Using an SPL Meter to adjust audio

[D'Ecosse]

This is an age old debate for anyone who's been in car audio. Tune for flat or tune for fun? Anyone remember R.A.C.? These debates never get anywhere. I hear very similar debates about steaks and whether or not you can eat a steak with a sauce. Diehards say no, rebel culinaries say yes. I'm of the belief you do whatever you like in every facet of life and no one but yourself should decide what tastes you should have...

& I especially agree with this!!
Each to his own - that's all that's important.

 

[Hugh]

Do you guys dip your stone crab claws in honey mustard sauce or hot melted butter? :smile:

 

[djdrock]

600 pages.. just enough to freighten everyone away for good John... :biggrin:

Notice we haven't heard from djdrock in a while... maybe he is out tuning... lol...

He wisely unsubscribed from this silly thread, set his sliders to his liking and is out enjoying his car and his sound system.

I'm baaaaaaack!

All of the above means squat. What matters is the final sound to the end user. Once again, I repeat that the human ear is not nearly as sensitive as electronic measuring devices. If you really want to eq the system for the car's owner, first you should plot a frequency response curve for his particular hearing capabilities.

Botttom line, play with the tone controls until it sounds good to you. Anything else is a complete and utter waste of time.

Everyone has their own opinion. And I certainly agree with Hugh, to an extent. Getting into audio techno-babble reminds a bit of a salesman I know at a high-end A/V store. I was listening to some Focal speakers in the studio, and I had brought in a few CDs of mine to listen to them. I kept saying everythings sounds bland/almost mono. He insisted that everythings was setup correctly. This is coming from a guy who claims to have "golden ears", and swears that by placing pennies on the corners of shelf speakers, you get better imaging/sound. So, I play a track that has very definite left/right panning, and would you believe it, the amp was not setup correctly, and it was playing everything in mono. Golden ears could not even detect this. My point...audio theory and everything that comes with it can go way off the deep-end. However, I am absolutely certain that my system can be improved upon, because I was able to find the "right" sound in my MR2. I have not fiddled with the crossover points on the amp much, thinking that the settings on it should probably match the settings on the similar amp in my MR2. Eventually, I will get to this.

 

[hofffam]

I agree that ultimately what matters is what sounds good to you.

The question is how to get there. I think turbo and others (like me) think it is better to start with a test CD and sound level meter. You have a better chance of starting from a reasonable tuning position. It is not an utter waste of time. Tweak by ear from there. Not from a blank slate.

BTW - I have a hard time taking serious audio advice from someone with Iron Maiden in their name. Maybe to listen to Iron Maiden correctly you need to just push all the EQ sliders to the top. That will push a nice ripple in the response from top to bottom and add noise.

 

[Hugh]

BTW - I have a hard time taking serious audio advice from someone with Iron Maiden in their name. Maybe to listen to Iron Maiden correctly you need to just push all the EQ sliders to the top. That will push a nice ripple in the response from top to bottom and add noise.

You've obviously never listened to Maiden.:smile:

Go get their latest album "A Matter Of Life And Death" and take a listen. If you don't like you can send it to me and I'll reimburse you for it. I have a lot of friends who'd love to have it.

P.S. I have over 2000 CDs in my collection ranging from classical to jazz to rock to metal and everything in between. I'm very musically literate. Go grab a copy of "Once" by Nightwish while you're at it. Tarja's vocals will be a great test for the sibilance in your system and the music is incredible.

Happy listening and Happy Holidays!

 

[Ski_Banker]

CL65captain said it but I will break it down and make it even simpler. A perfect human ear hears from 20Hz to 20,000 Hz. 1 Hz is one "cycle" of sound per second. One full wave going up and down. 20 Hz is the lowest bass frequency you can hear, and 20,000 Hz (or 20KHz) is the highest high. Most people's hearing however is much more limited than that.

An ideal stereo, would be capable of producing all these frequencies, all these sound waves, equaly. It would not exagerrate any particular part too much, or take any particular part AWAY too much. If you have no subwoofer for example, you probably won't get a lot of response from the system below 100 Hz. If you have no tweeter, you won't get much in the 10Khz area.

When you install a stereo system, you have to make sure that the tweeters, mids, woofers, subwoofers, all do their part right, and that their interaction with the "room", in this case the NSX cabin, produces a resonable response. When we talk about a "flat" response, all we are saying is that the frequencies are all produced equaly, at the same level (same loudness).

An SPL meter (Sound Pressure Level), just measures how loud a sound is. Thats all. The test disc, gives you tones... centered around frequencies such as 20 Hz for example, the next track a bit higher at 30Hz (a bit higher bass), and so on... all the way up. You simply sit in the cabin, and measure so that you know where a sound is louder, and where it is quieter. An increase in 3db (decibels) is roughly equivalent to a doubling of volume. So if you meausure and at 100Hz you have 90 dB, and everywhere else you are at 85 dB, you clearly have a "peak" at 100 Hz. It is too "loud" at around 100 Hz. And so you use the equalizer settings to lower the bass at 100Hz enough to bring it in-line with other frequencies.

Tuning a system is almost impossible by ear where there are a lot of problem areas, if you are not starting with a fairly clean sheet, a system with a fairly flat response. It is, like CL65captain said, very difficult to guess that you have a huge peak or dip at 5KHz, without measuring. All you know is something is not right. So instead of cutting at 5Khz, you may inadvertantly boost what is around it... at 7.5Khz, etc.

My advice for system tuning, is to just measure the response in your cabin. With a cheap SPL meter from Radio Shack (that I will state again is fairly accurate, especially for our use here), and a test disc like the stereophile (stereophile is a magazine) one to see what is going on. Once you have that info, there are plenty of experienced people on this forum that can look at the list of equipment, their placement and settings, and make suggestions as to what to do. If there is any area that a novice may screw it up, it is in this tuning area.

This is similar to for example sticking an wideband 02 sensor on your car, getting A/F ratios, plotting them, and then telling someone like Dynomike or the FactorX guys what you are getting. They can then help get the tuning right, and that is much better than sitting in your car with a laptop and "guessing" about how to set your A/F parameters.

This is a very general post and I know there are technical aspects that can be argued, I am refraining from doing so as I hope the more technical people here do as well.

I hope this was simple enough to understand.

Yep, thanks. Makes sense. Still seems like an exercise in saving time, by using the SPL results to benchmark, but I can see how it could take hours to listen to different music types and fiddle with an equalizer to perfection.

BTW, wouldn't you need to do the testing in a driving car to account for exhaust and road noise? And wouldn't that be a moving target since speed and RPMs are always different?

 

[hofffam]

You've obviously never listened to Maiden.:smile:

Go get their latest album "A Matter Of Life And Death" and take a listen. If you don't like you can send it to me and I'll reimburse you for it. I have a lot of friends who'd love to have it.

P.S. I have over 2000 CDs in my collection ranging from classical to jazz to rock to metal and everything in between. I'm very musically literate. Go grab a copy of "Once" by Nightwish while you're at it. Tarja's vocals will be a great test for the sibilance in your system and the music is incredible.

Happy listening and Happy Holidays!

Hey - sorry for the smack about Iron Maiden.

If that's what you like......:smile:

Have a great holiday!

 

[TURBO2GO]

BTW, wouldn't you need to do the testing in a driving car to account for exhaust and road noise? And wouldn't that be a moving target since speed and RPMs are always different?

No. The sound of the exhaust and the engine are noises that are on top of what the sound system is producing. If our goal was to create a silent space and only music within that space, then yes you would have to account for engine and exhaust noise and EQ them out. But our goal is to have a stereo system produce the music being played through it accurately. What you want in that scenario, is to be in as silent a space as possible when tuning.

Another example... you and I can listen to a good stereo system and talk at the same time. Our voice will not make the music sound bad or inaccurate. Its just the sound of our voice superimposed on top of the music. The engine or the exhaust have their own distinct sound recognized by the brain as "engine" and "exhaust". That is not the equivalent of a resonance frequency at 120Hz produced by the interaction of the subwoofer and the NSX cabin.

Do I make sense?

On human hearing that Hugh insists on going back to, most humans hear very similarly. The variation or "sensitivity" that he is talking about, presents itself at the extreme ends of the audio spectrum, the low or high end, usually the high end. It is not a graph full of peaks and valleys as he is suggesting that you would have to "plot" for first before you adjust the stereo.

Furthermore, we are not tuning for Margaret's or Fred's ear. What we are measuring, is the interaction of the system and the "room" the system is in, in this case the NSX cabin. Any good installer, audio, acoustics or recording engineer will tell you how important measurement is. Hugh, just like always, has his own opinions.

 

[dcrandon]

For God's sake, just use the EQ sliders, the head unit's settings, and your ears to acheive a sound that you like. Who gives a flying fuck what the laptop thinks? You are making a huge mountain out of a molehill.

More importantly make sure your crossover points and rolloffs are correctly set either on the head unit or amplifier side before you do the final adjustments with your ears and fingers

No offense intended Hugh, but this is bad advice. You don't spend hundreds or thousands of bucks and then do this.

I've been an audiophile for over 30 years. Knowing what good sound is like is something that has to be learned. Your ears and brain need to be trained. What the average person thinks "sounds good" is usually nowhere near as good as it can get.

An analogy would be an 18 year old kid who buys and NSX and then brings it to the track and thinks he can become a good driver in a day by just "driving". Doesn't work like that. He needs to learn how to drive first. And the most effective way is someone teaching you.

The advice Turbo2go is giving him is spot on.

 

[dcrandon]

I know I'm coming into this really late, but...

Quote from Hugh:

"The human ear is not a very accurate instrument for "measuring" or listening to sounds."

You're talking in circles dude; why are you telling him to adjust by ear and then you say the above?

What you say about each individuals ear and brain having different freq responses is very, very true. However, because the brain compensates for the changes as one ages, what a person "hears" doesn't change much unless the loss is profound.

 

[dcrandon]

An increase in 3db (decibels) is roughly equivalent to a doubling of volume.

Turbo, your advice is excellent thoughout this whole thread. However, just a little correction here...A 3dB increase is a doubling of power, a 6dB increase is a doubling of voltage, but a doubling of volume (like when listening) is a 10dB increase.

David

 

[Zennsx]

Turbo, your advice is excellent thoughout this whole thread. However, just a little correction here...A 3dB increase is a doubling of power, a 6dB increase is a doubling of voltage, but a doubling of volume (like when listening) is a 10dB increase.

David

This is 100% correct.

 

[TURBO2GO]

Turbo, your advice is excellent thoughout this whole thread. However, just a little correction here...A 3dB increase is a doubling of power, a 6dB increase is a doubling of voltage, but a doubling of volume (like when listening) is a 10dB increase.

David

yes you're right... I knew that, I was just having a brain fart.

Hugh is in his own world man... he loves to argue about almost anything, and will no waaaaay give up. I usually give up way before that crossdresser does. :biggrin: