Active crossover for use with multi-driver in-ear monitors
http://www.google.com/patents/US20060193479
In-ear monitor with shaped dual bore
http://www.google.com/patents/US7263195
https://www.google.com/patents/US8538061
https://www.google.com/patents/US8548186
https://www.google.com/patents/US3002058
https://www.google.com/patents/US7657048
https://www.google.com/patents/US8401215
http://www.google.com/patents/US8135163
http://www.google.com/patents/US7869610
http://www.google.co.uk/patents/US7860264
http://www.google.com.tr/patents/US8385583
http://www.google.com/patents/US20070058833