horn and WE555W.
Ta4181a 18" 24V field coil woofer.
se7018 network : 16 Ohm 400Hz (?) network
coils of both woofer and driver are supplied by a Motiograph Tungar PSU
differs only in diaphragm. WE555W was manufactured
till 1931 and has a lighter duralumin diaphragm : very good treble response.
WE555 , manufactured after 1931, has a heavier
,rugged aluminum diaphragm : warmer sound.
Mirrophonic style system sounds very clean and
straight . Its frequency response is very flat . Its sound is beautiful but
less exciting and lifelike in respect to the we15a system.
response on trebles is very smooth but it's flat till only 6000Hz. I boost
the 6000-13.000Hz region employing the treble control of a Scott 121 preamplifier.
In this way treble balance and energy is correct , the trebles have a better
dispersion due to multicell pattern and I can avoid to employ a tweeter with
its related network and phase relation . Due to only 2 way system , sound
coherence is reached.
field coil speakers
ERPI ta4181a 18"
coil : 24V , voice coil impedance 12 Ohm .
Electric never manufactured his woofer during 30's , but they were Jensen
made. WE Ta4181a and Ta4194a
were Jensen made under ERPI spec. ( Electrical Research Product Inc ).
and ta4194a were Jensen 18" with field coil magnet at 24V and 10V respectively.
instead usually made for pro and home audio purposes the same 18" speakers
but with High voltage field coils ( from 100 to 300V) and lower voice coil
impedances ( usually 8 Ohm ) . They were Jensen L18
, M18 , V18 and HF18.
M10 has the same magnet of Jensen 18" , but cone is 13.5". M10 has
bakelite spider instead Jensen 18" has cloth spider.
speaker exists in many versions ( M10 , V10 ,
M20 , ERPI TA4151a ). The main differences are
inbuilt or not PSU , field coil impedances. Usually this speaker has 8 Ohm
voice coil. Instead WE ta4151a has 11 Ohm voice coil.
is a widerange speaker , usually employed in console radios or studio monitors.
WE ta4151a was used fullrange or with we597a tweeter added or as bass speaker
on we15a systems.
of M10 is really beautiful , fast , clean , very lifelike. Probably one of
the best cone speakers ever made.
and Erpi 18" and 13,5"
speakers are made in modular way.
housing is always the same and is fitted with various field coils ( high or
low voltage). the basket comes with his own cone , spider and voice coil.
The basket assembly is bolted to the magnet housing with 4 bolts. So when
a cone brokes , was replaced the entire basket cone assembly , just bolting
it : no cut or glue needed.
at left there the 2 style magnets employed on ta4181a. At Right one ta4181a
with ERPI style magnet. Ta4181a were supplied both with ERPI and Jensen pedestal
style magnet housings. Same sound and data.