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Author Topic: Why Can I Hear Music From A Speaker Pointing Away From Me ?  (Read 1857 times)

Offline neilep

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Dear Speakerologists,

As a sheepy I am of course an avid music luffer. Yep, it's all I think about really from the minute I awake to the moment I fall asleep, listening to music is all I think about. As an audiophile sheepy i of course have invested in a high end audio system and to make the best of it I always make sure I sit in front of it as sitting in front of it is where I like to sit. However, perchance one day I ventured behind my speakers thusly:




Me Venturing behind My Speakers Thusly !

Nice eh ? (everything is in scale by the way)


Lo and behold !!...strike-a-light-guvna and luvaduck !!...I could still hear the music even though I was behind the speakers !!!....also...my speakers are outside in the middle of a field so ewe can't go saying the music is rebounding off some walls and ceiling stuff !!...so there !!!....nyahh nyahhh !!


So, explain it to me if you can please what miracle of science and wonderment allows me to hear music from a speaker that is in fact pointing away from me ?....I mean the drive units are pointing one way and I'm standing behind it !!..It's impossible !!

Why Can I Hear Music From A Speaker Pointing Away From Me
?


Can ewe help me ?


Hugs and shmishes



mwah mwah


Neil
Do Ewe Remember Din Plugs ?
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« Last Edit: 09/03/2012 17:47:41 by neilep »


 

Offline JP

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Hi Neil.  There are probably two things going on here: the engineering of the speaker and the basic physics limits on how sound moves.  I don't know much about speaker design, so I can only address the basic physics. 

The physical limitation has to do with how small your speaker is compared to the wavelength of the sound coming out of it.  There's a fundamental property of waves that says that the if the size of the wave source gets small (compared to the wavelength of the sound) the wave has to spread out quickly as it moves.  Now, if I did my calculations correctly, sound wavelengths are roughly 1 cm to 1 meter in size, so unless you have monster speakers, your speakers are roughly the same size as the wavelengths they're producing.  This means that much of the sound spreads out into all directions, including backwards.  If you listen carefully, you'll probably find that higher frequency sounds (shorter wavelengths) sound best in front of the speakers, since they have better directionality by virtue of being smaller wavelength.

There's also probably an effect of the speaker's case being designed to block sound from coming out the back/sides.  To block a wave, you generally need an absorbing material thicker than its wavelength, which would be impractical for many speakers and wavelengths...
 

Offline neilep

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Hi Neil.  There are probably two things going on here: the engineering of the speaker and the basic physics limits on how sound moves.  I don't know much about speaker design, so I can only address the basic physics. 

The physical limitation has to do with how small your speaker is compared to the wavelength of the sound coming out of it.  There's a fundamental property of waves that says that the if the size of the wave source gets small (compared to the wavelength of the sound) the wave has to spread out quickly as it moves.  Now, if I did my calculations correctly, sound wavelengths are roughly 1 cm to 1 meter in size, so unless you have monster speakers, your speakers are roughly the same size as the wavelengths they're producing.  This means that much of the sound spreads out into all directions, including backwards.  If you listen carefully, you'll probably find that higher frequency sounds (shorter wavelengths) sound best in front of the speakers, since they have better directionality by virtue of being smaller wavelength.

There's also probably an effect of the speaker's case being designed to block sound from coming out the back/sides.  To block a wave, you generally need an absorbing material thicker than its wavelength, which would be impractical for many speakers and wavelengths...

This is fantastic  !..Thank you so much JP.

It's difficult to grasp how that when the drive units are pointing one way that the sound can also travel backwards !..and yet...I witness this all the time !. ...I am very aware of how directional the HF frequencies are and how omni directional low frequencies are...hence the fact that subwoofers can really be placed anywhere in a room. I just never really understood it.

Thanks again for your great reply !
 

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