calculator

[kingjames]

Here is a neat calculator and this place has some decent articles on sound.

http://www.crownaudio.com/apps_htm/designtools/elect-pwr-req.htm

[SEAWOLF97]

it says to get 100db at 15 feet, I need 995 watts...hmmmmm, something wrong here ?

sens=87 according to manuf web site. and it also says I need 100-200 watts

[kingjames]

I said it was a neat calculator I never said it was accurate .:p

[Hoerninger]

...hmmmmm, something wrong here ?


Not quite shure, but 87 dB /W /m is a low efficiency speaker, and the calculator gives results for outdoor usage not within a room.
____________
Peter

[Andyoz]

Yes, it is only calculating for "free-field" conditions, i.e. outside.

When placing speakers indoors, the sound level at the listener is a summation of the "direct" and "reverberant" components. That formula is only calculating the "direct" component which decreases at 6dB for each doubling of distance.

It actually shows how important the "reverberant" component is when listening indoors, and this becomes even more important the further you are from the speakers (also shows how easy it is to blow-up gear when used outdoors!!)

That's why the room is one of the most important parts of your sound system :(

[Hofmannhp]

and the directivity of the speakers isn't considered....which makes a lot

HP

[Rusnzha]

Originally posted by seawolf



it says to get 100db at 15 feet, I need 995 watts...hmmmmm, something wrong here ?



Sound more reasonable for 15 meters? I don't think this thing works in feet.

[Hoerninger]

I don't think this thing works in feet.

Seawolf did it correct I suppose, inclusive conversion.
87 db/W /m is damn low.
____________
Peter

[clmrt]

If I ever get my E-V's back, I'll need a whole 2 watts.

How depressing.

[Andyoz]

The things calculating it correctly, a quick check with a calculator will show that.

100dB is a bloody loud level guys! It's hard enough to get that from domestic speakers (~87 dB/W/m) indoors let alone outdoors...

[clmrt]

http://www.myhometheater.homestead.com/splcalculator.html

According to this one, 995w gets you 109.5db @ 15 feet.

http://www.jblpro.com/pub/manuals/pssdm_1.pdf

[Andyoz]

That one includes +3dB for two sources, +3dB for room gain, and doesn't have the +3dB amp headroom allowance that the Crown calc has.

[rs237]

hello,

both calculators bring the same result:

http://img224.imageshack.us/img224/838/db1lx4.png

http://img224.imageshack.us/img224/8417/db2ul3.jpg

3.8 dB difference =
3 dB Headroom of the Calculator 1
0,8db = a difference between 15 Feet and 5 m

regards

juergen

[SEAWOLF97]

The things calculating it correctly, a quick check with a calculator will show that.

100dB is a bloody loud level guys! It's hard enough to get that from domestic speakers (~87 dB/W/m) indoors let alone outdoors...


Threshold of Hearing 10-12
Rustling Leaves10-11
Whisper 10-10
Busy Street Traffic 107
Vacuum Cleaner 108
Large Orchestra 109.8
Military Jet Takeoff 140
Instant Perforation of Eardrum 160

Near total silence - 0 dB
A whisper - 15 dB
Normal conversation - 60 dB
A lawnmower - 90 dB
A car horn - 110 dB
A rock concert or a jet engine - 120 dB
A gunshot or firecracker - 140 dB

[Baron030]

Ok, with all this talk about SPL calculators.
It has gotten me curious about what my new DIY project would sound like at full power.
Using the http://www.myhometheater.homestead.com/splcalculator.html calculator, with the speakers in the corners of the room and a 10ft. listening distance. I get the following:

2-2405s @ 40watts/channel = 120.3db in the 8 KHz to 20 KHz range.
2-2446/2382s @ 110watts/channel = 129.7db in the 1.2 KHz to 8 KHz range.
2-2012s @ 350 watts/channel = 124.8db in the 400Hz to 1.2 KHz range.
2-2226s @ 500 watts/channel = 123.3db in the 20Hz to 400Hz range.

Gee, I guess this explains why "Live at Leeds" sounds so very life like...
Why this system might even reproduce "Hotblack Desiato of the rock group Disaster Area" is at near live concert hall levels...
Wow...What...What...What...I can't hear you...I have this ringing in my ears...

At these dangerous Db levels, you can understand that whenever somebody asks me to about my stereo, I always reply with:
Thunderbolt and lightning-very very frightening me- :rockon2: :rockon2:
Ok, I am being very naughty here, by bragging in all.
So, just spank me.:rotfl:
Baron030

[Hoerninger]

:rockon2: :rockon2:
Ok, I am being very naughty here, by bragging in all.

Realy?

1 Watt at a 110 dB/ W /m
or
200 W at a 87 dB /W /m .


For live sound it is good to look at efficiency.
____________
Peter

[Zilch]

I wear ear plugs at live concerts anymore.

I should strive to accomplish that "full experience" at home, too? :dont-know

[Hoerninger]

I should strive to accomplish that "full experience" at home, too? :dont-know
That has not been my intention. And Baraon030 talked about "dangerous Db levels".

I talked about live not meaning preserved. My short words should have pointed out, that there can't be made a live show - for a greater auditorium - with low efficiency speakers. That's why the play with numbers. (And for some it might be astonishing.)
____________
Peter

[Andyoz]

Threshold of Hearing 10-12
Rustling Leaves10-11
Whisper 10-10
Busy Street Traffic 107
Vacuum Cleaner 108
Large Orchestra 109.8
Military Jet Takeoff 140
Instant Perforation of Eardrum 160
Near total silence - 0 dB
A whisper - 15 dB
Normal conversation - 60 dB
A lawnmower - 90 dB
A car horn - 110 dB
A rock concert or a jet engine - 120 dB
A gunshot or firecracker - 140 dB

Interesting, these sorts of tables drive us mad in our industry as they are meaningless unless the measurement distance from the source is stated. I can get my portable TV to measure 100dB if I put the sound level meter mic at 1" from the speaker.

Also, are they talking about average (Leq) levels or maximum (Lmax) levels. There can be a 10dB difference in Leq and Lmax and that's a HUGE difference in Sound Power.

An average SPL in a listening room of 90-95dBA would be judged to be very loud by most listeners....except JBL listeners perhaps.:D

[Baron030]

Gee, I am surprised that no one has gotten my little “"Hotblack Desiato – Disaster Area” joke.:rotfl:
Actually, I have done more damage to my hearing by not using ear plugs, while operating power tools.
Routers and circular saws are the absolute worst on your ears.
Hearing loss is not reversible.
Once it’s gone, it’s gone forever.
So, I really don’t play my music very loud, for just that very reason.
Actually, what everyone should get out of this calculator discussion thread is an understanding of what their system is capable of.
Pushing any system way too hard will only leads to distortion and eventual speaker failure.
Since, completing my little Drew Daniels inspired “Ancient audiophile’s quest for the ultimate in satellite speakers” project.
I have learned that by running a large system at a small fraction of its total capacity, you get much lower distortion, and a much wider dynamic range as a result.
Now, if I could just find the room for 4 -2242s...
Baron030 :)

[Rusnzha]

Originally posted by baron030



I have learned that by running a large system at a small fraction of its total capacity, you get much lower distortion, and a much wider dynamic range as a result.
Now, if I could just find the room for 4 -2242s...



:cheers: :cheers:

[Baron030]

Gee, now I am really surprised that no one has gotten my little "Hotblack Desiato - Disaster Area" joke.

Well, for those of you that didn't get it, just follow these simple rules.
1. don't panic!
2. Consult the guide...

http://en.wikipedia.org/wiki/Minor_characters_from_The_Hitchhiker's_Guide_to_th e_Galaxy#Hotblack_Desiato

[JBL 4645]

it says to get 100db at 15 feet, I need 995 watts...hmmmmm, something wrong here ?

sens=87 according to manuf web site. and it also says I need 100-200 watts


LOL I was having the same difficulty at first then I twigged it. I have a different SPL db calculator that I’ve used for several years now.:)
http://www.stageaccompany.com/en/support/splcalc.php (http://www.stageaccompany.com/en/support/splcalc.php)