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Subwoofers
Subwoofer myths exposed
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<blockquote data-quote="So Low iT Hz" data-source="post: 8213995" data-attributes="member: 658541"><p><a href="http:////forums/usertag.php?do=list&amp;action=hash&amp;hash=10" target="_blank">#10</a> cone material affects the sound</p><p></p><p>For low frequencies, the cone on a driver makes no difference in the sound whatsoever. The only possible affect it could have is in the case of a metal cone or very stiff composite cone that resonates at a high frequencies and buzzes. However this frequency would be up around 1000 to 2000Hz: Well beyond a bass driver’s usable limits.</p><p></p><p>Various cone materials are used for various purposes. Some cones, such as composite core with fiberglass or carbon fiber skins are extremely light and very stiff, especially when pressed with epoxy. Other cones such as aluminum provide excellent thermal cooling to decrease voice coil operating temperatures when the heat is conducted though the (if possible) conductive former. The cones job is to push air, not break, and ideally not be too heavy (easier said that done). But they don’t change the tone, pitch or timbre of a subwoofer system whatsoever. Anyone who tells you otherwise is probably hearing differences in the motor distortion, likely related to BL, compliance or other non-linear distortions not relating to the cone.</p><p></p><p><a href="http:////forums/usertag.php?do=list&amp;action=hash&amp;hash=11" target="_blank">#11</a> bigger magnet means more magnetic force</p><p></p><p>The motor is essentially the steel and magnets on the bottom of the driver. Its job to create a magnetic circuit that has an air gap where flux lines cross in one direction so that a coil can rest in this field and carry current which then produces a force up and down and moves the piston to create SPL. The force that this motor creates is dependent on the amount of power or rather current inside the conductor F = B*L*I. So we need a more intuitive understanding of how a motor affects a driver’s performance without considering how much current it receives. This is the simple concept of “force factor”. Larger motors will ideally have higher force factors, but this number not only affected by the motor, its affected by the voice coil size, length, distance to the motor (gap) and conductive martial used too. The end result is in fact the BL squared divided by Re (resistance of the vc). This is literally Newtons squared per watt and is called the force factor. The higher the number, the more efficient the motor voice coil combination is and the more performance you get out of the motor.</p><p></p><p>BL, one of the many TS parameters you are probably somewhat familiar with. It is literally the magnetic field “B” crossed with the conductor length “L.” L does not in fact depend on the number of turns on the voice coil, but rather the actual cross section area of the coil itself which is inside the gap. While force factor is entirely important for any high performance driver, one should also consider the moving mass. A 600 horse power engine in a semi truck is pretty typical, but in a sports car it’s certainly something to gloat about. Together, the force factor, moving mass and the piston area account for sensitivity. This number is very important even for subwoofers, especially for frequencies above ~60Hz.</p><p></p><p><a href="http:////forums/usertag.php?do=list&amp;action=hash&amp;hash=12" target="_blank">#12</a> Double bass kick, only good sounding drivers can do it</p><p></p><p>We have all heard that only good “SQ” drivers can do double bass kick because they have good transient response or something to that extent. This is really nothing more than linear frequency response and lack of ring. If high Q subwoofers are in small boxes or if low Q subwoofers are in large ported boxes, the frequency response of the system will likely be greatly non-linear. This non-linear response compromises relative SPL and can drown out certain sounds and frequencies. Room acoustics can also do the same thing. The same subwoofer may sound completely different in another room simply because there could be poor coupling and non-linear frequency response as a result of standing waves and peaks in the response curve. A peak at 80Hz may make for a rather anemic 60Hz response, and while 60Hz appears to be the problem, it’s actually from the nonlinear response else where! The bottom line is “double bass kicks” are usually not a function of the driver or driver’s performance but rather the system design, linear frequency and room equalization.</p><p></p><p>Often times people associate double bass as something to do with speed and only good drivers are fast. Believe it or not, even the largest and heaviest drivers, have no problem producing low frequencies, even 300Hz is a relatively slow long wavelength with a slow impulse time. Subwoofers are in fact MUCH faster than you would expect. Bottom line is, the lack of double bass, within the working limits of a driver, is not a problem with the driver so much as it is probably a problem with the system design, room and/or EQ settings.</p><p></p><p><a href="http:////forums/usertag.php?do=list&amp;action=hash&amp;hash=13" target="_blank">#13</a> Transient response is better with sealed boxes</p><p></p><p>The fact is “transient response” is truly misleading and probably entirely unimportant at least for low frequency response. What people hear is really a function of the linear frequency response and distortion. It is often accepted that transient is a function of timing, but our ability to hear differences of a few milliseconds of low frequencies is quite negligible which is why the low frequency group delay of a 4th order system is quite unimportant next to the sensitivity advantages provided. Transient does not exclusively depend on sealed or ported designs, high Q, low Q, in fact, even drivers with high inductance don’t outright suffer from “transient response” insofar as we can physically distinguish certain sporadic behaviors because within their working range, they may be very efficient and dynamic. The fact is, what makes bass indeed bass, are long wavelengths that take considerable time to pass our ears. The perception of transient is really a function of perceived sound quality and there is really not appropriate example for good “transient response”. We as humans hear two things, distortion and SPL, and in the end that’s really want matters. What does improve “transient” response or perceived quality is usually more headroom, more drivers (usually larger boxes depending on the Qts of the driver), better efficiency and ultra low distortion within the prescribed limits of the system or drivers within the system. Sealed systems in fact don’t offer better transient response no more than ported even with their lower group delay tendencies, at least to human ears!</p></blockquote><p></p>
[QUOTE="So Low iT Hz, post: 8213995, member: 658541"] [URL="http:////forums/usertag.php?do=list&action=hash&hash=10"]#10[/URL] cone material affects the sound For low frequencies, the cone on a driver makes no difference in the sound whatsoever. The only possible affect it could have is in the case of a metal cone or very stiff composite cone that resonates at a high frequencies and buzzes. However this frequency would be up around 1000 to 2000Hz: Well beyond a bass driver’s usable limits. Various cone materials are used for various purposes. Some cones, such as composite core with fiberglass or carbon fiber skins are extremely light and very stiff, especially when pressed with epoxy. Other cones such as aluminum provide excellent thermal cooling to decrease voice coil operating temperatures when the heat is conducted though the (if possible) conductive former. The cones job is to push air, not break, and ideally not be too heavy (easier said that done). But they don’t change the tone, pitch or timbre of a subwoofer system whatsoever. Anyone who tells you otherwise is probably hearing differences in the motor distortion, likely related to BL, compliance or other non-linear distortions not relating to the cone. [URL="http:////forums/usertag.php?do=list&action=hash&hash=11"]#11[/URL] bigger magnet means more magnetic force The motor is essentially the steel and magnets on the bottom of the driver. Its job to create a magnetic circuit that has an air gap where flux lines cross in one direction so that a coil can rest in this field and carry current which then produces a force up and down and moves the piston to create SPL. The force that this motor creates is dependent on the amount of power or rather current inside the conductor F = B*L*I. So we need a more intuitive understanding of how a motor affects a driver’s performance without considering how much current it receives. This is the simple concept of “force factor”. Larger motors will ideally have higher force factors, but this number not only affected by the motor, its affected by the voice coil size, length, distance to the motor (gap) and conductive martial used too. The end result is in fact the BL squared divided by Re (resistance of the vc). This is literally Newtons squared per watt and is called the force factor. The higher the number, the more efficient the motor voice coil combination is and the more performance you get out of the motor. BL, one of the many TS parameters you are probably somewhat familiar with. It is literally the magnetic field “B” crossed with the conductor length “L.” L does not in fact depend on the number of turns on the voice coil, but rather the actual cross section area of the coil itself which is inside the gap. While force factor is entirely important for any high performance driver, one should also consider the moving mass. A 600 horse power engine in a semi truck is pretty typical, but in a sports car it’s certainly something to gloat about. Together, the force factor, moving mass and the piston area account for sensitivity. This number is very important even for subwoofers, especially for frequencies above ~60Hz. [URL="http:////forums/usertag.php?do=list&action=hash&hash=12"]#12[/URL] Double bass kick, only good sounding drivers can do it We have all heard that only good “SQ” drivers can do double bass kick because they have good transient response or something to that extent. This is really nothing more than linear frequency response and lack of ring. If high Q subwoofers are in small boxes or if low Q subwoofers are in large ported boxes, the frequency response of the system will likely be greatly non-linear. This non-linear response compromises relative SPL and can drown out certain sounds and frequencies. Room acoustics can also do the same thing. The same subwoofer may sound completely different in another room simply because there could be poor coupling and non-linear frequency response as a result of standing waves and peaks in the response curve. A peak at 80Hz may make for a rather anemic 60Hz response, and while 60Hz appears to be the problem, it’s actually from the nonlinear response else where! The bottom line is “double bass kicks” are usually not a function of the driver or driver’s performance but rather the system design, linear frequency and room equalization. Often times people associate double bass as something to do with speed and only good drivers are fast. Believe it or not, even the largest and heaviest drivers, have no problem producing low frequencies, even 300Hz is a relatively slow long wavelength with a slow impulse time. Subwoofers are in fact MUCH faster than you would expect. Bottom line is, the lack of double bass, within the working limits of a driver, is not a problem with the driver so much as it is probably a problem with the system design, room and/or EQ settings. [URL="http:////forums/usertag.php?do=list&action=hash&hash=13"]#13[/URL] Transient response is better with sealed boxes The fact is “transient response” is truly misleading and probably entirely unimportant at least for low frequency response. What people hear is really a function of the linear frequency response and distortion. It is often accepted that transient is a function of timing, but our ability to hear differences of a few milliseconds of low frequencies is quite negligible which is why the low frequency group delay of a 4th order system is quite unimportant next to the sensitivity advantages provided. Transient does not exclusively depend on sealed or ported designs, high Q, low Q, in fact, even drivers with high inductance don’t outright suffer from “transient response” insofar as we can physically distinguish certain sporadic behaviors because within their working range, they may be very efficient and dynamic. The fact is, what makes bass indeed bass, are long wavelengths that take considerable time to pass our ears. The perception of transient is really a function of perceived sound quality and there is really not appropriate example for good “transient response”. We as humans hear two things, distortion and SPL, and in the end that’s really want matters. What does improve “transient” response or perceived quality is usually more headroom, more drivers (usually larger boxes depending on the Qts of the driver), better efficiency and ultra low distortion within the prescribed limits of the system or drivers within the system. Sealed systems in fact don’t offer better transient response no more than ported even with their lower group delay tendencies, at least to human ears! [/QUOTE]
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