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Old 08-04-2013, 02:37 AM
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Originally Posted by MUDCAT45 View Post

Quote:
Originally Posted by GIEGAR View Post

False. Per above, my list shows power required for speaker dBSPL at 1 metre from the baffle. The calculator you linked is for power required for a desired dBSPL at a specified listening distance. The calculation also incorporates the full 6dBSPL of attenuation per double distance for outdoor applications and the option to add an allowance for amp headroom (important for live sound applications to account for unexpected performance peaks, but not totally necessary IMO when dealing with calibrated maximum SPL's in a home environment).
If you insert a 1m distance; 90dB/W/m sensitivity; 0dB headroom and a desired dBSPL, you will get the same results as my list. I suggest you read the explanatory notes with the calculator.

In your first post you gave required power at the listening position. That is the important location. I doubt one would use 683 at 1m. The required power at 4m using 86 db efficiency is 127 watts. This is a lot for a 125 watt AVR.

This is the first time I recall anyone claiming headroom to be unimportant. Both movies and music peaks can vary greatly in a home set up. Low headroom can choke an amp.

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Originally Posted by MUDCAT45 View Post

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Originally Posted by GIEGAR View Post

How did you calculate this? It's meaningless without knowing what desired SPL at the listening position it's for.
More paraphrasing to misrepresent me. I didn't "(claim) headroom to be unimportant". I said: "not totally necessary IMO when dealing with calibrated maximum SPL's in a home environment". There's subtle but important distinction. Music and movie peaks can vary greatly, but with digital media and delivery, and calibrated loudness levels, the amplitude of those peaks is entirely predictable.
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Originally Posted by GIEGAR View Post


Now, in typical residential rooms, sound pressure drops off at around 3 to 4dB each time you double the distance from the source (speaker). If I assume a longish 4m distance from your speakers to your LP and an average of 3.5dBSPL drop off per doubling of distance, you get a total drop off of 7dBSPL. This means that your B&W's will need to play at 102dBSPL at 1m distance to produce those 95dBSPL peaks at your LP.


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It seems as if you are on the defensive. I am not attempting to misrepresent you. You originally quoted a 95db at the LP. That is how I calculated the power requirement.

Is this what you calculated?

I attempted to explain why this calculator isn't totally appropriate here and here.

Quote:
... that the calculator you linked has the full -6dBSPL attenuation per double distance (inverse square rule) embedded. I didn't use it at the LP because my calculations already included an allowance (3.5dB per d/d). The reason I suggested inserting 1m distance is so it (inverse square rule) is taken out of the equation, to demonstrate it does give the same results as I listed. You just have to understand what each calculator is doing and use the correct one. I originally linked the calculator I did because all I wanted was a simple dB : power calculator to augment the power progression list.
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Old 08-06-2013, 02:33 PM
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Here's a great deal
http://www.sherbourn.com/products/pa7350
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Old 08-06-2013, 07:08 PM
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Here's a great deal
http://www.sherbourn.com/products/pa7350

And below is a full review of that amp.

http://www.hometheater.com/content/sherbourn-pt-7030-surround-processor-pa-7-350-amplifier
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