# Need help interpreting measurement



## gdereese (Jul 28, 2012)

I've taken a measurement of my home studio (13'8" w x 15'1" d x 9' h) after applying treatment to my early reflection points (side walls and ceiling), along with bass traps in the front vertical corners (starting at the ceiling going down 4').

The purpose of the treatment was to clear up the flutter and improve my bass response. My mixes end up bass and treble-heavy as it seems I'm compensating for room issues. However, I need some guidance in interpreting the graph, and/or maybe some perspective as to how my response measures up to what is ideal, so that I can tweak whatever needs tweaking with my placement of speakers or treatments.

Looking at it myself, it looks like a pretty deep null between 90-100Hz and a general rolloff of higher frequencies, especially after 2kHz or so.

I've attached the graph. If anyone can take a moment to assist me with this, I would very much appreciate it.

Also, if there's any further info I can provide to help with your assessment, please let me know. Thanks!


----------



## phazewolf (Feb 5, 2012)

Do you have a sub? What are your mains crossed over at. Also what are you using for mains, wile that is a nasty dip and a guess is it has to do with the L and W of your room. 

Where is your mixing spot located in the room and have you tried to move it or move the drivers to see if the dip gets better or worse?


----------



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

First, welcome to the Forum, gdereese!




gdereese said:


> My mixes end up bass and treble-heavy as it seems I'm compensating for room issues.


That’s easily explained by your graph. Assuming an accurate measurement with a calibrated mic aimed at the speaker(s), your response at 10 kHz is nearly 20 dB lower than 100 Hz. And response falls like a brick below 100 Hz. So yes, your mixes end up bass and treble heavy because you’re compensating for a poorly-balanced system. (In this case, the null at 90 Hz is of no consequence. Even if it was eliminated, response below 100 Hz is still rolling out at 20 dB/octave or worse.)

Not sure what to recommend for a fix, but it looks like you should definitely consider getting a subwoofer to fill in the lows your main speakers are lacking. Dealing with the high-freq situation is more problematic. It’s so bad it’s beyond fixing with equalization, IMO (again, assuming an accurate measurement).

Regards,
Wayne


----------



## phazewolf (Feb 5, 2012)

That also brings up a good point. You said you had room treatments what are they how thick and where are they located? 

You maybe using room treatments that are as you see in the graft killing to much of your highs and not doing anything for the lows. Just for kicks try removing the room treatments if you can and rerun the room sweep and post it.


----------



## gdereese (Jul 28, 2012)

> Do you have a sub? What are your mains crossed over at. Also what are you using for mains, wile that is a nasty dip and a guess is it has to do with the L and W of your room.
> 
> Where is your mixing spot located in the room and have you tried to move it or move the drivers to see if the dip gets better or worse?


I do not have a sub in this setup - only a set of self-powered nearfield monitors (M-Audio Studiophile SP-5B). I noticed that in the product specs, the frequency response is stated as 33Hz-22kHz, while the range of the included frequency response graph only goes down to 200Hz (probably intended to make the lack of lower bass less obvious to the consumer; maybe it was intended to be accompanied with a sub to compensate). I've attached the graph for reference.









My mixing spot is virtually centered horizontally between the side walls (offset an inch or two to get away from nulls found in the center), and I tried to get as close to the magical 37% distance away from the front wall as practical.

I have not tried much moving around of anything as of yet, as I was convinced my problems would be solved with treatment. But I could be wrong...that's why I'm posting here 



> That’s easily explained by your graph. Assuming an accurate measurement with a calibrated mic aimed at the speaker(s), your response at 10 kHz is nearly 20 dB lower than 100 Hz. And response falls like a brick below 100 Hz. So yes, your mixes end up bass and treble heavy because you’re compensating for a poorly-balanced system. (In this case, the null at 90 Hz is of no consequence. Even if it was eliminated, response below 100 Hz is still rolling out at 20 dB/octave or worse.)
> 
> Not sure what to recommend for a fix, but it looks like you should definitely consider getting a subwoofer to fill in the lows your main speakers are lacking. Dealing with the high-freq situation is more problematic. It’s so bad it’s beyond fixing with equalization, IMO (again, assuming an accurate measurement).


I am using a Behringer ECM-8000 omnidirectional mic for measurements. I have also calibrated for my audio interface and mic (I have CAL files for each). However, my first measurement was done with the mic pointed upward per the directions in this REW tutorial video (mic instructions are about 3:25 in from the start): 



. I have since done another measurement with the mic pointing forward and attached a new measurement graph.











> That also brings up a good point. You said you had room treatments what are they how thick and where are they located?
> 
> You maybe using room treatments that are as you see in the graft killing to much of your highs and not doing anything for the lows. Just for kicks try removing the room treatments if you can and rerun the room sweep and post it.


I have treated the first reflection points (side walls and ceiling) with 2'x4' groups of Auralex foam, with 4' worth of Auralex LENRD bass traps in the front vertical corners of the room.

I know I've written a novel, but wanted to include everything asked for up to this point and see what you guys think from there. Again, thanks so much for taking the time to help!


----------



## ALMFamily (Oct 19, 2011)

Could the null you are seeing be caused from the rear wall? If you take a measurement from the primary seat and then move the mic forward about a foot and take another measurement, does the null move accordingly?


----------



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

gdereese said:


> However, my first measurement was done with the mic pointed upward per the directions in this REW tutorial video (mic instructions are about 3:25 in from the start):


 What they forgot to mention in that video is that upright mic orientation requires a 90-degree calibration file to compensate for the mic’s natural off-axis sag in response. You can see the difference between your two new measurements. (With the appropriate calibration file for the earlier measurement, the two should have looked about the same.)

Really, horizontal orientation is best for free field measurements. You can see more about mic orientation here.



> I have treated the first reflection points (side walls and ceiling) with 2'x4' groups of Auralex foam, with 4' worth of Auralex LENRD bass traps in the front vertical corners of the room.


The function of treatments is to reduce reflections and “deaden” the room. They aren’t going to have a tremendous effect on frequency response.

I’d like to revise some of what I said in my previous post about your high-frequency response. With nearfield monitors it’s not unusual for the highs to be reduced, since you’re sitting so close to them. So if your mixes are all turning out to be treble-heavy, as you mentioned, then that should be easy to fix with a simple tone control adjustment. I looked up some reviews of the SP-5Bs and their weak bass is pretty much universally acknowledged, so you do need to add a subwoofer. But fixing the highs should be easy.

Regards,
Wayne


----------



## gdereese (Jul 28, 2012)

> Could the null you are seeing be caused from the rear wall? If you take a measurement from the primary seat and then move the mic forward about a foot and take another measurement, does the null move accordingly?


I've attached a graph with my baseline measurement, one with the mic moved up 1 ft and one with the mic moved back 1 ft.









It looks like moving the mic up flattened the peak and null that existed between 60-100Hz, while moving it back made them more prominent. Does that suggest I should try moving my speakers and chair up 1 ft? Would that theoretically give me a result similar to the graph in terms of the bass response? I guess I'm not sure if that will hold up since moving only the mic up 1 ft places the 'ear' in a different relative location to the speakers. Am I making sense?



> The function of treatments is to reduce reflections and “deaden” the room. They aren’t going to have a tremendous effect on frequency response.
> 
> I’d like to revise some of what I said in my previous post about your high-frequency response. With nearfield monitors it’s not unusual for the highs to be reduced, since you’re sitting so close to them. So if your mixes are all turning out to be treble-heavy, as you mentioned, then that should be easy to fix with a simple tone control adjustment. I looked up some reviews of the SP-5Bs and their weak bass is pretty much universally acknowledged, so you do need to add a subwoofer. But fixing the highs should be easy.


Is there anything I should be concerned about when applying EQ to compensate for the environment in a studio settings (as opposed to maybe for home theater)? I don't fully grasp the reasoning, but I've heard/read that using EQ for this purpose can be bad for your sound - maybe having to do with distortions and unintended artifacts that come with EQ. I accept that I could be completely wrong about this, so some advice here would help.

Also, if EQ is OK to use here for correction, it seems like the target is to flatten the overall trend of the graph line. In this case, probably some kind of shelf @ 2kHz may work to compensate for the high-end rolloff. Does that seem right to you based on what you see here?


----------



## phazewolf (Feb 5, 2012)

I would move the seat fwd a foot then play with speaker placement and find the best combo.. As you can see a foot really made a nice change.

You could if you have room move it fwd a other foot or maybe 6 inches at a time if there is room and find the best spot you can then fine tune with the moving of your speakers and then put your room treatments sense the first reflection spot would of changed and finally remeasure and if you can spring the cash get a sub to fill in the missing low's.

Good luck.


----------



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

gdereese said:


> It looks like moving the mic up flattened the peak and null that existed between 60-100Hz, while moving it back made them more prominent. Does that suggest I should try moving my speakers and chair up 1 ft?


 Sure, you can try that. But the null is 15 dB down. IOW, the null – or its elimination – is so far below the speaker’s natural extension that it’s of no consequence. I’ll be shocked if you can hear a difference down in that range with your speakers or chair moved a foot. You could easily eliminate the null with a subwoofer, which will not be in the same location as your desk speakers and therefore will not have the same response in the 60-100 Hz range.




> Is there anything I should be concerned about when applying EQ to compensate for the environment in a studio settings (as opposed to maybe for home theater)? I don't fully grasp the reasoning, but I've heard/read that using EQ for this purpose can be bad for your sound - maybe having to do with distortions and unintended artifacts that come with EQ.


You might seek some opinions from people at a recording hobbyist forum like the Tape Op Message Board, but IMO most complaints about equalization are based on people using cheap equalizers, and/or now really knowing how to use them properly. Cheap equalizers can add noise and possible even audible distortion (if it’s a _really_ cheap one). And a common beginner mistake is to over-equalize, trying to eliminate every little ripple in response. Generally, all that’s needed is to precisely smooth out the most egregious peaks and troughs to deliver audibly smooth response.

And you might ask yourself, is properly EQing the speakers any worse than EQing the individual sources you’re recording, or the overall mix, to compensate for your speakers (which is what you’ve been doing, if your mixes have been turning out bass and treble heavy)?




> Also, if EQ is OK to use here for correction, it seems like the target is to flatten the overall trend of the graph line. In this case, probably some kind of shelf @ 2kHz may work to compensate for the high-end rolloff. Does that seem right to you based on what you see here?


Perfectly flat response sounds bad to most people; you might give my house curve article a read (see my signature). In your case, the biggest problems that will be audible are the broad plateau between 1-3 kHz and the spike in the 7 kHz range. These could be precisely eliminated with a good parametric EQ. At that point if things in the upper range still sound “soft,” you could apply a broad shelving filter to lift the highs a bit.

Alternately, for comparison you might try measuring the speakers in another environment, say on a stand in your living room. If for instance, the 7 kHz bump no longer shows up, it might indicate that something in your mix situation is causing it, like perhaps a reflection off the desk. 

Regards, 
Wayne


----------



## gdereese (Jul 28, 2012)

> Alternately, for comparison you might try measuring the speakers in another environment, say on a stand in your living room. If for instance, the 7 kHz bump no longer shows up, it might indicate that something in your mix situation is causing it, like perhaps a reflection off the desk.


I had my speakers angled downward a bit, since I had them sitting a bit higher than my ears. However, after doing some re-measuring of my ear/head height at mix position, I found that the downward angle was not necessary. After adjusting the speakers to sit level/parallel with the desk, I took another measurement:









As you can see, the higher end flattened out a bit. Based on that, maybe there was either some reflection happening off the desk that was causing cancellation, or maybe even due to being deadened by the carpet (since it was pointed a bit downward before)?

It also looks like my curve is getting a bit closer to the response curve of my speakers, which I suppose means that I've made adjustments for the better. Am I correct? I understand that I may need EQ to get a more ideal or flat response overall, but I am reasoning that the closer my measurement is to the response graph for the speakers, the more I have removed the room from the equation.


----------

