Hello,
I am using QSpeaker to design my ported enclosure. For this example i will be talking about built around Dayton TCP115 8 ohm, 2.3L enclosure and 65Hz resonant frequency. All well. Now to port.
The program will give me port diameter of 3.2cm and length roughly 22cm. All is well. Now i want a port of diameter of 2cm and it will give me length of around 8cm. But now if i change volume of enclosure, it will again set the port diameter to 3.2cm, which seems to be the programs favourite diameter.
So my question is this. Am i perfectly alright using 2cm diameter port of length 8cm, even though program seems to favor 3.2cm x 22cm ? I read that larger diameter results in less port noise. But as far as F3, will the 2 roughly compare the same ?
The reason i am asking is that shorter port is easier to include in this small enclosure than a large port and i would like to know if i am losing bass due to smaller diameter or i am not.
I am using QSpeaker to design my ported enclosure. For this example i will be talking about built around Dayton TCP115 8 ohm, 2.3L enclosure and 65Hz resonant frequency. All well. Now to port.
The program will give me port diameter of 3.2cm and length roughly 22cm. All is well. Now i want a port of diameter of 2cm and it will give me length of around 8cm. But now if i change volume of enclosure, it will again set the port diameter to 3.2cm, which seems to be the programs favourite diameter.
So my question is this. Am i perfectly alright using 2cm diameter port of length 8cm, even though program seems to favor 3.2cm x 22cm ? I read that larger diameter results in less port noise. But as far as F3, will the 2 roughly compare the same ?
The reason i am asking is that shorter port is easier to include in this small enclosure than a large port and i would like to know if i am losing bass due to smaller diameter or i am not.
The larger diameter port is preferable for the reason you state (less chance of 'chuffing' at high volume). The bass will be 'cleaner' with the larger diameter port.
Provided the internal end of the tube is at least 8cm from the wall of the enclosure, you are good to go. Otherwise you can use an elbow to fold the tube into a right angle, in which case the effective length is the distance measured through the centre of the arrangement.
Provided the internal end of the tube is at least 8cm from the wall of the enclosure, you are good to go. Otherwise you can use an elbow to fold the tube into a right angle, in which case the effective length is the distance measured through the centre of the arrangement.
Thank you, that is great that i can adjust the diameter of the port.
Can i ask why the port end has to be 8cm away from the end of the enclosure and what happens if it is not ?
Can i ask why the port end has to be 8cm away from the end of the enclosure and what happens if it is not ?
You change the effective length of the port that way - the zone of high velocity air in the port and around its ends constitute the momentum element in the acoustic circuit.
A ported enclosure is like an LC circuit, port is like an inductor storing energy in momentum, volume is like the capacitor, storing energy in the pressure x volume. There is a gradual transition from the port to the volume, constricting the flow at that point shifts the transition, and thus the resonant frequency of the ported enclosure.
A ported enclosure is like an LC circuit, port is like an inductor storing energy in momentum, volume is like the capacitor, storing energy in the pressure x volume. There is a gradual transition from the port to the volume, constricting the flow at that point shifts the transition, and thus the resonant frequency of the ported enclosure.
In my current speaker which is sadly glued and screwed together, the port isnt 8cm away, it is only 3cm away from wall.
- How in practice would that effect the bass ? The box is otherwise properly calculated through a program.
Also, when i cover the port with my hand, i barely notice any difference while in reality F3 difference with port vs non port is 100Hz vs 60Hz. Should i notice the difference with my ear ?
- How in practice would that effect the bass ? The box is otherwise properly calculated through a program.
Also, when i cover the port with my hand, i barely notice any difference while in reality F3 difference with port vs non port is 100Hz vs 60Hz. Should i notice the difference with my ear ?
I have a little update. I did a mistake of testing port in that ultra bass song that makes almost all my little speakers sound boomy. So instead i listened to a song from prodigy and i can tell you, when i cover the port, the difference is HUGE. Really huge. So it feels good knowing the port works.
I am not sure what my ports resonant frequency is, is that the enclosure resonant frequency, which i think i set at 65Hz ? And what am i going to hear when i play that frequency ?
I have so much to learn, just when i think i am getting a grasp on the basics, so many new information comes.
I am not sure what my ports resonant frequency is, is that the enclosure resonant frequency, which i think i set at 65Hz ? And what am i going to hear when i play that frequency ?
I have so much to learn, just when i think i am getting a grasp on the basics, so many new information comes.
The point of a port is to extend the bass response below what the driver and selaed enclosure can manage. Blocking the port will give the sealed box response. The correct tuning of a port will extend the bass response without too much of a peak/dip, but the air movement in the port will definitely show resonance (try holding a feather in front of it and sweep a tone up and down!). As frequency rises and the port goes off resonance the normal bass driver response should be rising up to compensate and produce a flat total response (or nearly so).
The range a port operates at is quite small, it might extend a response down to 40Hz from 60Hz, something like that, but without having to make the enclosure a lot larger. Try and make a port do too much to the response and there will be a big dip in the middle.
The range a port operates at is quite small, it might extend a response down to 40Hz from 60Hz, something like that, but without having to make the enclosure a lot larger. Try and make a port do too much to the response and there will be a big dip in the middle.
Thank you for your response. I have been playing with graphs including different speakers. And what is funny, for some speakers, the lower the resonant frequency, the lower the F3 value. But for others, its not like that, i set it at 40Hz resonant frequency and F3 will be at 110Hz. Then as i increase the resonant frequency, the F3 value drops to 60Hz.
So much more to learn. Btw, how will i know what frequencies the bass port "plays" ? Does it have anything to do with resonant frequency ?
So much more to learn. Btw, how will i know what frequencies the bass port "plays" ? Does it have anything to do with resonant frequency ?
The mass of air in the port vibrates in phase with the loudspeaker cone over a selected band of frequencies and so enhances the bass output of the system.
The optimum box tuning frequency depends on the Q (resonance magnification at fs) of the speaker and varies from frequencies much lower than the free air resonance, fs, of the speaker to frequencies above the free air resonance.
The optimum tuning will give a flat bass response with a low f3.
The optimum box tuning frequency depends on the Q (resonance magnification at fs) of the speaker and varies from frequencies much lower than the free air resonance, fs, of the speaker to frequencies above the free air resonance.
The optimum tuning will give a flat bass response with a low f3.