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building an enclosure..........
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<blockquote data-quote="thylantyr" data-source="post: 1320624" data-attributes="member: 560358"><p><a href="http://www.diysubwoofers.org/prt/" target="_blank">http://www.diysubwoofers.org/prt/</a></p><p></p><p>snip;</p><p></p><p><strong>A ported enclosure system consists of a driver mounted on one side of a box that has an open tunnel or port which allows the passage of air in and out of the box. At low frequencies, the vent contributes substantially to the output of the system. </strong></p><p></p><p>Ported boxes can be more efficient than a sealed box, a bonus if you want</p><p></p><p>more SPL.</p><p></p><p><strong>The ported enclosure system is characterised by lower distortion and higher power handling in the system's operating range, and lower cutoff frequency than a sealed enclosure system using the same driver.</strong></p><p></p><p>Some woofers are better suited for sealed box, some are better for ported box,</p><p></p><p>you have to model the woofer to see how it might perform. A woofer designed</p><p></p><p>for a ported box will have a lower cutoff frequency than the same woofer in</p><p></p><p>a sealed box so you get more lower end bass.</p><p></p><p><strong> Distortion rapidly increases below the cutoff frequency however as the driver becomes unloaded</strong></p><p></p><p>When you play frequencies below tuning the woofer cone can go into higher</p><p></p><p>excursion causing woofer damage and/or nasty distortion. That's why a good</p><p></p><p>design will use a subsonic filter and people try to tune as low as the design</p><p></p><p>allows to cover the 20hz and up range. Some folks try to tune lower down to</p><p></p><p>17hz if the woofer/design allows. This doesn't mean 20hz tuning is worse than</p><p></p><p>17hz, can you really notice a difference of 3hz for a single woofer system? Most</p><p></p><p>recorded music is 35hz and up, the 17hz - 20hz is recommended for HT because</p><p></p><p>movies are recorded with low frequency 'special effects', but because you are tuned low doesn't mean the music will suffer.</p><p></p><p><strong>and the transient response of a ported enclosure system is usually inferior to that of a sealed enclosure system using the same driver.</strong></p><p></p><p>This is true but over-rated, if you design a good ported box it will perform well</p><p></p><p>and you may never prefer a sealed box version of the same woofer.</p><p></p><p><strong>However, the lower cutoff frequency and better power handling within the system's passband often makes ported systems the alignment of choice for many speaker builders. </strong></p><p></p><p>Subjective</p><p></p><p><strong>Ported enclosure systems are much more sensitive to misaligned parameters than sealed enclosure systems, which makes their construction more difficult for the beginning DIYer. I advise that you don't attempt to build these systems, unless you're certain that the T/S parameters for the driver that you want to use are correct. </strong></p><p></p><p><strong> </strong></p><p></p><p><strong>Almost any driver can be used in a ported enclosure system, however, only drivers which have a Qts value between 0.2 to 0.5 will generally give satisfactory results. If the driver has a Qts above 0.4, try using it in a sealed enclosure or single reflex bandpass system instead. </strong></p><p></p><p>....</p><p></p><p>The first thing you have to do is pick woofers and model them in ported boxes</p><p></p><p>to see what the response is for various tunings because you may find out that you may not achieve</p><p></p><p>your goal... Also room acoustics will play a role that the common modeling software doesn't account for</p><p></p><p>and most people will eventually EQ their subwoofers after taking in-room measurements. So, don't</p><p></p><p>make plans unless you 'run the numbers' because you may want to buy a Ford F250, do some mods, and it will handle like</p><p></p><p>a Porsche? and accellerate like a bullet ? ... /hehe</p><p></p><p>If you are serious about audio the woofer system should be two part. The subwoofer system tuned low and crossed over low, perhaps low</p><p></p><p>pass 40hz - 60hz and the second woofer would be bandpassed from 40/60hz to whereever your midrange is. The subwoofer should be</p><p></p><p>of 'monster' high excursion variety and the regular woofer should be chosen for better SQ at the higher frequencies {think bass guitar reproduction}.</p><p></p><p>If you mains are good and powerful then you don't need the two part design, but mains with small drivers {unless arrayed} won't give you</p><p></p><p>the bass guitar punch you want.</p></blockquote><p></p>
[QUOTE="thylantyr, post: 1320624, member: 560358"] [URL="http://www.diysubwoofers.org/prt/"]http://www.diysubwoofers.org/prt/[/URL] snip; [B]A ported enclosure system consists of a driver mounted on one side of a box that has an open tunnel or port which allows the passage of air in and out of the box. At low frequencies, the vent contributes substantially to the output of the system. [/B] Ported boxes can be more efficient than a sealed box, a bonus if you want more SPL. [B]The ported enclosure system is characterised by lower distortion and higher power handling in the system's operating range, and lower cutoff frequency than a sealed enclosure system using the same driver.[/B] Some woofers are better suited for sealed box, some are better for ported box, you have to model the woofer to see how it might perform. A woofer designed for a ported box will have a lower cutoff frequency than the same woofer in a sealed box so you get more lower end bass. [B] Distortion rapidly increases below the cutoff frequency however as the driver becomes unloaded[/B] When you play frequencies below tuning the woofer cone can go into higher excursion causing woofer damage and/or nasty distortion. That's why a good design will use a subsonic filter and people try to tune as low as the design allows to cover the 20hz and up range. Some folks try to tune lower down to 17hz if the woofer/design allows. This doesn't mean 20hz tuning is worse than 17hz, can you really notice a difference of 3hz for a single woofer system? Most recorded music is 35hz and up, the 17hz - 20hz is recommended for HT because movies are recorded with low frequency 'special effects', but because you are tuned low doesn't mean the music will suffer. [B]and the transient response of a ported enclosure system is usually inferior to that of a sealed enclosure system using the same driver.[/B] This is true but over-rated, if you design a good ported box it will perform well and you may never prefer a sealed box version of the same woofer. [B]However, the lower cutoff frequency and better power handling within the system's passband often makes ported systems the alignment of choice for many speaker builders. [/B] Subjective [B]Ported enclosure systems are much more sensitive to misaligned parameters than sealed enclosure systems, which makes their construction more difficult for the beginning DIYer. I advise that you don't attempt to build these systems, unless you're certain that the T/S parameters for the driver that you want to use are correct. [/B] [B] [/B] [B]Almost any driver can be used in a ported enclosure system, however, only drivers which have a Qts value between 0.2 to 0.5 will generally give satisfactory results. If the driver has a Qts above 0.4, try using it in a sealed enclosure or single reflex bandpass system instead. [/B] .... The first thing you have to do is pick woofers and model them in ported boxes to see what the response is for various tunings because you may find out that you may not achieve your goal... Also room acoustics will play a role that the common modeling software doesn't account for and most people will eventually EQ their subwoofers after taking in-room measurements. So, don't make plans unless you 'run the numbers' because you may want to buy a Ford F250, do some mods, and it will handle like a Porsche? and accellerate like a bullet ? ... /hehe If you are serious about audio the woofer system should be two part. The subwoofer system tuned low and crossed over low, perhaps low pass 40hz - 60hz and the second woofer would be bandpassed from 40/60hz to whereever your midrange is. The subwoofer should be of 'monster' high excursion variety and the regular woofer should be chosen for better SQ at the higher frequencies {think bass guitar reproduction}. If you mains are good and powerful then you don't need the two part design, but mains with small drivers {unless arrayed} won't give you the bass guitar punch you want. [/QUOTE]
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