This is a common question which I have always faced during my audio/ movie journey over the past 10 + years with opinions usually swinging from a low of 3-4 watts to a high of 200+ watts. Finally while reviewing some articles on the web and some videos on youtube I came across some answers which seem logical.
Based on these I arrived at the following conclusion for my Wharfedale Diamond 220 speakers which carry a sensitivity of 86 db.
Disclaimer: I am a finance professional, hence it is likely that I misunderstood some point on ohms/ decibels/watts
Basic assumption: With1 watt the speaker produces 86 db sound at a distance of 1 meter. To increase sound by every 3 db I need to double the wattage.
Actual SPL: While watching a recent movie I was recording the sound level using a SPL app on my phone. At a comfortable listening level in my Atmos HT, the peak was recorded at 97 db and the average SPL for about half an hour of viewing was recorded at about 85 db. So assuming worst case that I need 100 db of sound level all throughout (really loud), I will need about the following watts:
86db: 1 watt so
89 db: 2 watts
92 db: 4 watts
95 db: 8 watts
98 db: 16 watts
101 db: 32 watts
104 db: 64 watts
107 db: 128 watts
THX recommends 105 db for reference level movie watching but at that level it will get very uncomfortable. Hence to power ~ 98 db (peak) I will just need 16 watts per channel.
Now the catch is the 1 meter condition- that is I will need 16 watts to produce 98 db if I am seated at a distance of just 1 meter. Hence assuming that I am seated at 10 feet ( ~ 3 meters) I need to jump 2 levels and add another 6 db to the above calculation. Hence to listen at 98db (throughout) I will need about 64 watts per channel when seated at 3 meters from the speaker.
If the above is true then the following comes to light:
1. Most budget AVRs may not pump out 64 watts per channel in real world which is why they sound weak when pushed ? eg Marantz 1509 states 50 w per channel at 8 ohms with just 2 channels driven.
2. Always use efficient speakers (90 db +) which will reduce power requirement giving more headroom to the AVR/ amp
3. At times I have seen people recommending even stereo amps at 100 watts + per channel. However this may be too much since the requirement will depend upon the speaker efficiency and your distance from speaker and at what levels you listen to music.
4. I haven't measured but when listening to music the sound level would be 85- 90 db unless one is hosting a party ? In that case the wattage requirement could be even lower. This could be the reason why I find my 40 w per channel Rotel to be sound very powerful when powering the Diamond 220. Volume knob always at 9 o clock position or lower.
5. I am also assuming 32- 64 watts per channel would be the requirement to maintain 98-101 db continuously. Hence if this is only the peak requirement, then obviously the AVR doesn't need so much power across all channels at all times. Hence any AVR which claims 90-100 watts per channel with 2 channel driven at 8 ohms should be enough in most cases (given seating distance and speaker efficiency).
6. I always thought that small speakers must be easier to drive than large ones. Eg satellites must be the easiest compared to book shelves or floor standers. But I came across Klipsch floor standers with an astounding 98 db sensitivity. Will they be easier to drive than satellites with let's say 88 db ratings ?
Let me know your views/ suggestions. I will be happy to stand corrected on the above.
Based on these I arrived at the following conclusion for my Wharfedale Diamond 220 speakers which carry a sensitivity of 86 db.
Disclaimer: I am a finance professional, hence it is likely that I misunderstood some point on ohms/ decibels/watts
Basic assumption: With1 watt the speaker produces 86 db sound at a distance of 1 meter. To increase sound by every 3 db I need to double the wattage.
Actual SPL: While watching a recent movie I was recording the sound level using a SPL app on my phone. At a comfortable listening level in my Atmos HT, the peak was recorded at 97 db and the average SPL for about half an hour of viewing was recorded at about 85 db. So assuming worst case that I need 100 db of sound level all throughout (really loud), I will need about the following watts:
86db: 1 watt so
89 db: 2 watts
92 db: 4 watts
95 db: 8 watts
98 db: 16 watts
101 db: 32 watts
104 db: 64 watts
107 db: 128 watts
THX recommends 105 db for reference level movie watching but at that level it will get very uncomfortable. Hence to power ~ 98 db (peak) I will just need 16 watts per channel.
Now the catch is the 1 meter condition- that is I will need 16 watts to produce 98 db if I am seated at a distance of just 1 meter. Hence assuming that I am seated at 10 feet ( ~ 3 meters) I need to jump 2 levels and add another 6 db to the above calculation. Hence to listen at 98db (throughout) I will need about 64 watts per channel when seated at 3 meters from the speaker.
If the above is true then the following comes to light:
1. Most budget AVRs may not pump out 64 watts per channel in real world which is why they sound weak when pushed ? eg Marantz 1509 states 50 w per channel at 8 ohms with just 2 channels driven.
2. Always use efficient speakers (90 db +) which will reduce power requirement giving more headroom to the AVR/ amp
3. At times I have seen people recommending even stereo amps at 100 watts + per channel. However this may be too much since the requirement will depend upon the speaker efficiency and your distance from speaker and at what levels you listen to music.
4. I haven't measured but when listening to music the sound level would be 85- 90 db unless one is hosting a party ? In that case the wattage requirement could be even lower. This could be the reason why I find my 40 w per channel Rotel to be sound very powerful when powering the Diamond 220. Volume knob always at 9 o clock position or lower.
5. I am also assuming 32- 64 watts per channel would be the requirement to maintain 98-101 db continuously. Hence if this is only the peak requirement, then obviously the AVR doesn't need so much power across all channels at all times. Hence any AVR which claims 90-100 watts per channel with 2 channel driven at 8 ohms should be enough in most cases (given seating distance and speaker efficiency).
6. I always thought that small speakers must be easier to drive than large ones. Eg satellites must be the easiest compared to book shelves or floor standers. But I came across Klipsch floor standers with an astounding 98 db sensitivity. Will they be easier to drive than satellites with let's say 88 db ratings ?
Let me know your views/ suggestions. I will be happy to stand corrected on the above.
