First REW Analysis - Voiceover Studio

[jrkaiser]

All traps and gobos are done... I'll have more than I need... treatment is underway. The gobos are in place effectively cutting the room in half. Still need to put bass traps and cloud in position.

The room analysis was done with Room EQ Wizard from www.hometheatershack.com and a Behringer ECM8000, along with a Radio Shack SPL Meter.

It looks like I've got a couple of room mode problems in the under 100 hz range and a couple of things that will need attention at 500 and 600 hz.

More on this project here...

http://www.flickr.com/photos/jrkaise...7617280297733/

BEFORE ANY ADDITIONAL TREATMENT 15-200



BEFORE ANY ADDITIONAL TREATMENT 15-200



BEFORE ANY ADDITIONAL TREATMENT 15-1500



AFTER GOBO PLACEMENT 15-200



AFTER GOBO PLACEMENT 15-200



AFTER GOBO PLACEMENT 15-1500



ROOM ANALYSIS MIC IN POSITION



CUTTING THE ROOM IN HALF WITH GOBOS



BEHIND MIXING POSITION

[brucek]

Looks good jrkaiser.

Some REW tips: You're measuring quite high, (or you're not using the Calibrate routine).

Usually 75dBSPL is a good target to use for measuring. Once you've finished running the Check Levels routine with a 75dBSPL level set, run the Calibrate routine. This will sync the REW SPL meter with the real SPL level at the listening position.

Once you've done that, the trace of your measurement will be around the target line of 74dB. You presently have your target set for sub, but should be changed to full range to be be useful.

Also note that unchecking the meter and soundcard cal boxes removes the visibility of those lines to unclutter the REW display, leaving only the target line.

ETC plots are also quite useful for determining any reflections. The distance tool can be used to quickly find the reflection distance.

brucek

[jrkaiser]

Thanks for the reply... glad to hear I am on the right path... I did run through the calibration, however, when measuring SPL I didn't realize I should adjust the volume level down versus typing in my SPL into REW... I'll take note of that next time and I need to go back and re-read the help file again anyway.

Bruce, I really appreciate all of the insight.

Did you notice anything that should be done in this room or the measurement mic placement to get better results?

What a great peice of software and a very giving group of people here at the Home Theater Shack.

Justin

[brucek]

when measuring SPL I didn't realize I should adjust the volume level down versus typing in my SPL into REW

The idea is that when you run Check Levels, the sound systems volume is adjusted so that the listening position is at 75dBSPL with a hand held SPL meter. Then the REW input level is set to about -12dB. Then click finish. Then to ensure that REW's SPL meter and the real SPL meter match, you run the Calibrate routine. It will use the same band limited pink noise as the Check Level routine, so the level should be around 75dB.
Once that's set, you don't alter the system level again and all your measurements will be at 75dB.

It's a good level to measure at. You'll find that you can evaluate the waterfall easier when the measurement level is at 75dB. Then you can get an idea of the decay time of your signal to below room noise (~<45dB). Looks like you're in good shape with that though. It's a bit more revealing also if you switch the waterfall plots to LOG from LIN. Use the Freq Axis button in the top right corner of REW to switch.
Then take a measure at 75dB and look at your LOG waterfall with a 600msec time base and see how it looks.

Did you notice anything that should be done in this room or the measurement mic placement to get better results?

Your best bet for acoustical advice is in our Acoustics Section. There are some smart guys over there that know a lot more about treatment than I do.

My only suggestion (and you may have already done this), is that when you're measuring for a studio and almost near-field when at your mixer board, I would sit in the chair when I take the measurement. Your reflective chair may offer a different response than when your body is in position. Somehow get the mic to be right where your head is located while your sitting there.

Your response is quite impressive though. the only decay problem appears in the waterfall around 40Hz (room mode). Not much you can do with that though. EQ (as I understand) is frowned upon in studio work. Positioning of speakers and listening position are out of the questions as a studio mixing chair and monitor placement doesn't have the latitude for positioning like an HT application.

Also take a look at Energy Time plots (ETC). It will show you if you have any bad reflections that occur at the mic position. You can use the distance tool to show the distance.
Do a full range sweep measurement (i.e. 0-15KHz) and then examine the ETC plot for reflections which might occur after the main impulse hits the mic (the first large spike). Then you can position the cursor with the left mouse over the main bang. Then press and hold down the Ctrl key and sweep the mouse while holding the right mouse button. It will read out in feet (very useful). Now you can decide where the main signal may have reflected from to produce that second spike reflection (if there is one).

Here's an example below. The large spike is the main measurement sweep hitting the mic. The next spike is a bad reflection. The distance tool shows it's 2.5 feet further to travel to get to the mic. It could be a wall directly behind at 1.25 feet away, or a side wall that made the signal travel that much further to reach the mic. Now place a treatment at those spots and see if the reflection goes away.
I think you get the picture.




brucek

[jrkaiser]

Bruce, again, thank you. I'll take your suggestions and incorporate them in the next analysis after I get the bass traps and rest of the panels in place. It's also probably a good idea, as you suggested to make the measurements with me in the chair as my large body mass could also have an effect on the results.

[jrkaiser]

OK, I think I'm getting the hang of this fantastic software...

We had a chance to hang the cloud yesterday, hung the Panels about 4" off the wall as well... Unfortunately due to the layout of the room using these specifically as Bass Traps will not work, so I'll have to create 3 or 4 simple Tube Traps...

If you have any other thoughts, I'm all ears...

Full size photos and complete documentation on this project from start to finish is available at the following location...

I should be back to voicing in this studio, after some final cleanup, next week. I'm not sure what it will sound like except for the fact that the reverb when clapping is a lot less, and the feel and sound seems to be a bit more intimate... I've learned quite a bit doing this project and hope it helps you...

BEFORE/AFTER COMPARISON - BEFORE IS RED - AFTER IS PURPLE





WATERFALL AND DECAY





FINAL TREATMENT





THE CLOUD IS UP - MAIN MIXING LOCATION



BEHIND MAIN MIXING LOCATION - CLOSET ON LEFT - ISO BOOTH ON RIGHT



CUTTING THE ROOM IN HALF WITH THE GOBOS



ENTERING STUDIO FROM OUTSIDE



LOOKING INTO WHERE THE STUDIO IS - IT'S UGLY AND NEED TO FINISH THIS



OUTSIDE ON THE RIGHT - GARAGE ON THE LEFT

[liyuthcw]

Nice one

[jrkaiser]

Thank you. My pride and joy... I've put a lot of work into this... always tweaking though.