# Problems with measurements in REW V5



## AudioNerd (Apr 4, 2013)

Good morning forum ,

i find out about REW V5 yesterday in the afternoon and was excited that i found that tool i was so long looking for. So i first installed the tool "Equalizer APO Version 07" and after that i installed REW. I played around with the different filters (sadly Equalizer APO just supports Generic). After i posted my attempts in a different forum a member drew my attention that the frequency response from my soundcard and my box (what i thought i was measuring) looks quite similar. I recently made also a measurement with the Demo of ARTA and this looks more realistic, the frequency response was rapidly falling in level around 60Hz otherwise did REW. Here it seems that my box runs full level to 20Hz  (which just is not possible with 4 x 6.5" drivers in closed box).

So i check the preferences if i used the right input and output devices and yes, i did. Also the program reacts to my finger snipping in front of my microphone with increasing levels so i know now that REW does not ignore my mic .

The level at measuring was also high enough (REW showed me 10dB).

Any ideas what i did wrong here? I attached the frequency response of my soundcard and of my "box" (which is indeed my soundcard i think) and a frequency response from ARTA.

Thanks for reading i hope you understood the important things :gulp:

With friendly greetings

AudioNerd

P.S. Therefore i can upload just one image here is only the soundcard frequency response from REW (Preferences -> Calibration -> Calibrate).

PPS: Maybe i should explain about how REW and Equalizer APO are hanging together. I measure the frequency response, i get my filters, then i save my filters and then i export the filter to a .txt file. Equalizer APO use this .txt file from REW now and change the output of my soundcard by the filters saved in the textfile. Here is one textfile:



> Filter Settings file
> 
> Room EQ V5,00
> Dated: 04.04.2013 13:38:47
> ...


PPPS: Now another problem suddenly appeared. After i get my right filter result i started battlefield 3 to play a little bit but the sound was so horribly (a lot of scratching at higher frequencies and if i shoot with a weapon it sounds like through a curtain) that i quit. The strange thing is, that if i am listening to music this scratching does not appear :huh: and also after quitting battlefield the sound does not change anymore if i change some settings in the config file from Equalizer APO (changing Filter .txt or Preamp values), even after a reboot...

Now something really strange has happened:

If i watch a video on YouTube and change the Preamp value in the Equalizer APO config-File, the sound changes too. But if i am listening to music through spotify nothing changes.

Suddenly, after i rebooted again, everything works fine (concerning the problem that the sound did not change if i change the paramters in the config file). But the soundproblem with BF3 does still exist.

But another problem:

If there is bass in the song the music gets a lot lower after it gets to the normal loudness. I read something about a windows limiter but i can't find that one in the sound options? Where is it? Does Equalizer APO maybe cause the problem?


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## JohnM (Apr 11, 2006)

Can you post the mdat files for your soundcard and speaker measurements? That measurement plot you attached looks more like noise, but it has such a huge vertical scale that it is hard to tell (this post has advice on the scale to use for graphs). 

It would be best not to use any filter settings until the measurements are confirmed to be valid.

I wonder if Equalizer APO doesn't like the use of comma as decimal delimiter in the filters file? Might need to replace the ','s by '.' and the '.'s by ','.


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## AudioNerd (Apr 4, 2013)

Ah a reply, thank you very much 

I replaced "," by "." and "." by ",", now it sounds a lot different and completely wrong...I attached the measurement file of my soundcard and my box.



> That measurement plot you attached looks more like noise


ARTA measures the same frequency response.
The strange thing is that a few weeks ago the frequency response from my loudspeaker looks completely different and more realistic (also measured with ARTA):

3 Weeks ago (different scaling):

http://www.fotos-hochladen.net/uploads/frequenzgangmeme20rt14pd.jpg

Now:

http://www.fotos-hochladen.net/uploads/frequenzgangbo5ey1nq4ipa.jpg


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## JohnM (Apr 11, 2006)

The soundcard loopback measurement certainly has some problems, and a very high noise level:








Was that measured into a line input? I recommend you clear that cal file from REW and do not use it.


With the cal file cleared the measurement itself looks OK though (1/6th octave smoothed for easier comparison with your ARTA measurement):


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## JohnM (Apr 11, 2006)

The soundcard loopback measurement certainly has some problems, and a very high noise level:








Was that measured into a line input? I recommend you clear that cal file from REW and do not use it.


With the cal file cleared the measurement itself looks OK though (1/6th octave smoothed for easier comparison with your ARTA measurement):


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## AudioNerd (Apr 4, 2013)

> With the cal file cleared


How can i clear that? Does this noise affect the frequency response from my loudspeaker strong or just a little bit?



> comparison with your ARTA measurement


But why does the frequency response from 3 weeks ago looks so different. I can't believe that this loudspeaker (closed box with 4x 6.5" Drivers) is running to 20Hz (or is this peak a superposition from the room?).

Should i try out some filters now?


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## JohnM (Apr 11, 2006)

To clear the cal file for future measurements go to the REW mic/meter preferences and click the 'Clear Cal' button. For existing measurements click the 'Change Cal...' button on the tab for each measurement.

The 23 Hz peak is certainly a room resonance.

Try *one* filter and measure with it in place to see if it had the expected effect, no point trying a dozen filters until you are sure a single filter works correctly.


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## AudioNerd (Apr 4, 2013)

I tried to reduce the valley at 86Hz, i think it worked.

But this is not explaining why i get those limitations when there is bass in the music...


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## JohnM (Apr 11, 2006)

Are you trying to use filters with boost to correct those narrow dips? That is a very bad idea. Firstly, the dips are usually very location dependent, moving a small distance can give a very different measurement. Secondly, any boost in the filter reduces headroom in the audio chain. The audio path can only carry a signal up to a certain level, if you have a filter with 10dB (say) of gain then any audio at the filter frequency that is less than 10dB below the maximum the channel can carry would result in clipping after the filter. Most equalisers would simply clip, causing heavy distortion, perhaps the Equalizer APO is smart enough to turn down the level of the whole audio signal to prevent the clipping. The basic problem is using a filter with boost in the first place, though.


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## AudioNerd (Apr 4, 2013)

> Are you trying to use filters with boost to correct those narrow dips?


Yes  :scratch:



> Most equalisers would simply clip, causing heavy distortion, perhaps the Equalizer APO is smart enough to turn down the level of the whole audio signal to prevent the clipping.


Ok, maybe that caused the problem...Equalizer APO just supports the filter "Generic" and "FBQ2496".
How should i correct or improve my frequency response, do you have any ideas? If i use Low or High Pass Filters i can't set which order (1rst to 4th).


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## JohnM (Apr 11, 2006)

AudioNerd said:


> How should i correct or improve my frequency response, do you have any ideas?


Start with trying different positions for the speakers and/or where you sit, as far as you are able, to try and get the smoothest response before any EQ - look for a response that does not have broad dips in the response. After that you could try using filters to bring down some of the peaks at low frequencies. The response looks OK already though, is there some particular feature of the sound that is bothering you?


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## AudioNerd (Apr 4, 2013)

The place of this speaker and me can't be changed (Pc-Speaker and no other position is possible).

I especially don't like the overdone heights and the big valley at the higher mids, and the bass is a bit low for my opinion.

So i should not work with this peak-filters because it can cause this limitations?

It also seems that Low or Highpasses does not have any affect on the sound. If i put in a 100Hz Lowpass and put this filter into Equalizer APO i can't hear any difference. Are there any other programs out there who can work with the files from Room EQ Wizard so that the filters affect the outcomming sound?

So i set a few filter who are correcting the big problems in the frequency response. Music sounds now a lot better. I lowered the very highs and pushed the crossing between woofer and tweeter (around 2.5kHz). I also pushed the Bass around 30 to 100Hz a bit. This causes this limitations again but now its hardly noticeable. The .mdat file is over the 9.33MB so i had to upload it at an external site:

http://dfiles.eu/files/av1k6nygi



But i have still one problem:

If i start Battlefield 3 the sound is horrible (again a lot of scratching and very dull) and it also happens if the filter is turned off in the config file of Equalizer APO! It seems that it is just BF3, if i start a other game the sound is normal...

Edit: Ok solved, there was a problem with the audio settings inside battlefield. Now everything is fine. Remains the questions: Are there other equalizers (such as Equalizer APO) who can work with Room EQ Wizard? It is odd that i can't push the bass without getting these limitations even it is just around +3dB...If i push 30Hz about 20dB in these normal "cheap" Equalizers with just 5 different Hz informations (30, 90, 300, 3000, 9000) i don't get those limitations.


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