Same answers as Dec 11 when you last posted the question.
Excursion is measured in Xmax (linear excursion) and Xlim or Xmech (excursion which will cause damage or noises).
Having more excursion capability allows any design to produce more low frequency output.
Perhaps you could rephrase your questions, "E max", "tear cones", "more tail" don't translate well .
The TH-50 and the Gjallerhorn
Both feature very long excursion drivers and work well.
rafaro
Yes large Xmax drivers with 3 to 5 inch excursion in tapped horns. Question is with such large air movement could problems with cones ripping arise. Would they need more front air space to cushion this? It can be in the form of adding a front chamber or increasing what danley calls the tail which is the apical segment of the horn which helps to smooth out the rippled freq response. Seems we will be seeing these kind of high Emax drivers with low distortion coming out soon.
Yes large Xmax drivers with 3 to 5 inch excursion in tapped horns. Question is with such large air movement could problems with cones ripping arise. Would they need more front air space to cushion this? It can be in the form of adding a front chamber or increasing what danley calls the tail which is the apical segment of the horn which helps to smooth out the rippled freq response. Seems we will be seeing these kind of high Emax drivers with low distortion coming out soon.
A TH is capable of about 6 dB more output than a ported cabinet, which does put more stress on the cone than a BR operated at the same power level.
So far, I have not heard of cone failures of drivers operated within Xmax in TH.
The LMS Ultra 5400 18” driver used in Josh Ricci’s Gjallerhorn has a 38.1mm Xmax (just over 3” peak to peak), it has survived some serious excursion in testing. The Gjallerhorn has a fairly standard compression ratio.
http://www.diyaudio.com/forums/subwoofers/189784-gjallerhorn.html
Although there are drivers that may have (or will have) more excursion than the LMS Ultra 5400, higher excursion requires a big surround suspension roll which reduces effective SD, and huge expensive heavy magnet and coil structures, a set of diminishing returns, ever so much more money for tiny incremental increases.
If you design a TH with its 1/3WL (lowest system efficiency peak/system resonance) and the -3dB (in response) above the Fs of the driver, they do not exceed their maximum physical excursion and can be powered by the AES power ratings from their specs. In other words, designing that way gives similar excursion behaviour to basreflex but with an 3dB to 6dB higher output like Art already explained. When you force the driver to play below its Fs, which is possible with a TH, the excursion will rise and the max power drops. The sensitivity will also drop but can be (partly) made up by increasing the horn size.
As you will find out soon all these single magnetic gap drivers will be obsolete soon
To be replaced by with Push Pull double voice coil technology with quadruple power output compared to same size driver with single magnetic gap. Excursion will be massive!!! And they will be inexpensive and not too heavy. Salivating yet!!!
To be replaced by with Push Pull double voice coil technology with quadruple power output compared to same size driver with single magnetic gap. Excursion will be massive!!! And they will be inexpensive and not too heavy. Salivating yet!!!
Unless excursion is doubled, a six dB increase will not be seen (heard) regardless of how many voice coils are driving the cone.
Doubling excursion requires a much larger surround area, reducing Sd, which then reaches a point of diminishing returns.
I won't be salivating or holding my breath or anticipating the obsolescence of single magnetic gap driver technology, any more than I did with the introduction of servo-motor or rotary fan driven woofers.
Art
power output= air volume X velocity square (I believe)
Therefore if you double excursion and double air volume you get twice the power out but if you double the air velocity you can potentially quadruple power output. The force on the VC is F=BLI where F= force ,B= magnetic flux,L= VC length active in the magnetic flux, I= input current. The Double VC doubles L the double magnetic gap also increases B you do the math
If you can increase both velocity annd excursion the sky is potentially the limit. Preliminary designs show 5X greater excursion and double velocity!! Additionally the larger surround is also involved in moving air more so and with more velocity than the same equivalent cone area!!!!!
Salivating yet??
Your contrasting replies apreciated!!
Therefore if you double excursion and double air volume you get twice the power out but if you double the air velocity you can potentially quadruple power output. The force on the VC is F=BLI where F= force ,B= magnetic flux,L= VC length active in the magnetic flux, I= input current. The Double VC doubles L the double magnetic gap also increases B you do the math
If you can increase both velocity annd excursion the sky is potentially the limit. Preliminary designs show 5X greater excursion and double velocity!! Additionally the larger surround is also involved in moving air more so and with more velocity than the same equivalent cone area!!!!!
Salivating yet??
Your contrasting replies apreciated!!
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Not quite, there are diminishing returns on excursion vs cone area. The area of air that couples to the driver surface gets smaller the higher the velocity gets. You may have the same mathematical displacement but air adds a thing called friction which dosen't like velocity. A large driver moving relatively slowly will make more sound than a small driver going like mad given that they both have the same mathematical displacement.
Cordially,
revb.
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I see high excursion hi velocity drivers most usable in horns
Seems hi velocity hi excursion benefits will be lost in the inefficiency of direct radiators. Even supposing can put out 2-4 excursion/velocity power transfer will barely show it. But in horns these drivers will be interesting they almost seem to act like compression drivers with high power pressure waves which horns will convert to large volume air movement. Thanks for the info on losing functional cone area with hi velocity. Presently working on a patent to enable common electrodynamic drivers to have hi excursion easily.
Seems hi velocity hi excursion benefits will be lost in the inefficiency of direct radiators. Even supposing can put out 2-4 excursion/velocity power transfer will barely show it. But in horns these drivers will be interesting they almost seem to act like compression drivers with high power pressure waves which horns will convert to large volume air movement. Thanks for the info on losing functional cone area with hi velocity. Presently working on a patent to enable common electrodynamic drivers to have hi excursion easily.
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