Hi, I'm pretty noob at speaker building. I'm building a pair of these: https://issuu.com/pali_tl/docs/beyma_enclosure/c/smei4qs
However I have a hard time finding a tube of diameter 80mm. The closest I can find is 75mm. What modifications would I have to make to the ports (length/position) if I use the 75mm tube instead?
Thanks in advance for your suggestions.
Bonus question, how much damping material would you stuff into the speakers (it's not explained in the design)?
However I have a hard time finding a tube of diameter 80mm. The closest I can find is 75mm. What modifications would I have to make to the ports (length/position) if I use the 75mm tube instead?
Thanks in advance for your suggestions.
Bonus question, how much damping material would you stuff into the speakers (it's not explained in the design)?
Download a copy of WinISD Pro and enter your woofer TS specs if they don't exist already, and then simulate the cab with the given internal volume and port dimensions.. note the shape of the cab is irrelevant it's just the internal volume as best you can estimate taking into account the volume displaced by the ports and drivers.
Once you have this you can alter the port dimensions and see what effect it has on the response, chances are it will be minimal but it never hurts to know ahead of time what the result should look like and if you are not using the drivers spec'd by the original designer this will tell you if they are a good match or not. And for any given tuning frequency the program will help you figure out the equivalent dimensions for square ports or a slot port along the bottom or triangle ports in the bottom corners(hint: treat it as a single square port and subtract the port length compensation for having a wall as part of the port.
Damping material is optional, for maximum SPL don't use any but if you find there are some resonant peaks in the response(shouldn't be with a trapazoid enclosure) line the interior walls with some damping material. The difference will be subtle but if it sounds good it is. PA speakers are never stuffed in general.
Once you have this you can alter the port dimensions and see what effect it has on the response, chances are it will be minimal but it never hurts to know ahead of time what the result should look like and if you are not using the drivers spec'd by the original designer this will tell you if they are a good match or not. And for any given tuning frequency the program will help you figure out the equivalent dimensions for square ports or a slot port along the bottom or triangle ports in the bottom corners(hint: treat it as a single square port and subtract the port length compensation for having a wall as part of the port.
Damping material is optional, for maximum SPL don't use any but if you find there are some resonant peaks in the response(shouldn't be with a trapazoid enclosure) line the interior walls with some damping material. The difference will be subtle but if it sounds good it is. PA speakers are never stuffed in general.
Last edited:
A smaller port diameter will not need to be as long for the same tuning. There will be an increase in wind noise.
Hi,
For the same tuning a smaller port is shorter.
Here it basically hardly matters.
rgds, sreten.
For the same tuning a smaller port is shorter.
Here it basically hardly matters.
rgds, sreten.
I second the download winISD I use the program and usually I can get the ports down to where I do not need a tube.
Why is it that a smaller diameter port needs a SHORTER length? It would seem that it would need to be LONGER in order to maintain the same port volume.
Yes, I did read that article. What I am asking is how the author came up with his initial 'given' that the port length-to-area ratio must remain the same.
I did the article to make it easier for people, the math was done a lot earlier (and i likely picked it from a GM post). It does work, i have done it often.
dave
dave
This is one method I found for calculating port length:
vent tuning
Indeed, the port length is inversely proportional to tuning frequency, port diameter, and box size.
vent tuning
Indeed, the port length is inversely proportional to tuning frequency, port diameter, and box size.
Oops! Should be "port length is directly proportional to port diameter and inversely proportional to tuning frequency and box size."
Thanks for all the answers! I'll try with a slightly shorter port.
Another question. The DIY design does not mention dampening material. How heavily would you dampen these speakers and how?
Another question. The DIY design does not mention dampening material. How heavily would you dampen these speakers and how?
I tend to over damp but I would rather have clarity over loudness.
I always damp the sides and back of a speaker. with a little extra behind the woofer if possible. I also damp the port tube. I test it all by knocking on it with knuckles, screwdrivers ect. The shorter it rings the better and the lower the better.
I always damp the sides and back of a speaker. with a little extra behind the woofer if possible. I also damp the port tube. I test it all by knocking on it with knuckles, screwdrivers ect. The shorter it rings the better and the lower the better.
You will not hear any change by altering the port. It's almost incidental so don't waste your time. I've built hundreds of speaker enclosures and small port error corrections are a myth.
- Status
- Not open for further replies.