One more calibration question, where does the SPL go?

[Dumb-Ask]

I just read this statement:

"hold the SPL meter at chest level with the microphone facing up at an angle of approximately 45 degrees at the Center speaker. Keep the meter at arm's length to prevent any audio from reflecting against your body. keep the meter aimed at the Center speaker as you take readings for the Left and Right monitors as well. When taking the SPL readings for the Left Surround or Right Surround speakers, keep the meter at the same angle and position as you did for the front speakers, but turn your body 90 degrees from the Center speaker towards the wall closest to the speaker you are measuring."


This really confused me, up until now I have been keeping the SPL facing the center speaker at 45 degrees to calibrate all my speakers including surrounds.

Unless I did not understand the text above it says that I should face the SPL towards the closest wall while standing at the same spot, is that correct?

It could be a language thing :P

would it be like this?

= speaker
stike =SPL meter





calibrating L?............................................calibrating center ?
------- -------- ............................... ------- --------

stike SPL facing the left wall at 45 degrees .................. stike SPL facing center at 45 degrees

[georgia]

I don't know about anyone else, but I use 5 mics placed in the room and a Time division multiplexer along with a spectrum analyzer to calibrate my rooms. But when I just want to check a room, I use my SPL meter... I hold it out a bit in front of me exactly straight out pointed directly at each speaker in the front, as I check each one, one at a time. If i'm doing Ls and Rs with multiple rear speakers on a a channel ,I point it in the general direction of the wall and toward the rear of the room. If it's one rear speaker per channel I point it at the speaker...This always matches the readings well enough for me to verify a room is ok... so it works for me.

cheers
geo

[Dumb-Ask]

Thanks for your answer Georgia.

Just to clarify, if I understand this correctly, which I fear I don't :P
If you were calibrating the left speakr in a streo set up would you stand in the sweet spot where your head should be and point the SPL diagonally at the speaker? or would you move left and then point it straight at the speaker?

I always thought I should be taking the measurement from the sweet spot pointing the spl towards the center, when calibrating stereo I would point it between the left and right speakers to get the phantom center measurement

[Dumb-Ask]

How do others do it? do you stay at the same spot and just move your arm towards the speaker when using an SPL?

[Bill@AudioVision]

I mount my meter on a camera tripod and sit low, out of the way during measurements. I average two readings, one facing the center speaker and one facing the back wall (180 degrees flipped). The mic is angled up maybe 30 degrees.

[Dumb-Ask]

Thanks bill,

Do you keep the SPL aimed at the center speaker when calibrating only the 3 front speakers or all five? and then do you aim it at the rear wall and only calibrating the 2 back speakers or all 5?
Sorry for the novice questions I'm just completely confused about this issue

[dr.sound]

Originally Posted by Dumb-Ask

Thanks bill, are you referring to stereo calibration or surround?
if I understand correctly your method is to aim the SPL meter to the phantom center and get lets say it reads 87db from the Left and 87db from the right and then you turn the spl to face away from the speakers looking back and lets say you get 83db on the Left and 83db on the right and you average both readings and get around 85db? Is that what you mean ?


Or are you referring to surround? if so do you keep the SPL aimed at the center speaker when calibrating only the 3 front speakers or all five? and then do you aim it at the rear wall and only calibrating the 2 back speakers or all 5?
Sorry for the novice questions I'm just completely confused about this issue

Here is a link to my "Room Calibration for Film And TV" :
NEW UPDATED Room Calibration for Film and TV Post - Digi User Conference

Read it again and think, we are playing 1 Speaker at a time NOT all at once.
We are standing right at the mix position facing the front speakers ,
We then tun facing the rear speakers and play them 1 at a time.
We are STAYING IN THE SAME PLACE just as if we are mixing.

Read it again.

[Dumb-Ask]

Thanks Marti, I actually read it and found it very useful, but English is not my first language and things got a little confusing.

I think that that's how I've been doing it so far apart from turning the SPL meter towards the rear wall to calibrate the Ls and Rs, I always kept it facing forwards the center when calibrating all the speakers ( I calibrate each speaker at a time to 79db).

When you say "We are standing right at the mix position facing the front speakers " If I understand correctly you point the SPL at the center at 45 degrease for calibrating the 3 front speakers?

when you say "We then tun facing the rear speakers and play them 1 at a time" do you turn the SPL 180 degrees flipped as bill says and to get the level of the Ls and Rs?

[mikevarela]

you've got to think that when you mix, sound reaches your ears from each speaker based on the mix position, but if you point the spl meter forward to read the rear speakers then the mic in the unit is being masked by the unit itself.

you point at an angle to offset initial pressure from the cone, hence 45 degrees. I read the paper you were referring to as well. they ask you to point it at a wall of the speaker your reading to approximate what your ears hear.

an spl reading is accurate if it's analogous to the volume that reaches your ears, which incidentally point outwards from your head, not forward like a cat. so you need to mimick this, or directly point the spl meter (45 degrees up) at the cone you're reading... like Georgia said.

and remember to read ONE speaker at a time!
Pink Noise too

[Dumb-Ask]

Thanks mikevarela, I understand the 45degrees upwards positioning thing.

but what is confusing me is what you said "directly point the spl meter (45 degrees up) at the cone you're reading".

Are you pointing the spl to each speaker's cone while keeping it on the same spot. or are you pointing it towards the center for the 3 front speakers and back towards the back wall for the Ls and Rs?


Do I do it this way - A:

L, R, C - SPL facing the center

Ls, Rs - SPL facing 180 degrees flipped (facing the SPL to the rear wall)



Or do I do it this way - B:
I.E. center = SPL straight to center
Left= = SPL diagonal towards the left
Right= = SPL diagonal towards the left
Right surround= = SPL diagonal towards the left surround
Left surround = = SPL diagonal towards the left surround

Thank you

[Bill@AudioVision]

Don't forget, calibration mics are omni - so 'aiming' them should not be that important. Keep the mic in one position as you calibrate all speakers. I flip it around 180 degrees just to get a second reading - but that's my personal style. Just make sure your SPL meter is in mix position.
It really doesn't matter if you are setting up for Stereo or 5.1/7.1... speaker calibration should all be done the same way. I'll also calibrate nearfields to match mains as well (as best as possible)

[soundboy]

Originally Posted by georgia

I don't know about anyone else, but I use 5 mics placed in the room and a Time division multiplexer along with a spectrum analyzer to calibrate my rooms.

cheers
geo

Is there lit on how to do this? I used to EQ live sound systems using a IV Spectrum Analyzer and 30 band graphic EQs for each speaker. Just trying to flatten the response. But I walked around with the analyzer, and tried to get an average and adjust accordingly. How do you set this up with 5 mics and a Time division multiplexer?

[mikevarela]

clearly there are a few ways people are handling it.

I've done mine by reading LCR first - each speaker, one at a time - facing center. Then flip the meter, same height and angle and read the Ls/Rs facing back center.

In this post, others have eluded to facing the meter at each cone when reading. I'm sure that the measurement will likely be ballpark for both methods, so use as you choose.

I know how frustrating it can be to get good information, so when I was doing this, I mixed two different pieces and then burned them to a dvd and began checking in home dvd systems against what i knew was standard volume for a movie.

you can also ask to bring your sessions to another house and try them there to to see if they translate.

main point is however, that you mark your monitor controller at the spl reading that's right for your room and then mix with your ears. then test in several locations and adjust accordingly.

its a trial and error process.

read Marti's post though about calibration, it helps

[ggegan]

This is probably going to sound heretical, but for my SMALL personal editorial/mixing room I first calibrate all the speakers one at a time with the SPL meter at exactly where my head would be and pointed front-center at a 45% upwards angle. I don't change the angle for the surrounds. I then load a session of 5.1 printmasters of shows I have recently mixed on large stages and adjust the surrounds from memory so that they feel right.

I find that I have to raise the surrounds about 1.5 to 2 dB to get them to feel correct, which is odd because when I discussed this with my friend who has a similar setup - small room but with different monitors, he feels that his surrounds are too loud using similar calibration methods.

I use Sky System One monitors, which to my ear have a less hyped high end than my friend's monitors, and I mount them right side up and pointed only very slightly down so that the tweeters are off axis. To me, this mimics what I hear on a large feature stage. My friend mounts his upside down from the ceiling and pointing more towards his mixing position, so the tweeters are lower and more on axis. I can only surmise that even though the SPL is the same, much of the perceived loudness of the surrounds has to do with the nature and dispersion of the tweeters.

[Jesse Peterson]

This is something I've been thinking about lately.. glad this thread is here

so in a theater, the rears are set to 82 vs the fronts a 85...

In a smaller room, people calibrate lower since you perceive loud sounds as louder when you are closer to the speakers.. is this the same reason why the rears on a dubstage are calibrated to 82? is this 82 due to proximity and perception of loudness?

If you have a sound in the center calibrated to 85, and pan it to the rear calibrated at 82.. do you perceive it to be the same level?

If yes, would it make sense for a smaller room to find their magic number for the front with experimentation and earball it in the rears?

[ggegan]

Originally Posted by Jesse Peterson

This is something I've been thinking about lately.. glad this thread is here

so in a theater, the rears are set to 82 vs the fronts a 85...

In a smaller room, people calibrate lower since you perceive loud sounds as louder when you are closer to the speakers.. is this the same reason why the rears on a dubstage are calibrated to 82? is this 82 due to proximity and perception of loudness?

If you have a sound in the center calibrated to 85, and pan it to the rear calibrated at 82.. do you perceive it to be the same level?

If yes, would it make sense for a smaller room to find their magic number for the front with experimentation and earball it in the rears?

I always figured that the reason the surrounds are calibrated 3dB lower was to compensate for mono material being played back in LS and RS simultaneously, which has an additive effect on the volume.

[Jfriah]

Yes, one should CALIBRATE with proper omni pattern calibration mics into an RTA (spectrum analyzer) and if you have them, adjust the 1/3 band EQs with your pink noise reference.

It is "fairly technical", and only THEN can you 'ballpark check it' with an SPL meter. Once your room is calibrated and balanced, THEN you can check your overall SPL...

And, yes, I'm also an SPL-meter-on-tripod kinda guy. I angle it up 45degrees, pointing front and then for surrounds, turning 90degrees to the side.

Read read read and good luck.

(cough cough especially with your LFE/subwoofer, cough)

Jeff

[georgia]

Originally Posted by soundboy

Is there lit on how to do this? I used to EQ live sound systems using a IV Spectrum Analyzer and 30 band graphic EQs for each speaker. Just trying to flatten the response. But I walked around with the analyzer, and tried to get an average and adjust accordingly. How do you set this up with 5 mics and a Time division multiplexer?

I place 1 mic literally clamped to the mixing chair I sit in. Then one in front toward the left and 1 in front toward the right. One behind to the left and one behind to the right. like the "5" on a set of dice. ( or slightly adjusted to compensate for room overall placement ). The 5 mics are connected to a Time division multiplexer that sends the multiplexed signal to a spectrum analyzer ( but the "time" is very very fast )... to the analyzer it appears to be 1 signal from 5 mics creating an overall room response... Much more accurate than taking multiple "reads" around the room. THe rest is the same, one speaker at a time, volume adjustment, eq adjustment, rinse/repeat... the resulting curve is much closer to reality than doing a single mic. It allows for the ROOM to be calibrated and not just a small sweet spot. Remember the mix position and the seats for those pesky clients must sound the same to assure everyone is hearing the same mix. ( Oh how I remember trying to work in a room once, where the mixer heard one thing and the client another... that type of situation just sucks. )


Dolby does it the same way when they test a room. ( that's where I learned how to do it a number of years ago )

cheers
geo

[soundboy]

I wish I had a time division multiplexer back in 1990 when I was working in theater! It would have saved a lot of time! Thanks for the info.

[mikevarela]

Georgia, quick question.

what program/hardware do you use (RTA - as mentioned above).

-----

I'm also wondering about room eq. are the users here using hardware eq's in the monitor chain or some software equivalent to correct for modes. I'm aware of genelecs system but wondering about users on other systems. If hardware, what have you liked.. I'm interested in tuning my studio, but don't want to put any more strain on my cpu than I have to.

thanks

[soundboy]

I'm using a Soundweb for my room EQ, but any quality 30 band EQ will do. You just need 1 per monitor.