| What
differences are there between amplifiers?
There are very big differences between amplifiers and I will
attempt to explain some of the very obvious reasons and the
more detailed reasons later on.
An amplifier does what?
For speakers amplifiers are the engines that make them move
very fast and loudly. The amplifier takes a small electrical
signal from a CD player (or any small signal) and turns it
into a larger electrical signal which is then passed into
the voice coil of the woofer which converts the electrical
signal into a magnetic filed. This magnetic field pushes and
pulls against the magnets in the drive unit causing the woofer
to move. Sound is created.
What do the Power ratings on Amplifiers
mean?
The power ratings on amplifiers can tell you a lot about
an amplifier. Firstly most good amplifier companies will not
have power ratings written on the amplifier, the reason is
they understand what is really important and so will their
customers. Power ratings on amplifiers tell us how many Watts
they are capable of generating. The Watt is a unit of power,
the more Watts an amplifier can generate the more powerful
the output can be. The power ratings that have are on amplifiers
are normally by marketing people, the maximum out put of an
amplifier can be easily calculated as it can not be more than
100% of the amplifiers current draw, normally 70% of the power
draw by the transformer is turned into power and the rest
as heat.
How many watts do I need?
Not a lot and as many as the woofer can handle is the answer.
Watts are very misunderstood when it comes to music and speakers.
The first 1 to 20 watts are the loudest and most important
watts you will have from an amplifier, the next 20 to 100
watts are important for good dynamics and headroom, the next
100 to 400 watts can be used by the very biggest of speakers
with very large coils, the next 400 to 1600 watts are for
the very extreme end of sound but are the least required in
an average listening situation. The problem with lots of watts
is they produce a lot of heat! this heat is the very same
thing that burns speakers out, so with very powerful amplifiers
you risk damaging your speakers. Pay attention to your speakers
power ratings, understand the difference between RMS and Maximum
and you will not damage you speakers.
The reason for more power having less loudness or volume
is sound is logarithmic, so we need 10 times the power to
double the loudness or volume, in other words the more power
you have the less you get back in sound, the law of diminishing
returns applies to watts and loudness.
RMS and Maximum power ratings, what do
these mean?
RMS means Root Mean Square and is the square root of the
mean squared value of x. It gets quite complicated but generally
works out to be a quarter of the Maximum output of the amplifier
is considered to be and what an amplifier can make for a long
safe period of time without damaging itself.
A good example is a top world class sprinter can run at 26
mph, but only for a few seconds because at this top speed
the sprinters muscles run out of energy very quickly. If the
very same sprinter was to run at there RMS speed, lets say
6 mph, they would be able to run for a very long time with
no risk of over heating or burning up.
This is the same principal for power amplifiers, the RMS
figure is more important then the Maximum power level as we
listen to music for minutes or hours and not seconds and milliseconds.
An amplifier at RMS power will be very comfortable and not
be at risk of over heating or burning itself up as it will
have power in reserve,However there is a reason why even at
RMS power an amplifier can be damaged and over heat, I will
explain this further down.
What difference does the Impedance or
Ohms ? of a woofer have on the amplifier?
Ohms, ? Impedance all means the same thing, Resistance, This
has a very big affect on the amplifier indeed, firstly all
amplifiers are designed to run certain loads or Impedances,
the higher the Ohms ? the less resistance there is on the
amplifiers, so the amplifier is safe but can not use its full
RMS power.
On the other side of this coin is if you have a lower ? impedance
than the amplifier can handle, the amplifier will have to
produce twice the power at RMS and twice the heat so even
though the maximum power rating of the amplifier is not being
used, the amplifier will heat up as twice the current is being
used, Even at modest volumes the amplifier can heat up and
break down.
This means that an amplifier designed to run a 4 ? Ohm load
which is driving a 4 ? ohm load can provide enough power to
move the speaker and the amplifiers potential power is being
used in a well balanced manner.
It is also worth while to mention that distortion (THD) figures
are typically much higher into 2 ? Ohms which is not ideal
for sound quality
An example is,
If you had to walk 1 mile by yourself you could do it with
easy am sure, lets call this a 4 Ohm walk.
Now if you had to walk 1 mile again, but this time you have
another person on your back and you have carry them 1 mile,
I am sure you could not do it and this would be a 2 ohm walk,
twice the weight means twice the power is needed,
but the average person is not designed to carry another person
1 mile just as most amplifier are not designed to drive impedances
lower than they can carry. Amplifiers should not be used in
such a manner as this will damaged the amplifier and reduce
the quality of sound.
What is the best amplifier then,
the most powerful one with the lowest impedance drive?
An amplifier needs to have a quality that is more important
than its raw muscle and power rating. Choosing an amplifier
based on its power rating is like choosing a person for there
looks, its a very shallow means of selections and tells you
nothing about its personality. Amplifiers have characters
just like people, valve amplifiers can have high distortion
and some people say its low power output of only 20 Watts
is weak and pointless and others say that valve amplifiers
have a rich warm sound that solid state electronics can not
match, plus 20 Watts from a valve amplifier can sound like
much more.
Solid state amplifiers that use transistors and can sound
cold and bright, but can be very powerful as they are much
more efficient than valve amplifiers. Now we have Class D
amplifiers that can be 80% efficient but only produce sound
from 10Hz to 300Hz, lots of power with no soul. The arguments
go on and on and people will always disagree.
Choose an amplifier that is well made firstly, is simple to
use and is not complex with too many useless features. Choose
one with good specifications and substantial quality, one
with a good power rating to match your speakers and one that
is within your budget is the most important thing.
How much Bass Boost should I use on my amplifier?
You really do not want to use any bass boost on an amplifier
in a vented system but if you have a sealed box and the bass
boost is an acceptable EQ type and will add more power below
the Fs of the woofer where the sound rolls off then a very
little amount can be used but less is more is the rule. Normal
amplifiers bass boost just hump the bass at 50Hz which is
really poor, which makes you feel you have more bass but you
don't, it just exaggerates one note from your woofer. You
want the most linear bass from a subwoofer with a mild increase
below the roll of point for this we recommend a linkwitz filter.
In general we do not recommend bass boost as they product
more heat and ruin the original signal, if you have a truly
powerful amplifier you will not need the bass boost and it
should not have a bass boost to start with.
The amplifiers we recommend and why
Making the best performance and highest
quality plate & module amplifiers for home and studio
use we recommend B.K Electronics.
These are UK designed and made amplifiers which are used in
many applications by professional across the world.
Rated at true RMS at 1Kh into a dummy load these are electronic
power stations with longevity and sonic stability.
Perfect for high power applications and wonderful amplification
for a Shadow Works infrawoofer.
The amplifiers below are quality hand made Italian
ones, with impressive construction and regulated power supplies
these are very refined and powerful car audio amplifiers.
We recommend PHD amplifiers as the are probably the best
car amplifiers in the UK.
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