OB speaker question

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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?
 
Two in parallel are +6dB. You need to think of the two woofers are a single unit.

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?
 
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 :confused:

Simon
 
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
 
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
 
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.
 
Last edited:
The original (and full!!) statement of MJK is
My recommendation is to use woofer drivers that are at least 6 to 10 dB more efficient than the rest of the speaker system and having Qts values between 1.0 and 1.2
Qts defines the efficiency loss (in dB) of a driver at its Fs compared to the driver efficiency in its "flat" region. This need not include 1 kHz. With that in mind MJKs recommendation is absolutely reasonable.
If manufacturers "cheat" by moving 1 kHz into some brakeup mode (and thereby pushing nominal efficiency up), it is up to the user to recognise that IMHO.

Rudolf
 
Wow,i thought open baffle,s were supposed to be the easiest to impliment.It seems the more i read the more complicated it gets.
Everything tends to become more complicated, the more one reads about it. ;)
At the moment I'm reading about sound localization - with every next page I turn, I wonder more how stereo can work at all. :D

But getting serious: If you are free to change the size of your OB and the position of the driver on that OB at will, you can distort this driver's response more than would be possible with any box.

Rudolf
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.