Enough? 2 X 2" aeroports with Eminence LAB 12 in 3.15 cubic foot box - AVS Forum
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post #1 of 5 Old 07-28-2012, 03:53 AM - Thread Starter
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I have been modeling for days. I purchased one of Erich's 3.5 subwoofer flatpacks. (Awesomely constructed by the way.) The problem I am running into is location and length/width of the aeroports I want to use from partsexpress.

From the front of the chamber to the interior bracing there is only about 10 1/2 inches of clearance. For a 24hz tune, I would need 15 inches in port length, which is too long. Winisd says that 2 two inch (0.047 meters in Winisd) Precision port flared ports will generate a vent mach of 15, which is acceptable to winisd, but higher than the more standard 10 that I read about. The precision port website calculates that I will need 8.5 inches of length for this tuning.

I know that these ports sizes are considered small, but they seem to model ok. Any thoughts or recommendations?





I have attached the information I calculated from modeling. I have noticed that winisdpro gives lower vent mach speed (6-7) for the 4 inch and 2x3inch flared ports. But I kept my original calculations for the moment. Subwoofer vent information and tuning.docx 14k .docx file

I have also attached a snapshot of my winisd pro modeling. For some reason Winisd pro is telling me one 3inch port is about equal to two 2inch ports winisd pro modeling.docx 95k .docx file
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File Type: docx Subwoofer vent information and tuning.docx (14.0 KB, 3 views)
File Type: docx winisd pro modeling.docx (95.3 KB, 1 views)
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post #2 of 5 Old 07-28-2012, 11:04 AM
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For that sub, I would use nothing less than one four inch port, or two 3 inch ports. There is no way that you will be happy with the two inch ports.

JP
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post #3 of 5 Old 07-28-2012, 11:51 AM
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Quote:
Originally Posted by zora View Post

For that sub, I would use nothing less than one four inch port,
I'd use two.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
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post #4 of 5 Old 07-28-2012, 03:31 PM - Thread Starter
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Quote:
Originally Posted by zora View Post

For that sub, I would use nothing less than one four inch port, or two 3 inch ports. There is no way that you will be happy with the two inch ports.
JP

(Bill I have bought your plans the THTs. Love em', just couldn't the get the wife to love them as much yet so the Lab-12 is going to this smaller project. I'd love to fit two ports, but the lengths are pretty long at about two feet each.)

I found a way to fit a 4 inch port around through the bracing. I can fit a one 4 inch port 13 inches (about 27 hz) or 15-16 inches (about 25 hz). 25 vs 27 hz.docx 94k .docx file


I think I favor the 27hz tuning due to increasing the sensitivity and output about 27hz or so compared to the lower 25hz tuning. There is, however, a steeper roll-off so less deep bass output. I have read the precision ports tend to increase output by about 3 decibles at the tuning frequency compared normal ports, but that could be marketing.

The 27hz tuned port will fire out the left side of the cabinet. I actually like that because my daughter is less likely to try to stick things inside and it fires about 18 inches away from the corner in a very large open layout house. The 25hz tuning would fire out the front baffle directly below the driver.

This have been a great experience and motivates me to build my own cabinets now that I see tradeoffs are always involved any other way.


Am I on the right track here? Thanks for anyone's responses!
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post #5 of 5 Old 07-28-2012, 08:40 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

I'd use two.

While I agree with Bill, the idea only works if you were designing the box from scratch. Fit the largest port you can in the box, and enjoy!
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