A Test. How much Voltage (power) do your speakers need?

I measured the test tone at:

  • 2 volts or less

    Votes: 335 40.4%

  • Between 2-5 volts

    Votes: 255 30.8%

  • Between 5-10 volts

    Votes: 107 12.9%

  • Between 10-20 volts

    Votes: 55 6.6%

  • Over 20 volts.

    Votes: 77 9.3%
  • Total voters
    829
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#1,003
BigE said:
I thought it you were listening to something at an average volume of one watt and then a 20dB peak showed up, you'd need to have 100 watts on tap to cover it.
Click to expand...
That's true. IF you are listening to a digital recording that has an average level of -20dBFS (full scale) at an amplifier output of 1 watt, you'd need 100 watts for the peaks. That's 28.3 volts peak into an 8 ohm load.

CDs with good dynamics can be 20-24dB average below peak. If you need 1 watt to get the average level you want, then you'll need 100 watts or more for the peaks. Say about 30 volts for 8 ohm speakers.

It all depends on your speakers, your room and how loud you want it, average. The poll above gives you a good idea of the voltages some people here use. For example, my system uses a fraction of a volt at average listening levels. Someone else with a bigger room and/or less efficient speakers will need higher voltages for those same levels.

This test allows you to determine the voltage ranges you might use.
 
#1,005
I would love to, but can't figure out the DR ratings. :xeye: I analyze a track and look at RMS value of the track. That way I know how far below peak the average is. -18dB is typical for some older rock/pop CDs. -24dB is common in classical works.
 
#1,007
OK, so it seems that the DR rating given by things like JRiver is the crest factor DR -- the # of dB for a peak above the average that is present on the recording.

So yes, if there is a DR of 10 ( fairly common ), you'll need 10x average power to ensure your amp does not clip. A DR of 20 will need 100x average power, and a DR of 30 will need 1000x average power.

I've never seen a DR of 30, but would probably be there at a live event.

The highest I am aware of is a DR of 22.

So it seems that if you listen to music with a 1 watt average, you'll need a 100 watt amp.
 
#1,012
Pano said:
It can be surprising how little voltage we actually get out of our amp outputs on a daily basis. If you get into a much larger space and higher SPL, the voltage will go up quickly. At home, it's usually pretty tame.
Click to expand...

Yes, and this would go hand in hand with the popularity of 100W/ch in the pre-home theatre era. If you're working on 1W base and 20dB DR, that would have permitted over 80dB/1m for most stereo speakers at the time. 80dB/1m wouldn't have permitted a club party (and so many found out when their tweeters didn't work the day after) but it would have been more than enough for regular listening.
 
#1,013
So I did the test and got 2.23V with the 120hz test tone. Room is 8m x 5.5m x 2.4m, about 43sqmeters. Speakers are Rega rs3 6ohm, 89db)

So I need 8.92V peak voltage from my amp. The power calculation you propose is for 8ohm speakers, how would I go and calculate for 6 or 4 ohm ones?

If I understand correctly then I take the 2.23*4= 8.92 then I square that: 79.57 and divide by the impedance of speakers: 79.57/6= 13.26W needed.

Is my calculation reasonable?
 
Last edited:
#1,014
Your calculation looks reasonable to me.

These days, I'm doing quite a lot of PA work - a Behringer NU6000DSP is feeding a Beyma 15P1200Nd a side, for somewhere around 1.5kW peaks per side. Sometimes I have to mash into the limiters a bit to keep up with drummers.
Some subwoofers ought to help...

Chris
 
#1,015
Hello Santos. Thanks for posting. :up:

Since you measured 2.23 volts, I figure that you need about 6.3V RMS for the loudest signal, or about 9 volts peak, as you said.

How do you know if an amplifier can supply that? Well, you could measure it while looking for clipping or distortion. Or you could calculate backwards from the specifications. How would an amp that can supply 6.3V RMS be rated? Use Ohm's law.
  • 10 Watts RMS into 4 ohms
  • 6.6 Watts RMS into 6 ohms
  • 5 Watts RMS into 8 ohms
That's not a lot of power. But that's what you need, minimum. You may be happier with a more powerful amp because it has a bigger power supply than you need (that can sound good), and lots of headroom. But that's up to you to decide. You now know what your minimums are for the volume setting you used.
 
#1,019
yes adding that to post1 would help all those that can't find the actual post.
There are probably other posts that give the method, but I tried searching the first 200 and missed finding the answer.
When post 994 came along, I then remembered how simple it was. But that was a week after I had already searched for the method.
 
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