Top notch speakers with their own sub

I have a pair of Infinity Prelude MTS complete with subs and towers. They serve me very well, don't require too much power because they have their own powered subs. The multiple components for upper base and mid range do have their advantage, giving a rather complete sound projection. This pair of Class A speakers certain have lived up to their pedigree, but the technology is about 10 years old. What would recommend for the current technology? I am looking for a pair of full size speakers that have their own powered sub.
Due to room modal issues I think you'll find most SOTA will recommend a separate sub that allows optimal placement. The main advance in the last 10 years has been the wider acceptance of active speakers in the market. Just as multiple drivers allow for complete and even sound projection at high SPL and low distortion, tailored individual amps paried with each driver can take things to another level.
Hmmm. Technology has not really changed much -- mostly, it's the testing & design equipment that have improved. Some drivers with new types of cone matl, but they're still cones Not knowing your musical & sonic tastes, I can only think you audition something from the same stable -- or similar ones.
I.e. the Genesis 5,3, the Vandy V, the Linkwitz Orion (that one is a fully active, reference-level design -- but you provide the amps)...
I'm not aware of any speakers that are constructed like that anymore. I bought the last of that breed, the ACI Talisman SE, a couple years ago. ACI was ceasing production as production costs were rising and they weren't sure about marketing it at a higher price point. I'm blessed with a good room that supports bass well and the Talismans have proven to be an excellent speaker. Their design places the woofer sections at the side of the cabinets like some Coincident and Audio Physics designs. Front firing drivers are symmetrical, so they can be placed woofers firing in or out depending on the room. After having the ability to tune each speakers bass output to taste and experienced the benefits, i'm relectant to go back to traditional all passive designs. You are correct that this approach allows for development of easy to drive speakers. No doubt Shadorne is right as well. Perhaps one thing that holds many back from acceptance of having completely self powered speakers is that many of us like to be able to try different amps and enjoy experimenting. When you buy self powered speakers, it's too simple, nothing to confound us!
I have 2 systems and also like speakers with built in powered woofer/sub units. Right now I am using Avantgarde Duo Omegas in one system and the Zu Presence in another. I have used several others over the years as well and these are my 2 favorites at this time. The Zu Presence is in a smaller room where the Duo's are in a dedicated stereo/home theater building which is much larger than where the Zu's are. The size of the room will come into play for which speakers are to be recommended,
Two designs: (1) Zu Definition 2s (that I have and like a lot) and Zu Presence (that I have not heard) and (2) Rethm Saadhana (also that I have not heard).
Listened to the new Wilson Sasha last week, which replaces the WATT/Puppy. Definitely one of the finest loudspeakers I've encountered, and people who have gotten to know me here know that I've not mentioned Wilson more than a couple of times previously on this site.
Tyler Acoustics PD80s can be outfitted with 1000 watt amps to drive the 2 15in woofers
I am referring to sub-woofers matching the remaining drivers. I am not talking about woofers. After several years enjoying that very deep base provided by the 2 subs which so seemingly align with other drivers to complete the sound projection, it's not easy to find "standard" speakers that can generously go that deep. I do not wish to go the route of standalone subs. Seemless sound transmission is a nightmare.

As to music taste, I do listen to a variety, from classical and acoustics, where texture and body are highly important, to that base-pounding rock music.

As to comment about Wilson Audio, the Infinity Prelude MTS in my opinion is somewhere between the Watt/Puppy and the MAXX 2.

Deqx powered systems from Salk, Selah, Lyngdorf and a few others are probably the current gen lineal descendants of the approach described by your Infinity Preludes. These are all actively crossed, multi-amped systems (the subwoofer amps are now BYO), and they now add digital room correction. Not precisely analogous to the Preludes, but these are probably the best for fit your "current technology" criterion that I know of.

I'd agree with the post which suggests separate subs to get the full-monty effect in specific rooms with various responses to low frequency sound waves. One of the finest effects I've heard in that respect has been the satellite sub system offered by Audiokinesis. This system offers seamless integration of subs in the most challenging of rooms, and the effect is astounding. The system is called the Planetarium System and is available in two forms.
The 3 BIG Montana Speakers, Master Reference, WAS2 and KAS2 all haver built in amplification for the subwoofers, check it out at

I certainly don't mind supplying amplifiers for various drivers including the subs. It's the seemless integration of the subs with other drivers to have coherent sound that I am worried about. Perhaps I'm wrong, but so far from the discussion, it comes across that the major speaker manufacturers don't get into system approach. In other word, you are on your own if you want to add sub-woofers into "standard" pair of speakers. This is for music listening, yet "standard" speakers don't have that abudance of a deep base sub-woofers can provide. Nor can you afford having the base coming from somewhere else but the primary speakers. At least with home theater, incoherance is more tolerable.
Nor can you afford having the base coming from somewhere else but the primary speakers. At least with home theater, incoherance is more tolerable.

I would take exception to your position. I can only touch on a few points that may explain; Sub level bass is non-directional and can be integrated, sometimes far more effectively, when produced from a point outside of the main speakers housing. The soundwaves at that level are much slower and longer than the others produced by your main speakers. I think room nodes have tremendous potential to wreak havoc with bass reproduction and in doing so have a detrimental affect on other parts of the range and generally in the natural presentation of the sound and timing. I'm by no means an expert...look to experts in the field for far more information than I could ever provide. From my own listening to various systems (my own, friends, and at shows) the best effects I've heard have come from satellite systems - that's not to say that speakers with integrated subs cannot do deep bass very well too - I have heard the PBN Montana's mentioned above by their representative (?) and they produced thunderous bass, practically to the point of distraction, but very effective. Rattle your fillings bass. I would remind you again that your room will have a profound effect on how that bass is delivered to your ears where you sit and listen. With the subs attached to the mains your only potential for adjustments are positioning of the (large) main speakers, and or room treatments (which may be a good idea regardless). Optimal position for the sub may not necessarily be the optimal position for the mains. The best (most natural) integration I've ever heard has been in Satellite systems with 2 or more subs that are separate from the mains and not always positioned near the mains. The Audiokinesis approach uses 4 subs placed asymmetrically around the room to cancel out room nodes. No association and I don't own Duke's speakers, but would certainly consider a set in the future.

The word is "bass", not "base", by the way.
I will admit not knowing much about bass equalization. All I know is that independent subs for home theater has this phase adjustment that does not work well at all. I can definitely hear where the bass comes from, despite the common claimed for non-directional effect. With just a brief look at Audiokinesis, I don't know the details. Can these 4 subs be integrated into any full size speakers? Or is this the case that you have to buy their main speakers as well?

The Prelude MTS back in their hay days costed $11K. I don't want to go beyond $15K. Of course the big boys in the speakers world do offer products in the $30K and up that easily blow away the Prelude MTS.
Can the MTS be surpassed, even today? Its technology is far from outdated, its form factor is supreme (it takes up less horizontal space than a monitor) it is relatively efficient (allowing wide latitude in choice of amps) and its high powered, RABOS system can eliminate the primary bass resonance and integrate into your room better than all but the most expensive subwoofers (and without digital eq!) Unless the rest of your system is beyond belief, you might be better served improving other components.
Thanks for the kind words, Jax2.

The distributed multisub concept is something I learned from Earl Geddes. Here's a brief synopsis in his words:

"The modal response of rooms at low frequencies causes large peaks and dips in the overall response of a system...

"By using multiple subs distributed around the room, low frequency response can be smoothed out. Placing multiple subs in multiple locations, each sub will excite the room’s modes in a different way. While the response of each would still have the anomalies suggested above, the total combined response is much smoother than any of the individual responses. In essence, they balance each other out, resulting in a much smoother overall response."

Todd Welti of Harmon International has published multiple technical papers on the subject, as well as a non-technical paper which is posted on Harmon's website. Welti did not investigate asymmetrical sub placement, but this paper is still excellent information for anyone interested in a high quality subwoofer system:

There are of course other issues, but a configuration that is conducive to relatively smooth in-room response is a good starting point.

One primary requirement for a distributed multisub system is a steep-slope lowpass filter (at least for those subs which are positioned away from the main speakers) so that you don't have subs reproducing lower midrange energy loud enough to betray their locations.

I will admit not knowing much about bass equalization. All I know is that independent subs for home theater has this phase adjustment that does not work well at all. I can definitely hear where the bass comes from, despite the common claimed for non-directional effect. With just a brief look at Audiokinesis, I don't know the details. Can these 4 subs be integrated into any full size speakers? Or is this the case that you have to buy their main speakers as well?

I hear you, Spatine. Setting up subs right can be tricky and I think most folks don't have the patience for it. The tendency is to set them up in whatever is the most convenient spot in the room, with the settings juiced so they are always audible and thus justify the purchase. I've found the better integration comes in setting up where you don't even notice them, but you are aware of their presence in those really deep moments of the music - that's exactly what they are for after all. Duke does sell his satellites separately (I think he calls them "The Swarm" when sold that way). I've only heard them with Duke's speakers so I could not comment as to how well or how easily they integrate with other speakers, but the principal he's based the design is very compelling and it sure sounded wonderful in the room at The Show that I heard them in. You can contact him through his website. He is a member of this forum as well. The other way to go would be with two conventional subs like JL Fathoms or Gothams (excellent subs), but you would have to have the patience to set them up properly or hire a local dealer or installer, or alternatively find a knowledgeable friend who might help you. If your subs are making themselves apparent in the way you describe then they likely are not set up right. If you want to skip the 'hassle' of setting up a sub, and prefer to just get something that is integrated into the mains, I think you can certainly find something that will make you happy among suggestions here, as well as other offerings out there. I would just reiterate that those solutions are not the best and most natural sounding in my own experience, when it comes to low bass and integrating a full range in a listening room. If your budget is $15K and you are looking at all-in-one full range speakers that do bass very well, my favorites have been Hansen's Prince which you just might find used for a bit above that price if you're very lucky. TAD Pioneer's Ref 1 was also outstanding in integrating a full range, as is Daedelus Ulysses speaker. None of these uses an integrated sub, but all have a very natural integration of their low-end. I've heard Wilson speakers on a number of occasions and they've never grabbed me as something I'd want to drop that kind of money on. Avalon's floorstanders also do a wonderful job of integrating the full range, and you may be able to find their excellent Indras in your price range used. Again, do check out Duke's Planetarium offerings and write to him for his own take on bass, subs, etc. He really does a great job and at fairly reasonable costs which I believe fall into your budget (I think the Planetarium Beta with his larger full-range speakers is around $10K). Duke's a great fellow too.

Good luck!

In theory, one great advantage of subs is that they can be placed where they work best (against the walls) - which is almost always far from where main speakers work best (away from the walls). You lose this option when the subs and mains share a cabinet.

When bass is generated out away from the walls in a room, the omnidirectional, long wavelength signals (i.e. bass) will reflect back off the walls and cause cancellation (nulls, or dips in response) at some particular frequencies and reinforcement (peaks) at others. Near wall placement reduces this bass effect because the strongest reflected signal is virtually coincident with the original signal. There is nearly uniform reinforcement evenly across the sub's entire output, and you can adjust (lower, relative to free space placement) the output level of the sub accordingly. To (virtually) eliminate the remaining peaks and nulls, you can EQ, or try Duke's "distributed" system which provides flexibility in using one (or more) sub's peaks to offset the other subs' dips.

BTW, the other approach is to find mains that are designed to work up against (or inside) a wall. Shadorne's soffetted system is one approach, Roy Allison's designs have offered a variation on the theme for a long time.

The Deqx idea I mentioned in my previous post is simply a "brute force" EQ solution. It allows the peaks and nulls to develop and beats them into submission with EQ. Audyssey and Velodyne (among others) also make EQ products for this purpose.

BTW, I can't localize the (carefully integrated) subs in my EQ'd system, even though they're far from the main speakers. Of course, YMMV.

Good Luck

I don’t know any of the mentioned brands of speakers in this topic, except for Wilson Audio. Venturing beyond the big brands does have the typical advantages and disadvantages we all know about. To do proper homework I really should look at the reverse role and take on what Lloydc said, that is if anybody wants to join the discussion and throw a monkey wrench. Is Prelude MTS really that outdated? Frankly speaking, edging out the well respected Watt/Puppy 8, which sure is current in technological development, is no easy task. Yet in my opinion the Prelude MTS has more details, fuller body, and less harsh a presentation. Granted that in the grand scale, mine is closer to the Watt/Puppy than the Maxx. An upgrade for my speakers without venturing out into the unknown (brands and sub equalization technology) would be getting the Wilson Maxx, or say the Gershman Black Swan. These are wonderful speakers from high to the very low frequency; however they are out of my price range.
They don't exist apart from speakers with dipole bass where you won't get enough output to cover the last octave for things like home theater and organ music (symphonic works at subjectively realistic levels or 90dBC rock/techno are fine with Linkwitz Orions in reasonable sized rooms like 2500 cubic feet or 13x19x8 but open on most of one wall to the entire 600 square foot floor).

With monopole woofers placement for mid+high frequencies is never going to be good for low (below the Schroeder frequency where the resonances no longer overlap thus imposing significant peaks and nulls on the bass response) frequencies because good low frequency placements are not symmetric.

With dipoles there's little (-20dB from the on-axis sound in practical examples) output towards the ceiling and along the dipole nulls 90 degrees off-axis horizontally. The speakers put audibly and measurably less energy into the room's height and width modes. You also get multiple bass sources stimulating the room length-wise with different phase although integrated dipole bass isn't going to be in an ideal location for this.

Linkwitz Orions, some of the Emerald Physics speakers, and the Audio Artistry line which are still made to order have dipole bass.

The better solution is probably designed to integrate with separate bass systems that are placed separately. Audio Kinesis, Lyngdorf, and Gedlee do that. NHT's Xd system did (there may be 10 pairs left).

Earl Geddes is applying custom transfer functions to each of the multiple sub-woofers which should work better than sending them the same signal. Duke could comment on what he's doing.
I read this thread with dropped jaw as no one has yet mentioned the finest speakers of this description. They being the time and phase coherent Vandersteen 5A.

MBL 116 and MBL 111

Avantgarde Duo's

YG Acoustics Kipod

Martin Logan Summit X

Someone up there mentioned "Vandy V".

In the Vandersteen line the top 4 -- Quatro, Quatro Wood, 5A, and the new 7 -- have integrated powered subwoofers with 11-band EQ and contour controls.

I'm more suprised no one mentioned the Definitive Technology Mythos STS and ST speakers. No bass EQ, though.
I listened to the Vandersteen/Ayre combination at a show and did enjoy the relaxed presentation. However this was a show with people constantly came by. So it wouldn't be fair if I conclude that Vandersteen 5A is about a trade off to Prelude MTS. Does anybody have studio comparison between Vandy 5A and Prelude MTS or Watt/Puppy 8?
Martykl writes:

>The Deqx idea I mentioned in my previous post is simply a "brute force" EQ solution. It allows the peaks and nulls to develop and beats them into submission with EQ. Audyssey and Velodyne (among others) also make EQ products for this purpose.

Nulls can't be fixed with equalization. With a 10dB NULL you need 10X the power or 3X the displacement you have at other frequencies. With 20dB it's 100X or 9X.

If you need 100W for sufficient bass head-room and aren't excursion limited, you'll need at least 2000W to overcome a 10dB null due to thermal compression. If you are excursion limited and are stacking woofers in the same location you'll need to triple their count.

Listener and/or speaker movement are the only reasonable solutions for nulls. I had to move my chair six inches to get decent bass in my current living room.

Nulls can be fixed with EQ - with some limitations. I have Eq'd to +12db with a pair of Velodyne SPLR 8 subs (1000wpc internal amps IIRC) and achieved excellent results. To muster +12db, I doubled down on the SPLR's internal EQ and added extra maximum EQ in my SMS sub controller. This approach IS DEFINITELY NOT recommended by Velodyne, but I did it anyway. Make no mistake, it my application.

I suspect that the real reason this approach can work well in music only systems is because my max EQ occured below 35hz where the pair of 8" drivers in the subs conked out. In actual use (playing music) there's little sustained signal there. OTOH, the EQ'd subs performed like a champ running test sweeps! I won't disagree with you that this approach lacks "elegance" and, in fact, could prove risky if amplification demands exceed the power available.

The real point I was making Re: DEQX powered speakers, however, is that straight EQ (including bass nulls) is the theory behind the design. I agree that you have correctly pointed out one significant limitation of the "brute force" approach.


It may work on certain soft music but an extra 12 db boost below 35 Hz is a gargantuan and scary extra amount for a poor subwoofer to put out. If you do this then I'd be extremely careful not to blow them up through excessive excursion or from burning up the voice coils.

Most 8 inch subwoofers are unlikely to play cleanly at 20 Hz or much below 35 Hz with anything more than 90 sb SPL output (which is barely audible). Below 35 Hz is really really tough territory for ANY subwoofer.

Another issure is ringing.....filters that boost will ring like a bell - as you exceed 6 db boost with a narrow high Q filter then the ringing will become progressively audible. Therefore it is best to use notch filters (sharp cuts) rather than any boost.

I can't recommend the approach (you state several good reasons not to), but I will say it worked really well for me. I filtered below 25hz, so the max boost was applied only to the narrow range between 25hz and 35hz. Test sweeps were run at app 95db and were quite loud - they exhibited no ill behavior that I could detect. Music reproduction was always pretty damn impressive to my ear, though I can't swear that there was ever much signal in the highly boosted frequency range under discussion here.

Equalizing peaks and nulls becomes more practical with a distributed multisub system. Before equalization the peaks are less peaky, the nulls are less nully, and there is less spatial variation (meaning that the response doesn't change as much from one location within the room to another). That being said, I'd still be hesitant about putting a lot of boost into a null unless you had plenty of headroom available - which apparently was the case in Marty's situation.
Hey Duke (or anyone else who cares to comment) - Is a flat response always necessarily an ideal target? I can understand addressing major dropouts at the sweet spot, certainly. When we go attend a concert the folks on the mixing board aren't getting a flat response from the room, are they? So if we're just talking about bringing the intent of the sound engineer / producer's work into our listening room with the least coloration/distortion, I expect that would lean towards the flat response, but could that also, for any reason, tend to sound any more or less engaging than a response that is more typical of most rooms (ie peaky)? Just curious what your take on that might be. Certainly if the Planetarium system speaks to this end it is a very convincing voice for that approach. I just wondered if that was the ultimate goal, or is that only a shade of something broader in what you are trying to achieve? What occurred to me as extraordinary about what you've achieved, at least in the room I heard, was a very natural and seamless integration of the low-end that did not call attention to itself as such, it was simply there at one end of the spectrum, yet was unmistakable as such. What I've objected to in some other approaches is that you become very aware of the low end to where it becomes distracting. I don't know whether this is due to overemphasis, room nodes, or some other imbalance. So is a flat response always the goal? Or?
Discussion on sub equalization and placement going on today is precisely the reason I hesitate straying from the mainstream speaker establishment. Now I have more plausible theory as to why major speaker manufacturers don't want to package non-integrated subs with their main speakers for music listening just yet. The technology is not sufficiently developed. Secondly, the idea of having 4 sub is quite intrusive, one way to get into major fight with your wife. Oh well, back to square one for me! But then the Prelude MTS is not bad at all really.
Jax2, in my opinion fairly flat in-room response is the goal in the bass region, and above the bass region, I prefer a gently downward-sloping curve. If I have to choose between too much and too little bass energy, I'll choose too little because that's less likely to be distracting.

Which brings up something else that most rooms do at low frequencies: Boundary reinforcement, sometimes called "room gain". Breifly, as we go down in frequency and the wavelengths become progressively longer relative to the distance to room boundaries, the first reflections become more in-phase rather than random-phase, so the net result is a roughly 3 dB per octave rise in bass energy as we go down below 100 Hz. This of course varies from room to room and with speaker positioning within a room, but since subs are usually placed close to the intersection of at least two room boundaries (on the floor and up against a wall) it's worth taking into account.

Without going off on a long semi-technical tangent, I'll just say that in my opinion a worthy "target curve" for a subwoofer system would be the approximate inverse of this 3-dB-per-octave typical room gain. If the subs are "flat" all by themselves, by the time room gain is factored in they will be bass-heavy. But if we have to err, imho best to err on the side of too much bass rolloff rather than not enough, so I'd rather have 6 dB per octave of rolloff (before room gain) below 100 Hz instead of none at all.


Killing the nodes bewteen 50hz and 150hz makes a HUGE difference IME. Getting flat in-room response in this range is really worth some effort and -IME- it will take some effort. I use bassbusters for the octave above 80hz - which works very well - and active PEQ below. In addition to much improved impact, weight, and "punch", the midrange sounds cleaner. Really flat response in this region also allows a more seamless integration of mains and subs - if you're crossing this high. My rule of thumb, cross where it's flat. The bass will seem to be a natural part of a seamless whole - it won't "stick out" at all. At least, not to me.

Below app 50hz, the whole excersize becomes a lot more subjective - IMHO. Again, weight is impacted as is, to my surprise, soundstaging. I'd heard people make this claim before, but I was doubtful - it wasn't intuitive. As it turns out, getting it right down low allows deep bass notes to "bloom" and expand in a way that feels natural and seems to define a larger space. To my ear, there's a decently broad band around truly "flat" response that achieves this result. I chose to extend flat in-room response to 25hz because it measured well and sounded great. Other folk's MMV.


BTW I currently use a pair of 12" Rythmik subs which require much less EQ than the 8" Velodynes.
Jax2 writes:
>Hey Duke (or anyone else who cares to comment) - Is a flat response always necessarily an ideal target?

The goal is flat on-axis response with a gradual directivity increase (or decrease in total power response). Your ears take a few cycles to pick up low frequencies so total power response comes into play more there although there seems to be some time domain component with steady-state measurements being an incomplete approximation.

Floyd Toole and Sean Olive at the Harmann Group have done studies on this with blind listening and their computer controlled speaker mover. The preferences hold regardless of listeners preferred musical genre, country of origin, and experience/training in critical listening.

>What I've objected to in some other approaches is that you become very aware of the low end to where it becomes distracting. I don't know whether this is due to overemphasis, room nodes, or some other imbalance.

It's the room and speaker+listener placement. Peaks really over-whelm the music. Placement too close to boundaries increases the whole bass spectrum. In-phase bass signals in the music add +3dB to total power response at high frequencies but +6dB at low enough frequencies. The room has up to 12dB/octave of gain below its fundamental resonance.

Reducing modal problems and room/boundary gain does a lot for natural bass which is like music as opposed to some fast, slow, tubby, or thin approximation that's noticeable and distracting.
In re-reading this thread I may have given something of a wrong impression re: EQ vs distributed subs. I love the idea of distributed subs and wouldn't be at all surprised to eventually own a set. I might very well still utilize room analysis/EQ, but mainly to help optimize placement (room analysis) and fine tune for +/- 1db or so for the 1/2 octave above and below my chosen x-over frequency. I suppose that some additional PEq might prove beneficial if any little anomolies survive the placement excercise, but I suspect that it would be minimal.


PS Duke - is there pricing info on the Swarm and Planetarium systems? I didn't see any on your web site. Not that I'm thinking.....
Spatine writes:
>Discussion on sub equalization and placement going on today is precisely the reason I hesitate straying from the mainstream speaker establishment. Now I have more plausible theory as to why major speaker manufacturers don't want to package non-integrated subs with their main speakers for music listening just yet. The technology is not sufficiently developed.

The technology is _fine_. Existing implementations are audibly, measurably, and theoretically superior in real rooms. "audiophile" exposure to cheap one-note sub-woofers and poor integration have created marketing prejudice against separate woofer enclosures. Spousal acceptance of additional boxes is an issue especially when placement constraints are taken into account. Some products call for more technical setup procedures and measurements for the maker to tailor transfer functions.

Mainstream speakers sound like speakers not live music due to inherently flawed physics which are addressed in alternative designs. You'll end up with a much more natural sound, better decor match (at the fringes it's small companies with made to order products. Figured woods/veneers, inlays, and finishes can be mixed and matched), and spend less money (you're mostly paying for parts and a furniture maker's time).

Speakers like the B&W Nautilus Prestige (acoustically small drivers+baffles with damped transmission line enclosures) and RAAL Requisite Eternity (uniform horizontal polar response, and I'd guess that the vertical response matches up well around the cross-over frequencies) take some steps to get there, although tighter uniform dispersion interacts less with the room. Bass needs separate enclosures and/or dipoles. Room specific bass filter functions are a good idea.

> Secondly, the idea of having 4 sub is quite intrusive, one way to get into major fight with your wife.

All but one location can use smaller woofers (they don't have to extend below the room's fundamental resonance, so they're not really sub-woofers) in smaller enclosures. AFAIK Earl Geddes is using 6th order band-pass boxes which can be 6dB more efficient for a given cabinet size and low frequency cut-off than a sealed design. In theory they ring more than a sealed or 4th order ported design, but the room dominates time domain behavior. In theory they have more group delay, but you need cycles of audio to pick up bass. Generalizing from small "sub-woofers" sold to the mass-market with a strong resonance to substitute for real bass doesn't apply to good ported designs and shouldn't be applicable to 6th order ones.

Didn't your Preludes utilize the RABOS system (IIRC a bass EQ scheme)?. Since you asked for current technological implementations, the answers naturally tended toward sat/sub variations and, eventually, EQ. The separate sub idea allows more placement flexibility. Additional placement flexibility isn't going to hurt things, though it's not 100% guaranteed to help, I suppose. Similarly, multiple subs offer even more placement flexibility. In the end, choose the approach which best suits your needs, but -in your place- I wouldn't be so quick to dismiss the potential advantages represented by some of the ideas here.
At the very least, there's some good food for thought.

Good Luck

Marty, I do appreciate the discussion. We are not talking and about your intention, and RABOS is definitely an EQ scheme of sort. The differences here are that I already know RABOS works and have been praised as an oddity in light of too many things that don't work. All I am saying is that hearing you guys somewhat disagreeing among yourselves doesn't help me build confidence in the unknown any.

Now what I didn't tell you yet is that even a few tens of dollars is not to be wasted in my life. So an upgrade from the Prelude MTS has to be truly an upgrade. Sort of better kinda thing is money not well spent. Why do I have a sense that in order to have that sufficiently spectacular improvement, thus justification to spend money, the order of improvement would have to be something in the scale of say ... the Wilson Maxx. Otherwise I am better off to sit still. Regardless of outcome, I do appreciate everybody's pitching in.
Given the investment you are prepared to make, and your reasonable expectations of a significant improvement, why don't you take the time to go to RMAF in the Fall and listen to some of the stuff suggested here as well as many other alternatives and see what's out there in your budget. You may find that your MTS are worth hanging onto, but you might also enjoy the trip and the show. I don't think you'll find a Wilson Maxx for $15K but you can always save your pennies.
"PS Duke - is there pricing info on the Swarm and Planetarium systems? I didn't see any on your web site. Not that I'm thinking....." - Martykl

Yeah my website is a bit out of date. I have a forum on that has more up to date info.

The two Planetarium systems are 6.5 grand and 10 grand, and the vented Swarm (as used in the Planetariums) is 2.5 grand including amp. I also have a sealed Swarm that's a bit less expensive.

Not that I'm holding my breath.....

You could probably roll your own without too much trouble, just be sure and use an amp that has a 4th order lowpass filter. Or better yet, add a couple more of whatever you're using now (Rhythmics??).

Now Earl Geddes would probably say you only need 3 subs, as long as you elevate one so that it's above the centerline of the room (closer to the ceiling than to the floor) so that your low frequency sources are scattered in all three dimensions. Neither Earl's approach nor my variation is particularly high in WAF, as Spatine obviously figured out!


Fair enough.

I didn't mean to be critical of your response, just suggesting that you might want to kick these facts around in your head a little more before reaching any conclusions - hence, the "food for thought". IMHO, this thread probably contains more useful info for achieving good sound than 99% of the material on A'gon. Figuring out how to utilize that info is your gig.

In a nutshell: optimal placement of multiple bass sources is a useful tool if it's available to you. Maybe it's not available (WAF or cost). EQ, whether from Infinity, Audyssey/SVS, Velodyne or others is also a useful tool, but others have -quite correctly- pointed out certain limitations to the approach (careful with nulls). Room analysis will make placement easier. Any thoughtful, properly implemented combo of these techniques is likely to improve in-room performance.

Take that FWIW.

Sanders Sound 10b or Innersounds.
This has been a very interesting discussion with a lot of useful information. Thanks to those who participated, and thank you, Spatine, for initiating it, even if it wasn't necessarily the direction you intended. Now I have to figure out a way to get an elevated subwoofer module past my wife! "It's just a little nook shelf, Love - don't you remember you asked for more built in storage?!" Hmmm, I don't think it's gonna' fly with her (pun not intended). Monofilament? Trap door in the ceiling?