Questions on REW..

[jakelm]

Hi all, newbie here. Just wanted to say, what a great forum , with tons of info.

Question:

I think I am doing something wrong in regaurds to REW. I cant seem to get it to read over ~8khz. I have calibrated the mic and sound card. When I run a sweep with the sound card it reads fine to 24khz, but when I switch to the mic and run it for my HT, it drops suddenly after~7khz. What am I doing wrong.


Here are some graphs:

[jakelm]

I have then adjusted the subs xover to fix the 60-70HZ drop. Also adjusted the tilt on the HK 635.

These 2 graphs are WITH the HK's ez/eq

Here is another pic:

[jakelm]

I made sure I was running full range and speaker, not sub. I dont understand. My mic is RS spl meter, using the c weight spl calibration

[JohnM]

Are you using a mic input? Some are only sampled at 16kHz, so they have no response above 8kHz. You need to use a line input. Do not rely on the RS meter above 1kHz or so, it typically has a pronounced bump in its response at around 5kHz or so and is generally poor above 1-2kHz. Make sure the meter is set to C weighting and not A weighting.

[jakelm]

JohnM wrote:

Are you using a mic input?

Yes I am. With mic input in setting menu of REW also.

Some are only sampled at 16kHz, so they have no response above 8kHz.

The mic or mic input?

You need to use a line input.

Hook the RS mic to the line input on the sound card?

Do not rely on the RS meter above 1kHz or so, it typically has a pronounced bump in its response at around 5kHz or so and is generally poor above 1-2kHz. Make sure the meter is set to C weighting and not A weighting.

I guess thats the bump I see after 2khz in my graph. The c weighting is on.

I also have my HK mic. For Ez/Eq auto calibration. How would this mic work out is used with REW?

I noticed that all mics are left channel only, should I "y" split it to a stereo jack or leave it left channel? Being I will use the Line input instead of the mic input.

I followed the direction pretty well, I did not read anyone else having this issue. Is it just my PC mic input?


Jake

[brucek]

Hook the RS mic to the line input on the sound card?

Yes, the RS meter outputs line-level signals. Mic-inputs are not suitable.

The c weighting is on

You need to go to our download section and get the calibration file for the specific RS meter you are using. RS meters are not reliable above 1KHz.

or leave it left channel?

Use left or right, it doesn't matter, since you select the channel in REW to match the channel you have it connected to.

I followed the direction pretty well, I did not read anyone else having this issue. Is it just my PC mic input?

The REW HELP FILES tell you to use only a line-in..........
A soundcard (internal or external) which supports full duplex operation (simultaneous replay and recording) with line inputs and outputs. Inexpensive soundcards are typically adequate, a reference measurement is used to remove the soundcard's frequency response from the measurement. Examples of USB soundcards which have been found to work well are the Soundblaster MP3+, Soundblaster Live! 24-bit USB External and the M-Audio MobilePre-USB. Note that microphone inputs are NOT suitable and should not be used.

brucek

[jakelm]

Thanks a bunch....

I did download the RS calibration and it did work very well for the lower end Fr's.

I must have misread that part in the Help file. Sorry..

Thanks again..

How does the Fr responce in the graphs look? Any pointers?


jake

[brucek]

Yeah, hook it up to the line-in and do your calibration, and then I'd like to see a 15Hz-200Hz graph if possible..

I would say that you probably had some crossover cancellation that could be fixed by adjusting the subs phase control. Do some tweaking and re-measuring for that if possible. Sometimes a bit of sub distance trim in the receiver helps there also.

brucek

[jakelm]

brucek wrote:

Yeah, hook it up to the line-in and do your calibration, and then I'd like to see a 15Hz-200Hz graph if possible..

I would say that you probably had some crossover cancellation that could be fixed by adjusting the subs phase control. Do some tweaking and re-measuring for that if possible. Sometimes a bit of sub distance trim in the receiver helps there also.

brucek

Is there a reason for just up to 200hz? Would a full spectrum run give the same reults for 0-200hz?

Also , when setting the sweep, I put in 22kz top end, for the extra headroom. Does this effect the measurement? Instead of stopping the sweep @ 20khz?

When I took the measurements, it was pretty late last night. I went through my HK xover settings, everything looked ok. Then checked my sub settings on the sub. I had the xover on the sub turned all the way to 40hz. The wrong way!!! I turned it back up to where it it supposed to be (all the way up since I am using my HK's xover). I did not re run the calibration because it was pretty late.

I will re run it again and post what I have.

Please ecxuse my ignorence, but how can you put up multiple measurements on a single graph. Instead of flipping back and forth from one graph to another?

[mswlogo]

brucek wrote:

A soundcard (internal or external) which supports full duplex operation (simultaneous replay and recording) with line inputs and outputs. Inexpensive soundcards are typically adequate, a reference measurement is used to remove the soundcard's frequency response from the measurement. Examples of USB soundcards which have been found to work well are the Soundblaster MP3+, Soundblaster Live! 24-bit USB External and the M-Audio MobilePre-USB. Note that microphone inputs are NOT suitable and should not be used.

brucek

Sorry if this is slightly off topic.

I have bought so many of these different cards for getting audio in and out (both analog and digital). The SoundBlaster ones were just horrible. For this application they might be ok. But ASIO support was joke. Getting Digital in and out without resampling was impossible on the soundblaster (Could not get encoded digital in and out without corruption). Both M-Audio and Soundblaster drivers were extremely buggy, including blue screens (which you rarely see these days). Not to mention the junk software that gets installed.

Both the EMU 044 and TASCAM 144 are excellent !! Vista support on both. XLR Phatom powered Mic inputs and LineLevel inputs (You can hook RS SPL or ECM 8000 directly). I can't stress this enough. The local guitar center dropped all low end M-Audio and SoundBlaster because of too many problems. I'm not saying you can't get the others to work and things can change in a year. But these other products are so much more stable and better quality for around the same price. The EMU can run as a standalone 24/192 ADC and DAC or as standalone analog preamp. TASCAM can act as standalone Preamp too. I have not tried TASCAM as a standalone DAC/ADC yet.

[jakelm]

Being I have 2 subs. The sub nearest the listening position, I have the xover turned all the way down as to not hear the midbass. I am just adjusting the "main" sub in the far corner, of the rrom, for blend. What do you think?

[jakelm]

I am using an intergrated Sound Max card from my ASUS mobo. Works better than my older SB Live.

[brucek]

Also , when setting the sweep, I put in 22kz top end, for the extra headroom. Does this effect the measurement? Instead of stopping the sweep @ 20khz?

From the HELP FILES:

Set the End Freq to the highest frequency at which you wish to measure. The sweep will span the range from 0Hz to twice the frequency you set (with an overall limit of half the soundcard sample rate) to provide accurate measurement for the selected range

Please ecxuse my ignorence, but how can you put up multiple measurements on a single graph. Instead of flipping back and forth from one graph to another?

From the HELP FILES:

All Measured TAB
This group shows the measured responses for all measurements on the same plot. The "Separate the traces" check box offsets each trace downwards from the preceding trace to make it easier to distinguish individual features when the traces are at similar levels.
It allows up to eight traces on one graph.

I have the xover turned all the way down as to not hear the midbass. I am just adjusting the "main" sub in the far corner, of the rrom, for blend. What do you think?

Yeah, a bit tricky when two filters are used for one sub - one from receiver crossover and one in the sub itself. Then you are trying to mix two subs with different frequency ranges in the same room - tricky. Usually when a sub is crossed at 80Hz, it's not localizable, although anecdotal evidence may dispute that somewhat. Have you tried an overall 60Hz cross? (perhaps your mains won't extend low enough to support it though).

I'd certainly start by integrating the single main sub and then begin to increase the level of the close sub and take measurements to check what's happening.

brucek

[jakelm]

brucek wrote:

From the HELP FILES:

Set the End Freq to the highest frequency at which you wish to measure. The sweep will span the range from 0Hz to twice the frequency you set (with an overall limit of half the soundcard sample rate) to provide accurate measurement for the selected range

So if I set the end Freq limit to 22khz, the sweep will cover all the way up to 44khz??

I have no idea what my sample rat elimit is on my soundcard. I saw the rate was set for 48khz. I guess thats half of my soundcard...

From the HELP FILES:

All Measured TAB
This group shows the measured responses for all measurements on the same plot. The "Separate the traces" check box offsets each trace downwards from the preceding trace to make it easier to distinguish individual features when the traces are at similar levels.
It allows up to eight traces on one graph.

Same plot? I cant take a measurement from 0-200hz, then another measurement from 200-22khz and put them on the same graph?

Yeah, a bit tricky when two filters are used for one sub - one from receiver crossover and one in the sub itself. Then you are trying to mix two subs with different frequency ranges in the same room - tricky. Usually when a sub is crossed at 80Hz, it's not localizable, although anecdotal evidence may dispute that somewhat. Have you tried an overall 60Hz cross? (perhaps your mains won't extend low enough to support it though).

I'd certainly start by integrating the single main sub and then begin to increase the level of the close sub and take measurements to check what's happening.

brucek

I found that adjusting the 2nd sub to the freq that is lacking in the room to be the best bet. If you wanted an increase <60hz and not an increase above 60hz, then the 2nd sub should start rolling off @ or around that freq.

Thanks for all your help...

[brucek]

So if I set the end Freq limit to 22khz, the sweep will cover all the way up to 44khz??

I have no idea what my sample rat elimit is on my soundcard. I saw the rate was set for 48khz. I guess thats half of my soundcard

Your cards sample rate is 48KHz, so the highest REW will scan is 24KHz.
Really, don't try and out think REW, just set it to whatever you want to measure to and REW will take care of it. Not many mics will go past 20KHz (nor does your hearing), so set an upper limit of 20KHz.

Same plot? I cant take a measurement from 0-200hz, then another measurement from 200-22khz and put them on the same graph?

You can put up to eight measures on a graph of any range you want. Usually we measure up to 200Hz when examining and equalizing subs. But you can set any range you like - 20Hz-20KHz is fine as long as you have a microphone that can do it. Just set the End frequency to scan at the limit of what you want to measure.

brucek

[jakelm]

My appologies, I do seem to over think things.

[jakelm]

OK..Here we go.. Please bare with me.

I hooked the RS meter to the Line input and things went crazy. In the soundcard calibration menu , I set the output to speaker and the input to Line in. Ran the sound card calibration. Everything worked out ok. Until, I got to the mic calibration. When I hooked the RS mic to the line inout and went to mic calibration, I installed the RS Analog calibration and checked off the C weighting box. Ran speaker pink noise to calibrate.

The line input record volume did not work , to raise the level. I had to open the soundmax window and raise a stereo mix recording instead of the line recording.

In the Record: SoundMax HD Audio window is listed:
AUX
Line IN
CD Player
Microphone
MONO Out
Stereo Mix

I had to use the Stereo mix to raise the level. Ok, no big deal. Read the meter, it was 73dbs, so when I got the levels even, I typed in 73 dbs then clicked finished.

Returned to the main screan to begin measuring. I checked volume, then clicked measure. It did it's thing with the sweep, when it posted the measurement, the graph looked like the sound card except inverted. I did everything over again from scratch and the same thing happened.

I started digging aroung my soundcard settings. I foung in a recording menu a Microphone Enhancement, which was turned on. I turned it off.

I return to the setting on REW and selected microphone for input, plugged the mic into the mic input, then re-ran the mic calibration. Adjusted my volumes and returned to the main screen.

I ran the sweep again, and it worked. From 0-22khz, a clean sweep.

I dont understand why it wouldnt work on the Line in but worked ok on the mic input.

Below or pics on the soundcard's menu and what I am talking about.

[jakelm]

New measurements with HK mic (which I found did a better job than the RS analog mic, by the way)

Logic7 Cinema 1/3 octave 10-22khz w/sub full sweep, Bass alittle hot, but its cool....

Sounds alot better after tweeking, What do you all think of the responce?

[jakelm]

Pro Logic 2 with HK mic, after adjusments, 1/3 octave

[jakelm]

And finally Stereo w/sub .5 octave

[brucek]

New measurements with HK mic (which I found did a better job than the RS analog mic, by the way)

The HK mic won't be accurate because you don't have a calibration file for it. The RS meter has a calibration file.

I had to use the Stereo mix to raise the level. Ok, no big deal. Read the meter, it was 73dbs, so when I got the levels even, I typed in 73 dbs then clicked finished.

Returned to the main screan to begin measuring. I checked volume, then clicked measure. It did it's thing with the sweep, when it posted the measurement, the graph looked like the sound card except inverted.

Stereo Mix is an internal loopback within the soundcard, it does not connect externally. You have to use Line In and configure the soundcard to get Line In working, then all should be OK for measurements. Note how the result was an inversion of the soundcard? That's becuase the output is internally looped to the input and the line-in is not being used in stereo mix.

Pro Logic 2 with HK mic

I'm afraid your results using the mic input and any soundfields aren't meaningful. The reciver must be in stereo mode with all soundfields off. REW is transmitting a mono signal. You can imagine what a soundfield does to that signal when its algorithm relies on phasing. REW is meant to be used in mono or stereo mode only.

10-22khz w/sub full sweep

You require a microphone with a calibration file that is capable of that response extension if you intend to do full range sweeps. The Galaxy CM-140 meter is suitable for full range.

brucek