Measure spl/speaker sensitivity

gasolin

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Marantz PM6005 has 45 watt rms in 8ohm, lets say 50 watt peak, that's 17 db, with 87 db sensitive speakers (i guess they measures it in pairs) in 8 ohm i should be able to play 104 db (actually a bit more since i only set the peak power to 50 watt).

Playing AC/DC Dirty Deeds Done Dirt Cheap from youtube, the volume at 10'o clock using Sound Meter and my samsung note 3.

2 feet away from my speakers i get around 75 db, my phone directly on the front grill i get 90 db. Shouldn't i be playing alot more then 2 watt,even more then 4 watt (in theory it should be 93db with 4 watt)

Why this huge difference in spl?

When they measure speaker sensitivity do they do it 2-4 feet away or a few inches from the speakers?

Why am i only playing 75/90db, it's pretty loud already, in fact so loud i can't imagine going from 90 db to 104db, (with my phone on the grill), since it must be insanly loud (have been to concerts with spl above 100db) and i imagine theres alot of distortion, although there shouldn't be any (atleast not much)

With earplugs (-22db) i couldn't get spl up to more then 92 db with my phone on the grill

Is the app limied to just a bit more then 90 db or is it the mic on my note 3 that limiteds the max spl i can measure?
 

gasolin

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spiny norman said:
Not quite.

For a start, speaker sensitivity is measured for a single speaker, at a distance of 1m, and you really need to think in terms of voltage, not watts.

The usual measurement of the sensitivity of a speaker is in dB, for an input of 2.83V (=1W), measured at one metre, but it could well be that your source isn't delivering anything like the 2V input your amp should be getting from a line source. In fact, given that you're feeding it from the headphone output of a your Note 3, which a spot of Googling suggests has a max output of a little under 12mW, you'll only get a tiny fraction of the level you might when using the amp with a standard CD player, which would have an output much nearer to that 2V standard.

So even with the amp delivering its gain and the volume cranked up, the chances are you're still only getting a fraction of a volt from your amp when fed in this way, and that's without taking into account how far down from a theoretical max level the YouTube content you're playing may be.

Only using my note 3 with sound meter to measure spl https://play.google.com/store/apps/details?id=kr.sira.sound&hl=da
 

spiny norman

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Not quite.

For a start, speaker sensitivity is measured for a single speaker, at a distance of 1m, and you really need to think in terms of voltage, not watts.

The usual measurement of the sensitivity of a speaker is in dB, for an input of 2.83V (=1W), measured at one metre, but it could well be that your source isn't delivering anything like the 2V input your amp should be getting from a line source. In fact, given that you're feeding it from the headphone output of your Note 3, which a spot of Googling suggests has a max output of a little under 12mW, you'll only get a tiny fraction of the level you might when using the amp with a standard CD player, which would have an output much nearer to that 2V standard.

So even with the amp delivering its gain and the volume cranked up, the chances are you're still only getting a fraction of a volt from your amp when fed in this way, and that's without taking into account how far down from a theoretical max level the YouTube content you're playing may be.
 

spiny norman

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gasolin said:
Only using my note 3 with sound meter to measure spl https://play.google.com/store/apps/details?id=kr.sira.sound&hl=da

Ah, I thought you said

'Playing AC/DC Dirty Deeds Done Dirt Cheap from youtube, the volume at 10'o clock using Sound Meter and my samsung note 3.'

but the point remains that the output from your computer via the Dragonfly is likely to be somewhat less than from a CD player. If you want to do this kind of measurement, you really need test-tones at 0dB, and to calibrate the source to ensure you're getting a 2V input into the amp. After all, with a lower input level, there's only so much the amp's gain can do.

Alternatively you need to get a voltmeter and measure the output at the amp's speaker terminals to ensure you're getting that nominal 2.83V output, at which point your speakers should be delivering something like their stated SPL when measured at 1m (allowing for some 'spin factor' in the way the specs are given).
 

Blacksabbath25

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I know with home cinema you have to sit and measure the sound levels were you sit and watch the films so would have thought music is the same . But measure the sound with a proper sound meter as the app sound meters are not that reliable . I did see a YouTube video were it was explained the man said that a amp that has a big power supply would normal be more powerful because he said it's like a water hose a fireman hose would be more powerful then a garden hose were not much water can come out but with the firemans hose more power comes out of it with a big power supply and how the amp handles this into watts .
 

gasolin

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I am following ´New record day on youtube and he often uses a spl meter to test spl.

I think his goal is above 90 db when he plays loud music, he often reaces levels beound 90 db and sometime over 100db

I know a phone isn't as accurate as a spl meter but wanted to test my system, but only got 92 db (weather it was 92db or louder do to app/mic limiteds i don't know, all i know was, it was loud) with my phone on the front grill and 75 db 2 feet away, volume was fare beyond 12'o clock(didn' noticed any distortion those 10 mabye 15 sec it lasted trying to reach top speed without distortion), i wonder if it's my phone (mic) app or both that is the limited, since i should be able to play above 100db but couldn't

https://youtu.be/NrCTPlBkMio?t=6m10s (i know he might have a bit more power then i have)
 

Covenanter

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It is perhaps not widely appreciated that the volume control does not increase amplification, it attenuates the input. So, for example, if your input signal is 1 volt at its lowest level almost nothing gets fed into the amplifier and at the higest level all of your signal gets fed in.

What this means is that a source that produces 2 volts will sound roughly twice as loud as one that produces 1 volt at any particular setting of the volume control.

Chris
 

davedotco

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Back in the day we used to measure speaker sensitivity outdoors, ie in free space, no reflections.

For different purposes we might use pink noise or sinewaves but always 2.83 volts, which as spiney almost said is 1 watt into 8 ohm. Measurement is carried out at 1 meter, one speaker to give the nominal sensitivity, ie 87 dB/watt/meter. The figure quoted by manufacturers is often 'massaged' to give the highest possible figure, most manufacturers do this so are nothing more than a rough guide.

The sensitivity in room is something else entirely, all kinds of things affect the result, such as distance to the listening position, reflections in the room (room gain), reverberation time, loudspeaker dispersion and half a dozen other things I have propably forgotten.

Simplest way to get a meaningful result is a decent SPL meter at the listening position and 2.83 volts, measured with a voltmeter at the speaker terminals. This will give you a benchmark figure to base your calculations on.

BTW. Covenanter is incorrect. Doubling the input voltage may be +6dB volts but gives just +3dB power, so a modest increase in volume, nothing like twice as loud.
 

Rethep

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I always thought that the efficiency of a speaker (in dB) is measured at 1000 Hz, 1 m, 2,83 V (in 8 ohms!), in an acoustically dead room!

I' m not sure about the freq though.
 

Covenanter

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davedotco said:
Back in the day we used to measure speaker sensitivity outdoors, ie in free space, no reflections.

For different purposes we might use pink noise or sinewaves but always 2.83 volts, which as spiney almost said is 1 watt into 8 ohm. Measurement is carried out at 1 meter, one speaker to give the nominal sensitivity, ie 87 dB/watt/meter. The figure quoted by manufacturers is often 'massaged' to give the highest possible figure, most manufacturers do this so are nothing more than a rough guide.

The sensitivity in room is something else entirely, all kinds of things affect the result, such as distance to the listening position, reflections in the room (room gain), reverberation time, loudspeaker dispersion and half a dozen other things I have propably forgotten.

Simplest way to get a meaningful result is a decent SPL meter at the listening position and 2.83 volts, measured with a voltmeter at the speaker terminals. This will give you a benchmark figure to base your calculations on.

BTW. Covenanter is incorrect. Doubling the input voltage may be +6dB volts but gives just +3dB power, so a modest increase in volume, nothing like twice as loud.

You are correct I'd forgotten the difference between sound power and electrical power.

Chris
 

davedotco

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Rethep said:
I always thought that the efficiency of a speaker (in dB) is measured at 1000 Hz, 1 m, 2,83 V (in 8 ohms!), in an acoustically dead room!

I' m not sure about the freq though.

There is no such thing as an acoustically dead room.

A large anechoic chamber is the nearest and to come close they have to be very large and very expensive. We did it in the open air, the speaker is pointed upwards, flush mounted on a platforn some feet of the ground, so no reflections at all. Some manufacturers do use anechoic chambers, others I think just guess.

You can use pink noise, in my view, best for a complete speaker system or specific frequencies or swept frequencies, whatever. The industry is not consistent in this.
 

gasolin

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Rethep said:
I always thought that the efficiency of a speaker (in dB) is measured at 1000 Hz, 1 m, 2,83 V (in 8 ohms!), in an acoustically dead room!

I' m not sure about the freq though.

That is what som amp specs are in, 1khz often giver more watt then 20-20.000hz and therefor some people may think it's a very powerfull amp
 

ID.

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Rethep said:
I always thought that the efficiency of a speaker (in dB) is measured at 1000 Hz, 1 m, 2,83 V (in 8 ohms!), in an acoustically dead room!

I' m not sure about the freq though.

No idea what is normal, but this is what is given for my Adams (active speakers, so purely dB measurements rather than any discussion of sensitivity).
Max SPL with sine wave acoustic 100Hz to 3kHz at 1m≥106 dBMax SPL per pair at 1m≥114 dB
As far as amplification goes, apparently 150w per channel (it gives the peak output, but I'm ignoring that).
 

davedotco

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ID. said:
Rethep said:
I always thought that the efficiency of a speaker (in dB) is measured at 1000 Hz, 1 m, 2,83 V (in 8 ohms!), in an acoustically dead room!

I' m not sure about the freq though.

No idea what is normal, but this is what is given for my Adams (active speakers, so purely dB measurements rather than any discussion of sensitivity).

Max SPL with sine wave acoustic 100Hz to 3kHz at 1m ≥106 dB Max SPL per pair at 1m ≥114 dB

As far as amplification goes, apparently 150w per channel (it gives the peak output, but I'm ignoring that).

As I said earlier, sensitivity and max output (SPL) are all something of a mish-mash. In hi-fi the sensitivity, dB/meter/watt seems to be the most important, in the pro and prosumer world maximum output (SPL) is considered important. In pretty much all cases the figures are, shall we say 'optimistic' but since every one does it, they are roughly comparble.

I'm interpreting a bit here, but I would say that the Adam A7x you quoted will produce a maximum of 106dB continuous (music or 'shaped' 100-3000Hz signal approximating to music) with a capability of 114dB on peaks.

Knowing the speaker, I would say that is what they are getting at.
 

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