Is There A Big Difference Between Subwoofers From Different Manufacturers

REL's system was created to cheaply get subs into peoples system (they don't have to buy additional items). It is a relatively poor way to do it and it fails to take advantage of a subwoofer's best advantages. People using that system should know that there are additional benefits they can grow into and really improve the performance of their system.

Rules of the Road.

Subwoofers have to be in corners or against walls.

Subwoofers have to be in phase with and time aligned with the main speakers.

Crossover should be between 80 and 100 Hz

Multiple subs in a symmetrical array are mandatory (at least two)

Bigger drivers are better. 10" is the smallest that should be used. At least four 10" subs would be needed. Two 12s will suffice.  

Similarly, apart from sound quality the design comes first for me.

Okay. I suppose that if I were coming at this from a technical point, I might feel the same. But as an audiophile, the sound quality is my first concern. I learned long ago that when theory and reality collide, reality wins every time.

But even as a designer, SQ should not give way to technical jargon IMO.

My subs are tucked away behind furniture so appearance isn't important.I've had a  Def Tech sub,a couple of Dayton subs, and now two HSUs and one SVS 2000.As you move up the line the cabinets are better quality and overall more attention to every aspect that results in improving sound quality should be obvious, not just bigger drivers and a few dbs lower.

 I really like the SVS app.Adjusting everything from the listening chair is wonderful.I'm far from being tech savvy and it's incredibly easy for me.

It is not just a rigid box design by itself, or throwing more money at it, or the latest app that carves out the contenders from the pretenders. There are three main challenges that we face. The link below and its condensed and edited article extract is one of the best reads on the issues of introducing subs into a two-channel system.

http://ultrafi.com/why-everybody-needs- ... subwoofer/

Why Everybody Needs a Good Subwoofer……And Why a Really Good Subwoofer is so Hard to Find

INTRO

Audiophiles and music lovers are missing out on one of the most dramatic improvements they can make to their audio system: Powered Subwoofers. Most audiophiles won’t even use the word “subwoofer” in public, let alone plug one in to their precious systems. There is a kind of snobbery that exists in the world of high-end audio aimed primarily at receivers, car audio, home theater and especially subwoofers. 

As a matter of fact, subwoofers are responsible for many people disliking both car audio and home theater, since it is the subwoofer in both of those situations that tends to call attention to the system and cause many of the problems.

The truth of the matter is that subwoofers have fully earned their bad reputation. They usually suck. Most of them sound boomy, muddy and out of control with an obnoxious bass overhang that lingers so long as to blur most of the musical information up until the next bass note is struck. We have all had our fair share of bad subwoofer experiences, whether it’s from a nearby car thumping so loud that it appears to be bouncing up off the road, or a home theater with such overblown bass that it causes you to feel nauseous half-way through the movie. You would think that high-end audio manufacturers would be above all of that, but you would be wrong. In many cases, their subwoofers are almost as bad as the mass-market models because they too, are trying to capitalize on the home theater trend that is sweeping the land.

(1) QUALITY BUILD SUBWOOFER AMP and its POWER SUPPLY IS EXPENSIVE. 

You see, it’s very difficult and expensive to build a good subwoofer. One reason is that a sub has to move a tremendous amount of air, which places big demands on the driver (or drivers). Moving lots of air requires a lot of power and that means an amp with a huge power supply, which can cost huge money.

(2) QUALITY BUILD SUBWOOFER BOX BUILD  IS EXPENSIVE 

Finally, in trying to move all of this air, the driver (or drivers) which operate in an enclosure, create tremendous pressure inside of the box itself. The cabinet walls must be able to handle this pressure without flexing or resonating. Building such a box involves heavy damping and bracing which gets very expensive. When you consider these requirements, you quickly realize that it is virtually impossible to build a really good subwoofer (I mean good enough for a high-end music system) for under $2000. Yet most of the subwoofers out there sell for between $800 and $1200. Manufacturers do this because their marketing research has shown them that that is what people want to spend on a sub, never mind the fact that what people want to spend and what it takes to get the job done right may be two different things. The result is that even most high-end manufacturers are putting out poorly constructed subwoofers that just don’t sound very good.

(3) JUST THROWING MORE-MONEY AT IT IS A MIRAGE, it’s the CROSSOVERS that matter

I don’t want to give you the impression that anyone who really wants to can build a good subwoofer so long as they are willing to throw enough money at the problem, because that really isn’t true either. There are some pretty expensive and well-constructed subwoofers out there that you would never want to plug into your music system because they would most certainly make the sound worse.

Why? Because of their crossovers. 

A crossover is inserted into your signal path in order to remove the lowest frequencies (the deep bass) from your main speakers so that they no longer have to do all of the dirty work. The deep bass will instead be dealt with by the subwoofer.

The #1 benefit of adding a high quality subwoofer to your system is not how it further extends the bass response, but how it can dramatically improve the sound of your existing power amp and main speakers from the midrange on up. That, my friends, is by far the most compelling reason to add a sub to your high-end music system.

Once your main speakers are freed from the burden of making deep bass, they will sound cleaner, faster and clearer, especially in the midrange and midbass. They will also image way better because there will be far less air pressure and therefore resonance and vibration affecting their cabinet walls. And since the power required to make the deep bass is provided by the subwoofer’s built-in amplifier, your main power amp will be free from that burden and begin to sound like a much more powerful amplifier.

The one big problem with all of this is that you need a crossover to roll off the deep bass in your system and achieve all of these benefits.

And the crossover that comes with almost every subwoofer on the market will cause more damage to your signal than can be overcome by these benefits. That is the main reason that audiophiles refuse to consider adding subwoofers, even very expensive onres with well built cabinets.

What @mijostyn said, though I disagree with some of the prioritizations mentioned here.

With subs it’s mainly about capacity, design principle and implementation. Through this structural integrity of the enclosure and overall build quality should be "sufficient," but personally I find the need to make them inert/heavy in the extreme to be unnecessary. I’m not saying rigid, heavy cabs don’t make a difference, but to which degree and at what cost (in more than one respect)? Some may find capacity and implementation the most important, others implementation mostly, and others again (like @mijostyn) stress the importance of enclosure inertness (among other things). There are different ways to attain prowess augmenting the mains in the lower octaves.

Capacity, i.e. sheer displacement area and also sensitivity is very important in my book. All things being equal, the less those cones move the lower the distortion, and the less power needed for a given SPL the more headroom. Headroom in the lowest frequencies is paramount (where prodigious amounts of energy can be released), because more of it equates into lower distortion and a cleaner, more effortless reproduction. To boot ample displacement gives you that important physical feel and power of music - vastly overlooked, I find.

Design principle matters. Balanced force approach has been mentioned. By far most subs today use direct radiating drivers in sealed cabs, because this way they can be made as small as possible (and the cabs more easily inert) and retain extension. It’s is the most inefficient approach though, but in multiples this can be somewhat ameliorated. Still, sealed designs have max. cone movement at the tune (contrary to vented cabs and others), and moreover the exposed, direct radiating driver is prone to emit mechanical noise - not least when working harder, which smaller drives in sealed cabs and limited numbers do. Mechanical driver noise = distortion. I prefer large, efficient designs with partially or completely hidden drivers in either horn and/or bandpass variations acting as force multipliers, and with pro drivers no less than 15" in diameter. These designs also bring "inherent" bracing to their enclosures due to horn paths and other design innards, and build in plywood not least are structurally very sound.

Implementation has been covered already. I would also stress the importance of at least two subs, stereo coupling, symmetrical-to-the-mains placement and, preferably, a cross-over no lower than 80Hz. I’m aware this usually involves the need for high-passing the main speakers, and that quite a few audiophiles are against this. Such things would be more easily demonstrated with actual demos to highlight the potential advantages (depending on the ears (and preconceptions) of those who’re listening) of such a configuration, also to narrow down the specific setup context in which the high-passing of the mains has been done - which of course matters a lot to the outcome and to prevent unnecessary generalizations either for or against HP’ing of mains.

So, it’s about choosing the designs that accommodates the above, I find, and this not least calls for the need to include DIY solutions. I’d disregard brands if it means making subs very expensive to get some minimum of physical requirements. In other words, hugely expensive subs from the likes of Magico and Wilson Audio are a waste of money if you ask me, although I’m sure others may disagree. This is below the Schroeder frequency we’re talking about, resonators meant to move air efficiently, cleanly, effortlessly and acoustically well implemented. Trying to make subs into some dubious, "sophisticated" affair akin to selling the idea of expensive, single item (well, two for stereo) small 2-way standmounts is severely sidetracked marketing B.S IMHO.