to take on more life-like tone.

@hilde45 Great point about the phase adjustment. I do feel that granular phase adjustment makes a difference for my affordable Jamo sub. But my REL sub does perform super well in its system. I wonder why REL doesn't provide more gradation in phase adjustment. 

I have a REL Storm subwoofer in my system. The REL subwoofer gets a full range signal from the amp. The subwoofer presents a very high impedance load to the amp, the amp acting mainly as a voltage source here. That is why the signal cable from the amp to a REL subwoofer has thin wires. The main speakers have the full power and full range of the amp, no loss to the tiny trickle taken by the subwoofer. The subwoofer gets exactly the same signal as the main speakers, so integration occurs naturally. I positioned my REL Storm near my listening position. It integrates like mad. I asked an experienced audio listener at my house if he thought I had a subwoofer in my system. He did not think so, even though that huge downward firing Storm was standing four feet in front of him. When I told him I did have a sub, he could not point to the source of bass. I am very happy with that arrangement.

The only sub that I know of that uses a high pass filter is Vandersteen.

And, yes, by utilizing the high pass crossover, the amp will be relieved of power demanding low frequencies.

B

1.  The sub would make the speakers’ job easier by not sending the low bass signal (i.e., below the crossover point) to them.

This can be true as long as the crossover in question has high pass filter capabilities. A feature very few powered subwoofers posses. A couple of exceptions are the JL Audio “E” series and I believe the Audio Kinesis “Swarm” (actually passive subs with an external amp). The other option would be to use an external crossover connected to your preamp outputs, which would split the signal that feeds your main and sub amps. Some examples of these would be the JL Audio CR-1, miniDSP as well as units made by dbx and XTA.

2. The signal sent to the speakers would still include the low bass even when the sub is used. Therefore the speakers would still receive the full range signal.

This is true with the connection method that you present.

Option 1 makes the job of your main speakers easier, option 2 does not.

You're not thinking too deeply. You're asking good questions. I had some of these, too. Have both REL and Rythmik. Like both, but Rythmik's adjustable phase is critical to getting room dialed in.

You're thinking too deeply about it.

This is audiophoolery-buy one and try it. There are plenty of happy REL users. The one that aren't simply didn't hear what they were expecting, and went with another brand.

I have owned both JL and REL. With JL, the integration was a nightmare (I did not try the external crossover). With REL, integration was seamless without compromising full range signal to my main speakers. The low bass extension with REL is just right (actually amazing), neither overpowering nor underwhelming in my system.  I can’t imagine my system without a pair of REL’s. For two channel system, always connect REL’s with High Level Neutrik Speakon connection, fine tune and enjoy! 

I was looking at both REL and JL Audio but ended up with Rythmik. I liked the fast servo sub and connect low level from my amp to the sub. My Parasound A21 has an RCA connection for both Left and Right channel and variable gain adjustment and connects directly to each stereo subwoofer(s). I push full range to my speakers and it seems to be easier to blend the low/mid low freqs between the sub and speaker.

speakers get full range signal with REL...JL is maybe what you are looking for...I prefer REL...crossover that doesn't degrade signal to main speakers is often quite expensive, though JL makes a great one...

Does the REL high level connection make the speakers job easier?  Well, no.  Neither option 1 or 2 makes the speakers job easier.  Option 1 may make the amps job easier.   Option 2 may make the sub integrate more seamlessly.