REW first scan - mystery

[staticV3]

Q. What test noise loudness is needed for REW measurement?

There is no fixed loudness requirement for REW measurements.

As long as SNR is sufficient, you can measure at 10dB SPL or 140.

 

[Sokel]

The SMSL M8 DAC has replaced SMSL SU-9 DAC.
The signal is via Airplay* > WiiM mini > Optical > SMSL M8 > ICE 1200 amplifier > Revel F206.
I did not get the result I expected.


REW says signal too low (see screenshot).
It sounds quite loud to me though, via speaker.
I checked the loudness with my iPhone (mic towards speaker) to see if it was similar to the UMIK-1 reading in REW for level. Screen shot attached.
I pressed 'Measure' in REW anyway.
I have made a measurement at 0º Left speaker.

Q. What test noise loudness is needed for REW measurement?

I can go a bit louder during the day if I'm nearly at measurement level - I'm in UK terraced house - so in the evening I have levels lower for neighbours.

I guess the SU-9 DAC is ok, as it has been swapped with M8 and a similar result showing.


*missing a USB 2.0 > C adaptor at moment

Out of curiosity, can you test with no calibration file at all?
Just go to preferences> cal files > Mic cal files, delete it (x) and test it like this, so to rule out any text misread, etc.

 

[1066]

Out of curiosity, can you test with no calibration file at all?
Just go to preferences> cal files > Mic cal files, delete it (x) and test it like this, so to rule out any text misread, etc.

I will try that tomorrow Sokel - thank you.

 

[1066]

For some reason cannot get Macbook 2019 to directly recognise SMSL M8 from via USB + USB-C adaptor.
Otherwise would have used USB to connect to DAC rather than Airplay-WiiM-optical.

These results without UMIK-1 calibration file look very similar to the previous readings?

 

[staticV3]

For some reason cannot get Macbook 2019 to directly recognise SMSL M8 from via USB + USB-C adaptor.
Otherwise would have used USB to connect to DAC rather than Airplay-WiiM-optical.

These results without UMIK-1 calibration file look very similar to the previous readings?

Something is still amiss.

Using the M8, do you still hear the same treble roll-off as you did before?

So essentially no output above ~8kHz?

 

[1066]

My ears are ringing now - is all these high test tones next to speaker

This 9k frequency was very feint - but could be heard if I turned my head a bit.

 

[1066]

I ordered a 3.5mm jack to 2 XLR cable which has arrived.

Have plugged Macbook 3.5mm headphone output directly into the Nord ICE1200 to measure REW sweep:

 

[staticV3]

I ordered a 3.5mm jack to 2 XLR cable which has arrived.

Have plugged Macbook 3.5mm headphone output directly into the Nord ICE1200 to measure REW sweep:

Bingo!

That confirms the Nord, Revel, UMIK, and REW settings are all fine.

But something weird is happening when using external DACs.

 

[AnalogSteph]

Looks about as messy as you'd expect from a single point measurement with no smoothing and default window size, but fundamentally fine.

At this point you could start playing with the MMM (which should yield some more confidence-inspiring results) and derive some EQ presets.

 

[1066]

Bingo!

That confirms the Nord, Revel, UMIK, and REW settings are all fine.

But something weird is happening when using external DACs.

Yes.

What is going on with the dacs?

I thought it might be the WiiM optical out but I’m sure I tested the smsl su-9 via usb cable from MacBook, eliminating AirPlay/WiiM.

The cliff edge in the REW response was still there.

(Head in hands with ears still ringing).

 

[1066]

Looks about as messy as you'd expect from a single point measurement with no smoothing and default window size, but fundamentally fine.

At this point you could start playing with the MMM (which should yield some more confidence-inspiring results) and derive some EQ presets.

Yes that would be great to be at that point. I don’t know what’s up with the DACs though.

 

[Keith_W]

Your ears shouldn't be ringing when you take measurements. If it does, you are measuring too loud. DON'T measure loudspeakers too loud, because you push them into nonlinear behaviour - compression, distortion, etc. Measure at a normal listening level. If you are concerned about signal to noise ratio, take a longer sweep.

 

[1066]

Good to know.

Before UMIK-1 I wouldn’t know what spl a sound was.

On REW it says:

“REW measurements are usually made at a level of about 75 dB SPL”.

I’m not sure what distance that is at. From usual listening position I guess.

I never managed to get to 75spl on the REW reading. 69/70 was most I got to on the REW noise generator at 2 metres.

I think it was more that 8,000-9,000Hz makes my ears whistle and I was one foot from tweeter.

How does one make a longer sweep in REW?
Is it a more accurate?

 

[Keith_W]

To determine absolute SPL you need an SPL meter. All measurement microphones including the UMIK-1 can only determine relative SPL. For most purposes in our hobby, relative SPL is enough, so I do not suggest that people buy an SPL meter.

If you want a ghetto SPL meter, try this - smoke alarms are calibrated to produce 85dB at 1m. Place your mic 1m away from a smoke alarm and press the "TEST" button whilst wearing hearing protection! Adjust REW's gain settings until it reads 85dB.

To make a longer sweep, choose 1M, 2M, or 4M. A longer sweep gives you a better signal to noise ratio without having to raise the volume. You may not even need that better SNR, it all depends on what you want to do with the measurement. But the one thing you should not do is to measure so loud that your ears hurt. As mentioned, the measurement is likely to be inaccurate, it is bad for your loudspeakers, it is bad for your ears. Measure at your normal listening level.

 

[staticV3]

All measurement microphones including the UMIK-1 can only determine relative SPL.

The UMIK-1 can determine absolute SPL, since it is SPL calibrated at the factory.

Simply load the unique calibration file into REW and the SPL Meter will display accurate SPL readings.

 

[SashaR]

I would be very grateful to all participants for their opinion regarding the serviceability/malfunction of my UMIK-1 (I have already sent it for replacement and I would like to know whether my newbie's decision was wrong). Pay attention to the fourth pic!

 

[kemmler3D]

I would be very grateful to all participants for their opinion regarding the serviceability/malfunction of my UMIK-1 (I have already sent it for replacement and I would like to know whether my newbie's decision was wrong). Pay attention to the fourth pic!

In the 4th pic, are these measurements from the same spot and same sweep? If so it does look like the UMIK was glitching out.

 

[antcollinet]

ears still ringing

If your ears are genuinely ringing, you are damaging your hearing. Please wear some ear protection.

In fact, wear it anyway if you are running test tones to speakers. Far too easy to accidentally send full power high frequency and kill your hearing altogether.

 

[SashaR]

In the 4th pic, are these measurements from the same spot and same sweep? If so it does look like the UMIK was glitching out.

Thank you!!!
ALL the graphs was produced in the SAME and STABLE environment.
Of course, on the 4th pic's chart the sweeps are placed at different levels of the chart.

 

[Keith_W]

Thank you!!!
ALL the graphs was produced in the SAME and STABLE environment.
Of course, on the 4th pic's chart the sweeps are placed at different levels of the chart.

I highly doubt that.

All the graphs are labelled "L+R" indicating you swept both speakers together.

The two graphs at the bottom (blue and orange) show comb filtering of the upper frequencies. This suggests that the polarity was inverted in one of the speakers. A faulty microphone does not produce comb filtering. If you look very carefully, you can see that in the green graph, the tweeter dropped in level. Interestingly, the comb filtering appears at the same frequencies upwards. This makes me think that you disconnected the cables to the tweeter, took the green measurement, and reconnected them with the wrong polarity. Then you took the two measurements at the bottom.

These are not the same measurements, even if you staggered the level. Read the REW Help thread, and make sure you are taking measurements properly. Then take another set of measurements and post them.