# The Perfect RTA Target Curve



## xpacpal1x (Apr 10, 2012)

I notice there are at least a couple threads discussing the perfect RTA curve, but I don’t think anybody has ever offered the following evidence or logical support. I’m looking for corroboration or rejection of my viewpoint from those with technical understanding of sound, recordings and electronics.

Again, I know RTA curves have been discussed elsewhere, but there’s always uncertainty regarding the best target curve. I think the answer is simple…the best target curve is the straight line I suggest below. Of course, if you want more bass or treble, you may adjust accordingly, but it seems to me that the ultimate RTA target curve should be a straight line (logic follows).

The screenshot is of a pink noise tone (Sheffield, I believe) file playing in my computer…note I say “in” my computer, not out of speakers. This is not an RTA microphone capture of actual sound waves. The spectrum analyzer program captures the sound intensity of a recorded file. Why, then, isn’t this the “perfect” RTA curve? Well, at least for those tuners using this specific pink noise file as their ‘reference’ tone. In other words, isn’t the perfect stereo system that which perfectly replicates the intensity of the recorded file? So, at least when using this specific pink noise track as the reference tone, the perfect RTA curve target should be a straight line with the displayed angle of slope. Right?

BTW, this validates what many suggest when they say, “when you tune to a flat line, the sound will be too bright.” Again, I agree with that, because this pink noise tone definitely slopes downward…while it is straight, it is not flat. For reference, it looks to me like it’s sloped down 10db from 63hz to 200hz and down 20db from 200hz to 20,000hz…at least that’s what I’ll try to target as I choose EQ settings. Why wouldn’t this create the most “realistic” tuning? Seems to me there shouldn’t be any argument regarding this point…then any variation is only to adjust to a listener’s preference for bass or treble balance.

Lastly, I notice that other test tones also exhibit the same downward slope of the Sheffield(?) pink noise tone. I also have log tone sweeps and individual 31-octave test tones that exhibit a similar rate of degradation of intensity as the frequency increases.


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## ndm (Jul 5, 2007)

xpacpal1x said:


> I notice there are at least a couple threads discussing the perfect RTA curve, but I don’t think anybody has ever offered the following evidence or logical support. I’m looking for corroboration or rejection of my viewpoint from those with technical understanding of sound, recordings and electronics.
> 
> Again, I know RTA curves have been discussed elsewhere, but there’s always uncertainty regarding the best target curve. I think the answer is simple…the best target curve is the straight line I suggest below. Of course, if you want more bass or treble, you may adjust accordingly, but it seems to me that the ultimate RTA target curve should be a straight line (logic follows).
> 
> ...


Does this program have the ability to hook up to the RCA's and test the line level. I am looking for a decent spectrum analyzer but dont have the $$$$ to splurge on something I wont really use that often.


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## xpacpal1x (Apr 10, 2012)

I do not know about the spectrum analyzer...I downloaded it as a free trial...it seems to be working only in a limited capacity, with many features turned off. Nonetheless, it served my purpose to create a graphic representation of what's actually recorded on a pink noise test tone file.


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## xpacpal1x (Apr 10, 2012)

So, almost 100 forum members viewed my post and none can either corroborate (i.e., agree with, or validate with additional facts) my assertion or disagree with it. Hmmmm. I will try once more... Bump.

Again, my question is, if the pink noise source file displays a downward sloping, straight line profile in a spectrum analyzer, isn't the best RTA target curve the same downward sloping straight line?


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## Jepalan (Jun 27, 2013)

An RTA will not display pink noise the same as a spectrum analyzer sweep. Pink noise will display a flatline on an RTA and a sloped line on a spectrum analyzer. This is due to differences in how the measurement is made. An RTA uses variable width filters that get wider as frequency increases.

You probably aren't getting much response because this has been discussed many times over. First read though all the responses in these threads:

http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/11579-flat-response.html
http://www.diymobileaudio.com/forum/how-articles-provided-our-members/12096-comparison-various-measurement-methods.html

Another good read:
http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/131029-target-curve-comparison.html


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## Justin Zazzi (May 28, 2012)

Jepalan said:


> An RTA will not display pink noise the same as a spectrum analyzer sweep. Pink noise will display a flatline on an RTA and a sloped line on a spectrum analyzer. This is due to differences in how the measurement is made. An RTA uses variable width filters that get wider as frequency increases.


Quoted for emphasis. RTA analyzers work differently than spectrum analyzers.

Very nice try xpacpal1x, but not quite right this time.


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## xpacpal1x (Apr 10, 2012)

Jepelan and Jazzi,

Thanks for your replies...this clears up an issue that has been bothering me for some time. I'll definitely strive for more of a flat line in the future.


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## Jepalan (Jun 27, 2013)

xpacpal1x said:


> Jepelan and Jazzi,
> 
> Thanks for your replies...this clears up an issue that has been bothering me for some time. I'll definitely strive for more of a flat line in the future.


To be clear, I wasn't recommending you tune to an RTA flat line target, only that an RTA will display pink noise differently than a spectrum analyzer.

Please read the discussion I linked titled "Target Curve Comparison". Tuning a car to an RTA flat line will almost always sound bad. 

Now, if you are just trying to achieve a consistent baseline before "tweaking to taste" (typically some shelf-boosted bass and high treble roll-off), then OK.


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## Patrick Bateman (Sep 11, 2006)

xpacpal1x said:


> I notice there are at least a couple threads discussing the perfect RTA curve, but I don’t think anybody has ever offered the following evidence or logical support. I’m looking for corroboration or rejection of my viewpoint from those with technical understanding of sound, recordings and electronics.
> 
> Again, I know RTA curves have been discussed elsewhere, but there’s always uncertainty regarding the best target curve. I think the answer is simple…the best target curve is the straight line I suggest below. Of course, if you want more bass or treble, you may adjust accordingly, but it seems to me that the ultimate RTA target curve should be a straight line (logic follows).
> 
> ...


I don't think there's one curve which will work for everyone.
You have to factor in the ambient noise level of the car, whether it's tuned for listening on the freeway or cruising down a city street, the directivity of the speakers, etc.

Music plays a role too; I find that I like to boost the low end with EDM, but that boost becomes fatiguing with other types of music.


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## cajunner (Apr 13, 2007)

Patrick Bateman said:


> I don't think there's one curve which will work for everyone.
> You have to factor in the ambient noise level of the car, whether it's tuned for listening on the freeway or cruising down a city street, the directivity of the speakers, etc.
> 
> Music plays a role too; I find that I like to boost the low end with EDM, but that boost becomes fatiguing with other types of music.


dynamic loudness circuits have that flaw, in that they don't analyze the type of music being played and adjust the various filters accordingly.

someone that had a brain, could take those ID tags that people use to index their music files, and produce a simple, 3 or 4 filter pre-sets for the dynamic compensation that would apply automatically to the type of music being played.

good acoustic, "unplugged" stuff would not be 'chesty' vocals, gonzo heavy metal wouldn't lag on the double kick drums, and rap would throw out a hair trick on the first try...

haha...


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## bugsplat (Nov 7, 2014)

cajunner said:


> someone that had a brain, could take those ID tags that people use to index their music files, and produce a simple, 3 or 4 filter pre-sets for the dynamic compensation that would apply automatically to the type of music being played.
> 
> good acoustic, "unplugged" stuff would not be 'chesty' vocals, gonzo heavy metal wouldn't lag on the double kick drums, and rap would throw out a hair trick on the first try...
> 
> haha...


I've always hated that problem. Was not a big deal when you listened to one album (cd) as all the tracks are about the same. When multi disc systems came out running in shuffle mode could be annoying. When the mp3 movement happened I had a number is ripped albums that were just annoying as hell when they cycled in. I'd have to race through my eq to turn them down. I ended up editing the music files to turn down the gain in some ranges. Painfully time consuming but it was all that could be done. 

I'd love too see what you mentioned added to tags. Would be amazing to have your system auto apply your pre-sets.


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## xpacpal1x (Apr 10, 2012)

Jepalan said:


> To be clear, I wasn't recommending you tune to an RTA flat line target, only that an RTA will display pink noise differently than a spectrum analyzer.
> 
> Please read the discussion I linked titled "Target Curve Comparison". Tuning a car to an RTA flat line will almost always sound bad.
> 
> Now, if you are just trying to achieve a consistent baseline before "tweaking to taste" (typically some shelf-boosted bass and high treble roll-off), then OK.


Jepalan...you broke my mindblock on the issue of RTA versus spectrum analyzer...and while I haven't yet fully internalized an understanding of the reasoning, I can move on to other issues. So, thanks for that.

However, since you brought it up, it seems to me that there is still some elegance to the thought of a straight line RTA target curve, but maybe with less downward slope than I previously estimated.


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