Knowledge of Speaker Network Parts
1.Electric Parts variety
The basic components of the speaker network circuit are two kinds of a coil and the condenser. However,
resister is used to equalize sensitivity and the effective resistance of speakers, and they are three kinds.
（Effective resistance is equal to AC resistance, about 1.1-1.3 times of DC resistance at speaker.）
2.Property of Network Parts
2-1.Type and the characteristic of the coil
A. Coil with iron core
(1) Coil with iron core forming closed magnet circuit
Because the non-linear B-H curve in iron core forming closed magnet circuit give a sound quality bad
influence, it is unsuitable for a sound use. You had better avoid closed magnet circuit even if it is very
superior iron core material, including the toroidal core or E-I core or U-U core.
(2) Coil with iron core forming opened magnet circuit
The air occupy greater in a magnetic circuit, it becomes nearer to the coil without core, and improved.
Because silicon steel can take permeability highly, size can be miniaturized, but distortion increases
because the B-H curve being bad. The ferrite has not high magnetic permeability, but can be used for
network circuit because the B-H curve is good. Magnetic flux dencity of ferrite have to be lower to reduce
distortion more. Because magnetic flux dencity is low, coil with big core is generally suitable for network
circuit. It is necessary that current capacity is large enough for speaker power calculated by P = RI2.
There is network coil with iron core on sale, but the coil without core is good if they are equivalent.
There is a small coil called the ferrite inductor on sale, but the size of a diameter of 10-16mm can be
used approximately till 1W for low tone, and till 10W high tone.
Therefore, when it may be in trial manufacture and examination use, a cost can be reduced, but it seems
to be difficult to recruit a coil freely because the retail store has little stock.
B. Coil without core
Magnetic saturation can not occur, and it is most suitable for a network circuit. However, there is the fault
to be very large and expensive. It is necessary that current capacity is large enough for speaker power
calculated by P = RI2. It must be selected whether reforming by inductance measuring instrument or
adjusting crossover frequency and the numerical value of the condenser because available numerical
value is limited on sale.
2-2.Type and charactoristic of condencer
The items influencing life are withstand voltage and current capacity. 0.707 time of Vdc is converted into
Vrms, and when Vac reduction calculated with 2/3 of Vdc, AC withstand voltage of the condenser is 0.47
time of the DC withstand voltage. Destruction may occur when supplied voltage more than the withstand
voltage of the condenser. The standard of the current capacity is prescribed in a catalogue, when current
flowed there is fever to be equivalent to (current)2xESR, and temperature rise occurs. As this temperature
rise shortens the life of the condenser, the current capacity is regarded as an average current.
A. Aluminum electrolysis condenser
The usable electrolysis condenser is a type called the bi-polarity (non-polarity) in a network. It is smaller
size and larger capacity than a film type. The stabilization of the characteristic becomes difficult because
change of the capacitance is big for temperature and the frequency. The equivalent circuit of the
condenser is series of CRL, and it is till 1-5kHz where is good faculty of condenser. Series resonance
frequency is about 10k-50kHz. The resonance frequency
is high in small capacity, and low in large capacity.
Aluminum electrolysis condenser is available for only
woofer and had better not use for squawker and tweeter.
The recent electrolysis condenser is improved, and there
is a usable to higher frequency including a low ESR type.
Because characteristic of electrolyte varies with low
temperature in the winter, a series resistance factor
rises, characteristic of condenser worsens. Temperature
was high, and sound quality was good after soldering on
trial, sound quality worsens when temperature falls next
day, please warn that troubled without understanding cause.
There is small type for minute signals and large type for
speaker networks when you purchase a bi-polarity
(non-polarity) aluminum electrolysis condenser. It must
be displayed "for networks", and current capacity need to be big enough. Even a condenser for minute
signals is conveniently usabe in small volume of sound because you can reduce a cost in the temporary
use of the trial manufacturing.
B. Film Condenser
It is the condenser which used films such as polyester or
polypropylene for dielectric. As change of the capacitance
is small, the characteristic becomes stable characteristic.
Good function as condenser is expected in the impedance
characteristic to 100kHz. Therefore, the film condenser is
suitable for the speaker network characteristically, but has
disadvantage that is large size and high cost. Condenser
which is used for network of tweeter should be a film
condenser because capacitance is small, and cost is low.
In the case of squawker, though a price changes by a
network circuit and crossover frequency, you had better
use the film condenser. In the case of woofer, because
capacitance is big, cost of condenser rises. If a budget
remain enough though cost performance is low, you may
use the film condenser. The performance of the high-
frequency property of the capacitor has the difference by the structure. The stratification type is the
best, the inductance cancel type is better next, and roller type is most inferior because of the difference
of constructional. Therefore, if the stratification type is selected for film capacitor of high tone circuit,
the bestperformanceof characteristic can be expected in high tone. Though regarding the electrode
there are two types, a metal foil type and a metallized film type, because the condenser of the big fixed
number is made of the metallized film only, most of condencers used in a speaker network become to
metallized film type. Moreover, though there are chiefly two types of the film material for condenser,
polypropylene and polyester, the polypropylene is excellent in respect of all characteristics. You had
better to use the film condenser made of the polypropylene if you can obtain.
2-3. Characteristic of the resistor
It is necessary to consider permission average power, but there is not a factor influencing sound quality
else. It seems to be suitable for precision if metal film resistance or metal oxide film resistance is adopted.
The permission power of the resistor is designed with average power. Because large cement resistor
or enamel resistor are necessary when it is designed with the greatest power, it becomes high-priced.