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when a sealed box is better than vented?

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Old Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote app Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2015 at 12:08am
Originally posted by Steve20131 Steve20131 wrote:

Super 4 way, how is it processed?  & app whats on hf?



They are the hf Big smile

These are the drivers http://www.fane-international.com/prod_details.aspx?pid=415

The sealed 12" are playing from about 100hz to 17k.
"what!?"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 09 August 2017 at 5:32pm
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?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2017 at 12:45am
Stuffing is a straight loss, lowering Qtc of the box.
djk
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2017 at 12:18pm
Originally posted by _djk_ _djk_ wrote:

Stuffing is a straight loss, lowering Qtc of the box.


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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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2017 at 2:26pm
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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