I am planning to build a subwoofer according to the drawing below. The closed part is W x H x D = 60 x 40 x 40 cm. The design with the open parts above and below the box for interior design reasons, not for acoustical reasons. The curved front is also a requirement for interior design, although it should be beneficial for acoustics as well.
Now I wanted to mount the woofer (30cm) in the bottom of the box. Also for aesthetical reasons.
I am wondering if the lower open space of the cabinet will cause resonances. After all, left-right it is a closed pipe of 60 cm length and front-back it is an open pipe of 40 cm. The height of the space is 16 cm.
The formula for resonance in a pipe is n v / 2 L. Where n - 1, 2, 3 ... ; v = speed of sound, L = length of the pipe.
In left-right direction the resonance frequence would be 280 Hz. The subwoofer amplifier has a filter at 80 Hz, 12 dB/oct. A frequency of 70 Hz is attenuated 24 dB, but if the pipe is resonant you should be able to hear that.
Or does this open space not behave as a pipe at all?
Now I wanted to mount the woofer (30cm) in the bottom of the box. Also for aesthetical reasons.
I am wondering if the lower open space of the cabinet will cause resonances. After all, left-right it is a closed pipe of 60 cm length and front-back it is an open pipe of 40 cm. The height of the space is 16 cm.
The formula for resonance in a pipe is n v / 2 L. Where n - 1, 2, 3 ... ; v = speed of sound, L = length of the pipe.
In left-right direction the resonance frequence would be 280 Hz. The subwoofer amplifier has a filter at 80 Hz, 12 dB/oct. A frequency of 70 Hz is attenuated 24 dB, but if the pipe is resonant you should be able to hear that.
Or does this open space not behave as a pipe at all?
No matter what you can chop everything in half and consider it as potential as a standing wave To be suspicious so. I’m sure you know
I don’t know if this is something you’re interested in or necessarily what you might be referring to But Look at what happens as a transmission line is given three folds. driver entry into the first 180 degree turn.Which splits the first two segments . Some of these things aren’t Necessarily bad. You can work it outin The actual pipe away from the closed end to the first pressure node (P min/ v max ) actual pipe away from the closed end to the first pressure node For that odd numbered harmonic interval (3/4) in pipe.
That is not really an answer I can understand. Honestly especially the second paragraph is incoherent. I know a few things about transmission lines and how to cancel certain harmonics. So the words and the sentences you write down are related to pipes and transmission lines, but the answer related to my question does not come through.
Maybe I should rephrase my question. Will the lower part of the cabinet act as a pipe. And if it does, will it cause audible resonances?
Maybe I should rephrase my question. Will the lower part of the cabinet act as a pipe. And if it does, will it cause audible resonances?
If you'd settle for a guess, the front back don't have much pipe beyond the driver. The side is 60cm out and back for some potential cancellation down near the 300Hz region. I'm not saying it will be a problem but if it is you could simply build in some deflectors.
Prototype. The only correct answer. I doubt it. Nothing but a down firing sub.
Not sure of your choice, but I only build SEALED subs. he lower the Q the better as the blend with room gain better.
Not sure of your choice, but I only build SEALED subs. he lower the Q the better as the blend with room gain better.
If the back of the 60x40x16 space is left open about 5 cm or more from the room wall, the "pipe" would not be enclosed, and little resonance would be produced.
If the back of the resonant chamber is enclosed, it likely will behave something like a pipe of 40 cm depth and a cross-sectional area of 16x60, 960 square centimeters, which will result in a narrow peak around 160 Hz. The peak probably would not be as pronounced as the Hornresp simulation below shows, but will not be subtle.
The rising response would be a bit more than the rolloff an 80 Hz second order low pass would impose, raising the acoustic crossover another octave.
The resulting acoustic crossover would be close to 24dB per octave above the peak frequency.
All the above is a rough approximation, and should be verified by more modeling with actual driver specifications.
If you are worried about resonances you can significantly reduce them at the source (est 90%) if you mount a pair of drivers push-push.
dave
dave