# First REW Effort, Think I Did Something Wrong



## tythebigd (Jul 22, 2009)

Alright, just wanted to run some tests with REW before my sub gets in later this week. So, I calibrate the sound card which already gave me trouble. I had a hard time adjusting the output and input so that I didnt get clipping issues. Basically had to have the input almost off. (I am using a realtek onboard on my PC). This is what I got for my souncard cal:









I took a measurement of the loopback to make sure it worked, and seemed fine to me?:









Now, hooked up to my receiver and ran some tests. Here is a full range run:








And here is a low:










Now, here is whats bothering me. First off, it dies up top? Doesn't sound that way. Secondly, down low. Supposedly my L and R speakers are running "flat" to under 20hz? This is impossible. They have ok output to about 40, but basically nothing under 30-35. What is going on with these measurements? Could it be that I am using long cable runs from my PC to my living room? (I dont have a laptop).

Edit: Might want to add I am using a Galaxy CM-140.

Any advice would be appreciated.

-Tyson


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## Wayne A. Pflughaupt (Apr 13, 2006)

Welcome to the Forum, T! Congrats, looks like you got REW up and running just fine. :T

Unfortunately you didn’t give us enough information to answer your questions.




> Now, here is whats bothering me. First off, it dies up top? Doesn't sound that way.


Measure one speaker at a time, point the mic at the speaker. Does your receiver have any kind of auto EQ / calibration function that you’ve utilized?




> Secondly, down low. Supposedly my L and R speakers are running "flat" to under 20hz? This is impossible. They have ok output to about 40, but basically nothing under 30-35.


How exactly did you previously determine that? What kind of speakers are these? Once again, any auto EQ that could have enhanced extension?

Regards,
Wayne


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## tythebigd (Jul 22, 2009)

Ill try measuring speakers one at a time when I get home from work.

I have a Yamaha RX-V765, so it does have eq. I tried with it on and off and it made no significant difference.

My mains are destination audio f300t's. They are rated to -3dB at 45 hz, and definitely roll off hard after that. At 30 hz, they have very little output. It is very easy to tell by ear.

Could the long cable runs be affecting this? Should I recalibrate the sound card using the long cable runs as the loopback?


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## glaufman (Nov 25, 2007)

It's conceivable the long cable runs affect the high end, but I wouldn't expect them to affect the low end... you could try running a scan (with the already produced soundcard cal) of just the cables and see exactly what they're doing to you.


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## Wayne A. Pflughaupt (Apr 13, 2006)

tythebigd said:


> My mains are destination audio f300t's. They are rated to -3dB at 45 hz, and definitely roll off hard after that. At 30 hz, they have very little output. It is very easy to tell by ear.


Keep in mind that factory specs are not absolute. For instance, if you use large speakers like that in a small room, low freq extension will improve due to cabin gain. In your case it looks like extension is being extended from 45 Hz down to ~38. That’s not a huge difference. 

Also, manufacturers have been known to be conservative with their specs, as it can get a more favorable reaction from reviewers and owners. After all, who’s going to be disappointed when they find that a speaker goes lower than was expected?

Also, keep in mind that the graph scaling is coming into play. The “low” graph, which stretches the horizontal scale, is being visually “nicer” to low end response than the compressed full range graph. But with either graph you can see that response drops at least 10 dB between 38 and 20 Hz. That’s a significant enough drop that render output at 20 Hz insignificant.

As for as the upper end, I can't say I've ever seen anyone post a full-range graph generated with the Galaxy meter, so I'm not familiar with what to expect from them.

Regards,
Wayne


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## tythebigd (Jul 22, 2009)

Thats a good idea. Ill try that tonight before I take measurements of the L R mains by themselves.

One other thing, is it normal to have to turn the output volume down to half or less and the input volume to almost 0 in order to keep from clipping?


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## tythebigd (Jul 22, 2009)

One other thing, at a few spots there is what appears to be a null such as at 200 hz in the low graph I posted. But, If I play a sine wave sweep from 180-210 slowly, there definitely doesnt sound to be any huge null like the graph shows. Is there any explination for this?


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## Wayne A. Pflughaupt (Apr 13, 2006)

If you're talking about the full range graph, 210 Hz is still in the depressed area. Try a wider sweep, say 150-400 Hz.

If you're talking about the bass-only graph, the 200 Hz null is too narrow to hear.

Regards,
Wayne


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## tythebigd (Jul 22, 2009)

Ya, I was refering to the bass only graph. For that graph I ran from 0 - 500hz.

So, since the null is too small to hear, does it matter?


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## Wayne A. Pflughaupt (Apr 13, 2006)

I don't worry about what I can't hear... 

Regards,
Wayne


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## glaufman (Nov 25, 2007)

Which is why the monster behind you always wins!


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## tythebigd (Jul 22, 2009)

Ok, so I ran a loopback measurement using all my cabling. Perfectly flat. So thats not affecting anything.

I reran the measurements for the left and right seperate and again with them both together. This time I left off the cal file for the cm-140, makes the top end look alot more realistic.

Left with 1/12 smoothing:








Right with 1/12 smoothing:








And Both:


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## glaufman (Nov 25, 2007)

Looks to me like you're using less smoothing now than before, and of course a slightly different scale, so it's difficult to compare directly... performing the additional smoothing mentally, it looks like you still have a dropoff starting at 4kHz... more realistic doesn't necessarily mean more accurate... Are those iwth the Galaxy in the same orientation? (hor vs vert)? Are you using our generic cal file for the Galaxy? It was taken in the horizontal position.


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## tythebigd (Jul 22, 2009)

The mic was positioned horizontally and and it was pointed at the speakers when I did the L or R by themselves. I didnt use the cal file for these graphs. When using the cal file I get a significant drop after 4kHz and I cant believe that its true. It shows ~11dB drop from 4kHz - 10kHz with the cal file and that for sure would be audible, but I don't hear a significant drop (or maybe I am naive?)


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## glaufman (Nov 25, 2007)

It's hard for me to say exactly without having all the graphs in front of me on the same scale and the same smoothing. BTW you can add/remove the cal file after the fact.
It's possible you need a custom cal file for that mic, that the generic cal file doesn't fit your particular one very well in that range. Was it the generic one you used?


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## Wayne A. Pflughaupt (Apr 13, 2006)

tythebigd said:


> I didnt use the cal file for these graphs. When using the cal file I get a significant drop after 4kHz and I cant believe that its true. It shows ~11dB drop from 4kHz - 10kHz with the cal file and that for sure would be audible, but I don't hear a significant drop (or maybe I am naive?)


I would agree that something’s amiss. The Galaxy calibration file shows that the meter is pretty well flat out to 8kHz. So with or without the calibration file you shouldn’t be seeing a drop starting as low as 4 kHz, especially one as serious as this.

Really, the best way to ensure accurate full-range measurements is with a custom-calibrated ECM8000 or EMM-6 mic...

Regards,
Wayne


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## tythebigd (Jul 22, 2009)

Thanks for all you guys help. I'm not too worried about the upper range, it sounds good to my ears  When I get my sub in I will repost my bass measurements.


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## tythebigd (Jul 22, 2009)

Got my Empire in today and so far really liking it  Now that I got some time I am moving it around and taking measurements. There are two places that I have found so far that will be ok I think, but the front right placement might be questionable with the wife. I will find out tomorrow 

Here is the Front Right which I think looks better and easier to EQ:








Here is a better spot as far as layout goes, we will call "corner":








And a overlay:








By the way, these are all with the mains running.

Do you think I can get away with the corner? Or should I try to convince my wife that frint right is ok 

Gonne keep messing with positions before I start EQ'ing.


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## tythebigd (Jul 22, 2009)

Did some EQ'ing. Not sure what to do with the 125hz null.


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## Nuance (Nov 2, 2008)

What is your crossover point? If your crossover is below 125Hz the null could be a phase issue or caused by the speaker interaction with the room. Room treatments or a repositioning of the speakers could fix the issue if its room related.


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## tythebigd (Jul 22, 2009)

Ya, I moved my speakers around a bit and fixed the 125hz null. Now I am going to run YPAO and see what that does for me. 


Cant do any listening tests till tomorrow, bummmmmed.


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## Nuance (Nov 2, 2008)

Cool. That looks pretty good. Put some listening time in tomorrow, and if it sounds good you're done.


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## tythebigd (Jul 22, 2009)

Hah, well my wife just told me I cant have the sub in the front right. So, looks like I have to start all over with the other position. Moving this 120lb beast around is fun...........


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## glaufman (Nov 25, 2007)

Front right is a nice looking response for no EQ... leave the sub where it is... move the wife...


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## tythebigd (Jul 22, 2009)

Ya, to get it relatively flat only really required two filters. 

O well, where the sub is at now has its advantages. Its right next to the couch so you can really feel the bass. There is one trouble spot at 30hz that can't be fixed. It is down about 10 db. 

I am gonna try to convince her eventually that we need another sub though. Hopefully it works


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## BowerR64 (Nov 4, 2009)

How do you smooth out the graphs? mine seem really noisy compaired to these?

Could it be his microphone is better? or the responce time maybe?


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## glaufman (Nov 25, 2007)

You can go into "Trace Adjustments"







Many of us like to look at bass graphs <200Hz with no smoothing, and full range graphs with 1/3 octave.


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