Re: Best flagship A/V receiver? - Home Theater Forum and Systems - HomeTheaterShack.com

Old 06-07-14, 05:11 PM Thread Starter
Senior Shackster

Join Date: Dec 2012
Location: Lexington, VA, USA
Posts: 155

Quote:
GCG wrote: View Post
While I'm waiting on AJ I'll assume I don't have to reconnect my head and proceed.

We all know the 'double/half power = 3dB spl relationship. Increase or decrease power by a factor of 2 and you get a bump in spl of 3dB.

Let's set some conditions:

Speaker impedance: 8Ω
Speaker sensitivity: 80dB (low, I know)
System noise floor (including system and room contributions) 44dB spl - below this you can't tell the output of the speaker above the noise.

At 1 watt and 1 meter that speaker is producing 80dB spl - 36dB above the noise floor. To get down to the noise floor you'd need to reduce the power by half 12 times (12 x 3 = 36). That's 1/4096 watt or .244 milliwatts before you can't tell the speaker is producing any sound. Now add 18dB to the speaker sensitivity to bring you to 98dB and the power level at the noise floor goes to 3.8 MICROWATTS. That could very easily put you on a very dicey point on the back side of the THD/power curve.

Now during that very soft passage of your favorite string concerto the violin starts to sound less and less like a violin and more and more like something else.
You have a well thought out discussion. And given the THD curve displayed earlier, you make excellent points.

White with THD, less is better has always been the mantra. And it comes from the days when amps produced high levels of distortion. However, as time went on and levels of distortion dropped, the question became, when is it low enough? One study indicated that extremely low THD amps sounded bad due to the high levels of negative feedback used to achieve low THD.

There is no easy answer. Plus, it is important to understand that not all harmonic distortion is created equal. Even order harmonic distortion is not as noticeable. If fact, some people describe it as 'warm', as in 'tube sound'.

Here is one old study that indicates that with test tones we can just barely detect 0.15% distortion. But in musical situation, distortion is masked, a phenomenon that lossy storage like MP3 and AAC take advantage of.

http://www.stereophile.com/asweseeit/673awsi/

https://passlabs.com/articles/audio-...n-and-feedback
TheHammer is offline

 Bookmarks

 Tags a or v , flagship , receiver

Message:
Options

## Register Now

Random Question
Random Question #2

User Name:
OR

## Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.