<s>
Motional	B-Device
Feedback	I-Device
(	O
MFB	O
)	O
is	O
an	O
active	O
high	O
fidelity	O
loudspeaker	O
system	O
which	O
was	O
developed	O
by	O
the	O
Dutch	O
Philips	O
brand	O
in	O
the	O
early	O
1970s	O
.	O
</s>
<s>
The	O
loudspeakers	O
have	O
built-in	O
amplifiers	O
and	O
feature	O
a	O
feedback	O
sensor	O
on	O
the	O
woofer	B-Device
.	O
</s>
<s>
The	O
sensor	O
measures	O
the	O
output	O
signal	O
of	O
the	O
woofer	B-Device
and	O
compares	O
it	O
to	O
the	O
amplifier	O
input	O
signal	O
.	O
</s>
<s>
Any	O
distortion	O
induced	O
by	O
the	O
enclosure	O
or	O
the	O
woofer	B-Device
itself	O
is	O
immediately	O
corrected	O
by	O
the	O
feedback	O
loop	O
.	O
</s>
<s>
Although	O
the	O
Motional	B-Device
Feedback	I-Device
technology	O
had	O
been	O
experimented	O
with	O
for	O
several	O
years	O
,	O
Philips	O
was	O
the	O
first	O
company	O
to	O
successfully	O
create	O
a	O
working	O
prototype	B-Application
and	O
create	O
a	O
commercial	O
product	O
line	O
of	O
loudspeakers	O
and	O
equipment	O
.	O
</s>
<s>
The	O
product	O
manager	O
of	O
the	O
Philips	O
High	O
Fidelity	O
group	O
,	O
Piet	O
Gouw	O
,	O
was	O
responsible	O
for	O
the	O
launch	O
of	O
most	O
of	O
the	O
Motional	B-Device
Feedback	I-Device
loudspeakers	O
and	O
other	O
high	O
fidelity	O
equipment	O
.	O
</s>
<s>
Today	O
,	O
at	O
the	O
age	O
of	O
86	O
,	O
Gouw	O
is	O
an	O
active	O
member	O
of	O
MFBfreaks.com,	O
the	O
home	O
of	O
Motional	B-Device
Feedback	I-Device
collectors	O
.	O
</s>
<s>
He	O
shares	O
historical	O
stories	O
and	O
answers	O
questions	O
on	O
the	O
MFBfreaks.com	O
forum	B-Application
.	O
</s>
<s>
Today	O
,	O
Motional	B-Device
Feedback	I-Device
is	O
used	O
by	O
high-end	O
audio	O
designers	O
.	O
</s>
<s>
Grimm	O
Audio	O
/	O
Tentlabs	O
have	O
developed	O
the	O
Pro-ls1s-dmf	O
,	O
a	O
digital	O
motional	B-Device
feedback	I-Device
subwoofer	O
which	O
,	O
according	O
to	O
the	O
company	O
,	O
lowers	O
low	O
frequency	O
distortion	O
by	O
30dB	O
.	O
</s>
