SPEAKER TONE CENTER
ton Y PaSko
Your Tone Formula
Let’s jump right in and continue with Part
II of our discussion that began with “Your
Signature Distortion” (September 2009). Part
I covered the DNA of a speaker and how
the materials used factor into your tone. This
month we’re diving in deeper to breakdown
how a speaker distorts. We’ll also answer the
question, “Is the speaker producing what the
amp can deliver?”
are designed to stay clean, so they spec out
at 100 watts with a sensitivity rating of 99dB,
a voice coil inductance of 1 kHz, ceramic
magnet and a resonance frequency of 104Hz.
There are a number of ways to achieve the
distorted tone you’re looking for. If you
have a tube amplifier, you can get distortion from clipping your preamp and power
amp tubes, not to mention the fact that
you can clip your input stage, thus adding
a bit of gain and compression right from
the input of your amplifier. Of course, you
also have a plethora of distortion pedals on
the market to give you an infinite variety
of distortion. But the funny thing is that all
of these distortion makers fall to the mercy
of the speakers. Why? Because it’s the way
the speakers interpret this signal that will
determine your ultimate tone.
The way typical guitar amplifier circuits, such
as Marshalls and Fenders, are designed also
affects how the speakers will respond. The
most obvious difference is that the Marshall
circuits let more signal pass through, and the
tone controls offer less frequency range. The
higher signal means that the preamp tube
stage can overdrive the output tube stage
more. Additionally, the Marshall circuits have
a slight dip in the midrange section, almost
an octave higher than Fender amps, metering in around 700Hz. A Fender’s midrange
dip is around 400Hz, while the bass response
on both amplifiers meter in around 10Hz.
Fender’s tone controls allow for a higher
midrange frequency to pass with the treble
response, meaning more dynamic range for
that sparkling, tight sound they’re famous for.
How does a speaker distort?
When a speaker distorts, it produces two
types of frequencies. The first type is
harmonic distortion: this is heard as additional
tones which are multiples of the original
note played. For example, if the original
sound produces 100Hz, you would also
get 200Hz, 400Hz and so on, even though
these tones are not part of the original
sound. The second type is non-harmonic
distortion, also known as odd harmonic distortion, and often referred to as a buzz or a
rattle in the sound. For example, if the original sound produces 100Hz, the odd harmonic distortion would produce frequencies
of 300Hz, 500 Hz, and 700Hz, etc.
The way typical
guitar amplifier
circuits, such as
Marshalls and
Fenders, are
designed also
affects how the
speakers will
respond.
How does this translate to your guitar tone?
It’s these specs that are directly responsible
for your tone, and it’s here where the “
disconnect” usually happens for most musicians.
We’re not trained to translate these features
into the sounds we hear, but it’s this knowledge that can serve as a guideline for you
to build your own “tone formula.” Here is
an example of a classic one: 50-watt tube
Marshall running through two 25-watt speakers ( 100 watts with four 25-watt speakers will
produce similar results). The Marshall circuit
allows more signal to pass through, meaning
that the guitar input section, the preamp and
power section are going to distort. The lower
wattage speakers with the smaller magnet
and voice coil are going to break up faster
at a lower volume. The voice coil will clip
and compress, giving you that “sizzle” in the
upper frequency range.
This is the classic Marshall tone, but here’s
the rub: the lower-wattage speaker distorts
so fast that the speaker will not be able
to produce the lower frequencies (bass
response) that the amp can put out, thus giving you the illusion that the amp has no bottom end. By adding a 30-watt speaker, you
can increase the bass response but cut the
level of distortion. Now, if you went to the
other end of the spectrum and had a Fender
amp that was too clean and brittle sounding,
you could add a lower wattage speaker with
a smaller magnet and voice coil and achieve
some nice, mild distorted tones. Changing
the magnet to alnico would also add a bump
to the midrange section.
When setting your tone, there are a series of
specs you need to consider, starting with your
guitar and amplifier. The signal from a guitar
pickup is mostly all midrange and is not rich
in harmonics, with practically nothing coming
through above 4000Hz. The sixth string “E”
tuned to pitch comes through at about 80Hz,
two full octaves above the 20Hz low frequency our ears can pick-up. The standard 4-string
bass has a range one octave below the guitar,
with the low E at about 40Hz.
To save time, I’ll spec out the three most
popular speakers associated with Fenders
and Marshalls, starting with a 25-watt, 12"
speaker with a sensitivity rating of 98dB,
1. 75" copper voice coil, ceramic magnet
and a resonance frequency of 75Hz. Another
popular choice is a 30-watt, 12" speaker with
a sensitivity rating of 100dB, 1. 75" copper
voice coil, ceramic magnet and a resonance
frequency of 85Hz. The speakers in Fenders
Next up in Part III: the “secret weapon” in
your tone formula. Stay tuned!
Tony Pasko
For more than 15 years Tony has been a music industry
professional, conducting clinics and in-store training seminars world-wide for Peavey, Washburn, Eden Amps and
Parker Guitars, as well as involvement in product development. He’s also an experienced performing musician.
