ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  
Pages: [1]   Go Down

Author Topic: SPL and Sensativity explained?  (Read 2224 times)

Dan Haddad

  • Full Member
  • ***
  • Offline Offline
  • Posts: 171
SPL and Sensativity explained?
« on: March 29, 2005, 02:15:23 pm »

Hey guys i am still debating between the SRX715, and the SRX725 speakers, i know bolth are great speakers. I have some questions about max SPL and system sensativity.

The 715 is rated: 800(continus) 1600(Program) 3200(peak)W, Sensativity is 96db 1w@1m, max SPL is 131

the 725 is rated at 1200(cont.) 2400(program) 4800(peak)W,
Sesnativity is 99db 1w@1m,max SPL is 136

The 715's will be pushed at around 1500 watts with my amps, the 725 will be pushed around 2000 with my amps(bridge mono, 1 amp per speaker)

Could someone explain what the diff sensatvities mean, i have heard that with SPL every 3 SPL db's means the perceived sound is doubbled, is this true?

Also with theese speakers do i want to run them closer to the continus rated level? what exactly is the program level? Also i was told the reason theese need so much power is because they have a lighter new magnet and dissapte most of the power as heat, not sound.

Thanks Everyone!
Logged
Hotmix Entertainment
http://Http://www.hotmixent.com
Michigan Mobile DJ Service.

Al Limberg

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1482
Re: SPL and Sensativity explained?
« Reply #1 on: March 29, 2005, 02:36:54 pm »

Well you're on the right track - just wandered off a little.  A 3db increase in output requires double the power.i.e., the 715 would require 2 watts to generate an output of 99db/spl.  Now to put this in perspective, a 3db change is about what it takes for the human ear to say "aha!  that got louder!" while typically a 10db increase is accepted as what we interpret as being "twice as loud".  (A 10db increase requires 10x the power BTW).  As regards the proper power for these cabinets, a quick trip to the study hall should work wonders for you (link at top of page).  What should be readily apparent is that the 725 will be noticeably louder with the same input as the 715 as well as being able to handle more power.

Regarding 'power handling' and heat, it should be apparent that efficiency is the key here. That might be defined as the ability of the transducer to convert input energy into sound. Heat is the requisite by-product.  Again, this could turn into a book just bringing up the whys and wherefors and what to watch out for.  Hit the study hall good man - you'll be glad you did.

HTH,
Al  
Logged
If the automobile had followed the same development cycle as the computer, a Rolls-Royce would today cost $100, get one million miles to the gallon, and explode once a year killing everyone inside - Robert X. Cringely

Allen Alonzo (tazada)

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 58
    • http://technicallysound.biz
Re: SPL and Sensativity explained?
« Reply #2 on: March 30, 2005, 06:40:26 am »

I was never good at DB, but as he said above, 3DB raise in SPL requires 2x the power.  If you make a chart like this:

96db @ 1w/1m  to add 3db power doubles so

99db @ 2w/1m  add 3db double power again...

and so on.....

102db @ 4W
105db @ 8W
108db @ 16W
111db @ 32W
114db @ 64W
117db @ 128W
120db @ 256W
123db @ 512W
126db @ 1024W
129db @ 2048W
132db @ 4096W

If you iterprolate, 131db would fall at about the 3000W max they spec, so it works.  You can make the same chart for the other speaker.  As you can see, it starts to require HUGE power to make it seem louder(3db), and GOBS of power to make it twice as loud (10DB gain), not to mention how fast the dbs drop with distance.....

Well folks, did I get that right????
Now, my question is, if you bump the mains slider so you send a 3db hotter signal from your mixer, is it linear to the speakers?  IE did you just double the power to the speaker terminals?

Cheers,
Allen
Logged

Ryan Lantzy

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2291
    • http://www.lhsoundandlight.com
Re: SPL and Sensativity explained?
« Reply #3 on: March 30, 2005, 07:26:34 am »

tazada wrote on Wed, 30 March 2005 06:40

I was never good at DB, but as he said above, 3DB raise in SPL requires 2x the power.  If you make a chart like this:


You could just do the math... 10*log(p1/p2) + Sensitivity or the opposite calculation 10^((SPL - sens)/10)
p1/p2 can be reduced to p1 if p2 is 1 watt. BTW 10^() means ten rased to whatever power in the parens.

If you are doing these on a calculator....

To find how loud a speaker can get (not taking into account power compression and other weirdness) use the first equation.  With your example of a 715  96 dB + 10*log(3200) = 131.05 dB max

3200 log x 10 + 96

To find the power required to get your particular speaker to a certain volume, use the second equation.  Say you want to hit 124 dB.  10^((124-96)/10) = 630.96 Watts.

124 - 96 / 10 then hit the 10x key (the x should be superscript) which is usually found above the log key if you calculator has it.

Most of this stuff can be found in the Study Hall on here.

Quote:

Now to put this in perspective, a 3db change is about what it takes for the human ear to say "aha! that got louder!"


I think this is very subjective... Kind of saying what is "twice as loud."  Very hard to qualify.

Quote:

Could someone explain what the diff sensatvities mean, i have heard that with SPL every 3 SPL db's means the perceived sound is doubbled, is this true?

Also with theese speakers do i want to run them closer to the continus rated level? what exactly is the program level? Also i was told the reason theese need so much power is because they have a lighter new magnet and dissapte most of the power as heat, not sound.


Generally, the more senstive a speaker, the better.  It means your power requirements will be less.  That's a good thing.  Generally speaking, a higher sensitivity, indicates that the speaker is more efficient allowing it to turn more electricity in to actual sound.

As far as where to run them... Continuous power is (correct me if I'm wrong guys) more a measure of the speakers capacity when dealing with content with a high average to peak power ratio.  Like a sine wave.  Signals that are not very dynamic (heavily compressed material) will max out at a speakers continuous level.  The Program rating is more of a real world rating as far as musical content goes.  Since, music is usually very dynamic, the average power is pretty low.  There are huge peaks however.  There's where your peak rating comes in.  Basically, if you run either of those speakers at their continuous rating (800 and 1200) you'll have about 6 db of dynamic headroom in your system.  Which is acceptable.  It will also mean your speakers are averaging a SPL in the mid to upper 120s.  That's pretty friggin loud.

Logged
Ryan Lantzy
"In the beginner's mind the possibilities are many, in the expert's mind they are few."

Jonathan Novick

  • Full Member
  • ***
  • Offline Offline
  • Posts: 165
Re: SPL and Sensativity explained?
« Reply #4 on: March 31, 2005, 02:38:08 am »

One thing to point out here is that sensitivity is not the same as driver efficiency. Sensitivity measurements are impacted by the directivity of the speaker enclosure/horn. If you were to take two identical drivers and place them into two different horns, the horn with the narrower dispersion will have a higher sensitivity reading. The proper tradeoff between sensitivity and dispersion angle will depend on the applicaiton.
Logged

Tom Reid

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 7412
Re: SPL and Sensativity explained?
« Reply #5 on: March 31, 2005, 02:37:34 pm »

sawdust12 wrote on Thu, 31 March 2005 01:38

One thing to point out here is that sensitivity is not the same as driver efficiency. Sensitivity measurements are impacted by the directivity of the speaker enclosure/horn. If you were to take two identical drivers and place them into two different horns, the horn with the narrower dispersion will have a higher sensitivity reading. The proper tradeoff between sensitivity and dispersion angle will depend on the applicaiton.


Yeah, that's correct.
But, in the aspect of an full range cabinet, the passive crossover is going to do more work to give you a sensitvity rating then any horn/driver combination.

Bi-amping changes that aspect.

Individual horns and mid cabinets make one rethink those issues.
Logged
tom

What does Buddha do on his day off?
Pages: [1]   Go Up
 

Page created in 0.043 seconds with 21 queries.