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Discussion Starter #1
I need help. WinISD is spinning my head:dizzy:

I am wanting to build a 15" sonosub tuned to around 15hz (or whatever is ideal). I have been playing around with WinISD, and I have a few questions.

Here is what I have decided on so far:

24" by 48" sonotube
CSS SDX15 driver
Behringer EP1500 amp

I have seen a few builds using a 6" port about 27 to 31 inches long, but I have not been able to find any 6 inch sonotube within a hour of my house. Is there any way to use multiple 4 inch ports or an 8 inch port? What length would give me the best performance if I went with either of these? Even when I put the 6 inch port into WinISD, I would get extreme port velocity??

I am also confused with cone excursion. With the 1400 watts from the EP1500, I am exceeding the limits of the driver in WinISD modeling. Is there any way to not push all of the watts from the EP1500? I have a BFD for filters if needed. If I had to to create a SSF, how would I go about doing that?

I just want to make sure that I am covering all of my bases before I start purchasing everything. I barely got my wife on board, so I want to do it right.
 

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I am coming up with about 11ft^3 ... assuming you can fit a 36" length tube in the 48" tube and clear the driver displacement, you can tune to 17Hz with an 8" x 36" port. You will need a 13Hz HPF (CSS Reckhorn B-1) in order to keep cone excursion tamed. Port velocity will be fine with a peak of 23 m/s near your tuning frequency. Keep the unit crossed over at 80Hz and the first port resonance at 188Hz is not an issue.

Also... I do not remember if that amp has been tested, but I wonder if it actually puts out 1400 watts at 20Hz?
 

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John, Do not be afraid to us 1400 W... Use RMS values instead of peaks, which will be more representative of program material.
 

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Discussion Starter #4
Thanks for the help guys.

Would I be able to create a HPF using the BFD that I have, or do I really need to purchase the one from CSS?

Just for background, I do not run my system at insane levels. This sub is going to be total overkill, but I want to make sure that it will fill a large room when we finally buy a house.
 

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You will most prbably not need a high pass even if you drive your sub at insane levels. Your tune is already quite low and most materials will be kept above that.
Anyway use common sense, if you always feel the driver is overstressed due to very low frequency (and I strongly doubt that will happen unless you intensionally use sin waves well below tune), reduce SPL or get yourself a high pass.
But my opinion is you will never need one.
 

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Yes, but isn't is better to be safe than sorry? I'm new at this but it seems everything I read about yes/no on a HPF in a ported design is YES.

I know that in my case there will be times were I'm going to have a strong desire to push my build to the max (either by myself or if a bass hungry friend comes over). I would sure hate to hear the dreaded clack. Yes, I've be known to have issues with self-control!
 
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