Room measurements

[amirm]

Here is the USB mic I talked about: http://www.daytonaudio.com/index.php/test-measurement/umm-6-usb-measurement-microphone.html

And place to buy it for $88: http://www.parts-express.com/pe/showdetl.cfm?partnumber=390-808

For a few dollars more, you can get a more precisely calibrated one: http://cross-spectrum.com/measurement/calibrated_umm6.html

The noise level on it is not great and it has some distortion but all of it is well below what we care about in room measurements. It comes with a long USB cable so you can right away with measuring things.

 

[mep]

I wonder if everybody would measure a dip around the 63 Hz range? It looks like your dip is some 15dB from your other peaks. Maybe the microphone has a dip in this region.

 

[Steve williams]

Likely if you point it differently you would get entirely different high frequency response.

I did and you don't. Same frequency response

 

[Steve williams]

I am interested in that calibrated Mic Amir. How does it differ from the uncalibrated for $2 more? Seems you get a file to download with it or am I misreading

 

[amirm]

The one from Dayton/Parts express comes with a single measurement file that you download. The one from Cross Spectrum is more precisely calibrated and comes with three files for each orientation of the mic (pointed toward the source, and up for example). So I would pay the extra and get it from Cross Spectrum. That said, I was in a hurry and got one from parts express .

 

[rockitman]

I wonder if everybody would measure a dip around the 63 Hz range? It looks like your dip is some 15dB from your other peaks. Maybe the microphone has a dip in this region.

maybe it's the result of bass trapping ? I need to take more measurements to see if they are consistent.

 

[JackD201]

Too high Jack? Does it matter? The pink noise was recorded at -20dB.

I was thinking too low but then again there is no direct formula to convert FS to dB. Is there a way to change the scale to dB? FS (Full Scale) is a very different reference point that I associate with noise inside the electronics and not acoustics. You should be measuring somewhere between 80 and 85dB (not dBFS) as a reference for your room response (common range of mixing monitor calibration). Too low and what you're measuring will always be jagged since the ambient noise will figure more prominently IIRC. Could you do a baby experiment Mark and show a screenshot with the pink noise not playing at all? IN other words a snapshot of your room's noise floor.

 

[microstrip]

REW (free) + an USB Soundcard with phantom power such as the M-Audio or the Tascam US-122MkII (75 to 140) + a calibrated behringer ECM-8000 (80) combo is the real deal. It will not take more than a few hours to get result with and improve many systems.

Happy Easter people!

Frank,

I agree on your appreciation of REW coupled with inexpensive hardware. But it will take more than a few hours until one is able to extract useful information from the system. These measurements must be interpreted using more information from the room, including the dimensions, speaker placement and at less a map of the high and low pressures at room modes such as given by the room eigenmode online calculator http://www.hunecke.de/en/calculators/room-eigenmodes.html.

IMHO a single isolated non documented measurement has very little value and can be highly misleading - you have to take many in different situations and placements, learn about your room and "feel" it. And in this comparative work you will find that the facilities of a good software such as REW and others I am forgetting really make the difference.

 

[mep]

I was thinking too low but then again there is no direct formula to convert FS to dB. Is there a way to change the scale to dB? FS (Full Scale) is a very different reference point that I associate with noise inside the electronics and not acoustics. You should be measuring somewhere between 80 and 85dB (not dBFS) as a reference for your room response (common range of mixing monitor calibration). Too low and what you're measuring will always be jagged since the ambient noise will figure more prominently IIRC. Could you do a baby experiment Mark and show a screenshot with the pink noise not playing at all? IN other words a snapshot of your room's noise floor.

Here you go Jack:

 

[rockitman]

Here you go Jack:

View attachment 8999

Hey Mark, after you pause the graph, press the home button and the on/off switch simultaneously for a second and the screen shot is captured in Camera Roll like in my image above.

 

[JackD201]

Thanks Mark. Looks like I'll need to download this App just so I can play with it. I'm having a tough time getting my correlation with FS. It's like being told 36-24-36 in millimeters. Lol!

Just two more if you don't mind. Pink noise and noise floor but this time without the phone's case on.

 

[mep]

Jack-my phone is charging as it's deader than a door nail right now. I will post as soon as I can.

 

[Steve williams]

Pink noise and noise floor but this time without the phone's case on.

I've done this and the results are unchanged as they are regardless of which plane you hold the iphone in

 

[mep]

Guess I don't need to take the other set of measurements then.

 

[Steve williams]

You should in order to confirm what I found.

 

[KeithR]

Took one both from this program and my preferred one- Audiotools. I find the latter much, much better fyi. It's 49.99 though.

 

[KeithR]

I also used Audiotools to set 80-81dbs as my level for the pink noise tests.

 

[Ethan Winer]

You can see some pretty big suck outs at 57.75 Hz and 145.8 Hz.

If you display without the 1/6 octave averaging, you'll see a better representation of the true response at low frequencies. It will look worse! But it will be much closer to reality.

--Ethan

 

[KeithR]

Mep- I should add, if you do not have any room treatment and opt to get some, prepare yourself for a treat. i can't tell you the amount of clarity, detail, and imaging that one gets when doing some basic things---and I have no idea how to measure that on any software. my guess is since bass trapping is involved (i have one large floor to ceiling trap and numerous ceiling clouds), that mids and highs are much more clear. so when you say "my room sounds great"- i think that your opinion will change quite a bit after experimentation (which is now cheap thanks to GIK, Realtraps, etc)

i was at a buddy's house this weekend with the same speakers, but no treatment. some tracks on the new How to Destroy Angels were so boomy that they were practically unlistenable there. it was amazing how much more i could hear once i got home- its as big as a speaker upgrade imo.

 

[mep]

Keith-I have posted numerous pictures and videos of my room and I have a bunch of room treatments hanging in my room.