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Old 9th April 2012, 06:43 PM   #41
chrisb is offline chrisb  Canada
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I've not been exposed directly to this concept: is it where the any two tangents of the curve cannot cross beneath the curve?

ie, dy/dx > 0 below the rolloff frequency.

not cross the line more than once, I think is what Dave means - as shown in the shallow dip then pronounced hump just before roll-off
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Old 9th April 2012, 06:49 PM   #42
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would I be going too far ahead to start building the cabs for the super pencil while awaiting these new 12.2p's?
I have drawn the new plans. Once vetted by Scott, you can email me for them in the short-term, in the long run the planet10-hifi box library is being moved to a new non-commercial site -- frugal-phile.com (so that i can post links to plans on audio circle)

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Old 9th April 2012, 06:51 PM   #43
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not cross the line more than once, I think is what Dave means - as shown in the shallow dip then pronounced hump just before roll-off
exactly. Take the derivative of the frequency magnitude wrt frequncy dm/df. It should cross zero at most once.

dave
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Old 9th April 2012, 09:39 PM   #44
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so...If i understand correctly, the super pencil would be the way to go?
No. Please see my previous posts. Neither of the existing boxes are ideal for the A12.2; you can use it in them if you have a pair to hand, but I do not advise building them for the new unit. There is a dedicated box for the 12.2.

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Old 9th April 2012, 10:41 PM   #45
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No. Please see my previous posts. Neither of the existing boxes are ideal for the A12.2; you can use it in them if you have a pair to hand, but I do not advise building them for the new unit. There is a dedicated box for the 12.2.
Seconded. From last Friday's listening session, the existing Pensil 12 box is a little restrictive. We'll play with the damping this Saturday to see if we can improve the sound. Pensils are simple boxes to make so its worth investing in a new build where possible.

Cheers
Mark.
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Old 10th April 2012, 12:08 AM   #46
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Seconded. From last Friday's listening session, the existing Pensil 12 box is a little restrictive. We'll play with the damping this Saturday to see if we can improve the sound. Pensils are simple boxes to make so its worth investing in a new build where possible.

Cheers
Mark.
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Old 10th April 2012, 03:23 AM   #47
chrisb is offline chrisb  Canada
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No. Please see my previous posts. Neither of the existing boxes are ideal for the A12.2; you can use it in them if you have a pair to hand, but I do not advise building them for the new unit. There is a dedicated box for the 12.2.


what took so long? , and where are the drawings


oh, now I've asked for it
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Old 10th April 2012, 09:53 AM   #48
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That curve violates my zero crossing critria, so i'd never go there.

The rule is intended to maintain bass quality over quantity in a reflex box.

dave
Dave, since you previously mentioned "derivative", I think you mean that you can have not more than 1 peak or minimum in the graph (the derivative of a function crosses 0 there). Is that a correct interpretation of your feedback?
In this case you indeed have a small hump and a minimum in the hollow at the right of it.

In my very humble experience, I have a similar small, not overly peaky hump in the alignment of current my main speakers (based on the Beyma 8BX coaxial speaker), and honestly it handles the bass remarkably well without obvious "quantity over quality" issues (which I am well prepared to believe that you can have audibly when there is a big sharp hump). So I wonder, would my simulation really be a bad alignment for this FR driver?

Tom
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Old 10th April 2012, 06:48 PM   #49
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Dave, since you previously mentioned "derivative", I think you mean that you can have not more than 1 peak or minimum in the graph (the derivative of a function crosses 0 there). Is that a correct interpretation of your feedback?
In this case you indeed have a small hump and a minimum in the hollow at the right of it.
Yes.

dave
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Old 10th April 2012, 08:30 PM   #50
chrisb is offline chrisb  Canada
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what took so long? , and where are the drawings


oh, now I've asked for it
saw the preliminary sketch last night - not tiny these
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