OB speaker question

kendt · 15th March 2012, 11:25 PM

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?

fastbike1 · 16th March 2012, 02:44 AM

Two in parallel are +6dB. You need to think of the two woofers are a single unit.

Quote:

Originally Posted by kendt

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?

Klimon · 16th March 2012, 09:40 PM

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

chris661 · 16th March 2012, 10:30 PM

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

Klimon · 16th March 2012, 10:58 PM

Quote:

Originally Posted by chris661

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

sreten · 16th March 2012, 11:16 PM

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.

Klimon · 11:31 PM

Quote:

Originally Posted by sreten

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

Rudolf · 16th March 2012, 11:48 PM

Quote:

Originally Posted by kendt

MJK's papers state a midrange driver should be 6-10 dbs lower in spl than the woofer.

Quote:

Originally Posted by Klimon

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

Klimon · 16th March 2012, 11:51 PM

http://www.quarter-wave.com/OBs/OB_Design.pdf

Page 15

Simon

sreten · 11:59 PM

Quote:

Originally Posted by Klimon

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.

15th March 2012, 11:25 PM	#1
kendt diyAudio Member Join Date: Dec 2006	OB speaker question 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?

16th March 2012, 11:16 PM	#6
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	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. __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

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16th March 2012, 09:40 PM	#3
Klimon diyAudio Member Join Date: Apr 2005 Location: Leuven	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

16th March 2012, 10:30 PM	#4
chris661 diyAudio Member Join Date: Feb 2008 Location: Sheffield Blog Entries: 8	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

16th March 2012, 11:51 PM	#9
Klimon diyAudio Member Join Date: Apr 2005 Location: Leuven	http://www.quarter-wave.com/OBs/OB_Design.pdf Page 15 Simon