How much amplifier power is required?

[6speed]

Maybe if those people who think they only need a few watts, attached a 'scope to the speaker terminals, let it free run and watched their peaks being chopped off flat on transients, while playing moderately loud dynamic music, they would throw out all their carefully calculated numbers...

Would they be able to see the clipping or would it happen too fast? If it's the latter, couldn't you calculate the average power, then have a computer program tell you how many dB the avg is below the peak for that track, and that would tell you the headroom you need in your amp?

 

[6speed]

...have a computer program tell you how many dB the avg is below the peak for that track, and that would tell you the headroom you need in your amp?

...which is effectively Pano’s test, right?

 

[DonH56]

Would they be able to see the clipping or would it happen too fast? If it's the latter, couldn't you calculate the average power, then have a computer program tell you how many dB the avg is below the peak for that track, and that would tell you the headroom you need in your amp?

Most 'scopes today are DSOs and infinite persistence is built in (so yes). They still have dead time, however, though for much different reasons. But you can use peak triggering and all that jazz.

 

[Putter]

So all systems without subs have deficient bass performance?

I did overstate the case a bit. There's a conflict between the optimal location for stereo speakers for best imaging (away from the walls and off the floor) and the best locations for subs (on floor and near wall esp corners and anywhere between 2 and 4 subs) for the most even bass reproduction.

 

[Willem]

I agree that subs are only the icing on the cake and by no means absolutely necessary (audio is full of compromises). However I like them and I agree that the best location for the main speakers is often not the best for subs.

 

[RichB]

Would they be able to see the clipping or would it happen too fast? If it's the latter, couldn't you calculate the average power, then have a computer program tell you how many dB the avg is below the peak for that track, and that would tell you the headroom you need in your amp?

A digital file can be analyzed and the maximum voltage determined.
I measured stereo playing 0 dBFS sine-waves at 2.83 volts that is 1 watt at 8 Ohms.
This measured 86 dB at my seating position in stereo.
Since the salon2s are 4 Ohms 86 dB uses 2 watts maximum.
I used spreadsheet to compute power at 3 dB increments and then labeled my typical listening levels.

With digital sources, a voltmeter, an SPL meter and a spreadsheet, one can reduce the amount of handwaving.

Don't get me wrong, I have hooked up a 100 WPC Yamaha receiver and subjectively it sounded flat to me. Not all amps handle reactive loads and low impedances the same. AVR's like my Yamaha have protection mechanisms that restrict power when a temperature increase is detected. The power measurements don't tell the whole story.

- Rich

 

[folzag]

I measured the power at 2.83 volts and measured the volume of sine-waves at my 12 foot listening position, then used a spreadsheet with my typical listening levels.
- Rich

Nice table. That last row should be "No really. Never."

 

[RichB]

Nice table. That last row should be "No really. Never."

Really, but in a few minutes I can bridge the amps, should whim overcome me.

- Rich

 

[jamestown]

Can I get an opinion as to the usefulness of using a calculator like the one linked below to determine my power needs? If my goal is to have 80-85db at the listening position, with 20db more to cover any peaks without distortion.

For instance, in my office:
100wpc clean (A-s801)
4 feet from the speakers
84.5db/2.83V/m (LS50)
Calculator says ~105.4db output

For my living room:
100wpc clean (A-s801)
12 feet from the speakers
88db/2.83V/m (Q750)
Calculator says ~102.7db output

https://myhometheater.homestead.com/splcalculator.html

 

[DonH56]

It at least tries to account for boundaries and speaker placement so should get you in the ballpark.

 

[yodog]

Fascinating subject indeed.

Is there a way to measure the preout voltage of the rca preouts using a fluke multimeter?

was wanting to know the preout voltage on my Musical Fidelity M2si and see if it’s outputting enough juice to effectively drive my Anthem MCA 225..... which in turns drives my 4ohm dynaudio’s.

Another question,
Let’s say my physical round shaped volume knob, with no click feedback just smooth and rotating, starts at the 630-7 o’clock position for zero volume, gets barely audible at 8-830 o’clock volume, and is very loud but not unbearable at 930 o’clock .... and goes all the way to 430-5 o clock, is it normal to not hear anything at all for a moderate portion of the beginning of the volume dial? I feel something is mismatched between my components. It goes like this:

Bluesound Node 2i using line level stereo preout RCA’s —-> musical fidelity m2si integrated amplifier, to it’s line level rca preouts (manual says it’s there for bi-amping) ——> anthem MCA 225 rca inputs (has xlr as well but not using them at the moment) —-> dynaudio 4ohm Standmounts + two small rel subwoofers (one per each side using speaker level connection)

so can I/should I try and measure the rca preout voltage on my m2si? See if I’m getting the full 400wpc rms @ 4ohms that Anthem claims?

 

[DonH56]

Fascinating subject indeed.

Is there a way to measure the preout voltage of the rca preouts using a fluke multimeter?

was wanting to know the preout voltage on my Musical Fidelity M2si and see if it’s outputting enough juice to effectively drive my Anthem MCA 225..... which in turns drives my 4ohm dynaudio’s.

Another question,
Let’s say my physical round shaped volume knob, with no click feedback just smooth and rotating, starts at the 630-7 o’clock position for zero volume, gets barely audible at 8-830 o’clock volume, and is very loud but not unbearable at 930 o’clock .... and goes all the way to 430-5 o clock, is it normal to not hear anything at all for a moderate portion of the beginning of the volume dial? I feel something is mismatched between my components. It goes like this:

Bluesound Node 2i using line level stereo preout RCA’s —-> musical fidelity m2si integrated amplifier, to it’s line level rca preouts (manual says it’s there for bi-amping) ——> anthem MCA 225 rca inputs (has xlr as well but not using them at the moment) —-> dynaudio 4ohm Standmounts + two small rel subwoofers (one per each side using speaker level connection)

so can I/should I try and measure the rca preout voltage on my m2si? See if I’m getting the full 400wpc rms @ 4ohms that Anthem claims?

Check the bandwidth of the Fluke then apply a test tone (download or whatever) within that bandwidth and measure the output voltage. Most Fluke's cover the audio band, but many multimeters are designed for measuring the AC wall voltage and roll off over a few hundred Hz or so. Others extend to 100 kHz or more. Check your specs. Also check if it is an RMS meter (most are these days).

If it plays loudly enough, it has enough "juice".

Volume knobs typically have a logarithmic taper to provide finer adjustment at lower volume and less at higher since we are less sensitive but not all of them do that; it is up to the manufacturer. So it is normal to hear nothing or very little at one extreme, and be as loud as we would normally like around the half-way point or so. If you are reaching full volume after only a little knob travel, then you could turn down the gain or the amplifier (if possible), adjust trim levels in your preamp (ditto), or add in-line attenuators to reduce the preamp's output and give yourself more range. Or if it works well enough now just move on and avoid the rabbit hole.

HTH - Don

 

[yodog]

Check the bandwidth of the Fluke then apply a test tone (download or whatever) within that bandwidth and measure the output voltage. Most Fluke's cover the audio band, but many multimeters are designed for measuring the AC wall voltage and roll off over a few hundred Hz or so. Others extend to 100 kHz or more. Check your specs. Also check if it is an RMS meter (most are these days).

If it plays loudly enough, it has enough "juice".

Volume knobs typically have a logarithmic taper to provide finer adjustment at lower volume and less at higher since we are less sensitive but not all of them do that; it is up to the manufacturer. So it is normal to hear nothing or very little at one extreme, and be as loud as we would normally like around the half-way point or so. If you are reaching full volume after only a little knob travel, then you could turn down the gain or the amplifier (if possible), adjust trim levels in your preamp (ditto), or add in-line attenuators to reduce the preamp's output and give yourself more range. Or if it works well enough now just move on and avoid the rabbit hole.

HTH - Don

Thank you Don, this was the kind information I was trying to get to. It really helps and actually helps prevent me from almost making a thousand dollar mistake. Thanks again, cheers.

 

[pjug]

Most 'scopes today are DSOs and infinite persistence is built in (so yes). They still have dead time, however, though for much different reasons. But you can use peak triggering and all that jazz.

If you have a scope this really is a good way to get an idea. Just be careful; I use two probes on the speaker + and - and the scope function A-B. Even though my amp is not bridged, just to be sure.

 

[veeceem]

Your spreadsheet may need some adjustment.

2.83V is 1 watt into 8 ohms. your speakers are closer to 4 ohms. (3-5 at bass where the power is). 2.83V at 4 ohms is 2 watts, twice as much. You need to double all your power numbers.

View attachment 45069

Since you give Salon2 as example, may I ask how much power at 4Ohm I need to play @103 SPL from 3meters seat in a 25m2 room?
Thanks

 

[RichB]

Since you give Salon2 as example, may I ask how much power at 4Ohm I need to play @103 SPL from 3meters seat in a 25m2 room?
Thanks

104 watts - Based on stereo measurements in my room that is similar size with ceiling ranging from 8 to 14 feet.

- Rich

 

[veeceem]

104 watts - Based on stereo measurements in my room that is similar size with ceiling ranging from 8 to 14 feet.

- Rich

Was -10dB by sitting 3meters away included?
Thanks

 

[RichB]

Was -10dB by sitting 3meters away included?
Thanks

Yes and room gain because it is measured at the listening position.

I measured 0 dBFS sine waves at my listening position in stereo with the XMC-1 set to -31 which produced 2.83 volts (measured with a Fluke 87 multi-meter). Since the Salon2's are basically 4 ohms, this computes to 2 watts. From there, I created a spread sheet that includes my typical listening levels, the XMC-1 volume setting, and the maximum power for a digital signal (excluding inter-sample overage).

You can view the spreadsheet in this post:
https://www.audiosciencereview.com/...mplifier-power-is-required.10781/#post-300381

I also compared my computations to this power estimator (https://myhometheater.homestead.com/splcalculator.html )
that includes room gain and speaker count in this post:

https://www.audiosciencereview.com/...mplifier-power-is-required.10781/#post-300476

The calculator computed 104.9 max at 180 watts (rated value for the AHB2 into 4 ohms) versus 128 that is based on in-room measurements, that is approximately a 1 dB difference.

So even with maximum gain in this calculator, it is computing a bit more power required.
The AHB2's include clip indicators at 1% and these illuminate at levels corresponding to my in-room measurements.

With digital sources, the maximum signal 0 dBFS so power estimation is better than analog.
All of my sources are digital.

If you have a multi-meter, an SPL meter, and a spreadsheet you can perform your own analysis in your room. It's good geek fun.

- Rich

 

[arisholm]

Anyone heard the nc2k amp? That must be able to drive any speaker out there with the not very limited 1600W/8ohm output! And with a dynamic range of 133dB... Fascinating to get that amount of clean power for about 2k per channel (apollon has one https://www.apollonaudio.com/hypex-nc2k-monoblock-amplifier-apollon-audio-nc2kslm/)... not that I really need it but...
Would be so interesting if @amirm would be able to test this class-D take-it-all-the-way-monster, but unfortunately I have none to ship over

 

[Xyrium]

Anyone heard the nc2k amp? That must be able to drive any speaker out there with the not very limited 1600W/8ohm output! And with a dynamic range of 133dB... Fascinating to get that amount of clean power for about 2k per channel (apollon has one https://www.apollonaudio.com/hypex-nc2k-monoblock-amplifier-apollon-audio-nc2kslm/)... not that I really need it but...
Would be so interesting if @amirm would be able to test this class-D take-it-all-the-way-monster, but unfortunately I have none to ship over

Those are "Hypex Watts", so it equates to about 100W/ch in Accuphase Watts.

I kid, I kid....