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Enclosure Design & Construction
4th Order Bandpass pictures of design... port/sub placement...
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<blockquote data-quote="bbeljefe" data-source="post: 8157294" data-attributes="member: 655960"><p>Success is a subjective term, especially where loudspeakers are concerned. If you're looking for extreme SPL in a narrow bandwidth, then the boxes I've modeled so far would be great. But if you're looking for sound quality (wide passband) then we haven't had any yet.</p><p></p><p><img src="http://i596.photobucket.com/albums/tt42/bbeljefe/AB1544_zpsf1abb231.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>The graph above shows a few boxes I've modeled for the AB driver you selected. The light blue graph is the widest bandwidth possible and is the box WinISD recommends for this driver. It's flat and has a reasonably wide passband but it's -3dB at 29hz, which means it isn't going to be very efficient on the lows. It's also a pretty small box at just over 3 cubes total. Using the same ratio WinISD recommended, I modeled two others (actually, I've modeled about 8) at a lower frequency and larger volumes, with opposite ratios for Fb &amp; Fr. They both slam the low 30s but as you can see, they fall off steep on both ends. The problem here is that this driver has a high EBP (Efficiency Bandwidth Product).</p><p></p><p>EBP is derived by dividing the driver's Fs by its Qes and here's what it tells us:</p><p></p><p>1-50 = Driver should be used in sealed or 4th order box.</p><p></p><p>51-99 = Driver can be used in either sealed/4th order or ported/6th order.</p><p></p><p>100+ = Driver should be used in ported/6th order.</p><p></p><p>That's a rule of thumb I've heard a lot but I've found that drivers above 50 don't usually work well in sealed/4th order alignments. That said, there are other factors so it's not a waste of time to model a driver with an EBP higher than 50. The XFL1544 is at 56 so it should be okay in a 4th. And to clarify, I think I said 74 in another post but clearly, I didn't do my math correctly so, I'm sorry about that confusion.</p><p></p><p>In any event, if 4th order is the best alignment for you, I'd recommend a driver with a low EBP. The TNT1544 has an EBP of 50.8. The XD1544 is 46 and the Sound Qubed Sdc2.5 15 is also 46, so either of those would be a likely choice.</p><p></p><p>Here are those two drivers:</p><p></p><p><img src="http://i596.photobucket.com/albums/tt42/bbeljefe/SQSDC2515ABXD1544_zps73c854aa.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Teal and green graphs are WinISD recommended for the SQ and AB drivers, respectively. Yellow and white are my modeling for them. Each box is:</p><p></p><p>Vf - 3ftⁿ</p><p></p><p>Vr - 6ftⁿ</p><p></p><p>Fb - 36hz</p><p></p><p>Vent = 6" x 14.82"</p><p></p><p>The SQ has a higher acoustical peak (+7dB @ 36) and both hit -3dB at 23hz, so they will play the lows well. The SQ also extends slightly higher than the XD but both of them hit -3dB on the high side at 56hz.</p><p></p><p>If you're looking for loud, I'd go with the SQ but if you're looking for a more smooth response curve, the XD would be better. And, if you're looking for pure sound quality, I'd go with WinISD recommended volumes for either driver. Although, the SQ does extend a bit lower on recommended volume.</p></blockquote><p></p>
[QUOTE="bbeljefe, post: 8157294, member: 655960"] Success is a subjective term, especially where loudspeakers are concerned. If you're looking for extreme SPL in a narrow bandwidth, then the boxes I've modeled so far would be great. But if you're looking for sound quality (wide passband) then we haven't had any yet. [IMG]http://i596.photobucket.com/albums/tt42/bbeljefe/AB1544_zpsf1abb231.png[/IMG] The graph above shows a few boxes I've modeled for the AB driver you selected. The light blue graph is the widest bandwidth possible and is the box WinISD recommends for this driver. It's flat and has a reasonably wide passband but it's -3dB at 29hz, which means it isn't going to be very efficient on the lows. It's also a pretty small box at just over 3 cubes total. Using the same ratio WinISD recommended, I modeled two others (actually, I've modeled about 8) at a lower frequency and larger volumes, with opposite ratios for Fb & Fr. They both slam the low 30s but as you can see, they fall off steep on both ends. The problem here is that this driver has a high EBP (Efficiency Bandwidth Product). EBP is derived by dividing the driver's Fs by its Qes and here's what it tells us: 1-50 = Driver should be used in sealed or 4th order box. 51-99 = Driver can be used in either sealed/4th order or ported/6th order. 100+ = Driver should be used in ported/6th order. That's a rule of thumb I've heard a lot but I've found that drivers above 50 don't usually work well in sealed/4th order alignments. That said, there are other factors so it's not a waste of time to model a driver with an EBP higher than 50. The XFL1544 is at 56 so it should be okay in a 4th. And to clarify, I think I said 74 in another post but clearly, I didn't do my math correctly so, I'm sorry about that confusion. In any event, if 4th order is the best alignment for you, I'd recommend a driver with a low EBP. The TNT1544 has an EBP of 50.8. The XD1544 is 46 and the Sound Qubed Sdc2.5 15 is also 46, so either of those would be a likely choice. Here are those two drivers: [IMG]http://i596.photobucket.com/albums/tt42/bbeljefe/SQSDC2515ABXD1544_zps73c854aa.png[/IMG] Teal and green graphs are WinISD recommended for the SQ and AB drivers, respectively. Yellow and white are my modeling for them. Each box is: Vf - 3ftⁿ Vr - 6ftⁿ Fb - 36hz Vent = 6" x 14.82" The SQ has a higher acoustical peak (+7dB @ 36) and both hit -3dB at 23hz, so they will play the lows well. The SQ also extends slightly higher than the XD but both of them hit -3dB on the high side at 56hz. If you're looking for loud, I'd go with the SQ but if you're looking for a more smooth response curve, the XD would be better. And, if you're looking for pure sound quality, I'd go with WinISD recommended volumes for either driver. Although, the SQ does extend a bit lower on recommended volume. [/QUOTE]
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