Help with REW SPL Graphs

[Cincyret]

I very new to REW and audio equipment. I have a Topping EX5, a Topping PA5, and REW with the minidsp mic. On April 19th & 25th I took measurements of my Left & Right speakers. The graphs show a vast (to me???) difference!
1) Do the graphs point to a miscalibration in REW?
2) A problem with the EX5 DAC?
3) A Problem with the PA5 AMP?
4) A problem with the mini monitor speakers?
5) A problem with the microphone?
6) Something else entirely - OR a complete misread of the graphs on my part?
In addition I've included the graph of 5 succesive measurements that averaged to the Apr 25th graph. Note the variance between measurements.
I hope I've posted in the correct place...(Room EQ?, PA5?, REW?)- Are my attachments too big?
Thanks,
John

 

[HarmonicTHD]

That c

I very new to REW and audio equipment. I have a Topping EX5, a Topping PA5, and REW with the minidsp mic. On April 19th & 25th I took measurements of my Left & Right speakers. The graphs show a vast (to me???) difference!
1) Do the graphs point to a miscalibration in REW?
2) A problem with the EX5 DAC?
3) A Problem with the PA5 AMP?
4) A problem with the mini monitor speakers?
5) A problem with the microphone?
6) Something else entirely - OR a complete misread of the graphs on my part?
In addition I've included the graph of 5 succesive measurements that averaged to the Apr 25th graph. Note the variance between measurements.
I hope I've posted in the correct place...(Room EQ?, PA5?, REW?)- Are my attachments too big?
Thanks,
JohnView attachment 202347View attachment 202348

That cut off at 8kHz is strange indeed.

What speaker do you have?

Do you have a weak computer? If yes try to increase buffer size from default 32k to 64k or higher.

There is a REW help thread already. Have a moderator move your post so you get more attention

REW Frequency Response Measurement Question (Help Request)

So today I took the first step towards getting more familiar with my system through measurements. My questions are: 1. In REW, there is a drop down menu, (circled in green), how come I do not see a dB option? When I see everyone else's charts it looks like the Y axis is in dB, there is other...

www.audiosciencereview.com

 

[Deleted member 46664]

One of the first life-lessons from REW is that moving the mic or the speakers even a couple of inches can get you an entirely different result.

To get a good in-room measurement...
1: the mic needs to be right in the centre of your listening position
2: the two speakers need to be within 1/4 inch of exactly the same distance from the mic.
3: the angle from the mic to each speaker needs to be within a couple of degrees of identical

To get the same measurement twice...
#1 through 3 need to be exactly the same as last time
and the output level from your speakers needs to be exactly the same.


That near vertical drop off at 8khz is worrying ... play your speakers at low volume and put your ear right up to each driver, make sure everything is working.

Also... we don't here in 1/24 octave slices ... try applying Psyacoustic smoothing to see a better picture of what you're actually hearing.

 

[Cincyret]

That c

That cut off at 8kHz is strange indeed.

What speaker do you have?

Do you have a weak computer? If yes try to increase buffer size from default 32k to 64k or higher.

There is a REW help thread already. Have a moderator move your post so you get more attention

REW Frequency Response Measurement Question (Help Request)

So today I took the first step towards getting more familiar with my system through measurements. My questions are: 1. In REW, there is a drop down menu, (circled in green), how come I do not see a dB option? When I see everyone else's charts it looks like the Y axis is in dB, there is other...

www.audiosciencereview.com

1) Speakers - Salk Sound WOW1 - 3 yrs old - I closed the port with acoustic foam (3 yrs ago). I like them, although I'm aware of contrasting views.
2) An NUC with 16gb memory, 8th Gen i5. I'm not sure of what buffer I should increase - In the REW measurement window the Length setting is 1M & the Sample rate is 192 khz.
3) I'm new...How do I ask the moderator to move the post (thread?)?
Thanks,
John

 

[Cincyret]

One of the first life-lessons from REW is that moving the mic or the speakers even a couple of inches can get you an entirely different result.

To get a good in-room measurement...
1: the mic needs to be right in the centre of your listening position
2: the two speakers need to be within 1/4 inch of exactly the same distance from the mic.
3: the angle from the mic to each speaker needs to be within a couple of degrees of identical

To get the same measurement twice...
#1 through 3 need to be exactly the same as last time
and the output level from your speakers needs to be exactly the same.


That near vertical drop off at 8khz is worrying ... play your speakers at low volume and put your ear right up to each driver, make sure everything is working.

Also... we don't here in 1/24 octave slices ... try applying Psyacoustic smoothing to see a better picture of what you're actually hearing.

1) I've attached the graphs with psychoacoustic smooth. My question is about the large difference between 40 and 150hz and the 8khz drop. Both (4/19 & 4/21) were taken at tweeter height (+/- 2 inches to be generous), centered (+/- 3 inches), 6.5' between speakers & 8' to mic (+/- 3 inches), angled in - I don't know the +/- in degrees. I did, however also take measurements with the speakers pointed straight ahead...it didn't seem to make a significant difference.
2) Listening to the speakers: I apologize..I'm very new to this - Should I listen to a 'sweep' or something else? Listen to the tweeter vs the woofer? - I'll try this.
3) Can you make a guess about the cause: Is a speaker problem more likely than an amp/dac problem?
Thanks,
John

 

[HarmonicTHD]

1) Speakers - Salk Sound WOW1 - 3 yrs old - I closed the port with acoustic foam (3 yrs ago). I like them, although I'm aware of contrasting views.
2) An NUC with 16gb memory, 8th Gen i5. I'm not sure of what buffer I should increase - In the REW measurement window the Length setting is 1M & the Sample rate is 192 khz.
3) I'm new...How do I ask the moderator to move the post (thread?)?
Thanks,
John

Ok. The speaker specs do not explain the weird 8kHz drop not the strange bass (just went to their website).
So most likely the culprit is your REW setup. I would guess your 192kHz sample rate is too high for your computer (-and your buffer). Set it to 48kHz as you only measure 20to20kHz anyway. Most likely when set to 48kHz the buffers are fine with their default values. I will be home in ca 2 hrs then I can post a screenshot on how to setup your sweeps. And be more detailed to get your thread moved.

 

[Cincyret]

To quote Roseanne Roseannadanna "Never Mind" - see graph. I'm sorry for the confusion. Back to normal. Thanks for taking the time with a newbie. Next time I'll give it a couple of days (weeks?) before I post.
John

 

[Deleted member 46664]

My question is about the large difference between 40 and 150hz and the 8khz drop.

Yeah ... that's worrisome.

Try running sweeps for the speakers separately... if there's a big difference that's a good hint.
Do you have another amplifier? Try hooking it up and testing.
Same with the DAC... see what a different one does.

Also are you running any kind of software for room correction or EQ? Try disabling that and testing again.

I don't know for sure what the problem is... but I can tell you it ain't good.

2) Listening to the speakers: I apologize..I'm very new to this - Should I listen to a 'sweep' or something else? Listen to the tweeter vs the woofer? - I'll try this.

naaa... just play some music quietly so you can hear each cone/drive separately and put your ear right near them. If you get one or more that aren't making sound, you might have a problem ... Not "do" ... "might" ... then it needs further investigation.

3) Can you make a guess about the cause: Is a speaker problem more likely than an amp/dac problem?
Thanks,

Do you have an alternate input you can hook up? Try that and see if it changes.

Also from experience I would say this is more a room/speaker problem than one from electronics. The electronics (amp/dac/etc) usually breaks down all across the spectrum... not at specific frequencies ... that's most often a speaker thing.

JohnView attachment 202521

 

[Deleted member 46664]

To quote Roseanne Roseannadanna "Never Mind" - see graph. I'm sorry for the confusion. Back to normal. Thanks for taking the time with a newbie. Next time I'll give it a couple of days (weeks?) before I post.
JohnView attachment 202533

What did you do to fix it??
might help the next person...

 

[Cincyret]

I think (???) that the USB cable wasn't plugged in entirely. I checked the mic attachment yesterday and it was fine. BUT.. there is an extender cable to the PC - I didn't check it. AND I didn't check the USB/PC plug.
Moral: Flaky results (on anything)? - Check the cableing!
Thanks again,
John

 

[HarmonicTHD]

To quote Roseanne Roseannadanna "Never Mind" - see graph. I'm sorry for the confusion. Back to normal. Thanks for taking the time with a newbie. Next time I'll give it a couple of days (weeks?) before I post.
JohnView attachment 202533

Blue and red look better except for the 20dB difference. What’s up with the green one, still strange. Run some separate, single sweeps for each speaker without averaging and ideally with VAR smoothing not Psy.

 

[Cincyret]

I think the blue & red diff is due to volume (SPL???) diff. I'm not going to sweat it. Thanks for your patience.
Note: I'm very new to this measurement thing. REW has so many controls (mic volume calibration just for one), then there are the placement of speakers & mic, then the controls on the audio equipment. All I can say is: Doing measurements myself raises the level of respect I have for Amir and ASR!
John

 

[HarmonicTHD]

I think the blue & red diff is due to volume (SPL???) diff. I'm not going to sweat it. Thanks for your patience.
Note: I'm very new to this measurement thing. REW has so many controls (mic volume calibration just for one), then there are the placement of speakers & mic, then the controls on the audio equipment. All I can say is: Doing measurements myself raises the level of respect I have for Amir and ASR!
John

Got it. We all went through that learning curve. Just in case you haven’t seen it. This a beginner friendly guide.

UMIK-1/2 setup with REW

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