A very controversial yet very interesting piece to read..
it deals with an explanation to some POWER AND CONE AREA MYTHS rampant in the car audio world..
http://www.installer.com/tech/conearea.html
comments...??
Victor...
Replies (1)
swez on 11/14/2004 10:39:35
His points make sense and good applied logic as well. However, the myth is closer to truth than not, in many cases. To prove or dispute these claims, we need some tools and a little math to determine validity.
1. Tone generator (audio source)
2. SPL meter with calibrated mike
3. VOM (to measure volts and nominal DC resistance)
4. Amplifer & speaker(s)
Clio or LEAP plots are very helpful as well. They show us the effects of changing impedence values, as frequency changes. In most cases, we are talking low power readings to get an accurate SPL and phase angle set of plots.
However, at high SPL levels, a new variable come into play. THERMAL COMPRESSION ! Meaning... as the voice coil heats up with more power applied, the resistance will go up as well. Whenever we heat a metal coil, the resistance will go up at a predictable rate. We just have to know the thermal properties of the wire used. Copper or aluminum are most common wires used in speakers. Also, some coils are vented better for better thermal management at high SPL levels.
The size of the coil, gage of wire used and bobbin materials used and venting system used, all help cool the coil at high SPL levels. The larger the voice coil diameter, the more heat it can safely dissapate. That why we see 3-4 inch coils on large cone speakers with high power ratings.
In short, there are "many variables" that must be taken into account, when building a quality speaker. Thiel & Small have made a tremendous impact on measuring these complex variables. Here's a basic list of T/S parameters.
Thiel-Small Parameters:
FS - Natural resonant frequency of the woofer
Cas - Acoustic compliance
Vas - Volume of air having the same compliance as the woofer suspension.
Qms - Mechanical Q
Qes - Electrical Q
Qts - total Q Qts=1/(1/Qes)+(1/Qms)
Vab - Air volume of box
Cab - Acoustic compliance of the air in the box
Fb - Resonant frequency of a vented box
Qb - Q of a vented box
Qtc - system Q of a sealed box
RE - Voice coil resistance
VB - volume of enclosure
VP - Peak Displacement
FB - resonant frequency of vented box
F3 - the 3dB down point
Source used for T/S parameters: http://www.installer.com/tech/speakers.html
Swez
it deals with an explanation to some POWER AND CONE AREA MYTHS rampant in the car audio world..
http://www.installer.com/tech/conearea.html
comments...??
Victor...
Replies (1)
swez on 11/14/2004 10:39:35
His points make sense and good applied logic as well. However, the myth is closer to truth than not, in many cases. To prove or dispute these claims, we need some tools and a little math to determine validity.
1. Tone generator (audio source)
2. SPL meter with calibrated mike
3. VOM (to measure volts and nominal DC resistance)
4. Amplifer & speaker(s)
Clio or LEAP plots are very helpful as well. They show us the effects of changing impedence values, as frequency changes. In most cases, we are talking low power readings to get an accurate SPL and phase angle set of plots.
However, at high SPL levels, a new variable come into play. THERMAL COMPRESSION ! Meaning... as the voice coil heats up with more power applied, the resistance will go up as well. Whenever we heat a metal coil, the resistance will go up at a predictable rate. We just have to know the thermal properties of the wire used. Copper or aluminum are most common wires used in speakers. Also, some coils are vented better for better thermal management at high SPL levels.
The size of the coil, gage of wire used and bobbin materials used and venting system used, all help cool the coil at high SPL levels. The larger the voice coil diameter, the more heat it can safely dissapate. That why we see 3-4 inch coils on large cone speakers with high power ratings.
In short, there are "many variables" that must be taken into account, when building a quality speaker. Thiel & Small have made a tremendous impact on measuring these complex variables. Here's a basic list of T/S parameters.
Thiel-Small Parameters:
FS - Natural resonant frequency of the woofer
Cas - Acoustic compliance
Vas - Volume of air having the same compliance as the woofer suspension.
Qms - Mechanical Q
Qes - Electrical Q
Qts - total Q Qts=1/(1/Qes)+(1/Qms)
Vab - Air volume of box
Cab - Acoustic compliance of the air in the box
Fb - Resonant frequency of a vented box
Qb - Q of a vented box
Qtc - system Q of a sealed box
RE - Voice coil resistance
VB - volume of enclosure
VP - Peak Displacement
FB - resonant frequency of vented box
F3 - the 3dB down point
Source used for T/S parameters: http://www.installer.com/tech/speakers.html
Swez
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