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Triticum's Improved Port Area Calculator


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45 minutes ago, juan777 said:

Your calculator agrees with many of my designs, i like it.

 

I noticed that your calculator does not take subwoofer size and quantity into account like other calculators I've seen. Could you explain why that value is not used?

me too, was wondering why cone area isnt factored in, or is it sort of redundant?

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Best Score to Date : 160.5 dB Outlaw (47Hz)[4 XM 15's & 2 Taramps Bass 12k's]

BL :  http://www.stevemeadedesigns.com/board/topic/147800-chevyboy95s-4-15s-7krms-wall-1533-db-on-half-power/
YouTube: http://www.youtube.com/hitemwiththeflex/

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i know through PM's he has gave me some great advice and told me what to expect and everything he told me has came true through my experiments. That is why i go to him first now. Trying to design a box for a pair of 10's on 5k is a son of a bitch.

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7 minutes ago, strangeduck said:

i know through PM's he has gave me some great advice and told me what to expect and everything he told me has came true through my experiments. That is why i go to him first now. Trying to design a box for a pair of 10's on 5k is a son of a bitch.

Any box Ive ever tried to plan for small subs was a bitch. Probably why I have stayed with 15's for so long. Battling port area and length always was an issue.

29408240963_9908a51930_o.png
Best Score to Date : 160.5 dB Outlaw (47Hz)[4 XM 15's & 2 Taramps Bass 12k's]

BL :  http://www.stevemeadedesigns.com/board/topic/147800-chevyboy95s-4-15s-7krms-wall-1533-db-on-half-power/
YouTube: http://www.youtube.com/hitemwiththeflex/

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So here's what i've found. Optimal seems to get port velocities in a range of 23 - 25 m/s. Minimum gets the velocities in a range of 32-33. By no means have I done extensive testing with different situations but I did 12 tests. I can do some more at another time to push the numbers more towards the extremes on both ends. The calculator so far seems to be pretty consistent which is definitely a good thing. 

Note: Test were done by using Triticum's calculator and comparing the port velocity graph of the Optimal, Minimum and a control port area. If I can find a way to keep people from changing the document I will post a link so y'all can see the actual numbers. 

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I did 11 more test with a different sub and the results change dramatically. The optimal port area now results in a a velocity in the low 30s while the minimum results in a velocity in the low to mid 40s. 

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2 hours ago, juan777 said:

Your calculator agrees with many of my designs, i like it.

 

I noticed that your calculator does not take subwoofer size and quantity into account like other calculators I've seen. Could you explain why that value is not used?

 

1 hour ago, ChevyBoy95 said:

me too, was wondering why cone area isnt factored in, or is it sort of redundant?


It seems really counter intuitive, but right at the point where port velocity is the highest (usually at the tuning frequency, but not always) cone size, sub quantity, or Xmax just don't matter much at all.  Right at the tuning frequency it really is the box that is playing and not the sub/s. The subs are just putting energy into the system, there is very little cone movement and virtually no output from the cone/s themselves.  Above or below that peak port velocity frequency cone area matters a lot but port velocity drops off pretty fast from that peak so port area is no longer limiting.

 

Here is an example of what port velocity looks like relative to frequency:

Capture.PNG.5e1a5fd2ccc75de777989c01c517ddb8.PNG

Just a couple Hz above or below that peak spot and things drop off fast.  Getting the right port area is all about optimizing for that peak.  

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