Speaker : front ported or rear ported?
- Thread starter bazee
- Start date
Hey Cranky, I am just trying to figure out this bit. A speaker with a 7inch woofer will have a cabinet depth of about one foot if not more. So with two feet behind the cabinet, the front baffle will end up about three feet infront of the wall behind which is approx 0.9meter. (So 343 divide by 0.9 divide by 4) Wont this cause a huge back wall cancellation with the center cancellation frequency around 95Hz? Wont that cause a significant bass loss? Back wall cancellation is a serious phenomenon which is usually best avoided
Genelec Oy - Wall behind the Loudspeaker Cancellation
Hi Cranky,
Thanks for a most informative and entertaining (for me at least) post.
First a clarification of my last post. The word 'ripple difraction' actually exists at least in high school and undergraduate physics class room demonstrations (abroad, donno about India) where the word ripple refers to surface waves in water. They actually put some obstacle in the path of the propagating ripples and then study diffraction. I thought you were meaning something similar with sound waves.
At last I understood why you were so excited seeing my Canton speakers had felt on the entire front baffle. Why wouldn't the other manufacturers follow this method?
Diffraction is a natural consequence of wave nature of any signal propagation (as opposed to particle-like signal propagation). The effects of diffraction are observable at distance scales comparable to the wavelength of the wave. From the formula: speed of wave = frequency x wavelength, we see that a wavelength of 1m means a frequency of 343 Hz (1 Hz = 1 vibration per second), with the speed of sound taken as 343 m/s. From the above we see that at a distance scale of about 1m, there would be diffraction of sound for frequency around 350 Hz. If the distance is 10m, then the frq affected will be of the order of sub 50 Hz, and if the distance is very small (say 1cm) then the freq affected is around 35000 Hz = 35 KHz.
Since visible light waves have much smaller wavelengths, the diffraction effects are negligible for everyday life distances. That's why when you put an obstacle in the path of light, you get a 'sharp' shadow, but when looked at with enough resolution, one would find that the shadow is not as sharp and there is blurring at the edges of the shadow (this is an effect of diffraction).
Theoretically, of course, I know all this. But it was fascinating to read from your very illuminating post, how diffraction can affect sound from a speaker and what are some of the important parameters and considerations in a speaker design and its positioning. Thanks again.
Regards.
Thanks for a most informative and entertaining (for me at least) post.
First a clarification of my last post. The word 'ripple difraction' actually exists at least in high school and undergraduate physics class room demonstrations (abroad, donno about India) where the word ripple refers to surface waves in water. They actually put some obstacle in the path of the propagating ripples and then study diffraction. I thought you were meaning something similar with sound waves.
At last I understood why you were so excited seeing my Canton speakers had felt on the entire front baffle. Why wouldn't the other manufacturers follow this method?
Diffraction is a natural consequence of wave nature of any signal propagation (as opposed to particle-like signal propagation). The effects of diffraction are observable at distance scales comparable to the wavelength of the wave. From the formula: speed of wave = frequency x wavelength, we see that a wavelength of 1m means a frequency of 343 Hz (1 Hz = 1 vibration per second), with the speed of sound taken as 343 m/s. From the above we see that at a distance scale of about 1m, there would be diffraction of sound for frequency around 350 Hz. If the distance is 10m, then the frq affected will be of the order of sub 50 Hz, and if the distance is very small (say 1cm) then the freq affected is around 35000 Hz = 35 KHz.
Since visible light waves have much smaller wavelengths, the diffraction effects are negligible for everyday life distances. That's why when you put an obstacle in the path of light, you get a 'sharp' shadow, but when looked at with enough resolution, one would find that the shadow is not as sharp and there is blurring at the edges of the shadow (this is an effect of diffraction).
Theoretically, of course, I know all this. But it was fascinating to read from your very illuminating post, how diffraction can affect sound from a speaker and what are some of the important parameters and considerations in a speaker design and its positioning. Thanks again.
Regards.
Front Ported speakers can be kept any where even closser to the wall but rear ported speaker should be kept at least 2to 3 feet away otherwise they my tend to give you a boom. Corners are very dangerous for these kind of rear ported speakers
Homiyar.:clapping::clapping::clapping:
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