ER18RNX
Thiele/Small Parameters
One would naturally assume that manufacturers specifications
are accurate. When it comes to drivers, it appears this
is not often the case.
SEAS
specified the ER18 Vas as 32 Liters. Measurements with LMS
indicates Vas=60.9 Liters. Needless to say, adopting SEAS
Vas would obviously lead to erroneous box tuning.
For
Vas=60.9L, the optimum Bass Reflex tuning is a 38L box.
This is much too large for a Bookshelf. I decided to load
the ER18 in a 15L box instead. The outcome is a higher F3
(45Hz) with a slight hump at 150Hz. I have no qualms with
this as it gives the upper bass a very light 2dB boost.
Another
issue with the ER18 is the pronounced rising response above
500Hz. If left unattended, the midrange will be overly emphasized,
resulting in a rather tiring listening experience. After
some testing, I settled on a Baffle Step Compensation of
5dB. Together with the upper bass boost, it has the right
"bounce" in the music. The violet plot on the
right is the response of the ER18 in a 15L Bass Reflex together
with the port and Baffle Step Compensation. Frequencies
beyond 500Hz should be ignored as they are inaccurate.
Predicted Low Frequency Response
Bass Reflex (Vb=15L Fb=60Hz)
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SEAS ER18 Frequency Response
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