Kreshna
...but I have to know.
Since the first time I read about full-range single driver loudspeakers --Fostex, Lowther, Audio Nirvana, and the likes-- I always wonder why single driver loudspeaker owners are mostly use SET amp or T-amp. Why do they never use traditional solid-state amp, for instance? Why does nobody drive Fostexes or Lowthers using traditional Sansui or Marantz solid-states?
1. Do full-range single driver loudspeakers only sound good with the purest, zero-feedback signal?
This is my first guess. SET amplifier is said to have the best signal purity, since it involves zero feedback. So it seems to me full-range single-driver loudspeaker sounds best with such pure signal, and will sound bad otherwise. And probably that's the reason people drive Fostexes and Lowthers using SET amp instead of traditional Marantz solid state amp.
But single driver owners also love to drive their speakers using T-amp; Tripath amp, which is class-D amp. And a friend of mine said all class-D amp, including Tripath amp, cannot function without feedback. So it seems T-amp does not sound as pure as SET amp.
So perhaps it's not about signal purity?
2. Do full-range single driver loudspeakers only sound good with warm, tube sound?
Since I never read about someone driving their Lowthers or Fostexes using Krell, McIntosh, or Bryston solid states, then probably full-range single driver loudspeakers only sound good with warm, tube sound.
However, people also drive their full-range single driver using T-amp, which is not tube amp. On the other hand, I've never read about someone driving their full-range single driver loudspeakers using push-pull tube amps either --only SET tube amps.
So perhaps it's not about warm, tube sound?
3. Do full-range single driver loudspeakers only sound good with low damping factor?
This is my last guess. As Nelson pass has wrote on his article (PDF here), due to their high sensitivity, full-range single driver loudspeakers only sound good with low damping factor. An amplifier with high damping factor will cause the highly sensitive full-range single driver to suffer from overdamping, which in turn causes significant loss in low frequency, making the said speakers sound shrill and strident.
Apparently, both SET amps and Tripath amps have such low damping factor, that they do not cause overdamping on full-range single driver speakers.
Am I correct so far? Please correct me if I'm wrong.
4. What is current source amplifier? What is voltage source amplifier?
On his article I mentioned above, Nelson Pass use the terms 'current source amplifier' and 'voltage source amplifier' repeatedly. I have the impression that current source amplifier is an amplifier with low enough current and/or low enough damping factor; examples are SET amp and T-amp. On the other hand, voltage source amplifier is an amplifier with high enough current and/or high enough damping factor; examples are traditional amplifier like QSC or Bryston. A voltage source amplifier is good to control thick cone woofers with heavy materials, because it has strong current and high damping factor to 'grip' the woofer cone properly. However, it will kill the bass on Fostexes or Lowthers due to overdamping.
Am I correct so far?
5. Using resistor in serial with full-range single driver to drive them using traditional amps?
On his article, Nelson Pass suggested to put a resistor in serial with full-range single driver loudspeakers, in order to get good sound when driving them with 'traditional' amplifier (voltage source amplifier). As Pass has said:
"Most of the examples we will examine do not require true current source amplifiers, only amplifiers of quite high output impedances. Most of these cases will be happy with an output impedance of approximately 47 ohms or so and prefer 47 ohms loaded in parallel with the output of a current source. That being the case, you can build a Thevenin Equivalent of such a current source by placing a large resistor (here later referred to as R0) in series with the output of a high wattage voltage source amplifier and get similar results.
I’m not saying it will equal a spiffy First Watt F1 (being Class A and no feedback and all), and your resistor will run hot. On the other hand, you probably already have such a voltage- source amplifier and some of these speakers are quite cheap, allowing you a taste of these forbidden pleasures without high expense."
In fact, Nelson Pass has run simulations and created the appropriate table to suggest the resistor to be used. For example, the resistor to be used with Fostex FE206E is 47 ohm.
So, has anybody tried the solution? Has anybody ever tried traditional solid-state amps, like Sansui and Marants, to drive their single driver loudspeakers, using resistor like Nelson Pass has suggested?
6. Full-range single-driver loudspeakers for home theaters?
One may ask; why do I bother asking all these questions? Well, because Fostex FE206EN in double bass-reflex enclosure really stirs my interest. The double bass-reflex enclosure seems to be easier to make than the back-loaded horn solution, and it might be great for home theater. Single-driver loudspeakers seem to have very excellent stereo imaging and sound stage depth, so with a subwoofer or two, they could make really impressive speakers for home theater. In fact, Bose Accoustimass speaker set has such great imaging because each satellite speaker is point-source loudspeaker (single driver).
However, acquiring 5-channel SET amp for such home theater purpose could be difficult.
So which one is better? Building a sufficiently powerful 5-channel Tripath amp to drive five full-range single driver loudspeakers for home theater? Or drive them using traditional 5-channel amplifier like ATI or Emotiva with Nelson Pass' resistor solution?
How about using this amplifier with full-range single driver? It seems it needs Nelson Pass' resistor, because it isn't SET amp. However, the tube input stage is interesting.
1. Do full-range single driver loudspeakers only sound good with the purest, zero-feedback signal?
This is my first guess. SET amplifier is said to have the best signal purity, since it involves zero feedback. So it seems to me full-range single-driver loudspeaker sounds best with such pure signal, and will sound bad otherwise. And probably that's the reason people drive Fostexes and Lowthers using SET amp instead of traditional Marantz solid state amp.
But single driver owners also love to drive their speakers using T-amp; Tripath amp, which is class-D amp. And a friend of mine said all class-D amp, including Tripath amp, cannot function without feedback. So it seems T-amp does not sound as pure as SET amp.
So perhaps it's not about signal purity?
2. Do full-range single driver loudspeakers only sound good with warm, tube sound?
Since I never read about someone driving their Lowthers or Fostexes using Krell, McIntosh, or Bryston solid states, then probably full-range single driver loudspeakers only sound good with warm, tube sound.
However, people also drive their full-range single driver using T-amp, which is not tube amp. On the other hand, I've never read about someone driving their full-range single driver loudspeakers using push-pull tube amps either --only SET tube amps.
So perhaps it's not about warm, tube sound?
3. Do full-range single driver loudspeakers only sound good with low damping factor?
This is my last guess. As Nelson pass has wrote on his article (PDF here), due to their high sensitivity, full-range single driver loudspeakers only sound good with low damping factor. An amplifier with high damping factor will cause the highly sensitive full-range single driver to suffer from overdamping, which in turn causes significant loss in low frequency, making the said speakers sound shrill and strident.
Apparently, both SET amps and Tripath amps have such low damping factor, that they do not cause overdamping on full-range single driver speakers.
Am I correct so far? Please correct me if I'm wrong.
4. What is current source amplifier? What is voltage source amplifier?
On his article I mentioned above, Nelson Pass use the terms 'current source amplifier' and 'voltage source amplifier' repeatedly. I have the impression that current source amplifier is an amplifier with low enough current and/or low enough damping factor; examples are SET amp and T-amp. On the other hand, voltage source amplifier is an amplifier with high enough current and/or high enough damping factor; examples are traditional amplifier like QSC or Bryston. A voltage source amplifier is good to control thick cone woofers with heavy materials, because it has strong current and high damping factor to 'grip' the woofer cone properly. However, it will kill the bass on Fostexes or Lowthers due to overdamping.
Am I correct so far?
5. Using resistor in serial with full-range single driver to drive them using traditional amps?
On his article, Nelson Pass suggested to put a resistor in serial with full-range single driver loudspeakers, in order to get good sound when driving them with 'traditional' amplifier (voltage source amplifier). As Pass has said:
"Most of the examples we will examine do not require true current source amplifiers, only amplifiers of quite high output impedances. Most of these cases will be happy with an output impedance of approximately 47 ohms or so and prefer 47 ohms loaded in parallel with the output of a current source. That being the case, you can build a Thevenin Equivalent of such a current source by placing a large resistor (here later referred to as R0) in series with the output of a high wattage voltage source amplifier and get similar results.
I’m not saying it will equal a spiffy First Watt F1 (being Class A and no feedback and all), and your resistor will run hot. On the other hand, you probably already have such a voltage- source amplifier and some of these speakers are quite cheap, allowing you a taste of these forbidden pleasures without high expense."
In fact, Nelson Pass has run simulations and created the appropriate table to suggest the resistor to be used. For example, the resistor to be used with Fostex FE206E is 47 ohm.
So, has anybody tried the solution? Has anybody ever tried traditional solid-state amps, like Sansui and Marants, to drive their single driver loudspeakers, using resistor like Nelson Pass has suggested?
6. Full-range single-driver loudspeakers for home theaters?
One may ask; why do I bother asking all these questions? Well, because Fostex FE206EN in double bass-reflex enclosure really stirs my interest. The double bass-reflex enclosure seems to be easier to make than the back-loaded horn solution, and it might be great for home theater. Single-driver loudspeakers seem to have very excellent stereo imaging and sound stage depth, so with a subwoofer or two, they could make really impressive speakers for home theater. In fact, Bose Accoustimass speaker set has such great imaging because each satellite speaker is point-source loudspeaker (single driver).
However, acquiring 5-channel SET amp for such home theater purpose could be difficult.
So which one is better? Building a sufficiently powerful 5-channel Tripath amp to drive five full-range single driver loudspeakers for home theater? Or drive them using traditional 5-channel amplifier like ATI or Emotiva with Nelson Pass' resistor solution?
How about using this amplifier with full-range single driver? It seems it needs Nelson Pass' resistor, because it isn't SET amp. However, the tube input stage is interesting.