Mode zapper

[PaulP]

I just happened across this patent for a device that looks to me like it could
be pretty useful in treating modes. It is made up of a microphone, amp and
speakers that you stick in a corner or other suitable place. There's a small
circuit (I haven't yet read what it does exactly) that produces the inverse of
what the microphone detects which is then output by the speakers cancelling
things out.

Here are two sources for the US patent no. 4,899,387 :

• Online pdf document
• US Patent Office document

There aren't many ways of dealing with really low frequency modes so if this
thing works at all it could be useful.

Apparently this patent has expired due to lack of payment so clone away.

Paul P

[jdg]

there's the bag end E-trap:
http://www.bagend.com/bagend/downloads/ETrap.pdf

[PaulP]

Originally Posted by jdg

there's the bag end E-trap:
http://www.bagend.com/bagend/downloads/ETrap.pdf

Yeah I finally came across it a few minutes ago. I'd heard of it before but
couldn't remember the name. I believe many people here know of it but does
anyone know how it performs ? The Bag End E-trap appears to work at two
specific frequencies which seems reasonable.

[Edit: I just did a search here on the Bag End E-trap and there is useful
information to be found.]

There are a few more patents referred to in the Pass patent that also look
interesting. With speaker management DSP getting pretty cheap active
treatment may be becoming a possibility.

Paul P