when a sealed box is better than vented? |
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app
Old Croc Joined: 26 December 2013 Location: Finland Status: Offline Points: 2435 |
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They are the hf These are the drivers http://www.fane-international.com/prod_details.aspx?pid=415 The sealed 12" are playing from about 100hz to 17k. |
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"what!?"
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Online Points: 3118 |
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I'm confused about sealed alignments. Alignment tables say that when Ql
is lower that alpha is lower - resulting in a larger Vb (Vas/alpha).
1/Qb=1/Ql + 1/Qa + 1/Qp but as Ql is the dominant term the tables refer
to Ql rather than Qb - right?
But, when people add stuffing to a box (lowering Qa) they say you can use a smaller box. How is this when Ql and Qa have an identical position in the formula for 1/Qb above? PP |
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_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
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Stuffing is a straight loss, lowering Qtc of the box.
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djk
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Online Points: 3118 |
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that's the bit that makes sense to me - adding stuffing lowers Qtc and increases the effective Vb. what I don't get is why a leaky box doesn't do the same. Losses from air leaks must surely lower Q and in the extreme a very leaky box is equivalent to an infinitely large box - isn't it? |
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odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5483 |
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I guess the answer is probably in the equivalent lumped circuit model of the box. A leak from box to air will be in parallel with the driver front to rear, whereas stuffing is dissipation of energy internal to the enclosure. Then as usual it all comes out in the maths. Modelling a sealed box is always the easiest place to start deriving a transfer function.
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