Plots and graphs and stuff (1 Viewer)

[Shane Morales]

How the hell do you make the frequency response plots/graphs for your speakers? Any past threads discussing this?

I have a feeling that if I make one of these for my system it will be really bad.

 

[Shane Morales]

I think I figured some of it out.

You use some kind of tone generator prog like WinISD to play some tones at regular hz intervals. Using an SPL meter you take measurements of the db reading for each tone. Then you plot it. Right?

Do you do this one speaker at a time or with all of them running? I know you do the sub by itself. What about everything else?

Then what? You can use something like a BFD on your sub, but what about the other speakers. Once you have the graph, then what?

 

[ChrisWiggles]

Then you try to EQ your sub. I wouldn't EQ main speakers, IMO.

 

[Robert AG]

Head over to here and buy the software and a calibrated microphone.

http://www.trueaudio.com/

 

[Wayne A. Pflughaupt]

Shane,

You’re on the right track. The preferred method is to use a spectrum analysis software program like TrueRTA or ETF because it’s the easiest. You can do individual test tones and map your plot on graph paper, but as you can imagine this can be a pretty daunting task if you’re talking about doing all the speakers. As far is the intervals for readings, 1/6-octave is acceptable, but naturally 1/12-octave is better, if you’re feeling brave.

Then what? You can use something like a BFD on your sub, but what about the other speakers. Once you have the graph, then what?

As I mentioned, if you aren’t/can’t equalize the main channels, the exercise is for informational purposes only. In order to equalize the mains you will obviously need one EQ channel for each main channel. And they have to be connected between the pre-amp and amplifier sections – which translated means you need pre-out/main-in jacks or outboard amplifiers for each channel you plan to equalize. As you can see, this can get pretty pricey, even if you go with cheap equalizers (which I don’t recommend).

I know equalizers often get a bad rap, especially if used on the mains, but IMO it’s because of people mis-using them and/or using cheap ones.

Regards,
Wayne A. Pflughaupt

 

[Christ Reynolds]

could this be done with excel and a rat shack spl meter? i plan on doing this for a little demo project for one of my electronics classes. honestly, appearance takes precedence over accuracy. i wont be calibrating these speakers, they actually arent good speakers, in comparison to my amp. however, i'd like to be able to make nice looking graphs for this project. anybody have any tips? or is it just as easy as plugging numbers into excel and plotting the db readings as a function of frequency? it may be a lot of work using excel, but i am limited to the tools i have access to. thanks for any help.

CJ

 

[PaulDF]

Do you do this one speaker at a time or with all of them running? I know you do the sub by itself. What about everything else?

This might be a little late, but don't measure the sub on its own with intent to use the results for equalizing. The interaction of the whole system must be measured while they crossover to the sub.

The only reason to measure the sub on its own is to find out its anechoic (no room interaction) frequency response. And this should be done at close range (within 1 m) and preferably outdoors. Though the middle of a room will do, if measured nearfield.

 

[Edward J M]

Wayne kicks ass - great forum resource. That is all; carry on.

 

[Brian L]

could this be done with excel and a rat shack spl meter?

Sure. While I have played around with SpectraPLUS, I decided I hated dragging the PC around, so I went back to the poor man's route.

The trick is to get discrete test tones. There have been links posted here and there with downloadable tones, or you can buy a CD with discrete tones (I use Bass Mekanix 5.0). BM 5.0 has tones from 20 hz to 99 z in 1/2 hertz increments. Perfect for EQ work. FWIW, in my room, these produce the most stable readings of any tones I have tried.

BGL