 Once you've mastered the basics of bass management, a subwoofer tucked away in the corner can deliver amazing bass. |
Back when I was growing up, bass management meant one thing — fiddling with the knob right next to the one that read "treble." And if you were lucky enough to have a "loudness" button, you could press it for an added dose of artificial bass kick. But nowadays, with multichannel mixes, separate subwoofer units, and adjustable crossovers, bass control is more than a little bit complicated. The fact is many people (even some with great systems) are downright baffled by the whole concept of bass management. At the very least, they're unsure as to whether or not they're getting the best possible bass performance out of their system.
Proper bass management isn't just important for smooth, high-impact bass output; it's also vital for achieving balanced overall sound, so you can experience music the way it's meant to be heard. In this article, we'll try to unravel some of the confusion surrounding bass management for a stereo setup (keep an eye out for a separate home theater and multichannel music bass management article coming soon). If you ever listen to stereo music (from CDs, satellite radio, from a networked PC, etc.), and you want to be sure you're getting the best bass your system has to offer, read on.
The low-down on bass management
First things first — if you're satisfied with the way your system handles the low frequencies, stop reading, put on your favorite disc, and forget you ever stumbled upon this article. The bottom line is, if you're happy with the way your system sounds, there's no reason to monkey with settings and connections. Just enjoy it.
On the other hand, if something just doesn't sound right, or if you think your system's got more bass pop than it's letting on, a tweak or two may make a world of difference.
The key is finding out how your receiver and subwoofer work, and then figuring out how to set things up so they play nice together. Often, folks unknowingly configure their system so that the components are working at odds with each other. That's the situation we're trying to avoid. On the following page, you'll find a list of questions and answers that will (hopefully) help lead you down a path towards truly satisfying bass.
The path to better bass
1. Does your receiver even send a signal to the subwoofer output when in stereo mode?
Most do, but some receivers' subwoofer outputs work exclusively with multichannel sources. So, in stereo mode, your subwoofer's functionality would be reduced to that of a silent footstool. The only thing worse than bad bass is no bass, and that's what you'd get. If you're unfortunate enough to own a receiver that falls into this category, skip down to question #4.
2. If your receiver's subwoofer output does send a signal in stereo mode, is it a full-frequency signal or a filtered, low-frequency signal?
As you know, your subwoofer is only designed to produce low-frequency sounds. Making your sub produce midrange or high frequencies is a recipe for disaster. So, how does your subwoofer know to only play the low frequencies? Well, it doesn't — it will try to play whatever signal reaches the driver. To prevent your sub from trying to play a searing Van Halen guitar solo or Tiny Tim's quavering vocals, a crossover filter blocks frequencies above a certain level (usually somewhere between 80Hz and 150Hz).
This crossover filter can live in your receiver or in the subwoofer unit. It's important to know if your receiver's sub output sends a full-frequency signal or a filtered low-frequency signal (check your receiver manual for details). Most are filtered, but if it happens to be a full-frequency signal, you'll have to count on your subwoofer's crossover filter to edit out the higher frequencies, which is just fine. But wait a minute, I know what you're thinking
3. What if both your subwoofer and your receiver have a crossover filter? Couldn't that cause some problems?
The answer is yes. And, the fact is, most people will probably end up with this dilemma because most powered subwoofers and most receivers have crossover filters. When you have two different filters wrestling over the same signal, you can end up with some very bad bass. You might be able to adjust the filters so they don't interfere with each other. This will require some experimentation.
But wouldn't it be great if you could just shut off one of the filters? You may be able to do just that — many subs come with either an LFE/normal switch or separate LFE and normal inputs. Just set your sub to LFE (or use the separate LFE input) and presto, the subwoofer filter is defeated, and your receiver's filter is flying solo. Everything's great, right? Well, kind of.
There's a very good chance that your subwoofer filter is better than your receiver filter and here's why: subwoofer filters are usually "continuously variable," meaning you can adjust the crossover point by single frequency units. You can get an ideal blend between your stereo speakers and sub. By shutting it off, you're losing one of the really cool features of your sub.
Receiver crossovers are often not variable; you're stuck with a crossover frequency preset by the manufacturer, and it might not work well with your sub and stereo speakers. And even if your receiver filter is variable, you usually can only choose between something like two and six different frequency settings certainly inferior to the fine-tuning you can do with a continuously variable subwoofer filter.
If you shut off your subwoofer filter and discover that your receiver filter is set just right for great bass performance with your system, you're good to go. If not (and if your receiver doesn't allow for adjustments that work for your gear), you're probably in trouble, because most receivers don't allow you to shut off their built-in crossover filter.
So, now what do you do?
 Most subwoofer back panels give you a lot of options — make the most of them! |
1. Does your receiver even send a signal to the subwoofer output when in stereo mode?
Most do, but some receivers' subwoofer outputs work exclusively with multichannel sources. So, in stereo mode, your subwoofer's functionality would be reduced to that of a silent footstool. The only thing worse than bad bass is no bass, and that's what you'd get. If you're unfortunate enough to own a receiver that falls into this category, skip down to question #4.
2. If your receiver's subwoofer output does send a signal in stereo mode, is it a full-frequency signal or a filtered, low-frequency signal?
As you know, your subwoofer is only designed to produce low-frequency sounds. Making your sub produce midrange or high frequencies is a recipe for disaster. So, how does your subwoofer know to only play the low frequencies? Well, it doesn't — it will try to play whatever signal reaches the driver. To prevent your sub from trying to play a searing Van Halen guitar solo or Tiny Tim's quavering vocals, a crossover filter blocks frequencies above a certain level (usually somewhere between 80Hz and 150Hz).
This crossover filter can live in your receiver or in the subwoofer unit. It's important to know if your receiver's sub output sends a full-frequency signal or a filtered low-frequency signal (check your receiver manual for details). Most are filtered, but if it happens to be a full-frequency signal, you'll have to count on your subwoofer's crossover filter to edit out the higher frequencies, which is just fine. But wait a minute, I know what you're thinking
3. What if both your subwoofer and your receiver have a crossover filter? Couldn't that cause some problems?
The answer is yes. And, the fact is, most people will probably end up with this dilemma because most powered subwoofers and most receivers have crossover filters. When you have two different filters wrestling over the same signal, you can end up with some very bad bass. You might be able to adjust the filters so they don't interfere with each other. This will require some experimentation.
But wouldn't it be great if you could just shut off one of the filters? You may be able to do just that — many subs come with either an LFE/normal switch or separate LFE and normal inputs. Just set your sub to LFE (or use the separate LFE input) and presto, the subwoofer filter is defeated, and your receiver's filter is flying solo. Everything's great, right? Well, kind of.
There's a very good chance that your subwoofer filter is better than your receiver filter and here's why: subwoofer filters are usually "continuously variable," meaning you can adjust the crossover point by single frequency units. You can get an ideal blend between your stereo speakers and sub. By shutting it off, you're losing one of the really cool features of your sub.
Receiver crossovers are often not variable; you're stuck with a crossover frequency preset by the manufacturer, and it might not work well with your sub and stereo speakers. And even if your receiver filter is variable, you usually can only choose between something like two and six different frequency settings certainly inferior to the fine-tuning you can do with a continuously variable subwoofer filter.
If you shut off your subwoofer filter and discover that your receiver filter is set just right for great bass performance with your system, you're good to go. If not (and if your receiver doesn't allow for adjustments that work for your gear), you're probably in trouble, because most receivers don't allow you to shut off their built-in crossover filter.
So, now what do you do?
 When your sub and receiver are working together, you'll hear the difference. |
4. If you can't get a satisfying connection through the subwoofer output on your receiver, is there any other way to hook up your subwoofer?
Since only high-end receivers give you a preamp-out/main-in option, the only other alternative for most people is to use the front left and right speaker-level outputs.
Most subwoofers have speaker-level inputs and many have speaker-level outputs, too. Just hook up your sub from your receiver's front left and right speaker outputs using ordinary speaker cable. This will be a full-frequency signal, but the sub's built-in filter will block the higher frequencies. Then, connect your stereo speakers via the subwoofer's speaker-level outputs. Your sub will pass on the unfiltered, full-frequency signal. If your sub does not have speaker-level outputs, you can parallel wire both the sub and stereo speakers from your receiver's speaker terminals.
Many would argue that wiring your subwoofer with a speaker-level connection would introduce unwanted noise into your low frequencies, and this may very well be the case. This method should only be used if you (for whatever reason) can't get a satisfactory line-level connection through your receiver's subwoofer output.
Did you get all that?
PHEW! Well, I guess if managing your bass was easy, everyone would have crisp, rich low-frequency tones and perfectly balanced sound … but the reality is, most people don't.
Once again, the key is making sure your receiver and subwoofer are working together in a sonically symbiotic relationship. Check your receiver and subwoofer manuals carefully for details and make your connectivity decisions accordingly. If the pertinent information is not provided in the manuals (which is often the case), contact the manufacturer directly. If you're adding a new sub or receiver to your system, you should pay close attention to bass management issues before you buy.