3 questions concerning speaker alignment (using room eq wizard)

[Mischdepp]

Hi,
I am in the process of calibrating our MTRX Studio /DADman 5.1/Stereo setup using room eq wizard.
I have read the very good tutorials on the production experts website - these helped a lot but there are some questions left:

1:
For a relatively small room like the one I am trying to align right now (80 cubic meters /2.800 cubic feet) with 2 Seats at mix position (me + director) how many measurements with different mic positions should I do and how far should I go in the back of the room?
Some say the more the better but I also read suggestions that prefer to measure only two or three positions close to the mix position saying that averaging too many measurements will compromise the results. I tried two approaches (10 positions all over the room vs 3 positions close to mix position) and the 3 position measurements resulted in eq profiles with a significantly less number of filters needed in MTRX...

2:
I have set up separate 5.1 monitor profiles in DADman - one for TV and one for theatrical with the surrounds lowered by 3dB. Is it necessary to do separate measurements for the two profiles?

3:
Am I right in thinking that I will have to recalibrate speaker levels after applying the EQ correction to the Outputs in MTRX Studio?

[Top Jimmy]

To my taste, up to 6 correction filters makes an improvement. Get into 8 or more and I don’t like what it starts to sound like. I stick to 3-5 measurements in the expected listening area and am pleased by the results.

Just changing the level of the surrounds doesn’t necessitate a new set of measurements. If you apply the same curve to all speakers then you only need to adjust the overall reference listening level. Personally, I would take corrections measurements in sections. Center gets one measurement, front left/right gets a measurement, and rear left/right gets a measurement. Of course since different correction curves are being used, this would definitely require a new calibration.

[BScout]

How wide is your room (volume doesn’t matter at your size room) at the mic position.

No for question 2. Speakers are amazingly linear. You’d only have to re-measure if the direct fell below room levels — which at that point the room would be useless for mixing. You aren’t doing this at with 3dB changes.

Yes to question 3. Should be your final step.

[Mischdepp]

Originally Posted by BScout

How wide is your room (volume doesn’t matter at your size room) at the mic position.

No for question 2. Speakers are amazingly linear. You’d only have to re-measure if the direct fell below room levels — which at that point the room would be useless for mixing. You aren’t doing this at with 3dB changes.

Yes to question 3. Should be your final step.

Room width is approx 4.83 meters or 15.85 feet.

Thanks to all for the detailed responses - much appreciated

[Mischdepp]

I made new measurements today using 4 positions for each speaker.

And one more question popped up:

The main and surround speakers are KH120. For TV mixing I decided to go without bass management because I didn't do it in the past and the all mixes translated well.

For Cinema I was planning to activate BM in the corresponding DADman monitor profile
(my idea was 24db/ oct. low pass Linkw.@ LP freq.44 or 46Hz).
When doing so would I measure the L R C Ls and Rs speakers with the sub turned on or off? Also I am not sure if the frequency is right
This is new territory for me cause all our previous interfaces had no bass management...

[BScout]

Measure you subwoofer full bandwidth. Measure you LCR speakers full bandwidth. Use REW's align tool to figure out where to crossover for bass management (it can give you a prediction of what the sum of the two is going to be and you can also adjust phase/delay in the tool to arrive at the correct settings to apply in DADman to avoid a dip or peak at the crossover point.) Dolby goes with a fairly static choice of 80Hz but there is no reason to stick with that. Remember that phase rotation influences both signals so if you are applying a high pass 24dB (4th order) to your LCR and a low pass 24dB (4th order) to your sub, you arrive at a theoretical in-phase situation. If you only do one side of this equation, you can end up out-of-phase and will need to invert phase on the sub. And then with the KH120, which is a ported speaker, you have to consider the phase slope of the port (which is 4th order) if you are crossing over where it is the contributing factor. If you are at 44-46hz, you are definitely in port territory. If you cross at 80Hz you'll be above the port territory and the speaker will be operating as a sealed box so a different phase when applying a HPF. A sealed satellite speaker to a sealed or ported sub is one of the easiest things to align since the math is simple. A ported satellite is a little more involved. But the REW align tool will take the guess work out of it as it is phase-aware when summing the predicted curve.
I suggest reading REW's information on the align tool; they are very good on documentation and instructions.

I would not mess with a different setup for TV vs Cinema for your LCR. If you make your LCR full range using bass management, use it also for TV. There is no advantage in NOT hearing lower frequencies (you just end up sending rumble to people who have good speakers -- something, as a mixer, you should be taking care of and something you can do if you can hear it.)

As for multiple points of measurement, your listening rectangle is pretty small so one to two points is fine vs averaging four. If you are going to be one place and your director is going to be at a different place both in front of your desk, that's as much as you need to average. Adding more points is just making your correction worse for points that won't be in use.

[mgoorevich]

Originally Posted by BScout

Measure you subwoofer full bandwidth. Measure you LCR speakers full bandwidth. Use REW's align tool to figure out where to crossover for bass management (it can give you a prediction of what the sum of the two is going to be and you can also adjust phase/delay in the tool to arrive at the correct settings to apply in DADman to avoid a dip or peak at the crossover point.) Dolby goes with a fairly static choice of 80Hz but there is no reason to stick with that. Remember that phase rotation influences both signals so if you are applying a high pass 24dB (4th order) to your LCR and a low pass 24dB (4th order) to your sub, you arrive at a theoretical in-phase situation. If you only do one side of this equation, you can end up out-of-phase and will need to invert phase on the sub. And then with the KH120, which is a ported speaker, you have to consider the phase slope of the port (which is 4th order) if you are crossing over where it is the contributing factor. If you are at 44-46hz, you are definitely in port territory. If you cross at 80Hz you'll be above the port territory and the speaker will be operating as a sealed box so a different phase when applying a HPF. A sealed satellite speaker to a sealed or ported sub is one of the easiest things to align since the math is simple. A ported satellite is a little more involved. But the REW align tool will take the guess work out of it as it is phase-aware when summing the predicted curve.
I suggest reading REW's information on the align tool; they are very good on documentation and instructions.

I would not mess with a different setup for TV vs Cinema for your LCR. If you make your LCR full range using bass management, use it also for TV. There is no advantage in NOT hearing lower frequencies (you just end up sending rumble to people who have good speakers -- something, as a mixer, you should be taking care of and something you can do if you can hear it.)

As for multiple points of measurement, your listening rectangle is pretty small so one to two points is fine vs averaging four. If you are going to be one place and your director is going to be at a different place both in front of your desk, that's as much as you need to average. Adding more points is just making your correction worse for points that won't be in use.

⬆︎⬆︎⬆︎ A very good advice! I absolutely agree.⬆︎⬆︎⬆︎

[Mischdepp]

Thanks again for the detailed advice!

Back to work

[Mischdepp]

Thanks a lot! When setting up bass management for the TV monitoring, do I have to uncheck the "set 10dB gain on LFE" in DADman and recalibrate the output for the sub?

[Mischdepp]

Originally Posted by Mischdepp

Thanks a lot! When setting up bass management for the TV monitoring, do I have to uncheck the "set 10dB gain on LFE" in DADman and recalibrate the output for the sub?

Ok - I got that one sorted out by myself

The only question still remaining is: when I measure the main speakers in REW - do I measure with the sub switched on and select "full range speakers", or without the sub and select "bass limited speakers" with the settings I set up in DADman?
I tried to look it up in the REW manual but could't find anything...