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Old 7th July 2013, 09:57 PM   #101
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The tuning isn't really doing anything currently - you wont hear the hump in their current state as the roll off is around 20db at 40hz.

Room acoustic is solveable - a local home cinema room company for a price will come and do a survey and tell me how much to fix it with lots of foam etc.

I am glad i am being the example of how not to build a MLTL.

Whats happened to yours Buzz - was wanting to see if yours worked first time!
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Old 7th July 2013, 10:53 PM   #102
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Doubtful, as I know less than you and depending heavily on modeled response. My current choice is here. screwed up start point of port, but doesnt change much. I like the idea of downward firing port, but it has been suggested that this not feasible without significant lift off the ground to reduce floor interaction.

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Old 8th July 2013, 03:41 AM   #103
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Well, everything I’ve seen still comes up a leak and to answer my earlier seeming conundrum, I’d forgotten that this is a folded pipe, so a leak between the two pipe lengths around the divider board satisfies it.

Also, if the divider board isn’t long enough, i.e. doesn’t preserve the area expansion around the bend, it can at least partially be the cause when the driver is at the top of the bend.

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Old 8th July 2013, 03:46 AM   #104
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Quote:
Originally Posted by buzzforb View Post
I like the idea of downward firing port, but it has been suggested that this not feasible without significant lift off the ground to reduce floor interaction.
Define 'significant'. IME, the larger the cab's base area, the less gap required due to a greater slot radiating area.

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Old 8th July 2013, 08:08 AM   #105
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GM,
Thanks for the answer. The port would be 6" in diameter and base would be appx 24"x25". Sim looks good to my eyes, being bested only by much larger cabinets or ones with driver positioned 1/2 down length. Talking about ideal, positioning the driver 1/2 way down the TL is quite shocking in what it does, but practical layout is difficult in my mind.
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Old 8th July 2013, 01:25 PM   #106
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You're welcome!

FWIW, I get a 2.55” slot assuming there’s at least 6.68” clearance to any walls, otherwise it would become an empirically arrived at gap for me, but historically I use slot loading to further mass load the vent or make up for a too short cab acoustical pipe length, so no experience trying to find a 2pi loading solution to a 1.0 or 0.5pi boundary condition or even know if there’s one in theory.

Hmm, to my way of calculating it, ~half way is only 'ideal' in a golden or acoustic ratio cab or typical expanding TL [ML-horn, AKA MJK's ML-TQWT project].

Usually not difficult if folded, but folk's generally not tolerating a wide baffle severely limits design options too much to make it practical.

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Old 8th July 2013, 01:45 PM   #107
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ill post the worksheets later if you dont mind taking a look.
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Old 8th July 2013, 02:45 PM   #108
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When you say 2.55" slot, is this assuming no internal port length and using floor to create this slot.

Here is 30% driver placement
Attached Images
File Type: jpg Altec 30%1.jpg (332.3 KB, 94 views)
File Type: jpg Altec 30%5.jpg (447.3 KB, 90 views)
File Type: jpg Altec 30%6.jpg (462.1 KB, 87 views)
File Type: jpg Altec 30%7.jpg (231.7 KB, 84 views)
File Type: jpg Altec 30%9.jpg (305.2 KB, 81 views)
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Old 8th July 2013, 02:48 PM   #109
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Here is 50% of line length. Sorry Vinylvalves, if GM helps me sort this, ill happily let you get a laugh or two at my expense.
Attached Images
File Type: jpg Altec 50%1.jpg (332.3 KB, 8 views)
File Type: jpg Altec 50%5.jpg (446.9 KB, 7 views)
File Type: jpg Altec 50%6.jpg (458.4 KB, 5 views)
File Type: jpg Altec 50%7.jpg (231.6 KB, 5 views)
File Type: jpg Altec 50%8.jpg (235.5 KB, 3 views)
File Type: jpg Altec 50%9.jpg (304.8 KB, 3 views)
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Old 8th July 2013, 09:46 PM   #110
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A sectio through the test cabinet showing how the speaker is located with respect to the fold.
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