Axiom Home Page Forums General Discussion Technical Questions Any science behind claim swfrs reducing loads on mains?

I don't think time-corrected has anything to do with doppler shift, but just the phase and "alignment" of the sound waves as they reach your ear.

Vandersteen speakers, for example, achieve time-alignment by mounting the different drivers not in a vertical plane, but slighly staggered from one another. Thiel accomplishes this by having the speaker baffle angled backward. All are still subject to this doppler shift.

On the other hand, anything that creates sound is subject to doppler shift, is it not? Take the violin for example. Vibration is created as the resined horse hair is dragged across the strings. The vibration is transmitted to the sounding board through the bridge, and then to the entire body. The vibrations are similar to -- though much more complex than -- a speaker cone in that surface of the violin oscillates back and forth.

I sometimes wonder if I really know that much less about all this stuff then some of you or if you're all just talking out your a** with some of these posts.

I guess I just have a lot of catching up to do with some of the finer details of speakers and how they work...or just get what I can out of threads like this(a good chunk of it made sense) and ignore the rest!

I don't know that it would be much more complex; after all, the speaker is reproducing those vibrations by vibrating itself. Therefore, a speaker playing violin music (a good speaker, mind you) would have to vibrate in a very complex way to even approximate the sound of the violin.

And yes, I am talking out of my ass. :-)

Hey, now. When I talk out of my a**, I usually try to make it transparent enough that it wouldn't fool anybody. Granted, I'm an acoustic engineer, but what I said above has at least a moderate grounding in reality.

No, you're not an acoustical engineer.

Hi all,

Thanks for the feedback and kind wishes re my trip to LV. pmbuko is right; Doppler stuff isn't related to the time-alignment of drivers.

The Doppler distortion results when a woofer cone is moving outward to reproduce, for example, a 40-Hz tone at the same time that it's reproducing a 100-Hz tone. The 40-Hz movement would add Doppler components (pitch shift?) to the 100-Hz tone. Is it audible? Does anyone care? Don't know; will quizz colleagues at CES.

In fact, it still amazes me that a woofer can reproduce two or more frequencies simultaneously with reasonable fidelity. Think about it: the cone is vibrating at 40 cycles per second at the same time that it's vibrating at 100 times per second. Huh? You'd think the results would be total grunge, not music.

Regards,

Hi Chess,

I forgot to say that to interpret those THD charts, you subtract the number of dB between the SPL level at the top (usually around 90 dB SPL) and the distortion curve at the bottom. So if there is 40 dB difference, or, to put it differently, if the THD curve at the bottom is 40 dB down from the upper curves, the distortion is 1% or less. If the distortion is just 20 dB below the test level, then the distortion is 10%.

As to midrange audibility, if you keep THD at 1% or less, it's generally inaudible with musical programs but audible with a fixed tone.

With music, THD distortion usually has to get well into the whole percentages to become audible or annoying. And this is even-order harmonic distortion, which is "musical" in a sense, nothing like as nasty as odd-order distortion that you can get from amplifiers.

Regards,

Alan, sounds like you're a closet fan of tube amps!

In reply to:

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In fact, it still amazes me that a woofer can reproduce two or more frequencies simultaneously with reasonable fidelity.

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The same thing I realized when I first started with digital audio theory on the C64 (wow, 40K of BASIC memory, with more under ROM? I can have an 8 second digital audio clip at 4000 samples per second, 4 bit resolution, holy cow!

The first time it occured to me that a 50-50 mix of two digital audio streams is a mathematical average of the two:
x=(a+b)/2
... it blew my mind... mix in 8 different signals and you should get mud, not a fine audio signal! Made me interested enough that I built a quick and dirty audio digitizer around a 0820 ADC, worked very well except the source had to be a DC walkman or similar (since I didn't build in any sort of ground isolation, it would hum like a bugger otherwise)

Bren R.

Doppler shift . Clearly, those audiophiles desiring to experience true purity of sound(at least those who hear differences in interconnects and speaker wires)would be required to use an individual speaker for each separate frequency up to at least 20,000Hz in order to avoid intermodulation effects; of course the wave form distortion of each individual frequency caused by driver excursions might still leave them unfulfilled, although a step closer to nirvana.