Post by vividjazz on Jan 16, 2006 16:35:58 GMT 10
Put simply, an enclosure is a box that the subwoofer sits in. They are vital to a good-sounding subwoofer, as subs can't deliver that full, rich bass without one. The more airspace you have in the enclosure, the deeper the bass; the less you have, the harder hitting the bass. But don't go overboard - too much or too little airspace can ruin the sound and possibly damage the sub. Almost all subs come with THIELE/SMALL parameters to enable you to design the correct sized box. Some of the manufactuerers make it even easier by providing the dimensions of the different types of boxes. Here in is a catch though because the manufacturers want to minimise warranty returns not maximise sound quality so these designs are often very conservative and can be improved upon.
* Sealed Box: An airtight enclosure with the woofer mounted directly to it. Perfect for tight, deep, accurate bass yet, because of its design, requires more power.
* Ported Box: A vented box that allows air movement in the subwoofer chamber. Perfect for a forceful, low bass response and more output which, in turn, provides more efficiency. These can be tuned to a specific frequency but take up more space as the box is larger than sealed.
* Bandpass Box: A dual-chamber box where one side is sealed and the other is vented (ported). An efficient design that delivers a loud, narrow frequency response.
* Free-Air: These are specially designed subwoofers that, instead of being placed in a box, are mounted to a board that's then usually attached to your backseat or boot; a great alternative to save you some valuable car space. Perfect for a flat frequency response. Great theory but car boots aren't airtight or soundproofed particularly in hatchbacks. Personally not recommended.
Technical bit follows - this bit is scarey and this is why they make software to design sub boxes so you just plug in the parameter numbers supplied by the manufacturer into the program and print out the design.
Thiele-Small-Parameters describe the acoustic and electrical behavior of a loudspeaker in a special case.
The most importent parameters are the resonance-frequency fs, the equivalent-volume Vas and the quality/grade Qts of the woofer. You need these to calc the size of your sub box.
fs : is the resonance-frequency (in Hertz, Hz) of the chassis: this means the first maximum of the impedance in free-field.
Most car audio stuff is 4OHM. Most home theatre is 8OHM. 2OHM and 1OHM is used in car audio stuff to increase the RMS but just because an amp is 2 or 1OHM stable doesn't mean it likes to run it. A bit like your engine. It will rev to 6,500rmp but its not going to like sitting at 6,500rpm all day, every day (though there are specialty products made to do it).
Vas : is the das equivalent-volume (in liters or cubic-foot) and describes the suppression of a loudspeaker in comparison with an air-capacity.
Qts : is the total (and acoustical!) Quality. Qts-value is the reciprocal attenuation of the membrane and decribes how hard the suspension is.
Qts = Qes * Qms / Qes / Qms
Qes : is electrical quality, the ratio of AC OHMS (often 4OHMS) to Re at fs. So Q has never a unit.
Re : is the DC-resistance of the speaker-coil (in ohms), mostly it's about twenty percent smaller than AC OHMS.
Qms : is mechanical quality, this value describes the ratio of deflection at fs.
Ok if you still with me after that your a glutton for punishment, passed high school physics or are an electrical engineer (who actually enjoys that last stuff).
* Sealed Box: An airtight enclosure with the woofer mounted directly to it. Perfect for tight, deep, accurate bass yet, because of its design, requires more power.
* Ported Box: A vented box that allows air movement in the subwoofer chamber. Perfect for a forceful, low bass response and more output which, in turn, provides more efficiency. These can be tuned to a specific frequency but take up more space as the box is larger than sealed.
* Bandpass Box: A dual-chamber box where one side is sealed and the other is vented (ported). An efficient design that delivers a loud, narrow frequency response.
* Free-Air: These are specially designed subwoofers that, instead of being placed in a box, are mounted to a board that's then usually attached to your backseat or boot; a great alternative to save you some valuable car space. Perfect for a flat frequency response. Great theory but car boots aren't airtight or soundproofed particularly in hatchbacks. Personally not recommended.
Technical bit follows - this bit is scarey and this is why they make software to design sub boxes so you just plug in the parameter numbers supplied by the manufacturer into the program and print out the design.
Thiele-Small-Parameters describe the acoustic and electrical behavior of a loudspeaker in a special case.
The most importent parameters are the resonance-frequency fs, the equivalent-volume Vas and the quality/grade Qts of the woofer. You need these to calc the size of your sub box.
fs : is the resonance-frequency (in Hertz, Hz) of the chassis: this means the first maximum of the impedance in free-field.
Most car audio stuff is 4OHM. Most home theatre is 8OHM. 2OHM and 1OHM is used in car audio stuff to increase the RMS but just because an amp is 2 or 1OHM stable doesn't mean it likes to run it. A bit like your engine. It will rev to 6,500rmp but its not going to like sitting at 6,500rpm all day, every day (though there are specialty products made to do it).
Vas : is the das equivalent-volume (in liters or cubic-foot) and describes the suppression of a loudspeaker in comparison with an air-capacity.
Qts : is the total (and acoustical!) Quality. Qts-value is the reciprocal attenuation of the membrane and decribes how hard the suspension is.
Qts = Qes * Qms / Qes / Qms
Qes : is electrical quality, the ratio of AC OHMS (often 4OHMS) to Re at fs. So Q has never a unit.
Re : is the DC-resistance of the speaker-coil (in ohms), mostly it's about twenty percent smaller than AC OHMS.
Qms : is mechanical quality, this value describes the ratio of deflection at fs.
Ok if you still with me after that your a glutton for punishment, passed high school physics or are an electrical engineer (who actually enjoys that last stuff).
