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

## I measured the test tone at:

• ### Over 20 volts.

• Total voters
818

#### Mooly

Paid Member
You have to go off the readings from the test tone. If you listen with bass and treble at maximum and you measure 6.6 volts rms on your meter then you need a 44 watt amplifier.

More correctly, converting that to a voltage means you need an amplifier that can maintain 19 volts rms into whatever load impedance your speakers are.

So if you really listen at those levels then your amplifier is probably right at the limit before it may start to clip.

#### Pano

Paid Member
Thanks Mooly for all the clear answers while I'm off traveling.
I will recap some of this toniight or tomorrow when I'm home. Mooly has answered everything very clearly and accurately.

Paid Member
No problem

#### Hiten

Ok, I surfed through the thread and and you are right. I will need 44 watts amplifier (in my system) if I listen to very loud with bass treble at maximum. I also calculated wattage requirement for my minimum reading of 2v by information in this post #562. It turned out to be 4 watts. Mind you this is loud above normal level so I think I can still get away with little less wattage amplifier. Thanks very much for the effort Pano, Molly and 5th element.
Best Regards.

Paid Member
You're welcome!

#### Pano

Paid Member
Voltage Test FAQ

After all these years, there is still some confusion about the test. Here are some Frequently Asked Questions.

• Q: How (or why) do I set my volume level? Is it a valid level?
• A: You can set the volume anywhere you like as long as it's below clipping, and the test will be valid for that volume setting. The idea here is to find the max level you normally use and then determine your peak voltage. You could just set your volume control to the loudest point you remember using it, and go from there.
• Q: How do I know this is the right level?
• A: You don't. But the test is valid for whatever level you set. That could be your max level, your average or anything else. For this test we are looking for your loudest level.
• Q: Should I measure a music signal?
• A: No. For this test we use a sine wave signal of a known value. We can calculate all other values from that. Any volt meter with a 2V or lower scale should give an accurate reading on this test.
• Q: Why is -12dBFS used? Is that a reference?
• A: -12dBFS is the RMS value of the test signal for several reasons. It's loud enough to be easily measured, but not too loud to cause problems. -12dB is also convenient for some of our calculations.
• Q: I have a CD with a 0dB tone, can I use this?
• A: Yes, but be careful, that's loud! That's 8 times more power to the speakers than our test signal. Depending on where your volume is set, you may damage your amp, your ears or your speakers. If you do use a tone like this, please report it in the thread and we can adjust your measurement.
• Q: Do I need to multiply my meter readings by 12dB to post them?
• A: No. Report your direct readings. That's what is in the poll results.
• Q: What's the point of this test? What does it tell me?
• A: The test gives you a good idea of the voltage levels going to your speakers at a given volume setting. You could test other volume levels too.
We tend to think of amplifiers in terms of power, because that's how they have almost always been rated. But the vast majority of audio amplifiers we use are a voltage source. Their output voltage is dependent on the input signal, not the load connected to the outputs. Using volts as an output measurement is not load dependent. Speaker ohms don't matter.

* The test signals posted to this thread have an RMS value of -12dBFS. That means that the average level is 12dB below the absolute maximum digital level called Full Scale. The signals are 9dB below the maximum allowed for a non-clipped sine wave. Why? Because a full volume sine wave will have an RMS value of 3dB below Full Scale. You will often see this referred to as a 0dB sine. In a way, it is, because you can't have a pure sine any louder in the digital domain. It's all in the point of reference.

Early CDs were often mastered at -18dB RMS as an average level, with peaks hitting 0dB throughout the song. Classical and some jazz might be mastered at -22dB to -24dB with peaks at 0dB. Loud CDs tend to be in the range of -15dB and some of the over-compressed "Loudness Wars" CDs and digital tracks are mastered at -10dB with many clipped peaks.

#### scottjoplin

Thanks Pano, that clears up a few things in my mind. My question is the one I kept coming back to with (the long suffering{with me anyway, ha!}) Mooly....he very helpfully uploaded some music in the same format as the test file for me, was this necessary? I mean was having the chromecast as my common source adequate?

#### Pano

Paid Member
I can't tell you if Chromecast is "adequate." Is it your main source? Is it what you normally use? It's a digital device, so it's suited to this test.

#### scottjoplin

Well, it's what I used to do the test, and I mean would it have been adequate for the purpose of the test if I'd used it to play the test file after setting my volume on the amp after streaming music on line through it also? My main usual source is a Marantz CD player, I'm not a complete philistine, haha!

#### Mooly

Paid Member
Yes it is adequate for this test.

The key important thing was that the file of Pano's and the music file should be played in the same way on the same equipment.

If I listened to the YouTube clip of the music, and then listened to the wav file I created from a CD then I'm pretty sure you would find the levels different. Both have to be treated the same way. Yes

Its like listening to the same radio show on DAB and on FM with both tuners feeding the same amplifier. Switch between the two sources and the levels will be different, even though both are the same material.

So what we have done in your case is fine, and the only way to do it really.

#### scottjoplin

Yes, I think you are right, and thanks for looking after my "case file" haha

Paid Member
No problem

#### msibilia

I mean was having the chromecast as my common source adequate?

If you are using Chromecast Audio, it is probably fine, but you have to be sure that you have turned audio compression off (in Google Home find the device and under settings, turn <Full Dynamic Range> to On [link to directions]). I don't know why they decided that compression should be the default. Then all the levels should be linear and the measurement valid.

Marc

Last edited:

#### Mooly

Paid Member
That's a great summary by Pano. It might be worth a copy and paste of that adding to post #1

#### Mrcloc

This is great, thanks! I'll do my tests sometime as well.

Based on this test, it would seem few people need any more than a 25 W/8 ohm amplifier (5 V measurement). Why, then, are hifi amplifiers of >150 W (8 ohm) so sought after? I mean, a McIntosh 2.4 kW used to its maximum will mean you measure 49 V! I've always thought > 200 W is pointless, but I've always assumed these ratings allow for very good dynamic range (lots of headroom). It seems 25 W gives heaps of headroom. Is it for home theater, where you need to shake the room with massive explosions?

#### scottjoplin

If you are using Chromecast Audio, it is probably fine, but you have to be sure that you have turned audio compression off (in Google Home find the device and under settings, turn <Full Dynamic Range> to On [link to directions]). I don't know why they decided that compression should be the default. Then all the levels should be linear and the measurement valid.

Marc

Hi, thanks for that. I'm using the original chromecast with an "audio extractor", I don't know how they compare audio quality wise. As far as I know there is no mention of compression with the one I have.

#### Pano

Paid Member
That's a great summary by Pano. It might be worth a copy and paste of that adding to post #1
There is a link there now.
Based on this test, it would seem few people need any more than a 25 W/8 ohm amplifier (5 V measurement). Why, then, are hifi amplifiers of >150 W (8 ohm) so sought after?
Lust for power? Because we can?
The extra headroom is not a bad thing, and power number get larger faster than the voltage numbers, so power increases seem big right away. Similar to the ASA vs DIN film speeds. Big numbers sell. I suspect that the big power supplies the sound, too.

The old stereo consoles of yesteryear that could fill a whole room, or even a whole house, run about 35 WPC. That was plenty. And for most speakers in most rooms, 25-30 WPC is enough. That would be about 15 volts RMS max out of the amp. With efficient speakers and medium size rooms, 7 volts is enough.

But not all rooms are small, not all speakers efficient, not all levels reasonable. As the room gets big, you need a lot more power, fast. Or if you get a nice level in your living room with speakers at 92 dB/W, you'll need 10X more power for the same level out of 82dB/W speakers. Yes, those exist.

#### Mrcloc

I'm going to go with: "Because we can."

I can't reach 100 W (40V peak). I've tried - it's just far too much, but I tell you, try to market a 50 W stereo amplifier and the audiophiles laugh at you. I'm currently driving my speakers off a 50 W, and I haven't heard any clipping yet, and I've really pushed it hard. And they're not extremely efficient speakers either (in my very big room - 7 x 5 meter floor area and about 2.6 meter high roof).

#### Mrcloc

Goodness, that's a LOT! Even 82dB speakers must have been very loud and moving like mad. Even so, that's still only 100W. 150W would be 50V, and that's a good 25% more voltage. I don't know. I've achieved that power, but is it even necessary is something I need to investigate more.