Let’s Get Physical
COSM is actually an amalgamation of many
different digital modeling technologies developed by BOSS and Roland.
These were created to precisely model the electronic, mechanical, and
magnetic characteristics inherent to an instrument, amplifier, or
speaker, and also to create completely new sounds. In concept, the COSM
process is not unlike the amazing computer-generated imagery (CGI) we
all see in today’s high-tech films, where complex software is used to
digitally construct people and animals from the inside out, from
skeleton to muscles to skin.
COSM models all aspects of an amp’s circuitry—every component, every path.
Variable
Guitar Modeling, or VGM, is the main component of COSM when it comes to
guitars and basses. It can be broken down into three separate elements:
- Electronic modeling—With
this process, BOSS and Roland engineers analyze and simulate the actual
electronic circuitry and how it interacts in a device such as a vintage
guitar amp or a classic stompbox. This includes the detailed behavioral
characteristics of vacuum tubes, transistors, and all other electronic
components.
- Magnetic modeling—Electromagnetic components
are a huge part of the sound of electric guitars and amps; this VGM
process simulates the characteristics of guitar pickups, amp
transformers, speakers, and more.
- Physical modeling—This
process is a central part of COSM instrument modeling. It simulates the
characteristics of the materials used to construct an instrument,
including the type of wood, the metal parts, and even the finish.
Physical modeling is also used to analyze the construction materials
used in different guitar speaker cabinets.
Measuring sound in an anechoic chamber.
Harmonic
Restructure Modeling (HRM) is another component found in some COSM
guitar products. The vibration of a guitar string generates many
harmonics, and these harmonics define the actual sound character of
guitar sounds as we recognize them. With HRM, BOSS and Roland engineers
manipulate these harmonics and change them to create very un-guitar-like
tones, while still retaining feel and playability of the guitar. In a
Roland V-Guitar System, for example, HRM applies the harmonic
characteristics of organs, reed instruments, and synths directly to your
actual guitar.
When all the VRM and/or HRM elements are brought
together, the result is a realistic composite of the individual
components of the object whose sound is being modeled. That’s a real
mouthful, so COSM’s extended name describes this process much more
elegantly: Composite Object Sound Modeling. Get it?
Realtime, All the Time
COSM
accomplishes all its modeling magic in real time using super-fast
digital signal processing to alter the guitar’s sound as you play. Your
guitar’s string signals are the fundamental building blocks of the sound
you hear, even when the real-time modeling process modifies that sound
into something quite unlike a guitar. As such, COSM retains the natural
feel and responsiveness of your guitar playing, with every subtle,
expressive nuance coming through.
source:
http://www.bossus.com/boss_users_group/article.php?ArticleId=1319
