Ohm's law states that for an equal output voltage from the audio amplifier, the power delivered to a 4-ohm speaker will be twice the power delivered to an 8-ohm speaker.Want to know Advantages n Disadvantages
Which is better? and why??
Questions of better, why, and advantage have to be answered in the context of the whole system, IMHO.
The way the pioneers looked at it, so I do too, higher impedance = less current draw = less thermal power compression for a given SPL and lower build/power distribution cost, so for other than mobile audio apps where voltage is severely limited, I don't understand why there's been a shift to lower impedance systems in prosound, consequently to many of the high SPL HIFI/HT systems that use at least the woofers, so what am I missing/forgotten?
GM
GM
@ GM
Hi,
But watts are watts, for the same SPL @ 4 Ohms more current = less volts, @ 8 Ohms less current = more volts. The power delivered/consumed is the same !
The build costs would actually be higher for the same power into 8 Ohms, due to the Amps needing a higher voltage power supply. Mains power distribution costs "could" be lower @ 8 ohms, due to being able to use less thick cable on mains & speakers.
So more speakers can be run in parallel on each Amp = less Amps & racks & weight etc. Often the Amps are placed near the speakers so not much speaker cable required. Also some speakers are Active = no external speaker cable needed.
Hi,
But watts are watts, for the same SPL @ 4 Ohms more current = less volts, @ 8 Ohms less current = more volts. The power delivered/consumed is the same !
The build costs would actually be higher for the same power into 8 Ohms, due to the Amps needing a higher voltage power supply. Mains power distribution costs "could" be lower @ 8 ohms, due to being able to use less thick cable on mains & speakers.
So more speakers can be run in parallel on each Amp = less Amps & racks & weight etc. Often the Amps are placed near the speakers so not much speaker cable required. Also some speakers are Active = no external speaker cable needed.
If I may ask some related questions out of purely self-interest... 
I run a 2Ohm stereo setup, as you can see in my build thread.
A person (well-known for various reasons on various audio fora, from what I can see) has aggressively insisted to me that:
- 2Ohm means the power is 'very uncontrolled' to the subwoofer(s);
- distortion from amplifiers increases with lower impedance (apparently ten-fold going from 8Ohm to 4Ohm);
- the rate of increase of distortion increases as impedance goes lower;
- double-digit distortion will definitely be aubibly worse [at subwoofer frequencies];
- at 2Ohm there is zero resistance to Back EMF distortion travelling back to the amp;
- 2Ohm increases 'wear and tear' so much on an amp that it will simply kill it in a short period of time; and
- I need to add an unbalanced-to-balanced conversion box into my signal chain, between the AVR and the sub amp, because the amp is not receiving 'a full pro audio signal' and is therefore not putting out what it could. (He has not responded to my point that adjustment of the gain knob on the amp should compensate for a small(er) input signal, AIUI.)
All of these claims have not been backed up with any documentary evidence.
Am I correct in thinking I should not worry about 2Ohm? As far as I am concerned my current (PPSL DIY) subs are the best I've ever heard, and I personally doubt re-wiring from 2Ohm to 8Ohm will have any measurable or at least noticeable difference...
I run a 2Ohm stereo setup, as you can see in my build thread.
A person (well-known for various reasons on various audio fora, from what I can see) has aggressively insisted to me that:
- 2Ohm means the power is 'very uncontrolled' to the subwoofer(s);
- distortion from amplifiers increases with lower impedance (apparently ten-fold going from 8Ohm to 4Ohm);
- the rate of increase of distortion increases as impedance goes lower;
- double-digit distortion will definitely be aubibly worse [at subwoofer frequencies];
- at 2Ohm there is zero resistance to Back EMF distortion travelling back to the amp;
- 2Ohm increases 'wear and tear' so much on an amp that it will simply kill it in a short period of time; and
- I need to add an unbalanced-to-balanced conversion box into my signal chain, between the AVR and the sub amp, because the amp is not receiving 'a full pro audio signal' and is therefore not putting out what it could. (He has not responded to my point that adjustment of the gain knob on the amp should compensate for a small(er) input signal, AIUI.)
All of these claims have not been backed up with any documentary evidence.
Am I correct in thinking I should not worry about 2Ohm? As far as I am concerned my current (PPSL DIY) subs are the best I've ever heard, and I personally doubt re-wiring from 2Ohm to 8Ohm will have any measurable or at least noticeable difference...
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Is your supply voltage limited?
That will determine whether you need to look at 2ohms, or 4ohms, or 8ohms capable amplifiers.
For a supply that is not limited, then a higher load impedance always allows the amplifier to perform better, even when it is capable of driving the lower impedance.
I would never try to design a 2ohms capable amplifier.
I would not design a 4ohms capable amplifier because I know that an 8ohms load will allow better performance. See some of the data given by D.Self over the last 20years.
Low impedance loads ALWAYS result in higher losses compared to high impedance loads.
That will determine whether you need to look at 2ohms, or 4ohms, or 8ohms capable amplifiers.
For a supply that is not limited, then a higher load impedance always allows the amplifier to perform better, even when it is capable of driving the lower impedance.
I would never try to design a 2ohms capable amplifier.
I would not design a 4ohms capable amplifier because I know that an 8ohms load will allow better performance. See some of the data given by D.Self over the last 20years.
Low impedance loads ALWAYS result in higher losses compared to high impedance loads.
" so what am I missing/forgotten?"
Not a thing.
http://i56.photobucket.com/albums/g196/dkleitsch/CoePA-2009.jpg
Each dual 15 cabinet is 8Ω, so in a pinch all four may be run on an amplifier that can safely drive 2Ω
I buy amplifiers that can drive 2Ω, but don't run them below 4Ω, except in an emergency.
4Ω is a lot more forgiving for wire selection as well.
Not a thing.
http://i56.photobucket.com/albums/g196/dkleitsch/CoePA-2009.jpg
Each dual 15 cabinet is 8Ω, so in a pinch all four may be run on an amplifier that can safely drive 2Ω
I buy amplifiers that can drive 2Ω, but don't run them below 4Ω, except in an emergency.
4Ω is a lot more forgiving for wire selection as well.
I would always prefer 16 ohm drivers (or even higher) if they were always available and I would not need the higher USPL sensitivity of the lower impedance version of the driver. Higher impedance version of the driver usually tends to measure better than the lower impedance versions due to current drive aspects.
Thanks for the inpot re: 2Ohms, chaps - I will find and read the D.Self work so I can make myself a bit more knowledgable as to the reasons!
FWIW I rarely crank my system up to anywhere near its potential, and when I do, I am pretty sure I'm not giving them anywhere near what they would take, due to the fact I am in a flat and don't want the neighbours banging on the door (again... lol) Films and classical music are about the only things I listen to loud, and most of those have short sharp transients rather than sustained big power draws!
FWIW I rarely crank my system up to anywhere near its potential, and when I do, I am pretty sure I'm not giving them anywhere near what they would take, due to the fact I am in a flat and don't want the neighbours banging on the door (again... lol) Films and classical music are about the only things I listen to loud, and most of those have short sharp transients rather than sustained big power draws!
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