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MultiWay Conventional loudspeakers with crossovers 

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View Poll Results: I measured the test tone at:  
2 volts or less  143  37.34%  
Between 25 volts  130  33.94%  
Between 510 volts  51  13.32%  
Between 1020 volts  23  6.01%  
Over 20 volts.  36  9.40%  
Voters: 383. You may not vote on this poll 

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27th January 2012, 11:31 AM  #101 
diyAudio Member
Join Date: Jan 2009

It definitely works. For my test (details in the full range section), I recorded 0.75V with my 98dB @ 1W speakers. Squared gives 0.5625W. If you work it out long hand, 0.75V @ 8 ohms gives 0.0703W (V^2 / R) at 12dB. Each 3dB is double power, so 0.1406W at 9dB, 0.28125W at 6dB and 0.5625W at 3dB (biggest sine wave possible).
So what happened there, well to work it out Pano's way, I squared the voltage. To do it long hand, I squared the voltage, divided by 8 (speaker impedance) to work out power, then multiplied by eight (3 doubles) to get from 12dB to 3dB. Cool, wish I had thought of that. Brian. 
27th January 2012, 12:21 PM  #102 
diyAudio Member
Join Date: Jul 2005
Location: leeuwarden

I also did the test.
"normal" listeninglevel gave me 0.5v, Loud (at the treshold of being annoyingly loud) gave me 23v. This was on ~88dB/2.83v/1m loudspeakers, 4 ohms impedance. (3*3)/4=2.25 times 8 gives me 18 watts. 
27th January 2012, 01:43 PM  #103 
diyAudio Member
Join Date: Jan 2011
Location: Ladysmith, BC

Ok I get it now. Whew!

27th January 2012, 02:49 PM  #104 
diyAudio Moderator

And we have a winner, ladies and gentleman! Please give a nice round of applause to Brian  Brig001.
He explained it very well and succinctly, but I'll go over it again. Mooly was getting there, too.
Your speakers may not be exactly 8 ohms, but the voltage you measured can be tracked back to an amplifier's 8 ohm rating. If you have 4 ohm speakers you might want to go by the amplifier's 4 ohm rating. Simply take your measured voltage, square it, then double that to find the 4 ohm power rating you need. If an amplifier is honestly rated*, for example to AES or IEC standards, then it can output a sine wave at the rated power into the specified load. 8 ohms, 4 ohms, whatever. Peak voltage will be 3dB higher, or twice the power. The amp may be able to supply a little more voltage, but it's going to soon start distorting and clipping. This little test is simple, it lets you measure a voltage, then multiply it to get a reference level. E.G. "I measured 3V on the test tone OK, I need at least a 9 watt amp to play that loud". *Yes, we all know that the marketing department writes the specs, but you are smart enough to see thru that. Look for IEC ratings, or better yet, measure for yourself! 
27th January 2012, 02:54 PM  #105 
diyAudio Moderator

You went a step too far. All you needed to do is 4x4=16. That's the power rating of the amp you need. (see my post above) You made the mistake of squaring that again to get to your result. Good effort, but one step too far.

27th January 2012, 03:08 PM  #106  
diyAudio Moderator

Like Ra7, you are making it too complicated.
Quote:
If you want to know how many watts that is into your 2.7 ohm load, do this: 19.8x19.8/2.7=145 You need an amp that can supply about 150 watts RMS into a 3 ohm load. See? 

27th January 2012, 03:09 PM  #107 
diyAudio Member
Join Date: Sep 2002
Location: Lakewood, Ohio

Don't you need to use the same digital source to play the test tone as you used to play the high volume music?
It's important that no volume adjustments are made between playing the two tracks.
__________________
Kevin 
27th January 2012, 03:29 PM  #108 
diyAudio Member
Join Date: Mar 2009

2.5v rms into 4 ohm load.
I had it cranked up listening to some rock. I may not listen to it at this level for long because it is hard on the ears. The speakers are quite efficient in the 93 db range. This DIY chipamp will do about 10v rms into 4 ohm resistors continuous, both channels driven before clipping. I will have to try my other listening system. Fun test! 
27th January 2012, 03:41 PM  #109  
diyAudio Member
Join Date: Nov 2005
Location: crete

Quote:
your way is wrong. unless if an 150watt rms amp can give 890 watt peak power. 

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