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Understanding Amplifier Measurements (Video)

D

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Others have provided links. Here is my standard answer:

Power Needs:

For many years I have used 17 dB peak-to-average power based on an old AES article I can no longer find. Anecdotally various audio fora report 20 dB or more for movies. IME most people use much less average power than they think, but require more peak power. An online calculator can help you estimate your average power; note 80 dB is very loud to me (YMMV). Here is one:


Most people think of volume in dB and most modern AVR/AVP/etc. units list dB on the volume knob. Power in dB goes as 10log10(Power_ratio) so the change in power is 10^(dB/10). Here are some reference numbers in dB and power:

1 dB is barely noticeable and requires 1.26x the power
3 dB is what most people hear as "a little louder" and requires 2x the power
6 dB is significantly louder and requires 4x the power
10 dB sounds twice as loud and requires 10x the power
17 dB is the headroom for music and requires 50x the average power
20 dB for movies requires 100x the power

If you listen at around 1 W average, then you need 50~100 W to avoid clipping on most source material. You can figure out your estimated average power from the calculator knowing your speaker's sensitivity and distance from them. Note music may be more compressed and thus require less headroom, and the loudest sounds in movies tend to be things like gun shots and explosions where a little clipping is likely unnoticeable.

HTH - Don
Exactly. Most people are somehow convinced that they don't need much power but that is only true in a desktop near field setup and with "girl & guitar" music.

I bet my left testicle (already got two kids, no big loss) that many people with speakers in room are actually clipping their amps regularly without noticing.

Seems the calculator checks out and I have just about the power I need to go deaf or burn coils. Whatever happens first.

1682655335750.png
 

Spocko

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Headroom question - does someone have a link for me to understand this issue? Does headroom matter if I am at a desk and never roll the power more than 50%? Thanks!
Also, beyond headroom, keep in mind the amp's ability to drive low ohm difficult speaker loads like some ribbon speakers and more exotic ones (2 ohm loads on MBL speakers) and so sometimes the amplifier headroom is less about SPLs and more about its ability to "drive any speaker" you throw at it. This is why I prefer active speakers, letting the manufacturer put in the best amp for its intended uses.
 

RichB

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Here is an analysis performed by measuring dual mono 0dBFS sine waves (200Hz, 1kHz, and 2kHz) from my listening position.
My ceiling is slanted from 8 to 12 feet. The measurements are taken at my 11 foot seating position in a 30 foot room.

A volt meter was used to set the level at the speaker (while playing) to 2.83 volts.
Since the Salon2s are basically 4 ohms speakers, this computes to 2 watts (from the AHB2s).
The AHB2s produce roughly 180 WPC into 4 ohms, so these amps can produce about 106 dB (using two speakers).
Measured SPL at Listening Position.jpg


The Peak SPL Calculator can reflect a similar result when selecting in corner placement, though the Salon2s are not jammed into the corner.
Salon2BenchmarkSPLEstimate.jpg


The problem with some with this type of analysis is that with a couple of incorrect assumptions, it is possible to overestimate power requirements by 2X, 4X, even 8X.

The computed levels have been corroborated using the AHB2 clip indicators.
I also bi-amp that is yielding 1 to 2 dB of headroom, observationally using the clipping meters.

I am not sure why, but since I now use a DAC3/LA4 for 2-channel, the system seems louder.
It is certainly far louder than I like for music and movies. Of course with movies, there are a lot of channels firing, including 2 Rytmik E22 subwoofers.

System1.jpg




- Rich
 
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amirm

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Is ASR running low on product to review? :)
If I stop accepting new gear to test, I will have work for months left! I am doing videos to use as preference for reviews so that people understand them. I need to finish the round for all category of devices.

Also, many people on youtube will not read ASR. So I need to serve that audience as well.
 

CtheArgie

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@RichB , I am stunned, flabbergasted, extraordinarily dissapointed, believe me, never seen his kind of disappointment. Your wires are on the floor! Not elevated.

Poor old soul, god bless his heart.
 

amper42

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If I stop accepting new gear to test, I will have work for months left! I am doing videos to use as preference for reviews so that people understand them. I need to finish the round for all category of devices.

Also, many people on youtube will not read ASR. So I need to serve that audience as well.

For me a YouTube video over 15 minutes is way too long - especially without segments. I wonder how many users completely watch a 50min informational video on YouTube? That would be interesting data. To each his own.
 

khensu

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If I stop accepting new gear to test, I will have work for months left! I am doing videos to use as preference for reviews so that people understand them. I need to finish the round for all category of devices.

Also, many people on youtube will not read ASR. So I need to serve that audience as well.
Don't get me wrong. I'm not complaining. I totally appreciate everything you're doing. I might suggest, though, that you amend the "send me your stuff to measure" page as it implies your turnaround time is quite a bit shorter (which I'm sure was true when you wrote it)
 
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amirm

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For me a YouTube video over 15 minutes is way too long - especially without segments. I wonder how many users completely watch a 50min informational video on YouTube? That would be interesting data. To each his own.
You don't need to wonder. Just read the comments under the videos which are universally positive and people say they don't mind the length at all. Reason is that they are getting a lot out of the video. Keep in mind that the same video in text would be dozens of pages. If you can't be bothered to watch a 15 minute, you sure as heck not going to read such a bible either.

Regardless, I am doing the work, not you.
 
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amirm

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Don't get me wrong. I'm not complaining. I totally appreciate everything you're doing. I might suggest, though, that you amend the "send me your stuff to measure" page as it implies your turnaround time is quite a bit shorter (which I'm sure was true when you wrote it)
I should update that page. For now, I let everyone know the lead time when they first contact me.
 

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For me a YouTube video over 15 minutes is way too long - especially without segments. I wonder how many users completely watch a 50min informational video on YouTube? That would be interesting data. To each his own.
I love long form videos. There's WAY too much stuff these days pandering to people with no attention span.
 

xaxxon

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You don't need to wonder. Just read the comments under the videos which are universally positive and people say they don't mind the length at all. Reason is that they are getting a lot out of the video. Keep in mind that the same video in text would be dozens of pages. If you can't be bothered to watch a 15 minute, you sure as heck not going to read such a bible either.

Regardless, I am doing the work, not you.
Please keep making videos exactly as long as they need to be to convey the information. I really appreciate videos being as long as they need to be and no longer or shorter to meet arbitrary requirements.
 

fcracer

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For me a YouTube video over 15 minutes is way too long - especially without segments. I wonder how many users completely watch a 50min informational video on YouTube? That would be interesting data. To each his own.
People use YouTube in different ways these days. YouTube Premium completely changes the experience for me. I download episodes like Amir's and then watch them on the planes I often find myself on. This completely melts the time away on flights and I learn something too. The one thing stops most people from watching longer videos is the ads, but with YouTube Premium, it's a total game changer.
 

DanielT

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Amazing videos that you have been releasing recently!

If we can't reliably trust the manufacturers reported power output for amps nor can we trust the manufacturers reported speaker sensitivity (let alone impedance) is there a rough rule of thumb now much reported "power" to look for in an amp?

I am thinking about a general livingroom or home theater where listening distances would be 8-10ft and wanting reasonable levels / headroom for dynamic range.

I found this: https://www.crownaudio.com/en-US/tools/calculators#amp_power_required
but don't know if people have other suggestions or rules of thumb.

Thanks again for the amazing videos!

Exactly. Most people are somehow convinced that they don't need much power but that is only true in a desktop near field setup and with "girl & guitar" music.

I bet my left testicle (already got two kids, no big loss) that many people with speakers in room are actually clipping their amps regularly without noticing.

Seems the calculator checks out and I have just about the power I need to go deaf or burn coils. Whatever happens first.

View attachment 281943
First, I just want to thank Amir for the video!:)

All calculators have listening distance as a parameter, then this may be worth taking into account:

Distance and sound pressure level in rooms is a very misunderstood area. In a normal listening room, the listener is placed in the so-called the reverberation field, where the room contributions dominate over the direct sound contribution. This means that the listening distance has little significance for the sound pressure level at distances above about two meters (6.56 ft)

Exactly how it all turns out depends on the speaker's directional index, the room's equivalent absorption area and to a lesser extent on the distance,....



This is something you easily notice if you walk around your listening room. Then set up a pair of speakers outside and move away from them. Big difference in sound pressure and listening distance then.:)
 
D

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People use YouTube in different ways these days. YouTube Premium completely changes the experience for me. I download episodes like Amir's and then watch them on the planes I often find myself on. This completely melts the time away on flights and I learn something too. The one thing stops most people from watching longer videos is the ads, but with YouTube Premium, it's a total game changer.
Adblock!
 

RichB

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@RichB , I am stunned, flabbergasted, extraordinarily dissapointed, believe me, never seen his kind of disappointment. Your wires are on the floor! Not elevated.

Poor old soul, god bless his heart.

My cables identify as being elevated.
However, the rear Salon2s use in-wall so there is not hope for them.

- Rich
 

Rottmannash

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Rottmannash

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Here is an analysis performed by measuring dual mono 0dBFS sine waves (20Hz, 1kHz, and 2kHz) from my listening position.
My ceiling is slanted from 8 to 12 feet. The measurements are taken at my 11 foot seating position in a 30 foot room.

A volt meter was used to set the level at the speaker (while playing) to 2.83 volts.
Since the Salon2s are basically 4 ohms speakers, this computes to 2 watts (from the AHB2s.
The AHB2s produce roughly 180 WPC into 4 ohms, so these amps can produce about 106 dB (using two speakers).
View attachment 282144

The Peak SPL Calculator can reflect a similar result when selecting in corner placement, though the Salon2s are not jammed into the corner.
View attachment 282145

The problem with some with this type of analysis is that with a couple of incorrect assumptions, it is possible to overestimate power requirements by 2X, 4X, even 8X.

The computed levels have been corroborated using the AHB2 clip indicators.
I also bi-amp that is yielding 1 to 2 dB of headroom, observationally using the clipping meters.

I am not sure why, but since I now use a DAC3/LA4 for 2-channel, the system seems louder.
It is certainly far louder than I like for music and movies. Of course with movies, there are a lot of channels firing, including 2 Rytmik E22 subwoofers.

View attachment 282154



- Rich
Love that set-up but really want to know where you sourced that cabinet. Am I seeing 4 AHB2's?
 

Rottmannash

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I should update that page. For now, I let everyone know the lead time when they first contact me.
Which is? I have a DAP I've been thinking about sending for review but...
 

RichB

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Love that set-up but really want to know where you sourced that cabinet. Am I seeing 4 AHB2's?
I had it custom made by the guy who made my kitchen cabinets.
That is the 83" LG OLED. Any bigger, and it will have to be reworked or replaced.
If the 97" OLED hits 10K or below, I'm one it :)

3 AHB2s bi-amp the FL, FR, and center channel. I thought I might need to bridge but I don't run out of power so I don't bother.
The Salon2 rears are powered by a single AHB2.

I moved from 2 ATI6002s and a AT6006, needless to say, technology has advanced and less components are required.
The core components are the RMC-1, Oppo 205, DAC2, LA4, AHB2s, and Raspberry Pi4 for Roon.
A NUC runs Roon in the basement.

I could downsize the cabinet at any time. It might be cheaper to build a new one.
It has hidden wheels, that are an absolute must for the serial upgrader.
Credenza style cabinets create a cable nightmare.

- Rich
 
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