Using math to figure out how loud my speakers would be? - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 7 Old 11-10-2013, 06:29 PM - Thread Starter
Member
 
Harry Muscle's Avatar
 
Join Date: Jun 2007
Posts: 126
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Over the last few days I've been trying to determine whether my proposed 50W receiver (Marantz NR1603 or similar) would be powerful enough to drive the Pioneer SP-FS52 tower speakers I'm hoping to get. The majority of the answers seemed to have been yes, maybe, and no ... so I'm still trying to figure things out and I decided to turn to my good friend math to solve the problem.

However, since I'm not an acoustic expert I wanted to get feedback on this to make sure I'm not making some stupid assumptions or mistakes.

So here goes the math:

The speakers have a 87db sensitivity at 2.83V and are 6ohms. That means that they produce 87db at 1m when being driven with 1.33W (2.83V @ 6ohms = 0.47amps | 2.83V * 0.47amps = 1.33W). Doing some wonderful logarithmic math we see that going from 1.33W to 50W increases our sound output by 15.75db to 102.75db. However, that's at 1 meter away. I will be sitting 8 feet away or 2.43 meters. Again doing some math we figure out that this increase in distance will drop our db by 7.7db to 95db. Now assuming the exact same sound is being played by both left and right speakers we add 3db to the total volume bringing us to 98db.

So in the end I know that if I put 50W of power into these speakers I will get 98db from them at my sitting distance. Does all this make sense?

Now to figure out if 98db is loud enough without a db meter smile.gif

Thanks,
Harry
Harry Muscle is offline  
Sponsored Links
Advertisement
 
post #2 of 7 Old 11-10-2013, 06:33 PM
AVS Special Member
 
pokekevin's Avatar
 
Join Date: Jun 2011
Location: Huntington Beach, CA
Posts: 5,071
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 101
http://myhometheater.homestead.com/splcalculator.html ?

No subwoofer I've heard has been able to produce the bass I've experienced in the Corps!

Must..stop...buying...every bluray release...
pokekevin is offline  
post #3 of 7 Old 11-10-2013, 06:48 PM
AVS Club Gold
 
AV Science Sales 5's Avatar
 
Join Date: Sep 2011
Location: A beautiful view of a lake
Posts: 8,329
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 637 Post(s)
Liked: 525
Quote:
Originally Posted by Harry Muscle View Post

Over the last few days I've been trying to determine whether my proposed 50W receiver (Marantz NR1603 or similar) would be powerful enough to drive the Pioneer SP-FS52 tower speakers I'm hoping to get. The majority of the answers seemed to have been yes, maybe, and no ... so I'm still trying to figure things out and I decided to turn to my good friend math to solve the problem.

However, since I'm not an acoustic expert I wanted to get feedback on this to make sure I'm not making some stupid assumptions or mistakes.

So here goes the math:

The speakers have a 87db sensitivity at 2.83V and are 6ohms. That means that they produce 87db at 1m when being driven with 1.33W (2.83V @ 6ohms = 0.47amps | 2.83V * 0.47amps = 1.33W). Doing some wonderful logarithmic math we see that going from 1.33W to 50W increases our sound output by 15.75db to 102.75db. However, that's at 1 meter away. I will be sitting 8 feet away or 2.43 meters. Again doing some math we figure out that this increase in distance will drop our db by 7.7db to 95db. Now assuming the exact same sound is being played by both left and right speakers we add 3db to the total volume bringing us to 98db.

So in the end I know that if I put 50W of power into these speakers I will get 98db from them at my sitting distance. Does all this make sense?

Now to figure out if 98db is loud enough without a db meter smile.gif

Thanks,
Harry

If you want clean sound, then I would subtract 3 db, so you are not running the AVR at it's limit. Power compression may rob you a little bit, but not much, since you are now talking about only 25 watts out of the AVR.

Mike Garrett, AV Science Sales Call Me: 585-671-2968
Email Me: Mike@AVScience.com
Brands we sell: http://avscience.com/brands/ 
Call for B-stock projectors
Stewart, Seymour, SE, SI, Falcon, DNP & more.
RBH, Martin Logan, Triad, Atlantic Tech., MK Sound, BG Radia, SVS & Def Tech, Denon, Marantz & Yamaha .
AV Science Sales 5 is online now  
post #4 of 7 Old 11-10-2013, 07:07 PM
Member
 
olletsoc's Avatar
 
Join Date: Feb 2007
Location: clearwater, FL
Posts: 108
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 38
you also need to consider that that 50W max output is at 8ohm. at 6 ohm it is rated for a max of 80W
olletsoc is offline  
post #5 of 7 Old 11-10-2013, 07:36 PM
AVS Special Member
 
Join Date: Dec 2007
Posts: 4,278
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 238
87dB/2.83v/m, 2.43m, 47 watts into 8 ohms & 62 watts into 6 ohms will produce 96dB per one speaker or 99dB per 2 speakers.

The $300 Denon 1612/1613 can output 118.5 WPC into 8 ohms x 2Ch, 141.5 WPC x 2 Ch into 4 ohms.

74 watts/8 ohms & 98 watts/6 ohms will produce 98dB/1 speaker or 101dB/2 speakers.

If the speaker is all or mainly 8 ohms, then 118 watts into 8 ohms could produce 100dB/1 speaker or 103dB/2 speakers.
AcuDefTechGuy is offline  
post #6 of 7 Old 11-10-2013, 08:28 PM
AVS Addicted Member
 
Bill Fitzmaurice's Avatar
 
Join Date: Nov 2009
Location: New Hampshire
Posts: 10,169
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 1675
Quote:
Originally Posted by Harry Muscle View Post

So in the end I know that if I put 50W of power into these speakers I will get 98db from them at my sitting distance. Does all this make sense?
Almost. First off, you want 6dB of headroom, so a realistic figure of how much power you'll be delivering is 12.5w. If you really need 50w continuous output you want at least a 200w/ch amp. That takes you down to 93dB, but in practical terms that's probably plenty. However, there are two errors in your calcs. The inverse square rule applies in an anechoic space. In a room you can figure a 3 to 4dB loss per doubling of distance from the source will be closer to the actual. And two speakers driven with the same voltage level produce 6dB more than one.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
Bill Fitzmaurice is online now  
post #7 of 7 Old 08-24-2014, 10:28 AM
Okv
Member
 
Okv's Avatar
 
Join Date: Jul 2010
Location: Aalesund, Norway
Posts: 196
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 43 Post(s)
Liked: 42
http://www.kvalsvoll.com/Articles/Au...culatorspl.htm

This will calculate all you want to know about spl and power for loudspeakers.

Just keep in mind that even though the calculator is theoretically correct, the usability of the calculations will depend on the accuracy of the input data, meaning, if the specified sensitivity for a speaker is off, then the calculated spl will also be wrong.
Acoustic properties of the room and speaker radiation will also be approximate.

If you dimension for spl as measured with ordinary spl meters, you should add at least 15-20dB from a dB(C) value, because peaks will be significantly louder than the average.

EDIT: Did not notice the date, this is a very old thread..

Last edited by Okv; 08-24-2014 at 10:30 AM. Reason: Old thread
Okv is offline  
Reply Speakers

Tags
Marantz Nr1603 Slim Line Av Receiver , Pioneer Andrew Jones Sp Fs52 Flr Stand Loudspeaker
Gear in this thread

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off