How to Estimate DB At 1 Meter By Volume Knob for Active Speakers?

[jdjung]

So, I read all the reviews and see distortion, compression and noise varies based on the loudness in db at 1 meter and see people saying I listen to my speakers at "so and so" db levels. Without an SPL meter at 1 meter in front of your speakers how are people determining this?

I own a pair of KEF LS50 Wireless 2 would I simply divide the highest rated db levels of the speakers (108db) by 100 (the total increments of volume that the KEF LS50 Wireless 2 have)? I heard most volume is actually exponential, so how would I figure this out? I generally listen to my speakers between 40-50 at 13 feet, what would the estimated DB be at this volume at 1 meter? Also, is AMP noise constant at different volume levels, meaning that listening to higher levels would reduce distortion till the amp clips and/or the drivers distort? What's the sweet spot?

 

[sigbergaudio]

So, I read all the reviews and see distortion, compression and noise varies based on the loudness in db at 1 meter and see people saying I listen to my speakers at "so and so" db levels. Without an SPL meter at 1 meter in front of your speakers how are people determining this?

I own a pair of KEF LS50 Wireless 2 would I simply divide the highest rated db levels of the speakers (108db) by 100 (the total increments of volume that the KEF LS50 Wireless 2 have)? I heard most volume is actually exponential, so how would I figure this out? I generally listen to my speakers between 40-50 at 13 feet, what would the estimated DB be at this volume at 1 meter? Also, is AMP noise constant at different volume levels, meaning that listening to higher levels would reduce distortion till the amp clips and/or the drivers distort? What's the sweet spot?

People generally don't determine it without an spl meter. But you likely have one in your hand right now (your phone).

 

[jdjung]

People generally don't determine it without an spl meter. But you likely have one in your hand right now (your phone).

I actually do have a RadioShack SPL meter someplace in storage and the Minidsp UMIK-1 and trying to learn how to use REW. What settings on REW do I need to measure the SPL accurately, because I know you can increase gain in the software. This also confuses me because the computer analog levels using the analog output (headphone jack) to the KEF Wireless 2 will also determine how loud you will be playing the speakers in REW. Do I MAX out the output in REW? I'm using a laptop vs my desktop which has optical/coaxial/balanced line level (4 volts at line level for the Antelope Audio Zen Q), but I would need to buy some seriously long cables to hook it up to my desktop.

 

[MrSoul4470]

But you likely have one in your hand right now (your phone).

Using a smartphone is usually no better than guessing. Most of those apps are useless unless you can choose the specific smartphone you use.

 

[jdjung]

This is what's frustrating, if you have several inputs being used in the KEF Wireless 2, optical/wifi/Bluetooth/HDMI/analog input, I doubt the input volume is all the same especially for the analog input. I don't even know if the KEF Wireless 2 analog input is for headphone or line level, given it's a regular 3.5 mm stereo jack.

 

[Blumlein 88]

Using a smartphone is usually no better than guessing. Most of those apps are useless unless you can choose the specific smartphone you use.

No, I don't think so. Some are better than others. I have an old RS meter, REW via Umik1, and a phone. Maybe when I get a chance I'll do a comparison of those with a few apps on an Android phone.

 

[nerdstrike]

As far as I am concerned the only thing you can do is calibrate and go from there. Anything else is guessing.

If you could get voltage probes to the amp then you might be able to estimate based on sensitivity... Not easy with an active package. Or maybe bounce a laser off the cone... Much cheaper to get a sound meter!

 

[jdjung]

I think the only real way to measure it is to look at the spec sheet, see the power output at the amp output, do some math and figure out the DB value if you're using a preamp to your amp. Line levels are not constant with preamps and with active speakers, what the heck are we supposed to do with different sources coming in? I other words to get to 96 DB, if your preamp is hot, then isn't it easier to get to 96 DB?

 

[MaxwellsEq]

Your SPL meter should be set to slow and C-Weighted. If you are calibrating your setup, use pink noise at -20. Studio monitoring is in the mid 80s, domestically that's loud, so something around 78 should be suitable. It's worth googling the Bob Katz method.

 

[jdjung]

Your SPL meter should be set to slow and C-Weighted. If you are calibrating your setup, use pink noise at -20. Studio monitoring is in the mid 80s, domestically that's loud, so something around 78 should be suitable. It's worth googling the Bob Katz method.

This is the silly thing I discovered when using the UMIK 1, it suggest going to 75 DB for in room measurements. When testing, the volume on the KEFs they were around 75 out of 100 clicks to get there. It was louder than I ever listened to them. I listen between 40-50 clicks out of 100 and in the morning 30-40 at 13 feet through WiFi using Roon. Why are we testing speakers at 96db and 86db? I can't imagine most people listen to speakers above 60db. Is it just marketing to get better noise measurements? I know we perceived volume doubling exponentially as you go up in db but are volume pots linear on most amps?

 

[MaxwellsEq]

The volume control position is totally, completely,, 100% useless as a guide for knowing the in-room SPL. Unfortunately, you are wasting your time trying to make this approach work.

The SPL depends on speaker efficiency, amplifier gain, the "log" of the volume control, the sensitivity of the inputs, the output voltage of source devices. Change any of these things, and the volume pot will be in a different place. This is why dB scales on HiFi volume control or amplifier VU meters are a joke.

 

[jdjung]

The volume control position is totally, completely,, 100% useless as a guide for knowing the in-room SPL. Unfortunately, you are wasting your time trying to make this approach work.

The SPL depends on speaker efficiency, amplifier gain, the "log" of the volume control, the sensitivity of the inputs, the output voltage of source devices. Change any of these things, and the volume pot will be in a different place. This is why dB scales on HiFi volume control or amplifier VU meters are a joke.

I'm never going to find my Radio Shack SPL meter it's in storage in a box who knows where. What do you suggest as a good SPL meter?

 

[sergeauckland]

Buy another Radio Shack analogue meter on eBay or wherever. I think it'll be the cheapest way to get a reasonably accurate meter. I've checked mine against a high-end lab instrument and on white noise it was within 1dB of the lab unit, so good enough for Jazz. Those on a 'phone will probably be a lot worse than that unless carefully calibrated, even assuming the app allows that.

S

 

[MaxwellsEq]

I'm never going to find my Radio Shack SPL meter it's in storage in a box who knows where. What do you suggest as a good SPL meter?

If you have an iPhone, search NIOSH. I compared the recommended free tool against my calibrated SPL meter and it was pretty close for everything above 100Hz. Otherwise, there are some reasonable SPL meters on Amazon, but check they support C weighting and Slow, the cheapest don't.

 

[Berwhale]

Why are we testing speakers at 96db and 86db?

My understanding is that this is to increase the signal to noise ratio (i.e. the amplitude of the test tone to the amplitude of background noise of your room) and therefore the accuracy of the results.

 

[sigbergaudio]

Using a smartphone is usually no better than guessing. Most of those apps are useless unless you can choose the specific smartphone you use.

I think that is exaggerated, but I see how it will likely be deviations on Android. On IOS on the other hand it is relatively accurate. Not for a scientific study, but certainly for what the OP needs (based on my understanding).

 

[Sokel]

Find your SPL meter and calibrate REW against it (it's really simple,use the SPL tab,it explains everything).
You can then use the SPL tab and the logger there to see your actual SPL including average,maximum and peaks.

 

[sigbergaudio]

I actually do have a RadioShack SPL meter someplace in storage and the Minidsp UMIK-1 and trying to learn how to use REW. What settings on REW do I need to measure the SPL accurately, because I know you can increase gain in the software. This also confuses me because the computer analog levels using the analog output (headphone jack) to the KEF Wireless 2 will also determine how loud you will be playing the speakers in REW. Do I MAX out the output in REW? I'm using a laptop vs my desktop which has optical/coaxial/balanced line level (4 volts at line level for the Antelope Audio Zen Q), but I would need to buy some seriously long cables to hook it up to my desktop.

What are you looking to figure out specifically? You don't need REW to measure SPL.

 

[wwenze]

That's why UMIK-1 is useful compared to normal analogue mics... just plug it in, load the calibration file in REW, there, SPL-calibrated.

 

[jdjung]

What are you looking to figure out specifically? You don't need REW to measure SPL.

I guess my question specifically after giving this a lot of thought are the following;

1. What settings I should use for accurate SPL readings in REW using the UMIK-1 with calibration file?
2. Is there a math equation I could use and what is it if I'm outside of an SPL meter when listening to speakers outside of my home such as a store and friends house? I had believed most potentiometers are either linear or logarithmic.
3. Given that most tests are at 1 meter from 1 speaker vs 2 speakers, how much more DB does 2 speakers vs 1 make when determining loudness when making a speaker buying decision?
4. Given that most tests are at 1 meter, what difference in db does distance make as you go past 1 meter?
5. When looking at the optimal loudness for volume, does noise generally go up at lower volume levels for amp noise but goes down for speaker noise?
6. If using a physical preamp or streaming wirelessly (Bluetooth and wifi), does noise generally stays constant at the preamp to amp stage. If this is true, shouldn't we max out our preamp or streaming minus a few DB to stop clipping at the DAC or preamp input, to reduce noise at speaker output? In other words nearly max out Bluetooth or preamp analog input signal to get the least amount of noise to the speaker?
7. Does speaker cabinet resonance go down as volume goes down or is it linear or logarithmic or just random based on volume level?