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Playing lower than fb in a sealed box.

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  • Playing lower than fb in a sealed box.

    In a sealed box it seems that the fb can't always reach down to about 40hz(although I have one set of subs that easily do), so lets say for arguments sake the fb is around 58hz but the fs of the driver is 30hz what happens under the 58hz if I was to boost it with DSP?

    Is there more likely to be distortion under the 58hz?

    And most importantly how do I know the driver can handle it? What parameters do I look at?


  • #2
    Model the speaker, look at the excursion plot at the power level you intend to run. EQ doubles the power for each 3dB of boost. Where excursion exceeds xmax THD will be very high.
    www.billfitzmaurice.com
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    • #3
      Originally posted by billfitzmaurice View Post
      Model the speaker, look at the excursion plot at the power level you intend to run. EQ doubles the power for each 3dB of boost. Where excursion exceeds xmax THD will be very high.
      That is great, so basically I look at what point excursion exceeds xmax. Thanks.

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      • #4
        Now, I have read in another thread where you have dismissed any company who doesn't know there parameters or the xmax of their driver and products and that its probably due to them not being the manufacturer. But, nearly every Chinese manufacture of speaker drivers who provides all the parameters never has xmax. Could there be any reason for this?

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        • #5
          Originally posted by Trdat View Post
          Now, I have read in another thread where you have dismissed any company who doesn't know there parameters or the xmax of their driver and products and that its probably due to them not being the manufacturer. But, nearly every Chinese manufacture of speaker drivers who provides all the parameters never has xmax. Could there be any reason for this?
          Xmax is pretty basic. If they don't have that I'd doubt the accuracy of the other T/S parameters.

          To directly answer your question, the magnet is probably tiny and inexpensive, so Xmax is small. Best not to even mention it.
          Francis

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          • #6
            Originally posted by Trdat View Post
            nearly every Chinese manufacture of speaker drivers who provides all the parameters never has xmax. Could there be any reason for this?
            There's no good reason for it. Not listing the xmax of a driver is the equivalent of selling a car without listing the displacement of the engine.

            www.billfitzmaurice.com
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            • #7
              Originally posted by billfitzmaurice View Post
              There's no good reason for it. Not listing the xmax of a driver is the equivalent of selling a car without listing the displacement of the engine.
              Not to nit pick Bill, but engine displacement doesn't mean much any more. Used to be that getting 100HP/liter was pretty good. Nowadays, not so much...

              But your point is valid. If they don't list Xmx it's probably because it's nothing to be proud of.

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              • Kornbread
                Kornbread commented
                Editing a comment
                Modern sportbikes are reaching near the 200hp/liter level.

            • #8
              Its interesting even when you contact the manufacturer, they send you all the parameters which excludes xmax.

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              • #9
                Who's the manufacturer?
                www.billfitzmaurice.com
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                • #10
                  Originally posted by Trdat View Post
                  Its interesting even when you contact the manufacturer, they send you all the parameters which excludes xmax.
                  I'd say that's a sure sign they don't make a quality product. Some people don't care about xmax, but then some people are perfectly happy with terrible distortion, too.
                  Francis

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                  • #11
                    They may make a quality product. Around 2004 I was approached by Celestion to recommend some of their drivers in my DIY designs. I replied that I might do so if they had drivers with the requisite T/S specs. They didn't have any. At that time they were still providing only inches and watts, which was typical of musical instrument driver manufacturers in the 80s-90s. As I recall Eminence was producing data sheets by 1998 or so. I didn't start seeing real data sheets from Celestion until 2008.
                    www.billfitzmaurice.com
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                    • #12
                      Originally posted by billfitzmaurice View Post
                      They may make a quality product. Around 2004 I was approached by Celestion to recommend some of their drivers in my DIY designs. I replied that I might do so if they had drivers with the requisite T/S specs. They didn't have any. At that time they were still providing only inches and watts, which was typical of musical instrument driver manufacturers in the 80s-90s. As I recall Eminence was producing data sheets by 1998 or so. I didn't start seeing real data sheets from Celestion until 2008.
                      Well it's 2021 now, and they sent him other T/S parameters. Something is very fishy.
                      Francis

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                      • #13
                        Without knowing what they are we're at a dead end.
                        www.billfitzmaurice.com
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                        • #14
                          Originally posted by billfitzmaurice View Post
                          They may make a quality product. Around 2004 I was approached by Celestion....
                          is there a post/reply from OP that's gone missing? How do you all know we're talking about Celestion here??

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                          • #15
                            I didn't say the OP was talking about Celestion.
                            www.billfitzmaurice.com
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