# Using the measurement graphs, and interpreting the results...



## chrome7713 (Jan 7, 2012)

Hello,
So I've successfully got measurements for my room, both before and after some bass trap treatment. (phase1)
Thing is- what is the best way to interpret the graphs?

Are spikes/sharp troughs in the graphs the thing to watch out for?
_I noticed after reading some posts here that Blaser posted some graphs with some pretty smooth waterfalls.. and had a few gushing comments from people.._ 
So that would lead me to assume that spikes=bad and smooth plots =good.
Is this correct?

Should I be looking at the waterfalls only? Or is there a prefferred sequence/choice of which graphs to use for certain situation analysis?
If someone more learned lddude: could lend a guiding hand I'd appeciate it 

All advice is gratefully received. :T


----------



## fusseli (May 1, 2007)

More or less, ya, smooth plots are better than peaky plots. You can refer to the SPL graphs for applying EQ, and waterfalls to start to see where your room really resonates (or where your speakers might be also, depends). There are more advanced analyses, yes, such as RT60. It all just depends on what you're trying to accomplish.

Care to share your results? :bigsmile: Before & afters are always interesting to see.


----------



## chrome7713 (Jan 7, 2012)

Hello!
I must admit my testing was pretty crude and used a very basic mic loaned to me...

As You can see the LF spikes are better, but still not perfect after installing the basic trihedral traps with a corner fill each side. 

I produce drum and bass tracks - so a bit of LF taming goes a long way 

I know that the MF and HF still needs taming and that's next to do on my list.
I'm working to an extremely tight (wife friendly) budget so went for foam over fibre at this time.

Any thoughts on the graphs?


----------



## SAC (Dec 3, 2009)

The frequency response plots with excessive comb filtering appear as if there are several sources being driven simultaneously. 

For modal waterfalls use the Limits function to set the Y axis frequency from ~10 Hz to about ~250 Hz.
And the Z axis time to 1 second, and the Y axis gain from and abut 20 to 65 dB (using current values). Also, toggle the frequency button to display a linear rather than a logarithmic frequency scale.

Did you calibrate the gain? If so, the level is too low with a maximum gain of about 65 dB.

For information above the modal range forget about the frequency response and instead use the ETC response generated per each individual source driven singularly. The ETC will show each individual direct and indirect energy arrival from which you will be able to identify arrival time, gain, vector path and point of boundary incidence as well as a qualitative assessment of the the sparseness or diffuseness of the energy.


----------



## chrome7713 (Jan 7, 2012)

A very informative post.. thanks.

I'm running only one monitor during the measurement..
The gain was set to 50% for the soundcard master volume during the calibration.

When I did the room measurement I had to turn it up to maximum to hit the threshold requirements for both the soundcard output _and_ the input gain from the Mic (and I've set the input to INST rather than line to boost it further).. this is probably a fail on my part.
As I said before- the mic is low quality... and is possibly part of the problem?
Perhaps I can boost the volume of the sweep (it's currently at -12dbFS)..

I'l look into it; and boost to -6dbfs and recalibrate the interface at max master gain and run the subsequent room test again at max gain and post back when I can. 
Thanks again for your patience.

Edit* Oh and the above graphs are single 'waterfall' slice.


----------



## chrome7713 (Jan 7, 2012)

Hey SAC,
To clarify:
First I calibrated the soundcard so that both input/output read -6.0dbfs.
That looked like this:








Next I plugged in my Mic (rubbish brand.. super cheap- loaned from a friend). 







As you can see I've had to boost the output gain so that the mic will pick up the sweep at a decent level
(Mic input gain is at Max too, and INST button is pressed to boost it further)

The resulting waterfall looks like this:








So is it that the mic is just rubbish?
Or is my room just doomed?
Or am I just plain doing it wrong?

Thanks in advance.


----------



## chrome7713 (Jan 7, 2012)

For your reference (it means little to me at this time :rubeyes: ) here are the relevant ETC graphs for the same measurement:






Default/Soundcard






Default/Measurement






Default/Combined






Combined/smoothed 5ms
View attachment FEB9_MASTER_MEASURE.mdat
-mdat file.

I'm open to learning how to understand these graphs.. so thanks in advance for your time in replying


----------



## frullog (Feb 15, 2012)

I'm new of the forum and i thank you for to share the experiences. Thanks


----------



## SAC (Dec 3, 2009)

Please just post the .mdat file(s).


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

SAC said:


> Please just post the .mdat file(s).


See post #7.

Regards,
Wayne


----------



## SAC (Dec 3, 2009)

Thanks Wayne...

Attached find a few of the convolved plots.

The mic must be an omni-mic.

I quite frankly don't know what is up.

The levels (if there has been Any adjustment) are extremely low and they do not track between views.

The FR lacks detail (in addition to gain) - in fact it lacks detail even if it were heavily smoothed; and the overall slope is very questionable.

If the FR is hosed, the derived impulse will be questionable despite its looking 'OK'. But the *really* wonky response is the ETC - the single ski slope bump beginning before the direct arrival and decaying to ~15ms...

Lots of questionable results... I don't know what to tell you, except that you need to use the proper equipment and perform setup.


----------

