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Old 12th November 2012, 06:17 PM   #11
Davey is offline Davey  United States
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Technically, you are correct. But, I'm just saying, the Orion uses only a 6db/octave shelving filter for Q "correction" in the ASP architecture.

You're probably confused because of the ASP capabilities. The ASP circuit board design does allow you to implement a full bi-quad (LT) stage, if needed for some other usage. But it is not configured that way in the Orion design.

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Old 12th November 2012, 06:34 PM   #12
sreten is offline sreten  United Kingdom
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Hi,

An LT is basically inversely correcting a high Q sealed box response and
then arranging an alternative bass roll off. There is no LT involved here.
Its just simply EQ as bass boost to alter the bass roll-off.

rgds, sreten.
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Old 12th November 2012, 06:40 PM   #13
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http://www.linkwitzlab.com/images/gr...orion-asp2.jpg

Is what I am referring to, where clearly an LT is used on the woofers along with a shelving section.
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Old 12th November 2012, 06:45 PM   #14
Davey is offline Davey  United States
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I'm not going to argue with you about it.

The U11B stage is just a simple 6db/octave shelving circuit.
You're talking to a fella who has a pretty good working knowledge of the Orion ASP configuration.

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Dave.
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Old 12th November 2012, 06:49 PM   #15
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by 5th element View Post
http://www.linkwitzlab.com/images/gr...orion-asp2.jpg

Is what I am referring to, where clearly an LT is used on the woofers along with a shelving section.
Hi, one simple part of a LT does not make a complete LT, rgds, sreten.
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Old 12th November 2012, 06:54 PM   #16
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Quote:
Originally Posted by 5th element View Post
http://www.linkwitzlab.com/images/gr...orion-asp2.jpg

Is what I am referring to, where clearly an LT is used on the woofers along with a shelving section.
While labeled LT2, it is not an LT. It is a 20-110 1st order shelf. That is, the gain is 110/20 and the poles are at 20 and 110 Hz. The way this is done with the original woofers is that the 20-110 shelf shifts the low Q pole at 110 Hz to 20 Hz. Dipole EQ would in theory extend from 305 Hz to DC. However there is also another (stealth) shelf to shift the woofer pole below 20 Hz up to 20 Hz. This shelf would be a cut, not a boost. As I recall it would have poles at about 5 Hz and 20 Hz. But this pole shifter is the inverse of the dipole eq below 20 Hz so by stopping the dipole eq at 20 the second pole shifter can be omitted and the same result is achieved down to 5 Hz. Below 5 Hz the woofer would roll off 3rd order.
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Old 12th November 2012, 07:04 PM   #17
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That's interesting as LW himself describes the LT2 circuit as a 12dB/oct biquad which is clearly not a simple shelving network. On his website he also describes how one can compensate for a low Q woofer on an OB by using a special biquad circuit, which links to the LT with a description of how to use it.

LW may have used different filters that arrive at the same end result, but it is certainly misleading for him to write two things that indicate that an LT is used and then to not actually use one.
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Old 12th November 2012, 07:31 PM   #18
Davey is offline Davey  United States
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He's not misleading anyone.

The designations on the block diagram you posted are correct. Items in parentheses are capabilities the ASP circuit boards have, but that are not used in the Orion design. You'll note there are others as well.....such as a 200Hz notch filter in the woofer circuit. There is no 200Hz notch filter in the Orion design, but the boards have the capability to implement one should an experienced user/designer be using them for some other purpose.

Dave.
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Old 12th November 2012, 07:46 PM   #19
dewardh is offline dewardh  United States
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Quote:
Originally Posted by rich31td View Post
Rather than correct for the dipole roll off, could I just let the midrange roll off naturally and apply low pass LR2 to the woofer at 100hz?
Or am I missing something vital?
Missing something vital. Unlike a sealed box that falling acoustic output doesn't mean excursion is falling.
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Old 13th November 2012, 12:56 PM   #20
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Originally Posted by dewardh View Post
Missing something vital. Unlike a sealed box that falling acoustic output doesn't mean excursion is falling.
I have given up on that idea as I got confused with dipole roll off.

Surely cone excursion is a limiting factor in all dipole/open baffle designs?

Even if the Orion doesn't use any LT, using this wouldn't pose any problems in my design?
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