# Questions on REW..



## Guest (Feb 13, 2008)

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:


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## Guest (Feb 13, 2008)

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:


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## Guest (Feb 13, 2008)

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


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## JohnM (Apr 11, 2006)

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.


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## Guest (Feb 13, 2008)

JohnM said:


> 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


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## brucek (Apr 11, 2006)

> 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


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## Guest (Feb 13, 2008)

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


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## brucek (Apr 11, 2006)

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


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## Guest (Feb 13, 2008)

brucek said:


> 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?


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## mswlogo (May 8, 2007)

brucek said:


> _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.


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## Guest (Feb 13, 2008)

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?


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## Guest (Feb 13, 2008)

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


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## brucek (Apr 11, 2006)

> 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


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## Guest (Feb 13, 2008)

brucek said:


> 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...:dontknow:




> 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...


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## brucek (Apr 11, 2006)

> 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


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## Guest (Feb 13, 2008)

My appologies, I do seem to over think things.


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## Guest (Feb 14, 2008)

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.


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## Guest (Feb 14, 2008)

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?


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## Guest (Feb 14, 2008)

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


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## Guest (Feb 14, 2008)

And finally Stereo w/sub .5 octave


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## brucek (Apr 11, 2006)

> 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


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## JohnM (Apr 11, 2006)

Also would normally need to set the Wave level to max in the playback settings, that is the source of the REW test signal.


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## Guest (Feb 14, 2008)

Brucek, 

Thanks for your answers. I am just starting out here, so there is alot I need to learn. I appreciate your help.

The last graph shows in stereo mode. I am most interested in 0-15khz, above that I know I will be off the chart.

After calibrating the RS mic, I got the same responce as the HK's, but a roll off in the higher Freq, which was to be excpected.

I worked in the Line In for a half hour, trying to get it to respond to the mic. But with no luck, I gave up.

I will post graphs of both the HK's mic and the RS mic.

I understand about running in stereo, but to get a somewhat idea of how the surrounds are performing, I ran it that way also. If you notice, there is not much difference in the stereo and the surround. Logic7 does add more bass, but between 100hz and 10khz, the responce is almost identical.

Dont give up on me my friend, I will get it.,.....raying:


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## brucek (Apr 11, 2006)

> I worked in the Line In for a half hour, trying to get it to respond to the mic


I trust for the line in, you're using a *stereo plug*, since the line-in is a stereo jack. This requires you to use an adapter that 'breaks out' the stereo left and right signal into left and right jacks..... so you can then plug the mono Radio Shack meter into one of them..??

Like these adapters:


















brucek


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## Guest (Feb 14, 2008)

brucek said:


> I trust for the line in, you're using a *stereo plug*, since the line-in is a stereo jack. This requires you to use an adapter that 'breaks out' the stereo left and right signal into left and right jacks..... so you can then plug the mono Radio Shack meter into one of them..??
> 
> Like these adapters:
> 
> ...


Absolutly, I have a stereo jack that splits into left and right RCA jacks. I then hook the left or right (cant remember, but I dont think it matters) into the Mic's output. It works perfectly for the Mic In but not for the Line In. For the Line In, I get a sugnal, but when running the sweep, its an inverted reading from the soundcards reading, at a higher dB. And like I said, when plugging the mic into the Line In, the card switches to Stereo In. And I cannot find where to disable this, so I can run direct Line In.


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## brucek (Apr 11, 2006)

> And I cannot find where to disable this, so I can run direct Line In.


I'm confused how you were able to get a soundcard cal with the line-in and not able to use it when setting up the levels?

You have to find what has placed the card in "monitor loopback" mode and disable it, becuase there is really no other way to use REW..........

brucek


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## Guest (Feb 14, 2008)

I will work on it more tonight. I will retrace all of my steps and try to find out where I am wrong.

This might be a dumb question, but, in the graphs I have posted, does there look like something is wrong with how I am measuring? 

Again, I appreciate all your help


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## brucek (Apr 11, 2006)

> in the graphs I have posted, does there look like something is wrong with how I am measuring?


It's quite hard to comment, because there are too many variables here. It's easy to get a line on a graph, but if it's not reasonably and predictably accurate, it doesn't mean too much.

You first need to have a proper soundcard cal file using line-out to line-in, that results in a perfectly flat cable loopback measurement.

Then you require a microphone or meter that has a reasonably accurate calibration file to be used to take a measurement within its response limits. You're using an HK mic that you have no knowledge of its calibration.

Then all the levels have to be set up within defined parameters and a measurement is taken...

Then you can assess the results....

brucek


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## Guest (Feb 14, 2008)

I understand.

Could the soundcard Line In calibration be used on the mic in side as well? Instead of looping the soundcard through to the Line In, if I disable all effects for the mic In, could I loop it through the mic side? Or is the mic side input too sensitive and too off, to calibrate correctly?

The problem is, my soundcard has this auto/detection , that I have to keep turning off. The soundcard is built to change its outputs. the Line In becomes surround out, the Speaker out, becomes main speak out and the mic out becomes center out. if I am not careful and pay attention to whats going on, things can and do change in the settings. The soundcard is almost too complex.

Tonight, I will go over the Line In and make sure it stays at Line In and not switches to Stereo In or some other thing.


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## brucek (Apr 11, 2006)

> is the mic side input too sensitive and too off, to calibrate correctly?


Yeah, the the mic input will offer too much gain since actual mic signals are quite low in relation to line level signal (such as the SPL meter outputs). 

This extra gain at the mic inputs front end usually results in increased noise.

In addition, mic inputs usually enjoy a very limited bandwidth that is designed to comply with a narrow voice frequency range that a cheap microphone would supply.

It's just a bad idea to try and use a mic input. If you have a line input, then there is a way to make it work.



> The soundcard is almost too complex.


We run into this all the time. People go out and buy some soundcard that could be used professionally by a recording studio, just to use with REW. We keep telling eveyone, that the best cards seem to be simple stereo el-cheapo cards that REW can create a soundcard cal for. That's what I use. It's some piece of junk I got at Futureshop in the bargain bin with a broken taped up box. Works great.

brucek


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## Guest (Feb 14, 2008)

Its not a card, its actually and intergrated Soundmax soundcard, that came with my ASUS mobo. I might have to install my el cheapo sound blaster live card.


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## Guest (Feb 16, 2008)

Calibrated Soundcard. I think I know what was the problem. I was using the wrong channel. Right instead of left when using the mic.
The help file said right, so thats what I kept using, as soon as I switched it to left, I was able to use the Line In to adjust the input volume.

I feel so dumb...:coocoo:

This is the soundcard. I can adjust my eq to raise the lower end, but I think I will leave it be.


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## Guest (Feb 16, 2008)

When starting a new project, I can just load my soundcard, right? I dont have to keep recalibrating, do I?


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## Guest (Feb 16, 2008)

Ok here is a new measurement w/ RS mic using the Line In. What do you think?


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## Guest (Feb 16, 2008)

Stereo with C weighting checked on. And RS calibration loaded. But something doesnt sound right to my ears. Why is it rolling off so quickly around 15khz?


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## Guest (Feb 16, 2008)

Another after a small tweek in the treble.


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## Guest (Feb 16, 2008)

Sub to 500hz


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## Guest (Feb 16, 2008)

Sub recalibrated. Rumble filter on Rythik amp set to Low and 14hz


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## JohnM (Apr 11, 2006)

The measurements look reasonable. The big bump around 5kHz and the rapid high frequency roll off are both characteristics of the RS meter, don't make adjustments based on an RS meter above about 1 - 2kHz.


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## Guest (Feb 16, 2008)

JohnM said:


> The measurements look reasonable. The big bump around 5kHz and the rapid high frequency roll off are both characteristics of the RS meter, don't make adjustments based on an RS meter above about 1 - 2kHz.


I thought the RS calibration tool was supposed to take care of that?

Anyways.....

I made my adjust ment mostly between 50hz-3kz.

Thanks for all the help..


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## brucek (Apr 11, 2006)

> This is the soundcard. I can adjust my eq to raise the lower end, but I think I will leave it be.


You may be a bit confused. The soundcard cal file which is created once and then loaded into the slot completely compensates for the response problems of the soundcard. That graph of the soundcard is inversly added to any measurement and so compensates. In fact, to prove the soundcard cal file is working, the help files tell you to loop a cable from line-out to line-in and do a measure. If the soundcard cal file is working properly, you should get a perfectly flat line response.



> I thought the RS calibration tool was supposed to take care of that?


The calibration tool is only to match the actual level in the room as measured by an SPL meter with the REW SPL meter level. This way, when we measure 75dB with an actual SPL meter, the REW SPL meter will show 75dB (how else would it know if we didn't have a routine to match it).

The SPL meter calibration file for the Radio Shack meter compensates for the meters response problems at the lower end. It does not take care of the fact that it is inaccurate above 1000Hz. So, you should avoid measuring above 1000Hz with the RS meter. If you want to measure full range, we recommend the Galaxy CM-140 SPL meter.

brucek


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## Guest (Feb 18, 2008)

Bruce, you have been a ton of help. 

Is there a .cal file anywhere that has measurements for the RS meter , higher than 200hz?

Also, take a look at my graph. Seems the Line In is working perfectly now. I tested soundcard cali, to line in cali. A perfect match.

Green is Line In and gold is soundcard via line in.


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## Guest (Feb 18, 2008)

After many tweeks, I think I got my bass responce as good as I can get it without eq's. Other than the hump between 50-60hz.

This is at 1/1, Should I stick with 1/3?


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## Guest (Feb 18, 2008)

Waterfall 10-500hz.

My waterfall looks like razorblades, why?


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## brucek (Apr 11, 2006)

Limit your waterfall graph to 200Hz and change to LOG mode.

brucek


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## brucek (Apr 11, 2006)

> This is at 1/1, Should I stick with 1/3?


Once you measure above about 200Hz, smoothing is usually required because of reflections that make the graph hard to read. The 1/1 and 1/3 can both be used to show different things depending on the severity of the reflections.. The overall trend is revealed with the 1/1 for sure and more detail is exposed with the 1/3.

brucek


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## Guest (Feb 18, 2008)

Ok, Bruce, will do.

I prefere the 1/3 because I find the 1/1 too smooth. There are dips that just dont show up in the 1/1.

Will close the graph down to 200hz.

Being I'm an ameteur at graphs, I cant somewhat tell what I'm looking at. But looking at my graph, what suggestions would you give concerning peeks and dips?


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## Guest (Feb 19, 2008)

10hz - 200hz water fall.


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## brucek (Apr 11, 2006)

Yeah, looks pretty good. Usually I find if I switch the graph from LIN to LOG (click the Freq Axis ICON button), it will look more like the frequency response graphs that are in LOG form. Then you can move the waterfall slider from 1 to 30 and see how each slice falls off in time.

brucek


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## Guest (Feb 19, 2008)

10hz-200hz Changing Freq Axis...

Is this what you ment?


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## jagman (Jul 8, 2006)

Your plot looks pretty good considering no EQ. If you bump the sub volume up a little relative to the mains, you could dial in a pretty nice house curve by only having to cut a couple peaks (~24 Hz and 50-60 Hz).


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## Guest (Feb 19, 2008)

jagman said:


> Your plot looks pretty good considering no EQ. If you bump the sub volume up a little relative to the mains, you could dial in a pretty nice house curve by only having to cut a couple peaks (~24 Hz and 50-60 Hz).


What I did, actually. I do not have a graph, but I turned my second sub on. Crossed it over @ 40hz. Turned it until the blend was pleasent to the ears. The second sub is a Dayton 12" w/Rythmik amp, tuned to ~23hz. It is located in the opposite corner of the room. ~ 22' from the opposite 1st sub.

I will take another measurement with the 2nd sub, but by just reading my RS meter, 22-37hz have increased 2dB's. I did a quick eye measurement with my RS meter, just to some-what dial in the 2nd sub.

I didnt want to keep increasing the 1st sub, due to phase and null problems, so I kept the 1st sub "as is" with the mains and filled in the gaps with the 2nd sub.


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