Car
Stereo &
Electronics
Amplifiers
Subwoofers
Full-Range Speakers
Midrange Speakers
Tweeters
Power Capacitors
Empty Enclosures
Loaded Enclosures
CD/Mp3 Receivers
CD Changers
Bass Packages
Car TV/Video
Satellite Radio
Bluetooth Wireless
GPS Navigation
Neon/LED Lighting
Radar Detectors
Chrome Mufflers
Car Alarms/Security
AUTO PARTS STORE
Auto
Wiring &
Accessories
Air Horns
Power Antennas
Antenna Boosters
A/V Controllers
Bass Blockers
Crossovers
Dynamat
Equalizers
Fans (Cooling)
FM Modulators
Interfaces
Line Converters
Noise Filters
Power Inverters
Power Supplies
RCA Cables
RCA Splitters
Remote Controls
Signal Boosters
Vibration Control
Speaker Grills
Wiring Kits
Marine
Stereo &
Electronics
Stereo Amplifiers
Stereo Speakers
Stereo Woofers
Woofer Tubes
Enclosed Speakers
Wakeboard
Speakers
CD/Mp3 Receivers
TVS & Video
VHF
Radios
GPS Navigation
Fish Finders
Depth
Finders
Chart Plotters
Accessories
Home
Stereo &
Electronics
Flat
Screen & HD TVs
Surround Sound
Home Theater
DVD Players/Tivo
DVD Recorders
Blu-Ray Devices
Amplifiers/Tuners
Speaker Systems
Subwoofer Drivers
Midrange Drivers
Tweeter Drivers
Powered Subwoofers
Outdoor Speakers
Stereo Accessories
Digital Photo Frames
Video Game Systems
Game
Accessories
Video Games
Home Security/Alarms
Computers
&
Related Products
Desktops & Laptops
Add-Ons/Peripherals
Computer Monitors
Computer Software
Computer Games
Printers &
Scanners
Ink/Specialty Papers
Parts & Components
Computer Supplies
Security/Tech
Support
Personal
Stereo
& Electronics
Laptop Computers
Cell Phones & PDAs
Portable TV & Video
Electronic Readers
MP3/Music Players
CD
Players/Booms
Earphones/Buds
Digital Cameras
Video Cameras
Personal GPS
Bluetooth
Calculators
Accessories
Technical
Help
& Education
Glossary Of Terms
Speakers Main Page
How Speakers Work
Choosing Speakers
What's A Woofer?
What's A Midrange?
What's A Tweeter?
Other Speaker Types
More Speaker Types
What's A Capacitor?
Installing A Capacitor
What's A Crossover?
What's An Equalizer?
Speaker Enclosures
Theile/Small Param.
About Power Amps
Installing An Amp
Installation Tips
Power Ratings
Installing/Replacing
Head Units/Receivers
Installing Neon/LED
Eliminating Noise
Use The Right Tools
Manufacturer's Links
Home
Stereo
Tech Information
FAQ
Glossary
Home
Speakers
Understanding
Theile/Small Parameters
(NOTE:
For terms you do not understand,
please refer to our Glossary)
This mathematical description of loudspeaker behavior applies to any sound transducer, but finds it's most common application with enclosure design for woofers/subwoofers.
For most audiophiles, a standard enclosure that meets the VAS requirement for the their driver will usually perform quite adequately. See bold section below.
The three Theile/Small parameters that primarily determine the frequency response of a loudspeaker are:
Compliance or Vas
Free-air resonance or Fs
Response time or Qts
Compliance or Vas is a measure of the overall stiffness, or resistance to motion of the cone, the surround, and the spider. It is specified in term of the volume of air having the same compliance as the driver. A small number corresponds to a small volume of air, which is stiffer than a larger volume of air. Thus, compliance and stiffness are inversely proportional.
Optimum enclosure volume is proportional to Vas. It is usually measured in cubic feet, and generally is equivalent to the internal volume of the enclosure. This is the principle specification for the speaker cabinet
Free-air resonance or Fs is the resonant frequency of the driver's voice coil impedance with the driver suspended in free air (no enclosure). The -3 dB frequency (F3) of an enclosure is proportional to Fs.
Response time or Qts is a measure of the sharpness of the driver's free-air resonance. It is defined as (Fh-Fl)/Fs, where Fh and Fl are the upper and lower -3 dB points of the driver's voice coil impedance in free air. Optimum enclosure volume is related to Qts but is not directly proportional. It is accurate to say that the volume gets larger as Qts gets larger. Likewise, F3 gets smaller as Qts gets larger, and for the sealed box enclosure, F3 is inversely proportional to Qts.
Theile/Small
Parameters And Speaker Design
Research done in the study of loudspeakers has
been conducted by a number of acousticians. The work of Neville Theile
and Richard Small is considered to have the most impact on the loudspeaker
design field. They discovered a method that could predict the frequency
response performance, and other characteristics of a loudspeaker system,
based on its physical properties.
The reference nomenclatures for the Physical Characteristics of a speaker are:
Re: The static D.C. resistance of the voice coil measured in Ohms.
Sd: The surface area of the speaker's cone.
BL: The magnetic strength of the motor structure.
Mms: The total moving mass of the speaker including the small amount of air in front of and behind the cone.
Cms: The stiffness of the driver's suspension.
Rms: The losses due to the suspension.
~ * ~
The Theile/Small Response Parameters
By understanding the relationship of these 20 physical parameters and how to change them, we may alter the response of the system to fit the desired goal.
The most frequently cited measures in design are:
Re: The D.C. resistance of the voice coil measured in Ohms.
Sd: The surface area of the speaker.
Fs: The resonant frequency of the speaker.
Q: The ratio of resistance to reactance, or vice versa.
Qes: The electrical "Q" of the speaker.
Qms: The mechanical "Q" of the speaker.
Qts: The total "Q" of the speaker.
Vas: The volume of air having the same acoustic compliance as the speaker's suspension.
Xmax: The width of the voice coil that extends beyond the front plate plus 15%. This relates to how far the speaker can move in either direction without appreciable distortion. The amount of power required to move a speaker to its maximum excursion is referred to as the displacement limited power handling. Please note that this number varies with enclosure size and type.
Understanding the response parameters allows us to calculate the predicted frequency response of a given speaker system. The formulas that accomplish this are rather lengthy and complex, and are best left to a computer. There are a number of high quality computer programs on the market that automate the design process of building an enclosure. We have located a free example on line.
What's New -- What's Hot -- On Sale -- Our Philosophy -- Testimonials
© Copyright 2000 - 2009 ElectronixWarehouse - All Rights Reserved - Website Designed And Maintained By MetroDirect Communication
