# Does calibration really make a difference?



## htguy (May 14, 2008)

It may be wrong to ask this in a tweaker’s forum (and I hope I am not banned!), but how much of a difference would I notice if I calibrated my sub as compared to a non-calibrated sub? I have a very modest sub (the JBL L8400), and am not an audiophile. The sound system is used only for HT? Is there a really good chance that the difference will be noticeable, or will I not really know until I make the calibration? I don’t really want to spend $200 or so on equipment, and then not hear any difference.
Thanks


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## Rambo4 (Jan 25, 2008)

I am no expert, but I think your placement is your best advice from my own experience. If you are in a null, it'll be hard to calibrate anything properly without a lot of EQ. As far as anything else, a SPL meter measurement is a relatively cheap, quick, and worthwhile investment, combine that with the free REW software available here and you should get a good idea of where you stand acoustically. There other avenues you can take apart from EQ, such as sound absorbers and bass traps as many here know much more about than I. 

Basically, I found I was able to rid myself of major nulls and peaks with the placement and SPL measurement, then I tweaked after that with EQ. Did the trick for me.


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## brucek (Apr 11, 2006)

> Is there a really good chance that the difference will be noticeable,


No one can answer that question, because the only answer is, it depends.

You need to measure your response of your low frequencies and see how it looks.

If it follows a reasonable target, then the answer is that you don't require any changes.

If you had a +20dB peak at 50Hz, then that 50Hz is about all your hearing from your subwoofer, and you could at least benefit from moving the sub around to smooth your response.

The cost is a cheap Radio Shack meter and some cables. We know you have a computer..

brucek


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## htguy (May 14, 2008)

Thanks, I really appreciate these answers. From what I have read, it seems like the Behringer ECM5000 calibration mic at $50 is my best bet. I have access to an M-audio firewire solo. I read that moving the sub even a few inches can make a difference, depending on the room.


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## brucek (Apr 11, 2006)

Yeah, the ECM8000 is the best choice, and if you have a soundcard that has a built-in mic preamp (with phantom power), then you're good to go.

brucek


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## salvasol (Oct 31, 2006)

htguy said:


> ... but how much of a difference would I notice if I calibrated my sub as compared to a non-calibrated sub? I have a very modest sub (the JBL L8400), and am not an audiophile. The sound system is used only for HT? Is there a really good chance that the difference will be noticeable, or will I not really know until I make the calibration? I don’t really want to spend $200 or so on equipment, and then not hear any difference. Thanks


Where in Los Angeles??? 

Did you calibrated the rest of the system??? ... What I mean, Did you set up all your speakers to 75db??? ... That can be a starting point (if you haven't done it) :yes:


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## htguy (May 14, 2008)

I see that you are in Fontana. I am near West LA.
I have to reveal my ignorance. What does setting up speakers to 75db mean?


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## salvasol (Oct 31, 2006)

htguy said:


> I see that you are in Fontana. I am near West LA.
> I have to reveal my ignorance. What does setting up speakers to 75db mean?


That's the first calibration you do to the system ... here you set all speakers to get 75db with the SPL meter so they sound the same when using a test tone (What receiver do you have??? ... some have the auto-calibration feature, that's what I mean when I said set to reference level or 75db :yes


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## htguy (May 14, 2008)

I used the auto calibration feature of my receiver. My next step will be the SPL to double check the receiver.


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## htguy (May 14, 2008)

I have started to read the REW instruction pages. Boy, this seems confusing. It will probably make more sense once I get it running. Anyway, it seems like if I am using the Behringer mic with the REW, I will also need an SPL meter to calibrate the REW? Can use the Galaxy M130 for that purpose? Is the 130 better than the radio shack model?


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## brucek (Apr 11, 2006)

> Can use the Galaxy M130 for that purpose? Is the 130 better than the radio shack model?


Yes (if it's a Galaxy CM-140). The CM130 has no AC output.
The Galaxy CM140 is a good all-in-one choice for use with REW.

brucek


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## htguy (May 14, 2008)

Brucek- The cost of the 140 is about the same as the cost of the behringer mic and either the 130 or a radio shack meter. Since I am starting from scratch, I thought I would get the mic and a separate meter. From reading other posts, it seems like the behringer mic is slightly preferred over the 140? But, I also read on a post that the 130 is rated to only 125Hz, which makes it useless for sub measurements? Is that correct? So, if you were going to pick between the 140, and the Behringer mic/Radio shack meter combo, which would you recommend? Or, is the 130 OK for sub measurements? Thanks for your help with all of these basic questions.


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## brucek (Apr 11, 2006)

> if you were going to pick between the 140, and the Behringer mic/Radio shack meter combo,


I personally like the (ECM8000 with the XENYX preamp) along with a Radio Shack meter for rough level setting.

brucek


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## htguy (May 14, 2008)

brucek said:


> I personally like the (ECM8000 with the XENYX preamp) along with a Radio Shack meter for rough level setting.
> 
> brucek


I already have the M-audio firewire solo. Is that a suitable alternative to a XENYX?


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## brucek (Apr 11, 2006)

> I already have the M-audio firewire solo. Is that a suitable alternative to a XENYX?


Yep...

brucek


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## htguy (May 14, 2008)

After a lot of testing and working with the guru’s on this forum, I learned that REW won’t work with my older (non-intel) Mac computer. I would like to at least get some very basic measurements to determine if I have any severe bass frequency problems. I do have an analogue radio shack sound meter. I read someplace that is possible with a sound meter to manually do what REW does, but that would take hours. I noticed that there is a 15 Hz to 80 Hz test tone on the download page. Could I do the following as a “quick” way to test to see if my subwoofer could benefit from EQ: Play that test tone and see if the meter dips or jumps at any time?


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## brucek (Apr 11, 2006)

Go to the downloads page and download the manual method excel file that matches your meter type and then download the sinewaves  from that page and create a CD and you're set for hours of fun.

brucek


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## htguy (May 14, 2008)

Thanks. I was sort of trying to avoid that.


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## htguy (May 14, 2008)

I forgot to ask, what volume do I set the subwoofer at for the tests? Do I calibrate it to 75db to match the volume from my other speakers while running a pink noise test tone?


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## Andysu (May 8, 2008)

htguy said:


> Thanks, I really appreciate these answers. From what I have read, it seems like the Behringer ECM5000 calibration mic at $50 is my best bet. I have access to an M-audio firewire solo. I read that moving the sub even a few inches can make a difference, depending on the room.


More so if you where to move a few inches like side to side forwards or backwards or downwards and slightly upwards from the original position and, you’ll hear a slight difference.


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## salvasol (Oct 31, 2006)

htguy said:


> I forgot to ask, what volume do I set the subwoofer at for the tests? Do I calibrate it to 75db to match the volume from my other speakers while running a pink noise test tone?


Sorry you couldn't make REW work.

You can try playing the 80Hz test tone and set the SPL to read 75db ... then play the rest of the tones and write down the reading you're getting. I think you can input the results into REW to see a graph; I did it but I use Windows XP ... :yes:


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## clausdk (Jun 28, 2007)

htguy said:


> It may be wrong to ask this in a tweaker’s forum (and I hope I am not banned!), but how much of a difference would I notice if I calibrated my sub as compared to a non-calibrated sub?  I have a very modest sub (the JBL L8400), and am not an audiophile. The sound system is used only for HT? Is there a really good chance that the difference will be noticeable, or will I not really know until I make the calibration? I don’t really want to spend $200 or so on equipment, and then not hear any difference.
> Thanks


In my system its like night and day with and without calibration.

I can run the bypass on the BFD and in an instant you can hear the sound with and without the BFD doing its magic.

I'm down to using 2 filters right now and thus removing a HUGE peak around 35 hz in my room.

When I run demos for people who come over I sometimes switch the BFD in and out and they are really surprised about the difference.


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## htguy (May 14, 2008)

For some reason I can’t get the test tones on the download page to play. I downloaded them on a mac, and copy them into itunes, and itunes shows zero length for the file. When I download on a PC, windows media player plays the file, but there is no sound (yes, I have the vol turned up). Is there a trick to playing these tones? Can I use the signal generator in REW instead?


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## brucek (Apr 11, 2006)

> For some reason I can’t get the test tones on the download page to play.


I can't see any reason why this is happening.

I just tried it a couple of different ways. I simply click the index.html link and it asks if I want to open or save the file.

If I click open it lists all the different tones. If I click one it plays the tone.

If I click save, it puts the index.html file in the location in my computer and it plays the tones when I open it??

OK, you're just messing with us , right?

brucek


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## htguy (May 14, 2008)

I got the tones to play on my PC at work. At home I only have Macs. I am new to all of this stuff. I am embarrased to say, but I had some of my outputs muted on the sound control panel when I was learning about calibrating a sound card. I forgot that I had them checked. I am sure I am doing something equally as simple with my Mac at home.


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## htguy (May 14, 2008)

Progress. I got the REW signal generator working, and sending a signal to the sub. Doing a quick sweep, looks like I have a peak some place between 55 and 65. I will do the time consuming test later. My wife thought the test tones were annoying. After I showed her the REW program and the meter, she at least now thinks this is mildly interesting.


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## htguy (May 14, 2008)

Here is the result of my first graph. I used a RS analog meter, and I downloaded the excel spreadsheet. The signals were from the REW generator, Sine Wave. No dither added to output. RMS level dB FS at the default -20.0. My sub is crossed at 80, so I stopped testing above 100. I started at 10. Looks like I could use some EQ, but does this graph look "right?" Are the RS correction factors in the excel spreadsheet the most current ones? Thanks in advance.


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## brucek (Apr 11, 2006)

> Are the RS correction factors in the excel spreadsheet the most current ones?


Yes, they match the downloadable .cal files (as long as you chose the one for your meter).

If you have a sub that you know will not reach down to 10Hz (given its specifications) then I would recommend not measuring that low. The problem is that noise can be interpreted as signal at those very, very low frequencies and with the compensation at 10hz which can be ~30dB with the old RS meter, it results in false readings. I would limit my bottom end measures to 16Hz.

Other than that, it looks like a legitimate graph of your response. You have a couple dips at 30Hz and 45Hz. You will have to attempt a few other positions to see if you can alleviate the problem - then decide if it makes sense to move the sub...

brucek


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## htguy (May 14, 2008)

Thanks. So, because I have "dips" instead of "peaks," does this mean that I would not really benefit that much from an equalizer like the BFD? I read that EQ can not help much with a dip, but it can bring down the peaks. I do not have many options for the sub in my room. If moving the sub does not even out the curve, would it help to use the BFD to bring down the "peaks" at 36 and at 50? Would that allow me to better hear the entire range of frequencies from the sub?


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## brucek (Apr 11, 2006)

> So, because I have "dips" instead of "peaks," does this mean that I would not really benefit that much from an equalizer like the BFD?


You really need to do some placement tests with your sub to see if you can get a bit smoother response. Your response is going up and down through some dips and peaks, so you may be able to help it a lot with placement.



> I read that EQ can not help much with a dip, but it can bring down the peaks.


If you have a dip caused by an out of phase reflection, and so throwing some gain at that frequency will also increase the out of phase signal that's causing the problem. In that case you could add gain forever and you won't get rid of the dip. Moving the position a little might help though.



> would it help to use the BFD to bring down the "peaks" at 36 and at 50?


As long as you don't cut too much, and if you have the headroom to boost the sub back up, it would help.

brucek


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## htguy (May 14, 2008)

I moved the sub a little, and that made virtually no difference. I only have two other places for the sub. One is in a corner, and the other is a few feet from that corner. Both graphs are attached. It seems like I have problems no matter where the sub goes. Would EQ fix one of these positions better than the others? Room treatments are not an option.
Thanks


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## brucek (Apr 11, 2006)

The second plot is a bit better. Removing the peak at 36Hz would probably help out.

It would be a lot easier if you were to get REW working. Do you not have an old PC around?

brucek


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## htguy (May 14, 2008)

I have been working on trying to fine someone who will let me borrow a PC for a while.
Thanks


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