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Old 16th March 2012, 12:25 AM   #1
kendt is online now kendt  Canada
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I was wondering what two bass drivers would do to the over all efficiancy over one driver.MJK's papers state a midrange driver should be 6-10 dbs lower in spl than the woofer. If two woofers are used does that still apply or does the midrange driver need to have higher spl than a single woofer design?
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Old 16th March 2012, 03:44 AM   #2
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Two in parallel are +6dB. You need to think of the two woofers are a single unit.

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Originally Posted by kendt View Post
I was wondering what two bass drivers would do to the over all efficiancy over one driver.MJK's papers state a midrange driver should be 6-10 dbs lower in spl than the woofer. If two woofers are used does that still apply or does the midrange driver need to have higher spl than a single woofer design?
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Old 16th March 2012, 10:40 PM   #3
Klimon is offline Klimon  Belgium
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Must add that, although MJK's work looks otherwise quite well-documented, he states 98db as efficiency for alpha 15 (following mfr) which is even optimistic at 1k... At the intended range it looks more like 88db on the FR graph. Hope he didn't take such reasoning as basis for his X-db rule...

Correct me if I'm missing something

Simon
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Old 16th March 2012, 11:30 PM   #4
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The graphs on the Eminence 'site are taken from an infinite baffle.
Problem is that the open baffle will drop bass efficiency for fun. A longer front-back path preserves more of the LF energy, so there is no definite efficiency for a bass driver on an open baffle.

Chris
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Old 16th March 2012, 11:58 PM   #5
Klimon is offline Klimon  Belgium
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Originally Posted by chris661 View Post
The graphs on the Eminence 'site are taken from an infinite baffle.
Problem is that the open baffle will drop bass efficiency for fun. A longer front-back path preserves more of the LF energy, so there is no definite efficiency for a bass driver on an open baffle.

Chris
Agreed, but that's still another issue. If MJK takes an erroneous baseline efficiency, how can the resulting rule of thumb for midrange/bass efficiency be correct?

Simon
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Old 17th March 2012, 12:16 AM   #6
sreten is offline sreten  United Kingdom
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Hi, MJK is not remotely stupid, and things are as he states, rgds, sreten.

All driver sensitivities discussed are into half space and are also relative.
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Old 17th March 2012, 12:29 AM   #7
Klimon is offline Klimon  Belgium
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Hi, MJK is not remotely stupid, and things are as he states, rgds, sreten.
Simply wondering why he seems to quote efficiency specs that are way off in the used range, and if the rule of thumb is based on these. Correct me if I'm wrong, but preferably with arguments and not with a logical fallacy

Best,

Simon

Last edited by Klimon; 17th March 2012 at 12:31 AM. Reason: World peace
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Old 17th March 2012, 12:48 AM   #8
Rudolf is online now Rudolf  Germany
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Quote:
Originally Posted by kendt View Post
MJK's papers state a midrange driver should be 6-10 dbs lower in spl than the woofer.
Quote:
Originally Posted by Klimon View Post
If MJK takes an erroneous baseline efficiency, how can the resulting rule of thumb for midrange/bass efficiency be correct?
Can one of you lead me to the paper, where this "rule of thumb" is stated by MJK?

Rudolf
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Old 17th March 2012, 12:51 AM   #9
Klimon is offline Klimon  Belgium
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http://www.quarter-wave.com/OBs/OB_Design.pdf

Page 15

Simon
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Old 17th March 2012, 12:57 AM   #10
sreten is offline sreten  United Kingdom
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Originally Posted by Klimon View Post
Agreed, but that's still another issue. If MJK takes an erroneous baseline efficiency,
how can the resulting rule of thumb for midrange/bass efficiency be correct?

Simon
Hi, you have yet to show your right and he is wrong, rgds, sreten.

He's slightly out due to Eminence methods, your miles out.
Nothing changes the fundamental premises of his modelling.
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Last edited by sreten; 17th March 2012 at 12:59 AM.
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