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Old 11th December 2012, 08:26 AM   #531
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Maybe, but EQ is required anyway.

We used two Beyma 18" with Fs=37 Hz and Qts=0.34
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Old 11th December 2012, 08:42 AM   #532
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Maybe NP would shear measures and info about the new slot loaded open baffle? :-)

What is the ideal listening distance, is around 3 meter ok?

As far as i can see the fullrange is a Lowther PM6A and the woofer a Eminence DEFINIMAX 4015LF 15"?
And they are divided with a B5 active crossover? With slopes, fq and baffle step corrected at?

Correct mee if i am wrong :-)

THX in advance

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Last edited by superlian; 11th December 2012 at 08:56 AM. Reason: inserted picture
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Old 11th December 2012, 08:56 AM   #533
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Key T/S parameters of the 4015LF is:
Fs = 42 Hz
Qts = 0.5

That is not too far from the Beyma 18" we used in our experiment.
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Old 11th December 2012, 09:07 AM   #534
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Quote:
Originally Posted by markus76 View Post
The driver parameters probably didn't match the requirements for such a design.
I looked over the original article by NP linked on page 1 here. It is also about 30 dB down at 20 Hz without EQ.
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Old 11th December 2012, 09:38 AM   #535
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Quote:
Originally Posted by StigErik View Post
Maybe, but EQ is required anyway.

We used two Beyma 18" with Fs=37 Hz and Qts=0.34
Qts should be about 0.5. With the right parameter set one probably can get away with a simple low pass filter. Let's wait and see how the SLS-12 Ripole turns out.
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Old 12th December 2012, 07:43 PM   #536
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What is the tradeoff for theese designs?

I am particular thinking about:

1) The horisontal slot down on the floor (A)
2) Open or closed rear side of the woofer (B&D vs C&E)
3) Standing (F) vs symetric/mirrored (G) use of 2 woofers


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Old 13th December 2012, 03:24 AM   #537
Octavia is offline Octavia  United States
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Actually the Lowther was a special field coil driver that was xo at 160Hz @ 12dB and the bass driver was Eminence Definimax 4015LF xo @ 80dB also with a 12dB slope. I'm pretty sure there were some additional adjustments to make the Lowther sing and not shout. I loved the sound of the set up, clean and clear whether in the front row or in back. This one along with Linkwitz set up were the highlights of the day for me.
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Old 13th December 2012, 08:35 AM   #538
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Despite all the meanings around dipol peak and uneven f.r. with open baffles NP use a standard method with several designs (after what i have read and some suggestions from NP on email). It is mentioned in the article, and it also works for me with my B5 and Fostex FE203En-S:

It's easier to use an active crossover when you want quick results. You just adjust the
crossover filters, measure, listen, and then repeat the process until you're happy. It did not
take me long to get good results because the mating of the woofer and tweeter were well
behaved. I used a 2 pole low pass filter for the bottom at 80 Hz and a 2 pole high pass filter
at 160 Hz, and because I am lucky the proper response was with both drivers in phase.
Some equalization was called for on both drivers. The woofer received a high Q high pass
filter at 20 Hz which removed subsonics and gave the response a 6 dB bump up at 20 Hz.
The Lowther enjoys 4 dB of step correction above 2 Khz or so to take down the overall top
end. If you are a little off-axis, you might decide that 2 dB is better.

Last edited by superlian; 13th December 2012 at 08:38 AM.
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Old 18th December 2012, 02:11 AM   #539
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The actual step of the Lowthers in practice is -2dB. The -4 dB figure gives the
flattest response on axis.

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Old 19th December 2012, 03:51 AM   #540
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Quote:
Originally Posted by Nelson Pass View Post
The actual step of the Lowthers in practice is -2dB. The -4 dB figure gives the
flattest response on axis.

Can you tell us anything helpful in regards to your bottom slot baffles you had this year at Burning Amp? I'm tempted to try these, but also considering h frames, mainly due to my lack of knowledge regarding the single woofer slot loading. I am tempted to use Eminence Beta 15 over the Alpha, and feel if that's the case, they will lend themselves better to the slot vs h frame, as my understanding is that the slot loading will raise q slightly. Is that correct? As well, what effect do the side "wings" have on the woofer, or do they just support the baffle face?
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