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Old 7th January 2011, 04:13 PM   #41
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Your box resonance is 60Hz-ish, there is no way you can EQ to 20Hz, you will have too much gain and the system will be full of hum and unstable, not to mention will only be able to attain quiet listening levels at best.

A true 40Hz response is surprisingly deep for music, I suggest you aim for that with your drive unit and box combination.
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Old 7th January 2011, 04:30 PM   #42
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Default off topic

I have just noticed that posts from the UK stand at 20.
Only two posts are shown as from outside the British Commonwealth.

Co-incidence or ?
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Old 8th January 2011, 05:59 AM   #43
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Quote:
Originally Posted by chris661 View Post
Sounds like you've taken the displacement required into consideration. In that case, experiment with the circuit (try different Q of the response - some say Q=0.5 is better than Q=0.7).
I had noted this on the very day you advised me. I tried to understand why so.
what I found is this is called as bassel alignment (Q =0.577) here we get linearity in group delays. This has bigger box volume. Bigger box volume means lower F3. Lower f3 means lesser gain with LT. so the above is better over Q= 0.7. did I understand it right ? any point missing? The only problem I see is larger enclosure size.

About selecting F3 of 20Hz, I belive that If i can drive it safely to low as 20Hz I can easily make it for 30Hz or 40Hz, so currently I am calculating @ 20Hz. as we already said first lets experiment with different Q and F3.

My final design which I would assemble would be designed around 30Hz or 40Hz. I am not overhearing your advice.

Also the output of LT is Inverted. It needs a one inverted unity gain output stage. right?
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Old 8th January 2011, 06:20 AM   #44
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Quote:
Originally Posted by richie00boy View Post
Your box resonance is 60Hz-ish, there is no way you can EQ to 20Hz, you will have too much gain and the system will be full of hum and unstable, not to mention will only be able to attain quiet listening levels at best.

A true 40Hz response is surprisingly deep for music, I suggest you aim for that with your drive unit and box combination.
Yes thanks, I understand you are right... I have put my thought process in above post.
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Old 8th January 2011, 12:21 PM   #45
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Quote:
Originally Posted by Aucosticraft View Post

Also the output of LT is Inverted. It needs a one inverted unity gain output stage. right?
I just wired the woofer backwards...
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Old 8th January 2011, 04:27 PM   #46
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Some unusual experiment. I tried LT with QB3 Vented enclosure . the curve was achieved with trial and error. also applied Linkwitz Riley 4th order HPF. I found group delay could be the matter .The orange line is without equilazition and filter.

don't know if this is stupid for any reason.
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File Type: pdf Different try.pdf (134.5 KB, 20 views)
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Old 8th January 2011, 06:19 PM   #47
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Look at cone excursion.

Dropping the port tuning may help, but adding boost below the port tuning is asking for trouble, considering that many people actually cut the signal below Fb.

Chris
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Old 8th January 2011, 07:29 PM   #48
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excursion limits
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File Type: pdf the cone excurtion.pdf (48.1 KB, 16 views)
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Old 9th January 2011, 08:31 AM   #49
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Hi,
excursion @ 125W with both filters ticked.

Can you explain what we are looking at?
Power delivered at 14Hz, 20Hz, 32Hz, 100Hz, 200Hz?
What is the LT gain to give the bass extension from 40Hz down to 32Hz?
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Old 9th January 2011, 11:00 AM   #50
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Hi Andrew,

Yes, The above excursion is with both the filters ticked.
I just thought to experiment LT with vented system. The thought was if i can achieve it at lower gain of LT. the other thought was vented as a basic design has 3db gain. so broadly speaking vented gives double (+3db) output with the same rating woofer. 3db gain is like using other woofer delivering same wattage. but frankly this was a thought that stuck me, and trying to do it using tool don't cost much.

To make it easy I just manipulate the crossover points to get control over excursion and to get best possible F3.

I am posting the Graph for LT gain , HPF and Power Graph.
Attached Files
File Type: pdf _EQ transferfunction.pdf (110.1 KB, 11 views)
File Type: pdf HPF+ EQ.pdf (115.9 KB, 8 views)
File Type: pdf HPF.pdf (116.5 KB, 4 views)
File Type: pdf Power.pdf (109.8 KB, 7 views)
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