Bandpass port question

[0kriz]

A port are tuned to a given frequency however, the port does provide output above an below tuning with dismising returns. If chamber 1 port is tuned to 40 hz and chamber 2 port is tuned to 65 hz, will the 40hz port’s output at 65hz cancel out the 65hz tuned port at 65hz? If so, what about at 52 hz where both the ports are equally active? How close can ports be before they start working against each other? If 10% of port velocity at one port cancel the output of the other port, then that is 10% waste in output potential. It is also wasted power, heat and stress on the subwoofer driver.

Click to read more...

 

[winkychevelle 10+ year member]

Depends on the design.

Model your design before building it

This is the 6th order I'm currently going to build.
1cube at 28hz and .75cube at 55hz two nvx vcw104v3 isobaric. Goal was the flattest response 30-65hz

 

[0kriz]

Depends on the design.

Model your design before building it

This is the 6th order I'm currently going to build.
1cube at 28hz and .75cube at 55hz two nvx vcw104v3 isobaric. Goal was the flattest response 30-65hz
View attachment 44455

Looks nice man. Im working on a small 6.5’’ bandpass now, the tuning is low 30s and low 60s somewhere. Im currently trying to reduce port noise so I can increase port velocity. Due to its small size, I can only fit 2x 2’’ ports per chamber, which is why im qurious if the ports cancel each other in any significant way. Ill need to get as much spl out of the ports as possible for maximum fun.

My experience with free simulation software is that they dont do well with 6th order bandpass. I prefere tuning both ports while building the enclosure. Beside that, any imperfections is corrected with eq.

I have heard that tuning one octave away is a nice rule, and I see many follows it, I have yet to find any explanation as to why it should not be any closer. Internet is flooded with bro sience so finding answeres is not easy.

 

[winkychevelle 10+ year member]

Looks nice man. Im working on a small 6.5’’ bandpass now, the tuning is low 30s and low 60s somewhere. Im currently trying to reduce port noise so I can increase port velocity. Due to its small size, I can only fit 2x 2’’ ports per chamber, which is why im qurious if the ports cancel each other in any significant way. Ill need to get as much spl out of the ports as possible for maximum fun.

My experience with free simulation software is that they dont do well with 6th order bandpass. I prefere tuning both ports while building the enclosure. Beside that, any imperfections is corrected with eq.

I have heard that tuning one octave away is a nice rule, and I see many follows it, I have yet to find any explanation as to why it should not be any closer. Internet is flooded with bro sience so finding answeres is not easy.

Reducing port noise only comes from reducing port air velocity so you have a conundrum.

 

[0kriz]

Reducing port noise only comes from reducing port air velocity so you have a conundrum.

It can also be reduced by flared ports, smooth surfaces, no corners or bends, proper distance from walls to port or atleast an air flow guiding wall, distance the ports tuning futher away if they cancel each others output to some degree. Low cut at tuning in the lower chamber also help since most airpressure below tuning is wastefull and does not provide any meaningfull amount of sound output. Im not sure if the same apply for the high tuned port, but I think so, from what I understad the same happens above tuning for the high tuned port as below tuning for the low tuned port, but im not sure. I dont understand bandpass design enough yet.

 

[winkychevelle 10+ year member]

It can also be reduced by flared ports, smooth surfaces, no corners or bends, proper distance from walls to port or atleast an air flow guiding wall, distance the ports tuning futher away if they cancel each others output to some degree. Low cut at tuning in the lower chamber also help since most airpressure below tuning is wastefull and does not provide any meaningfull amount of sound output. Im not sure if the same apply for the high tuned port, but I think so, from what I understad the same happens above tuning for the high tuned port as below tuning for the low tuned port, but im not sure. I dont understand bandpass design enough yet.

This should be included into the base box design.

 

[0kriz]

This should be included into the base box design.

Are there any other places it can be included? Just qurious

 

[winkychevelle 10+ year member]

Are there any other places it can be included? Just qurious

Personally I'd likely go slot ported with the low tuned side of the box and aero on the high tuned side. 6th orders are just big by design