Greg Smith

Past columns from The Entry Level are also available.

July 1997

Audio Concepts, Inc. Titan Subwoofer

Back at the beginning of the 80's, I was deeply wrapped up in mythology. To this day, I can still run that column when it comes up on Jeopardy! So when I started seeing prerelease information for this new film called Clash of the Titans in 1981, I was pretty excited. It was supposed to be an extravagant treatment of Greek mythology. Well, I don't know if you've actually seen this turkey of a film, but to say I was disappointed doesn't come close to my level of letdown when I actually watched the movie. Instead of a proper treatment, the plot pieced together bits and pieces of a bunch of different stories. While most of the film was loosely based on the adventures of Perseus, you got portions of other myths (like Bellerophon and Pegasus) mixed in badly. The whole mess was incoherent enough that I think I'd rather clean the Aegean stables than watch it again.

[ACI TITAN] Adding a subwoofer to an existing system can feel like a labor of Hercules (the original one, not that pansy on TV nowadays). Like that ill fated movie, it's all too easy to end up with two pieces that don't work well together even though they may be good separately. The Audio Concepts Titan is designed not to clash with your main speakers, and claims to be compatible with a wide spectrum of other equipment. While sold for $799 factory direct, it's stated to be comparable to subwoofers that sell for twice that price via retail. It seemed perfect for trying out with the Magnepan MMG speakers I've been using as mains since moving into my new apartment.

Subwoofer 101

Discussing the technical details behind subwoofer selection in the context of this review makes for some interesting circular references. When I was originally getting into speaker building during the early 90's, I picked up catalogs from all the appropriate companies I knew of to get a feel for what was available. The only place I ended up ordering anything from in that first round of looking around was Audio Concepts. At the time, they offered a couple of small books on speaker design, including one that was specifically targeted at subwoofers. What made these unique was that they featured recommended configurations for the very good drivers that ACI sold, along with suggestions for utilizing premium units from companies like Dynaudio and Focal. The other material I had available was either theoretical or featured sample designs implemented with very inexpensive drivers, typically Radio Shack and the like. Even more useful in the long run were the multitude of suggestions offered on design philosophy and amateur project scope, drawn from ACI chief Mike Dzurko's years of experience. The slim 25 pages on subwoofer use and construction obviously reflected views gathered over decades of work. ACI recently celebrated their 20th anniversary; even if the name isn't familiar to you, you can be assured that they've got an excellent reputation for selling affordable products direct.

When I sat down to write this review, I scribbled some notes on things I wanted to mention and started to get things organized. As part of that, I went back to my much referenced original material from ACI, only to find that my current thinking on the subject owes more than I had realized to that early reading--quite a bit of what I was going to mention is covered so well by Dzurko's explanations that any attempt I made to discuss the subject would be redundant. Accordingly, I'll send you to the same source first. If you're not familiar with subwoofers, or aren't familiar with interpreting the technical statistics that go along with them, head over and read the Subwoofer Primer that's on Audio Concepts' home page (a visit to the Audio Glossary there might also be in order).

Why the emphasis on technical material? Out of all the components a typical high-end audio system might include, the subwoofer is by far the one that you can gather the most useful information about without needing to listen to it. Trade-offs in size, bass extension, maximum volume, and price can be scoped out without hearing a note. There are so many units out there, with a wide array of potential applications, that narrowing the field considerably is in order before you start auditioning them. Some physical limitations come into play here. You need to move a lot of air to get deep bass response. Dropping down an octave in response requires four times as much output to maintain the same level.

The three most important figures of merit describing a woofer are the resonant frequency, the woofer Q, and the volume of air needed to match the compliance of the woofer suspension. Describing each of these is a bit beyond the scope of what I want to get into here, but the main thing to understand is that by knowing all three you can predict with reasonable accuracy what results you'll get from putting that woofer in a given box. When you start playing with the equations relating all these figures, a few patterns emerge. First, some woofers are better suited for sealed boxes, and others are more useful for ported ones (a small number can be used well in either application). Second, there is a range of "reasonable" box sizes that go along with a given woofer. If you start going toward the small portion of the range, low frequency extension drops and you start getting nasty peaks in the output. Make the box big, and it goes deeper, but beyond a point you don't get any more useful drop but the output volume starts going down. There are even more factors to consider with ported designs. Generally, though, given a woofer, there's a fairly narrow range of box size it will work well with, resulting in a good trade-off between low frequency roll-off, flat response, and output level. Power handling is also affected in the mix as well.

Let's look at some samples. Your typical 8" woofer has around 1" of it's outside edge taken up with driver metal, surround, and other parts not actually radiating sound. The cone itself is about 7" in diameter, which (pi r squared) makes about 38 square inches. There really isn't quite that much, because the dust cap in the center takes up some space, but for the gross comparison we'll be doing here that's small enough to ignore. For a good unit, the resonant frequency of the woofer would be closer to 30Hz. A reasonable sealed box would be around 1 cubic foot, and you'll end up with a -3dB drop-off point around 60 Hz. If you used a port, and made the box way bigger (closer to 2 cubic feet), you could probably get this down to below 40Hz.

Specific woofers would vary, but this gives us something for comparison. Now, 60Hz is not nearly deep enough out of that sealed box, right? If we wanted to get 30Hz instead, that's an octave drop, requiring four times the output. First reaction: get a bigger woofer, right? Your typical 10" woofer has a cone area of around 63 square inches. That's only twice as much. What about 12"? That gets up to 95 sq. in, which still isn't even close (the box size here will be around 2 cu ft). You can play around with the numbers all you want, but the fact remains that even the best 12" woofers out there, in a huge sealed box, are very difficult to get flat response out of at 30Hz. If you go ported instead, that helps. You could very well end up with response down to 25Hz, or even lower. Recognize that it may take an enormous box to pull that off in, though; 4 cu ft is not out of the question.

Doesn't sound good, does it? And we haven't even gotten into qualitative measures yet. The Q figure I glossed over before is one to consider. Q is a ratio that gives an idea how well controlled the woofer is, with low numbers being better damped. There are several Q figures for the woofer, and also one for the woofer/box combination, which is what we'll compare next. A sealed box will typically have a Q of 0.5 to 1.5, with 0.5 being "tight" and 1.5 being "boomy". Anything over 1 is probably too much; 0.707 is typical goal for a good balance of enclosure size vs. bass accuracy. These figures don't quite apply the same way to ported enclosures, where bass accuracy is more difficult to put a quantitative measure on.

There's more to the whole sealed vs. ported decision than the factors mentioned so far. One important factor is that sealed boxes roll off at the bottom at a rate of 12dB/octave, while ported ones roll off at 24dB/octave. This means that given a sealed box and ported box, both of which are 3dB down at 40Hz, the sealed box drops to -15dB at 20Hz while the ported one will be -27dB. The extra output from the port also results in losing low bass faster. No free lunch here. Because of the way this works, ported boxes are also far more susceptible to problems with overextension. If you drive a sealed box with frequencies far below what it's capable of reproducing, you'll waste power but the potential for woofer damage is minimal. Ported boxes fed frequencies well below what they're capable of handling will cause the woofer to overextend, making all sorts of nasty clacking sounds as you hit the limits of the suspension and possibly burning the voice coil out. Overall, then, compared with sealed boxes, ported ones usually have a lower -3dB point. They also don't give as much output below that point, there's a much greater potential for harm if pushed very low, and often a larger enclosure is needed. You'll really need to worry about all this if you're playing vinyl, because the significant low-frequency garbage on that medium that can easily destroy systems that can't handle frequencies well below their normal output.

The ACI Titan uses a sealed box, because the design goals lean more toward getting the tightest and best controlled bass rather than maximum output. By itself, the 12" woofer in this configuration is tuned to be -3dB at 40Hz, with a Q of 1. Not all that great for a subwoofer, you might think; it's not deep enough and could be perceived to be too boomy. But there's more to the design than just those two pieces.

EQ to the Rescue

So you've got a woofer in a box, and it doesn't go as deep as you'd like it to. What's there to do about it? Luckily, there are some options. The usual route taken is to add some sort of electronics before the subwoofer amplifier. If your response is dropping at 12 or 24dB/octave, then boosting output at the same rate will result in flat response, right? That's the idea, anyway. In order to pull this off, you'll first need a woofer that can be pushed with a lot of power and produce useful output. And we're talking about a lot of power here. Remember, output needs to go up by a factor of four with every octave drop. Let's drop back to our examples from before. Let's say we take our sample 8" woofer that's -3db@60Hz and want it to stay flat down to 30Hz. If typical power into the woofer is 50W, that means we'll need 200W to do that. There aren't many 8" woofers that can handle 200W of power and do anything useful with it, especially at very low frequencies. Typically you'll find somewhere between 50W and 300W of amplifier power driving a powered subwoofer. There are some exceptions. Most notable is Bob Carver's Sunfire subwoofer, which claims to pack 2700W of amplification into a little box, which allows deep output from small woofers.

The amplifier inside the Titan is rated at 250W. The electronic equalization results in a system that's -3dB at 20Hz, with a Q of 0.6. Very deep, very tight. And considering the relatively large surface area of the cone, this much power provides substantial output even at 20Hz.

One additional complication is distortion. Cones driven with lots of power, especially below their natural output range, will distort. No matter how good the technology behind the cone may be, it's not a question of if it will distort, it's how much distortion you're getting that you need to consider. There are a few approaches for controlling distortion and keeping your woofer from frying under the strain of too much power. The usual way is to simply cut back on the power above a certain threshold. One technique installs a motion accelerometer sensor on the cone and what's referred to as a servo feedback mechanism to keep cone problems in check. The most popular models utilizing this technique are from Velodyne. The only concern is that dropping output when the limits approach means you're going to get a mismatch in output between your main speakers and your subwoofer. ACI utilizes a unique approach for output limiting. There's an high-pass filter built into the crossover and amplifier circuitry that normally runs at 20Hz. This keeps low-frequency rumble from causing problems or wasting power, and is especially helpful for those playing vinyl. As the limits of the amplifier (which is matched to the limits of the speaker) are approached, the frequency of this filter goes up. So if you've normally got the unit configured so that it's running from 20Hz-80Hz, a very high output situation might result in only getting 25Hz-80Hz or 30Hz-80Hz. This ensures that you'll never get an output discontinuity with your main speakers around the crossover point, because higher frequency output never compresses. And since the bottom frequencies are the ones using the most power, this approach is very likely to solve output problems without cutting too much off. As a bonus, it's almost impossible to damage the woofer with an arrangement like this; you'd really have to go out of your way to destroy a Titan.

Hertz so good

We've now followed along a good bit of detail about whether the Titan is going to work well or not, and note that I haven't even mentioned listening to it yet! That's how good subwoofer selection should work. It's a complicated enough part of the market that unless you check around and do some reading about the available designs, it will be seriously tough to find something that's likely to work for you. Decide how deep the bass needs to go, how large of an enclosure you're willing to settle for, and try to estimate how much power you'll need given those answers.

In my case, I was looking for something that was dead flat to at least 20Hz. My own appreciation for deep bass was fueled by purchasing an early pair of Hsu Research HRSW10 subwoofers in 1993. Those featured a pair of cylindrical enclosures with unusually high output 10" woofers and a ported enclosure. Electronic EQ left them -3dB at 20Hz with usable output down to 14Hz, although they go nuts if driven with tones much lower than that. These are actually still in great condition; unfortunately, with two good sized cylinders, there is not enough space in my listening room to house them comfortably. Plus, the fact that they are passive subwoofers means that they need a separate amplifier and crossover, more things that I'm hard pressed to house in my relatively cramped confines.

The Titan has a footprint of 13"x15", which means you don't lose much floor space. At 26" high, it's designed to look like an end table. Despite the appearance, be careful of what you put on top of it--the amount of bass you get out of a subwoofer like this will easily bounce things off the surface. I feel the Titan is a very attractive unit, more so than most speakers in this price range. Usually, those who actually have some semblance of decorating taste offer a disgusted look when entering my listening room, with its monolith-like Magnepans ("have you been listening to Also Sprach Zarathustra too much again?") and acoustic foam tiling portions of the wall. The ACI subwoofer usually elicited a "that looks nice, what is it?" kind of response, as opposed to the "what the hell is that?" I usually receive when new equipment arrives. The standard finish is clear lacquered oak, with black lacquered oak and clear lacquered cherry also being no-charge options. Special order finishes are available as well.

Making a connection

There is quite a bit of crossover and filter circuitry inside a Titan, and several pieces that add new capabilities are available. As a summary, the Titan includes:

  1. Electronic low-pass crossover filter operating between 50 and 150Hz before the internal amplifier. There's a potentiometer to control the frequency. This filter starts at 12dB/octave and increases to 24dB/octave at higher frequencies.
  2. Protection hi-pass filter. This 18dB/octave filter normally is fixed at 20Hz, and serves to protect the subwoofer from frequencies lower than it can reproduce. The frequency of this filter is increased automatically to protect the woofer from being overdriven.
  3. Speaker-level to line-level adapter. A pair of speaker cable style wires are terminated with an internal resistor and an RCA jack. This lets you tap off your main power amplifier to obtain a subwoofer signal.
  4. (Optional) In-line filter. With a female RCA jack at one end and a male at the other, this filter also includes a small crossover network. The two resistors and capacitor inside are designed to be used between a preamp and a power amp to roll-off bass below 85-90Hz at 6dB/octave, without being particularly sensitive to amplifier input impedance.

There are three RCA input jacks on the Titan, which means you can drive it in mono, stereo, or with all three front channels in a home theater. These are line-level inputs that you can connect directly to a preamp subwoofer output, should you have such an option available to you. If not, there is an included set of speaker level to line-level adapters that consist of two short lengths of wire with an embedded resistor, terminated by a male RCA jack. You would connect these in parallel with your speaker outputs at the amplifier output. The high input impedance means the Titan crossover won't draw any significant power away from the amplifier. Note that the few inches of cable provided is not going to be enough to run out to the Titan from your amp. And the male connector means you'll probably need a female/female RCA adapter to connect another cable. The instructions in the manual show a female jack for the converter cable, which isn't what you get anymore in current production. Since the Rotel RSP-960 preamp I was using has a mono subwoofer output, I utilized that to drive the subwoofer amplifier. This is generally a stronger, more predictable signal than what you get from tapping off of the speaker level amplifier output. Fellow SoundStage! troublemaker Doug Blackburn doesn't quite agree with me on this issue. He makes a case for using the speaker level converters because that makes the character of the subwoofer's bass match your main speakers. So if you've got a tube power amplifier for your main speakers, the subwoofer will have more of a tube-like character in the bass if the subwoofer signal is tapped off after the tube amp. That makes for a better match between main speakers and subwoofer. I personally would label this interaction with power amplifier characteristics a problem rather than a solution, but I can see Doug's point as being valid for some circumstances. If you can, try them both and see what works better for you.

The woofer in the Titan points downward. This requires a woofer suspension designed for that purpose, otherwise the cone sags under the pull of gravity in short order (this is still a long-term concern no matter what woofer you use). The advantage of downward firing is that the configuration acts as a low-pass filter, cutting out some of the high frequencies. This is obvious if you think about it; if you turn your speakers face-down, you'll still hear the bass even though the treble gets lost in the process. There are four screws with short cylinders below the woofer that elevate the main portion of the cabinet a few inches off the base. While you can get your fingers through this opening and touch the woofer cone if you really want to, in most cases the restricted access means the woofer is safe from physical harm, and doesn't need a grill.

The effective frequency range of the subwoofer starts at 20Hz. The upper end of the response depends on how you set the crossover potentiometer. The maximum frequency you could use is about 150Hz; a downward facing design like this one certainly shouldn't be used any higher than that. Figuring out what frequency to cross from your main speakers to the Titan is not necessarily a simple task. The first thing to consider is how deep your mains go by themselves. You certainly shouldn't pick a frequency lower than that, otherwise you'll have a hole in response between main and sub. Pick a frequency that's too high, and you'll end up with overlapping response that will give an inaccurate emphasis on some frequencies.

The other thing to consider is whether you're going to remove some of the bass from your main speakers. Often, this will let them play louder, use less power, and/or sound less distorted. ACI sells in-line filters that go between your preamp and power amplifier to remove low frequencies ($39/pair, $29/pair if ordered with the sub). These feature a little crossover network in them that is -3dB around 85-90Hz, depending on how it interacts with the rest of your system. If you use these, you won't be able to tap off the power amplifier output to get a signal for the Titan--the low bass will already be removed by the filter before it gets to the amplifier. The other option is to just get a non-polarized capacitor (polarized ones will explode in this application) for each channel and put that in series with the speaker outputs. Around 200uF will roll off frequencies below 100Hz at 6dB/octave. The main problem with that is that you really put yourself at the mercy of your speaker's impedance; if it varies significantly in the area you're trying to cross over at, the effectiveness of the filter drops dramatically. Also, this isn't useful at lowering the power needed for driving your main speakers. ACI's filter is more stable (impedance wise) than a simple cap, and better at lowering power requirements.

Some examples should make all this a little clearer. Originally I was trying to match up the Hsu Research HRSW10 subwoofers with my various main speakers. These use a passive crossover and operate up to 40Hz. At the time I bought them, I was using them with my Klipsch Forte II speakers, which are rated -3dB at 32Hz. Combining the two resulted in a peak in response between 32Hz and 40Hz, where the sum of the main and sub outputs wasn't flat. When I switched to the Magnepan MMG speakers, those are -3dB at 50Hz. Combining those with the Hsu speakers gave too little output between 40Hz and 50Hz. I could have gotten a new crossover and fixed all this, but the Hsu units were too big for my new pad, anyway. They are now happily mated to my father's Boston Acoustics T1030 speakers, whose -3dB at 40Hz bass output are a perfect match with how my Hsu subwoofers are configured.

Switching to the Titan gave me much more flexibility. It incorporates a variable crossover that's continuously adjustable between 50Hz and 150Hz. I started with the Klipsch speakers. There's obviously way too much deep bass output from those mains to combine them with the Titan easily. Accordingly, I used a pair of the in-line filters to roll off their output below around 85Hz. This worked OK, but I was never happy with it. I like the way the Klipsch woofers sound from 40-85Hz, working in stereo, and switching to a mono subwoofer for that range didn't improve things over what I already had there. I wasn't expecting this combination to work well, anyway, so I moved on to a more useful configuration.

The Magnepan MMGs require quite a bit of power compared with most other speakers, and you never get the feeling that you can turn them up very loud. Dropping some of the low bass range out of their output should improve both of those characteristics, so I started with the in-line filters in place before the amplifier used for them. While removing some bass from the Magnepans was successful in improving peak output a bit and lowering distortion, it still didn't sound right. One of the things I really like about these Maggies is how their bass sounds, even if it doesn't go very deep. While the Titan sounded good, I still preferred the way bass in the 50-85Hz region sounded on the MMGs.

Let me clarify that a bit. I'm a fan of keeping subwoofer crossover frequencies as low as possible. As you move up to higher frequencies, getting the transition smooth becomes more difficult. The home theater crowd seems to have standardized on around 80Hz as the spot for this sort of thing. As far as I'm concerned, that's the upper limit I find acceptable. For one, going higher than 80Hz puts you in a position where you can lose stereo information in the bass. Even more problematic in my mind is that it's much easier to notice discontinuities above that frequency; your ear is more sensitive to picking them up. So when I say that I prefer to push the crossover down to below 60Hz whenever adding a sub to a system, that's isn't meant to be a criticism of how the Titan handles higher frequencies. I do that with every subwoofer, because I think it works better that way. This line of discussion leads to me ranting about why I'm not fond of several popular budget speakers, like the NHT SuperZero and the Radio Shack LX-5, where you have no choice but use a higher crossover point. I'll save you from that for the moment.

Anyway, out went the in-line filters; all the speakers I was using were a bit too full-range for them to be helpful. Fortunately, I could configure the ACI subwoofer to operate only up to 50Hz. Since this perfectly matched the bottom frequency the MMGs were playing, there shouldn't be any hole or peak around the crossover frequency. Initial listening proved this out; after fiddling with the level adjustment to match sensitivity, things sounded pretty good. Not perfect yet, though; getting the crossover and level approximately right so that the main speakers and subwoofer integrate together well is only the first of the trials you'll face when trying to add deep bass to your system.

While I was trying all this out, I was also breaking the woofers in. Anyone who says break-in is a myth needs to spend some time listening to what happens to the bass of a subwoofer with a rubber surround on the driver during its first few months of life. These take forever to hit peak performance. Especially when the woofer is capable of high output; you can't just play some wimpy break-in tones at low volumes while you're away for a few days. You've got to push that cone to get the rubber stretched out properly. I'll warn you: as delivered, the Titan is not an especially impressive unit. I was kind of disappointed at the sound initially. It took a full weekend of bass abuse before it started sounding like I expected. It easily took 100 hours before I thought it had reached full potential. ACI says 40 to 60 hours for break-in, and they are not kidding. Although they offer a 15 day money-back guarantee if you're not happy with their speakers, I think it would be real hard to break this subwoofer in and get it properly configured with your system in that time (assuming you actually have some sort of life beyond your audio pursuits, which I'm told some people do). You may have to make a judgment call on faith that things will improve if you can't muster enough time during the trail period to break the Titan in and get it matched to your system.

Get a room!

To say that bass frequencies are affected by your room is like saying the Grateful Dead have released a few albums; while strictly true, it doesn't really communicate the magnitude of what you're dealing with. Room effects can turn the best subwoofer into a bloated one-note beast. While the details involved are a bit beyond this review, I'll generalize with a few statements that are usually true:

Even if your room has potential, placement of the subwoofer(s) is still critical. Theories on what's best vary. What is certainly true is that the closer your speakers are to the room boundaries, the more audible output you'll get from them. This is most extreme at the corners, where bass output is greatest. Move any of your speakers, including a subwoofer, around the room, and bass level wanders all over the place. Further complicating matters is the fact that certainly frequencies get emphasized and others depressed due to the way bass waves flood a room. While it's possible to predict these effects (called room modes) mathematically if you get some figures about the room and speakers involved and chug through some equations (preferably with a computer), in the real world it's extremely difficult to gather enough information about everything involved to actually pull this off. At best, work like that only is useful for offering rough suggestions about what you should try.

One idea you'll often see bandied around is called the "theory of superposition". The idea here is that you can reverse the positions of yourself and a subwoofer without changing the way the bass sounds. What you do, then, is position the subwoofer at your usual listening position, then wander the room until you find something that sounds good. Mark the spot, put the sub there, and you're done. Great, right? That lets you move around, instead of needing to drag some heavy object (as subwoofers invariably are). Well, it's a reasonable start, but don't go thinking that's going to solve all your problems. I think this theory is a sham, actually. Getting the bass on the sub to sound good is the least of your problems. The really hard part is finding the position that gives the smoothest transition between the sub and your main speakers. You can't do that unless you're sitting at your normal position, of course; go wandering the room, and you can't hear the regular speakers correctly anymore. Plus, my listening position usually consists of a nice comfy couch, which is even more trouble to drag around than the subwoofer is; since I'd have to move it out of the way to put the sub there, this isn't a useful option in any case.

I've never found a method more effective than trying a bunch of places and listening for what sounds best. Positions you certainly want to try include all the corners, a few spots along the walls, and a number of spots around your main speakers. I've always gotten best results getting everything to integrate together with the sub in between the pair of main speakers, which happily avoids some of the reflection issues you run into in other spots (especially with dipolar speakers like the Magnepans). After a month of dragging around the Titan (I kid you not, it took that long), I ended up with it about 1/3 of the way between the MMGs, closer to the left one. Totally dependent of the room itself, of course; your mileage will vary.

There's more than just a quick listen required at every stop on your subwoofer listening tour. While you should be able to tell from that whether the sound reasonably good, in order to properly compare things you'll need to rebalance the level. There's another control to play with, the phase switch. Since it's quite possible that a subwoofer can be out-of-phase with the main speakers in some positions, ACI provides a switch that inverts the polarity of the output. This makes a 180 degree phase shift. While a finer control than that is provided on some subwoofers, and is a desirable feature, 180 degrees is probably enough control over phase for a typical setup. Whenever trying to match subwoofer and mains, you should try both settings of the phase control whenever you change crossover frequency, level, or position.

Sounds like a lot of work, doesn't it? Drag the subwoofer to at least a dozen positions, and adjust level and phase at each one to get the best match with the other speakers. Listen for a bit to make sure there's not something obviously wrong; if not, listen to at least an album or two of bass-laden music to see if you like it better or worse than the previous position. You'll probably have to visit some positions multiple times before you settle on what you like best. Budget at least two days of time to do this right, and not successive ones; spend at least a week listening at whatever position you liked best at the end of each day to get a feel for the strengths or weaknesses of the subwoofer sound at that resting place. I suggest listening to "Stop dragging my heart around" if the moving starts becoming too much. While the 70 pound Titan is no joy to move, its bottom is smooth enough that you can drag it easily over carpeted or wooden floors without damaging either the sub or the floor.

Things that go thump in the night

Have you picked up the major flaw in this approach? It's easy--how are you supposed to know what things are supposed to sound like if you've never heard deep bass reproduced this well? As a side issue, there's no easy way to tell how subwoofer worthy the music you're listening to is; unless you find something that has some output in the crossover region between main and sub, along with something good for the sub to munch on, you'll never know if your subwoofer is working properly.

For the first part, it's tough to give recommendations. You can try and find a dealer or friend who has already gone through subwoofer alignment boot camp and try to match what they play. On the flip side, you can get someone else to help you align things as a start, and see if you want to change anything after you've got more experience in low bass land.

As for what to listen to, you'll probably spend months going through your collection rediscovering your music with a new dimension. I'll mention what I use for subwoofer abuse duty. For initial alignment and crossover setting, I've settled on the title track from Ray Obideo: Iguana. This features a bass guitar part that not only goes very low, it wanders up and down the low frequency scale with a constant volume. This makes it fairly obvious when bass transitions aren't correctly aligned. When I've got things almost right and am ready for fine-tuning, I pull out Toy Matinee. This features the most killer bass guitar I've ever heard (bass god Guy Pratt was the Guy playing for Pink Floyd on their last tour), and the tight interweaving between it and the kick drum is a brutal test for subwoofer resolution. Next up is David Baerwald's Triage, which has incredible transients along with sub-30Hz output. These are two of my favorite albums, by the way, in addition to being woofer demolishing monsters. After everything else seems good, the final hurdle for any subwoofer is Mike Oldfield's Songs of Distant Earth. With this CD, the subwoofer often becomes a secondary concern. You'll be finding loose door frames, poorly constructed windows, and objects that weren't firmly attached to their shelves. My last listen to this one with the Titan hooked up revealed that, if sufficiently provoked, the ceiling of my listening room can be made to rattle very loudly and sound as if it were going to collapse on my head. The album has that kind of bass on it. Any of these three are far more difficult to reproduce than the oft-repeated staples of rock music with deep bass, i.e. Pink Floyd's Dark Side of the Moon.

One audiophile favorite for bass is the Dorian recording of Jean Guillou playing Mussgorsky's Pictures at an Exhibition (DOR-90117). Tracks like Gnomus feature a pipe organ with solid output down to 16Hz. Even if you're not a fan of that piece, this one is worth having just as a demo piece. Like everything else I threw at it, the ACI Titan didn't skip a beat playing any of these tracks under normal conditions.

There were some limits, though. One thing I found annoying when cranking the volume up some was this odd distortion that sounded as if the woofer has some sort of air limiter on it; I'm used to hearing sounds like this from ported devices that can't push enough air through their port. I threw some earplugs in and determined that the airflow around the woofer, out of the slot, seemed to a problem. I pulled the bottom section (the plate and feet) off, and sure enough the problem went away when playing the sub on its side. This obviously wasn't a woofer extension or power concern; it seemed the slot just wasn't quite big enough for some of the notes I was trying to push through it. Happily, I came across an easy fix. ACI sells a variety of spikes that fit into threaded holes on the bottom of the Titan cabinet. Usually, the idea is that a spike allows the enclosure to better couple to the floor, which makes for better bass. My Titan was supplied with the optional Extra Points, which sell for $14.50 per the four needed. When I got around to using them, the output was clean to a much higher output level. The extra space under the bottom appears to improve air circulation around the slot. Considering that, in addition, all the bass sounded better with them attached, I'd highly recommend that anyone using a Titan use one of their spikes with it.

This does add yet another dimension to the whole subwoofer tuning process, though. Putting the sub on the spikes changed the sound enough that I needed to tweak the level and reverse the phase to get the best match afterward. You might have to make a similar adjustment. The sound was different enough that you'd probably need to do all your position change comparisons with the spikes on to get the optimal results. It's not too much a compromise to only do this step only on the best few positions found without the spikes on.

How does the Titan do when competing with the Hsu HRSW10 subs I've been using? That's a tough call to make. I find that stereo subwoofers are far easier to get good results from. There's more flexibility trying to get smooth bass response from two subwoofer sources than it is a single source with twice the output. When put in a large (over 20'x30') listening room with concrete floors, I can easily get plenty of smooth output from the Hsu subwoofers at low frequencies. A single Titan just couldn't keep up with that pair in output, and I never could find a good place to make it integrate with the main speakers quite right. To keep things in perspective, the HRSW10 units costs $750/pair in 1991 dollars just for the speakers--no amplifier or electronic crossover included, and the cabinets don't look very nice. The Titan has so much output into my normal listening room (10"x16" with wooden floors) that I have to open a door to keep the room from overloading when playing recordings that dig deep. A single Titan will move enough air to satisfy most reasonably sized rooms, and adding another is always an option.

I'm serious when I say overloading is a problem in my normal-sized room. I don't think most people realize how serious output at 20Hz will shake the hell out of everything they own. You can easily spend days (months if your house is old enough) just trying to fix all the structural problems a subwoofer like the Titan will reveal. Those with reasonably sized rooms might be better served by getting something that isn't quite so dead flat at very low frequencies. A subwoofer that only goes down to something more reasonable, like 30Hz, can get you almost all of the music without causing the "look what just fell off the shelf and broke" kind of damage a more serious unit will cause. You've been warned.

The Cabinet of Dr. Dzurko

For the ambitious do-it-yourself audiophile, it's possible to order a Titan Parts Kit that comes without the cabinet for $529. You'll save $270, which frankly I feel is a fair price to pay for the well constructed and very attractive enclosure ACI supplies That's certainly a personal value judgment; if you have good woodworking skills, you might be able to do better.

The stock cabinet is made out of 3/4" medium-density fiberboard (MDF), widely recognized as the best enclosure material at the inexpensive end of the market. The outside wood veneer looks good and is well-applied. The inside is lightly stuffed with poly-fill material. This enclosure is fairly rigid and well damped, but it's certainly possible to do better. It will probably end up costing you more than $270 to do so, however. This is a valid option some might consider; it's possible to construct a Titan cabinet with better internal bracing, more extensive damping on the walls, or any number of other improvements, if you're willing to put the time and money into it, and know how to recalculate the volume to account for what you did. This would not be a good starter project for learning how to build speakers, but it is possible to trade-off some of your time to save some money or to attempt to get a better result than the regular enclosure.

While we're talking about the inside, I'll mention that the panel housing the crossover and input jacks is glued to the cabinet, in addition to being screwed on, making it difficult to remove and examine. You do get a better air-tight seal that way, but it makes fooling with the circuitry harder, which may very well be an intentional move on ACI's part. The potentiometers used for crossover and level control are all precision parts from Alps. There's a big toroidal transformer inside powering the amplifier, with high quality parts used throughout. The tweaker could potentially experiment with upgrades here, but I suspect there's little to be gained in tweaking a subwoofer amplifier that's already well implemented. The woofer is connected to the amplifier with 18 gauge wire that's soldered directly to its input terminals. While it's not experimenter friendly, the components inside the box should last a long time without anything working lose. An occasional, careful tightening of the screws holding the woofer is about the only mechanical adjustment I might suggest for using a Titan in the long term. Frequent furniture polishing is also in order to keep the outside looking nice and shiny.

20 to 20K for 1.3K

There are so many subwoofers on the market, it would be silly to try and say whether a particular unit is "recommended" without a number of qualifications on applications it would be suitable for. A single Titan is excellent for medium-output situations where you want bass that goes all the way down to 20Hz without any mercy. Add more if you want high volumes in a large space. At $799 direct from the factory, the Titan is a bargain. Subwoofers with comparable retail prices aren't nearly as impressive, but that's one of the things you get when you cut distributors and dealers out. Whether you're the kind of buyer who should go without dealer guidance for buying a subwoofer is a personal call; it's certainly a difficult enough production that having someone to fall back on may very well be warranted.

For those willing to take the 20Hz challenge, the ACI Titan is the least expensive way I know of to become equipped with real bass that goes as deep as any reasonable person would want. With it's three inputs and array of crossover controls, it should be flexible enough for almost any music or home theater system.

Now, I'll clue you in to one of the great bargains available from the current market. A pair of Magnepan MMG speakers will run you $500. An ACI Titan costs $800. These two components mate together perfectly at 50Hz, and the results is stunning. For $1300, this is the killer combination to beat. What else can you buy for that price, after all? You could get a very nice two-way system for $800- $1000. See the SoundStage! reviews from companies like NEAR, Coincident, and Meadowlark for examples. All of them (along with innumerable others) make great speakers at that price point. While these are all very good, you're certainly not going to get flat bass to 20Hz out of any of them, and whether they match the realism of the planar-magnetic midrange of the Magnepans or the detail of its quasi-ribbon tweeter is debatable. I've listened to many of the sub-$1500 speakers out there, and there's none I'd pick over the MMG/Titan combo. You'd have to clear $2500 to get a big step up from that duo in a full-range system as far as I'm concerned.

Heading back to cold reality, this combination wouldn't be for everyone. You've got to be willing to deal with all the peculiarities of the MMGs, including a small sweet spot, the probable need for room treatment, and the certain need for a good amplifier. Plus, absolute output volume from the Magnepans isn't that high; try to head over 95dB or so in a normal room, and you're likely to be running into blown tweeter fuses. And I've already pointed out how much work is involved trying to get proper integration between a Titan and any set of speakers. For the "just plug it in and go crowd", these would be poor choices. But for the audiophile who's willing to put some sweat into optimizing their room, there could be a considerable musical reward for $1300 spent this way.

That summarizes my feelings toward the Titan, too. This isn't the easiest subwoofer on the market to get good results out of; it's too flexible to be simple. You've got limited resources to call on for hands-on help compared with buying something locally. Buying mail-order also involves the ugly reality of shipping; the Titan I was shipped got a big notch taken out of it during transport, enough so that even through ACI's heavy packaging there was a small ding on the finish. The reward for your trouble is one of the best subwoofers available for under $1000, configurable for almost any system if you plan properly and get the right accessories. Considering how good it sounds for what you pay, I suspect most complaints about the ACI Titan come from the neighbors of those who own one.

.....GS (

ACI Titan
Price: $799 USD
Available Factory Direct Only

Review Source for all products: Audio Concepts, Inc.

Audio Concepts, Inc.
901 South 4th Street
La Crosse, WI 54601
Phone: 608-784-4570
Fax: 608-784-6367


Mike Dzurko of Audio Concepts responds:

Our thanks to Greg Smith for an extremely thorough and detailed review of our Titan powered sub. This information will be useful to anyone considering the purchase of a powered sub, or just wanting to improve the performance of a sub they already own. A few more tips/ideas:

  1. I've often found it helpful to plug the port of a vented speaker when adding a subwoofer. The plugged vent changes the roll-off to a more gradual and constant 12dB/octave which often interfaces better with a sub. This may have helped Greg's Klipsch speakers integrate better with the Titan. [Nice idea normally, but they have a passive radiator that isn't so easy to plug --GS]
  2. Experience and customer feedback confirms that often the best place for a sub is in one of the corners behind the main speakers. If your room allows for corner placement, I'd try it first.
  3. Our customers have successfully matched the Titan with a huge variety of speakers models. I believe adding a Titan or two will improve most systems. However, I also believe that the final decision is the customer's, and that's why all our speaker systems are sold with a money-back guarantee.
  4. A single Titan is more than sufficient for most people, However, approximately 35% of our customers use a pair of Titans. A pair of Titans adds 6db of clean output level. We feel it is easier to place two Titans in a room than one HUGE box.
  5. Greg mentioned some minor shipping damage to his Titan. In spite of our best attempts to pack our systems safely, occasionally we incur shipping damage. We fully insure all shipments, and usually can have a replacement shipped and the damaged unit picked up within days.

I think Greg sums it up best: "At $799 direct from the factory, the Titan is a bargain".

Announcement: sometime this July we plan to begin shipping our new "Junior" version of the Titan. Slightly smaller, response to 30Hz, 100watts, black box, projected price under $500.

Oops! I made a technical error in describing some of the below resonance roll-off in the first version of this article, and I corrupted Mike Dzurko's comments to match in a fit of bad editing. Sorry for any confusion this may have caused, it's all corrected now. All errors were mine, and I apologize to Mr. Dzurko for putting incorrect words in his mouth. --GS