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Sensitivity (2.83V @ 1m): 92dB?


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#1 of 14 OFFLINE   BrianHo

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Posted May 13 2003 - 10:48 AM

Is this good? What does it mean in performance?

Brian

#2 of 14 OFFLINE   Geoff L

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Posted May 13 2003 - 11:35 AM

I give, you win....Posted Image Posted Image Posted Image Posted Image Posted Image
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#3 of 14 OFFLINE   AlbertA

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Posted May 13 2003 - 11:46 AM

It means that with 1 watt of power at a distance of 1 m you will get 92 dB of sound pressure level.

For every 3dB of SPL increase you will need twice the power. For example, if you want 95dB SPL you'll need 2 Watts. for 98dB, 4 Watts, 101 dB 16 Watts, 104dB 32 Watts and so on.

So, the higher the sensitivity the better, since you don't need to use a lot of power to drive your speakers and leaves headroom for those reference level peaks.
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#4 of 14 OFFLINE   Michael R Price

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Posted May 13 2003 - 12:20 PM

It might be deceiving, especially if that's an "in room" sensitivity spec or the speakers are lower than 8 ohms, since calculating levels from that spec means you assume your amplifier is a perfect voltage source. What speakers in particular are you describing?

Otherwise, higher is better (and 92db is not bad at all). I think most conventional speakers are 83-90db, but some horns can be 100db and higher.

#5 of 14 OFFLINE   Danny Tse

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Posted May 13 2003 - 05:43 PM

The sensitivity doesn't mean anything in terms of performance. But it does give you an idea on what kind of power is needed to power them correctly. There are excellent speakers with high sensitivity, and there are excellent speakers with low sensitivity. Just remember a lot of things go into making a "system" sound good.
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#6 of 14 OFFLINE   John Kotches

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Posted May 14 2003 - 12:39 AM

AlbertA said:

Quote:
It means that with 1 watt of power at a distance of 1 m you will get 92 dB of sound pressure level.

Not quite. 2.83v into an 8 ohm load is 1w of power. 2.83v into a 4 ohm load is 2w of power.

So it depends on the impedance of the speaker.

Regards,
Surround Music Enthusiast / Curmudgeon in Training
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#7 of 14 OFFLINE   Dan Hine

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Posted May 14 2003 - 01:18 AM

Quote:
Not quite. 2.83v into an 8 ohm load is 1w of power. 2.83v into a 4 ohm load is 2w of power.


Alright John...I'm a tad confused. I have seen several companies list different efficiencies for 1w/1m and 2.83v/1m. And it's not close either (usually 3db or more difference). So how/why does one equal the other? Also, which spec should be the one considered when designing/simulating, etc...?

Thanks!

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#8 of 14 OFFLINE   BrianHo

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Posted May 14 2003 - 05:59 AM

I'm refering to JBL s312II speakers.

Thanks for the info even though it really confused me.

Brian

#9 of 14 OFFLINE   John Kotches

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Posted May 14 2003 - 06:12 AM

Dan,

I was taught that there are two germane (and relatively simple) equations for these calculations:

Ohm's law says V (Voltage) = I(Current)*R(Resistance(Impedance for our purposes)).

Power = V(Voltage) * I(Current)

Voltage(2.83v) is constant for our examples.

Solving to determine current with Ohm's law:
2.83 = x * 8
2.83/8 = x
x ~= .35A.

Then calculating power usage:
x = 2.83 * .35
x = 1 (watts)


When we talk about a 4 ohm speaker, we have
2.83 = x * 4
2.83/4 = x
x ~=.7A

Power usage in this case:
x = 2.83 * .7
x = 2 (watts)

The 3dB difference would directly equate to the difference in power applied, assuming the speakers rated impedance is 4 ohms.

There is no one spec to look at in this case which is more correct than another. Both xxdB/1w/1m and yydB/2.83v/1m describe the sensitivity. The first example is a little more straightforward.

I could be wrong, it's been way too long since I took the appropriate course.

Regards,
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#10 of 14 OFFLINE   Phil Iturralde

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Posted May 14 2003 - 06:24 AM

STUDIO™ SERIES – S312II / 3-Way, 12-Inch Floorstanding Speaker
• Impedance: 8 Ohms
• Sensitivity (2.83V @ 1m): 92dB - Measurement Standard used by the Speaker Manufactures for comparison of efficiency w/1 Power Watt vs. SPL (Sound-Pressure Level)

Excluding powered sub-woofers, speaker sensitivity ratings is your quick** starting point in determining how loud SPL vs. watts can deliver.

First the basic rules: (SPL = Sound Pressure Level)
1: It takes at least 3 dB of SPL for the human hearing to perceive an increase of loudness.
2: In terms of Power output vs. SPL, to achieve 3 dB increase of acoustic SPL requires doubling (x2) the REC/AMP Power.
=============================
Watts--SPL (dB)------SPL (dB)
1------86------------92
2------89------------95
4------92------------98
8------95------------101
16-----98------------104
32-----101-----------107
64-----104-----------110
128----107-----------113
=========================
Using 2 examples:
Column 1 = 86 dB sensitivity rated speakers using 1watt @ 1 meter
Column 2 = 92 dB sensitivity rated speakers using 1watt @ 1 meter


Based on 86 dB sensitivity, ... 64 watt output, you can achieve 104 dB SPL! (very loud!)

Based on 92 dB sensitivity, ... 64 watt output, you can achieve 110 dB SPL! (ear bleeding levels)

NOTE: Incorporating an Powered Sub-woofer will remove the AMP/REC requirements & strain.

-----

**To get an little more accurate SPL vs. 5 Speakers vs. Room, use C.M.Collins excellent SPL CALCULATOR

The JBL S312-II will be an easy load for just about any AV REC/AMP that you might want to use! Hope your neighbors aren't too close to your HT setup!!!

Phil
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#11 of 14 OFFLINE   Michael R Price

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Posted May 14 2003 - 12:06 PM

Brian,

Be careful though, because I remember James Johnson posting a review of the S312s saying they were fatiguing when played loud; they might be somewhat brighter speakers, like Klipsch. They'll go loud for sure, but it would help to listen to those speakers before buying them, so you're sure you like the sound.

#12 of 14 OFFLINE   John Kotches

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Posted May 14 2003 - 02:44 PM

Phil,

I don't know many people that listen in the nearfield at 1m.

Don't forget to adjust the SPLs for distance (and make an allowance for room reinforcement).

Regards,
Surround Music Enthusiast / Curmudgeon in Training
Opinions are my own, not representative of the publication I write for.

#13 of 14 OFFLINE   Phil Iturralde

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Posted May 15 2003 - 01:59 AM

Quote:
I don't know many people that listen in the nearfield at 1m.

The above Watts vs. SPL Chart is just a Quick Snap Shot value, ...

Quote:
...Don't forget to adjust the SPLs for distance ...

Which is why I recommend using C.M.Collins excellent SPL CALCULATOR (linked above in my original post), which you fill-in the following blanks:

Speaker Sensitivity: ______ dB SPL (1 W/1 M)

Amplifier Power: ... ______ Watts

Distance: .......... ______ feet

No. of Speakers: ... ______ usually 2, more for multi-channel

Speaker Placement (Choose 1):
.................... ______ Away from walls (or do not consider placement)
.................... ______ Near a wall (within 2 to 4 feet)
.................... ______ In a corner (within 18 to 24 inches)


======= Pressing "Calculate" provides:

RESULTS

_____ dB Gain from amplifier
_____ dB Loss due to dispersion (distance)
_____ dB Gain from sonic reinforcement (multi speakers)
_____ db Gain from placement (reinforcement from reflected sound)
_____ dB SPL at listening postion


=======

Phil
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#14 of 14 OFFLINE   hdnrs

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Posted June 17 2013 - 04:41 PM

Hi,
This thread has helped explain quite a bit about SPL, and I was hoping to get a little more info about how to use SPL. I am trying to create a portable sound system for various applications (battery powered, transportable via subway). I am concerned with size, weight, quality and throw (I hope that is the correct term). I have a variety of speaker / amp / battery solutions currently I am working on my subwoofer.

Since sound level is measured at a reference point and SPL is measured at the source I wanted to try and work out power consumption vs. relative sound levels in order to approximate how my power source (i.e. battery) requirements and volume levels. Currently I am focused on using this outdoors.

Here is what I suppose to be the relevant pieces of data
Sub SPL: (2.83v/1m): 85.6 db
Amp: 200 Watt RMS (Class D ~86% efficiency)

 

Here is the logic used

 

Input power (power draw @ battery) = output (amp) power / 86%

  -Output Power should be ~86% of the input power

 

db (@ source (i.e. 1m) ) increases 3 db for every 2 watts (output power) over SPL

  -For the data below I used an increase of 9 db for every 6 watts

 

DB @ distance = (DB@source - (20 * log(distanceFromSource/1m)))

  As taken from http://www.sengpiela...distancelaw.htm

 

Is this correct ? Thanks

 

Input Power  Output Power    db (@source)  @2m        @3m      @4m
(Watts)      Watts (86% eff)
1                      1                         85.6                79.6       76.1     73.6
8                      7                         94.6                88.6       85.1     82.6
15                     13                        103.6               97.6       94.1     91.6
22                     19                        112.6               106.6      103.1    100.6
29                     25                        121.6               115.6      112.1    109.6
36                     31                        130.6               124.6      121.1    118.6
43                     37                        139.6               133.6      130.1    127.6
50                     43                        148.6               142.6      139.1    136.6
57                     49                        157.6               151.6      148.1    145.6
64                     55                        166.6               160.6      157.1    154.6
71                     61                        175.6               169.6      166.1    163.6
78                     67                        184.6               178.6      175.1    172.6
85                     73                        193.6               187.6      184.1    181.6
92                     79                        202.6               196.6      193.1    190.6
99                     85                        211.6               205.6      202.1    199.6
106                    91                        220.6               214.6      211.1    208.6
113                    97                        229.6               223.6      220.1    217.6
120                    103                       238.6               232.6      229.1    226.6
127                    109                       247.6               241.6      238.1    235.6
134                    115                       256.6               250.6      247.1    244.6
141                    121                       265.6               259.6      256.1    253.6
148                    127                       274.6               268.6      265.1    262.6
155                    133                       283.6               277.6      274.1    271.6
162                    139                       292.6               286.6      283.1    280.6
169                    145                       301.6               295.6      292.1    289.6
176                    151                       310.6               304.6      301.1    298.6
183                    157                       319.6               313.6      310.1    307.6
190                    163                       328.6               322.6      319.1    316.6

 


Edited by hdnrs, June 17 2013 - 05:02 PM.



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