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Discussion Starter · #1 ·
I just finished my ultimax 18 build. And am quite happy with it. I tuned it to 18hz and 10cft internally. I was very meticulous with the port length and box volume calculations but I wanted to see where the box tune would unload.

I played sine waves 1/6 octave and the port seems to unload at 12.5hz. The driver moves a small amount and the air comes out the slot ports???? I'm very confused. It has heaps of output at 12.5hz. It's tremendous. And clean. Doesn't even seem to chuff much.

I guess I did something wrong. The only thing that varied from win isd is that I made the 3 slot ports 25mm longer than needed.

Is that enough to change the tune that much???
 

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I played sine waves 1/6 octave and the port seems to unload at 12.5hz. The driver moves a small amount and the air comes out the slot ports???? I'm very confused. It has heaps of output at 12.5hz. It's tremendous. And clean. Doesn't even seem to chuff much.

I guess I did something wrong. The only thing that varied from win isd is that I made the 3 slot ports 25mm longer than needed.
"heaps of clean output at 12.5Hz" and "did I do something wrong?" strike me as an oxymoron, along the lines of "jumbo shrimp", "freezer burn" and "government intelligence". It sounds to me like you did quite well, unless I'm missing something. :scratch:
 

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Discussion Starter · #3 ·
I guess it does sound silly. It just makes me wonder where it starts to roll off. I doubt it is linear. I think I will buy a umik and use rew and minidsp to check it out.

Music does blend nicely with my mains and it doesn't sound much different than my svs pb12plus.
 

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Discussion Starter · #5 ·
Yep will do next time on the PC.
I watched Hanna last night at -10 all channels set to small and it was a major spl upgrade over my svs. The lows are sooooo deep. I'm am very happy in that regard. The scene where she is jumping on the shipping containers was amazing as is the whole movie really. I have all my ht nearfield too. So I can feel a lot of rumble.
 

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Discussion Starter · #7 ·
1 other question.

With 3 slot port length win isd gave me approximately 987mm. Is that 987mm each port or 987mm total length of all 3 combined?
 
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