Frequency Response Charts

[gellor]

I was just wondering if there is an actual software package that y'all use to make the frequency charts (like the one below) or if this is just curve-fitting in an Excel graph or something.

 

[brian32672]

Are you thinking about testing one speaker (for speaker building) or your in room response?

 

[gellor]

in-room response. (that may not have been the exact correct picture to use, but it was the first one I found)

I suppose this one might have been a better choice...(one of the ones from Home Theater Mag)

 

[brian32672]

Well you can just do a plot for your FR with just a paper/pen & RS meter.
If you want a program (that actually will work with the RS meter)
There is a free version, but the paid version is what you will need. (preferably level 4)
TrueRTA - http://www.trueaudio.com/rta_abt1.htm

There are others, but this is pretty much the most popular.


You can also try this one (its free as well, and you will not need a paid version)
I have not used it (yet) but plan on trying it soon.
http://www.avsforum.com/avs-vb/showthread.php?t=529224&page=1&pp=60

 

[Buckle-meister]

Well you can just do a plot for your FR with just a paper/pen & RS meter.

Eh? You'll need some way to generate either discrete or continous tones depending on the accuracy required.

Brian, the link from AVS forum "around 2-3 minutes to measure 20-120Hz in 1Hz steps" is pretty slow compared to the likes of ETF which will take a 20Hz to 20kHz sweep in five seconds.

For this reason Gellor, I'd recommend the free (cut-down) version of ETF, the use of which will require that you have a computer with appropriate soundcard, some cables and adaptors, and the RS meter (or equivalent). Be aware though, that you will get back something similar to this as opposed to any of the graphs you posted, the first of which shows the weighting curves used by the RS meter and the second of which looks to have been averaged.

Regards

 

[brian32672]

Eh? You'll need some way to generate either discrete or continous tones depending on the accuracy required.

OOPS my bad, I forgot to mention TrueRTA has a tone generator.

Also, Buckle - I had said "I had never used that program on AVS (Yet)"

You can also use the frequency sweep that is in DVE or Avia as well.
Also there are a lot of free tone generator programs on the net. Just do a Google search on tone generator.

Here are a few -
http://www.realtraps.com/test-cd.htm
http://www.world-voices.com/software/nchtone.html
http://educate-yourself.org/nch/
http://www.hitsquad.com/smm/programs/TTG/

EDIT:: Also I recommend reading this - http://www.avsforum.com/avs-vb/showthread.php?t=572477
Specially the part on why not to use 1/3 and 1/6 octave testing. Which is also explained in the realtraps link.

 

[Buckle-meister]

...there are a lot of free tone generator programs on the net.

Yes, but playing tones, manually recording the SPL for each and plotting the results is pretty time consuming. It would be totally impractical to obtain a full-frequency sweep this way. Playing tones manually also gives only the frequency response, when ETF (or other equivalent programs) give you much more information besides.

Regards

 

[brian32672]

Yes, but playing tones, manually recording the SPL for each and plotting the results is pretty time consuming. It would be totally impracticle to obtain a full-frequency sweep this way. Playing tones manually also gives only the frequency response, when ETF (or other equivalent programs) give you much more information besides.

Regards

Ok, thats why I will show this.

The graph below shows the response at the listening position in a typical 16 by 10 by 7-1/2 foot room. Note the peak/dip pair at 110 and 122 Hz where the response varies a staggering 32 dB across a range smaller than one musical whole step. This behavior is completely hidden when measured at 1/3 or even 1/6 octave spacing.

To solve this problem we created a series of MP3 files you can download and burn to a CD. Our intent is not to duplicate all of the features of commercial test CDs. Therefore, we supply only low frequency sine waves, in 1 Hz increments, with a track organization that's easy to understand. We also created a blank sheet of logarithmic graph paper you can print to plot the results.

You can use any inexpensive Sound Pressure Level (SPL) meter such as those sold by Radio Shack. Simply place the meter where your ears are when seated in the listening position, play the CD, and write down each number displayed by the meter. Each tone is ten seconds long, which gives you enough time to switch the meter range when needed. Yes, it will take the better part of an hour to run these tests, but when you're done you'll know your room's true low frequency response.

 

[Buckle-meister]

Yes, it will take the better part of an hour to run these tests, but when you're done you'll know your room's true low frequency response.

What about 5 seconds for a full-frequency room response? Plus other helpful parameters?

Regards

 

[brian32672]

What about 5 seconds for a full-frequency room response? Plus other helpful parameters?

Ok, Ok, fine I am now downloading yet another program... Sheesh....

I am assuming that all functions work in the demo version?
Anyhow, I will play around with it later tonight....

 

[Buckle-meister]

I am assuming that all functions work in the demo version?

...I'd recommend the free (cut-down) version of ETF...

Nope. But for the full and/or low-frequency plots that Gellor was enquiring about, it'll do just fine.

Regards

 

[gellor]

I just wanted to say thanks for all the helpful responses.