# does this graph look right?



## xx-moto-xx (Sep 11, 2006)

I've read and followed the entire setup in the help section of REW, I don't think there were any setup or calibration errors, and these are the graphs I get. It seems a little too scattered to make any sense of. The first is the measured responses and the second is the filter adjustment graph.


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## xx-moto-xx (Sep 11, 2006)

I forgot to ask, should "compensate for c weighting" be checked or unchecked when taking measurements?"
Also, I notice the guide to posting graphs says to cut off at 200Hz. Why is this? Is this program only good for bass tuning?
Thanks for any help and answers.


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## Guest (Sep 14, 2006)

I don't know what the recommended trace smoothing is...but if you use 1/3 or 1/1 you should see a better picture of the average. You should also set the limits of the graph to the following: Top=105.0, Bottom=45.0, Left=15.0, Right=200.0. This will give you a better picture of your low frequencies only. You then want to set the graph size to 800 pixels wide.

It also doesn't look like you have your 80Hz crossover in your reciever on, but you have the target set to Bass limited with a 120 or so cutoff? Which speakers are playing when you took the measurements? Do you have a sub? Towers? What kind of mic are you using? I'm not sure why you have the the target line sloping down like that at 80Hz as it seems you have a full range signal. I'm guessing you are using tower's that are set to large...if so set the target to full range and set your graph up like I explained in paragraph 1. There is also a thread that explains this.


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## brucek (Apr 11, 2006)

Tell us what you're trying to accomplish first.

What is your goal? Subwoofer equalization? Room equalization with traps? Main speaker testing? etc


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## xx-moto-xx (Sep 11, 2006)

Thanks for your responses. I'm new at this, so I need guidance.
First: What I'm trying to accomplish is to test the full range of sound in my system as it is now, and make whatever improvments that I can make (ie: receiver eq settings, Sub crossover setting/volume, sub location, etc).
Second: my equipment-
JVC RX-8000VBK (100W/channel) Receiver
Panasonic DMR-ES20 DVD Recorder
Polk Audio RM5400 Sat speaker system- 
I have moved the PSW50 that came with the system to the rear channel and added a PSW350 to the front.
I have both Subs wired into the receiver speaker terminals and adjust the crossover at the Sub (Polk Audios recommendation). I have my speakers set to LARGE except the center, which is set to small.
I am using a RS33-4050 to take measurements - I just bought yesterday for this testing.
I'm not sure why my target line is dropping so steep at 80Hz. I cant remember what step in the process set this line, but I'll check it out and redo the set up if I need to. Any ideas why my measurements are so erratic? is this normal?


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## brucek (Apr 11, 2006)

> What I'm trying to accomplish is to test the full range of sound in my system as it is now


If you're using a Radio Shack Meter for this task, it isn't accurate much above 5KHz, so I wouldn't measure higher than that.

Hopefully, you're using the correct calibration file in REW for the meter you are using.

Yes, c-weighting must be turned on and a calibration file used.

Your vertical scale should be from 45dB to 105dB. Always return to this scale after *every* measurement.



> Also, I notice the guide to posting graphs says to cut off at 200Hz. Why is this? Is this program only good for bass tuning?


No, but it's the area of interest for creating filters in a parametric equalizer to compensate for low frequency effects (where most of the problems will occur). No use measuring above that if you can't do anything about it. Were you planning on building room treaments or traps for the higher frequencies?



> I have both Subs wired into the receiver speaker terminals and adjust the crossover at the Sub (Polk Audios recommendation). I have my speakers set to LARGE except the center, which is set to small.


Doesn't really make sense. Your receiver is designed specifically to carry out bass management. You can't do this unless you connect your subwoofer to the subwoofer output on the receiver and select an appropriate crossover in the receiver (while deselecting the subs crossover). 

With your center selected as small, where are the center low frequencies being directed?

With your mains on large, both the subwoofer and mains are producing the same low frequencies. This creates cancellations in addition to the inability to re-locate the low frequency source produced by the mains to obtain better response in the room as you would a subwoofer. 

brucek


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## xx-moto-xx (Sep 11, 2006)

Thinking back, I downloaded the cal file, but I don't remember loading it. I may have or may not, it took a while to get set up. I'll start over from the begining this weekend and try again up to 5Hz - Thanks for that piece of info by the way.


> Were you planning on building room treaments or traps for the higher frequencies?


I plan to give this a try, I have the tools, and it would be a fun project, but I need to learn more about it first.
Let me explain a little better about the sub arrangement. I run speaker wire from the receiver to the Subs high level inputs, and then wire from the Subs speaker outputs to the satellites. I set the receiver setting to LARGE so that it sends the signal as if this was a full range tower speaker and the adjustable crossover built into the sub cuts the frequency to the satellites. The manual that came with the speaker system recommended this arrangement over using the receivers sub output. Once I get a good measurement with this, I'm certanly open to trying it using the receivers sub output instead as a comparison.


> With your center selected as small, where are the center low frequencies being directed?


With the main speakers set to LARGE and the center set to SMALL and the receivers crossover set to 100Hz, center channel signals below 100Hz get sent to the mains. I know 80Hz is a more common crossover point, but the speakers in the satellite system are quite small and it sounds better at 100. 
In the future (christmas?) I'm planning to move the front satellites to the rear (they are much better than the rear speakers that came with the system), and purchase either a pair of Polk Monitor 60, or RTi8 towers for the mains along with a matching center.
Thanks for your help, I really appriciate it.


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## brucek (Apr 11, 2006)

> I run speaker wire from the receiver to the Subs high level inputs, and then wire from the Subs speaker outputs to the satellites


Yeah, this connection method is a bit dated and has been replaced since all receivers now have fairly sophisticated bass management circuitry.

I would highly recommend setting all your speakers to small @100Hz and connect the large subwoofer to the subwoofer line out. All redirected and LFE channel bass will be sent to the subwoofer, that you can then place for optimum room response (corner being your first choice). I would not use the lesser sub. Combining a capable and lesser sub together dumbs down the capable ones abilities.

Polk will recommend the high level situation since it is a sure bet that in all configurations from old to new it will work. Not work the best - just work. If you have a receiver with bass management, it will be the best configuration to use.

brucek


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## xx-moto-xx (Sep 11, 2006)

I re-ran the tests and have new graphs, but the MANAGE ATTACHMENTS button is gone, and I can not select the "attachments" icon (or any other icon) in the "reply to thread" screen.
???


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## brucek (Apr 11, 2006)

> but the MANAGE ATTACHMENTS button is gone, and I can not select the "attachments" icon


Don't understand why? You do have to use the POST REPLY button and not the Quick function at the bottom of the page for those features though........


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## xx-moto-xx (Sep 11, 2006)

I used "post reply" and then "preview post", still nothing is selectable (smilies, text formating etc.). The graphs turned out MUCH better so, I'll try again later. Sometimes "later" magically fixes everything.


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## xx-moto-xx (Sep 11, 2006)

Here are the new graphs. These are measured with the sub still wired to the high level inputs, so I'll have re-wire and compare with the receivers bass management system. Both have "trace smoothing" applied at 1/3 octave. The first is 10-5KHz, left right and "Sub only". Any ideas on the reason for the drop at 3KHz?
The second is 10-300Hz (to show full the drop on the Sub channel). How does it look?


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## brucek (Apr 11, 2006)

Can you be more specific about what you're showing in the second graph?

Is the purple the sub only with a crossover at 100Hz? 

Are the red and green a left and right combined with the sub?


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## xx-moto-xx (Sep 11, 2006)

The red and green lines are the right and left channels with the sub wired at the high level inputs and the sub outputs wired to the satellites. The purple line is a repeat of the right channel test with the speaker wire disconnected at the satellite (sub only).


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## brucek (Apr 11, 2006)

Since you aren't able to equalize the sub with the wiring configuration you've chosen, you might try to reduce the peak at ~80Hz by lowering the subs LPF a bit. You might also try the phase switch to help reduce that peak.

Other than that it looks fine. The sub has a spec of -3dB @38Hz, so you're more than beating that, and the transition to the mains looks pretty good except around 80Hz...

brucek


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## xx-moto-xx (Sep 11, 2006)

Thanks for your help Bruce. I'm planning to rewire and try using the sub output on the receiver. After I do that, can the adjustable LPF on the sub still be used for fine tuning? Or where should I set it, since I'll be using the crossover at the receiver?


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## brucek (Apr 11, 2006)

> After I do that, can the adjustable LPF on the sub still be used for fine tuning? Or where should I set it, since I'll be using the crossover at the receiver?


No, you don't want the subs LPF in use at all when you use the receivers bass management. I believe your sub has an input called LFE, which totally bypasses all filtering. Use that. 

Some subs don't have the ability to bypass the LPF, so in that case the LPF control is dialed to maximum to reduce its effect.

brucek


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