Bob Somers wrote on Sun, 23 January 2011 21:22 |
I've seen all sorts of statements about what the lowest audible frequency by humans is and also, if there is a min SPL needed for it to be audible that is unusually high (such as 110dB, for example), please let me know what that value is. I would greatly value your observations on this from your own direct listening/measurements experience. Also, if there are any well regarded academic research sources relating to this, a pointer to them would be great. I have a second question. For a home living room, say dimensions approximately 15' X 15' X 8'(height), which subwoofer (including those now available and also those that have been discontinued) or subwoofer combination (and if more than one of these is needed, please say so) would cover 125Hz down to the lowest audible frequency at say, +/- 3dB all at whatever the max SPL level is that the human ear can tolerate without pain (this may be about 120dB, not sure and may vary with frequency) and with inaudible distortion or if that is not achievable, then with the lowest currently available. Of course, there are tradeoffs among the above criteria and I'm interested in your opinion on what equipment would give the most desirable results. Please include these in what you consider if you have knowledge of their performance: labsub, submersive, contrabass, basstech 7, whatever the current most potent model is of the Danley Tapped Horn design, Thigpen Rotary Woofer (a fan with variable pitch blades), Paradigm Sub 2, and a real oldie: the Bose Acoustic Cannon. Thank you very much!!! |
Bob Somers wrote on Tue, 25 January 2011 14:55 |
I've been doing more research on the Net and the Danley products certainly appear to be very potent. I wonder what it would be like if the DTS-10 drivers were driven by the servo motor arrangement (or similar) that had been used in the Contrabass? |
Art Welter wrote on Tue, 25 January 2011 17:47 | ||
Large advances have been made in conventional woofers linear excursion potential, the difference between conventional and servo drive speakers is not much with the present state of the art. Servo drive cones had around 16 MM Xmax, conventional cones of that time more like 4 or 5. Today, 16 mm Xmax is still quite respectable, but becoming more common in conventional sub woofers. Due to supply and demand, the price of servo motors is greater than it used to be, while high Xmax drivers costs have gone down. |
Alan Singfield wrote on Wed, 26 January 2011 12:17 |
http://www.rotarywoofer.com/ Just a suggestion. Edit: incorrect URL |
Don Gspann wrote on Wed, 26 January 2011 07:49 |
.... I'm sure the transient response is much better on the new subs,..... |
Tim Padrick wrote on Wed, 26 January 2011 23:10 | ||
Given the slow rise time of the frequencies that are fed to subwoofers, I think that the term "transient response" is not applicable. |
Art Welter wrote on Thu, 27 January 2011 11:07 | ||||
Transient response describes the behavior of a system following a sudden change in its input. It is not limited to high frequencies. Many sub designs suffer from the persistence of cone movement or stored energy in the system after the signal has stopped, underdamped transient response. Listening with two systems equalized for identical response, a sub with poor transient response, as described above, will subjectively sound “tubby” or “slow”. Percussive notes tend to blend together, bass lines become less recognizable. I hate it when that happens . |
Tim Padrick wrote on Sat, 29 January 2011 01:38 | ||||||
My thinking is that the term transient response describes the DUT's performance on the leading edge only - that anything that happens after the peak is reached has to be described by another term. No? |
Art Welter wrote on Sat, 29 January 2011 14:01 |
McGraw-Hill Science & Technology Dictionary defines Transient Response as: “The behavior of a system following a sudden change in its input.” Wikipedia: “In Electrical Engineering and Mechanical Engineering, a transient response or natural response is the response of a system to a change from equilibrium. Specifically, transient response in Mechanical Engineering is the portion of the response that approaches zero after a sufficiently long time (i.e., as t approaches infinity). “ But even looking at the transient response at the start of a signal, there are differences that can be observed between woofers. A 10” woofer with a powerful magnet can accelerate a light cone faster at the onset of a signal than an 18” heavy cone woofer with a weak magnet. The former would have better transient response than the latter. |
Mac Kerr wrote on Sat, 29 January 2011 12:25 | ||
Of course, there are no sudden changes in input in a sub. All changes are gradual because of the LPF eliminating those pesky rapid changes. Obviously there can be mechanical systems that are so slow in response that even a relatively slow change to the input of the system can't be accurately tracked by the output. Since it is a case of the output not tracking the input I suppose that could be thought of as transient response. It isn't transient response in the sense that that term has in any other part of the system. Mac |
Art Welter wrote on Sat, 29 January 2011 15:18 |
100 "changes" a second is not sudden? Of course, that 100 changes would be only the upper fundamental frequency, when a woofer is responding to a musical signal, there are multiple frequencies involved, the "changes" it needs to respond to are in the thousands. When are changes sudden, at 1000, 10,000 Hz ? How does transient response apply to one set of frequencies and not to another? |
Mac Kerr wrote on Sat, 29 January 2011 14:17 | ||
Yes, the changes it needs to respond to are in the thousands, but all of them are below about 100Hz. In a sub, maybe an impulse with a 2.5ms 1/4 wave rise time or greater can be called "transient". What often gets mentioned in discussions about sub "transient response" in subs is the first snap of the beater on the bass drum. It you compare the rise time of that first impulse as heard by the mic to the signal as heard by the sub, the signal at the sub won't look so much like a "transient". If the "snap" of a bass drum is around 4kHz it has a rise time 1/40th of that of 100Hz, or 0.0625ms. If "transient response" is the ability of the output to track the input, there is no lower limit to what a transient is, it is defined by the mechanical system's ability to track the input. If a "transient event" is defined by the frequency content of the original full range source, what happens at the sub is slow motion. Mac |
Don Gspann wrote on Wed, 26 January 2011 07:49 |
... but I do have 2 ContraBass subs in my living room. I'm sure the transient response is much better on the new subs, but for the size and weight and the sheer wall/floor shaking, knick-nak knocking off shelves enjoyment, I'm not giving them up anytime soon! A Telarc/DTS disc that has a recording of a space shuttle launch is too much fun to play for people. At first, all your you hear is the windows rattling, and feel the house shaking! Love them! |
Bob Somers wrote on Thu, 03 February 2011 12:22 |
It seems to me there is no such thing as transient response and that what is incorrectly called transient response is really included within the definition of distortion. Please give me your thoughts about my views on this. Thanks, Audioresearch |
Bob Somers wrote on Wed, 02 March 2011 15:48 |
It just seems to my eye (just an educated guess not based on any measurements) from photos I've seen that the external servo motor Danley used is a much, much larger motor than what could fit into the "motor" portion of a conventional voice coil speaker and I would think that a cone driven properly by such an external motor would be likely to move a lot more air than a conventional voice coil driver with the same cone area because of what appears to be the much larger power that a big external motor could provide. If I'm wrong about that, and I may be, which off the shelf woofers now available could equal or exceed or at least come very close to the displacement volume of the Danley-type external motor with attached cone that was used in, say, the Contrabass? |