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Car Audio Equipment
Subwoofers
Bass Louder and softer sometimes... Bass subwoofer problem - Bass loss
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<blockquote data-quote="Doxquzme" data-source="post: 8848185" data-attributes="member: 689267"><p>I've been building loudspeakers for 40 years, and the way I read the spec sheet, you are about 50L (net) to small on the box for 2 of these 15" woofers. This might sound decent on some playback and not on others, not how it should sound on anything! Gross internal volume for two drivers should be 180L gross (150net) tuned to 60Hz (vb) which will yield a 50hz response (which would be almost 4 octaves down, so I'm not sure what they are telling you there). Given the Vb and the tuning frequency of 60Hz, 57Hz would be your 3db down point, not exactly low in my book but not atypical for a larger driver. You can't just tune a box to your liking, where you think or want it to play; it needs to relate to the specifications of the woofer, the box and the woofer work together. According to the specs you list for the SPL box (the smaller option in this case), you need 180 liters of gross volume (this is the volume before negating the woofer drivers and the port displacement), 75 liters of net volume, or Vb at 75L per chamber (150L net for two drivers), and the port they recommend is 30cm x 12.5cm or 375 square centimeters, for the rectangle port opening with a length of 27.5cm. I didn’t do the conversion from round to rectangle (375sq cm is equal to an 8.25" port, maybe?), but I am guessing the port you are using is completely wrong. The resonant frequency (the point where the woofer vibrates undesirably) for this woofer is 35hz. Unless you are using a subsonic filter crossed at 20Hz, you shouldn’t tune below 35hz. This box does not appear to be correct for two woofers (not even close). The box you have is half the size it needs to be. These woofers are never going to perform correctly in this enclosure. It is important to note, larger woofers do not necessarily and in most cases, do not play as low as 10’s or 12’s usually do, or at all for that matter. 15’s rarely play lower than 12’s, they just move more air (are louder). Try disconnecting one of the woofers, closing up that opening (temporarily) and see if the sound is more to your liking. I think you need to think about starting over on this box. I have BASS box pro and can run the specs if you need, for an extended bass box tuned to 35-40, but it looks like it will be on the order of 6-8 cubic feet given the parameters that I found ( <a href="https://www.carhifitwente.nl//Files/2/37000/37805/Attachments/Product/3m9ky7D682XXT075Y3ZXm6T8mQ9100pf.pdf" target="_blank">https://www.carhifitwente.nl//Files/2/37000/37805/Attachments/Product/3m9ky7D682XXT075Y3ZXm6T8mQ9100pf.pdf</a>), that’s a REAL big box! Thid subwoofer, with a Qts of .83 and an EPB >50 is meant for ported, not sealed enclsures. Stuffing the port will not change this. These woofers are meant to perform best in ported enclosures.</p></blockquote><p></p>
[QUOTE="Doxquzme, post: 8848185, member: 689267"] I've been building loudspeakers for 40 years, and the way I read the spec sheet, you are about 50L (net) to small on the box for 2 of these 15" woofers. This might sound decent on some playback and not on others, not how it should sound on anything! Gross internal volume for two drivers should be 180L gross (150net) tuned to 60Hz (vb) which will yield a 50hz response (which would be almost 4 octaves down, so I'm not sure what they are telling you there). Given the Vb and the tuning frequency of 60Hz, 57Hz would be your 3db down point, not exactly low in my book but not atypical for a larger driver. You can't just tune a box to your liking, where you think or want it to play; it needs to relate to the specifications of the woofer, the box and the woofer work together. According to the specs you list for the SPL box (the smaller option in this case), you need 180 liters of gross volume (this is the volume before negating the woofer drivers and the port displacement), 75 liters of net volume, or Vb at 75L per chamber (150L net for two drivers), and the port they recommend is 30cm x 12.5cm or 375 square centimeters, for the rectangle port opening with a length of 27.5cm. I didn’t do the conversion from round to rectangle (375sq cm is equal to an 8.25" port, maybe?), but I am guessing the port you are using is completely wrong. The resonant frequency (the point where the woofer vibrates undesirably) for this woofer is 35hz. Unless you are using a subsonic filter crossed at 20Hz, you shouldn’t tune below 35hz. This box does not appear to be correct for two woofers (not even close). The box you have is half the size it needs to be. These woofers are never going to perform correctly in this enclosure. It is important to note, larger woofers do not necessarily and in most cases, do not play as low as 10’s or 12’s usually do, or at all for that matter. 15’s rarely play lower than 12’s, they just move more air (are louder). Try disconnecting one of the woofers, closing up that opening (temporarily) and see if the sound is more to your liking. I think you need to think about starting over on this box. I have BASS box pro and can run the specs if you need, for an extended bass box tuned to 35-40, but it looks like it will be on the order of 6-8 cubic feet given the parameters that I found ( [URL]https://www.carhifitwente.nl//Files/2/37000/37805/Attachments/Product/3m9ky7D682XXT075Y3ZXm6T8mQ9100pf.pdf[/URL]), that’s a REAL big box! Thid subwoofer, with a Qts of .83 and an EPB >50 is meant for ported, not sealed enclsures. Stuffing the port will not change this. These woofers are meant to perform best in ported enclosures. [/QUOTE]
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Bass Louder and softer sometimes... Bass subwoofer problem - Bass loss
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