Interesting findings. Read through your case study report, I like the analytical approach to try and figure it out fundamentally. However, I sometimes find that I can get caught up on too many details of theory and lose out on the aspect of actually doing something, which is where I find the joy. Have to turn my engineer brain off a bit when doing personal projects and not work haha.
Yes, I thought about this as well, but I think it is somewhat overly complex (in a different way, it's kind of indescribable to me?) from what I wanted this build to be. Active/DSP is something I am very interested in and will probably mess with in the future, but my gut always pushes me back to passive due to the "simplicity" or "elegance" it has. At this budget, active would definitely increase performance, but I think there is something satisfying about knowing it won't be perfect that I enjoy.
Additionally, I modified the port again based on Tenson's advice to be a bit bendy (due to space constraints in the box) and to reduce rapid velocity changes from the original sharp bend, increasing flow turbulence within the port and chuffing. I have 3D printers already so I'm not concerned about manufacturing it. I could go even more wild with the geometry, but I think the performance gains would be diminishing at that point.
From Vituix with an updated volume of 31L, Fb 32 Hz, and port diameter of 3" at 130W, port velocity will be ~24 m/s which is within the ranges A4eaudio recommended.
The port end in the model is only capped so I can measure true internal volume of the box, not including the port volume. Total volume, not including port, bracing, ect is 31.1L. I don't know the exact volume of the RS270, but I am assuming it will put me in the 30-30.5L range.
Once built and damped, I am not expecting the simulations to match reality for the tuned port length, but I plan on making the port in two halves, so I can swap the lower half to easily increase/decrease length until desired.
Keep in mind some of the assumptions that are suggesting chuffing will be a problem may be overstated. The modelling is at 130 watts, which is when the driver reaches xmax, which is a normal modelling perspective. But it is also common to reach xmax before you actually reach the power handling limits of the driver. The RS270-4 has Power Handling RMS of 100 watts and MAX at 200 watts.
Nothing wrong with modelling at 130 watts, the driver can handle hitting some peaks at that level, but is that really the power level we are worried about when trying to worry about port chuffing? (I'm not saying it ISN'T the level to worry about, just asking the question.)
Bottom line...I bet your model in #21 is fine and if you went with a 2.5 inch or 2.75 inch (if you are 3D printing) it would be fine too.
Nothing wrong with modelling at 130 watts, the driver can handle hitting some peaks at that level, but is that really the power level we are worried about when trying to worry about port chuffing? (I'm not saying it ISN'T the level to worry about, just asking the question.)
Bottom line...I bet your model in #21 is fine and if you went with a 2.5 inch or 2.75 inch (if you are 3D printing) it would be fine too.
I'd think about having a wooden brace that does double duty bracing the woofer magnet and offering a plane/face for the inside end of the port to terminate at.
You can pinch the middle of the tube a little bit to shorten the tube if desired - air speed at the middle of the port is not really a problem, only at the terminus.
You can pinch the middle of the tube a little bit to shorten the tube if desired - air speed at the middle of the port is not really a problem, only at the terminus.
indeed it will never see 130 watts under normal listening.
So 24 m/s rather respectable for exceeding the thermal rating anyways.
Be fine
single 3" works fine, likewise x2 2"
either way same old same old.
It is home HiFi not live audio.
Its half space transfer function in sim.
Real life the 6 dB drop below 300 Hz
Gets made up for when you turn up the
Bass knob Eq.
People overthink ports to much.
Your either tuned 3 to 6 Hz above or below
Driver Fs and enough volume to make the suspension
happy. The end, just a plain old velocity ramp.
Rather tune it low so when you actually crank the
equalizer. not hear the port hum.
Its tuned to 30 Hz so at least its nowhere close
to annoying little speakers tuned at 60 Hz
Should be a enjoyable speaker for you
So 24 m/s rather respectable for exceeding the thermal rating anyways.
Be fine
single 3" works fine, likewise x2 2"
either way same old same old.
It is home HiFi not live audio.
Its half space transfer function in sim.
Real life the 6 dB drop below 300 Hz
Gets made up for when you turn up the
Bass knob Eq.
People overthink ports to much.
Your either tuned 3 to 6 Hz above or below
Driver Fs and enough volume to make the suspension
happy. The end, just a plain old velocity ramp.
Rather tune it low so when you actually crank the
equalizer. not hear the port hum.
Its tuned to 30 Hz so at least its nowhere close
to annoying little speakers tuned at 60 Hz
Should be a enjoyable speaker for you
Port noise at the back is far less anoying than small vents ending on the front baffle. Large ports simply work better, because less energy is lost in the transitioning from the inside to the outside. Your port from post 21 should be perfect. You will not hear any unwanted noise from it at any SPL. The driver is no monster...