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Discussion Starter #1
Hi folks,


Can someone guide me on how to plot a graph so I can see how much LFE my sub is able to produce. I would like to use whatever I have at home but I don't know where to start. I have the Radio Shack analog SPL meter and it's got an RCA port. I also have a computer. What software do I need? Are there free downloadable software that can do the the graph? I couldn't recall the term, I think it's called waterfall. Do I hook the spl meter to my computer's sound card?


Any help would be greatly appreciated.


Thanks,


Neil
 

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If you're looking to do waterfalls like the one in DrPainMD's thread movies with bass, he has a link in the thread to show you how to do it. Kweezer has pics to do settings.
 

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Discussion Starter #4

Quote:
Originally Posted by JamesK8 /forum/post/13006824


If you're looking to do waterfalls like the one in DrPainMD's thread movies with bass, he has a link in the thread to show you how to do it. Kweezer has pics to do settings.

Great! I will search for this threads so I can make the waterfall. I am also now interested in the other information I've posted. I really need some help. I want to know if I am doing it right. I don't know if I am really doing it right. I continued last night since I didn't see any response on the Audio Test thread. I found out that I need to put the data to an excel spreadsheet so I did. However, I remember not seeing any 21Hz, 22Hz or 28Hz on the dvd. That means, I don't know what to put in the column C.


And also, I want to know if my sub is doing fine based from the values I've gathered. I'm also getting very conflicting information as to spl meter setting. I found an article and it mentions that I should set it to FAST response while playing a tone sweep like .5db 200Hz-1hz. Then I'm quite confused as to how to plot it because when playing that test sweep tone, I don't know what tone is being played. My hand writing and eyes are not fast enough to switch back and forth on the paper and the spl meter. Something is really wrong with the way I am doing. So someone please, I need your help since I really don't understand the values. And also honestly, I'm not bragging about the result because I don't know if sub is doing fine or not.


Just few minutes ago, I did some test again. I played the -.5db 200hz-10z again but I turned my Yamaha's master volume at -24b. I found this test on the Extras menu. I took a picture of my radio shack when it hit 120db. The needle happened maybe somewhere 20hz-30hz. That is just my guess only since after few seconds, the test was done.


So yeah, if anyone can help, I would really appreciate it.

 

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Discussion Starter #6

Quote:
Originally Posted by exojam /forum/post/13008475


You can use REW which is a free download. All the information you will need concerning it is located below. I found it to be a great program and the folks over there are very helpful if you have questions (just read the instructions first). Hope this helps.

http://www.hometheatershack.com/forums/rew-forum/

Thank you so much!!!
With the information I mentioned above, is there something wrong with what I did?
 

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I have never used a test cd to obtain readings. I have always used REW for measurements. It has a file you can download to correct the RS meters for correction values. Take a little time to read through the REW steps and than you can compare what you had previously obtained and see what you get.


Looking at some of that thread you mention, I see this are “manual plots” of your readings. REW does all the processing for you. Much, much easier once you figure out what you are doing. Below are two old graphs I had from REW jsut to show you some of the output.



 

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Discussion Starter #8
exojam,


Finally, I was able to use REW. I followed every step such as the SPL meter calibration and the plus-minus number that we should match. Then I clicked check levels and it says Level is OK. -17.2 db. It changes sometimes.


Anyways, here is the reading. However, I don't know how to decipher the graph. I would like to know what I just did. I would like to know if the graph is bad. Can someone please check?


Oh, and also, I couldn't find the LIN or LOG that was mentioned by Sonnie of Shack. Where do I find it?




Any help would be greatly appreciated.


Thanks,


Neil
 

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First question I would have in seeing that output is what value did you get when you did the "Calibrate SPL" step?


Also, just did a quick search for "lin log" at HTS and there was this entry. See if you can find the button he is referring to. Let me know if that helps.


You need to change your graphs from linear (LIN) to logarithmic (LOG). It's an ICON at the top of REW called Freq Axis.
 

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Discussion Starter #10

Quote:
Originally Posted by exojam /forum/post/13010908


First question I would have in seeing that output is what value did you get when you did the "Calibrate SPL" step?


Also, just did a quick search for "lin log" at HTS and there was this entry. See if you can find the button he is referring to. Let me know if that helps.


You need to change your graphs from linear (LIN) to logarithmic (LOG). It's an ICON at the top of REW called Freq Axis.

I adjusted it to 80 because my SPL meter's needle was at 0db and dial knob at 80db.
 

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I use a digital RS meter so I am not familiar on how yours reads. Can you set your receiver to -20db and than adjust your sub amp to have the meter read 75db while running a test tone. Do the check SPL and make sure it reads right around 75db. Set the target to 75db, than run another sweep and let me see what you have for a graph
 

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Discussion Starter #12
I redid everything. It's set at 75db now. Here is the latest graph. Yamaha receiver also says -24db. What do you think about the output now?

 

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Whoa. You would be a good candidate for room treatments and some eq.
 

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Discussion Starter #15

Quote:
Originally Posted by Looneybomber /forum/post/13011633


Whoa. You would be a good candidate for room treatments and some eq.

Yes sir!
I'll tell my wife that the walls and carpeting need to be installed very soon or else the sub will not work anymore. Hehehe.
 

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Discussion Starter #16

Quote:
Originally Posted by exojam /forum/post/13011655


I would most defiantly agree with Looney on this one. I believe a lot of folks use a BFD to eq with. On the room treatments, if you have the time you can make some nice ones yourself.


http://www.avsforum.com/avs-vb/showt...ghlight=exojam


Forgot to ask, have you tried relocating the sub to see how different placements of it affect the readings?

Nope, haven't done that yet. I'm a bit confused to as to where to place the spl meter. That reading, the spl was place about 1 to 2 ft from sub. Should I put it on the listening position?


This is how it was when I made that measurements.
 

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Place it at the listening position. By the looks of that picture you have an IB, or maybe I just am not looking at the picture correctly. If it is an IB there will not be any repositioning of it unless you have not made a final home for it. If not an IB, first place the SPL at the listening position, take a reading see what you have. Then try different locations where it is feasible that the sub could be located and try some more.
 

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Discussion Starter #18

Quote:
Originally Posted by exojam /forum/post/13011722


Place it at the listening position. By the looks of that picture you have an IB, or maybe I just am not looking at the picture correctly. If it is an IB there will not be any repositioning of it unless you have not made a final home for it. If not an IB, first place the SPL at the listening position, take a reading see what you have. Then try different locations where it is feasible that the sub could be located and try some more.

You are correct. It will become an ib in the future but now, it's acting like a sealed sub with some few opening at the bottom. I'll try making a new reading again but this time at the listening position.


Thank you so much exojam. I learned a lot today!!!
 
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