netzero
from what i understand it isnt that much...but im not an amazing box designer either
soak it in the pool, works better.
iirc, you take the lenghth of the flared part and divide it by 2. and add that to the lenght of the port and that is the total lenght of the port. I hope this made sence.
Pl8er
5,000+ posts
Can you solve it?
I think that a kurfed (i always spell it kerfed LOL) looks SEXY. Much better looking than a standard port.
Now does anyone have an explanation of how the soaking works? Do you soak, then bend then let dry? That seems like it would take a very long time.
Now does anyone have an explanation of how the soaking works? Do you soak, then bend then let dry? That seems like it would take a very long time.
I am kerfing the ports on my upcoming enclosure as well. I don't think you are required to calculate port area any different than with a standard slot vent. I've always been told the main reason to do it is because the kerf helps reduce "chuffing" at higher output. Not to mention bent MDF looks cool as hell! //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
Pioneer~Saturn
5,000+ posts
Dr. Enclosure
Yea, x2 on what propimp said...id add about half the length of the flared section to the total length...shouldnt change the tuning drastically. And yes, they look like the secks //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
Immacomputer
10+ year member
Cloud disappear
It is spelled "kerf" and not "kurf". Also, the soaking comments are from people making fun of somebody here who soaked the MDF in his pool to make it bend. This is NOT what you do with MDF. A treated plywood can handle the moisture and not bloat like MDF does.
A problem with bending is either from too shallow kerf cuts, uneven depth kerf cuts (ie, the board doesn't stay completely flat when the saw is cutting the lines), too little cuts for your intended radius, or too short of spacing between cuts (goes hand in hand with the previous).
As far as calculating the distance of the effective air mass for the port, I have found that with a circular flare, it's safe to use up to about twice the width of the port for effective port length.
You can see what I mean in this picture of an enclosure that I built:
The port was 2" wide and the effective port length extended to around the 4" wide portion. The blue line segments represent the actual port length.That wasn't measured very scientifically but I think it is a pretty safe bet for judging actual line length.
Pioneer~Saturn
5,000+ posts
Dr. Enclosure
Good post right there...great description!It is spelled "kerf" and not "kurf". Also, the soaking comments are from people making fun of somebody here who soaked the MDF in his pool to make it bend. This is NOT what you do with MDF. A treated plywood can handle the moisture and not bloat like MDF does.
A problem with bending is either from too shallow kerf cuts, uneven depth kerf cuts (ie, the board doesn't stay completely flat when the saw is cutting the lines), too little cuts for your intended radius, or too short of spacing between cuts (goes hand in hand with the previous).
As far as calculating the distance of the effective air mass for the port, I have found that with a circular flare, it's safe to use up to about twice the width of the port for effective port length.
You can see what I mean in this picture of an enclosure that I built:
The port was 2" wide and the effective port length extended to around the 4" wide portion. The blue line segments represent the actual port length.That wasn't measured very scientifically but I think it is a pretty safe bet for judging actual line length.
OP
netzero
10+ year member
USMC
- Thread Starter
- #10
Thanks everyone for the info, its all starting to come to me how im going to go about it. Immacomputer especially, thanks man. Few questions to your diagram, So If you don't calculate the port 'inset' from the box front and compensate by extending the entrance of the port, i'm assuming you might tune your box 1~2 Hz higher than you wanted?
Also, do you have any methods or number to help. Like: blade depth/blade width, amount of cuts, frequency of cuts, and when to start and stop cutting? Thanks
Also, do you have any methods or number to help. Like: blade depth/blade width, amount of cuts, frequency of cuts, and when to start and stop cutting? Thanks
Immacomputer
10+ year member
Cloud disappear
If you count the end of the flare as effective length, then yes, your port length would be shorter than you designed and you might be off by a couple Hz.
I can't speak for anybody else as I don't know how other people do it but this is the methodology that I have used in the past and it's always worked out.
Blade depth: 5/8" for 3/4" MDF works but I usually go a little deeper to help it bend. Going deeper will usually make it easier to see the kerf cuts but the number of cuts also affects that.
Blade width: I use a 10" table saw blade that is 1/8" wide.
Amount of cuts: Well, this one can be simple or tricky. You can really choose your own destiny here as far as how many cuts you want to do but there is minimum. The minimum amount of cuts you can do to make a 90* bend is 11 cuts. Any less than that, and you will not get 90*. If you go with 11 cuts though, your angle will actually be greater than 90*. This can be good and bad and it will vary with different blade widths (I use 1/8" but some blades may be larger or smaller). If you're going to fill the gap then it is fine and the more cuts you make the easier it will bend. It will also have a smoother flow with more cuts. But, you do lose strength so unless you fiberglass or epoxy from the inside, you shouldn't make too many cuts over 11 for a 90* bend. I usually do 10 cuts and then I don't get a perfect 90* angle but I prefer the look and the wood all aligns on the inside. You can see what I mean about getting slightly less than 90* in this picture:
Cut spacing: This will depend on the radius you want. What you have to first decide on is the inner flare radius (Rf) and angle (θ). The angle will give you the number of cuts (Nc) you need. I use these equations to get line spacing (Ls):
Ls = [(2*Rf*pi) / (θ/360) - (Nc*Bw)] / Nc
Where Bw is your blade width. Also note that the angle (θ) needs to be in degrees in order to get the actual arc length for the piece of wood. It seems confusing but it's really simple. The numbers work well enough that you can incorporate it with any flare angle, radius, and number of cuts.
Starting point will be based on when you want the flare to begin and the ending point will just happen as you make the cuts with the constant spacing. Let me know if any of that was unclear.
I can't speak for anybody else as I don't know how other people do it but this is the methodology that I have used in the past and it's always worked out.
Blade depth: 5/8" for 3/4" MDF works but I usually go a little deeper to help it bend. Going deeper will usually make it easier to see the kerf cuts but the number of cuts also affects that.
Blade width: I use a 10" table saw blade that is 1/8" wide.
Amount of cuts: Well, this one can be simple or tricky. You can really choose your own destiny here as far as how many cuts you want to do but there is minimum. The minimum amount of cuts you can do to make a 90* bend is 11 cuts. Any less than that, and you will not get 90*. If you go with 11 cuts though, your angle will actually be greater than 90*. This can be good and bad and it will vary with different blade widths (I use 1/8" but some blades may be larger or smaller). If you're going to fill the gap then it is fine and the more cuts you make the easier it will bend. It will also have a smoother flow with more cuts. But, you do lose strength so unless you fiberglass or epoxy from the inside, you shouldn't make too many cuts over 11 for a 90* bend. I usually do 10 cuts and then I don't get a perfect 90* angle but I prefer the look and the wood all aligns on the inside. You can see what I mean about getting slightly less than 90* in this picture:
Cut spacing: This will depend on the radius you want. What you have to first decide on is the inner flare radius (Rf) and angle (θ). The angle will give you the number of cuts (Nc) you need. I use these equations to get line spacing (Ls):
Ls = [(2*Rf*pi) / (θ/360) - (Nc*Bw)] / Nc
Where Bw is your blade width. Also note that the angle (θ) needs to be in degrees in order to get the actual arc length for the piece of wood. It seems confusing but it's really simple. The numbers work well enough that you can incorporate it with any flare angle, radius, and number of cuts.
Starting point will be based on when you want the flare to begin and the ending point will just happen as you make the cuts with the constant spacing. Let me know if any of that was unclear.
If you count the end of the flare as effective length, then yes, your port length would be shorter than you designed and you might be off by a couple Hz.
I can't speak for anybody else as I don't know how other people do it but this is the methodology that I have used in the past and it's always worked out.
Blade depth: 5/8" for 3/4" MDF works but I usually go a little deeper to help it bend. Going deeper will usually make it easier to see the kerf cuts but the number of cuts also affects that.
Blade width: I use a 10" table saw blade that is 1/8" wide.
Amount of cuts: Well, this one can be simple or tricky. You can really choose your own destiny here as far as how many cuts you want to do but there is minimum. The minimum amount of cuts you can do to make a 90* bend is 11 cuts. Any less than that, and you will not get 90*. If you go with 11 cuts though, your angle will actually be greater than 90*. This can be good and bad and it will vary with different blade widths (I use 1/8" but some blades may be larger or smaller). If you're going to fill the gap then it is fine and the more cuts you make the easier it will bend. It will also have a smoother flow with more cuts. But, you do lose strength so unless you fiberglass or epoxy from the inside, you shouldn't make too many cuts over 11 for a 90* bend. I usually do 10 cuts and then I don't get a perfect 90* angle but I prefer the look and the wood all aligns on the inside. You can see what I mean about getting slightly less than 90* in this picture:
Cut spacing: This will depend on the radius you want. What you have to first decide on is the inner flare radius (Rf) and angle (θ). The angle will give you the number of cuts (Nc) you need. I use these equations to get line spacing (Ls):
Ls = [(2*Rf*pi) / (θ/360) - (Nc*Bw)] / Nc
Where Bw is your blade width. Also note that the angle (θ) needs to be in degrees in order to get the actual arc length for the piece of wood. It seems confusing but it's really simple. The numbers work well enough that you can incorporate it with any flare angle, radius, and number of cuts.
Starting point will be based on when you want the flare to begin and the ending point will just happen as you make the cuts with the constant spacing. Let me know if any of that was unclear.
what's thr pros and cons of having flared vs. slot? or is it all just cosmetic?
tommyk90
5,000+ posts
THE WHOLE THING!!!
It's also a slim chance that you will even notice a slight change in the tuning frequency with a kerfed port the same length as a normal slot port anyways, especially once the enclosure is placed into a vehicle.
At that point the resonant frequency of the vehicle and the car acoustics can change the tuning/frequency response.
Immacomputer gave a very clear and simple explanation though.
Plus most people probably don't factor in for end correction anyways, which will drop the tuning. I usually don't bother either because the change is fairly miniscule; 1 hz is the most i've seen.
At that point the resonant frequency of the vehicle and the car acoustics can change the tuning/frequency response.
Immacomputer gave a very clear and simple explanation though.
Plus most people probably don't factor in for end correction anyways, which will drop the tuning. I usually don't bother either because the change is fairly miniscule; 1 hz is the most i've seen.
OP
netzero
10+ year member
USMC
- Thread Starter
- #15
Well, thank you everyone, this has definitely helped me figure out what im gonna do, and i think with some practice the kerfed port is gonna be sweet! Immacomputer, I really like the less than 90* bend there, it adds even more artistic flavor to the already sexy flare. And the perfect explanation on the distance formula, thanks man. Hope this helps anyone else with questions on kerfed porting!
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