Target Curve Comparison - Car Audio | DiyMobileAudio.com | Car Stereo Forum

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Old 06-08-2012   #1
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Default Target Curve Comparison

This thread may spur some discussion, or it may not. I often see people ask about what final "curve" they should tune their system to. You see responses range from things like: flat, "smiley face", ELC (equal-loudness contour), gentle slope downward, the "JBL Curve" (provided by Andy W.), etc. It just so happened I decided to do a bit of research on the topic while I had some down-time recently and wanted to share my findings. Everything below was obtained from simply using Google Search.

So, let's start with the curves written out. I ended up settling on five different curves. Any explination/logic I found about why these curves exist will be shared below said curve.

1.) JBL/Andy W. Curve:

-20-60hz: +9db
-60-160hz: Transition to 0
160-3khz: Flat (0)
3khz+: Gradual Roll-off to -6db @ 20khz

* Andy has stated this target response is the "ideal response for a small listening environment" with a bump on the low-end to compensate for typical listener preference.

https://www.diymobileaudio.com/forum/...20response.jpg

2.) Crutchfield Labs Curve:

-20-125hz: +6db
-125-200hz: Transition to 0
200-12.5k**: Flat (0)
12.5-16khz: Roll-off to -3db
16-20khz: Roll-off -6db (-9db total)

**This range includes a +1db bump at 400hz, a -1db dib at 10khz, and a +1db bump at 12.5khz.

* This target curve was in a recent edition of Crutchfield Labs. Here is the only comment I found to the logic behind it, "This represent's Jeff's ideal sound curve, one that helps overcome some of the limitations that appear when you listen to music in a moving vehicle."

Crutchfield Car Stereo Proving Ground

3.) Audyssey Curve:

20-1khz: Flat (0)
1-3khz: -3db dip
3-10khz: Roll-off to -1.5db
10-20khz: Roll-off -3db (-4.5db total)

* This "popular" curve is the closest I found to flat that some people recommend. I also thought the logic behind the curve was interesting. The roll-off on the top-end is performed as a gated measurement. This eliminates reflections being added to the measured response. Ungated response will be "whatever it is" after reflections are accounted for, but it should be close to flat. This leaves the small dip. It was explained that because of the popularity for 8"/1" and 6.5"/1" speaker combos (both in home and car), we have become accustomed to and prefer the sound of a directivity mismatch, and the dip in power response, and therefore Audyssey "tunes it in" even if it isn't needed. They also flatten the response of the sub up to around 3khz, add the crossover at 80hz, and allow the end-user to adjust sub output if they perfer a boost on the bottom end (similar to all the other graphs)

4.) Audio Control Curve

-20-40hz: +6db
-40-250hz: Transition to +1db
-250-2khz: Transition to 0db
-2-20khz: Roll-off to -5db

* It seems this curve was included in the manual with the old Audio Control RTA's. The manual basically said, "Flatten response as much as possible (you won't like it), and then adjust to something approximating this curve." I found this information on diyaudio.com I believe if you want to dig further.

5.) B&K Curve

-20-160hz: +3db
-160-2khz: Transition to 0db
-2-20khz: Roll-off to -3db

* There is a long PDF about this curve which I've attached. It seems to be well-received in mimimum phase systems (which the car ISN'T), but I wanted to include it because it also represents the people who like a smooth and steady roll-off.

http://www.bksv.com/doc/17-197.pdf

And for those of you who are visual learners...a graphical representation of all the curves and an average of all the curves:


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Last edited by pionkej; 06-08-2012 at 03:08 PM..
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Old 06-08-2012   #2
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Default Re: Target Curve Comparison

If this thread does generate some discussion, I'd like to point out up front that this is just one helpful tool in the "game" of tuning. There are MANY other factors out there besides a target curve that need to be considered and I suggest people read up on them before aiming for this. Things like phase response, polar response, and power response all need to be considered.

There are many ways to get to the "finish line" and if you choose poorly you could end up with a "perfect curve" and system that sounds like crap.

For example, I could cross the 6.5" midbass in my door at 50hz and 5khz. I then boost the low end flat (and beyond xmax) to meet the sub and the top-end to flat (to compensate for beaming/off-axis response) to meet the tweeter. The graph may look nice, but I've introduced distortion from exceeding xmax (and may kill the speakers too) and created a terrible mismatch in power response (because the midbass is beaming and the tweeter is omin-directional).

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Old 06-08-2012   #3
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Default Re: Target Curve Comparison

great right up....i posted a thread yesterday similar to this in terms of (among other things) trying to understand the logic behind a few of the curves (JBL and Crutchfield)....didn't even know about these other curves however.

Please note that on your graph, you placed the 400hz 1 db boost of the crutchfield curve incorrectly at 4000k mark instead of 400.

Last edited by Libertyguy20; 06-08-2012 at 11:40 AM..
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Old 06-08-2012   #4
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Default Re: Target Curve Comparison

Quote:
Originally Posted by Libertyguy20 View Post
great right up....i posted a thread yesterday similar to this in terms of (among other things) trying to understand the logic behind a few of the curves (JBL and Crutchfield)....didn't even know about these other curves however.

Please note that on your graph, you placed the 400hz 1 db boost of the crutchfield curve incorrectly at 4000k mark instead of 400.
Good catch. I've edited the original post and moved the bump to 400hz.

Also, I wanted to point out that I personally aim for my frequency response to not vary more than 3db per octave from my "target curve". I do aim for less than that, but 3db is my "threshhold". I say this because I'd be hard pressed to care about any of the 1db peaks or dips in the Crutchfield response personally, but I included it anyways.

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Old 06-08-2012   #5
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Default

This is perfect! Ive been researching this exact topic... And not having the greatest luck.
Ive recently started "trying" to dial in my front stage with an rta.
I wont be much help, but looking forward to what others have to add.

Thank you for posting this.

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Old 06-08-2012   #6
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Default

This is what I was reading yesterday. I know its geared for home audio, but some of the "small room" stuff could carry over... Or I could be totally wrong.
http://www.hometheatershack.com/foru...ed-how-do.html
I get kinda lost between curves, equal loudness, etc. being new to Rta based tuning doesnt help either. Lol

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Old 06-09-2012   #7
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Default Re: Target Curve Comparison

Nice post. The one key piece of information you're missing is the METHOD by which you're measuring your loudspeakers.

Example: Is your mic directional? Omnidirectional? Or were they binaural microphones that take into consideration the directivity of the sound source/reflections and the shape of the listener's ear? Was it gated (i.e. you cutoff later reflected sounds that are ignored by the ear)? And are you measuring in a diffuse field or a free field? The relative intensity and direction of the different sound waves that strike your ear (i.e. direct + reflected and arriving at an angle) makes a BIG difference in the sound that ultimately strikes your eardrum.

You can take identical speakers in an identical room, but change around HOW you measure, and subsequently, you could "come up with" a whole bunch of different "target curves" that describe the exact same listening environment. That's why it's useless to talk about target curves without specifying the precise method/environment of the measurement.

If you're interested, here's another curve to add, it's for free-field measurement and it's based on blinded listener preferences to loudspeakers, including expensive or well-regarded ones.
http://www.aes.org/tmpFiles/elib/20120609/5270.pdf
It's doesn't really apply that well to the diffuse-field you get in a car, but it's still good for comparison. It would be nice if anyone knows of any JAES papers that talk about listener preference curves for in-car sound systems.

Last edited by smellygas; 06-09-2012 at 12:02 PM..
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Old 06-09-2012   #8
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Default Re: Target Curve Comparison

I have researched this quite a bit myself over the course of the past 2 years or so but I must say I don't think I have seen as many curves discussed so well all in one place. Subscribed for sure. I, too, would like an answer to the above post on how to measure for these curves. It is something I have always wondered myself. I use an omnidirectional mic (ECM8000) mounted flat and aimed straight ahead. I try to get the mic as close to where the center of my head usually is. I actually find that difficult as the mic is rather long and the seat headrest usually gets in the way. Maybe there is a better more accurate way to be aiming/placing the mic?
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Old 06-09-2012   #9
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Default Re: Target Curve Comparison

I have also read that taking multi- readings at different angles/positions and averaging them is necessary (spacial averaging). I have not really played with that too much as it is time consuming enough for me. The couple times I did, I noticed the high frequencies change immensely between readings (above 5 Khz or so).
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Old 06-09-2012   #10
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Default Re: Target Curve Comparison

Quote:
Originally Posted by smellygas View Post

<snip>...it's useless to talk about target curves without specifying the precise method/environment of the measurement.
I'll agree with your statement up to this point. It's only useless based on the assumption that the person measuring the listening environment is ignorant to the process and the choices they have when doing so. I think a discussion of the curves themselves and the perspectives behind them brings a separate and useful discussion to bear. Again, I agree, the process of measuring is as much or more important than the data it gathers but assuming a fundamental understanding of the measurement process this discussion stands freely and in its own right.

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Old 06-09-2012   #11
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Default

I'm more interested in the curves provided and how they were obtained. Sure, knowing how to measure is important, but knowing how a given was measured is at least equally important and arguably moreso. That's one thing I really see. And then when people try to lump in the equal loudness curve... It's just nebulous to discuss it without knowing the procedures taken to arrive at any result.


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Old 06-09-2012   #12
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Default Re: Target Curve Comparison

Just curious,

How accurately have phone rta apps been when compared to m-audio/true rta and other methods?

I have surprisingly similar results using true rta and the droid app RTA Pro

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Old 06-09-2012   #13
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Default Re: Target Curve Comparison

Quote:
Originally Posted by bikinpunk View Post
I'm more interested in the curves provided and how they were obtained. Sure, knowing how to measure is important, but knowing how a given was measured is at least equally important and arguably moreso. That's one thing I really see. And then when people try to lump in the equal loudness curve... It's just nebulous to discuss it without knowing the procedures taken to arrive at any result.


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Old 06-09-2012   #14
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Default Re: Target Curve Comparison

Quote:
Originally Posted by highly View Post
I'll agree with your statement up to this point. It's only useless based on the assumption that the person measuring the listening environment is ignorant to the process and the choices they have when doing so. I think a discussion of the curves themselves and the perspectives behind them brings a separate and useful discussion to bear. Again, I agree, the process of measuring is as much or more important than the data it gathers but assuming a fundamental understanding of the measurement process this discussion stands freely and in its own right.
Let me clarify. If you plan to EQ your system to match a particular target curve, but you don't know the method by which the target curve was obtained, then YOU CAN'T DO IT = useless. But great for discussion, I guess.

Example: Let's say I take the world's best sounding car stereo. And I record the freq response curve from pink noise using an [unknown measuring technique], then publish my curve for others to duplicate my incredible sound. Problem is, depending on the measurement technique used by the tuners trying to copy this "target curve," you will obtain a completely different final equalization. For instance, take the ubiquitous ECM8000. Aim it up and take a spatial average. Now aim it at each speaker and take an average. Quite different. Take binaural mics and take a spatial average. Different. And what's worse is that some of the curves above were measured in the free-field with mostly direct sound arriving from directly in front of the listener and reduced amplitude reflected sound coming from the sides. Car sound is direct sound coming more from the sides with near-equal amplitude early reflected sound coming from all around in a diffuse field. Completely different. So unless you match the technique, you can't reproduce the original sound signature. i.e. useless.

...and the result is people complain that XYZ Target Curve doesn't sound right, it's too bright, etc. It's not the target curve, it's the failure to match the measurement technique.

Last edited by smellygas; 06-09-2012 at 03:08 PM..
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Old 06-09-2012   #15
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Default Re: Target Curve Comparison

Quote:
Originally Posted by tyroneshoes View Post
Just curious,

How accurately have phone rta apps been when compared to m-audio/true rta and other methods?

I have surprisingly similar results using true rta and the droid app RTA Pro
Here is a good thread that someone just recently did. Used an Iphone4 w/ Studio Six and the mic/etc used in the first post

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Old 06-09-2012   #16
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Default Re: Target Curve Comparison

much like my experiences. The smartphone RTA apps work surprisingly well.

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Old 06-09-2012   #17
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Default Re: Target Curve Comparison

Quote:
Originally Posted by pionkej View Post
If this thread does generate some discussion, I'd like to point out up front that this is just one helpful tool in the "game" of tuning. There are MANY other factors out there besides a target curve that need to be considered and I suggest people read up on them before aiming for this. Things like phase response, polar response, and power response all need to be considered.

There are many ways to get to the "finish line" and if you choose poorly you could end up with a "perfect curve" and system that sounds like crap.

For example, I could cross the 6.5" midbass in my door at 50hz and 5khz. I then boost the low end flat (and beyond xmax) to meet the sub and the top-end to flat (to compensate for beaming/off-axis response) to meet the tweeter. The graph may look nice, but I've introduced distortion from exceeding xmax (and may kill the speakers too) and created a terrible mismatch in power response (because the midbass is beaming and the tweeter is omin-directional).
OK, thanks for the info. How about a little more on how to best set up one's system so that RTA is more effective? Maybe choose your crossovers and slopes wisely, set the levels on your drivers to match the target curve as close as possible to avoid excessive EQ, avoid boosting levels and EQ bands so that you do not drive the amplifier into clipping, etc?

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Old 06-09-2012   #18
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Default Re: Target Curve Comparison

Hey, guys, can we stay on topic here. The discussion is about target curves, not smartphone RTA's. There's a thread about that here:
https://www.diymobileaudio.com/forum/...-platform.html
Thanks.
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Old 06-09-2012   #19
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Default Re: Target Curve Comparison

Having spent many hours in my car over the past weeks with my new RTA toy this thread is very interesting and timely.
I also researched the topic and found the JBL curve, house curve, etc. Basically the target curve is just a starting point. The important thing is to be consistent in your measuring as you develop and refine your own curve to your own liking. Here are some takeaways-
*Mic position averaging. I did this at first by averaging multiple mic positions. However to simplify the process I did find a single position that duplicated the "average" curve. I use this mic position every time I fine tune for an RTA curve. Basically it's ear level, dead center in the driver's seat facing directly forward.
*Source. I use correlated pink noise full spectrum. Track 43 on the shefield lab disk.
*Software settings. Find what works and keep them consistent. Your are attempting to reshape a curve over time based on tuning, listening over a few days, re-tuning etc. It's not so important the shape of the curve but that you create the curve in the same way each "session". This way you can understand the relationship to the visual curve and the sound you are experiencing.
My first curve was way too bass heavy. I liked it at first but then had to re-tune it. Having the RTA available and using it the same way each time guarantees that I can go in and refine the bass part of the curve and possibly other frequency zones without affecting other areas- it is tuning with vision, not tuning blindly. You draw a line- if you don't like the sound, it's easy to reshape parts of the curve based on what you are hearing or not hearing.

Here is my latest curve- it is kind of radical but I like it so far. I'll live with it for a week and see if it needs more work.

Another important factor is that too much EQ (even if there is no boosting) can sound very bad at times. I've made more of an attempt lately to adjust to a given curve by setting crossovers, slopes and levels to minimize the amount of EQ needed. This definitely improves the SQ of the results no matter the curve shape.

-
One final comment- that crutchfeld curve article is registering high on my BS meter. With the way car interiors are these days it is highly doubtful they were able to achieve their resulting curve with only some aftermarket speakers and a receiver without advanced EQ or processing controls.

Make a curve- listen over a few days and note what you like / don't like as it relates to the frequency octaves/ refine your curve by measuring the same exact way and by adjusting to those findings/ repeat as necessary / pray that some day you can put away the microphone and cables. peace.
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Default Re: Target Curve Comparison

Smellygas-

I understand and appreciate your comments on how a curve isn't worth much without knowing how to get there. However, I would contest that it ISN'T nearly as confusing or difficult as you imply. I'd also contest that knowing how to properly achieve your target curve is more important than how you measure for it.

Let's look at it this way. If you dig deep though this forum, you'll find many people are happy with a tune that is "level" within +/-3db using 1/3oct smoothed resolution. The variance of the curves above look big because of the scale, but they are, in reality, all very close. In fact, outside of the two outliers (Audyssey & JBL) on the low-end (20-80hz) every curve is within 3db of the "average" I plotted. Even the outliers are only 4.5db out at that range. What does this mean? To me, it means that if you chose the average curve and accepted a +/-3db range mentioned above, you could satisfy nearly all of the curves.

Also, you mention directional mics...why? I don't think I have EVER seen anyone mention using a directional mic for measurements. That goes for pro audio, home audio, or car audio. So again...why? If you take that away, you are left with a omnidirectional mic and a binaural mic. If you use spatial averaging, neither will give you much difference in results. Ask Erin. Not to put him on the spot, be he bought binaurals and has gone back to using a single omni. From what I understand, it's because it's easier to use and when using spatial averaging, the results are NOT very different. If I'm wrong about that and there was a big difference, I'll eat my words and apologize.

So, on to where to measure and how to measure. Well, I vote for measuring at the listening position. This doesn't change for me, or most people that I know of, whether in the home or the car. You are right that the car is more reverberant than the home, and depending on how you measure (gated or ungated) it WILL affect what the final sound is. Fortunately, because of the size of the listening space, nothing below the treble range changes much anyway (see image below). In fact, with a 5msec gated test vs an ungated one, I have no difference in FR from below 10khz. Granted, there is a 15db difference between the two at 20khz, but odds are the only speaker affected is the tweeter, so it isn't like trying both options and seeing what you prefer would affect any tuning beyond said tweeter.

All of this brings me back to the fact that I, PERSONALLY, feel that measuring system response is the easy part. Getting to the target is the difficult part.


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Default Re: Target Curve Comparison

Quote:
Originally Posted by bikinpunk View Post
I'm more interested in the curves provided and how they were obtained. Sure, knowing how to measure is important, but knowing how a given was measured is at least equally important and arguably moreso. That's one thing I really see. And then when people try to lump in the equal loudness curve... It's just nebulous to discuss it without knowing the procedures taken to arrive at any result.
Erin,

From all that I've read about the ELC lately, I feel there is ZERO need to factor it in IMHO. I know you already know this, but I thought it was a good time to share why since I feel I've read some good stuff on it lately. First off, it isn't accurate to material such as music. The ELC is based on people listening to individual pure tones and ranking them based on when they "equal" a 1khz tone in output. If anybody wants to know more about this part, go look at "A Weighted Curve" on wikipedia. Next, jcollin76 gave a useful link to "House Curves" from HTS. Here is a take on why tuning for a target curve doesn't degrade how the recording was mastered or why the ELC doesn't need to be incorporated. It is one man's opinion, but I felt there was enough logic behind it that I've jumped on board.

Part Three
Answering house curve critics


Every theory in audio has its proponents and detractors. However, as we’ll see, room curve detractors typically don’t have a good understanding of what it is, nor of its function.


A house curve built into recordings?
One thought critical of house curves is based on a rather idealistic concept of the recording studio environment and exactly how it affects our program material. The following is from a house curve discussion thread a few years ago on another Forum:

”Consider a properly set up mixing booth in a studio. The mixing engineer is listening to either nearfield monitors or other speakers when he is laying out the final 'sound' of the music that is being mixed down to two (or more) channels. If the physical space and hardware has been designed properly (including the choice/location/EQ of the monitoring speakers), the frequency response at the mixing position should be flat from 20 Hz to 20 kHz. Neither the booth nor the mixing electronics should add or subtract from the sound on the master tape. If you wish for your home system to be accurate, it needs to be as flat as the one they used in the studio.”

Here’s the problem with this idea: If the mixing engineer’s monitoring system is as flat as all that, it will sound as bad to him as it does in your living room! There’s no way around it; a properly-tuned studio monitoring system will also have an appropriate house curve for the room it’s in. It has to. If not, the engineer is simply going to compensate with equalization. Good engineers know that their room and speakers of choice will affect their final mix. That’s why they usually demo it in different environments before they finalize it.

Another thought critical of house curves acknowledges and indeed embraces the fact that they come into play in the production stage. It holds that a room curve at home isn’t necessary because it’s built into the product’s final mix. Therefore – once again - we should set up our systems with response as flat as possible, otherwise nothing will sound right.

Nice idea, but as we’ve established, very few people actually think flat in-room response sounds good on their playback system.

Furthermore, the question needs to be asked: which house curve are they using in that mixing studio – small room, large room, or something in between? As we saw in Part Two, room size matters tremendously, and once again this can’t be understated. After all, the engineer can reasonably expect that his CD will be played back in cars, dorm rooms and living rooms. What about the DJ spinning tunes in a huge hotel ballroom or at an outdoor event? What a dilemma: Which house curve is our hapless engineer supposed to “build in?” Obviously something fundamental is missing from the built-in curve theory: an industry standard.


A Fletcher-Munson house curve?
Other room curve skeptics base their doubts on the Fletcher-Munson curves, which show deficiencies in human hearing at the lowest and highest frequencies. They claim that studio engineers, being human themselves with the same auditory deficiencies, compensate for that in the recording process. The following was also presented on a discussion thread a few years ago:

“The engineer who mixed the material you are listening to has the same hearing response you do, that is less sensitive to lower bass frequencies. Do you think he would increase them to compensate? Of course he will.

“Now, enter a concept like a house curve to this equation. If your playback system has a curve attempting to compensate for a frequency response associated with human hearing, what do you think the results will be when you play back material that was mixed and prepared on a flat system?

“Well, you'll be re-compensating, adding again the same compensation curve that the engineer added.”

This critic’s disapproval is fundamentally flawed because it’s based on the notion that a house curve is synonymous with the Fletcher-Munson curves. It isn’t. The Fletcher-Munson curves show how our perception of bass and treble frequencies change with variations in volume levels. That is a wholly separate phenomenon that has virtually nothing do with a house curve, other than the fact that it's best to calibrate your system at the volume level you use most. As we’ve thoroughly established, a house curve is compensation for the room, not the ear.

Along the same lines we have this complaint:

The problem with a "house curve" is that it's a static solution which only works at one playback volume. It may be inadequate at lower volumes, and it may be overly intrusive at higher playback volumes.

I have not found this to be the case at all. Calibrate your system and house curve for the level you normally listen and you’ll find that it will be adequate for most listening from that point, except perhaps for extreme level variations. With extreme changes from your normal settings you aren’t doing critical listening anyway – e.g. ultra-low levels for background music, or ultra high when you’re “showing off” the system's capabilities. In these instances, all that’s needed (if anything) is a simple level adjustment of the sub, not a total re-curving.

Read more: House curve: What it is, why you need it, how to do it! - Home Theater Forum and Systems - HomeTheaterShack.com


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Old 06-09-2012   #22
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Default Re: Target Curve Comparison

See my comments below:

Quote:
Originally Posted by avanti1960 View Post
*Mic position averaging. I did this at first by averaging multiple mic positions. However to simplify the process I did find a single position that duplicated the "average" curve. I use this mic position every time I fine tune for an RTA curve. Basically it's ear level, dead center in the driver's seat facing directly forward.

I wouldn't do this personally. It is stupid easy to take averages with TrueRTA (which I see you use) and it WILL be more representative of your system if you take averages. Just start measurement, stop, hit Alt+1, repeat for six measurements. Go to Utilities and average all six (I like to save as 20). I do all of this at 1/6 octave. After it's done, I go back to utilities smooth the response to 1/3 octave and evaluate from there.

Here is my latest curve- it is kind of radical but I like it so far. I'll live with it for a week and see if it needs more work.

Try what I said above about 1/3 smoothing and repost. You may find it isn't so radical.

Another important factor is that too much EQ (even if there is no boosting) can sound very bad at times. I've made more of an attempt lately to adjust to a given curve by setting crossovers, slopes and levels to minimize the amount of EQ needed. This definitely improves the SQ of the results no matter the curve shape.

Many times if you try and "fix" high Q peaks with EQ (like those found on 1/6 octave tuning), you can ruin the sound. It is another reason I prefer 1/3 octave smoothed. The only exception to this is when looking for modes (below around 300hz). There, I would use something like 1/24octave, a slow sine sweep, and peak hold settings. I haven't done this part yet, but I know others who have with success, I plan to do it myself on my next tune, and that's why I feel comfortable recommending it.

Make a curve- listen over a few days and note what you like / don't like as it relates to the frequency octaves/ refine your curve by measuring the same exact way and by adjusting to those findings/ repeat as necessary / pray that some day you can put away the microphone and cables. peace.

Pretty much truth here. Make sure when tuning you try and do it in small doses and you step back and evaluate. Some of my worst tunes came from sitting in the car too long at one time. I end up "fixing" things that were fine and I hate the sound the next day. So, take your time and make small adjustments, evaluate, and repeat until happy (if you're ever happy).

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Old 06-09-2012   #23
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Default Re: Target Curve Comparison

Quote:
Originally Posted by pionkej View Post
Smellygas- Let's look at it this way. If you dig deep though this forum, you'll find many people are happy with a tune that is "level" within +/-3db using 1/3oct smoothed resolution.
Thank you for the thoughtful reply. My opinion is that +/-3dB at 1/3 oct smoothing, depending on where the peaks/valleys are, can sound okay to pretty bad. My personal goal is to get something close to what I can get from a reference home audio setup.

Quote:
The variance of the curves above look big because of the scale, but they are, in reality, all very close. In fact, outside of the two outliers (Audyssey & JBL) on the low-end (20-80hz) every curve is within 3db of the "average" I plotted.
Having done a lot of EQ for years, my experience is that much smaller corrections over smaller bandwidths can make BIG differences in sound quality. My perspective is that those curves are completely difference. Even a wide bandwidth boost/cut of +2dB over the treble can make a big difference in "brightness."

Quote:
Also, you mention directional mics...why? I don't think I have EVER seen anyone mention using a directional mic for measurements.
Keep in mind that even mics we call "omnidirectional" are actually quite directional. Take the ubiquitous ECM8000. It's polar response is not flat. Unless sound is a single point source (it's not due to reflections), you're going to have off-axis sound striking the ECM8000 and the mic's response will be different. So when you take that spatial average of sound striking the mic at all different angles, the curve you get is mic-dependent.

Quote:
That goes for pro audio, home audio, or car audio. So again...why? If you take that away, you are left with a omnidirectional mic and a binaural mic.
You cannot use identical measurement techniques in home and car audio. Car audio, again, has a sound field consisting of direct/early-reflected sound at similar amplitude. Home audio is direct with lower-amplitude early+late-reflected sound. Perceived sound flatness varies based on the direction at which is strikes your outer ear. This is why I don't think the home audio curves are applicable to car. It's the same reason why headphones do not have a flat frequency response (because otherwise they would sound terrible). They are diffuse-field corrected because just like in car audio, the sound comes from the sides and all around, not primarily from the front of the listener.

Quote:
If you use spatial averaging, neither will give you much difference in results. Ask Erin. Not to put him on the spot, be he bought binaurals and has gone back to using a single omni. From what I understand, it's because it's easier to use and when using spatial averaging, the results are NOT very different. If I'm wrong about that and there was a big difference, I'll eat my words and apologize.
I'd be interested i knowing why this person didn't prefer using binaurals. But my first question is, was he/she equalizing towards a curve that was specifically derived from binaural measurement to begin with? If not, I don't see how you can get good results.

Quote:
So, on to where to measure and how to measure. Well, I vote for measuring at the listening position.
Of course, where else would you measure from?

Quote:
Fortunately, because of the size of the listening space, nothing below the treble range changes much anyway (see image below). In fact, with a 5msec gated test vs an ungated one, I have no difference in FR from below 10khz. Granted, there is a 15db difference between the two at 20khz, but odds are the only speaker affected is the tweeter, so it isn't like trying both options and seeing what you prefer would affect any tuning beyond said tweeter.
If you're referring to the car cabin environment, then yes, this is known already that gating makes no difference because reflected sound arrives very shortly after the direct sound (i.e. a diffuse field)

Quote:
All of this brings me back to the fact that I, PERSONALLY, feel that measuring system response is the easy part. Getting to the target is the difficult part.
There are many harmful ways to EQ to a target curve. And a target curve doesn't capture all the problems with your system, like high-Q high amplitude peaks in the midbass...can't see that with 1/3 octave
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Default Re: Target Curve Comparison

See below:

Quote:
Originally Posted by smellygas View Post
Thank you for the thoughtful reply. My opinion is that +/-3dB at 1/3 oct smoothing, depending on where the peaks/valleys are, can sound okay to pretty bad. My personal goal is to get something close to what I can get from a reference home audio setup.

I agree that the +/-3db at 1/3 I mentioned can sound great to terrible. I find it pretty bold to say "okay" at best. Fact is, it is a good range to consider acceptable IMHO and many of the best sounding cars I've heard target it as such. That also doesn't mean there aren't problems that need to be fixed by using higher resolution or your ears. Spot treatments don't discredit a general +/-3db range of "acceptability".

Having done a lot of EQ for years, my experience is that much smaller corrections over smaller bandwidths can make BIG differences in sound quality. My perspective is that those curves are completely difference. Even a wide bandwidth boost/cut of +2dB over the treble can make a big difference in "brightness."

Again, you're right that a 2db change can make a difference. Hell, a .5db change can make a difference. Point is, I put up several different curves (yes, I agree they are different) that all have VERY similar trends. They are similar enough that if you chose the "average" response of them and accepted a +/-3db range, you could touch on almost all of them within the same tune. I didn't say that tune would sound good/great either, but I think it's worth noting since they LOOK to be very different when, in fact, they aren't.

Keep in mind that even mics we call "omnidirectional" are actually quite directional. Take the ubiquitous ECM8000. It's polar response is not flat. Unless sound is a single point source (it's not due to reflections), you're going to have off-axis sound striking the ECM8000 and the mic's response will be different. So when you take that spatial average of sound striking the mic at all different angles, the curve you get is mic-dependent.

I think you're clutching at straws here personally. I'm not saying that accuracy isn't important, and I certainly think you should have a calibrated mic, BUT to imply that using the ECM8000 is worthless because of polar response issues is a bit misleading too. Take 6, or more, measurements and average them and I promise it's going to paint a pretty good picture of what your system is doing. Again, I'm not trying to be a jerk with the "clutching straws" comment, but your posts seem to be awfully "doom and gloom" towards generally accepted methods of tuning while sharing very little on what you think is the proper way to measure. It just contributes very little and I feel that if somebody wants to challenge what is being shared here, having a valid response with support is required.

You cannot use identical measurement techniques in home and car audio. Car audio, again, has a sound field consisting of direct/early-reflected sound at similar amplitude. Home audio is direct with lower-amplitude early+late-reflected sound. Perceived sound flatness varies based on the direction at which is strikes your outer ear. This is why I don't think the home audio curves are applicable to car. It's the same reason why headphones do not have a flat frequency response (because otherwise they would sound terrible). They are diffuse-field corrected because just like in car audio, the sound comes from the sides and all around, not primarily from the front of the listener.

I don't really have anything to back up my disagreement here other than the fact that the curves above are similar. The "JBL Curve" comes from Andy W. and is recommended for cars. So is the "Crutchfield Curve". Neither are that different than the other "home curves" I've included. I understand you feel differently, but as it stands, you have not shared any suggestions and so I'll stick with what I've got in front of me.

I'd be interested i knowing why this person didn't prefer using binaurals. But my first question is, was he/she equalizing towards a curve that was specifically derived from binaural measurement to begin with? If not, I don't see how you can get good results.

They are a member here. In fact, they have already commented in this thread. If they feel like sharing more, they can. Anything beyond what I've already said would be purely speculation. All I do know is they had the means and have moved back to a single omni with spatial averaging.

Of course, where else would you measure from?

I'm not sure. I was thinking you might have implied we should measure right at the speaker to avoid reflections, which is not an accurate picture of the sounds that reach your ears.

If you're referring to the car cabin environment, then yes, this is known already that gating makes no difference because reflected sound arrives very shortly after the direct sound (i.e. a diffuse field)

Actually it does make a large difference in the treble (which I believe I just showed). What I'm saying is that you have no way of separating the reflections below that point and therefore they are included in the response. So you tune with them included. Now if you have an adjusted target response for the car, I'm all ears. Right now, you're still playing like you hold all the keys, but you're holding them all above our heads.

There are many harmful ways to EQ to a target curve. And a target curve doesn't capture all the problems with your system, like high-Q high amplitude peaks in the midbass...can't see that with 1/3 octave

You're right again, but I actually just shared how to look for modes (the high Q peaks you speak of) in another reply. It's funny how we both know the answers, but only one of us seems willing to help others by sharing them.
For now, I'm done with this thread. I simply started it to share some information I had recently acquired doing some searching of the web. I felt it was better than the typical "what midbass/sub should I use" threads that pop up daily. It seems that instead my sharing is being challenged by a person who knows a bunch and shares very little. The point of this forum, to me, is to share and dispel dogma...if it isn't happening...I'm not interested.

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Default Re: Target Curve Comparison

Quote:
Originally Posted by pionkej View Post
See below:



For now, I'm done with this thread. I simply started it to share some information I had recently acquired doing some searching of the web. I felt it was better than the typical "what midbass/sub should I use" threads that pop up daily. It seems that instead my sharing is being challenged by a person who knows a bunch and shares very little. The point of this forum, to me, is to share and dispel dogma...if it isn't happening...I'm not interested.
I was done with this thread when I received 2 personal attacks (deleted by a mod) when I simply requested that people not talk about their smartphone RTA's here.

I'm flattered that you think I know the answers. I don't. That's why I'm trying to ask questions that usually don't get asked in the bimonthly target curve thread. Obviously that's not acceptable. So never mind. Everyone appreciates your efforts in compiling the different target curves. Clearly, nobody appreciates me pointing out that the curves are not reproducible without duplicating or accounting for the way the target curve was measured.

And hey, maybe I'm completely wrong! But explain how I can measure my car's FR with an ECM8000 and with binaural mics and obtain completely different curves (and both are almost completely flat on-axis 20-20k). Even 2 different ECM8000's won't measure the same without calibration. But hey, never mind, let's just talk about the normal stuff we talk about in these threads. By all means.

There are people out there who've determined a "preferred" freq resp curve using a reference car stereo system and have generated a target curve using their measurement technique. For instance, any company with a DSP cabin response correction feature (like the MS-8, Alpine's Imprint, and the Audissey solution for car) knows...they just haven't published it AFAIK in JAES, and it remains somewhat proprietary. (Interesting, the Harman Group HAS published the "target curve" of home loudspeakers including their measurement technique). Andy has published his target curve for cars, but I'd be curious how to duplicate his results - i.e. if I EQ to that curve, what measurement equipment would I use? binaural mics, spatially averaged? Standard dummy head with binaural mics? Spatially averaged omnidirectional mic?

I obviously offended some people, and my contributions are not appreciated, so cya later. Perhaps someone who knows the answer can chime in so we can stop having these repetitive target curve threads.
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