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<blockquote data-quote="Martyn ferrit Rowe" data-source="post: 122131" data-attributes="member: 379">Re: Stair Cardioid Subwoofer ArrayHey Gang,So where is the &quot;Acoustic center&quot;? Let&#039;s define it as the physical point from which the acoustic propagation emanates including the phase.This definition is valid up to those frequencies where the acoustic wavelength is large compared to the cabinet size.If we use a simple point source model to predict the LF acoustic radiation of an array of enclosures we need to know where this is.General thought has put this position at the center of the piston, perhaps where the cone apex meets the voice coil?It might come as a surprise to some that in actual fact it is situated some distance in front of the enclosure, in the case of the MLX subwoofer its actually 50cm in front!As the frequency increases it moves in towards the enclosure, but as far as LF is concerned we can say it remains in place.If this &quot;offset&quot;is not taken into account, quite large errors, in the order of 20dB, can result in the predictions. &lt;yikes!&gt;In answer to the question on endfire and Cardioid setups some preliminary work has been done.cheersferrit</blockquote>

[QUOTE="Martyn ferrit Rowe, post: 122131, member: 379"] Re: Stair Cardioid Subwoofer Array Hey Gang, So where is the "Acoustic center"? Let's define it as the physical point from which the acoustic propagation emanates including the phase. This definition is valid up to those frequencies where the acoustic wavelength is large compared to the cabinet size. If we use a simple point source model to predict the LF acoustic radiation of an array of enclosures we need to know where this is. General thought has put this position at the center of the piston, perhaps where the cone apex meets the voice coil? It might come as a surprise to some that in actual fact it is situated some distance in front of the enclosure, in the case of the MLX subwoofer its actually 50cm in front! As the frequency increases it moves in towards the enclosure, but as far as LF is concerned we can say it remains in place. If this "offset"is not taken into account, quite large errors, in the order of 20dB, can result in the predictions. <yikes!> In answer to the question on endfire and Cardioid setups some preliminary work has been done. cheers ferrit [/QUOTE]

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