posted
ok see if yall can understand me on this one.... spl meters are suposed to all measure the same thing right? why do thier numbers deviate so much from one another.....one company says use a sensor....anothercompany says no a mic with metal in it....and another company says no a mike with plastic in it.....can you actually get an accurate spl reading and which one is that.....i mean a db is a db an inch is an inch....you dont see "foot long rules"(meaning 12 inches) get the inches stretched to where its really like 16 inches i mean.......wtf..... sorry for the no punctuation this just kinda irritates me....
-------------------- Jon Elia 2-12w3v2's 1-jbl 1200.1 hope to change the subs soon
member: Team Gates
quote:Originally posted by HORNETS NEST : MAn, we're worldwide man,
DIrTy SoUtH DEAF SQuAD Posts: 257 | From: longview texas | Registered: Mar 2004
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posted
Db is actually just showing an increase in power from one thing to another. If you calibrate a microphone on monday and the static atmospheric pressure changes you start the day out with a DB reading due to the change in pressure already. the new sensor is more consistant because it is ot affected by environmental conditions.
-------------------- Just some thoughts from a nobody. Posts: 3598 | From: Lakewood,Ohio | Registered: Aug 2003
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posted
ok but i'm talking same day same conditions thing...if they are all made to show the same thing....you can get three meters....just say audiocontrol termlab and the old termlab.....they all will have different spl levels if you run them in the same car at the same time....arent they suposed to measure the same thing?
-------------------- Jon Elia 2-12w3v2's 1-jbl 1200.1 hope to change the subs soon
member: Team Gates
quote:Originally posted by HORNETS NEST : MAn, we're worldwide man,
DIrTy SoUtH DEAF SQuAD Posts: 257 | From: longview texas | Registered: Mar 2004
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posted
I remember the liner x mics were different then the termlab ones. Who knows some mics are just differnt... you have to factor in a margin of error. LIke you said even when measuring an inch with the most precise instrument there will still be some margin of error because nothing is perfect.
-------------------- _ _______________________________________ _ 2005 Chrysler 300 Touring 1997 Dodge Ram SS/T 1969 Oldsmobile Delta 88 Royale Posts: 189 | From: Western MA | Registered: Aug 2001
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quote:Originally posted by elia151: ok but i'm talking same day same conditions thing...if they are all made to show the same thing....you can get three meters....just say audiocontrol termlab and the old termlab.....they all will have different spl levels if you run them in the same car at the same time....arent they suposed to measure the same thing?
The conditions change all day long which you might not notice but could eat a few tenths here and there. This is why they used to calibrate the mics before and after a run at finals in the past. The microphones that are used in ac and old t/l setups are underwater hydrophones. The can handle high SPL but don't really like high SIL. The diaphrams can and do strech and become non-linear after a really loud car goes through the lanes.
-------------------- Just some thoughts from a nobody. Posts: 3598 | From: Lakewood,Ohio | Registered: Aug 2003
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quote:Originally posted by ShadowStar: There is a generally accepted 0db point of 1e-12 watts per square meter: Most or all SPL meters should be pretty much atmosphere invariant.
ShadowStar
How can they be atmosphere invariant? They have to have a base pressure to start with,then they need to know the compressibility of the medium, then they can try to convert pressure into an electrical impulse. After you convert and measure the electrical impulse then you can is the log to figure out the power factor of the equation. All the calculations rely on an accurate measurement of the static and dynamic pressures on the microphone/sensor. The SIL can greatly influnce the outcome of the equation as well as any waveform which is clipped or squared in any way.
-------------------- Just some thoughts from a nobody. Posts: 3598 | From: Lakewood,Ohio | Registered: Aug 2003
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posted
I find this topic really interesting because when I got into car audio back in 1997 the frequently calibrated Audio Control at the local shop was the reference god. I worked for years to break 150. Remember I'm are talkin about before Class D was readily available I was working with Rockford, Precision Power, Soundstream Reference.... Class A/B amps. This was before I learned of ported enclosure gains and walk in port one note wonder setups. I was workin with the good old school stuff (ermm real amps ). SO when I finally broke 150 with MMATS D300HC's and Digital 9515 wall on the Audio Control, thats a 150 to me, period. I don't care if some new meter tells me I am hitting the same with my wall as I used to on the AC with two JL 12's and a PPI amp. I will still call that degree of loudness (which most audio nuts should know) that distinct zone when the air gets watery that you pass 147-151 mark, I will call that 150! So even though at a show say I land a 140 something, thats not a 140 something to me in reality to me its a 150 I guess you could argue that a standard is a standard, I guess it all goes by what you prefer or if you just want to be straight up and accept new standards in equipment. Now I'm into home audio so i guess my opinion doesnt count Posts: 841 | From: Pennsylvania | Registered: Feb 2002
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How can they be atmosphere invariant? They have to have a base pressure to start with,then they need to know the compressibility of the medium, then they can try to convert pressure into an electrical impulse. After you convert and measure the electrical impulse then you can is the log to figure out the power factor of the equation. All the calculations rely on an accurate measurement of the static and dynamic pressures on the microphone/sensor. The SIL can greatly influnce the outcome of the equation as well as any waveform which is clipped or squared in any way. [/QB][/QUOTE]
Umm.. We're comparing apples to apples here. Microphone A operating in the same enviroment as Microphone B, if both are referenced to the standard of 0db (or a vacuum chamber or whatever,) should function similarly, no? The problem is when Mic A doesn't read the same as Mic B for the same situation, right?
ShadowStar
-------------------- You can't build a reputation for what you're GOING to do.. But you can build one for TALKING about it!
It's all about knowledge, love and respect. Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
I see what you're saying, (put both mic's in one car during one run), and they should both read within a tenth of each other... or something.
By comparison, hold your wristwatch next to the Naval Atomic clock and see what the variance is.
Now, are you willing to believe the atomic clock is more accurate then your watch because it (the atomic clock) uses a "more accurate" method/media?
Hence, TL is the new king of accurate measurment for spl...
-------------------- Get loud daily... not burping. From Finals 2005:
quote: It's World Finals. A certified event. A 4x scoring event. It's the "pinnacle" of the "sport".
If I showed up to Game 7 of the World Series and was found to have a Corked Bat in pre game warm-ups, what would happen to me? Even if I said that I 'didnt see it in the rulebook, my bad'.
From Finals 2004:
quote:Originally posted by dBSteve: Everybody in the top 8 in every class bent the rules.
posted
what it boils down to is this... All and I do mean ALL electronics will vary from unit to unit. A little less solder here on one, a little less silicon in a xsister on another. Throwing in diff manf or types of sensors will even throw that equation out further. Generally speaking same models of same manf should read reasonably close if they are in calibration.
I repair cellphones and can have two brand new ones from diff manf that will have very diff signal strengths, side by side. Even two of the same manf will show diff's somethimes.
Posts: 8 | From: Atlanta | Registered: Aug 2004
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quote:Originally posted by jnealg: what it boils down to is this... All and I do mean ALL electronics will vary from unit to unit. A little less solder here on one, a little less silicon in a xsister on another. Throwing in diff manf or types of sensors will even throw that equation out further. Generally speaking same models of same manf should read reasonably close if they are in calibration.
The problem with this argument is that we are speaking of calibrated measuring instruments. Given a calibration factor ( a vacuum, a particular amount of energy, some noise, whatever,) these devices to within specifications should read the same thing.
Thats like saying, if you use two rulers to measure an object, well, because wood cells expand and contract differently and all marking/inking schemes are slightly different, I could reasonably get 11 inches on one ruler and 11 1/4 on another ruler.
But, of course, we're talking about really expensive rulers here aren't we?
ShadowStar
-------------------- You can't build a reputation for what you're GOING to do.. But you can build one for TALKING about it!
It's all about knowledge, love and respect. Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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quote:Originally posted by SPL Neon: I find this topic really interesting because when I got into car audio back in 1997 the frequently calibrated Audio Control at the local shop was the reference god. I worked for years to break 150. Remember I'm are talkin about before Class D was readily available I was working with Rockford, Precision Power, Soundstream Reference.... Class A/B amps. This was before I learned of ported enclosure gains and walk in port one note wonder setups. I was workin with the good old school stuff (ermm real amps ). SO when I finally broke 150 with MMATS D300HC's and Digital 9515 wall on the Audio Control, thats a 150 to me, period. I don't care if some new meter tells me I am hitting the same with my wall as I used to on the AC with two JL 12's and a PPI amp. I will still call that degree of loudness (which most audio nuts should know) that distinct zone when the air gets watery that you pass 147-151 mark, I will call that 150! So even though at a show say I land a 140 something, thats not a 140 something to me in reality to me its a 150 I guess you could argue that a standard is a standard, I guess it all goes by what you prefer or if you just want to be straight up and accept new standards in equipment. Now I'm into home audio so i guess my opinion doesnt count
You really really shouldn't trust the AC calibrated or not. I've done enough personal testing on my own TermLab sensor and our teams Classic TL to know with certainty that hydrophone meters (new AC/old AC/old TL/linear X)tend to vary wildly with minimal to no changes. I do not know why this is, but it is so....
If you make no changes your score will ALWAYS be the same on the TL sensor. The same cannot be said for the AC. I'd be willing to bet that you got into the 150s several times but didnt know due to the AC's wild variances...
-------------------- 2005 Florida Street C Champion 2004 SBN Street C Champion 2004 SBN IDBL No Wall Champion 2003 NOPI Nats Street B Champion
posted
Doesnt it have something to do with that dB is a measurement of a "multiple" of difference? And not a physical ammout of anything? ...Like that 24dB is not double 12dB... its really 16X more!
for example, 1 inch is a objective measurement. It is derived in the most precise instruments from how far light travels over time, which does not vary.
DB is funny in that it only measures "doublings" in power, and has no real "zero" or more importantly a "one" mark. Cause you cant base a multiple on zero, you need something (5x0=0, 47x0=0, 2.4368x0=0, BUT 5x2=10!)
If I remember right, 1dB is commonly the least ammount of sound perceptable by the human ear. Then you base your multiple on that. It all depends on what "ear" you start from tho... its not a real quantifible thing
Posts: 45 | From: Richmond, VA | Registered: Apr 2004
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posted
as I understand it the new TL setup takes an averge of 3 frequencies centered around your peak. This will give a lower score but is more accurate because environmental factors are less of a variable.
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