Some guidance please

[BritInVA]

New to REW......so please go easy on me.

- REW v4.11 b1086
- Toshiba Tecra laptop running Windows XP
- M-Audio Mobile Pre USB Souncard
- Beringer ECM 8000 mic (calibrated)

First after researching I beileve I calibrated soundcard. Loopback from Output 2/R to Input Ch2. After running thru calibration steps I get following.



Which looks like that in help......so far so good

Next I ran the check to see if calibration was succesful but unsure if this is the correct result as its very different to that in help.



Appreciate if someone can confirm before I continue.

Thanks,
In advance.

Cheers,
Mark

[brucek]

Next I ran the check to see if calibration was succesful

I don't see any problem.

You've got the target, soundcard cal and corrected checkboxes selected, so that adds confusion to the graph, but your correct straight blue line is there, as it should be...

You should be using a vertical scale of 45dB-105dB.

brucek

[BritInVA]

brucek - Thanks.

Thats part of my confusion. in the help it does not show or say what should or should not be checked.

Onto the next step.

[brucek]

in the help it does not show or say what should or should not be checked.

The checkboxes only effect what is shown on the plot. That's it.

If you want to see it, you check it...

brucek

[Anthony]

Yep, looks fine to me.

Bruce and I did a loopback check with a voltage divider to check line-out to mic-in to see if there was a difference. Almost none. Something like 1/4 dB at 20 Hz and spot on for the rest of the spectrum.

So that cal file you did for your MobilePre is probably good enough. You can also enable loop-back on Channel 1 and use a effects cord (1/4" tip-sleeve to do Ch 1/L to Ch 1 Line in). That loop replaces the calibration file and is theoretically more accurate in case anything changes over time (unlikely). But you'll get good results either way.

Happy measuring!

[BritInVA]

OK......next

Removed loop and connected Output R/2 to the Aux on my AVR (Denon 2807) using splitter at AVR to L&R.

Connected Mic to Mic Ch2 and turned on Phantom power.

I've run thru checking levels using Speakers - using RS Analod SPL meter set AVR volume so reading was 75db.

Then calibated SPL Reading also to 75db.

And them made measurement during which got follow message



And following graph



If I change the Sweep Level or AVR volume it says I need to "Set Target Level". Now does that mean I need to take another SPL reading and then change the calibration reading to this value?

Thanks,
Mark

[salvasol]

BritInVA wrote:

If I change the Sweep Level or AVR volume it says I need to "Set Target Level". Now does that mean I need to take another SPL reading and then change the calibration reading to this value?

I remember reading about a trick ...I think you just increase the volume in the AVR and set the target to 75db (even if your reading on the SPL is higher), then do the check levels first to see if you still get the same message about levels ...if not, do the new reading

[BritInVA]

OK so I found the "Target Settings" panel

But still unsure what I need to do.

[salvasol]

BritInVA wrote:

OK so I found the "Target Settings" panel

But still unsure what I need to do.

Just set the target to 75db ...then do the check levels and look for an error message, if not , you're set to measure

P.S.: If you're measuring sub response only, post the graph with this settings: 45db-105db and from 10Hz to 200Hz ...for full frequency the same 45db-105db and from 10Hz to wherever your measuring.

[BritInVA]

So to be sure I'm understanding this right.

- Increase volume on AVR
- Set Target level to 75db
- Run Check level to see if error persists

[salvasol]

BritInVA wrote:

So to be sure I'm understanding this right.

- Increase volume on AVR
- Set Target level to 75db
- Run Check level to see if error persists

Yes.

But before increasing the volume....What target did you have before you found the "Target setting panel"??? ...75db???...maybe you just need to set the correct target and don't need to increase volume

[BritInVA]

Target was already at 75db.

I increased volume on AVR so SPL was 80db.

Rerun measurement and no message and get following.



Now to understand what it all means.

Appreciate any input on how good or bad this looks and what I should be doing next.

Cheers,
Mark

[salvasol]

BritInVA wrote:

Now to understand what it all means.

Appreciate any input on how good or bad this looks and what I should be doing next.

Couple of suggestions:
1) Use 1/3 smoothing.
2) Change settings 10Hz to 24KHz.
3) Use the save graph icon, I think the standar size is 800x800 (I think is below the graph)

[BritInVA]

Like this?

[brucek]

Mark,

It's normal practice to first check your subwoofer alone, and then add the mains to setup your crossover region, then do a full range if you require it. When checking subwoofers, remove the mains, and use the subwoofer test signal.

For subwoofers, always use the standard Vertical graph axis of (45dB - 105dB) and the Horizontal graph axis of (15Hz - 200Hz) using the Graph Limits button in the top right corner of REW.

For full range, use the standard Vertical graph axis of (45dB - 105dB) and the Horizontal graph axis of (15Hz - upper limits you desire. i.e 20KHz).

For full range only, enable smoothing to eliminate the comb filtering. Use a 1/3 octave smoothing.

There is a floppy icon in the bottom left hand corner of the REW screen. Please use it to create your 800 bit wide graphs. You do not need to post the entire REW page.

Be sure you have the microphone calibration file loaded.

brucek

[BritInVA]

brucek wrote:

It's normal practice to first check your subwoofer alone, and then add the mains to setup your crossover region, then do a full range if you require it. When checking subwoofers, remove the mains, and use the subwoofer test signal.

Bruce,

Thanks.

1) So do I physically disconnect the mains from the AVR?

2) Do I go into AVR and increase the current crossover (think its set now to 80Hz)

3) Do I set REW to use subwoofer test signal in Settings --> Soundcard or somewhere else.

Sorry if I appear dim (which I'm feeling right now).

Cheers,
Mark

[Cathan]

I for one appreciate all of your questions, Mark. I feel like I'm learning this right along side you.

[salvasol]

BritInVA wrote:

1) So do I physically disconnect the mains from the AVR?

Yes

2) Do I go into AVR and increase the current crossover (think its set now to 80Hz)

No, unless you'll be using something different, set it to the crossover you'll use.

3) Do I set REW to use subwoofer test signal in Settings --> Soundcard or somewhere else.

Yes, on REW you have two options: Speaker or Sub test tones...use Sub.

Don't worry about asking questions....I'm not an expert in REW, but I recall a little what I did when I use it the first time

[BritInVA]

OK, disconnected mains.

Reset level using sub signal to 75db but when running had low headroom so ended up increasing volume so was nearer 90db.

Here is resultant graph



Cheers,
Mark

[brucek]

Reset level using sub signal to 75db but when running had low headroom

And after the 75dBSPL was set at the listening position, did you then set the REW Input level to -12dB? And then run the Calibrate routine? Then Measure?

brucek

[BritInVA]

brucek wrote:

And after the 75dBSPL was set at the listening position, did you then set the REW Input level to -12dB? And then run the Calibrate routine? Then Measure?

brucek

Hmmm...now I think I may have forgot that part.

I'll re-run tomorrow. Having PC blue-screen-of-death issues and my daughter has friends over for a movie tonight so I need to tidy room.

So back tomorrow.

Thanks everyone for there help.

Cheers,
Mark

[BritInVA]

Back to testing.

- Loaded yesterday's Soundcard cal file (assume don't need to redo each time)
- Loaded the mic cal file
- Disconnected mains
- Used Check Levels, AVR vol and SPL meter to get 75db at mic position
- Calibrated SPL

Run measurement but was getting headroom pop-up so increased AVR vol in steps (leaving target level at 75db).

This what I was seeing

SPL Meter Headroom
75db --------- 29.6
80db --------- 26.2
82db --------- 22.8
85db --------- 20.1
88db --------- 18.1
90db --------- 16

I'm I doing anything wrong here?

This is graph with SPL at 90db



Thanks,
Mark

[brucek]

Used Check Levels, AVR vol and SPL meter to get 75db at mic position

And, as I said above, did you .... after the 75dBSPL was set at the listening position, did you then set the REW Input level to -12dB? And then run the Calibrate routine? Then Measure?

[BritInVA]

Don't know if this info about my room is useful

Equipment
- AVR: Denon AVR2807
- Front Speakers: Ascend 340 SE
- Subwoofer: HSU STF-2

Room Treatments
- Screen Wall: Acoustic cotton in corners and 2" OC703 for remainder of area (screen area also now 2" OC703)



- Side Walls: Fabric covered 1" OC703 from 8" to 54"
- Oak panelling and bar at rear (sure this hurts room but looks nice)

Finnished Room Pictures



To sub is located in the right corner of screen wall, not really any other options for placement other than left corner.

Cheers,
Mark

[BritInVA]

brucek wrote:

And, as I said above, did you .... after the 75dBSPL was set at the listening position, did you then set the REW Input level to -12dB? And then run the Calibrate routine? Then Measure?

Do you mean the Sweep Level? If so that is -12db