Philco 511 "Coffin" Radio & Model 211 Speaker (1928)
This is the "Spanish Brown" Philco model 511 together with its matching model 211 loudspeaker. It was one in the 1928
line-up of Philco's very first radios. The less common models 512 through 514 were painted Mandarin Red, Labrador
Grey and Nile Green respectively and each was adorned with hand-painted flowers. The even rarer model 515 was
painted in an impressionistic style. Each of these models too could be purchased with a matching loudspeaker (models
212 through 215).
According to early Philco advertising, the cabinets for these models were designed by Hollingsworth Pearce, billed as a
leading authority on cabinet design, with the color effects created by Mlle Messaros and applied by hand under her
direction. The model 511 had an original purchase price, minus tubes, of $115. With speaker and tubes the price
increased to around $160. The patent for the set's escutcheon, filed in March of 1928, can be viewed here.
The model 511 is an ac "socket-powered" radio that covers the standard broadcast band from 550 - 1500kc. It uses 7
tubes:- 80 (rectifier), 71A (power amp), 26 (first af), 27 (detector), 26*3 (3 tuned RF stages). A bottom view of the set,
with the metal cover removed, can be seen here and the schematic is available online courtesy of NostalgiaAir.
The radio's use of triodes for RF amplification demanded that each stage be neutralized to compensate for the inherent
plate-grid capacitance of these devices. This capacitance, in accordance with the so-called Miller Effect, becomes
magnified by the gain of the stage and without compensation renders the circuit practically useless as an RF amplifier.
Cognizant of this, Philco contracted with the Hazeltine Corporation for rights to use their neutrodyne circuit, which had
been invented by Louis Alan Hazeltine in 1922. In their advertisements of the time, Philco referred to their radio as being
"Neutrodyne Plus - a combination of the neutrodyne circuit PLUS super power". Their promotional literature referred to it
as a "New Radio Discovery". The exact meaning of the word PLUS has however become somewhat of a subject for
debate in recent years.
I bought this in unrestored condition from a dealer but have since restored it. All it needed was a basic recap, lubrication
and cleaning. It was missing the matching model 211 speaker, but I found one later in a Maine antiques store. The
speaker is often found with an open driver coil, but this one turned out to be fine. It's a high impedance speaker
designed to match the plate circuit of the 71 output stage, to which it is capacitively coupled. The radio would not work if
connected directly to a modern permanent magnet speaker.
line-up of Philco's very first radios. The less common models 512 through 514 were painted Mandarin Red, Labrador
Grey and Nile Green respectively and each was adorned with hand-painted flowers. The even rarer model 515 was
painted in an impressionistic style. Each of these models too could be purchased with a matching loudspeaker (models
212 through 215).
According to early Philco advertising, the cabinets for these models were designed by Hollingsworth Pearce, billed as a
leading authority on cabinet design, with the color effects created by Mlle Messaros and applied by hand under her
direction. The model 511 had an original purchase price, minus tubes, of $115. With speaker and tubes the price
increased to around $160. The patent for the set's escutcheon, filed in March of 1928, can be viewed here.
The model 511 is an ac "socket-powered" radio that covers the standard broadcast band from 550 - 1500kc. It uses 7
tubes:- 80 (rectifier), 71A (power amp), 26 (first af), 27 (detector), 26*3 (3 tuned RF stages). A bottom view of the set,
with the metal cover removed, can be seen here and the schematic is available online courtesy of NostalgiaAir.
The radio's use of triodes for RF amplification demanded that each stage be neutralized to compensate for the inherent
plate-grid capacitance of these devices. This capacitance, in accordance with the so-called Miller Effect, becomes
magnified by the gain of the stage and without compensation renders the circuit practically useless as an RF amplifier.
Cognizant of this, Philco contracted with the Hazeltine Corporation for rights to use their neutrodyne circuit, which had
been invented by Louis Alan Hazeltine in 1922. In their advertisements of the time, Philco referred to their radio as being
"Neutrodyne Plus - a combination of the neutrodyne circuit PLUS super power". Their promotional literature referred to it
as a "New Radio Discovery". The exact meaning of the word PLUS has however become somewhat of a subject for
debate in recent years.
I bought this in unrestored condition from a dealer but have since restored it. All it needed was a basic recap, lubrication
and cleaning. It was missing the matching model 211 speaker, but I found one later in a Maine antiques store. The
speaker is often found with an open driver coil, but this one turned out to be fine. It's a high impedance speaker
designed to match the plate circuit of the 71 output stage, to which it is capacitively coupled. The radio would not work if
connected directly to a modern permanent magnet speaker.
Philco 511 neutrodyne plus...vast distance range, split-hair selectivity and tremendous volume.
"...the cabinet stands forth as a
highly artistic ornament on its
own account, exquisite in its
classic line, softly modulated in
color"
highly artistic ornament on its
own account, exquisite in its
classic line, softly modulated in
color"
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