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Old 10-05-2010, 07:39 AM   #1
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sub/port placement??

I've been doing some reading to try to get a better grip on building a box before I give it a try
Been playing with the RE enclosure calculator, very nice, even tells you what size to cut the MDF

However.. The diagram doesn't show the cutouts for the subs .

There's many way to do it right? subs up/port back... subs/port back, both forward etcetc .

How does sub placement in relation to the port affect the box's sound??
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Old 10-05-2010, 11:29 AM   #2
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My personal experience may be useful to you as i had the same question years ago and decided to experiment myself (this was in no way a measured, scientific experiment but based on my subjective observations). my results are as follows: My preferred port location is on the the same face as the sub. However, the difference in output and SQ was minimal with different port locations in that particular car...00 dodge intrepid. I built a box (2.0 cubes net) with 3 different port locations (that could be plugged and used a 4" pvc tuned port at 36 hz), same sub (alpine type r 12), and power (hifonics bx 1205d at 2ohms..600watts rms). One was a rear port, the other a side port, and the final one was a front port (same face as sub). All were tried in different orientations (front firing, rear firing and even up firing (front face port only the others wouldn't fit that way). All sounded about the same, though there were some output differences with orientation (the loudest was definitely rear facing box with front face port about 1 ft from the rear of the trunk due to loading). The front face port generated more impact when front fired into the cabin with seats down. I believe this to be more due to the air movement you could feel on your skin from the port (very nice). With the seats up they all sounded similar with the advantage to the one loaded to the rear trunk with the front face port. As a result I prefer the front face port configuration firing into the cabin with the box sealed off from the rear around the sides for maximum impact, and output. With the sub box sealed from the rear it created similar output to the rear trunk loaded orientation( I used a baffle board with closed cell foam which the box face is sealed to). I've used the same configuration in my other cars with similar results. Anyway, hope that helps and keep in mind that different vehicles will affect the system differently.
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Old 10-05-2010, 02:31 PM   #3
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yeah veeman, that helps alot bro, thanks.

I had been thinking of loading off the back, subs up, but I think I'll need the room for the cubes.
I like your idea of firing forward and sealing off the back, should give me some extra room for box size, without needing the extra space for loading off the rear.

thanks again
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Old 10-05-2010, 05:28 PM   #4
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in vans like yours you would want:

-subs and port back
-subs up and port back
-subs up port to the side
-subs and port up

I personally did rather well with subs and port up in the far back of the van. Subs up and port back seems to be working well too. If you want to try something I've been thinking about but haven't tried yet, build a box similar to mine but fire subs into sides of van.
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Old 10-05-2010, 07:46 PM   #5
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A twin watermelon canon?

I couldn't build a box anywhere near that well, I need 90 degree cuts and glue instead of glass and knowhow..lol

The RE enclosure calculator I found only shows vented L port designs, nothing near as inventive as your and other guys SPL boxes!!

Is there another calculator for making other types of boxes as well? Tube ports etc?
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Old 10-05-2010, 10:16 PM   #6
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Car Alarm, Car Stereo, Mobile Video, and Cruise Control Info for Installers

they have a few box calculators
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Old 10-07-2010, 09:33 AM   #7
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Cool JD thanks..
Love that round port calculator, have the flared one too?

Soooo guys... if I wanted a box something like DS mentioned. Subs firing to the side, port back, but a rectangular box - 6 cubes at 30 hz - round port
- build a 6 cube box(account for sub displacment)
- add a 17.8 " long, 8 " in Internal diameter (Thats the size the calculator says anyhow) tube to the OUTSIDE of the box

Done?

Can't be that easy!!

Why is it that the round port calculator tells me I can use any diam. port but of a diff. length, to get the same tuning????

Now ,if I added the port to the INSIDE if the box, I would have to add the tube volume to the 6 cubes, is that right?

Crap, my learning curves is almost flat.
I'm starting to like prefabs...

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Old 10-07-2010, 09:53 AM   #8
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sounds about right (6 cubes @ 30 hz= 8"x 18" pipe).

Different diameter pipe can always be used to get the same tuning frequency....but, the port velocity of the air increases and port noise becomes a problem as well as output becomes limited due to too much load (the woofer can't move enough to push the air through the smaller hole...keep in mind that too much port is also a problem).

Yes, if the port is internal, that volume has to be accounted for.
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Old 10-07-2010, 09:53 AM
 
 
 
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