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#41
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SS subwoofer amplifier with high-ish output impedance?
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#43
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SS subwoofer amplifier with high-ish output impedance?
(unitron) wrote in message . com...
(dangling entity) wrote in message . com... Is there some practical way to do this by doing something funky in the feedback loop or something? Would there be considerable downsides wrt the operation of the amplifier itself? Excessive thermal dissipation in the amplifier output stages, for instance? Do SS amplifiers like this already exist (for one reason or another), or would this be relatively virgin territory? Are you looking for something to drive a novel design of low audio (or sub-audio) frequency electrical current to air pressure transducer, perhaps novel enough that conventional terms such as speaker and subwoofer are inadequate? If it's something you may seek a patent for, and therefore wish to withhold details, can you at least reveal input impedence and power requirements? Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? Fiddling with the series resistance affects the drivers Qts value (via Qes). The requirements on the Qts value can vary between designs. So, there is actually no universally optimal Qts value, and no universally optimal series resistance (=damping factor) for a loudspeaker DRIVER. For the engineer, the series resistance can be seen as an interesting opportunity to change the Qts value. To make use of this opportunity, the speaker system would have to be designed *together* with the series resistance, and would typically include a built-in amplifier. Positive resistor values could be realised with an ordinary resistor, but in order to avoid power loss, it can be realised with negative feedback of the driver current. Negative resistances can be realised with positive feedback of the driver current. Commercially available non-amplified speaker systems are however almost always designed for a near-zero series impedance, probably because most amplifiers have a near-zero output impedance. BTW, having understood these effects it appears clear that the value of extremely low cable resistances and/or extremely high damping factors is questionable, IMO. As an example, 100 milliohm series resistance change would correspond to the resistance change due to a temperature raise of about 7 degrees celcius of the (4 ohm) voice coil. Am I drifting off the topic...? :-) |
#44
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SS subwoofer amplifier with high-ish output impedance?
(unitron) wrote in message . com...
(dangling entity) wrote in message . com... Is there some practical way to do this by doing something funky in the feedback loop or something? Would there be considerable downsides wrt the operation of the amplifier itself? Excessive thermal dissipation in the amplifier output stages, for instance? Do SS amplifiers like this already exist (for one reason or another), or would this be relatively virgin territory? Are you looking for something to drive a novel design of low audio (or sub-audio) frequency electrical current to air pressure transducer, perhaps novel enough that conventional terms such as speaker and subwoofer are inadequate? If it's something you may seek a patent for, and therefore wish to withhold details, can you at least reveal input impedence and power requirements? Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? Fiddling with the series resistance affects the drivers Qts value (via Qes). The requirements on the Qts value can vary between designs. So, there is actually no universally optimal Qts value, and no universally optimal series resistance (=damping factor) for a loudspeaker DRIVER. For the engineer, the series resistance can be seen as an interesting opportunity to change the Qts value. To make use of this opportunity, the speaker system would have to be designed *together* with the series resistance, and would typically include a built-in amplifier. Positive resistor values could be realised with an ordinary resistor, but in order to avoid power loss, it can be realised with negative feedback of the driver current. Negative resistances can be realised with positive feedback of the driver current. Commercially available non-amplified speaker systems are however almost always designed for a near-zero series impedance, probably because most amplifiers have a near-zero output impedance. BTW, having understood these effects it appears clear that the value of extremely low cable resistances and/or extremely high damping factors is questionable, IMO. As an example, 100 milliohm series resistance change would correspond to the resistance change due to a temperature raise of about 7 degrees celcius of the (4 ohm) voice coil. Am I drifting off the topic...? :-) |
#45
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SS subwoofer amplifier with high-ish output impedance?
(unitron) wrote in message . com...
(dangling entity) wrote in message . com... Is there some practical way to do this by doing something funky in the feedback loop or something? Would there be considerable downsides wrt the operation of the amplifier itself? Excessive thermal dissipation in the amplifier output stages, for instance? Do SS amplifiers like this already exist (for one reason or another), or would this be relatively virgin territory? Are you looking for something to drive a novel design of low audio (or sub-audio) frequency electrical current to air pressure transducer, perhaps novel enough that conventional terms such as speaker and subwoofer are inadequate? If it's something you may seek a patent for, and therefore wish to withhold details, can you at least reveal input impedence and power requirements? Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? Fiddling with the series resistance affects the drivers Qts value (via Qes). The requirements on the Qts value can vary between designs. So, there is actually no universally optimal Qts value, and no universally optimal series resistance (=damping factor) for a loudspeaker DRIVER. For the engineer, the series resistance can be seen as an interesting opportunity to change the Qts value. To make use of this opportunity, the speaker system would have to be designed *together* with the series resistance, and would typically include a built-in amplifier. Positive resistor values could be realised with an ordinary resistor, but in order to avoid power loss, it can be realised with negative feedback of the driver current. Negative resistances can be realised with positive feedback of the driver current. Commercially available non-amplified speaker systems are however almost always designed for a near-zero series impedance, probably because most amplifiers have a near-zero output impedance. BTW, having understood these effects it appears clear that the value of extremely low cable resistances and/or extremely high damping factors is questionable, IMO. As an example, 100 milliohm series resistance change would correspond to the resistance change due to a temperature raise of about 7 degrees celcius of the (4 ohm) voice coil. Am I drifting off the topic...? :-) |
#46
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SS subwoofer amplifier with high-ish output impedance?
I'd say svante is pretty much riding the same wavelength I am, in
requesting info on such an odd setup. Negative current feedback, but watchout for instability, eh? Interesting! So would such a configuration bring about other barriers to high power output (as in subwoofer amp sort of watts), relative to conventional low Z-out amplifiers? |
#47
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SS subwoofer amplifier with high-ish output impedance?
I'd say svante is pretty much riding the same wavelength I am, in
requesting info on such an odd setup. Negative current feedback, but watchout for instability, eh? Interesting! So would such a configuration bring about other barriers to high power output (as in subwoofer amp sort of watts), relative to conventional low Z-out amplifiers? |
#48
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SS subwoofer amplifier with high-ish output impedance?
I'd say svante is pretty much riding the same wavelength I am, in
requesting info on such an odd setup. Negative current feedback, but watchout for instability, eh? Interesting! So would such a configuration bring about other barriers to high power output (as in subwoofer amp sort of watts), relative to conventional low Z-out amplifiers? |
#49
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SS subwoofer amplifier with high-ish output impedance?
I'd say svante is pretty much riding the same wavelength I am, in
requesting info on such an odd setup. Negative current feedback, but watchout for instability, eh? Interesting! So would such a configuration bring about other barriers to high power output (as in subwoofer amp sort of watts), relative to conventional low Z-out amplifiers? |
#50
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SS subwoofer amplifier with high-ish output impedance?
(Svante) wrote in message . com...
(unitron) wrote in message . com... ---SNIP!--- Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? --and then Svante wrote a bunch of smart stuff I could only sort of grasp, followed by-- Am I drifting off the topic...? :-) I knew I shouldn't have mentioned religion, I mean, damping factor :-) Seriously, my question was mostly about why someone would want an amp intended to drive a speaker to have a high output impedence when the general trend is to build 'em so that they won't let the magic smoke out when someone parallels a second speaker on the output. |
#51
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SS subwoofer amplifier with high-ish output impedance?
(Svante) wrote in message . com...
(unitron) wrote in message . com... ---SNIP!--- Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? --and then Svante wrote a bunch of smart stuff I could only sort of grasp, followed by-- Am I drifting off the topic...? :-) I knew I shouldn't have mentioned religion, I mean, damping factor :-) Seriously, my question was mostly about why someone would want an amp intended to drive a speaker to have a high output impedence when the general trend is to build 'em so that they won't let the magic smoke out when someone parallels a second speaker on the output. |
#52
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SS subwoofer amplifier with high-ish output impedance?
(Svante) wrote in message . com...
(unitron) wrote in message . com... ---SNIP!--- Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? --and then Svante wrote a bunch of smart stuff I could only sort of grasp, followed by-- Am I drifting off the topic...? :-) I knew I shouldn't have mentioned religion, I mean, damping factor :-) Seriously, my question was mostly about why someone would want an amp intended to drive a speaker to have a high output impedence when the general trend is to build 'em so that they won't let the magic smoke out when someone parallels a second speaker on the output. |
#53
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SS subwoofer amplifier with high-ish output impedance?
(Svante) wrote in message . com...
(unitron) wrote in message . com... ---SNIP!--- Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? --and then Svante wrote a bunch of smart stuff I could only sort of grasp, followed by-- Am I drifting off the topic...? :-) I knew I shouldn't have mentioned religion, I mean, damping factor :-) Seriously, my question was mostly about why someone would want an amp intended to drive a speaker to have a high output impedence when the general trend is to build 'em so that they won't let the magic smoke out when someone parallels a second speaker on the output. |
#54
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SS subwoofer amplifier with high-ish output impedance?
(dangling entity) wrote in message . com...
I'd say svante is pretty much riding the same wavelength I am, in requesting info on such an odd setup. Negative current feedback, but watchout for instability, eh? Interesting! So would such a configuration bring about other barriers to high power output (as in subwoofer amp sort of watts), relative to conventional low Z-out amplifiers? Let's see if I understand your question correctly; the maximum output would normally not be affected, since it is determined by Xmax of the driver for low frequencies. The main effect would as I said be an alteration of Qts and a lowered efficiency if the resistor is passive. In our loudspeaker laboration we actually use a series resistance to tune the Qts of a driver. The lab instructions http://www.speech.kth.se/~svante/elak/htlab.pdf are in swedish, sorry, but you can find the equation for calculating the series resistance on page 14, equation 11. Q'ts is the Qts you want, Qts is what you have. It's a horrible equation and students *never* get it right the first time, so check it carefully before relying on your results. All variables should be entered in SI units, ie m3, m2, m/s etc. HTH /Svante |
#55
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SS subwoofer amplifier with high-ish output impedance?
(dangling entity) wrote in message . com...
I'd say svante is pretty much riding the same wavelength I am, in requesting info on such an odd setup. Negative current feedback, but watchout for instability, eh? Interesting! So would such a configuration bring about other barriers to high power output (as in subwoofer amp sort of watts), relative to conventional low Z-out amplifiers? Let's see if I understand your question correctly; the maximum output would normally not be affected, since it is determined by Xmax of the driver for low frequencies. The main effect would as I said be an alteration of Qts and a lowered efficiency if the resistor is passive. In our loudspeaker laboration we actually use a series resistance to tune the Qts of a driver. The lab instructions http://www.speech.kth.se/~svante/elak/htlab.pdf are in swedish, sorry, but you can find the equation for calculating the series resistance on page 14, equation 11. Q'ts is the Qts you want, Qts is what you have. It's a horrible equation and students *never* get it right the first time, so check it carefully before relying on your results. All variables should be entered in SI units, ie m3, m2, m/s etc. HTH /Svante |
#56
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SS subwoofer amplifier with high-ish output impedance?
(dangling entity) wrote in message . com...
I'd say svante is pretty much riding the same wavelength I am, in requesting info on such an odd setup. Negative current feedback, but watchout for instability, eh? Interesting! So would such a configuration bring about other barriers to high power output (as in subwoofer amp sort of watts), relative to conventional low Z-out amplifiers? Let's see if I understand your question correctly; the maximum output would normally not be affected, since it is determined by Xmax of the driver for low frequencies. The main effect would as I said be an alteration of Qts and a lowered efficiency if the resistor is passive. In our loudspeaker laboration we actually use a series resistance to tune the Qts of a driver. The lab instructions http://www.speech.kth.se/~svante/elak/htlab.pdf are in swedish, sorry, but you can find the equation for calculating the series resistance on page 14, equation 11. Q'ts is the Qts you want, Qts is what you have. It's a horrible equation and students *never* get it right the first time, so check it carefully before relying on your results. All variables should be entered in SI units, ie m3, m2, m/s etc. HTH /Svante |
#57
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SS subwoofer amplifier with high-ish output impedance?
(dangling entity) wrote in message . com...
I'd say svante is pretty much riding the same wavelength I am, in requesting info on such an odd setup. Negative current feedback, but watchout for instability, eh? Interesting! So would such a configuration bring about other barriers to high power output (as in subwoofer amp sort of watts), relative to conventional low Z-out amplifiers? Let's see if I understand your question correctly; the maximum output would normally not be affected, since it is determined by Xmax of the driver for low frequencies. The main effect would as I said be an alteration of Qts and a lowered efficiency if the resistor is passive. In our loudspeaker laboration we actually use a series resistance to tune the Qts of a driver. The lab instructions http://www.speech.kth.se/~svante/elak/htlab.pdf are in swedish, sorry, but you can find the equation for calculating the series resistance on page 14, equation 11. Q'ts is the Qts you want, Qts is what you have. It's a horrible equation and students *never* get it right the first time, so check it carefully before relying on your results. All variables should be entered in SI units, ie m3, m2, m/s etc. HTH /Svante |
#58
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SS subwoofer amplifier with high-ish output impedance?
(unitron) wrote in message . com...
(Svante) wrote in message . com... (unitron) wrote in message . com... ---SNIP!--- Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? --and then Svante wrote a bunch of smart stuff I could only sort of grasp, followed by-- Am I drifting off the topic...? :-) I knew I shouldn't have mentioned religion, I mean, damping factor :-) Seriously, my question was mostly about why someone would want an amp intended to drive a speaker to have a high output impedence when the general trend is to build 'em so that they won't let the magic smoke out when someone parallels a second speaker on the output. In the normal case it is a good idea to have a *reasonably* low output impedance, firstly because most speaker systems are designed for such an amplifier, secondly for the thing you mention about paralleling more than one speaker. The non-zero output impedance would have to be designed knowing the loudspeaker that is connected to it. Such a design should be integrated in the loudspeaker system. |
#59
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SS subwoofer amplifier with high-ish output impedance?
(unitron) wrote in message . com...
(Svante) wrote in message . com... (unitron) wrote in message . com... ---SNIP!--- Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? --and then Svante wrote a bunch of smart stuff I could only sort of grasp, followed by-- Am I drifting off the topic...? :-) I knew I shouldn't have mentioned religion, I mean, damping factor :-) Seriously, my question was mostly about why someone would want an amp intended to drive a speaker to have a high output impedence when the general trend is to build 'em so that they won't let the magic smoke out when someone parallels a second speaker on the output. In the normal case it is a good idea to have a *reasonably* low output impedance, firstly because most speaker systems are designed for such an amplifier, secondly for the thing you mention about paralleling more than one speaker. The non-zero output impedance would have to be designed knowing the loudspeaker that is connected to it. Such a design should be integrated in the loudspeaker system. |
#60
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SS subwoofer amplifier with high-ish output impedance?
(unitron) wrote in message . com...
(Svante) wrote in message . com... (unitron) wrote in message . com... ---SNIP!--- Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? --and then Svante wrote a bunch of smart stuff I could only sort of grasp, followed by-- Am I drifting off the topic...? :-) I knew I shouldn't have mentioned religion, I mean, damping factor :-) Seriously, my question was mostly about why someone would want an amp intended to drive a speaker to have a high output impedence when the general trend is to build 'em so that they won't let the magic smoke out when someone parallels a second speaker on the output. In the normal case it is a good idea to have a *reasonably* low output impedance, firstly because most speaker systems are designed for such an amplifier, secondly for the thing you mention about paralleling more than one speaker. The non-zero output impedance would have to be designed knowing the loudspeaker that is connected to it. Such a design should be integrated in the loudspeaker system. |
#61
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SS subwoofer amplifier with high-ish output impedance?
(unitron) wrote in message . com...
(Svante) wrote in message . com... (unitron) wrote in message . com... ---SNIP!--- Ordinarily wouldn't lower amp output impedence be better from a standpoint of damping factor and not being subjected to too low of a load impedence (i.e., too great a load, drawing too much current)? --and then Svante wrote a bunch of smart stuff I could only sort of grasp, followed by-- Am I drifting off the topic...? :-) I knew I shouldn't have mentioned religion, I mean, damping factor :-) Seriously, my question was mostly about why someone would want an amp intended to drive a speaker to have a high output impedence when the general trend is to build 'em so that they won't let the magic smoke out when someone parallels a second speaker on the output. In the normal case it is a good idea to have a *reasonably* low output impedance, firstly because most speaker systems are designed for such an amplifier, secondly for the thing you mention about paralleling more than one speaker. The non-zero output impedance would have to be designed knowing the loudspeaker that is connected to it. Such a design should be integrated in the loudspeaker system. |
#62
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SS subwoofer amplifier with high-ish output impedance?
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#63
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SS subwoofer amplifier with high-ish output impedance?
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#64
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SS subwoofer amplifier with high-ish output impedance?
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#66
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SS subwoofer amplifier with high-ish output impedance?
(dangling entity) wrote in message . com...
(Svante) wrote in message . com... Let's see if I understand your question correctly; the maximum output would normally not be affected, since it is determined by Xmax of the driver for low frequencies. The meaning I intended was really asking about the *amplifier*. Would the amplifier experience difficulty with this new feedback setup in delivering rated output, overheating, driving the targeted speaker at frequencies where the impedance hits the mins, etc.? Basically, I'm asking if this feedback scheme places additional stresses on the amplifier such that it doesn't perform as well as it did when it was a plain ole low-Z amplifier? Negative and positive current feedback has been used at least since the sixties, so I'd say it is safe to say that it is practically possible to use this scheme. As always with feedback, there is the risk of self-oscillation, which has to be taken care of. In the case with a single electrodynamic driver connected to such an amp, there *should* not be much of a problem, since the impedance of the voice coil is high for HF, resulting in a low current and low feedback at HF. If you are new to it, do some experimenting with inexpensive parts first, to be on the safe side. :-) |
#67
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SS subwoofer amplifier with high-ish output impedance?
(dangling entity) wrote in message . com...
(Svante) wrote in message . com... Let's see if I understand your question correctly; the maximum output would normally not be affected, since it is determined by Xmax of the driver for low frequencies. The meaning I intended was really asking about the *amplifier*. Would the amplifier experience difficulty with this new feedback setup in delivering rated output, overheating, driving the targeted speaker at frequencies where the impedance hits the mins, etc.? Basically, I'm asking if this feedback scheme places additional stresses on the amplifier such that it doesn't perform as well as it did when it was a plain ole low-Z amplifier? Negative and positive current feedback has been used at least since the sixties, so I'd say it is safe to say that it is practically possible to use this scheme. As always with feedback, there is the risk of self-oscillation, which has to be taken care of. In the case with a single electrodynamic driver connected to such an amp, there *should* not be much of a problem, since the impedance of the voice coil is high for HF, resulting in a low current and low feedback at HF. If you are new to it, do some experimenting with inexpensive parts first, to be on the safe side. :-) |
#68
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SS subwoofer amplifier with high-ish output impedance?
(dangling entity) wrote in message . com...
(Svante) wrote in message . com... Let's see if I understand your question correctly; the maximum output would normally not be affected, since it is determined by Xmax of the driver for low frequencies. The meaning I intended was really asking about the *amplifier*. Would the amplifier experience difficulty with this new feedback setup in delivering rated output, overheating, driving the targeted speaker at frequencies where the impedance hits the mins, etc.? Basically, I'm asking if this feedback scheme places additional stresses on the amplifier such that it doesn't perform as well as it did when it was a plain ole low-Z amplifier? Negative and positive current feedback has been used at least since the sixties, so I'd say it is safe to say that it is practically possible to use this scheme. As always with feedback, there is the risk of self-oscillation, which has to be taken care of. In the case with a single electrodynamic driver connected to such an amp, there *should* not be much of a problem, since the impedance of the voice coil is high for HF, resulting in a low current and low feedback at HF. If you are new to it, do some experimenting with inexpensive parts first, to be on the safe side. :-) |
#69
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SS subwoofer amplifier with high-ish output impedance?
(dangling entity) wrote in message . com...
(Svante) wrote in message . com... Let's see if I understand your question correctly; the maximum output would normally not be affected, since it is determined by Xmax of the driver for low frequencies. The meaning I intended was really asking about the *amplifier*. Would the amplifier experience difficulty with this new feedback setup in delivering rated output, overheating, driving the targeted speaker at frequencies where the impedance hits the mins, etc.? Basically, I'm asking if this feedback scheme places additional stresses on the amplifier such that it doesn't perform as well as it did when it was a plain ole low-Z amplifier? Negative and positive current feedback has been used at least since the sixties, so I'd say it is safe to say that it is practically possible to use this scheme. As always with feedback, there is the risk of self-oscillation, which has to be taken care of. In the case with a single electrodynamic driver connected to such an amp, there *should* not be much of a problem, since the impedance of the voice coil is high for HF, resulting in a low current and low feedback at HF. If you are new to it, do some experimenting with inexpensive parts first, to be on the safe side. :-) |
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