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High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
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In Reply to: Re: Whats the low-frequency slope of BASSMAXX One's? posted by Tom Dawson on August 25, 2003 at 12:10:45:
Hi TomIt’s a good thing Ham’s and others didn’t know it was “impossible†to make them as they (passive hilbert transforms) have been used for ages in producing SSB conversion in radio communication as well as being in the TEF 10, TEF 12 and TEF 12+ (while the TEF 20 is in software) for generating the quadrature test signal.
If you have a friend with Japan Radio 535 or TEF machine, you can see the schematic for one.So far as what a simple case driver (acoustically small, flat response, piston behavior) does, one has to choose what the books say or what the mfr's say.
If one buys into the mass controlled acceleration response to offset the changing radiation resistance, well then one has to buy the 90 degree shift thing.
Similarly, if one carefully measures a real low frequency driver with a suitable test (TDS) one also finds the phase shift.
Alternately, should one try to pass a specific signal for a waveshape critical application like active sound cancellation, well then one also finds the phase shift IS the main reason one can’t just use a microphone and invert the signal.
The speaker DOES NOT preserve the waveshape and so an adaptive algorithm is used instead (which does not work well on random noise cancelation).Understand too that a small acoustic point source like a woofer and a bass horn with the same frequency response will have a very different acoustic phase response because the horn is resistance controlled and the direct radiator is reactance controlled.
If one has a “perfect†example of each, the acoustic phase would be 90 degrees different from each other with the horn being at zero degree and direct radiator at ~ -90.
On the other hand, I have been able to find a room location and frequency where speakers that didn’t even sound good, made a decent square wave.
For a manufacturer to come out and say that “fundamentally our speaker cannot preserve a signal’s wave shape†would not sell many speakers.
Rather the argument made by speaker companies is that phase shifts and non zero phase are largely inaudible.Having heard many systems getting closer to ideal, I would have to say it is the other way around, that to a significant degree it IS the “time problems†and driver location issues which makes speakers sound more like a recording and less like the real thing.
These time problems occur AT the location of the speakers and your ear can identify then spatially (location and depth).
Eliminate the time issues to the point where one can preserve waveshape over a significant bandwidth and it makes a BIG difference in clarity and makes it much more difficult to tell how far away the speaker is or even where it is in a good stereo recording.
I have heard countless old recordings come alive, hearing stuff I could never make out previously and some good recording sound phenomenal with amazing depth of image.Tom, if are you in the midwest or near Chicago, I can demonstrate something I am working on related to all this, bring your best test recordings.
Cheers,Tom Danley
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Follow Ups
- Re: Whats the low-frequency slope of BASSMAXX One's? - tomservo 08/25/0317:13:06 08/25/03 (0)
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