My short answer is, two smaller subs instead of one bigger sub.
The following is my long answer.
Off and on over the course of a decade or so I tried building a sub that was "fast" enough to mate well with Maggies and Quads, on the theory that there might be a market for such. I built sealed boxes, low-tuned vented boxes, transmission lines (many different geometries), equalized dipoles, aperiodics, isobarics, and pretty much anything that seemed promising except for a full-sized horn. Some were better than others, but none passed the test.
The one day a really smart guy, Dr. Earl Geddes, taught me that the problem is room interaction, and regardless of how "tight" and "fast" a sub is, the room will impose large peaks and dips that will dominate its response. It is the peaks that are especially detrimental, in that they decay slower than the rest of the spectrum. His suggestion was to use four small subs asymmetrically distributed, such that each produces a different room-interaction peak-and-dip pattern, and the sum of the four dissimilar peak-and-dip patterns would be much smoother (and therefore much "faster") than any one alone.
This made sense to me. I was aware of an AES paper that showed a dipole has significantly smoother in-room bass than a monopole, and a dipole is two monopoles back-to-back with the polarity of one reversed, plus a path-length-induced time delay between them.
The general principle I learned from Earl is, the more intelligently-distributed bass sources within a room, the smoother the in-room bass. Two subs are potentially twice as smooth as one, and four subs are potentially twice as smooth as two. A dipolehas roughly twice as smooth in-room as a monopole in the bass region, so four intelligently-distributed monopole subs are theoretically comparable to two dipoles.
If you do a casual survey of relevant posts by Maggie and Quad owners, I think this is what you will find: Those who have tried a single sub usually go back to using no sub, and those who have tried two subs usually keep them in the system. I think this is because two subs exhibit less in-room smoothness discrepancy relative to a pair of dipole mains than does a single sub. So don’t fall into the trap of thinking "I’ll try one sub and if it’s an improvement then I’ll add another." One sub probably won’t be a worthwhile net improvement.
So to get back to your question, I believe two intelligently-positioned subs would be smoother (and therefore potentially "tighter") in-room than just one. Some EQ or other adjustability might be called for, because the amount of boundary reinforcement varies significantly from one room to another. If the two subs have continuously-variable phase controls, that might be sufficient adjustability: Set their phases 90 degrees apart to begin with, and adjust their relative phases from there (along with your adjustments of level and frequency).
I don’t mean to dismiss the qualitative differences between different subwoofer models, but I think the room-interaction advantage of two small subs intelligently distributed would probably outweigh the benefits that the single larger (more expensive) sub has to offer.
distributed multi-sub advocate
REL subs are the company you should be looking at. Their S Series subs are the best cost effective way to marry a speaker to a sub and not get anything but better everything from mids to low end out of it. This is using their special connections that take the amplifier outputs for the sound. This matches what is coming out of the speaker better. And REL is a super fast system, and can keep up with the speed of the speakers. Even Martin Logans will sound like the REL is part of the speaker system. I have to mention that 2 RELs are really the only way to fly, having one for each channel for true stereo separation and room filling balance. Be warned.... once you hear a properly setup REL dual sub setup..... you can't unhear it. It's worth every cent to get the S Series or better. REL.net..... Cheers
+1 for the VANDERSTEEN
Reposted article provides a good summation of the conflicting strengths and warts in setting up a sub for music properly
August 3, 2008 by ultrafi in Tips, Tricks & Info | Comments Off on Why Everybody Needs a Good Subwoofer…
" …And Why a Really Good Subwoofer is so Hard to Find
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.
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. 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 $1000. Yet most of the subwoofers out there sell for between $500 and $900. 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.
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 subwooferto 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 ones with well built cabinets.
Enter the Vandersteen 2Wq 300 watt powered subwoofer.
This is the only subwoofer that is specifically designed to be inserted into the highest of high-end music systems without doing any harm to the precious signal. So how does Vandersteen do it? Simply. In fact his crossover scheme is so ingeniously simple that it’s a wonder nobody else thought of doing it the same way. I’ll spare you an in-depth description and just say that the only thing you end up inserting into your system is a couple of high quality capacitors. That’s it, nothing more! No additional wires or gadgets enter your signal path. Hell, you don’t even have to disconnect the wire between your amp and speakers to add this subwoofer. The model 2Wq sub uses the same basic crossover scheme as the $15,000 flagship Model 5As. As a matter of fact, you can even run the specially designed Model 5A crossovers (M5-HP) with the 2Wq if you want the most transparent sound imaginable.
So what about the other reason to add a subwoofer to your system: for more powerful and extended bass? I don’t care how big your main speakers are, they’re no match for a good subwoofer in the bass. A really good subwoofer can run rings around the best floorstanding speakers when it comes to bass extension, power and control because it is designed to be good at that and nothing but that, whereas main speakers have to be good at higher frequencies as well. Ideally, you want two subwoofers so that you have true stereo separation down deep into the bass. Stereo subs can also help to lessen room interaction problems by providing two discrete sources of bass information. Remember, if you can’t afford to buy two subwoofers at once, you can always add the second one later. Adding a pair of 300 watt powered subwoofers is exactly like adding a pair of 300 watt monoblock amplifiers to your system and upgrading to a pair of better main speakers at the same time. The beauty is that you don’t have to replace your main power amp or speakers to do it.
But there is a problem here as well. Everything comes at a price, and the price you pay with most subwoofers is that when you add them and their built-in amplifiers to your system, they don’t tend to blend or integrate well with the sound of your power amp and speakers. This is especially true if you own a tube amp, because the character of your amp is nothing like the character of the big solid-state amp that is built into most subwoofers. The result is that your system sounds split in half. You can hear where one part of the system leaves off (namely your amp and speakers) and where the other part takes over (the sub and its amp). This is a HUGE problem for audiophiles who aren’t willing to destroy their system’s coherence for additional power and bass extension. Fortunately, Vandersteenhas the perfect solution for this problem that is, again, so simple, I wonder why nobody else thought of it first. His solution is to build a very powerful 300 watt amplifier that strictly provides the huge current needed to drive the subwoofer. You can think of this amplifier as only half of an amplifier; or just the power portion of an amplifier. The release of this power is controlled by the signal that is provided by your power amp. Vandersteen’s amplifier needs a voltage to modulate its current output, and what better place to get that voltage than from your main power amp? This way, your power amplifier is directly responsible for the sonic character of the deep bass coming from the subwoofer because it provides the necessary voltage signal. This voltage signal contains the unique and characteristic sound of your main power amplifier and insures that that character is maintained in the sound of the subwoofer itself. The beauty of it is that your amplifier is only providing a voltage reference and no actual current, so it is not taxed with the burden of “driving” the subwoofer in any way. As a matter of fact, your amplifier doesn’t even know that the sub is connected to it. The 2Wq’s potential is almost unlimited given that it will ratchet up its performance as you improve your power amp. Remember that you always want your subwoofer to sound just like your power amp. No better, no worse. NO DIFFERENT!
After having spent time with the amazing Vandersteen Model 5A loudspeakers with their 400-watt powered, metal cone subwoofers, we were reminded of the sound we had with the awesome Audio Research Reference 600 mono power amps. With the Ref 600s there was a sense of effortlessness, openness and unrestricted dynamic freedom that we have only otherwise heard with live unamplified music. Listening to those monstrously powerful amps made us realize that all other systems sound compressed by comparison. Only when we heard the new Vandersteen Model 5As with their hugely powerful built-in subwoofers, did we again have a strikingly similar sonic experience. The reason is that the Model 5As provide a total of 800 high-quality watts, to which you have to remember to add the power of the amp we were using, the ARC VT-100, at 200 watts. This means we were listening to about 1000 total watts of amplifier power – not far from the 1200 total watts provided by the Ref 600s. With the Vandersteen subwoofer crossover and amplifier, you are able to get those hundreds of subwoofer watts to blend seamlessly and even take on the character of the ARC VT-100. It’s amazing! What’s even better is that the price of the system with the Model 5As and the VT-100 is under half the cost of the Ref 600s alone! Since this discovery, we have achieved the same kind of unbelievable dynamics and seamless blending with ProAc loudspeakers and twin Vandersteen 2Wq 300 watt powered subs. So, if you want the sound of Ref 600s but cannot afford them, buy a pair of Model 5As or your favorite pair of ProAcs plus a couple of 2Wq subwoofers and mate them with a VT100 and you’ll get surprisingly close. You can cut the cost even further by running a pair of Vandersteen 2Wq 300-watt subwoofers with your existing speakers. Or mate a pair of 2Wqs with your favorite ProAc. In any case, it is the magic of SUBWOOFERS that allows this to happen. It is for all of the above reasons that there is only one subwoofer in existence capable of integrating seamlessly into a high-end music system, allowing you to reap all of the benefits of having a subwoofer, with none of the drawbacks. And the Vandersteen 2Wq is the one. And just in case you think I am a biased source, our correspondent Blaine Peck (who, for all you know is also a biased source) recently wrote the following, with no discussion between us about the topic prior to his sending us his comments. Whether reproducing the plucked string of an acoustic bass or the sound of an analog synthesizer, the Vandersteen2Wq subwoofer is a seamless extension of any system. Nothing else need be added! With its internal 300-watt power amplifier, it is the perfect compliment to any sound system. Designed to take on the characteristics of your main stereo amplifier, the amp in the 2Wq will not sound foreign in your system. Also, through an extension of the Vandersteen design philosophy, a unique gradually sloping crossover system is implemented so you simply do not know where your main speakers stop and the 2Wq begins.
Now that your main speaker/amplifier combination need not concern themselves with those power demanding low frequencies, they are freed up to work in a more comfortable range. Yes, now what is coming from your main speakers will sound better than ever.
The 2Wq is not just another subwoofer. It consists of three 8″ floor-facing drivers, each with a massive motor. So why not a more typical single 12″ or 15″ design? Well frankly, the mass of a larger driver will not allow it to respond as quickly as the Vandersteen 8″ drivers to today’s demanding recordings. The 2Wq’s 8″ drivers are designed to handle the content but be “fleet of foot” at the same time. Concerned about where to put them? You need not worry. With the control of both its respective level and the “q” (how loose or tight the low end is) you have the flexibility to place them in a location that fits your living environment and not sacrifice performance. The simple beauty of this product will soon become an addition to your room.
So whether on orchestral music, hard rock or something in between, the Vandersteen 2Wq will exceed your expectations...."