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Top Ten Reasons Why Subwoofers and B&W Loudspeakers Don't Mix Musically... Usually
DISCLAIMER: I make some pretty bold statements in the proceeding essay. If you think you might be offended stop here. It was not my intention to offend anyone but I have some very strong feelings about this subject as it pertains to B&W loudspeakers.
Some people are of the mind that subwoofers are not only beneficial but necessary to realize and fully enjoy music reproduction in all of it's varieties. While I agree to some extent that subwoofers can in some unique situations aid the listener I do not agree that it is a requirement for the majority of people with full range monitors. What is full range? Any loudspeaker capable of producing bass, midrange and treble frequencies with high-fidelity. What is high fidelity? It is the reproduction of sound that faithfully captures the original master recording. Unfortunately, subwoofers, even high quality ones, fail to maintain true and authentic to the source material because of the lack of expertise employed by its user and/or the types of techniques required to integrated them into a high performance two-channel system. Here's why...
10. Room Placement - You thought finding the right spot for your mains was tough try adding a sub to the equation. The same rules apply but guess what? Your mains should already be occupying the optimal position within the room. This wouldn't be a problem if you used your sub the way it was intended and that is to produce sub bass, that is below bass, not mid-bass. Our audible threshold of bass starts at 20Hz, not 60+Hz. Placing your sub anywhere in the room where it can be localized is a problem that many, including myself, have difficulty contending with because of the domestic restrictions most of us must deal with. Two subs are definitely better than one in this case but only if you have the means to accommodate them. Who among us do? Not many.
9. Room Excitation - You finally have gotten your mains positioned for the best response in your room and they sound great but you "think" that something is missing... low bass. So now you add a sub to make up for (what you "think") are the inadequacies of your left and right speakers. Guess what, you may have just created new problem. The energy at some low frequencies may now be coincident to the resonant modes of your room. If you are one of the lucky few that have EQing abilities built into your sub this would seem like a non-issue. Time to refresh yourself with the definition of what it means to have high-fidelity that started this post. EQ's are the antithesis of audio purity. Fixed EQ's have gaps in-between frequencies that cannot be compensated for and variable realtime EQ's correct the signal after it has been produced. Both artificially manipulating the original signal. A high performance stereo system is designed to stay out of the way of the signal path, not jump head on into it. If you have a room that behaves poorly, treat the room! Don't bandaid the signal. Adding a second sub would be a great idea and would go a long way in taming the standing waves, if you can mange it, which again many if not most of us can't.
8. Crossover Frequency - The general rule of thumb for setting the subwoofer crossover point is double the low frequency response of the main speakers. The problem with this is that most loudspeakers would require settings of of 60+Hz or more to compensate for slope variations thus crossing into mid-bass territory; recognized to be 40+Hz. Most subwoofers are not very adept at producing mid-bass frequencies much less upper bass which is what the engineers of your B&W's spent years perfecting. For home theater this is fine but it's not so good for revealing the subtleties within the musical fabric.
7. Phase Relationships - Some subs provide the means for adjusting this parameter, sometimes called a delay, with an adjustment knob. Other's are less accommodating by using switches. The difficulty comes in knowing how much delay to apply. Once you know how it is pretty straight forward. Do you know how? I'll give you a hint, invert the polarities of your mains and pipe a 25Hz test tone through your system and dial the knob or better yet laterally move your sub. What do you think you should hear? Very little! Improper phase calibration could mean a breakdown in linear response or over excitation of certain modes drawing attention to the sub when there shouldn't be.
6. Pitch and Timbre - How good are you at detecting driver induced resonances? You know they exist right? Well they do. Every transducer on the planet comes with it's own blend of color. What would you do if you needed to replace one of the woofers in your beloved B&W's? Will it come from Scan-Speak? How about Usher or better yet Focal? Maybe you could save yourself the trouble and expense by picking up a garden variety type off the shelf of your local electronics supply store. Unlikely that you would I am sure. Chances are you will replace the woofer with an original OEM. So why choose a different make and model transducer for your subwoofer? If all you wanted from your sub was sub-bass then this wouldn't be an issue. But you aren't asking your sub to produce LFE you are asking it to produce mid-bass. Herein lies the problem. Low frequencies produced by the sub can sound different from the low frequencies produced by the mains. The discontinuity manifests itself in a variation of pitch and timbre at different bass registers. Bass notes don't instantly drop off with one driver to be immediately picked up by another. Slopes cross over. Some of this can be compensated for but not so easily with most subs.
5. System Q - Have you got Q? How much Q do you have? What the heck is Q? Q is a quality factor. It is a unit-less number that describes the resonant characteristics of woofers. A high measure of Q means a lower level of damping and a lower measure of Q means a higher level of damping. So what's this got to do with subs? Everything! Remember the objective is to integrate the subwoofer with the mains not to simply add it. The problem is high quality loudspeakers like B&W, have been engineered to deliver taut, lean, and quick bass impulses with very little overhang. Most subwoofers are not designed in this articulating fashion. Some servo based (distortion controller) subs can ameliorate this to some degree but they are not completely immune from ringing at upper bass frequencies. Check point reminder, subwoofers are meant to do one thing and one thing only and that is to produce prodigious amounts of sub-bass, not low bass but sub-bass.
4. Signal Integrity - Here is the oft overlooked killer of signal purity, the subwoofer crossover network. How do you get your sub to properly mesh with your mains? One way is to use low level (line level) signals. The other way is to use high-level (speaker level) signals. Most audio purists, including myself, would recommend balanced low level signals whenever possible. If you don't have this option then go with single ended connections. But don't use high level signals unless you can't avoid them. Why? Because some subs use a fixed high pass frequency and slope when passing high signal levels to your main speakers. Mixed crossover slopes can show up as discontinuities in the low frequencies between the mid-bass bass produced by the mains and the low bass that is produced by the subwoofer. Furthermore, the quality of the crossover network and topology may not be of the same caliber as your mains and you simultaneously introduce another sound degrading circuit into the signal pathway. Folks, if you ever wanted to know the reason for sticking with the same manufacture for your mains and sub, this is it!
3. Cabinet Design - When is a sub a musical sub? When it has no ports. Reflex loaded subs are designed with the sole intention of efficiently delivering visceral feel and impact at subsonic frequencies. Problem is they are not as competent at delivering the subtle nuances of music in the mid-bass region. It may seem like ported subs are accomplished low bass producers once they have been dialed in but it isn't "good" musical bass only good special effects bass that includes chuffing noise. Sealed subs are much better at low bass definition but generally need to be larger than their ported cousins and are usually much less efficient. This may seen like no big deal until you discover the tradeoff the manufacture had to make in cabinet construction to get it that size. When was the last time you "felt" your sub? That's right I said felt. Next opportunity you get, while playing music, feel your sub. Then feel your mains. If high performance audio means anything to you cabinet resonance should be non existent. You can't hear what you don't feel! Why spend all the time, trouble and expense to furnish your room with speakers that add very little of their own noise to the music you enjoy only to spoil it with a fat sub? Tattoo this thought to your head, subs mean distortion!
2. Level Control - Here' a biggy, the volume control. You just spent $$$ dollars on that new state-of-the-art sub so you can hear what you think you have been missing in your music sources so you better be able to hear it, right? Maybe it's time to rethink what you've been thinking. Maybe it's time for a pair of hearing aids? Or maybe its time to educate yourself with equal-loudness contours? The human ear is less sensitive to frequencies that extends much below 1KHz or above 5KHz. Couple this with your hearing ability, or the lack thereof, and the issue is exacerbated. I am a 40 year old male with an average +5dB in the right ear and 0dB in the left, according to my last audiometer report in April. Superimposing my results to that with the absolute threshold of hearing curves places my hearing aptitude with that of a 20 year old male. I am not suggesting that I am the man with the golden ears or that I have perfect hearing, although my doctor seems to think so. What I am saying is that I have learned to become a very good listener and I don't require the boost on the low side of the frequency spectrum that others may need to enjoy the full range of the audio band. I don't need to feel the music I only need to hear it. But when I do feel the need I only need to adjust one volume knob not two thus avoiding yet another problem subs create at low frequencies. Understand what equal-loudness curves is all about and you'll understand exactly what I meant by the last statement.
1. What do you know about B&W? - What do you know about the British sound? Seriously, what do you know? B&W's house sound can be simply described as somewhat forward in the high band (treble), somewhat reserved in the mid-band (midrange) and somewhat polite in the low-band (bass). Further up the range of B&W models the more refined and closer to neutral the performance of their loudspeakers become. But make no mistake, the Brits are no stranger to making bass, good articulate bass that is accurate and revealing. But don't expect to find the thunderous heart pounding knock you off the edge of your seat bass that you have come to expect from the loud and obnoxious sound systems used to put on most concert shows. You aren't going to find it here. But with an appropriate set of ancillary equipment what you will achieve is the quickness of attack and undistorted transient decay that only comes from unamplified acoustically projected live venues be it at semi-large or quaint little forums. The results may not be as polished as that you'll find from the same act in the recording studio but the intimate connection that you get from listening to the artist will be no different. If you are bass hound then I suggest you look elsewhere. The are some notable manufacturers, Vandersteen is one that comes to mind, that engineer their speakers from the ground up using built in subwoofers for those that need them. Also be sure to take into consideration your style of music. Most music rarely reaches energy levels much below 28Hz. If the kind you listen two hits this mark frequently, consider speakers that are engineer for these applications. B&W's own 801D passive radiators comes very close but even it will fall somewhat short on those rare occasions.
Reading these ten reasons not to use a subwoofer for music would seem to indicate that it would be wrong in doing so. Well the reality is that it is neither right nor wrong. People should be compelled to do what feels good to them. We all have unique tastes and abilities which are carried over to the choices we are free to make. One cannot make a bad choice here. However, attached to the choices we make are the unavoidable conditions that go with them. Ask yourself this question, why am I here reading this post in Club B&W on HTGuide? Well, I believe one reason is because you have more than just a passing interest in B&W loudspeakers. I believe you are looking for answers to questions like what constitutes good sound and how can I achieve it? One way is to read the experiences of others the other is to experience it for yourself. My experience tells me subwoofers have no place in accurately representing the pre-recoded music that I prefer and have compared to live forums not equipped with public address systems, which far too many people falsely associate quality too. Now I am not completely abdicating the use of subwoofers altogether for stereo playback but I am of the mind that it isn't necessary for the vast majority of listeners and for anyone to suggest subs are unconditionally necessary is totally misleading of the truth and completely inaccurate.
Some people are of the mind that subwoofers are not only beneficial but necessary to realize and fully enjoy music reproduction in all of it's varieties. While I agree to some extent that subwoofers can in some unique situations aid the listener I do not agree that it is a requirement for the majority of people with full range monitors. What is full range? Any loudspeaker capable of producing bass, midrange and treble frequencies with high-fidelity. What is high fidelity? It is the reproduction of sound that faithfully captures the original master recording. Unfortunately, subwoofers, even high quality ones, fail to maintain true and authentic to the source material because of the lack of expertise employed by its user and/or the types of techniques required to integrated them into a high performance two-channel system. Here's why...
10. Room Placement - You thought finding the right spot for your mains was tough try adding a sub to the equation. The same rules apply but guess what? Your mains should already be occupying the optimal position within the room. This wouldn't be a problem if you used your sub the way it was intended and that is to produce sub bass, that is below bass, not mid-bass. Our audible threshold of bass starts at 20Hz, not 60+Hz. Placing your sub anywhere in the room where it can be localized is a problem that many, including myself, have difficulty contending with because of the domestic restrictions most of us must deal with. Two subs are definitely better than one in this case but only if you have the means to accommodate them. Who among us do? Not many.
9. Room Excitation - You finally have gotten your mains positioned for the best response in your room and they sound great but you "think" that something is missing... low bass. So now you add a sub to make up for (what you "think") are the inadequacies of your left and right speakers. Guess what, you may have just created new problem. The energy at some low frequencies may now be coincident to the resonant modes of your room. If you are one of the lucky few that have EQing abilities built into your sub this would seem like a non-issue. Time to refresh yourself with the definition of what it means to have high-fidelity that started this post. EQ's are the antithesis of audio purity. Fixed EQ's have gaps in-between frequencies that cannot be compensated for and variable realtime EQ's correct the signal after it has been produced. Both artificially manipulating the original signal. A high performance stereo system is designed to stay out of the way of the signal path, not jump head on into it. If you have a room that behaves poorly, treat the room! Don't bandaid the signal. Adding a second sub would be a great idea and would go a long way in taming the standing waves, if you can mange it, which again many if not most of us can't.
8. Crossover Frequency - The general rule of thumb for setting the subwoofer crossover point is double the low frequency response of the main speakers. The problem with this is that most loudspeakers would require settings of of 60+Hz or more to compensate for slope variations thus crossing into mid-bass territory; recognized to be 40+Hz. Most subwoofers are not very adept at producing mid-bass frequencies much less upper bass which is what the engineers of your B&W's spent years perfecting. For home theater this is fine but it's not so good for revealing the subtleties within the musical fabric.
7. Phase Relationships - Some subs provide the means for adjusting this parameter, sometimes called a delay, with an adjustment knob. Other's are less accommodating by using switches. The difficulty comes in knowing how much delay to apply. Once you know how it is pretty straight forward. Do you know how? I'll give you a hint, invert the polarities of your mains and pipe a 25Hz test tone through your system and dial the knob or better yet laterally move your sub. What do you think you should hear? Very little! Improper phase calibration could mean a breakdown in linear response or over excitation of certain modes drawing attention to the sub when there shouldn't be.
6. Pitch and Timbre - How good are you at detecting driver induced resonances? You know they exist right? Well they do. Every transducer on the planet comes with it's own blend of color. What would you do if you needed to replace one of the woofers in your beloved B&W's? Will it come from Scan-Speak? How about Usher or better yet Focal? Maybe you could save yourself the trouble and expense by picking up a garden variety type off the shelf of your local electronics supply store. Unlikely that you would I am sure. Chances are you will replace the woofer with an original OEM. So why choose a different make and model transducer for your subwoofer? If all you wanted from your sub was sub-bass then this wouldn't be an issue. But you aren't asking your sub to produce LFE you are asking it to produce mid-bass. Herein lies the problem. Low frequencies produced by the sub can sound different from the low frequencies produced by the mains. The discontinuity manifests itself in a variation of pitch and timbre at different bass registers. Bass notes don't instantly drop off with one driver to be immediately picked up by another. Slopes cross over. Some of this can be compensated for but not so easily with most subs.
5. System Q - Have you got Q? How much Q do you have? What the heck is Q? Q is a quality factor. It is a unit-less number that describes the resonant characteristics of woofers. A high measure of Q means a lower level of damping and a lower measure of Q means a higher level of damping. So what's this got to do with subs? Everything! Remember the objective is to integrate the subwoofer with the mains not to simply add it. The problem is high quality loudspeakers like B&W, have been engineered to deliver taut, lean, and quick bass impulses with very little overhang. Most subwoofers are not designed in this articulating fashion. Some servo based (distortion controller) subs can ameliorate this to some degree but they are not completely immune from ringing at upper bass frequencies. Check point reminder, subwoofers are meant to do one thing and one thing only and that is to produce prodigious amounts of sub-bass, not low bass but sub-bass.
4. Signal Integrity - Here is the oft overlooked killer of signal purity, the subwoofer crossover network. How do you get your sub to properly mesh with your mains? One way is to use low level (line level) signals. The other way is to use high-level (speaker level) signals. Most audio purists, including myself, would recommend balanced low level signals whenever possible. If you don't have this option then go with single ended connections. But don't use high level signals unless you can't avoid them. Why? Because some subs use a fixed high pass frequency and slope when passing high signal levels to your main speakers. Mixed crossover slopes can show up as discontinuities in the low frequencies between the mid-bass bass produced by the mains and the low bass that is produced by the subwoofer. Furthermore, the quality of the crossover network and topology may not be of the same caliber as your mains and you simultaneously introduce another sound degrading circuit into the signal pathway. Folks, if you ever wanted to know the reason for sticking with the same manufacture for your mains and sub, this is it!
3. Cabinet Design - When is a sub a musical sub? When it has no ports. Reflex loaded subs are designed with the sole intention of efficiently delivering visceral feel and impact at subsonic frequencies. Problem is they are not as competent at delivering the subtle nuances of music in the mid-bass region. It may seem like ported subs are accomplished low bass producers once they have been dialed in but it isn't "good" musical bass only good special effects bass that includes chuffing noise. Sealed subs are much better at low bass definition but generally need to be larger than their ported cousins and are usually much less efficient. This may seen like no big deal until you discover the tradeoff the manufacture had to make in cabinet construction to get it that size. When was the last time you "felt" your sub? That's right I said felt. Next opportunity you get, while playing music, feel your sub. Then feel your mains. If high performance audio means anything to you cabinet resonance should be non existent. You can't hear what you don't feel! Why spend all the time, trouble and expense to furnish your room with speakers that add very little of their own noise to the music you enjoy only to spoil it with a fat sub? Tattoo this thought to your head, subs mean distortion!
2. Level Control - Here' a biggy, the volume control. You just spent $$$ dollars on that new state-of-the-art sub so you can hear what you think you have been missing in your music sources so you better be able to hear it, right? Maybe it's time to rethink what you've been thinking. Maybe it's time for a pair of hearing aids? Or maybe its time to educate yourself with equal-loudness contours? The human ear is less sensitive to frequencies that extends much below 1KHz or above 5KHz. Couple this with your hearing ability, or the lack thereof, and the issue is exacerbated. I am a 40 year old male with an average +5dB in the right ear and 0dB in the left, according to my last audiometer report in April. Superimposing my results to that with the absolute threshold of hearing curves places my hearing aptitude with that of a 20 year old male. I am not suggesting that I am the man with the golden ears or that I have perfect hearing, although my doctor seems to think so. What I am saying is that I have learned to become a very good listener and I don't require the boost on the low side of the frequency spectrum that others may need to enjoy the full range of the audio band. I don't need to feel the music I only need to hear it. But when I do feel the need I only need to adjust one volume knob not two thus avoiding yet another problem subs create at low frequencies. Understand what equal-loudness curves is all about and you'll understand exactly what I meant by the last statement.
1. What do you know about B&W? - What do you know about the British sound? Seriously, what do you know? B&W's house sound can be simply described as somewhat forward in the high band (treble), somewhat reserved in the mid-band (midrange) and somewhat polite in the low-band (bass). Further up the range of B&W models the more refined and closer to neutral the performance of their loudspeakers become. But make no mistake, the Brits are no stranger to making bass, good articulate bass that is accurate and revealing. But don't expect to find the thunderous heart pounding knock you off the edge of your seat bass that you have come to expect from the loud and obnoxious sound systems used to put on most concert shows. You aren't going to find it here. But with an appropriate set of ancillary equipment what you will achieve is the quickness of attack and undistorted transient decay that only comes from unamplified acoustically projected live venues be it at semi-large or quaint little forums. The results may not be as polished as that you'll find from the same act in the recording studio but the intimate connection that you get from listening to the artist will be no different. If you are bass hound then I suggest you look elsewhere. The are some notable manufacturers, Vandersteen is one that comes to mind, that engineer their speakers from the ground up using built in subwoofers for those that need them. Also be sure to take into consideration your style of music. Most music rarely reaches energy levels much below 28Hz. If the kind you listen two hits this mark frequently, consider speakers that are engineer for these applications. B&W's own 801D passive radiators comes very close but even it will fall somewhat short on those rare occasions.
Reading these ten reasons not to use a subwoofer for music would seem to indicate that it would be wrong in doing so. Well the reality is that it is neither right nor wrong. People should be compelled to do what feels good to them. We all have unique tastes and abilities which are carried over to the choices we are free to make. One cannot make a bad choice here. However, attached to the choices we make are the unavoidable conditions that go with them. Ask yourself this question, why am I here reading this post in Club B&W on HTGuide? Well, I believe one reason is because you have more than just a passing interest in B&W loudspeakers. I believe you are looking for answers to questions like what constitutes good sound and how can I achieve it? One way is to read the experiences of others the other is to experience it for yourself. My experience tells me subwoofers have no place in accurately representing the pre-recoded music that I prefer and have compared to live forums not equipped with public address systems, which far too many people falsely associate quality too. Now I am not completely abdicating the use of subwoofers altogether for stereo playback but I am of the mind that it isn't necessary for the vast majority of listeners and for anyone to suggest subs are unconditionally necessary is totally misleading of the truth and completely inaccurate.
ops: Anyways, its not all gloom and doom as I'm off to relisten to my CD collection on my new speakers! 
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