Lf Parts List; Final Functional Test (Stethoscope Examination) - Bowers & Wilkins 804 D3 Technical Manual

Bowers & Wilkins TECHNICAL SUPPORT

25. LF Parts List

26. Final Functional Test (
Stethoscope Examination of Speakers)
Aim of the Test
The stethoscope functional test can quickly reveal any air leaks or flaws following a
repair to a loudspeaker. The only sound coming from a loudspeaker enclosure should
be from the driver components themselves, not the surfaces or seams of the speaker
cabinet. We normally hear in stereo as a result of our ears being placed at two
separate points in space separated by several inches. When you use the stethoscope
both of your ears hear from the same single point at the position of the listening piece.
You are now listening not in stereo, but rather in mono mode which allows a greater
accuracy in examining a particular sound source.
Performing a Stethoscope Examination on a Speaker
For the following tests you should remove the chest piece from the end of the
stethoscope and listen via the tube only.
There are two options for carrying out this test:
Option 1
Drive the speaker via an amplifier and signal generator set in the low bass region, say
20 to 60 Hz, to listen for air leaks at the enclosure seams, driver mounting edges, and
jack plates. The smallest air leak will be heard clearly. Follow the same procedure as
in Option 2.
Option 2
Start by playing your choice of music (frequency) through the speaker you wish to
examine and keep the volume moderate.
The contents of this document and associated files contain confidential information that is propriety to Bowers & Wilkins, and
are intended solely for the purpose of servicing the product. The information is intended for use by service technicians familiar
with electronic products. No part of the contents should be supplied or published elsewhere.
Page 45 of 51 © Bowers & Wilkins 2016