Bill Fitzmaurice wrote:
The cabinet width in and of itself is inconsequential. From a design standpoint it has to be made wider to make the mouth larger for higher sensitivity at the low end of the pass band. But if you go too wide the throat is too large for proper loading of the driver and the rear chamber is too large for reactance annulling. That's why a range of acceptable widths is specified.
I found this: viewtopic.php?f=28&t=23964&hilit=reducer+panel&start=30#p266378
" Just like when you tune a ported box too low, low freq efficiency suffers. That is what the reducer plate in the plans does."
Which makes clear to me that chamber reducers can be used, the size of the driver chamber does matter and does not have to be as wide as the cab.
About temperature influence on drivers: http://adamjhill.com/AJHILL/wp-content/ ... tation.pdf
Through research, simulation and experimentation, it is clear that voice coil temperature
affects the performance of a loudspeaker. The majority of these effects occur due to the direct
relationship between the voice coil temperature and DC resistance. The change in DC
resistance can affect the majority of performance parameters including electrical impedance,
efficiency and axial SPL. The increase in DC resistance also causes certain low frequency
values (around 110 Hz in the tested loudspeaker) to increase in amplitude as temperature
rises. This can be attributed to the changes in the electrical impedance and quality factor
around the nearby resonant frequency (90 Hz in this case).
Aside from the DC resistance relationship, the voice coil temperature also causes the
enclosed air in a loudspeaker to rise in temperature. This will bring a rise in the speed of
sound inside the enclosure, causing the response pattern to shift upwards with temperature.
While the low frequency range is largely unaffected by the voice coil temperature, high
frequencies experience a significant decrease in amplitude. This is likely due to the change in
stiffness of the enclosed air making it harder for the driver to move at high velocities without
The most interesting frequency range affected by voice coil temperature is a mid-range band.
The explanation presented in this paper is that this drop in amplitude is due to the resonant
modes due to the enclosure dimensions. These modes interact to cause significant drops in
this frequency range that become more visible as the voice coil temperature rises.
Tested was a 125W 8 inch driver with a 35W amp and voicecoil temps got 76C / 169F See page 46 for measurements; interesing to see is that the back plate of the driver is hotter then the coil.
Page 50 shows a 1kHz dip when the driver is warm.
According to http://sound.whsites.net/lr-passive.htm#s3.3
voicecoils get even hotter like 150C and all passive crossovers suffer from rising temps to.