Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Speaker self-destructive interference...

Status
Not open for further replies.
Externet

Externet

Advanced Member level 2
Joined
Jan 29, 2004
Messages
579
Helped
28
Reputation
58
Reaction score
29
Trophy points
1,308
Location
Mideast US
Activity points
5,665
Hi.
A speaker without cabinet/baffle placed on a table emitting its front wave upwards and its 180° out of phase rear wave reflected by the table upwards...

At 1 KHz audio, the wavelenght λ is 34cm.
The additional bouncing path traveled by the rear out-of phase wave reflected by the table upwards will cancel the front wave if is 17 cm. Is that right ?

For 2KHz audio, λ = 17cm, the cancelling effect will take place if the bouncing path is 8.5cm. Is that right ?

At 500 Hz audio, λ = 68cm, the cancelling effect will take place if the bouncing path is 34cm. Is that right ?
 

Did you notice that the linked articles are describing speakers mounted in closed cabinets. As far as I understand, your post is about a different situation.
 

Yes, the back wave bounces from the table surface in the same direction of the frontal wave and cancels it at certain distances and frequencies,
or bounces from the internal rear surface of the cabinet and affects/interacts with the cone directly producing cancellations,
or the external cabinet rear emission bounces from the back wall towards the front and does destructive interference.

Trying to eliminate as much as possible rear emission from reaching front emission setting distances and with closed/open cell sponges at the back. This is not for entertainment, but for a serious monoaural application.
 
Last edited:

Hi,

Yes, the back wave bounces from the table surface in the same direction of the frontal wave and cancels it at certain distances and frequencies,
Click to expand...

No. "In the same direction" just adds to the signal with phase shift. (vectorial addition. amplitude will become smaller if phase shift 180°...360°)
What you are talking about is "opposite direction"

But this is true only for true waves. Without case - below a certain frequency - the membrane can't build up sound pressure(true waves) because of an acoustical short circuit. Independent of wall behind the speaker.

Klaus
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top