Passive Amplifying Effect for Speakers

[korneld]

The other day, I took my cheap and properly crappy speakers of my PC and placed them face down on my desk. They sounded louder and better. If I lifted them up just a bit off the surface, they sounded even better. I do own a decibel meter and I did some testing. The speakers are somewhat louder, but only by a few decibels. But the perceived volume is so much grater.

Could someone walk me through why this is? I'd be very interested in the physics behind the phenomena.

Thanks.

 

[Inductor]

Probably what you are noticing is a different type of enclosure/effect from the normal speaker layout/position to a bandpass. Look at 4th order bandpass type, probably you would be happy...
The Subwoofer DIY Page - 4th Order Bandpass Systems
Shavano Online - Sub Woofer; 4th Order Bandpass Calculator
http://www.diyaudio.com/forums/subwoofers/186855-post-your-triple-reflex-bandpass-designs.html
http://www.diyaudio.com/forums/subwoofers/194047-what-speaker-should-i-choose-setup.html
http://www.diyaudio.com/forums/multi-way/206567-acoustic-cross-helper-woofer.html

 

[dumptruck]

Well, you could read up on how horns (all horns) work, because that sort of thing would cause the same sorts of changes in directivity and acoustic coupling with the air in the room that horns cause. I'm not saying you've created an effective horn, just that the same stuff is going on. You'd also probably have a resonant cavity between speaker and table ringing across some frequency range (which would make them sound louder in that range), and changes to the Fb & Q of the cabinet alignment, if the cabinets for these speakers are functional.

 

[korneld]

Hey, dumptruck. I think your idea fits what's going on best. I did some reading up on horns, and experimented some more and it seems that's what's going on. Thanks.