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Hugh G. Rection

understanding ports, a lesson in dimensions vs efficiency.

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seems like it would take some very odd measuring equipment, and alot of time, to test and verify this. with the air in the port moving both directions, measuring velocity and pressure would take much different tools than if it were just moving one direction.

Yeah its definitely not something that can be easily measured by most folks. I know a hot-wire anemometer is the right tool to measure port velocities, since those things don't care what direction the air is flowing, but again, not something most folks have laying around (myself included).

I posted the formula since it mathematically supports what you said in your original post and to try and give folks a objective method by which they can compare different shaped ports of equal area. I've got the formula plugged into Excel which makes comparing ports pretty quick and easy. I can post what the formula looks like in Excel if anyone is interested.

Just a thought, what about repurposing a used MAF/Mass Airflow Sensor from a car? Figure you can get one out of a junkyard fairly affordably, but it'd take some calibration to use it and make sense of the data based on the size of the port/sampling tube in the MAF.

Just thinking outside of the box.

its an interesting concept, but i just dont believe that mass airflow sensors work in a way that would be useful for something like this.

Theoretically, possible though. A VAF/Vane Airflow Meter measures mass by deflection of a door hung in the airflow. MAF reads mass of air based on how fast a wire heated to a set/known temp is cooled by the air moving through the sample tube. I see no reason why if you could keep the air temp stable (otherwise you'd have to mathematically correct for it) you could use the same cooling of the MAF element to infer air velocity. Maybe posssible, maybe not, but the guts of a MAF seam like a step in the right direction towards what you're trying to measure at a reasonable price on the used/salvage market. Calibrating it would take some test and tune.

Well this settles it, next box I build will have an areo port

Yeah, I'm about a millimeter away from chunking my box design in the trash and changing dimensions to fit an aeroport.


2007 Mazda 3; 5000K HID's, Kenwood Excelon KDC-X997, Infinity Reference 6.5 comps in front and coaxials in the rear doors, JL 320.4 four channel, Rab Designs built ported enclosure with an SA12, Kenwood monoblock, Redline Leater shift boot/e-brake boot/center console cover, JBR short shifter/shifter bushings/rear motor mount. Nothing special, just a daily driver/wife and kid hauler.

Build Thread

1996 Mazda Miata: Kenwood Excelon HU, Alpine speaker in the doors, Clearwater (miata specific) headrest speakers, sounded awesome but no room for bass.

1994 Mazda Protege: Kenwood Excelon HU, Infinity Reference 2 ways all around, 2x RF Punch 10's in ported boxes. Pounded like crazy for a first attempt.

MECP certified....not really. I CAN however MacGyver stuff out of duct tape and zip ties, yell vitriolically, and throw tools while drinking beer.

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Glad that I caught this, will be building my box in the next month or so.


When I hear music, I fear no danger. I am invulnerable. I see no foe. I am related to the earliest times, and to the latest.
~Henry David Thoreau

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The world is not flat after all. A circle it is. I'll be rebuilding with an aero port soon Two different designs but I always thought that my enclosure that is aero ported sounded better than the wood ported.

I'm tuned in to learn more!

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Tuning in... Built an enclosure with a long ass slot port so I could tune to 32hz at 1.5c net. I don't like the sound of it and my enclosure if huge. I'm still trying to figure out what size aero I need to prevent noise and also to keep my enclosure as small as possible. Good write up. Learning a lot on this thread... I hope more is posted on this topic.,..


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seems like it would take some very odd measuring equipment, and alot of time, to test and verify this. with the air in the port moving both directions, measuring velocity and pressure would take much different tools than if it were just moving one direction.

Yeah its definitely not something that can be easily measured by most folks. I know a hot-wire anemometer is the right tool to measure port velocities, since those things don't care what direction the air is flowing, but again, not something most folks have laying around (myself included).

I posted the formula since it mathematically supports what you said in your original post and to try and give folks a objective method by which they can compare different shaped ports of equal area. I've got the formula plugged into Excel which makes comparing ports pretty quick and easy. I can post what the formula looks like in Excel if anyone is interested.

I have a hot wire anemometer if you wanna borrow it :)

This one. http://www.fieldpiece.com/products/detail/aat3-hot-wire-anemometer-psychrometer-accessory-head/anemometers/

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So if a suggested port area (manufacturer suggested) is 50" for a slot port what could be said as a reasonable reduced amount of area for a round port.

reason on why I'm asking is because aero ports are easily bought with flares or made compares to making a slot port with an equally effective flare is its counterpart aero port. With the round ports more easily flared to reduce chance of audible noise people like to use them to as a way to get away with fitting bigger boxes in smaller areas with less port area but no harm done to efficiency or audible quality.


t1500bdcp

2 t2d4 15"

1 t600.4

1 t400.2

1 set p1 tweets

singer alt, tons of wiring, smd vm-1, 80prs, back seat delete, still in the works, aiming for a 145-147 with the ability to play 25hz up to 50hz.

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Depends on the ratio of the slot port.


b_350_20_692108_381007_FFFFFF_000000.png

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Krakin, are you some sort of mad scientist?

I would have replied earlier, but I was measuring the output of my amp with a yardstick . . .

What you hear is not the air pressure variation in itself

but what has drawn your attention

in the two streams of superimposed air pressure variations at your eardrums

An acoustic event has dimensions of Time, Tone, Loudness and Space

Everyone learns to render the 3-dimensional localization of sound based on the individual shape of their ears,

thus no formula can achieve a definite effect for every listener.

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So if a suggested port area (manufacturer suggested) is 50" for a slot port what could be said as a reasonable reduced amount of area for a round port.

reason on why I'm asking is because aero ports are easily bought with flares or made compares to making a slot port with an equally effective flare is its counterpart aero port. With the round ports more easily flared to reduce chance of audible noise people like to use them to as a way to get away with fitting bigger boxes in smaller areas with less port area but no harm done to efficiency or audible quality.

One of the hassles of aero ports is they only come in certain sizes, so you just try to get as close as you can.

A 50 sq in slot port is probably going to be somewhere around 3-3/8" x 15", that should be equivalent to a 42 sq in aero port, which is 7.3" in diameter. Since you can't get a 7.3" diameter aero port you are probably going to round up to 8", which is right back at 50 sq in of port area.

I suppose you could use a 6" and a 4" port together for 41 sq in, but you don't see folks using different sized ports together. I've haven't had a chance to try different sized ports together myself, from my own research I've heard it works just fine, but since I haven't tried it I can't say for sure.

Edited by Triticum Agricolam

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

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How would you even determine port length with 2 different sized ports?


t1500bdcp

2 t2d4 15"

1 t600.4

1 t400.2

1 set p1 tweets

singer alt, tons of wiring, smd vm-1, 80prs, back seat delete, still in the works, aiming for a 145-147 with the ability to play 25hz up to 50hz.

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excellent read guys!!

Thank you much for taking the time to write all of the information in this post!!

seen as i do have some port alterations to my existing box, i am really starting to wonder if i wouldnt just be better off to start all over from scratch.

Edited by Ritch40

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