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Discussion Starter #1
As you may have read I am trying to decide on a sub build, I made up these designs in WinISD but I am not sure id they are good designs. It seems like the 10cf box tuned to 17.5hz looks good (the port is 12X4X35.66 with a freq of 189hz)but I don't understand what the other graphs tell me so can someone interperut these please. This is for Malestrom-X with an EP2500 bridged mono 4 ohm 2400w, I have tha amp but waiting for woofer which is OOS.
Just for ease (building and moving) I would like a smaller box size than an LLT if I can.
 

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Here's a comparison of the 17 cu.ft. tuned to 14 hz and 10 cu.ft. tuned to 17 hz. Both are modeled with 1500 watts applied. Porting for the 10 cu.ft. box would be a 8 inch port 41 inches long or a square port with a surface area of 50 square inches. The performance of the 10 cu.ft. box is excellent, you just give up some low end extention over a bigger box. If that is what suits your needs then go for it.

dcx.JPG
 

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Discussion Starter #3
I guess the question would be how much information is in movies in that range of hz. If I read correctly I am giving up 1 db between 18hz and 10hz (approx from reading) which accoeding to my research we shouldn't be able to detect. Seem like a small price to pay for a huge reduction in box size. My next question is in the cone excursion and delay the 10cf box does a little better, is this correct? The max amp power @ 4 ohms is 2400w which (again if I am starting to understand these graphs) the 10cf box doesnt ecceed the X-max but the larger box does, is this correct and if it is does it mean anything.

i think in my size restrictions the 10cf box is a easier build (size and moving) with less cut waste.

Thanks again Mike for taking the time to help me understand.
 

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Between 18hz and 10hz you're giving up an average of 3 db as shown in the graph above.

The max amp power @ 4 ohms is 2400w which (again if I am starting to understand these graphs) the 10cf box doesnt ecceed the X-max
The listed maximum power handling of the sub is 1500 watts not 2400 watts. The SPL graph in post #2 is based on that. Here is the cone excursion graph with 1500 watts input power. The 17 cu.ft. box barely exceeds Xmax which is no concern.

maelstrom c ex.JPG
 

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XC, do not think of the power handling in a larger vs smaller enclosure as though the larger box can't handle more power. What is really happening is that the larger enclosure will allow the driver to reach a given excursion level (which equates to an output level) with less power in lower frequencies as compared to the smaller enclosure. Above some frequency, say 25hz, the power handling and output capability of the two subs will be virtually identical despite what the simulations may or may not show.

What you gain with a larger enclosure is a handful of benefits. First, a lower tuning can be achieved while maintaining a relatively flat frequency response. That is good not only for producing more tactile bass in movies and having better impulse response, it also leads into the second benefit of not having to purchase a device with a highpass filter, as the driver won't theoretically begin to unload until nearly single digits, at which point it is fairly well protected. A tune closer to 20hz leaves the sub somewhat vulnerable in the low to mid teen region, an area that a lot of movies are placing potenet bass and electronics rolloff hasn't really kicked in much yet. Also, in trying to get that lower tune, a larger enclosure allows for more cross sectional port area, reducing the chances for port compression or chuffing.

Now with all that said, don't get me wrong by any means, the 10 cube 17hz design will still be excellent - it should do everything you want it to do without breaking a sweat. It will also be easier to move and probably easier on the eyes. You may need to look into some type of a highpass filter however, and with that the really low infrasonics may be just out of your reach. 13hz compared to 17hz sounds tiny, only 4hz, but octave wise, it's nearly a half octave lower.

I just wanted to give you a heads up on what the advantages were because it seemed like you were only considering the disadvantages :T
 

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Discussion Starter #6
Thank you very much,
I tried to read all of the LLT info but I just couldn't follow all the technical info so my brain just skips over that stuff and I get lost.
Your explanation above helped me understand much better.

The only reason size is an issue is building that monster since the length will extend beyond one sheet and was unsure of the right way to extend the length. My guess is to the sheets together and screw/glue a 2 or 3 foot piece inside and brace across that area top and bottom. The unit may have to be finished in place due to weight and size. It will be built into the wall and either flush and finished or slightly recessed with a grill cloth.
Do I need to do double sheet the entire front panel or just like 4 or 6 ft. around the woofer area. I will be screwing it into the studs in the wall to keep it in place unless someone tells me that is a bad idea.
 

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Discussion Starter #8
I can anchor it around a chimney with steel cable if that would be better and leave an inch space on the sides so it doesn't touch the studs just the subfloor.
 
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