Good work on the Isobaric John. You make me scared 
. You seem to have covered everything. Even harmonics go down, uneven stay the same. Fine, i knew that.
Thanks fo reminding me that mechanical coupling helps. I used that idea in my 1989 Avanti. OHHHH, i get old. Some call me a dinosaur here in Europe. At that time they called me crazy. "It can not work".
Migeo, i never whould use an Isobaric in the midrange. I did not like the Sara much eather but it was a success on the marketplace. What i did not like at all was the wall placement. It totally robbed the sound of any depth of image and the voices came from where the frontwall hit the floor. Weired.
Thanks SY. You liked the sound and with some modifications Dyanaudio made it work, so it can be made to work.
Earl, i did not say that cancelation of even order harmonics is a major design criteria. It just comes for free in a push-pull arangement. i did not even say that i WILL use an Isobaric ( but i will try it ) and yes, this Isobaric thing is very controversion too.
. You seem to have covered everything. Even harmonics go down, uneven stay the same. Fine, i knew that.Thanks fo reminding me that mechanical coupling helps. I used that idea in my 1989 Avanti. OHHHH, i get old. Some call me a dinosaur here in Europe. At that time they called me crazy. "It can not work".
Migeo, i never whould use an Isobaric in the midrange. I did not like the Sara much eather but it was a success on the marketplace. What i did not like at all was the wall placement. It totally robbed the sound of any depth of image and the voices came from where the frontwall hit the floor. Weired.
Thanks SY. You liked the sound and with some modifications Dyanaudio made it work, so it can be made to work.
Earl, i did not say that cancelation of even order harmonics is a major design criteria. It just comes for free in a push-pull arangement. i did not even say that i WILL use an Isobaric ( but i will try it ) and yes, this Isobaric thing is very controversion too.
Specifics would be nice. Look, I'm certainly not perfect - just as mistake prone as the next person. But there's no way I'm going to be able to learn from general and vague statements like "energy storage is meaningless" as to what I'm overlooking or mistaken about. Please be specific. Take any specific statement or assumption and pick it apart at will. That would be fine by me and perhaps this thread could be of some use to me as I might actually learn something.
I believe I stated earlier in this thread that energy storage is created when a force vector is exerted upon a mass over a distance. It's a pretty basic definition in physics, no? Do you have a problem with that? Do you have a problem characterizing a diaphragm suspended on a suspension that has compliance as producing stored energy in that suspension when it is deflected? Can we at least agree on that?
Wait a minute. This is all a joke right? It's like I'm on candid camera or something and you guys are just making fun of me since I've been explaining the obvious. Ok, I get it now. Never mind, professor.
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Joachim
The 8th harmmonic goes up by almost an order of magnitude. In theory if I start with two identical drivers that have only even orders and combine them backwards then all the even orders are canceled but odd orders are created instead. In a more complex situation some orders go up and others down, but in a general sense the distortion is not lowered only moved arround.
fntn - I'd like to be more specific, but I am not sure that I know how to do that. If energy storage means simply energy content then I am at a loss to see how the concept can be used to clarify anything. All of the energy in a loudspeaker is derived from the amplifier. Lets say this energy is full specrum. Then the loudspeaker contains a full spectrum of energy as well. Is this energy "stored"? It is constantly being disipated in various form, mostly heat, but its not really stored in the sense that it stays after the excitation source is turned off - it disipates. Now it is true that it dissipates at different rates depending on the details of the loudspeaker. If there are resonances that have Q's above "critical" then these resonances will disipate the energy more slowing and oscillatory. But any resonace that is more than critically damped will disipate the energy at that frequency in the same time as any other frequency that does not have a resonance. To me this is simply not "storage" in the same sense as a high-Q resonance. But with your deffinition, low-Q, high-Q they are the same thing and hence they are also the same thing as the energy content at any frequency that is not a resonance. It simply looses all meaning.
The 8th harmmonic goes up by almost an order of magnitude. In theory if I start with two identical drivers that have only even orders and combine them backwards then all the even orders are canceled but odd orders are created instead. In a more complex situation some orders go up and others down, but in a general sense the distortion is not lowered only moved arround.
fntn - I'd like to be more specific, but I am not sure that I know how to do that. If energy storage means simply energy content then I am at a loss to see how the concept can be used to clarify anything. All of the energy in a loudspeaker is derived from the amplifier. Lets say this energy is full specrum. Then the loudspeaker contains a full spectrum of energy as well. Is this energy "stored"? It is constantly being disipated in various form, mostly heat, but its not really stored in the sense that it stays after the excitation source is turned off - it disipates. Now it is true that it dissipates at different rates depending on the details of the loudspeaker. If there are resonances that have Q's above "critical" then these resonances will disipate the energy more slowing and oscillatory. But any resonace that is more than critically damped will disipate the energy at that frequency in the same time as any other frequency that does not have a resonance. To me this is simply not "storage" in the same sense as a high-Q resonance. But with your deffinition, low-Q, high-Q they are the same thing and hence they are also the same thing as the energy content at any frequency that is not a resonance. It simply looses all meaning.
I wish more attention was paid to this. Whenever I see more than a half-cycle of "ringing" in a system I find myself wondering "at what frequency is it ringing?" . . . and the answer is almost never "at the frequency (if there is one) of the exciting impulse". And where the ringing differs from the exciting impulse it becomes, by definition, "non-linear" distortion, doesn't it, since it represents the "creation" of a signal (tone) that was not present in the original? An extreme example might be a bell resonant at 100 Hz., excited by a 200 Hz. tone. Any "ringing" present, particularly after removal of the exciting signal, represents "distortion", doesn't it? Slightly less extreme would be a (typically lower Q than a bell) resonant box enclosure (as is commonly used to "augment" bass output). What does one call the decay trail of box resonance *after* the exciting signal (at other than the box resonant frequency) is removed?
OMG, you weren't joking!
The "physical Q" of the driver throughout most of it's passband is indeed quite close to zero because the energy stored is very low compared to the energy dissipated. At resonance, this changes. Part of the change is that stored energy reduces the demand for current from the amplifier because the physical load on the voice coil is reduced (due to an energy conversion sequence occurring in a store-release, store-release fashion). This is precisely why the amplifier "loses control" over the voice coil's motion (I'm sure we all can agree that current is what creates force on the voice coil and dictates motion). Thus small changes in voltage applied at resonance have little or no effect on voice coil motion because motion dictated by stored energy dominates. This is why the input/output transfer function at resonance is considered highly "non linear". The standard tests of additivity and homogeneity reveal this clearly.
The issue is not simply that high q resonances exhibit a gradual decay of energy - but that the build up of stored energy itself leads to non linear behavior because the intended driving element (amplifier) is no longer doing the driving.
Earl, the Isobaric idea is more about the reduced size. That is the basic ZDL idea.
I could build two versions, one push-pull and the other push-push. In an ABX test the outcome will be a null result. Drove Michaelson crazy. He did not trust until the end of his life that the speed of light is ............
I could build two versions, one push-pull and the other push-push. In an ABX test the outcome will be a null result. Drove Michaelson crazy. He did not trust until the end of his life that the speed of light is ............
We'll have to agree to disagree as my positions have not changed. You may have misunderstood them. And it's not worth the effort to argue what you think is accurate or not at this point. I stand by what I've said throughout this thread. As I said, if you question something, just ask, I'll explain my position more thoroughly if need be and you care to drag this out.
Dave
Michael, different drivers. The DA500 (not released for diy construction) used a paper cone 12 ohm 30cm on the outside and a paper cone 12 ohm 21cm on the inside. This crossed over to the "horn" version of the D54- the 17cm drivers didn't exist then. To me, the solution was quite elegant- the "isobaric" qualities weren't needed (and were indeed a problem) in the lower midrange, so the inner driver was choked off. The remaining interference was broadened out by the size of the intervening chamber and the perpendicular orientation- the distances were small compared to wavelength where the isobaric effect was wanted (sub-100 Hz or so).
That's the one! The plane of the 21cm driver is about at the level of the step between woofer and midrange. There's a fellow in Salt Lake named Bob Silk who probably still has my old pair.
I still have the 21cm drivers, but the 30cm ones in my storage have severe cone damage and haven't been supported by Dynaudio for at least 20-25 years.
I still have the 21cm drivers, but the 30cm ones in my storage have severe cone damage and haven't been supported by Dynaudio for at least 20-25 years.
Hello All,
I went to the produce market and missed two pages of posts.
A vertically mounted Iso-barik with a tube installed midrange mounted on top sounds compact, allowing the centerline distance between the woofer and midrange to be minimize. For integrating woofer and midrange outputs this sounds like a good idea. Good benefits and I bet that the drawbacks are still 30 db plus down.
For you EE types I have no dog in the hunt. I make my money doing ME things with springs as vibration and noise isolation in labs and hospitals (plus other stuff, I like hot water).
The origin of the stored energy discussion and testing by Linkwitz is not steady state. It is how much does this Driver A compared Driver B continue to flop about after the impulse is applied. In the case of an Iso-barik pair with twice the motor for the same effective piston area I bet it stops flopping twice as fast. Sounds pretty clever to me.
I guess we are all too proud for shoes.
DT
All just for fun!
I went to the produce market and missed two pages of posts.
A vertically mounted Iso-barik with a tube installed midrange mounted on top sounds compact, allowing the centerline distance between the woofer and midrange to be minimize. For integrating woofer and midrange outputs this sounds like a good idea. Good benefits and I bet that the drawbacks are still 30 db plus down.
For you EE types I have no dog in the hunt. I make my money doing ME things with springs as vibration and noise isolation in labs and hospitals (plus other stuff, I like hot water).
The origin of the stored energy discussion and testing by Linkwitz is not steady state. It is how much does this Driver A compared Driver B continue to flop about after the impulse is applied. In the case of an Iso-barik pair with twice the motor for the same effective piston area I bet it stops flopping twice as fast. Sounds pretty clever to me.
I guess we are all too proud for shoes.
DT
All just for fun!
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OMG, you weren't joking!
But I sure hope that you are. I'd hate to think of someone coming here and taking explainations like that as serious science. I see why others have simply stopped discussing this with you. I'll probably do the same.
If you are talking to me, my position would be that I have never seen the usefulness of isobaric. (I'd love to hear your justification for them.) To me a simple closed box with a low(ish) Q is ideal for the mains, and, of course, multiple subs for the modal region. I can't see any other viable solutions when cost and size are prominate factors. I find dipoles interesting for directivity control in the ka (wavenumber * radius) region where a closed box cannot yield any appreciable directivity, but then comes the modal region of the room and the abominable efficiency of the dipoles. I have sketched out some designs which have dipole mid-low directivity and monopole LF sensitivity, but the cost and size just become prohibitive. Maybe some day I'll hang-up my hang-up with extremly costly solutions to problems, but at this point I can't do that.
Every resonance has bandwidth. If you apply a 200 Hz signal to an oscillator it oscillates at 200 Hz because it is a forced response. When the 200 Hz signal is removed the system will return to rest based on it natural behavior from the conditions (displacement, velocity and acceleration) at the time the signal was removed. This will be a natural or free oscillation at the natural frequency. Nothing nonlinear about it. It is just the transient decay of the linear system.
Go back the the weight hanging on a spring. If you displace the weight and let it go it oscillates and decays at its natural frequency, but it you grab hold of it you can move it at what ever frequency you like. When you let go of it again it will oscillate and decay again at its natural frequency.
Could you imagine Earl that an isobaic sounds different ? Anyway, i take your contribution seriously. An isobaric with my target response and the drivers i use comes out at 40 liters.
A closed box comes out at 80 liters and a reflex with one driver needs 100 liters plus. Of cause the isobaric waists sensitivity but this is more a nearfield design.
Thanks John. Until about 2 years ago i had even full hair although a fancinating shade of grey, brown, silver and gold.
A closed box comes out at 80 liters and a reflex with one driver needs 100 liters plus. Of cause the isobaric waists sensitivity but this is more a nearfield design.
Thanks John. Until about 2 years ago i had even full hair although a fancinating shade of grey, brown, silver and gold.
OMG, you weren't joking!
The "physical Q" of the driver throughout most of it's passband is indeed quite close to zero because the energy stored is very low compared to the energy dissipated. At resonance, this changes. Part of the change is that stored energy reduces the demand for current from the amplifier because the physical load on the voice coil is reduced (due to an energy conversion sequence occurring in a store-release, store-release fashion). This is precisely why the amplifier "loses control" over the voice coil's motion (I'm sure we all can agree that current is what creates force on the voice coil and dictates motion). Thus small changes in voltage applied at resonance have little or no effect on voice coil motion because motion dictated by stored energy dominates. This is why the input/output transfer function at resonance is considered highly "non linear". The standard tests of additivity and homogeneity reveal this clearly.
The issue is not simply that high q resonances exhibit a gradual decay of energy - but that the build up of stored energy itself leads to non linear behavior because the intended driving element (amplifier) is no longer doing the driving.
Energy stored in mass and compliance elements. Energy exchanged between them . Down hill form there.
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