# REW Suggestions



## spike99 (Nov 29, 2011)

Hi,

New to this forum.

OK, so I would like to check my In-Room frequency response in my HT for my sub and possibly make manual modifications.

I have been reading some posts but wanted to mention what I have and wanted to get suggestions.

I have the following:
SPL Meter: Galaxy CM140
Laptop with XP - Soundcard: internal soundcard
Desktop with Win 7 - Soundcard: HT | OMEGA Claro Halo XT PCI Interface Sound Card

With the laptop, I probably will need to buy an external USB soundcard
With Desktop, it has a very good soundcard already.

Although my desktop has a good souncard it's a bit heavy and a pain to move around but since taking measurements will only require only a few moves, maybe I should use my desktop ?

On the flip side, probably its easier to use my laptop since I can take measurements easily and don't need to drag my desktop. I have seen some suggestions for external usb sound cards but those suggestions were old links so I don't know if there is a more up to date suggestion.

For microphone... should I use my SPL (CM-140) ? or do I need to buy a separate mic ?

Thanks in advance.


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## EarlK (Jan 1, 2010)

>< A few observations ;

(i) REW runs great on XP .

(ii) Lap-Tops ( by their portable nature ) do encourage users to measure .

(iii) That Galaxy SPL meter is one of the recommended measurement mics ( since it has a line-level output ) .

(iv) Typically ( now-a-days & by the later releases of XP just before Vista ) the built-in soundcards within laptops are/were up to the task of running REW .

<> So, I would use the lap-top. Get the necessary adapters & cables to access your sound-cards ins & outs and then give REW a whirl . ( You'll need to research all this stuff in the self-help guide at the top of the forum ) .

<> You'll know soon enough if your setup is golden ( once you go & make a soundcard calibration ) .

<> In my case I can't directly plug a SPL meter into my Dell 2510 laptop because the stereo microphone jack on it outputs a couple of volts ( for some reason ) which stops my Radio Shack meter from performing properly . The "fix" in my case was to use a simple Behringer UCA202 ( USB SoundCard ) since it doesn't output this strange ( un-needed ) voltage .

:sn:


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## spike99 (Nov 29, 2011)

I do prefer laptop due to portability.

OK, I will first check the internal sound card of my dell laptop. 

By the way, looks like I have Vista instead of XP on my laptop.

Also, regarding my SPL (CM140), specs indicate that it goes down to about 30Hz. If this only goes down to 30Hz, how does it measure below this ?


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## spike99 (Nov 29, 2011)

OK,

So I downloaded REW and tried to calibrate sound card with both my desktop & laptop.

The measurements look very similar and they look pretty bad on both my desktop and laptop. 

Experimenting with my desktop, I wasn't sure if it made a difference but I set sample rate on my sound card to be the same as 44.1k and retested with same results... then I plug laptop to my AVR with similar results.

The sound card on my PC is pretty good so I don't know if I bought an external USB sound card for my laptop would make a difference ?

One thing to note is that when I connect my laptop to my AVR, there's a lot of noise that I hear from AV receiver and when I put music on, I don't hear noise anymore.

Any suggestions ?


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## spike99 (Nov 29, 2011)

Apologies, I did not read the instructions properly. This looks a bit better.

Edit: Shouldn't the line be closer to zero ? Should I consider getting an external USB sound card ?


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## EarlK (Jan 1, 2010)

> REWs soundcard correction ( calibration file ) will effectively "zero-out" the response ( compared to what's shown above ) .

> While the trace is a mite noisy for my liking / (IMO) it's still not worth dumping the card for a new one .

> Try running your laptop of the battery ( & turn off WiFi ) & then run another loopback calibration for the soundcard ( it'll usually be a bit cleaner when taken with a CPU running on battery power ). 

:sn:


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## spike99 (Nov 29, 2011)

EarlK said:


> > REWs soundcard correction ( calibration file ) will effectively "zero-out" the response ( compared to what's shown above ) .
> 
> > While the trace is a mite noisy for my liking / (IMO) it's still not worth dumping the card for a new one .
> 
> ...


Unfortunately battery for my laptop does not work and I have to plug Adaptor to turn on laptop... I can turn off WiFi but last night I ran into some trouble and since it was late last night was unable to post additional info.

From memory, below are the issues I encountered. Note: I have been reading the help PDF file for REW.
1. After I calibrated soundcard, I followed below steps....
To check that the calibration has been successful:

Leave the loopback connection from line output to line input in place
Uncheck the C Weighted SPL Meter box in the Mic/Meter Preferences
Press the Measure button
Press Start Measuring

On the "make a measurment window" only the first bar went up to about 90db and then it just sat there... with "Ready to measure" at the bottom. I was expecting a chart displayed in page 23 of PDF help file.

Although I was expecting a chart, I continued with the steps of help file.

Next I did the "Check Levels". Initially I connected my PC output to AVR. I believe in this step I had an issue where I noticed bass from my speakers... and I only wanted to check frequency my sub at this time... I wasn't sure how to disable front speakers in AVR, so I connected PC to sub directly.

Calibrating SPL was fine... It was set to 75db.

Next came the "Making a Measurement". The result in the chart did not seem correct. I don't remember the values but it just didn't look right.

I tried to see some of the previous steps I had done before and then decided to start from the beginning. This is where everything was wrong. 

I started noticing noise coming from sub when RCA plugs were connected to my PC. Something was not right there.

Next, I tried to re-cablibrate soundcard.... but it seems the output & line in on PC was not working properly... At this point it was a late so I gave up.

Right now, it seems like a sound card issue ? Everytime I unplug and re-enter 3.5 cable to laptop, I have to select what type of connection... for the mic, I have to select either mic or line in.

You mentioned you had "Behringer UCA202", this is very inexpensive and maybe I should buy this and retry ?


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## EarlK (Jan 1, 2010)

> This is a fair representation of the setup you should be using for measurements ( you don't need the left out to left in loopback cable at this time ) .

> When using an SLM ( such as the Galaxy 140 ) as your test mic , set it to "C" weighting & check the "C weighting" compensation box within REWs " preferences window, under the "Mic/Meter" tab . 

> Regarding what you think are SoundCard issues . Make sure you are using the proper adapters & cables .

ie ; Use stereo 3.5mm plugs that then go to mono "whatever" type of connectors ( typically, female RCA ) . 
-  *ReRead the user manual of the Galaxy 140 * to confirm what type of connector it uses for output ( it's a mono 3.5mm output, so don't plug a stereo 3.5mm connector into it & expect it to work ).










:sn:


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## spike99 (Nov 29, 2011)

EarlK said:


> > This is a fair representation of the setup you should be using for measurements ( you don't need the left out to left in loopback cable at this time ) .
> 
> > When using an SLM ( such as the Galaxy 140 ) as your test mic , set it to "C" weighting & check the "C weighting" compensation box within REWs " preferences window, under the "Mic/Meter" tab .
> 
> ...


Thanks for diagram.

One of the things I noticed was that it indicates that when you connect to AVR, it should be in "stereo mode"... I'll check this.

I had mentioned previously that I had noticed bass output coming from front speakers... how do I prevent bass output from front speakers ? I thought about disconnecting banana plugs from speakers... that's why I connected to sub directly.

> When using an SLM ( such as the Galaxy 140 ) as your test mic , set it to "C" weighting & check the "C weighting" compensation box within REWs " preferences window, under the "Mic/Meter" tab . 

This was done.

> Regarding what you think are SoundCard issues . Make sure you are using the proper adapters & cables 
I checked CM-140 manual it states the following:
*Output signal by standard 3.5mm coaxial socket signal on pin.*
I do have a 3.5mm cable that I plugged my CM-140 directly to mic input to PC with no adapters...

Edit: I just called Galaxy audio, and they confirmed that their CM-140 output is a 3.5mm stereo ouput so the 3.5mm cable I have should be good.

But I when I plugged PC to sub... here is where I did something wrong. When calibrating souncard I connected line in to one line out (PC has 2 line outs) and when I connected PC to sub I plugged both line outs to sub... I need to get adapter you provided one 3.5mm on one end and 2 RCA outs on other end.

I'll get this adapter and retry...


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## spike99 (Nov 29, 2011)

OK... So today I was able to recablibrate sound card with no issues.

Next step was to check cal was successful but it doesn't look right.

Pease advise.


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## spike99 (Nov 29, 2011)

Forgot to attach file:
Above line is: db
middle line is: soundcard cal
bottom line is: Phase


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## Sweetmeat (Nov 19, 2011)

spike99 said:


> Forgot to attach file:
> Above line is: db
> middle line is: soundcard cal
> bottom line is: Phase


Wow, at least you've made it that far. I've had very similar problems as you, and not sure what to do next. Maybe you could provide some suggestions?

To this point, I've calibrated the sound card and then checked the levels.

Then I hooked up the cables as depicted in the help section (the hookup without using a sub EQ), with the loopback, then measured. This is where I started having problems.

First, I hear a ton of static coming out of my front speakers. When I hook up directly to the sub, I get measurements that I would expect, but I was told not to do that. It was recommended to hookup to the AVR so the fronts and sub could be measured to ensure they integrate well together. 

The second issue I had was I could get up to 80db when connected to the AVR, no matter how high I set the volume to. Really, I didn't hear any test tones coming out like I did when I had it hooked up to the sub.

The third problem I had was that I kept getting a message after the measurement that said that the SPL was too low and I needed to either increase the AVRs volume or the level. I tried increasjng the AVR's volume to -10 (which is really loud), but that work. Then I tried incrementally increasing the level and that eliminated the message, but my measurements still don't show 80db - AND I'm not sure if by changing the level messes with the calibrations that I did with a different level value - so I'm not sure if I'm getting any valid results.

Have any ideas?


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## spike99 (Nov 29, 2011)

Actually, I believe the image I posted previously looked OK....

But when I measured then this looks wrong or at least not ideal ?


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## spike99 (Nov 29, 2011)

Sweetmeat said:


> Wow, at least you've made it that far. I've had very similar problems as you, and not sure what to do next. Maybe you could provide some suggestions?
> 
> To this point, I've calibrated the sound card and then checked the levels.
> 
> ...


Actually, I also have static noise when I connect to AVR. Before I connected to sub directly but now I connect to AVR. In order to send bass to sub only I changed cross over for speakers to 200Hz so that noise only goes to sub.

Yes, I also got SPL was too low but I increased vol level on my AVR and that resolved it.


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## spike99 (Nov 29, 2011)

spike99 said:


> Actually, I believe the image I posted previously looked OK....
> 
> But when I measured then this looks wrong or at least not ideal ?


So I continued to experiment today. I continue to get noise when connecting from PC to AVR and it is very annoying... Should I be getting an external soundcard ? Also, does it make sense to get a MIC with pre amp ?

I have several bass traps but moving them around did not make any change.

I do have a 10" sub in my bedroom and although they are different from my 12" sub in my Living Rm I thought it would be a good idea to experiment to see if it made a difference and get a flatter response. The reason I'm experiment is that I probably need to return my 12" ported sub due to size and was thinking of getting 2 10" subs.

So after I connected both subs and placed the 12" sub by front speakers and then the 10" sub diagonally I ran Audyssey XT32. Then I re-did steps for REW except to calibrate sound card.... I got the same response from above... no flattening response...

I'm pretty sure I set the same db levels for both subs when running Audyssey so I'm a bit confussed about results.

Any ideas ?


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## fotto (Jan 17, 2010)

Regarding the static, I found that if I had my PC power supply plugged in that I got static. Running on battery/unplugged fixed it. Must have been a ground loop or something.

Not sure if that's your issue, but might check it out.


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## Sweetmeat (Nov 19, 2011)

fotto said:


> Regarding the static, I found that if I had my PC power supply plugged in that I got static. Running on battery/unplugged fixed it. Must have been a ground loop or something.
> 
> Not sure if that's your issue, but might check it out.


Thanks for your suggestion. I'll try that out.


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## spike99 (Nov 29, 2011)

Sweetmeat said:


> Thanks for your suggestion. I'll try that out.


Let me know if that resolves it for you.. Unfortunately, my battery does not work and needs replacement, hence I can only plug to outlet.


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## spike99 (Nov 29, 2011)

Hello,

I have rerun my Auddyssey set up. Please see my attachment. To fix this... Since I'm unable to to move my sub from current location... is the solution to get a second sub ?

Thanks in advance.


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## JohnM (Apr 11, 2006)

Additional subwoofers in other locations can help smooth the overall low frequency response, but a second sub in the same location (e.g. stacked on top of the existing sub) would not have the same effect. If you have another location for a second sub you could try moving your current sub there first. Also worth trying different seating positions if you have some flexibility there.


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## spike99 (Nov 29, 2011)

JohnM said:


> Additional subwoofers in other locations can help smooth the overall low frequency response, but a second sub in the same location (e.g. stacked on top of the existing sub) would not have the same effect. If you have another location for a second sub you could try moving your current sub there first. Also worth trying different seating positions if you have some flexibility there.


Yes, I will be placing second sub in different location. My current sub which I plan to change to a smaller one is huge and I'm not able to move to a different location. I have rerun REW and tested 3 different positions and I have attached results. There are slight differences but overall not any better ?


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## JohnM (Apr 11, 2006)

The third position has the shallowest dips, that's the one I would go for.


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## spike99 (Nov 29, 2011)

JohnM said:


> The third position has the shallowest dips, that's the one I would go for.


It's odd because when I tested yesterday it wasn't show the null at 25Hz. Yes, position 3 has lowest dips... So to resolve these dips... Is the solution to get an extra sub ? Or am I making too much of a big deal ?


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