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In Reply to: RE: speaker listening levels. posted by 6bq5 on June 15, 2017 at 16:34:04
I would be interested in knowing a mathematical formula one could plug in speaker efficiency (the 1 watt db rating..) and get the result in watts of power for the requested dB 'in room' (perhaps needing a standard distance from speaker..)
I KNOW such a formula would be very loose with an estimate..
But even a wide variation from reality would at least give an idea of the power required.
Follow Ups:
hahax said " Doubling that [distance] reduces the level by 1/4 on most speakers"
Yes, but only if they are in an anechoic chamber or outdoors.
If they are in a room then the SPL will remain constant with distance once the listener is far enough back to be in the reverberate field.
In a "typical" living room this happens at about one meter (how convenient).
A quote from Paul Jappa,
"The calculator you linked assumes you are listening outdoors, or at least in a concert-hall or larger space.
In the average living room using average speakers, the sound level does not reduce with distance once you are past about 1 meter. This is because the reverberant field in the room has statistically uniform loudness; only the direct field drops off with distance. At about 1 meter the direct field is the same loudness as the reverberant field; beyond that point the reverberant field dominates the perceived loudness.
This has of course some variation, depending on the room's size, sound absorbing contents, and speaker directivity index. The subject of room acoustics is fairly complex and challenging, but quite rewarding to study if you are a music enthusiast. But until you are ready to do a full study of your environment, the 1-meter rule is a good place to start. Just re-do the calculation with 1.0 meters distance instead of 4.5 meters. The difference will be startling, around 1/20th as much power is needed."
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The factors are:
type of speaker-
-Planar - flat panel that is LARGE at lest 4 x 7 feet per radiator
-Line source
-dynamic - the speaker that most of us have
> > the planar speaker will have ~0dB fall-off as the distance is doubled
> > the line-source will drop-off at ~3dB as the distance is doubled
> > Dynamic will drop-off (level/volume/Loudness) at ~6dB as the distance is doubled.
Listening distance from the speaker
Your measurement - Peak or Average
If it is peak - then you are going to calculate the max power that you are delivering to you speaker to get the dB reading (at a given distance)-
If, on the other hand, you are measuring average, then you may want to look at how much headroom you want/need....
Thus, if we walk down this path a bit-
let's assume Dynamic speaker - @ 88dB efficiency:
at one meter at 2 meters at 4 meters
88dB = 1 watt: @ dbl'd distance: 82dB=1watt Now 76dB=1 watt
Listening level
96 = +8dB ~ 6.3Watts 96dB= +14dB ~ 25 watts 96dB = +20dB ~ 100W
so - where are you sitting?
and How Loud is it?
Happy Listening
"Your measurement - Peak or Average"I have dynamic speakers and what I do for measurements is walk around the room and listen.
The perceived SPL doesn't change except in a couple of spots where the bass stacks up.
If the SPL was falling at 6db for every doubling of distance don't you think I would notice?
If I move back as to double the distance twice that would be 12db.
I have a volume control with 2db steps. 12db would be 6 clicks on my volume control. 6 clicks is huge. Nothing like that happens when I move away as to double the distance twice.
"people listen to speaker in reverbrant rooms" and "above 500Hz or so the SPL at any point in the room was the same"
Edgar Villchur
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 06/16/17
Point taken, but I think 1 meter is probably not the right number for most rooms and most speakers, especially larger rooms or if the speakers have controlled directivity.
In my smaller room downstairs the volume level continues to drop as you move back, up to maybe 2m or so, and the direct sound still seems to dominate at the listening position which is 8 ft away. I do have acoustic treatment though. In my open plan living room, it's further.
"especially larger rooms or if the speakers have controlled directivity.
"
Agreed.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
There are a lot of SPL calculators around the web. Here's one:
You can 'back calculate' the power being used-
Need to know type of speaker - line source, planar, dynamic...
And listening distance from speaker-
Happy Listening
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