REW first scan - mystery

[1066]

I hope this is going in the newbie section.
Please move if it appears somewhere else.
Hoping there is some simple positive advice.

I have seen much mention of REW/UMIK-1 and thought I would see if any simple improving tweaks could be made to the sound, possibly with WiiM PEQ which is all I have.

So bought a UMIK-1 - a mic stand and tried REW software last night.

I got this graph and am puzzled. Measured at 90º orientation with calibration file for that orientation.
Although graph is showing like it sounds, like a partially blocked ear.

1. What could it be?

What next:

1. Is it possible to measure the DAC balanced output voltage on right channel with a multimeter and an iPhone sign wave generator via Airplay to narrow down which item is causing the frequency drop-off?
2. Are the pins in the screenshot the correct ones to use?
3. I would attach the .mdat file but the web CMS doesn't seem to allow it.
   
   Thanks
   

 

[Keith_W]

Welcome to ASR. Please read this thread. To attach a .MDAT, you need to zip it up first.

What is interesting is that you said that the measurement seems to reflect what you hear, as if the high frequencies are missing? I suggest you try the following:

- Check your REW settings and make sure you have set the sweep to run from 20Hz to 20kHz. You never know.
- Use REW's generator to play test tones through both speakers. No need to measure, just listen to the test tones. If you can hear test tones above 5kHz, that confirms that your speakers are working and there is something awry with the measurement.
- Check if the problem occurs with both speakers. If it's only one speaker, it is possible that the tweeter has gone bust / cable to the tweeter from the crossover is disconnected or something like that.

Finally, please detail what you used to take the measurement. UMIK-1 into laptop. How did you send the sound to the speakers?

 

[antcollinet]

Welcome to ASR. Please read this thread. To attach a .MDAT, you need to zip it up first.

What is interesting is that you said that the measurement seems to reflect what you hear, as if the high frequencies are missing? I suggest you try the following:

- Check your REW settings and make sure you have set the sweep to run from 20Hz to 20kHz. You never know.
- Use REW's generator to play test tones through both speakers. No need to measure, just listen to the test tones. If you can hear test tones above 5kHz, that confirms that your speakers are working and there is something awry with the measurement.
- Check if the problem occurs with both speakers. If it's only one speaker, it is possible that the tweeter has gone bust / cable to the tweeter from the crossover is disconnected or something like that.

Finally, please detail what you used to take the measurement. UMIK-1 into laptop. How did you send the sound to the speakers?

To add.

Be careful with test tones. Start with the amp volume at the lowest, start a test tone at about 2kHz, then turn up the volume slowly until it is easily hearable, but not loud. Test at that volume level.

Depending on your age, don't be surprised if you can't hear much above 12kHz.

 

[1066]

Thank you Keith,
Sound went to speakers via:

MacBook. >.
Apple Airplay. >
WiiM mini >
SMSL SU-9 >
Nord 2 (ICE 1200) >
Revel F206.

 

[1066]

To add.

Be careful with test tones. Start with the amp volume at the lowest, start a test tone at about 2kHz, then turn up the volume slowly until it is easily hearable, but not loud. Test at that volume level.

Depending on your age, don't be surprised if you can't hear much above 12kHz.

Yes, am not expecting to hear much above 12-13kHz due to mid 50s age.

 

[DVDdoug]

Be careful with test tones. Start with the amp volume at the lowest, start a test tone at about 2kHz, then turn up the volume slowly until it is easily hearable, but not loud. Test at that volume level.

I was about to say the same thing! Tweeters can't handle as much power as woofers and you can fry them with high-power continuous test tones. That includes tones you can't hear and/or that the speakers can't reproduce.

...Even the woofer in a "100W" speaker usually can't handle 100W continuous test tones. It's designed to handle 100W on the "occasional" peaks.

It does look like a "tweeter problem" to me, if it's not a measurement problem. Do you know the speaker's crossover frequency? A 7kHz crossover wouldn't be unusual in a 3-way speaker.

 

[olieb]

I got this graph and am puzzled.

Your diagram shows over 400dB dynamics, therefore it is a bit difficult to interpret.
The drop-off is extreme, a ∆ of 120dB from 5.5kHz to 7.5kHz. That is too steep for just about anything, unless the signal just stopped.
Is this a sweep? Starting at 2Hz? Airplay has a considerable delay, that can cause problems.
Maybe try to play some noise with the generator and check with the RTA window of REW?

 

[1066]

Started at 2,000Hz test tone from REW at low volume level to speakers.
Between 7,500Hz and 8,000Hz the level drops hugely and can barely hear anything.

I plugged direct into the DAC this time with USB cable to avoid Wiim Mini/Airplay in the chain.

 

[1066]

Apologies if REW sweep is not to right scale - am very new to REW.
Do these files help?

I will try a 0º sweep later. ‍

 

[staticV3]

Started at 2,000Hz test tone from REW at low volume level to speakers.
Between 7,500Hz and 8,000Hz the level drops hugely and can barely hear anything.

I plugged direct into the DAC this time with USB cable to avoid Wiim Mini/Airplay in the chain.

Try sending the test tone to the SU-9 from another source device (phone, laptop, PC etc). Maybe your iPhone via Bluetooth.

In REW you can export the measurement sweep as .WAV file using the Generator, then in the Measure dialog set the Playback: from file.

The .WAV file can by synced to your iPhone via Music/iTunes.

If the HF drop-off persists across multiple source devices, then I'd blame the DAC.

If it goes away, then something on your MacBook is messing up the sound.

 

[1066]

I was about to say the same thing! Tweeters can't handle as much power as woofers and you can fry them with high-power continuous test tones. That includes tones you can't hear and/or that the speakers can't reproduce.

...Even the woofer in a "100W" speaker usually can't handle 100W continuous test tones. It's designed to handle 100W on the "occasional" peaks.

It does look like a "tweeter problem" to me, if it's not a measurement problem. Do you know the speaker's crossover frequency? A 7kHz crossover wouldn't be unusual in a 3-way speaker.

This is the Revel Spec page for the 206. The crossover points do not look to be that high for MID > Tweeter?

 

[1066]

Try sending the test tone to the SU-9 from another source device (phone, laptop, PC etc). Maybe your iPhone via Bluetooth.

In REW you can export the measurement sweep as .WAV file using the Generator, then in the Measure dialog set the Playback: from file.

The .WAV file can by synced to your iPhone via Music/iTunes.

If the HF drop-off persists across multiple source devices, then I'd blame the DAC.

If it goes away, then something on your MacBook is messing up the sound.

This is the highest frequency I can hear from iPhone via bluetooth to SU-9.
Slightly lower frequency than via USB.
7,500Hz is highest I can hear sitting in front of left speaker at appx. tweeter height.

 

[1066]

Highest audible frequency via bluetooth.

 

[staticV3]

Highest audible frequency.

About matches your graph. Something's wrong.

Do you have another DAC that you could try?
Even just the MacBook's built-in headphone output would work with the right adapter.

 

[Sokel]

Do you have any way to record the DAC's output on it's own?
Not connected to anywhere else.That way you prevent accidents.

The DMM idea is good, use it with a cable for convenience, an XLR m>XLR f would be ideal as you can stick the probes in it.

Now how:
NOT like the pic you posted. You must measure 2 against 1 and 3 against 1.
Put the DMM at AC play a 10kHz tone at 3dB with the REW gen and go your way up and down, write down your findings.


AGAIN, NOT with speakers, amps and subs connected.

Edit: it would be a good idea to check it for DC too, that must be the first thing to do with all gear right after unboxing, you never know the trip they had.

 

[1066]

I have an old SMSL M8 DAC in a drawer - unbalanced phono fixed output though.
How would I control volume as I have been using SU-9 volume control?

And a Topping BC3 bluetooth receiver.

The Nord 2 amplifier has just balanced inputs.

 

[staticV3]

The DMM idea is good

Except that DMMs will drop off in frequency response far earlier than OP's issue, so can hardly be used to diagnose this.

 

[olieb]

How would I control volume as I have been using SU-9 volume control?
..
The Nord 2 amplifier has just balanced inputs.

You can control volume in REW generator.
And if everything fails, you can play the tones directly from Mac (headphone plug) to speaker, bypassing your amp too. I just checked with my Kef R3, not loud enough for party but should do for Umik check.

 

[1066]

Do you have any way to record the DAC's output on it's own?
Not connected to anywhere else.That way you prevent accidents.

The DMM idea is good, use it with a cable for convenience, an XLR m>XLR f would be ideal as you can stick the probes in it.

Now how:
NOT like the pic you posted. You must measure 2 against 1 and 3 against 1.
Play a 10kHz tone at 3dB with the REW gen and go your way up and down, write down your findings.


AGAIN, NOT with speakers, amps and subs connected.

This is all I have (which I do not know how to use).
Originally I wondered about measuring the DAC output voltage at the REW graph drop-off frequency area but was not sure which two pins to connect to and how to get it off DC Volts onto AC Volts.

Is the pin number reference I found correct?

 

[Sokel]

There's something else to check too as in an acoustic measurement like that the level shown there is crazy and I suspect the mic.
While mic is connected just hit the RTA window at REW and show it to us.

Normally it should show your room's noise floor.