The Pursuit of a SQ Standard in Car Audio.

[tspence73]

Hello,

I've been racking my brain for almost 2 years attempting to fathom what exactly sound quality 'is'. Try to find a definitive standard that truly 'sounds good'. So far I couldn't.

So, I decided to sit and think. Is there any place in audio that has a uniform/set standard for audio. There is!

For home theater audio, the only known set standard for audio quality is Lucas film's THX.

There are set standards to qualify an audio system for THX certification in studio production, amplifiers, sound processors, cables and speakers.

The whole purpose of THX certification is to provide a minimum set standard so that you can reproduce the same performance in your home as the engineers did in the studio during mixing and mastering the film sound.

I can't think of a more apt description of what 'sound quality' truly is. It's the very essence of 'realism'. The only TRUE measure of SQ must be a controlled set of parameters that starts:

1. In the studio with properly calibrated microphones & equipment.

2. Through the mixing and mastering stage with a properly calibrated audio system.

3. The media used to store the recording.

3. Then the certified playback equipment.

4. Finally the calibration of the playback equipment to match the way the original mixing and mastering system was calibrated.

THIS is the definition of sound quality and ironically, only in home theater will you find any such set standard.

Now, problem. I've looked into music recordings and found some disturbing information. There is no set standard in the studio for recording, mixing, mastering etc. This is precisely WHY you cannot build a system that sounds perfect on everything you play.

The solution. Knowing that there is no true standard for music recording, mixing, mastering etc. I began to think of methods for getting the best possible sound quality. The solution? You must rely on your own good judgement as to what 'real' sounds like. Only YOU can calibrate a system to sound real without a set standard to go on.

1. Find what you consider to be a 'perfect' recording. A track that has great tonal balance, dynamics, vocals, instrumentation, etc.

2. Then take a track that sounds 'wrong' and rip it to wav.

3. open the wav file in a program like sound forge

4. use the EQ and other sound processing in this program to try and match the character or 'timbre' of the really good sounding track.

5. compare them and if they have good similarity, you can play them back in your car and be assured that they are similar enough that you don't have to worry about adjusting settings to get the best sound quality.

I've found this works for me. It helps correct the main problems associated with the music industry's lack of symmetry. The only way to improve this problem is for the music recording industry to set strict standards like the movie industry does. I can honestly say that I can pop in any modern movie and I don't have to worry about adjusting sound levels or tonality at all. It's sounds perfectly comparable to other modern films from other studios. The movie industry has it RIGHT and the music industry needs to take a cue from them and create a modern studio recording standard across the industry.

So, for the equipment. What do you buy? What set standard do you use to select your gear?

I have created my own set standards to produce realism.

What do we know about 'real world' sound? Well, let's start with our ears. Our ears have limits. Both in frequency response AND in how much loudness we can safely stand. What is the human limit? Let's go out on google and find some info.

http://copublications.greenfacts.org/en/he...xes/table-1.htm

http://art110.wikispaces.com/Dynamics

http://www.statemaster.com/encyclopedia/Threshold-of-pain

It seems that the bulk of information indicates the threshold of pain is around 110db - 120db.

I went one step further and applied the fletcher-munson curve to this information:

The Threshold of hearing is frequency dependent, and typically shows a minimum (indicating the ear's maximum sensitivity) at frequencies between 1 kHz and 5 kHz. A typical ATH curve is pictured in Fig. 1. The absolute threshold of hearing represents the lowest curve amongst the set of equal-loudness contours, with the highest curve representing the threshold of pain. Sound pressure level (SPL) or sound level Lp is a logarithmic measure of the energy of a particular noise relative to a reference noise source. ... Sound pressure p (or acoustic pressure) is the measurement in pascals of the root mean square (RMS) pressure deviation (from atmospheric pressure) caused by a sound wave passing through a fixed point. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... Fig. ... The old Fletcher-Munson equal-loudness curves from 1933. ... In hearing, the Threshold of pain is the sound pressure or sound pressure level beyond which sound becomes unbearable for a human listener. ...

In my own personal test. I applied a 300Hz tone to my car system. I used a radio shack SPL meter to measure the SPL. I kept turning up the volume until I just couldn't stand it. At 110db SPL sustained for a few minutes, it was enough to leave me nautious and dizzy. With a lower frequency like 50Hz, I was able to easily stand up to 125db before having similar effects. I call that easily hitting the threshold of pain. So, the fletcher-munson curve seems a bit inaccurate to me according to the figure. I'm MUCH more sensitive at 300Hz than at 50Hz.

What I've come up with? People say SPL systems are not SQ. That may be true to a point, however, I submit to you that SPL is one such way to measure a system to assure proper clean output.

What the speaker manufacturer's have FAILED at in giving you true options in buying gear? A measurement of SPL capability vs distortion. This is truly going to allow you a gauge to figure out what your speaker can do and how far you can push it before it starts outputting junk. Another spec mysteriously missing from most speakers is 'power compression'. This is going to effect the 'dynamic range' capability of your speakers. Ever listen to a system with tiny drivers that seems to sound 'flat', with no 'punch' and sounds more lifeless the more you turn up the volume? That could be power compression at work, limiting the potential peak output of the speaker(s) when you apply more wattage to it's voice coil.

So, what are the goals in selecting your speakers?

1. Select a speaker that yields very low distortion at the threshold of pain for it's intended frequency range.

2. A sub woofer will require more SPL output to match this goal as your ears can tolerate FAR more SPL in the bass range than in the midrange.

Do you 'get it'? You don't have to have your midrange speakers able to produce the same maximum SPL as your subs, etc.

What is the loudest 'real world' music? Well, let's turn to classical. You would be shocked that during peaks in orchestras, a 'fortissmo' can reach up to around 110db! Wow. That's really loud for acoustic/natural music but it's true.

http://web3.unt.edu/news/story.cfm?story=7128

So, if we want to reproduce these 'real world' listening conditions, we will need to select the proper amplifiers and speakers to accomplish the job. My NEW definition of 'sound quality' is, "The maximum SPL that can be achieved up to the threshold of pain with the lowest power compression and lowest distortion. The lower the power compression and distortion at the theshold of pain (depends on the individual but 130db for bass and 110db for all other sounds works for me personally), the better the sound quality.".

So, this will fly in the face of the theory of a lot of people who think that low sensitivity speakers with modest power handling are somehow going to give you great sound qualiy. If your GOAL is to produce 'real world' sound levels, you better re-evaluate what speakers you are saying have good sound quality.

Amplifier selection must be made based on how much wattage it will take to drive your speakers to the SPL levels needed to reach the pain threshold. So, depending on your speaker sensitivity, your amplifier choices may vary across a spectrum of outputs.

So, I would say it's a good guess that most SPL lovers can produce this range effectively and at lower distortion than most SQ-based car systems.

But what separates a blunt SPL car from an SQ car if the output levels are both 'loud'? Tuning, of course. You will be out to achieve proper balance and tonality, but not super-g-force bass. Most SPL competition installs greatly exceed pain thresholds, which would be a rather big waste in an SQ install. The goal is to merely have the ability to reach the threshold of pain, but it's also to reach that with the lowest distortion possible.

[EXOcontralto]

THX is outside car audio - And it simply means the separation of audio and video into two parts on one reel -

It means nothing more than unitary sections of data that play simutaneously -

THX is seen nowhere, but in movies, and theater reels. It means nothing to us Car Audio guys.

[a_steezy]

THX is outside car audio - And it simply means the separation of audio and video into two parts on one reel -

It means nothing more than unitary sections of data that play simutaneously -

THX is seen nowhere, but in movies, and theater reels. It means nothing to us Car Audio guys.

what exo said ^^^

BASS HEADS UNITE!

[littleitaly1990]

THX is outside car audio - And it simply means the separation of audio and video into two parts on one reel -

It means nothing more than unitary sections of data that play simutaneously -

THX is seen nowhere, but in movies, and theater reels. It means nothing to us Car Audio guys.

What he is saying is there is a standard that all products carrying the THX badge must meet. If audio followed this standard, there wouldn't be as much deviation from one song or piece of equipment to the next, so tuning would be far easier as you would only have to tune once for it to sound good for all music. Excellent post.

[SQMonte]

I agree with the fact that there should be standards...I can put in a cd that sounds sick, very clear, very loud, very precise, and then put in another cd where the bass us muddy, vocals are too low, overall volume noticeably lower, that irks the shit outta me. And it's even more prevalent with MP3's and other various audio file types, one set standard would eliminate that as they would all have to be mastered and recorded to the same specs.

[Neel]

It is extremely difficult to achieve a perfect listening environment in a car, IASCA has set some standards as to what a car should sound like (not saying that IASCA = SQ) and it is very rare to see someone put in the effort to build a car that actually sounds very good. Every car is shaped differently and made of different materials that reflect / absorb sound differently. Even driver placement is such a pain in car stereo, even with the drivers in the kickpanels , we still have to use signal delay to compensate. In a home theater all the drivers can placed exactly how you want them. Enclosures? HT speakers come in perfect enclosures!! While in car stereo we have to slave for months finding the perfect location and then building a strong enclosure that does not resonate ( and still manage to get it to fit in the car without taking up a ton of room and still being able to aim it correctly). Home theaters almost have low / no noise floor to worry about...people spend months trying to chase noise out of car stereo systems. It is also very hard to find 12v components that are actually good...

Notice how one of the most successful IASCA competitors used primarily home theater components in his car.

http://www.milbert.com/autos/earl

Why havent you posted this on DIYMA?

[tspence73]

It is extremely difficult to achieve a perfect listening environment in a car, IASCA has set some standards as to what a car should sound like (not saying that IASCA = SQ) and it is very rare to see someone put in the effort to build a car that actually sounds very good. Every car is shaped differently and made of different materials that reflect / absorb sound differently. Even driver placement is such a pain in car stereo, even with the drivers in the kickpanels , we still have to use signal delay to compensate. In a home theater all the drivers can placed exactly how you want them. Enclosures? HT speakers come in perfect enclosures!! While in car stereo we have to slave for months finding the perfect location and then building a strong enclosure that does not resonate ( and still manage to get it to fit in the car without taking up a ton of room and still being able to aim it correctly). Home theaters almost have low / no noise floor to worry about...people spend months trying to chase noise out of car stereo systems. It is also very hard to find 12v components that are actually good...

Notice how one of the most successful IASCA competitors used primarily home theater components in his car.

http://www.milbert.com/autos/earl

Why havent you posted this on DIYMA?

I got banned on DIYMA. Don't ask. I'm just moving on from that place.

Anyway, here is a thread on caraudio.com about my system:

http://www.caraudio.com/forum/showthread.php?t=434614

I just sent my Planet Audio BB175.4B 4-channel amp to ZED Audio and Stephen Mantz himself is going to personally modify & test the amplifier for me as well as add LED clipping indicators to it.

[HHR Ed]

SQ is so subjective to the listener, even in THX standards.

And especially in cars does the install and build matter more than the equipment being used.

Simply put, its impossible to standardize SQ.

Can I tell you that something is beautiful because standards say it is so?

What you think is beautiful may not meet those standards and therefore it is not really beautiful?

[Nirvalica]

I would say sound quality of a speaker is the difference or dynamic range between the quietest and loudest sound it can create at one moment.

Edit: as well as keeping it all accurate, of course.

[littleitaly1990]

SQ is so subjective to the listener, even in THX standards.

And especially in cars does the install and build matter more than the equipment being used.

Simply put, its impossible to standardize SQ.

Can I tell you that something is beautiful because standards say it is so?

What you think is beautiful may not meet those standards and therefore it is not really beautiful?

This is very true, sound quality is 100% in the ears of the beholder. However, the standard that TXH makes is more of an equipment standard...So if all songs were recorded with bass at +28db or whatever, it would be far easier for use to tune our system to a place that sounds good for more songs...