Port Wars frequency testing

[shizzzon 461]

how exactly do u go about finding peak note to use in port wars?

i know what to modify AFTER the port is made but how do u know which note to use?

i was thinkin about throwin the meter in the box and sealing it up..

but... if i do this, will the car's peak note effect the peak note for port wars?

or IS the proper tuning for port wars equal to SPL tuning?

[sadistic 13]

at this link is a good example of tuning box tunes 33hz and 40 hz is it's peak you put 40 hz note threw it it will be louder then 33 but the 33 hertz note will feel harder then the 40 hertz it just the way this sub is. there are better out there like ssa's. but as you know the higher the hz the softer it hits. put it this way this sub could be better the 33 hz and lower just does not travel as far as the 40 hz note. this is why placement is key. now on to the other part. this is why i suggest those bass meknic cd's sonic over load .second cd track 4-11 the first 5 are low spl tracks. that rage in frequency like so track 4 = 20-30hz track 5= 30-40hz etc etc.... your just using five tracks to find your peak and your using a mic at the window or at the port etc...how ever they measure it for that particular comp.so read the rules. this is because every sub peaks differently like at link for the ported box.

http://manuals.harman.com/JBL/CAR/Boxes%20and%20Parameters/P1022rev3_27_06.pdf

[shizzzon 461]

so.. r u trying to say that port wars peak frequency can change by the type of sub i'm using?

Meaning, peak frequency wont change in car by me swapping out subs but if i were to be swapping out subs for port wars, subs effect port war peaks?

[sadistic 13]

so.. r u trying to say that port wars peak frequency can change by the type of sub i'm using?

Meaning, peak frequency wont change in car by me swapping out subs but if i were to be swapping out subs for port wars, subs effect port war peaks?

no the port tuning for that sub determines peak frequency. but the tune can be higher then what it's tuned at.

[sadistic 13]

so.. r u trying to say that port wars peak frequency can change by the type of sub i'm using?

Meaning, peak frequency wont change in car by me swapping out subs but if i were to be swapping out subs for port wars, subs effect port war peaks?

let me answer each question yes frequency's can change by type of sub or brand

2)does not effect port wars peaks port tune effect port wars peaks

[shizzzon 461]

hehe, i dont think you understand the post, let me start over.

I currently have a wall with no port in it right now, after doing testing the other day, i need to build a port that peaks at 50hz as that's my car's peak.

Port wars is completely different from just burping 20" from the windshield... Port wars is measuring the back pressure from inside the box and the start of the port. (slot porters will have an advantage here)

Now, i know how to find peak frequencies in cars, but have never tried to find peak frequency for port wars because i do not know if the front wave of the subs has an effect on the back wave which is inside the box.

I would assume it would but also, i'm sure the Wall itself has it's own peak and differs from the car's and i'm pretty sure i'm right about that.

It's my understanding that if that's right that tuning to peak at the box's peak would not be the loudest in the car due to the car's acoustical design.

This is why i am wondering if sealing up the box with the meter inside will tell me the peak of the box. I'm about to go try this method shortly.

I'm assuming that the box's peak note will effect the port's entrance reading a LOT more than the car's peak note.

I am currently gearing up to compete in multiple divisions, one being port wars so it's essential to know how this works before i start guessing.

[sadistic 13]

hehe, i dont think you understand the post, let me start over.

I currently have a wall with no port in it right now, after doing testing the other day, i need to build a port that peaks at 50hz as that's my car's peak.

Port wars is completely different from just burping 20" from the windshield... Port wars is measuring the back pressure from inside the box and the start of the port. (slot porters will have an advantage here)

Now, i know how to find peak frequencies in cars, but have never tried to find peak frequency for port wars because i do not know if the front wave of the subs has an effect on the back wave which is inside the box.

I would assume it would but also, i'm sure the Wall itself has it's own peak and differs from the car's and i'm pretty sure i'm right about that.

It's my understanding that if that's right that tuning to peak at the box's peak would not be the loudest in the car due to the car's acoustical design.

This is why i am wondering if sealing up the box with the meter inside will tell me the peak of the box. I'm about to go try this method shortly.

I'm assuming that the box's peak note will effect the port's entrance reading a LOT more than the car's peak note.

I am currently gearing up to compete in multiple divisions, one being port wars so it's essential to know how this works before i start guessing.

i under stand the comp part would it be a higher tune or a lower to to hit the 50 hz i think you would have to tune higher to hit 50 on those jbl's because i got them in a 28 hz box and the peak is lower

not sure on the back wave either i would have to test it it most likely the same as 1/4 waves wear the back wave has a effect on the front wave because of distance to windshield and box placement. split into 4 quarters

could try it sealing up the box your right the box does peak differently

[sadistic 13]

all ported box have 4 waves a,b,c,d.--- line a from of cone to wind shield is front wave line b and c are the back wave to port out of the port to wind shield is line path d

just like speed of sound it travel so far at each hertz so 30 hertz travel less further then 50 hertz.. the b and c line depend on air space so you would have to box in the rear of the sub to adjust the back wave to pressurize the port. enough to hit windshield hard enough. so using a infinite baffle with to much air space will effect port tuning. any ways hope you get the point i think wall are ib right ???

[shizzzon 461]

they dont meter port wars at the windshield, they meter it literally IN the PORT. At the entrance point in the box is where the meter is placed.

i just came back from doin the box testing.

the box does peak differently than the car AND the car's peak note does play a partial role in finding the box's peak as well.

So, it's not as easy as just tune to 100hz and hope for the best, hehe, because that won't help.

My car's peak is exactly 50hz and the metering slope inside the box gradually got louder to 50hz then started to get quieter but only until it got to 53hz, just 3 above 50. Once it hit 53hz, the pressure started going back up again, up so much that 53hz is actually louder than 50hz! It kept going up until it peaked at frequencies 55, 56 and 57hz exactly at the same level then it started to slope back down all the way to 100hz with minor small peaks on the way.

So.. apparently, i must build a port to peak at 50hz for SPL, a port in the 30s for daily driving, a port in the 50hz range for bassrace(optional at the moment) and a port to peak in the range of 55-57hz for port wars.

Lots of testing to do...

[KU40 173]

I don't think Sadistic Customs knows what he's talking about, let alone being able to put it into logical sentences and paragraphs.

I don't know much about port wars however. But I wouldn't think that the vehicle acoustics have anything to do with sticking the mic inside the port, because the wave in the port has not had any interaction with the surrounding environment. You just want the highest pressure possible inside the box. I think you'll just have to do a lot of testing and tweaking the box, just like legal SPL comps.

[tech2332 3]

let alone being able to put it into logical sentences and paragraphs.

I'm glad I'm not the only one who doesn't understand a sentence he wrote on this topic.

Edited July 25, 2009 by tech2332

[sadistic 13]

they dont meter port wars at the windshield, they meter it literally IN the PORT. At the entrance point in the box is where the meter is placed.

i just came back from doin the box testing.

the box does peak differently than the car AND the car's peak note does play a partial role in finding the box's peak as well.

So, it's not as easy as just tune to 100hz and hope for the best, hehe, because that won't help.

My car's peak is exactly 50hz and the metering slope inside the box gradually got louder to 50hz then started to get quieter but only until it got to 53hz, just 3 above 50. Once it hit 53hz, the pressure started going back up again, up so much that 53hz is actually louder than 50hz! It kept going up until it peaked at frequencies 55, 56 and 57hz exactly at the same level then it started to slope back down all the way to 100hz with minor small peaks on the way.

So.. apparently, i must build a port to peak at 50hz for SPL, a port in the 30s for daily driving, a port in the 50hz range for bassrace(optional at the moment) and a port to peak in the range of 55-57hz for port wars.

Lots of testing to do...

exactly. you should use a interchange able port. they sell couplers at lows for 3,4,6 inch inside dia pipe then all you got to do is cut length of pipe and don't glue the pvc together and find the correct length and try to find that correct tune is all i can say

[shizzzon 461]

I don't know much about port wars however. But I wouldn't think that the vehicle acoustics have anything to do with sticking the mic inside the port, because the wave in the port has not had any interaction with the surrounding environment. You just want the highest pressure possible inside the box. I think you'll just have to do a lot of testing and tweaking the box, just like legal SPL comps.

You are right to a certain point.

When i was doing testing earlier, it would be better if i made a graph to show you so bare with me, the car's peak note DOES effect the reading inside the box because it gradually got louder in the box until it reached my car's peak note then started to roll off them BAM, it started going back up FAST til it finally peaked.

And this test was done with the port sealed up!

I believe what is going on is the car's acoustics is effecting the way the subs produce pressure in the car and what effects the front wave must effect the back wave since the subs are the only thing that remain the same in the cabin and in the box.

So with that theory laid out, i believe that if the box's peak note AND the car's peak note were to be the same... then that person would be in for a helluva surprise when it gets metered.

I'm still trying to understand something though-

No matter what port you use in port wars... whatever it peaks at in the car, it ALWAYS peaks 1-3hz lower in the port... Why is this?

I don't know where to look to understand this reason.

Is it because when we say stuff like, " i'm tuned to 35hz but it peaks at 38hz..." means that what the port is TUNED too is what it'll peak at in the port?

[KU40 173]

Well at the tuning frequency is when the most sound is coming out of the port instead of the front of the sub. The sub is moving the least at that point, but the air from the port is moving the most (relative to the rest of the frequency spectrum that the sub will be playing). So the air inside the box is doing more work at that point, and perhaps that means more pressure inside.

With this laid out I wonder if smaller boxes would be better for port wars. Less volume to pressurize inside the box. I'd think there would also be an ideal port size. Too large of a port would allow the box to depressurize too easily, but too small of a port may not let all of the pressure out at the same time due to the airflow restriction.

[shizzzon 461]

oh i'm gonna be doin port area tests. That's what is gonna take me forever in terms of testing.

I completely forgot about modifying the internal air space...

I know many competitors use small boxes with humongous external vented aero ports to achieve high pressure levels in street. I know a local guy that keeps his name under the Ky state record year after year.

hmm...

Port wars just got as complicated as SPL, hehe.

[sadistic 13]

they dont meter port wars at the windshield, they meter it literally IN the PORT. At the entrance point in the box is where the meter is placed.

So.. apparently, i must build a port to peak at 50hz for SPL, a port in the 30s for daily driving, a port in the 50hz range for bassrace(optional at the moment) and a port to peak in the range of 55-57hz for port wars.

Lots of testing to do...

they do not meter at the windshield for port war but do for bass race. if the box is smaller in the one chamber that is not being measured. this will create more pressure in the chamber being measured. but what is need is to over come the front wave. so you can do the two at once.

[sadistic 13]

all ported box have 4 waves a,b,c,d.--- line a from of cone to wind shield is front wave line b and c are the back wave to port out of the port to wind shield is line path d

just like speed of sound it travel so far at each hertz so 30 hertz travel less further then 50 hertz.. the b and c line depend on air space so you would have to box in the rear of the sub to adjust the back wave to pressurize the port. enough to hit windshield hard enough. so using a infinite baffle with to much air space will effect port tuning. any ways hope you get the point i think wall are ib right ???

I completely forgot about modifying the internal air space...

now i know you are thinking must have remind you here.lol

[Duran 387]

You need to find the right mix of port area to volume in the enclosure, I think a "small" enclosure with a port that causes the LEAST amount of air resistance but with "low" port area would be beneficial.