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Re: [TowerTalk] Tower and antenna decisions

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Tower and antenna decisions
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sat, 26 Oct 2013 23:17:30 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 10/26/2013 10:57 PM, Grant Saviers wrote:
You're the audio expert, but didn't Bob Carver figure out some clever variable supply voltage tricks with his big Sunfire amps? I have two and my "Signature" stereo is rated 2 to 16 ohms (1250w/ch 4 ohms) and runs stone cold even when delivering big power. No other amp I've tried had the headroom needed for my B&W 801Fs to generate max orchestral peaks at concert hall levels.

So isn't what you are suggesting been done before in the audio domain?

For at least four decades, solid state audio power amps have been contstant voltage sources with VERY low output Z (typically 0.1 ohms or less) , so the voltage is constant with load Z, and power out increases as load Z decreases (P=I squared R, or E squared /R))

There are good reasons for this -- the low output Z of the amp damps mechanical oscillation in the loudspeaker to clean up the sound (so that the bass isn't "floppy." The "damping factor" is the ratio of the nominal loudspeaker Z to the amp output Z (plus the resistance of the loudspeaker cable) . The loudspeaker Z is a a very complex function, with a dip in the midrange of each driver, rises above that point due to inductnace of the equivalent circuit, and at low frequencies, encounters resonances with the physical structure of the loudspeaker driver and addition resonances of the loudspeaker enclosure. In other words, it ain't simple. :) The nominal Z of a loudspeaker is the minimum value of Z in the midrange.

I am not familiar with Bob Carver's work, so cannot comment. Bob worked primarily in home systems, and I worked in pro systems.

73, Jim K9YC
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