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PM DIY Baffle Step
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<blockquote data-quote="Peter Morris" data-source="post: 213272" data-attributes="member: 652"><p>Yes we do have a good idea of its vertical and horizontal directivity. In fact the dipole arrangement and crossover point was designed with that in mind - to control the vertical directivity down to quite a low frequency. Lots and lots of off axis responses were measured.</p><p></p><p>Below is the directivity plot of a box that should be similar down to about 700Hz after which the DIY vertical directivity is is estimated (red line)</p><p></p><p>As I said above, if you want more SPL in the low frequencies then I believe you are better to make the horn bigger rather than adding a baffle.</p><p></p><p>You get the advantage of better directivity in the low frequencies AND the longer horn which will give you better horn loading of the lower frequencies .... model it in HornResp and you will see what I mean ... may be as much as 6 - 10 dB at 100Hz by increasing the horn length by 30cm, BUT the box becomes much bigger and not pole mountable. </p><p></p><p>Also don't forget that the DIY was designed to be crossed at 100Hz, at which point the directivity of the sub / bass bin comes into play.</p><p></p><p>You talked about putting 6" driver together .... yes they will sum but you need to have a look at what happens to the polar's as the frequency goes up beyond about 1000 - 1500 Hz <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite13" alt=":cautious:" title="Cautious :cautious:" loading="lazy" data-shortname=":cautious:" /></p></blockquote><p></p>
[QUOTE="Peter Morris, post: 213272, member: 652"] Yes we do have a good idea of its vertical and horizontal directivity. In fact the dipole arrangement and crossover point was designed with that in mind - to control the vertical directivity down to quite a low frequency. Lots and lots of off axis responses were measured. Below is the directivity plot of a box that should be similar down to about 700Hz after which the DIY vertical directivity is is estimated (red line) As I said above, if you want more SPL in the low frequencies then I believe you are better to make the horn bigger rather than adding a baffle. You get the advantage of better directivity in the low frequencies AND the longer horn which will give you better horn loading of the lower frequencies .... model it in HornResp and you will see what I mean ... may be as much as 6 - 10 dB at 100Hz by increasing the horn length by 30cm, BUT the box becomes much bigger and not pole mountable. Also don't forget that the DIY was designed to be crossed at 100Hz, at which point the directivity of the sub / bass bin comes into play. You talked about putting 6" driver together .... yes they will sum but you need to have a look at what happens to the polar's as the frequency goes up beyond about 1000 - 1500 Hz :cautious: [/QUOTE]
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