4 ohm speakers are more demanding in terms of current but need less voltage.
An 8 ohm speaker with a sensitivity of 90db at 1watt needs 2.83 volts across its terminals to achieve the 1 watt.
A 4 ohm speaker rated at 90db at 1 watt would need just 2 volts.
So often amplifiers specified for 4 ohm loading may be specified to run on seemingly lower supply voltages.
Lower impedance does mean more current. At clipping the amp would be delivering over 5.5 amps (rms) into the load but as I have said before, continuous power testing into dummy loads is a world apart from very loud music.
If you look at how much voltage you actually need across the speaker terminals then you might be in for a surprise. Its not much for even loud music.
Have you tried this, it is well worth doing and only takes a few minutes:
A Test. How much Voltage (power) do your speakers need?
An 8 ohm speaker with a sensitivity of 90db at 1watt needs 2.83 volts across its terminals to achieve the 1 watt.
A 4 ohm speaker rated at 90db at 1 watt would need just 2 volts.
So often amplifiers specified for 4 ohm loading may be specified to run on seemingly lower supply voltages.
Lower impedance does mean more current. At clipping the amp would be delivering over 5.5 amps (rms) into the load but as I have said before, continuous power testing into dummy loads is a world apart from very loud music.
If you look at how much voltage you actually need across the speaker terminals then you might be in for a surprise. Its not much for even loud music.
Have you tried this, it is well worth doing and only takes a few minutes:
A Test. How much Voltage (power) do your speakers need?
Yes I have heard of it before, and have now looked trough the test, thanks🙂
It is all together fine but something is "wrong-ish" why would anyone ever invent any home user amplifier above 3W if you already have rock concert at 2W in your living room?
By according to that calculation could you entertain a whole street for an hour, just by mounting a 9V battery. 🙂 Something is going over my head here! 🙂
It is all together fine but something is "wrong-ish" why would anyone ever invent any home user amplifier above 3W if you already have rock concert at 2W in your living room?
By according to that calculation could you entertain a whole street for an hour, just by mounting a 9V battery. 🙂 Something is going over my head here! 🙂
Well it may seem that way, however lets put some numbers in.
A 9V battery can only pull or push the speaker cone one way at a time. You need to physically reverse the leads. So to move the cone in and out we would need to swing 4.5 volts one way and 4.5 the other.
4.5V (peak) is just 3.2 volts rms. That would give just 1.3 watts approx (rms) but remember that our amplifiers are not so efficient that they can put that voltage across the load. Typically you might get say 3.5V peak (and that would be pretty good into an 8 ohm load). Now we are down to 760 milliwatts.
3.5V would be the peak voltage available which means on music it would the infrequent transients. The bulk of the signal would be way below those peaks and so our 9 volt battery doesn't really give all that much really loud volume.
You need to try that test, it is very very revealing.
Have a look at post #44
A Test. How much Voltage (power) do your speakers need?
Post #775
A Test. How much Voltage (power) do your speakers need?
Try the test 🙂
A 9V battery can only pull or push the speaker cone one way at a time. You need to physically reverse the leads. So to move the cone in and out we would need to swing 4.5 volts one way and 4.5 the other.
4.5V (peak) is just 3.2 volts rms. That would give just 1.3 watts approx (rms) but remember that our amplifiers are not so efficient that they can put that voltage across the load. Typically you might get say 3.5V peak (and that would be pretty good into an 8 ohm load). Now we are down to 760 milliwatts.
3.5V would be the peak voltage available which means on music it would the infrequent transients. The bulk of the signal would be way below those peaks and so our 9 volt battery doesn't really give all that much really loud volume.
You need to try that test, it is very very revealing.
Have a look at post #44
A Test. How much Voltage (power) do your speakers need?
Post #775
A Test. How much Voltage (power) do your speakers need?
Try the test 🙂
Right now do I only have my sound editing system that runs via a mixer and a set of active speakers. So I have problem running any test but I have seen and tried calculations where the result is very low.
But why did you go for about 50W, why 1000W in some high end speakers bass control?
If 1W at one meter can blast your ears off? 🙂
But why did you go for about 50W, why 1000W in some high end speakers bass control?
If 1W at one meter can blast your ears off? 🙂
There are several other factors behind it.
- we rarely want to sit one meter from the speaker
- 1W at one meter, of a test tone, seems louder than pink noise or music
- bass speakers are invariably less efficient than tweeters and mids
- psychology plays a role -- twice the 'power capability' will probably always 'register' as more compelling, even if we're not using it
- power semiconductors are cheap compared to 'big iron' -- we build bigger amps 'because we can'
Cheers
- we rarely want to sit one meter from the speaker
- 1W at one meter, of a test tone, seems louder than pink noise or music
- bass speakers are invariably less efficient than tweeters and mids
- psychology plays a role -- twice the 'power capability' will probably always 'register' as more compelling, even if we're not using it
- power semiconductors are cheap compared to 'big iron' -- we build bigger amps 'because we can'
Cheers
Am I understand this correctly? By mixing Mooly's and your explanations.
In a imaginary perfect system, 5W would be fine for any system up to insane volume but since everything is not perfect, have loses, do not react instantaneously and all in all is a mess of impedance, mechanical resistance and so on, you do need extra power to compensate for that? But when that is said, do we in fact need fare less Wattage then one would think, no need for buying a 500W amp because you would never use it?
About the psychology of the Watt, yes I have seen people talking exited about there system being able of 2500W and so on but often do I think it's more bragging right then usefull🙂
Thing that can impress me (don't know if it have any foundation in reality) a 25W amplifier weighing 100 lbs because a 1000VA transformer with 250,000 uF capacity and a headroom of maybe 6-10 dB. That tells me that it don't give a sh*t what you ask it to do, it just do it!! 🙂
In a imaginary perfect system, 5W would be fine for any system up to insane volume but since everything is not perfect, have loses, do not react instantaneously and all in all is a mess of impedance, mechanical resistance and so on, you do need extra power to compensate for that? But when that is said, do we in fact need fare less Wattage then one would think, no need for buying a 500W amp because you would never use it?
About the psychology of the Watt, yes I have seen people talking exited about there system being able of 2500W and so on but often do I think it's more bragging right then usefull🙂
Thing that can impress me (don't know if it have any foundation in reality) a 25W amplifier weighing 100 lbs because a 1000VA transformer with 250,000 uF capacity and a headroom of maybe 6-10 dB. That tells me that it don't give a sh*t what you ask it to do, it just do it!! 🙂
OK, so your current system isn't suitable for The Test since you don't have easy direct access to the speaker terminals. Still, reading just a few dozen of those posts can be pretty revealing -- there're 1200 of 'em 😉
On your hypothetical 100 lb, 25W amp -- would that be 6 - 10 dB headroom over the 25W? 'Cause that's 100 - 250W unclipped ..
Really, there's some pretty thoughtful stuff on there. Its good reading.
Cheers
PS: archimago blogspot has a bunch of great stuff concerning power, too. (referred to in that Pano thread)
PPS: No need to mix mine and Mooly's explanations -- just ignore mine! 😉
On your hypothetical 100 lb, 25W amp -- would that be 6 - 10 dB headroom over the 25W? 'Cause that's 100 - 250W unclipped ..
Really, there's some pretty thoughtful stuff on there. Its good reading.
Cheers
PS: archimago blogspot has a bunch of great stuff concerning power, too. (referred to in that Pano thread)
PPS: No need to mix mine and Mooly's explanations -- just ignore mine! 😉
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No my current system do only have XLR inputs but yes, as I have tried to say, I have read about it and did it again after it came up here on this thread🙂
Yes I meant a 25W with 250W headroom. Can't remember where I did listen to one with 6dB headroom but even at the "worst" passages where the classic music did try to kill the system, did that amplifier just shrug and kicked the speaker so hard it did not dare to do anything other then deliver the most clean sound🙂
LOL about ignoring your text, I chose to see it like this, no text is to be ignored, because every word from anybody, is a fantastic source for me to learn from different angles🙂
Yes I meant a 25W with 250W headroom. Can't remember where I did listen to one with 6dB headroom but even at the "worst" passages where the classic music did try to kill the system, did that amplifier just shrug and kicked the speaker so hard it did not dare to do anything other then deliver the most clean sound🙂
LOL about ignoring your text, I chose to see it like this, no text is to be ignored, because every word from anybody, is a fantastic source for me to learn from different angles🙂
> why would anyone ever invent any home user amplifier above 3W
Because since 1938, or 1968, you can add "value" to a product with a higher Watts number, because audio power has become incrementally cheaper every 30 years (today class D makes all old amp look sick, $/Watt). 30 Watts has GOT to be better than 3 Watts, right??
Because the "most you could want" is "soft". If 3 Watts is not enough, then 6 Watts won't be much better, and you may have to go 30 Watts to say "enough". Today. Tomorrow your ears are dulled and you need "still more" for the same thrill.
Amplifier power and woofer size are semi-complementary. An 8 foot horn fills a theater with 30 Watts. A 15" woofer in a 2 foot box will do nearly the same if 300 Watts is at hand. In 1928 only the big horn was practical. In 1968 to 1978 the super-amps got practical. While big horns were never popular at home or small clubs, we got more boom out of small woofers when we had high-power amps.
Because since 1938, or 1968, you can add "value" to a product with a higher Watts number, because audio power has become incrementally cheaper every 30 years (today class D makes all old amp look sick, $/Watt). 30 Watts has GOT to be better than 3 Watts, right??
Because the "most you could want" is "soft". If 3 Watts is not enough, then 6 Watts won't be much better, and you may have to go 30 Watts to say "enough". Today. Tomorrow your ears are dulled and you need "still more" for the same thrill.
Amplifier power and woofer size are semi-complementary. An 8 foot horn fills a theater with 30 Watts. A 15" woofer in a 2 foot box will do nearly the same if 300 Watts is at hand. In 1928 only the big horn was practical. In 1968 to 1978 the super-amps got practical. While big horns were never popular at home or small clubs, we got more boom out of small woofers when we had high-power amps.
We used to have a lecturer at college whose favourite expression when we were working on audio stuff was "50 milliwatts please" meaning that was quite loud enough.
As I understand it, is there "home user watt" and "stage watt" at home do you play up to a level you feel is right, no matter if you have 10 or 1000 Watt, while on stage do you need lots of real power to control lots of giant speakers and loud for hours is better.
As home user do the Amps tell about the ability to grip and control the speaker while Volt is the volume it can play at?
In other word, Volt is fine to have if the music goes high but normally is it not something you have to think about, the same about amps, unless your speaker is a brutal beast to drive, you do not have to get a welder or a tractor starter. But when that is said, it do not harm to have the extra power.
Is that right or a lot of gibberish? 🙂
As home user do the Amps tell about the ability to grip and control the speaker while Volt is the volume it can play at?
In other word, Volt is fine to have if the music goes high but normally is it not something you have to think about, the same about amps, unless your speaker is a brutal beast to drive, you do not have to get a welder or a tractor starter. But when that is said, it do not harm to have the extra power.
Is that right or a lot of gibberish? 🙂
At home you are generally in a small confined space and so that really puts a limit to how much energy you can pump into a given speaker and still have it sound good. There tends to be a 'loudness limit' in such a room where if you exceed that limit the sound just hardens up and becomes less satisfying.