** The gauge of wire used inside a speaker to make the voice coil has NO effect on efficiency. The same speaker could be produced with impedance anywhere from 0.5 ohms to 50 ohms just by altering the wire gauge. The important thing is that the same overall VOLUME of copper is used to make the coil.
The voltages that amplifiers deliver to speakers is kept within safe limits if the speaker is no more than 8 to 16 ohms. A 100 ohm speaker would require dangerously a high drive voltage at power levels of 50 watts or more ( ie 70 volts rms) and hence preclude domestic use.
They are obviously not common but what are the pro's and cons? I can't think of any cons except the higher voltage. Lower current = more efficient, smaller wire, etc...
High impedance speakers are common in commercial settings where 100V and 70V public address wiring is common. usually ordinary 8 ohm loudspeakers are used with a transformer to convert the impedance.
Often the transformer has a several taps and and switch to select between them allowing the volume to be ajdusted at the output without using a wasteful L-pad.
the 8 ohm speaker in combination with the transformer form a high impedance speaker.
That's a different application. Since the wiring maybe long, it makes sense to use higher voltage so the current is lower for the same power, and thus the higher resistance accumulated over the longer wires will not affect things the way it would if low voltage higher current audio was going through those lines.
Consider the other issues: insulation thickness, temperature variations, and magnetic gap. Imagine a 240 volt speaker driven by a common 3 phase power transmission line from the grid . This is a loud siren for tsunami alarms. The insulation must be thicker than for varnished magnet wire. Thick insulation keeps heat building up to bad temperatures. Thick insulation increases the gap between the wires in the moving parts and the permanent magnet or electromagnet. Tradeoffs between competing physical effects may be calculated.
Consider the other issues: insulation thickness, temperature variations, and magnetic gap. Imagine a 240 volt speaker driven by a common 3 phase power transmission line from the grid . This is a loud siren for tsunami alarms. The insulation must be thicker than for varnished magnet wire. Thick insulation keeps heat building up to bad temperatures. Thick insulation increases the gap between the wires in the moving parts and the permanent magnet or electromagnet. Tradeoffs between competing physical effects may be calculated.
Consider the other issues: insulation thickness, temperature variations, and magnetic gap. Imagine a 240 volt speaker driven by a common 3 phase power transmission line from the grid . This is a loud siren for tsunami alarms. The insulation must be thicker than for varnished magnet wire. Thick insulation keeps heat building up to bad temperatures. Thick insulation increases the gap between the wires in the moving parts and the permanent magnet or electromagnet. Tradeoffs between competing physical effects may be calculated.
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None of the responses give the pro's of high voltage though. Obviously higher current = higher temperature = thicker wire and/or insulation, larger speaker magnetics, larger transformers, etc. As far as I can tell it is much easier to use higher voltage speakers from all perspectives except the high voltage itself as it could pose a health hazard.
So is there any real real cons besides the high voltage itself? If not then why do we even use high current(verses high voltage) speakers in the first place? Old tube radios used higher voltage speakers(I have a couple of them and they are much higher impedances(1k's+). Surely there has to be a reason why high current was chosen over high voltage. Best I can guess is that it has something to do with efficiency of the magnetics... it's really just a guess though.
The other reason (actually *the* reason) for 70V (or 100V) PA distribution systems is it issue of impedance matching when you have a large and arbitrary number of speakers.
Suppose you had a typical home-stereo power amp, with a minimum recommended load impedance of (say) 4 ohms, and you want each channel to drive a number of speakers. If you want to drive 2 speakers per channel, you can put two 8-ohm speakers in parallel. If you want to drive 4, you can have two branches in parallel, each with two 4-ohm speakers in series. And so on. But it's a major headache for arbitrary numbers (like odd numbers), and it's totally impractical if you want to add or remove speakers later.
With 70/100V distribution you just put all the speakers in parallel, with each having its own step-down transformer from the high-impedance (and high voltage) distribution wiring to a standard 8 ohm (or whatever) speaker.
See for example
(That's not a plug for the company, just the first non-PDF that Google came up with.)
Best regards,
Bob Masta DAQARTA v6.01 Data AcQuisition And Real-Time Analysis
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High impedance speakers are common in commercial settings where 100V and 70V public address wiring is common. usually ordinary 8 ohm loudspeakers are used with a transformer to convert the impedance.
Often the transformer has a several taps and and switch to select between them allowing the volume to be ajdusted at the output without using a wasteful L-pad.
the 8 ohm speaker in combination with the transformer form a high impedance speaker.
------------------- I suppose high current speakers could have been chosen over high voltage speakers because of this reason since putting them in series would require unsafe voltages? e.g., if you have 10 speakers at 100V each the total voltage then would be 1kV vs around 20V-30V for your average speakers. Of course 95% of speakers are not used in PA's so that is not a really good reason but who knows...
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