General questions and answers. Elaboration on all things audio and the facts.

[Papermaker85 5,000+ posts]

We need a good thread where people can ask questions a they can be answered and answered with science behind them..

I see so may outright wrong information.

For starters port area per cube. It's stright up wrong and there is no truth to it.

Click to read more...

 

[macsdad 10+ year member]

We need a good thread where people can ask questions a they can be answered and answered with science behind them..I see so may outright wrong information.

For starters port area per cube. It's stright up wrong and there is no truth to it.

Please explain.

 

[shizzzon 10+ year member]

Papermaker or someone else.. Do you know what % of xmax is used when determining recommended port area for a given speaker?

 

[Papermaker85 5,000+ posts]

it is based on displacement and tuning frequency. Its been YEARS since I've seen the formula i'm going to find the actual formula but for sake of answering your question and making it easy for everybody to figure out the proper amount to avoid noise and compression.

Car Audio - PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES

pretty simple to do.

 

[Papermaker85 5,000+ posts]

Dmin = 100*(20.3*(Vd^2/Fb)^0.25)/Np^.5

vd is total displacement of the driver(in cubic inches)

Fb is the tuning frequency(in HZ)

NP is the number of ports

its strictly displacement and tuning frequency related. there are other variables like turbulence but for the most part its accurate..

 

[Papermaker85 5,000+ posts]

I'm going to work on developing how the port's damping affects both output and bandwidth. i see NOTHING on it. also its relation to phase and its acoustical impedance which i cant find as well.

 

[Slo_Ride 5,000+ posts]

We need a good thread where people can ask questions a they can be answered and answered with science behind them..I see so may outright wrong information.

For starters port area per cube. It's stright up wrong and there is no truth to it.

Thats what the forum is for. We don't need one thread for everyone to ask a question. That's retarded. If a member has a question then he or she can start their own thread asking their particular question.

Port area per cube is not a written in stone rule. Its a general reference.

 

[Papermaker85 5,000+ posts]

Thats what the forum is for. We don't need one thread for everyone to ask a question. That's retarded. If a member has a question then he or she can start their own thread asking their particular question.
Port area per cube is not a written in stone rule. Its a general reference.

It's retarded and Invalid.

Don't ruin a potentually good thread..

It's meant to get everybody involved over a wide variety of subjects and get the youth and or less knowledgeable crowd a chance to learn and be all in one place..

 

[Papermaker85 5,000+ posts]

Papermaker or someone else.. Do you know what % of xmax is used when determining recommended port area for a given speaker?

Vd is xmax*cone area. The actual xmax is going to depend on the box tuning and input power. I'll get more into this as well.

 

[the727kid 10+ year member]

Why even bother try to educate the members on this forum? If its not a wall and supertweets, you're doing it wrong.

 

[n2audio 5,000+ posts]

Dmin = 100*(20.3*(Vd^2/Fb)^0.25)/Np^.5vd is total displacement of the driver(in square inches)

Fb is the tuning frequency(in HZ)

NP is the number of ports

Sorry to nit-pick, but if it's Sd * xmax then the unit would be cu. in.

Personally, I don't fault someone for wanting to get something done right w/o needing to know the science behind it. Some people have real life to tend to and have no desire to spend a week studying enclosure design theory.

If the goal is to build an effective, noise-free port then 12-18 in*in/cu ft will get it done -- maybe way bigger than necessary but nonetheless effective.

IMO the over-arching point of the guideline is just to say you can't put a 12 in 2cf and tune it with a 2" port -- something a lot of novices aren't aware of.

 

[Papermaker85 5,000+ posts]

Thanks. Your right it's cubed. Lol.

As far as the port area it's simply missleading. Even in 3 cubes ported a 15 that has 30mm xmax still needs around 100in^2 and in 5 cubes with 12mm xmax only needs 40in^2..

 

[Papermaker85 5,000+ posts]

Why even bother try to educate the members on this forum? If its not a wall and supertweets, you're doing it wrong.

Eyes cross.

 

[Papermaker85 5,000+ posts]

Sorry to nit-pick, but if it's Sd * xmax then the unit would be cu. in.
Personally, I don't fault someone for wanting to get something done right w/o needing to know the science behind it. Some people have real life to tend to and have no desire to spend a week studying enclosure design theory.

If the goal is to build an effective, noise-free port then 12-18 in*in/cu ft will get it done -- maybe way bigger than necessary but nonetheless effective.

IMO the over-arching point of the guideline is just to say you can't put a 12 in 2cf and tune it with a 2" port -- something a lot of novices aren't aware of.

The point is the info is out there. If anyone with a brain wants to learn we need to keep it relevant in everyone minds and the right way not some made up bs..

 

[kr15 5,000+ posts]

This is interesting however. Some vague generalizations that arent always an end all be all. Like power input for example. Im running a sub with 30mm in a 4.2cu box...but im running double the rated power and can max it out mechanically easily...how much port area should i be running? Also, im tuned low, 29hz...and from my experience you can do less port area tuned low....so for those more knowledgeable than me, how much port should i run? Curious to see how close, or far off I am