UM1-K has arrived - now to get started, but sweep and moving mic measurements don't line up.

[antcollinet]

Mic arrived today a day early from Hong Kong, and no import duties collected - bonus.

I initially started a thread here
https://www.audiosciencereview.com/forum/index.php?threads/planning-room-eq-like-this.26409/
for some up front advice (thanks to everyone who helped), but have since realised it was the wrong sub forum, so I'm starting a new thread here.
(If anyone wants to move the previous thread, feel free)


So in the other thread moving mic measurement was suggested and I would like to give it a try. However, I'm getting significantly different SPL levels from the moving mike method compared with the sweep measurement.

I've added the cal file for the UMIK-1. I've set an SPL of about 75 with pink noise from the generator.

I've carried out a sweep measurement, then a capture from the real time analyser - which I believe is what is used for a moving mic measurement from the video linked in the other thread. However, the video didn't give any info on setting up the measurement. Settings and Mic position are unchanged between the two measurements.

In the screenshot, the green line is the curve from the sweep measurement, and the red curve is from the real time analyser. As can be seen the sweep gives a much higher level (and closer to the 75dB set up in the SPmeter). The RTA curve is very similar in shape, but about 20 to 25 dB lower, and with the higher frequencies falling off more.

Any ideas what I may have wrong in (I'm assuming) the RTA measurement?

Thanks.

 

[abdo123]

Can you show your RTA settings?

 

[abdo123]

Also if you're finding the MMM method to be too difficult just take 6 sweep measurements and average them, this should minimize the statistical variance quite a bit.

 

[antcollinet]

Can you show your RTA settings?

Thanks for getting back so quickly.

Here are the RTA Settings (all I could find). I think all default, except for smoothing

 

[tecnogadget]

Take a look at this thread so you can copy the correct RTA settings for MMM Technique.

https://www.audiosciencereview.com/forum/index.php?threads/rew-moving-microphone-method-help.12641/

 

[antcollinet]

Thanks - I'll try that after lunch.

 

[DJBonoBobo]

Take a look at this thread so you can copy the correct RTA settings for MMM Technique.

https://www.audiosciencereview.com/forum/index.php?threads/rew-moving-microphone-method-help.12641/

Yes. Additionally, activate "Adjust RTA levels" to correct the 20-25 dB lower appearance.

 

[Hipper]

A single point measurement is ideal for one listening position. If you plan for a few people to listen on a sofa then perhaps a multi position average or the MMM may be better.

As far as I'm concerned measurements like you've shown are a guide to be used to get you to where you want. So whether one line is 25dB more then the other doesn't matter. It's the shape that's important. The main point is to be consistent in the way you measure so that you can see changes after implementing filters.

I listen on my own and I prefer the single point arrangement with a sweep as it's easy to be consistent. I've never tried the MMM method.

Looking between 30-300Hz both measurements show your problems for boomy base. Using either of them to generate your filters to flatten the FR then apply them. Listen to some music. Not for a few minutes but a few days. It may take time for you to adjust to less but more musical bass. If it's bass light then perhaps you may prefer a downward slope from low to high frequencies.

Once you've got a satisfactory bass address any problems higher up.

You mentioned phase on your other thread. I found that phase improves as you correct the FR as well as when you add room treatment. Indeed I found room treatment perhaps more important then FR correction as this reduces decay times which I think is an issue which has a big if not most important, part to play in getting accurate sound.

Above all do not get obsessed about getting the perfectly flat FR. Listening to your music should be the ultimate judge for you.

 

[antcollinet]

OK - so the adjust RTA Levels has put me about 20dB the other way, but the RTA 1/48 now gives a jagged stepped line with no smoothing options.

Is that what I should expect.

When I do a "check levels" on the measurement sweep, I'm getting about -56dB headroom - is that related?

 

[abdo123]

OK - so the adjust RTA Levels has put me about 20dB the other way, but the RTA 1/48 now gives a jagged stepped line with no smoothing options.

Is that what I should expect.

When I do a "check levels" on the measurement sweep, I'm getting about -56dB headroom - is that related?View attachment 152335

Yes this looks okay, just try to capture more area while you're moving the mic, cylindrical motion with a 1m radius.

 

[antcollinet]

OK - but in the video, and with other peoples plots, I am seeing smooth traces rather than the jagged one.

Does that matter?


EDIT - OK never mind - I can apply smoothing once the measurement is saved. That is looking much better now - thanks all.

 

[Jdunk54nl]

Isn't it fun how energy works

A sweep plays a single sweeping tone at full energy. Pink noise plays all of the stuff at full energy. That is why the differences in SPL are seen between sweeps and pink noise. So pink noise spreads the energy out throughout all of the frequencies instead of a sweep that focuses it all at whatever single frequency is playing at the small moment in time.

Also make sure you are using pink periodic noise and setting the FFT length in the RTA window to match.

 

[Jdunk54nl]

OK - but in the video, and with other peoples plots, I am seeing smooth traces rather than the jagged one.

Does that matter?


EDIT - OK never mind - I can apply smoothing once the measurement is saved. That is looking much better now - thanks all.

You want to capture the data at the highest resolution possible. Once you are done capturing and saving the data, you can post smooth in the All SPL window by clicking the controls gear and choosing what you want to smooth too. I would suggest 1/6 to start.

 

[antcollinet]

Here is the result: Lighter (lower) orange trace is a sweep from slightly the wrong postion. The other three are all MMM traces.

 

[Jdunk54nl]

Also, if you want to do a bunch of sweeps, you can have them all selected in the ALL SPL tab and then you can vector average them together. This will average the results into a mmm result. I still much prefer the pink noise approach because you can see when the RTA stops moving and that is the best average you will get and repeatable.

 

[antcollinet]

So - I've done a left and right separate EQ From my "at the desk" listening position. Plots here show (in order)

Measured before (Right)
Predicted (Right)
Measured after (Right)
Measured after (Left)

Filter was from 35 to 700 Hz

 

[Jdunk54nl]

Looks good overall!

Are you setting up a target to EQ to in the EQ window?

I personally would knock down the energy on both speakers from 3500hz to 7000hz and try to a/b it if I like that better. Similar with 700-1000hz. These are pretty wide q areas and I bet it would sound better with those wide peaks knocked down a little.

 

[antcollinet]

I could probably do that just by extending the band of the EQ - I stopped it at 700Hz. I'd read somewhere that it didn't make sense to EQ above Bass to low mids.

 

[GimeDsp]

Hi, I have been have the SAME problem with REW RTA.

The RTA seems broke now.
It use to properly display RTA (spectrum) when using pink noise. Not it has a HUGE TILT like yours and it will not display properly that way

It will display properly is you change spectrum to "RTA 1/48" or other RTA that is smoothed. However the display sucks and isn't very useful for tuning.

ONE measurement is really not ideal and should be avoided UNLESS you have a perfectly symmetrical room.

You should take at least 2 mearuemts, where your ears will be.

If you use the MMM you should only do it near the listening area as some location outside may have huge peaks and dips that can affect your "average". There is no point in adding this information into your MMM.

There is a reason to EQ above 300-400hz or where the room becomes dominant. that is to correct speakers response issues, like what Amir does.

With EQ in the higher frequencies you have had narrow and low DB or wider and higher DB, and you can have low and wide.

I believe this is why you see Amir using a Q of 2 when he adds some boosts, and the same reason I do.
So there are very good reasons to boost and cut frequencies high and low, it just has to be done correctly to avoid artifacts.

PS-the sweep and RTA on my REW both seam to be broken and don't jive with Systune program

 

[Jdunk54nl]

I could probably do that just by extending the band of the EQ - I stopped it at 700Hz. I'd read somewhere that it didn't make sense to EQ above Bass to low mids.

It is fine to EQ in higher frequencies, ideally this would be done with a good directivity speaker that way you are fixing both the on-axis and off-axis response when you EQ. If you do it with a speaker that has directivity errors, then when you fix what you measure, you may mess up the on/off axis response because the on/off axis responses don't do the same thing.

Either way, try it, A/B the results and see which one you like better. Choose a couple of good songs that you know well and A/B the EQ.