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Discussion Starter #21
@BD55 I was planning to encase the duct work where it passes through the enclosure. We want to avoid such a large whole as in your drawing so it looks unmodified. I planned to double the soze of the wholes in the wall and then install matching registers with both ducts routed to one and the manifold in the other. This is what I drew in option 1 and 2. The rectangle is the duct and the round tube is the possible port.

@Mike I really need to get up there and measure. At what point do you not include a high pass filter? I will throw what ever at this sub I can get a hold of so I want to be safe. The way I see it at 12 or 15HZ tuning I get 3 or 6db at 16-17HZ and above so keeping the tuning higher gets me more output once EQ'ed. Am I correct in stating that?

Zach
 

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At what point do you not include a high pass filter?


A rule of thumb is 15 hz but it also depends on how the sub models and how much power they get.

The way I see it at 12 or 15HZ tuning I get 3 or 6db at 16-17HZ and above so keeping the tuning higher gets me more output once EQ'ed. Am I correct in stating that?


Theoretically yes. We need to know the opeing size of the register in the picture and then double it to see exactly how big the opening will be. You can not use an opening that is too small for 4 18 inch subs or you end up with a horn loading.
 

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Discussion Starter #23 (Edited)
I did some measuring and came up with about 200 ft^3 if my math is correct. The height is 33", width is 144" and the depth is 75". These measurements are as if I capped off all the studs. It amazes me how large a space looks to me until I fill it with objects. As you can see below it will be very hard to fit more than two 18" speakers in the space. Both the small opening on the bottom that is the conduit for the ducts and the whole manifold can be reduced in size since the sd of the speakers as a whole is much smaller if only using two. That is a good thing as 800 in^2 is about the max opening I would want to put in the wall. Reduce that by half as the A/C takes one half of the opening and then further reduce it due to the design of the register and I believe 2-3 18" Mach 5's are all I could take if ported. I could build into the attic but at this point I believe the opening size is my limitation. Correct?

 
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