Dubious about SPL used by objective testers

[whazzup]

The reason they don't measure all speakers at the quieter level may be time/money related. I'm guessing they have to pay for time spent using NRC's anechoic chamber.

Second this. Just ask Amir how long it takes to complete one set of measurements at 1 db level (including logistics of handling different sized speakers, errors in measurements and redoing, etc), and multiply that by whatever number of db levels you think they should do. Complete sets because some other reader may complain if it's not.

Double / triple the cost/time? The magazine can afford that?

 

[Senior NEET Engineer]

96 dB SPL sine wave in room sounds extremely loud to me. Unlike audiophile music, the RMS will be close to the peak (only 3dB difference I think). Try listening to Death Magnetic at 93 dB SPL. Would you consider that normal listening level?

Not sure if 96 dB SPL anechoic would be louder. I'm guessing yes... most sound heard in room is reflected.

 

[hardisj]

96 dB SPL sine wave in room sounds extremely loud to me. Unlike audiophile music, the RMS will be close to the peak (only 3dB difference I think). Try listening to Death Magnetic at 93 dB SPL. Would you consider that normal listening level?

Not sure if 96 dB SPL anechoic would be louder. I'm guessing yes... most sound heard in room is reflected.

96dB is loud. I agree. However, don’t confuse 96dB at 1 meter with 96dB at the typical listening position. I polled a forum earlier this year and found most sit at about 3-4 meters from their speakers. Just using the standard 6dB/doubling distance that means the 96dB at 1 meter is equivalent to 84-87dB at typical listening distances. Which is also the volume level most said they listen at. I rarely go much lower than 80dB at my listening position. Usually in the mid 80’s and above.

 

[hardisj]

Second this. Just ask Amir how long it takes to complete one set of measurements at 1 db level (including logistics of handling different sized speakers, errors in measurements and redoing, etc), and multiply that by whatever number of db levels you think they should do. Complete sets because some other reader may complain if it's not.

Double / triple the cost/time? The magazine can afford that?

Or ask me.

For an HD sweep? Seconds.

For IMD or multitone max SPL testing? Longer. My max SPL testing typically takes 45 minutes to an hour for loudspeakers. That involves a one minute cool down between each multitone test.

But HD sweeps take literal seconds. They’re easy.

 

[whazzup]

Or ask me.

For an HD sweep? Seconds.

For IMD or multitone max SPL testing? Longer. My max SPL testing typically takes 45 minutes to an hour for loudspeakers. That involves a one minute cool down between each multitone test.

But HD sweeps take literal seconds. They’re easy.

Cool, maybe can answer the OP then, why not do HD sweeps at 2, or even more SPLs? Diminishing returns? Time/cost?

Is the NRC using Klippel too?

 

[hardisj]

Cool, maybe can answer the OP then, why not do HD sweeps at 2, or even more SPLs? Diminishing returns? Time/cost?

Is the NRC using Klippel too?

I do HD sweeps at 7 levels. I do 2.83v/1m and add the following:
-6dB
+6dB
+8dB
+10dB
+12dB
+14dB

Takes an extra minute of my time. Fully automated.

The other tests i mentioned above are what take longer.

 

[amirm]

Cool, maybe can answer the OP then, why not do HD sweeps at 2, or even more SPLs?

You are asking us or them? I run two already and for headphones started to run three. I can run more but it takes time to document and post them and people's eyes glaze over after some point with too many graphs. With two settings I put them side-by-side. With three can't do that.

As for NRC the fact that they change the level for different speakers bothers me as well. I picked 86 dBSPL which almost every speaker can do and then 96 dB which some can't. This way we always have one reference point that is common between all speakers.

 

[amirm]

Is the NRC using Klippel too?

Not the near-field scanner. They may use the baseline Klippel analyzer which is not the same thing.

 

[hardisj]

I can run more but it takes time to document and post them and people's eyes glaze over after some point with too many graphs.

This.

I chose to combine mine in to gif format for that reason. But no doubt if I posted them separately I would not post more than 3. It would just be one more thing to keep up with and probably wouldn’t be worth my time.

 

[hardisj]

Not the near-field scanner. They may use the baseline Klippel analyzer which is not the same thing.

Based on their graphs, I seriously doubt they even use the “regular” Klippel stuff.

 

[whazzup]

You are asking us or them? I run two already and for headphones started to run three. I can run more but it takes time to document and post them and people's eyes glaze over after some point with too many graphs. With two settings I put them side-by-side. With three can't do that.

As for NRC the fact that they change the level for different speakers bothers me as well. I picked 86 dBSPL which almost every speaker can do and then 96 dB which some can't. This way we always have one reference point that is common between all speakers.

To you and @hardisj. And both of you have already answered, thanks! So mainly more of editorial limitations.

 

[Dennis Murphy]

I can't help wondering whether the Soundstage statements that motivated this thread are simply incorrect. I've had my speakers measured by NRC (direct commission--not subordinate to a Sounstage review) and have had numerous discussions with the NRC engineer who's been doing these tests for years. The standard distortion test, to which all loudspeakers are subjected, is performed at two meters at 90 dB. If a speaker does particularly well on this test, such as was the case for, say, the JBL 890, a second test will be done at 95 dB, not 86 dB, also at 2 meters. See below.
As far as I know, all of the measurements on the Soundstage web site are the ones referenced in the magazine reviews, so I don't know where the 86 dB figure is coming from unless this is a very recent development that I haven't noticed yet.
THD+N @ 90dB, 50Hz - 10kHz (measured @ 2m)

THD+N @ 95dB, 50Hz - 10kHz (measured @ 2m)

 

[Sancus]

As far as I know, all of the measurements on the Soundstage web site are the ones referenced in the magazine reviews, so I don't know where the 86 dB figure is coming from unless this is a very recent development that I haven't noticed yet.

The thread's mostly been talking about 96dB, which is just 90db@2m converted to 1m.

For IMD or multitone max SPL testing? Longer. My max SPL testing typically takes 45 minutes to an hour for loudspeakers. That involves a one minute cool down between each multitone test.

BTW I really, really like your multitone testing.

 

[amirm]

As far as I know, all of the measurements on the Soundstage web site are the ones referenced in the magazine reviews, so I don't know where the 86 dB figure is coming from unless this is a very recent development that I haven't noticed yet.

86 dB is from me in my tests, not theirs. I worried that 96 dB (same as 90 dB at 2 meter at soundstage) was too high for some speakers. So just dropped it by 10 dB.

 

[Dennis Murphy]

The thread's mostly been talking about 96dB, which is just 90db@2m converted to 1m.

A good bit of the thread was criticism of testing at 86 dB, and that's the reference that started the thread off. I was just pointing out that the 8

86 dB is from me in my tests, not theirs. I worried that 96 dB (same as 90 dB at 2 meter at soundstage) was too high for some speakers. So just dropped it by 10 dB.

Right--I must have assumed that the lower level Soundstage was referring to was 86 dB. But for the record, the Soundstage description of the NRC testing procedure isn't correct. The starting point is 90 dB at two meters, or 96 dB at one meter. They don't test below that point to the best of my knowledge. But they do ramp things up to 95 dB at 2 meters if the speaker doesn't break a sweat at 90 dB.

 

[Senior NEET Engineer]

96dB is loud. I agree. However, don’t confuse 96dB at 1 meter with 96dB at the typical listening position. I polled a forum earlier this year and found most sit at about 3-4 meters from their speakers. Just using the standard 6dB/doubling distance that means the 96dB at 1 meter is equivalent to 84-87dB at typical listening distances. Which is also the volume level most said they listen at. I rarely go much lower than 80dB at my listening position. Usually in the mid 80’s and above.

No it is roughly -3 dB for each doubling of distance in typical living rooms. 96 dB SPL 1m free field will be higher than 96 dB SPL 1m in room. Half space is +3 dB. Two speakers is +6 dB. Sitting near rear wall is +3 dB.

 

[hardisj]

No it is roughly -3 dB for each doubling of distance in typical living rooms. 96 dB SPL 1m free field will be higher than 96 dB SPL 1m in room. Half space is +3 dB. Two speakers is +6 dB. Sitting near rear wall is +3 dB.

But you've already gained the +3dB once you put it in to a room. So when you move twice the distance away from the speaker, you still lose 6dB. You don't get to keep adding 3dB because the room has already been factored in at the beginning.

Example: Start with 96dB @ 1m anechoic. In a room near a wall it's closer to 99dB. Now move 2 meters away and the SPL is roughly 6dB down or 93dB in-room. At 4 meters it's 87dB.

So, like I said, if you take the 96dB anechoic then that's closer to 84-87dB at typical listening distance (anechoic). Add a few dB for room gain, sure. But the difference between 1 meter and typical listening distance of 3-4 meters is -9 to -12dB. That's why a 96dB @ 1m output measurement isn't over-reaching in loudness levels; it's right in the sweet spot where I find most listen once you factor in how far their MLP is from the speakers.

Now, if we want to add the additional speakers and all that... sure... that is correct. I still contend 96dB is a good number to test a single loudspeaker with assuming it can handle that. In one of my recent drive unit tests I maxed out at 95dB because the sensitivity of the DUT was ~84dB on average and I limit my IMD testing to about +10dB (iirc).

At this point, you and I may be "arguing" the same thing. I just want to be clear for others who may read that this is how the math works.

Though, I still do my testing at 7 different levels ranging from the standard 2.83v/1m to -6dB up to +14dB/1m to try to make sure I cover a wide range of output levels.


Edit: I use this site as a sanity check for in-room SPL levels at varying distances. Love this site:
https://myhometheater.homestead.com/splcalculator.html

 

[NTK]

This is the method ANSI/CTA-2034-A uses in its in-room SPL estimation. The standard uses a listening distance of 4 m (13 ft), assume 2 channels of uncorrelated signal (+3 dB) and room gain of +6 dB (3 dB higher than the calculator Erin linked to):

CTA-2034A also provide adjustment guidance. Note that the adjustments are based on the listening level category. For example, if the speakers are rated for listening level "Loud" using the formula above, but the room is large (≥ 600 ft²) with normal furnishing, they will be derated 1 step to "Moderate".

 

[hardisj]

This is the method ANSI/CTA-2034-A uses in its in-room SPL estimation. The standard uses a listening distance of 4 m (13 ft), assume 2 channels of uncorrelated signal (+3 dB) and room gain of +6 dB (3 dB higher than the calculator Erin linked to):

View attachment 100671

Good stuff. I remember reading that and thinking I need to use that standard but honestly forgot all about it. I need to try to remember using this again. Though, TBH, I'm not sure how useful it'll be for most average consumers... but can't hurt to use it. Just gotta find the time.

Interesting they use uncorrelated signal. Wonder why.... what's wrong with using correlated (other than it changing their gain value).

 

[NTK]

Good stuff. I remember reading that and thinking I need to use that standard but honestly forgot all about it. I need to try to remember using this again. Though, TBH, I'm not sure how useful it'll be for most average consumers... but can't hurt to use it. Just gotta find the time.

Interesting they use uncorrelated signal. Wonder why.... what's wrong with using correlated (other than it changing their gain value).

I think the sound from the speakers above the (mono) bass frequencies are probably closer to uncorrelated than correlated.