Update: Chris Lewis... And His Decibel Chart Article Inside

[quakecitystudio]

Do you guys remember Chris Lewis when he worked for AutoSound and Security. He had an article that stated how one could calculate his or her estimated SPL based on amp wattage and woofer output at 1w/m. It was an estimation because vehicular modifications or box setups would make it more complex. I remember trying to email him, to let him know that his chart was a bit flawed, but he never responded back. It was as if he disapperaed off of the face of the planet. I still have the article:

For those of you that are not sure of the article it is called "The SPL Channel" in Auto Sound & Security/ August 1997. "PART TWO: How I spent my Summer Vacation Blowing Stuff Up."

From the article:

Edited June 16, 2008 by quakecitystudio

[Boon]

Do you guys remember Chris Lewis when he worked for AutoSound and Security. He had an article that stated how one could calculate his or her estimated SPL based on amp wattage and woofer output at 1w/m. It was an estimation because vehicular modifications or box setups would make it more complex. I remember trying to email him, to let him know that his chart was a bit flawed, but he never responded back. It was as if he disapperaed off of the face of the planet. I still have the article, with my version of the charts...

A wild, wild, wild, completely infeasible estimation?

8" Sub we tested

500wrms

In a van, 2 4" aeroports = 133dB

In a tiny Ford Hatch, 1 4" aeroport, bit of box tweaking = 142dB

Of course it was flawed, he probably didn't email back because he got 10000 other emails about it being flawed.

[tommyk90]

Those charts are completely worthless.

Most people can't get a 140 out of a type-r 10, I got my truck up to a 151.

All of your threads suck.

Edited June 14, 2008 by tommyk90

[quakecitystudio]

All of your threads suck.

Why make such a comment like that? Do you see me harassing you about your threads? No, so let it go.

Edited June 16, 2008 by quakecitystudio

[quakecitystudio]

We must understand that his calculations are based on the 1w/m outside of the vehicle, with all other variables constant. The only considerations being the woorfer, and the wattage, and an efficiency constant of 116.6.

Now, here's where I have questions:

Where did he get 116.6 db and how is it a measurement of efficiency?

Also, how did he determine the dbs of each ratio number? There is no standard formula, like saying since 1:1 is 0 and 2:1 is twice as 1:1 then 2:1 will = 3 and since 4:1 is 2x2 then 4:1= 6dbs meaning twice the output= 3+ dbs. But, after that it's off the map...

Here's what I did on his chart: a comparison of ratio to ratio:(middle numbers are the difference between ratios)

1:1 = 0

3

2:1 = 3

1.7

3:1 = 4.7

1.3

4:1 = 6

1

5:1 = 7

.8

6:1 = 7.8

2.5

7:1 = 8.5

.5

8:1 = 9

.5

9:1 = 9.5

.5

10:1 = 10

There isn't a pattern, and the only thing that stands is that 4:1 is twice more than 2:1, but no value for 1:1 since 2:1 is twice more than 1:1.

[quakecitystudio]

Here is my version:

1:1 = 1.125

2:1 = 2.25

3:1 = 3.375

4:1 = 4.5

5:1 = 5.625

6:1 = 6.750

7:1 = 7.875

8:1 = 9

9:1 = 10.125

10:1 = 11.25

or if 1:1 must equal zero:

1:1 = 0

2:1 = 3

3:1 = 4.5

4:1 = 6

5:1 = 7.5

6:1 = 9

7:1 = 10.5

8:1 = 12

9:1 = 13.5

10:1 = 15

[quakecitystudio]

As an example We will use Chicken's caddy: actual 160 db on termlab (and door open)

16,000 w on the subs (2,000/sub)

18" BTL 93.7 db 1w/m

*Now this calculation is outside the vehicle at 1w/m*

The spl of one woofer at 2000 w:

woofer's efficiency + wattage given to woofer = spl of one woofer

93.7 + 33 (Based on Chris Lewis Scale) = 126.7 db for one woofer at 1m or 39.37 inches from mic.

SPL of given wattage if sound system was efficient at 1 meter:

16,000 w = (2)((10)(10)(10) = Chris's table = 3+9+10+10+10=42

42+116.6(efficiency standard)= 158.6 db at 1w/m

So you can see that Chris's numbers are pretty close.

[tommyk90]

Why make such a comment like that? Do you see me harassing you about your threads? No, so let it go.

I'm a jerk.

And, if you can't take a hint, nobody gives a damn about these numbers. The severe lack of replies should tell you that.

In all seriousness, there's no reason to even bother wasting time trying to figure out some mathematical formula.

For some cars it may be close, and for others it could be drastically off. That's all part of the SPL game. Instead of trying to figure out equations you should spend time building and testing to see what works and what doesn't.

Edited June 17, 2008 by tommyk90

[Boon]

That whole article just smacked of failure to me. The sheer difference you can get in dB by changing pathetic little things means any mathematic modelling of a system is fairly meaningless.

For SPL it is only real world testing that matters.

His statement that concrete and lexan are pointless seems woefully ignorant. Go tell Alan Dante that.

Also tell me how Dante does 180.1 with 'only' 28000w to a single 18" woofer

28000w = 10x2800 = 10x10x280 = 10x10x10x28 = 10x10x10x2x14 = 10x10x10x2x2x7

So chart numbers:

Chris: 10 + 10 + 10 + 3 + 3 + 8.5 = 44.5

44.5 + 116.6 = 161.1 = Failure

Your numbers:

11.25 + 11.25 + 11.25 + 2.25 + 2.25 + 7.875 = 46.125

46.126 + 116.6 = 162.725 = Failure

Have you ever actually done an SPL build? You would probably know little things like 'maths never equals real world' and that totally seperating the rear wave (usually) does NOT make a car loud - as well as amazing facts like simple cars = loud cars, take one look at the Euro street scores and that would become very apparent.

[Big P]

I'm a jerk.

And, if you can't take a hint, nobody gives a damn about these numbers. The severe lack of replies should tell you that.

In all seriousness, there's no reason to even bother wasting time trying to figure out some mathematical formula.

For some cars it may be close, and for others it could be drastically off. That's all part of the SPL game. Instead of trying to figure out equations you should spend time building and testing to see what works and what doesn't.

Why are you being such a dick? Its really uncalled for.