Hello all, i am new here.
I have a question about end correction. I have attached pictures of the port style im wondering about.
any guesses at what the end correction would be for a port this style? note how it flanges at each end.
I'm thinking it would be around 3.227 ????? but thats just a guess....
shnitzel
I have a question about end correction. I have attached pictures of the port style im wondering about.
any guesses at what the end correction would be for a port this style? note how it flanges at each end.
I'm thinking it would be around 3.227 ????? but thats just a guess....
shnitzel
Attachments
3.227? WTF?
I know CAD and have no idea what you have drawn.
Buy some cheap OSB and make a test box, or just build it and live with it. No way to calculate end correction for such a complicated case - and it depends on the surroundings as well.
I know CAD and have no idea what you have drawn.
Buy some cheap OSB and make a test box, or just build it and live with it. No way to calculate end correction for such a complicated case - and it depends on the surroundings as well.
You'll have to calculate it like a two segment back loaded horn with the vent proper being conical and the back section/terminus as parabolic plus any boundaries of course. Hornresp will get you in the ballpark, but ideally you'll want to use AkAbat.
GM
GM
that makes sense that it would be similar or the same style calculations as a "2 segment back loaded horn".
attached is the usual port end correction jpg in german. the worst case situation on the diagram is the bottom right one. which has an end correction factor of 2.227.
the port on the box concept im working on is the total worst case scenario. the port is bordered by 3 walls on BOTH the inside and outside wall of the port. the cad drawings are only conceptual for this discussion. this isnt my final drawing.
so, i took worst case scenario from that german jpg, (2.227) and i added 1 to it. ha ha ha. not that scientific.
hopefully that clears up the style of port im up to. i really like the attached jpg, it just needs a few more scenarios 😉
shnitzel
attached is the usual port end correction jpg in german. the worst case situation on the diagram is the bottom right one. which has an end correction factor of 2.227.
the port on the box concept im working on is the total worst case scenario. the port is bordered by 3 walls on BOTH the inside and outside wall of the port. the cad drawings are only conceptual for this discussion. this isnt my final drawing.
so, i took worst case scenario from that german jpg, (2.227) and i added 1 to it. ha ha ha. not that scientific.
hopefully that clears up the style of port im up to. i really like the attached jpg, it just needs a few more scenarios 😉
shnitzel
Attachments
ok, after some more research i have new answers AND questions. ha ha ha.
the first diagram says the effective port length is an extra 1/2 the width of the port. if the port style was the same on the opposite end would i add an extra 1/2 the port width for that end too?
and in the second diagram. i have changed how the face of the port. how much effect on this do you think this would have?
shnitzel
the first diagram says the effective port length is an extra 1/2 the width of the port. if the port style was the same on the opposite end would i add an extra 1/2 the port width for that end too?
and in the second diagram. i have changed how the face of the port. how much effect on this do you think this would have?
shnitzel
Attachments
Nobody can tell you, you will have to build it and see.
The first two cases in your post 4 are the sum of the end corrections for flanged (0.85) and free diaphragms (0.6...) and are each essentially the mass of air on each side of the port that moves without being compressed. All the rest are some sort of empirical GUESS. Empirical means someone built it and made a guess at end correction. You should be very skeptical of all of the info on that image.
Here is an empirical study that calls the 0.732 value into question.
vent tuning
Let's say you come up with an end correction for a box in the middle if a field, then you put that box in a car or a small or large room. The tuning will actually probably change slightly depending on a number of factors, proximity to boundaries, etc.
Build it and find out...you are wasting your time trying to calculate it.
The first two cases in your post 4 are the sum of the end corrections for flanged (0.85) and free diaphragms (0.6...) and are each essentially the mass of air on each side of the port that moves without being compressed. All the rest are some sort of empirical GUESS. Empirical means someone built it and made a guess at end correction. You should be very skeptical of all of the info on that image.
Here is an empirical study that calls the 0.732 value into question.
vent tuning
Let's say you come up with an end correction for a box in the middle if a field, then you put that box in a car or a small or large room. The tuning will actually probably change slightly depending on a number of factors, proximity to boundaries, etc.
Build it and find out...you are wasting your time trying to calculate it.
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of course. this isnt my first stab at building boxes...
im all about experimenting. but you cant blame me for looking for a bit of a head start.
in the end yes, i will build it!!!! but after i research and plan as much as i can!
shnitzel
im all about experimenting. but you cant blame me for looking for a bit of a head start.
in the end yes, i will build it!!!! but after i research and plan as much as i can!
shnitzel
Sure, but...
you can also plan too much.
If you "waste" too much time planning you could have build maybe 3 enclosures and you would`ve gained valuable experience instead of theoretical "planning".
The head start will come with practical experience.
Also the planning phase will shorten considerably with experience.
(MDF)/OSB is cheap.
Regarding port tuning, there are a lot of factors which you cannot really plan.
Driver tolerances, final placement, room effects, possibly wrong parameters (made up, typo, etc.), often a somewhat higher tuning will get you where you want to because of room effects (if indoor), ...
If you want to build just one enclosure use variable length ports.
Also it is not just the tuning, it is also port area, length and possible losses.
I was never able to calculate the perfect port length. Listen, measure, open the box, shorten the port. Good? No. Again.
I recommend a test enclosure of cheap (MDF) or OSB.
For sq place the inner end of the port as close to the cone as you can.
Also you want port area to be large and port length to be short.
While both isn`t possible you need to find a compromise.
you can also plan too much.
If you "waste" too much time planning you could have build maybe 3 enclosures and you would`ve gained valuable experience instead of theoretical "planning".
The head start will come with practical experience.
Also the planning phase will shorten considerably with experience.
(MDF)/OSB is cheap.
Regarding port tuning, there are a lot of factors which you cannot really plan.
Driver tolerances, final placement, room effects, possibly wrong parameters (made up, typo, etc.), often a somewhat higher tuning will get you where you want to because of room effects (if indoor), ...
If you want to build just one enclosure use variable length ports.
Also it is not just the tuning, it is also port area, length and possible losses.
I was never able to calculate the perfect port length. Listen, measure, open the box, shorten the port. Good? No. Again.
I recommend a test enclosure of cheap (MDF) or OSB.
For sq place the inner end of the port as close to the cone as you can.
Also you want port area to be large and port length to be short.
While both isn`t possible you need to find a compromise.
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