need formula, how loud will speaker play?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=129123
Printed Date: May 02, 2024 at 12:14 PM
Topic: need formula, how loud will speaker play?
Posted By: radarcontact
Subject: need formula, how loud will speaker play?
Date Posted: November 07, 2011 at 10:40 AM
Hey guys, I have seen the formula before but didn't understand it. Thought I did but the results were obviously wrong, and now I forget it.
Can someone dummify the formula (including how to punch it into a scientific calc, if that's not obvious) for me?
I want to compare speaker A to speaker B with a given amount of amp power, having the following numbers available to me:
Speaker driver sensitivity
Amp power per channel
Speaker ohms
Xmax
Power handling (NOM and MAX)
I think that's all I'll need, right?
Thank you...I'm still trying to learn. ;-)
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RadarContact
Replies:
Posted By: i am an idiot
Date Posted: November 07, 2011 at 10:43 AM
I think you are missing the one parameter that you really need. The speaker's Sensitivity will have a lot to do with what you are looking for.
Posted By: radarcontact
Date Posted: November 07, 2011 at 12:41 PM
It's there...  ------------- RadarContact
Posted By: DYohn
Date Posted: November 07, 2011 at 2:48 PM
https://www.doctorproaudio.com/doctor/calculadores_en.htm#calc_spl
You also need the distance from the driver to the listening position and if multiple drivers, are they acoustically in phase at the listening position or is the phase cancellation random (which is normally the case.) ------------- Support the12volt.com
Posted By: i am an idiot
Date Posted: November 07, 2011 at 4:47 PM
<<<<
Posted By: haemphyst
Date Posted: November 07, 2011 at 5:36 PM
Amplifier output, impedance, Xmax... None of those will have play in calculating DRIVER peak output. Amplifier power on hand will determine peak SYSTEM output, but that is not necessarily the driver's peak capability, is it...?
For a single driver, ON AXIS, a very general simplification is this:
Sensitivity, in dB, in my example, I'm using a 90dB efficient driver
Power handling, in watts, NOT how much power the amp has, UNLESS that's the lower number between driver handling or power available.
For each doubling of power handling in power capacity, add 3dB
90dB @ 1 watt
93dB @ 2 watts
96dB @ 4 watts
99dB @ 8 watts
...and so on and so forth.
Again, this is a grand oversimplification, and generally ONLY applies to true anechoic, truly infinite baffle measurements, but can be used as a very thumbnail calculation scale. Cabin/room gain and response curves, enclosure, (and as DYohn mentioned) distance from the drivers, can all make HUGE differences in total output of a system.
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: radarcontact
Date Posted: November 07, 2011 at 5:44 PM
Actually this is what I'm referring to, I just found it again, but am too ignorant to know how to use it! I have a scientific calc, but again, can't use it. Not mathematically educated.
Here it is:
10 x log10(Power) + Efficiency = Maximum Output
(Where)
Power = watts
Efficiency = decibels
Maximum Output = decibels
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RadarContact
Posted By: haemphyst
Date Posted: November 07, 2011 at 5:49 PM
All those logs, once actually calculated out will tell you just the same as I just did...
Double the power, gain 3dB.
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: oldspark
Date Posted: November 07, 2011 at 5:54 PM
So assuming that formula is correct (and you can add dB to Watts), you simply compare speaker "efficiency" for the power being compared.
Then just factor in directionality and spread.
Posted By: radarcontact
Date Posted: November 07, 2011 at 6:56 PM
Using that formula, I have 80 watts, 87 sensitivity, came up with 106 spl. Anyone concur?
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RadarContact
Posted By: DYohn
Date Posted: November 07, 2011 at 7:37 PM
One system at one meter, yes, assuming 87db is the system efficiency and not just the loudspeaker's sensitivity. ------------- Support the12volt.com
Posted By: radarcontact
Date Posted: November 07, 2011 at 7:55 PM
Thank you.  ------------- RadarContact
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