You actually have measured that LCR trap does the same thing? Just showing the LCR smooths the impedance means it prevents feedback into the amp.
Customers ask for this data, yes, but I am not sure that the use of a Klippel system has improved or even changed any of the B&C drivers that I use in any way. But we certainly agree that the whole discussion is academic anyways.
Agree - plus some lovely beat due to time of flight from one diaphragm to the next.
Michael
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Hi John, had trouble following any of the rest. What is the intent of an LRC that nulls out the drivers resonance? Won't this just raise the Qt of the driver? Why is that a good thing?
And to fntn, in any system, if the Q of the resonance is below "critical", i.e. .71 then there is no "stored energy" at resonance. That's what "critically damped" means. And there is no evidence that stored energy in a LF loudspeaker in a real room with a multitude of modes that do have "stored energy" is an issue at all. Seems to me that the details of the resonance of any woofer is darn near irrelavent in light of the fact that it is placed, and couples to, a system that completely dominates the situation, namely the room.
Possibly this is so as you do not listen close enough for more subtle details to value changes in presentation there ?
Michael
John, the isobaric is more compact. The other reason is that when i mount the bass driver magnet up then there is some increase in second harmonic because the cone is driven slightly out of the gap ( not totally out of the gap of cause, only a certain way ) by its mass. The internal driver is mounted magnet down ( driving into the gap ) and reversed in phase so i have push-pull drive hopefully compensating somewhat the distortion that only a single woofer whould have. Migeo, i know that there are problems in an isobaric system when the two cones are not extremely close together. I experimented many years ago with this and found that i could improve the situation when i fill up the hollow cave that exists between the cones. I made it work and t sounded great. If the isobaric fails miserably i will try something else. Sorry that i am not fast enough with physical construction to prove my point in praxis but you are all very quick minds here. Thanks for contributing even if this road is a bit rough at times.
I thought that we agreed that this was academic? Now its a major design criteria to balance 2nd order nonlinearities? You realize that balancing a 2nd order nonlinearity with another one in reverse does so by raising odd order nonlinearities? In essence the 2nd - inaudible one - is lowered by raising the more audible third order or higher odd order ones.
I just do not get this obsession with nonlinearity - must be Klippel. I have studied this whole area intensely and short of using a good shorting ring in a wideband LF driver there is nothing to be gained from pursuing nonlinearities. Looking back, I regret having spent so much time studying this as it was a waste of time.
It essentially wipes out energy available to excite resonance in the driver altogether. If Fs is not part of your passband - it's an acceptable method. Obviously, it's acceptable because it has produced satisfactory results on a widespread basis in the industry.
If tightly controlled low distortion response is required through resonance, the t-line is superior because it manages energy storage better than most other alignments - the resulting impedance curve is the obvious report card for performance on that basis. "Feedback to the amp" or electrical damping from the amp's low impedance has nothing to do with it because the driver's response is not based on current flowing through the voice coil - it's based on mechanical storage of energy. In fact, the high resistance shown by the voice coil at resonance indicates that it is not possible for current to become a factor. Only when excess mechanical energy stored in the driver's suspension and moving mass is absorbed, can the amplifier regain its ability to control or modulate the moving mass. The heavy reduction in impedance across the entire resonance band with t-lines demonstrates this phenomenon.
A shunt is good from the point of view that it helps the crossover filter design in that the impedance it sees around the driver resonance is flatter and tends towars pure resistance. But the down side of it, or any netwrkrok between the driver and amp is that the driver may see a different load when acting as a generator and therefore have a different Qts.
Not saying that is good, just what happens.
In the good old days we just used to place a resistor across the driver if necessary. Wastes power but it's just as effective and a lor cheaper than a large inductor and cap.
LOL
but fast learning guaranteed too
Wrong put again - too much smoke over there in Essex ??? - its not exactly a matter of close mounting.
The Linn Sara had veeery close mounting of their B200 - did not help any. Same for stuffing - *if* you would be able to prevent interaction - what good would it be for to use two chassis at all...
But people are different sensible for such things I admit - just read Earls recent comment for prove.
Michael
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Well, being more compact depends on what woofers you use. Distortion, I would not count on it being all that beneficial.
An externally hosted image should be here but it was not working when we last tested it.
More at Isobaric
Is that really what it means professor?
Q factor - Wikipedia, the free encyclopedia
Because in the school I went to, they taught that Q is proportional to energy stored divided by energy dissipated per cycle as shown clearly in the link above. That would mean that there is "energy stored" at resonance unless the system Q is 0. Maybe that's the Q of systems you work with. It isn't the Q of anything I've ever worked with.
BTW, critical damping is a Q of .5. A Q of .707 is not critical damping - it is optimized for bandwidth.
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While almost all of the statements were incorrect, this one is a hallmark of misinformation.
Joachim, fwiw, the absolute best implementation I've heard for the isobaric was a variation on the old Dynaudio DA500. Inner and out drivers were different, the chamber between inner and outer was significant, the inner fired through a variovent, and the drivers were perpendicular to one another. From the subjective standpoint of bass clarity, I have never heard anything better. I was particularly impressed by the reproduction of the fist knocks on the top of an acoustic guitar on an old Sheffield recording (I find that track very revealing of midbass issues).
Is that really what it means professor?
Q factor - Wikipedia, the free encyclopedia
Because in the school I went to, they taught that Q is proportional to energy stored divided by energy dissipated per cycle as shown clearly in the link above. That would mean that there is "energy stored" at resonance unless the system Q is 0. Maybe that's the Q of systems you work with. It isn't the Q of anything I've ever worked with.
BTW, critical damping is a Q of .5. A Q of .707 is not critical damping - it is optimized for bandwidth.
You are talking about "free" vibrations of systems not forced vibration. When a system is forced at a resonance then the energy in the system is disipated in minimum time when it is critically damped. To me there is no energy "storage" in this case. Sure it takes time for the energy in the system to disipate, but there is only "storage" of energy when this time exceeds the minimum time for the energy to be disipated. By your deffinition of "storage" - zero time - any system that "contained" energy would be storing it and this is a pointless way to define the term because it makes it meaningless. "energy storage" and "energy" then become completely synonimous.
It's not my definition of Q or energy storage. It's an industry standard definition. If you have a different one, perhaps a new Wiki could be started.
So you are talking about using a driver where a passive crossover is used close enough to its resonance that its impedance becomes an issue. But then fntn keeps refering to using TL as the same thing and I only see those as a LF alignment. I have found the discussion a little confusing, but was not in on it from the begining.
I use a resistor across my compression drivers for almost precisely the reason that you state. I need to dump energy anyways so why not flatten out the impedance at the same time - so to me its not "the good old days", its quite contemporary.
I suppose this gets at the root of my dislike of the phrase "energy storage". I believe that what was intended was that a resonant system that has a high Q can take more time to disipate its energy than its period. This means that the energy disipation will oscilate at the resonance frequency. But if the Q is low enough then the energy is disipated faster than its period and the system just returns to its stationary state with no oscillations. But what fntn seems to be implying is that "energy storage" is any energy in the system and the time it takes to disipate it is not relavent. This later interpretation of the meaning makes "energy storage" a meaningless concept. At any rate I just never use the phase and that makes the discussion a lot more sensible. Its not a term that a physicist would use in the context of resonances. To me "energy storage" means a battery. A resonance cannot "store" energy in the same sense that a battery does because it will always disipate. The time it takes to disipate it is the key question.
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