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Need speakers that can rock with just one watt? You found da place.

What can you do with less than 1 Watt?




OK, so keep my Avatar in mind when your read this. I have a separate amp for my bass bin, getting the receivers pre-outs because I need about an extra 5 db of gain in the FH-1 with K33's vs. the top section driven by my AV receiver amp (K402/K1133 with QSC/DE-250).

Also need a certain amount more gain in my Tapped Horn sub with the amazing LAB 12 woofer. Because my receiver sets up the relative gains against an 85 db industry standards when it measure at my sweet spot, all this is taken into account by setting the levels there

Because the average and dynamic levels of CD's, DVD's and Blue Rays are all over the place, the only to maintain a stable level (so I don't piss off my neighbors) is to use a db meter before a music or movie session.

My system setup auto detects my source in the Panasonic Blue Ray player and sets up for 2.1 or 5.1 by itself. The majority of my time is spent listening to 2.1, hence the post here. The typical setting on my somewhat obsolete Onkyo AVR typically ranges from -20 db to -30 db setting on the level control (Right and Left channel are set to -12 db internally after Audyssey calibration, for a total of -32 to -42 db nominal against the receiver's supposedly full output, not including whatever "headroom" they put in there). Setting up some Jazz music at about 77-85 Decibels average at my sweet spot on the couch, (slow C curve on my Radio Shack DB meter).

I whipped out my digital voltmeter and measured at the speaker terminals of each section on the Right channel, plus the sub. I knew I was using very little power before I began, but now I can put real numbers to it. I had a Jazz CD with heavy electric bass content, so I set the average level to 3 tracks total to my usual level of satisfaction, which is usually -23 db setting on my receiver (Right and Left channel are set to -12 db internally after Audyssey calibration, for a total of -35 db nominal).

I went to the track that is the loudest on there with the most bass and did my measuring. I'm not sure about the response time of the meter, but I looked for the highest voltage value detected and rounded up. At the Xover terminals (feeding the two top horns' capacitors, I got 1.5 volts on the sub's LAB12 terminals, 0.36 volts on the FH-1, and 0.28 volts on the treble section. The are the highest readings and most of the time they were less than this

So the mono sub's, which has it's own amp fed from the "sub out" on my receiver, and set to -6 db internally by Audyssey, according to ohm's law ( Voltage squared over average impedance of 6 ohms) yields 2.25/6 ohms=0.26 watts (about 1/4 watt of power).

Similarly, the 5.6 ohm K-33 needs 0.130/5.6ohms=0.023 watts (23 milliwatts), and the treble section is .078/8 ohms=0.010W (10 milliwatts).

Paul W Klipsch told me to add 17 db headroom, which he measured from his own live symphony recordings. If we double that amount, and round up to a plus 20 dB headroom, we need 100 times the power to achieve it. This means my receiver will most likely never put out more than 1 W on the highest peaks in my 15x18 foot room with 7 foot drop ceiling on the K1133/DE-250 compresson drivers (since it's 100W/channel, I still have another 20dB headroom on top of it, it can NEVER clip).

The K33 will see a peak of 2.3 watts, and the LAB 12 will see 26 watts peak from a 200 watt per channel amp, with only 1 channel used. Even if you add another 10 db (yet another 10X more power) that may be needed for the +10db in the LFE channel from movies (requiring 1,000 X more power than my measurements), it would mean a 260 Watt peak requirement.

You can see that in an all-horn system, the subwoofer channel potentially needs all the power and the rest can be driven by flea powered amplifiers.

How many guys that have Tuba HT's that do a 20 Hz sine wave test at 10 Volts are flexing their drywall and windows? Now you know why large format horns ALL have ridiculously low distortion and wide dynamics. The voice coils never heat up and behave in a high distortion, non-linear manner from thermal compression. Comments invited.
Claude
5.1/2.1 wall of sound Stacks: Front L&R=LaScala Type Bass (Peavey FH1 with K-33 woofers), Klipsch K-402/K1133 drivers, B&C DE250/QSC Horn Tweeters, Front& Center=Cornwall I, L&R Sides=KPT-200's, 18 foot long folded Tapped Horn "coffee table sub with LAB12 B&W amp, all Driven by an Onkyo 706 Receiver, Hats off to Tom Holman and Audyssey EQ!!




Edits: 05/09/12 05/09/12

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Topic - What can you do with less than 1 Watt? - claudej1@aol.com 08:25:43 05/09/12 (13)

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