Reply to thread

Message

<blockquote data-quote="stones" data-source="post: 1004538" data-attributes="member: 540734">To tell if they are blown-1- If the voice coil is scorched or burned the will cut in and out or not play at all.2- If the spider has torn loose from the neck of the cone or the basket, you can tell this by a close visual inspection on the back of the woofer, gently move the cone up and down and search for any torn areas on the spider (that ribbed cloth thing the cone is connected to). A damaged spider can cause rattles.Another cause for rattles, if you have loosley mounted your subs and air is leaking out around the mounting diameter or any holes in the box (not ports thats different)The subs will bottom out easily as they have no acoustic suspention due to the leaks. A sealed box must be airtight.Ported boxes take the backwave of the sub and change it to add to the front wave of the sub, if you play a sub with no enclosure at all it will make no sound because the backwave will cancel out the frontwave, a port will change the wavelenght of the backwave so it doesnt cancel out the frontwave.Ported boxes are generally louder then sealed due to the extra air movment from the port. the extra volume is at the expense of a larger enclosure and slightly less accurate sound. the port provides acoustic suspention to the sub by restricting airflow at certain frequencys, the most restriction happening at the ports tuning frequency, below the ports tuning frequency the port no longer provides acoustic suspention and allows the sub to play without resistance, this is why some amps have subsonic filters to cut out these ultra low frequencys below tuning.More info-4.4.2&nbsp; Sealed Box-----------------*&nbsp; &nbsp; Advantages...-&nbsp; &nbsp; &nbsp;&nbsp; Small enclosure volumes-&nbsp; &nbsp; &nbsp;&nbsp; Shallow (12 dB/Octave) roll off on low end-&nbsp; &nbsp; &nbsp;&nbsp; Excellent power handling at extremely low frequencies-&nbsp; &nbsp; &nbsp;&nbsp; Excellent transient response/ group delaycharacteristics-&nbsp; &nbsp; &nbsp;&nbsp; Easy to build and design-&nbsp; &nbsp; &nbsp;&nbsp; Forgiving of design and construction errors*&nbsp; &nbsp; Disadvantages...-&nbsp; &nbsp; &nbsp;&nbsp; Not particularly efficient-&nbsp; &nbsp; &nbsp;&nbsp; Marginal power handling in upper bass frequencies-&nbsp; &nbsp; &nbsp;&nbsp; Increased distortion in upper bass over ported design-&nbsp; &nbsp; &nbsp;&nbsp; When using high power and small box, magnet structureis not in an ideal cooling environment4.4.3&nbsp; Ported Box-----------------*&nbsp; &nbsp; Advantages...-&nbsp; &nbsp; &nbsp;&nbsp; 3-4 dB more efficient overall than sealed design-&nbsp; &nbsp; &nbsp;&nbsp; Handles upper bass frequencies better with lessdistortion-&nbsp; &nbsp; &nbsp;&nbsp; Magnet is in good cooling environment-&nbsp; &nbsp; &nbsp;&nbsp; When properly designed, a ported box will slaughter asealed in terms of low frequency extension*&nbsp; &nbsp; Disadvantages...-&nbsp; &nbsp; &nbsp;&nbsp; Size (not so critical outside the mobile environment)-&nbsp; &nbsp; &nbsp;&nbsp; Woofer unloads below Fb-&nbsp; &nbsp; &nbsp;&nbsp; More difficult to design/ can result in boomy, nastysounding bass if misaligned</blockquote>

[QUOTE="stones, post: 1004538, member: 540734"] To tell if they are blown- 1- If the voice coil is scorched or burned the will cut in and out or not play at all. 2- If the spider has torn loose from the neck of the cone or the basket, you can tell this by a close visual inspection on the back of the woofer, gently move the cone up and down and search for any torn areas on the spider (that ribbed cloth thing the cone is connected to). A damaged spider can cause rattles. Another cause for rattles, if you have loosley mounted your subs and air is leaking out around the mounting diameter or any holes in the box (not ports thats different) The subs will bottom out easily as they have no acoustic suspention due to the leaks. A sealed box must be airtight. Ported boxes take the backwave of the sub and change it to add to the front wave of the sub, if you play a sub with no enclosure at all it will make no sound because the backwave will cancel out the frontwave, a port will change the wavelenght of the backwave so it doesnt cancel out the frontwave. Ported boxes are generally louder then sealed due to the extra air movment from the port. the extra volume is at the expense of a larger enclosure and slightly less accurate sound. the port provides acoustic suspention to the sub by restricting airflow at certain frequencys, the most restriction happening at the ports tuning frequency, below the ports tuning frequency the port no longer provides acoustic suspention and allows the sub to play without resistance, this is why some amps have subsonic filters to cut out these ultra low frequencys below tuning. More info- 4.4.2 Sealed Box ----------------- * Advantages... - Small enclosure volumes - Shallow (12 dB/Octave) roll off on low end - Excellent power handling at extremely low frequencies - Excellent transient response/ group delay characteristics - Easy to build and design - Forgiving of design and construction errors * Disadvantages... - Not particularly efficient - Marginal power handling in upper bass frequencies - Increased distortion in upper bass over ported design - When using high power and small box, magnet structure is not in an ideal cooling environment 4.4.3 Ported Box ----------------- * Advantages... - 3-4 dB more efficient overall than sealed design - Handles upper bass frequencies better with less distortion - Magnet is in good cooling environment - When properly designed, a ported box will slaughter a sealed in terms of low frequency extension * Disadvantages... - Size (not so critical outside the mobile environment) - Woofer unloads below Fb - More difficult to design/ can result in boomy, nasty sounding bass if misaligned [/QUOTE]

Verification