Hi,
although it is not strictly linked to fullrange, I would still like to ask here: it is clear that the lower the resistance of the speaker, the more demanding it is to drive.
Many therefore even buy 16 ohm loudspeakers. Most (all) loudspeakers show a wavy impedance curve - how far should the impedance be smoothed with the xo?
It's often emphasized that the impedance doesn't go below 6-7-whatever ohms. But what is the upper limit?
Thanks for your opinions in advance.
although it is not strictly linked to fullrange, I would still like to ask here: it is clear that the lower the resistance of the speaker, the more demanding it is to drive.
Many therefore even buy 16 ohm loudspeakers. Most (all) loudspeakers show a wavy impedance curve - how far should the impedance be smoothed with the xo?
It's often emphasized that the impedance doesn't go below 6-7-whatever ohms. But what is the upper limit?
Thanks for your opinions in advance.
While impedance does get high, the response is right all the same. For example, at resonance the response is boosted mechanically so it needs less power. This is reflected as a higher impedance. The amplifier provides the same drive Voltage and the driver draws less current.
Also, minimum impedance value, typically found around 250 to 400Hz, is not much a problem for output transistors, any reasonable design allows for, say, 20-30% extra current capability (at least)
Much more stressing (for the output transistors) is driving the speaker at resonance, where it´s highly reactive.
Transistors are subject to simultaneous high voltage and high current, SOAR limits are easily reached and even surpassed.
To boot, a heavy cone, heavy/large voice coil and big magnet speaker at that frequency can and does produce high EMF peaks at the worst possible moments, reverse biased clamping diodes from speaker out to +/-V rails are also mandatory .
Not that big a problem in a regular Hi Fi amplifier, playing a "normal" music program, but I make Bass Guitar amplifiers, which often have such speakers, and are constantly over-driven for hours on stage and specifically at such Bass frequencies (hey, it´s what the guy is playing) so that´s an extra consideration.
Big heavy underdamped speakers in a terrible design cabinet (that describes 80% of those out there) are a very difficult load.
Much more stressing (for the output transistors) is driving the speaker at resonance, where it´s highly reactive.
Transistors are subject to simultaneous high voltage and high current, SOAR limits are easily reached and even surpassed.
To boot, a heavy cone, heavy/large voice coil and big magnet speaker at that frequency can and does produce high EMF peaks at the worst possible moments, reverse biased clamping diodes from speaker out to +/-V rails are also mandatory .
Not that big a problem in a regular Hi Fi amplifier, playing a "normal" music program, but I make Bass Guitar amplifiers, which often have such speakers, and are constantly over-driven for hours on stage and specifically at such Bass frequencies (hey, it´s what the guy is playing) so that´s an extra consideration.
Big heavy underdamped speakers in a terrible design cabinet (that describes 80% of those out there) are a very difficult load.