An excellent book that shows how different systems are in fact equivalent is "Dynamical Analogies" by Olson. Downloadable from eg https://worldradiohistory.com/BOOKS...Technology/Dynamical-Analogies-Olson-1943.pdf
An old book, but completely relevant even today. Fairly mathematical, but that comes with the topic.
Lots of stuff in there about the commonality of electrical quantities with acoustical and mechanical systems (like flywheels).
An old book, but completely relevant even today. Fairly mathematical, but that comes with the topic.
Lots of stuff in there about the commonality of electrical quantities with acoustical and mechanical systems (like flywheels).
Indeed - Harrry Olson's book on Acoustical Engineering is a standard text on the subject even now. Along with FV Hunts' book on ElectroAcoustics and Leo Beranek's book Acoustics were the three major texts on the subject.
Leo Beranek in later years (he lived to 102, and was born before the first world war in 1914!) wrote Concert Halls and Opera Houses in which he provides acoustical parameters for all the major such places. I am very lucky to have a signed copy by the great man. Among his massive technical ability, he was also a concert grade pianist. Quite a guy.
https://en.wikipedia.org/wiki/Leo_Beranek
Leo Beranek in later years (he lived to 102, and was born before the first world war in 1914!) wrote Concert Halls and Opera Houses in which he provides acoustical parameters for all the major such places. I am very lucky to have a signed copy by the great man. Among his massive technical ability, he was also a concert grade pianist. Quite a guy.
https://en.wikipedia.org/wiki/Leo_Beranek
We've spoken about specifying components that are placed directly across an amp, and the inevitable rise in coil temperature as coil resistance is increased and inductor size reduced. Members have a need to know of the limitations and any concerns.
Is that something you'd consider explaining?
Quite so. The Jantzen inductor I use can cause elevated temperatures because it has DCR of 3R2, but as the DC of the inductor goes higher as it gets warmer, the damping of the tuning frequency (typically near 60-70Hz), will go in the right direction.
The current actually reduces, but the above example is when the inductor's DC is doubled and even then result is not too bad. Compare that to no LCR.
So the load don't get worse with that 18mH 3R2 inductor. In fact all the above scenarios are easy loads.
Under current drive you might get a slight 60 Hertz bump. But who are currently doing that with the Elsinores, in fact they do very well using current-drive. I can demonstrate that to anybody who comes around.
The above example is the NBAC. But the others are also quite similar.
Below is the various current phase angles.
As things do, naturally. The Elsinore is capable of considerable output. A builder who wants to use them to their strength would really like to use a lower resistance unit that could manage the power. In a critical position across the amp, it only makes sense.
Interesting that you should remember the "isolation" word, pleased that you did; and yes, isolated from the point of view what the amplifier sees on the current side. The 0.1R is a thought experiment (Danish scientist HC Ørsted looks to be the first), and if any reactive current triggered by the load of the amplifier, this will largely be isolated from the amplifier. You are right, the resistor does not store energy. It is the fact that it does not, that this means that the amplifier is effectively seeing no store energy at all, but the drive still contributes.
Nobody in their right mind would argue that no reactive current occurs because of the load of the speaker. We all know that.
That 0.1R as a thought experiment, where we effectively are ignoring heat and even the ability of the amplifier to supply 80x the current, will isolate by 80x (800%?) the reactive current triggered by the driver. This conclusion is hardly rocket science. Crudely you are swamping any existing reactive current or any current that is not resistive. Hence the isolation word.
But what then is a good way of applying the above. My conclusion was a simple one, look to be guided by the DC resistance Re of the driver, typically 6 Ohm. Make the amplifier produce the same current at all frequencies, or in effect EQ the current to see 6 Ohm at all frequencies.
Of course.
And in this instance, this is exactly what we want. We just want resistance.
You are absolutely right, the Elsinores can go very loud if you to. Before Covid I took a pair down to Melbourne Audio Club and the room was very heavily draped and damped. We have to raise the Elsinore about a foot of the floor. I used a 32 Watt amplifier and the front four rows got the full impact and dynamics (I got comments and reactions about that), but the back of the hall was a bit muffled and could not do much about that and more power would not have helped. But I was more pleased than I thought it would be, as these demos are fraught with dangers (don't like the sound much that we get at Epping). But certainly, the Elsinores could have been used with a more or very powerful amplifier and I am not blind to the inductor issues.
I have no objection to use 18mH inductors with lower DCR and have indeed used them as well. Even those, and large physical size, they are still up around 1R. But when designing the PCB I now have the option of using a much smaller inductor that now fits on the PCB, but higher DCR. But you can still use the larger physical size inductors and wire them into the PCB even if not on the PCB. But I did use my DC lab power supply and used it as a current source and set the current. Could I make it warm up? Yes, but fairly slowly, a good thing as they do still have significant thermal mass. I can also track the rise in DCR as it gets warmer. I am fairly satisfied with the results. BTW, I do have a Purifi amplifier that output well over 400 Watt into 2 Ohm and still a fair bit at 6 Ohm. Not a problem even playing loud.
It's probably about 50-50 for 'small' inductor versus larger circa 1R inductors. Not had a single issue yet. But I agree, not the perfect solution.
Here is a simple thing to try. If you have a typical 2-Way speaker system, so common these days, then if it is rated a 8 Ohm, then try the following:
Get some decent size 8R or 8R2 resistors, two of them. Most amplifiers can handle 4 Ohm. Connect the speakers to the amplifier. Now across the speaker terminals, add the 8R right across the speaker terminals. It will turn the speakers into 4 Ohm and be seen that way by the amplifier.
Now take a listen.
Get some decent size 8R or 8R2 resistors, two of them. Most amplifiers can handle 4 Ohm. Connect the speakers to the amplifier. Now across the speaker terminals, add the 8R right across the speaker terminals. It will turn the speakers into 4 Ohm and be seen that way by the amplifier.
Now take a listen.
Could you please show this in a circuit simulation, using adequate "probes" exemplifying the 80x effect? I could not follow the reasoning (my bad probably) but a spice model and simulation would educate me in the complex.
Thanks!
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I have tried to make it as clear as possible and when I posted it, I added that if there is any confusion, to please simply ask and there are plenty on the thread to help, in addition to myself. So yes, the total target is 6R6, my compact inductor is 3R2 and I used two 6R8 in parallel to make up 3R4 plus 3R2 = target 6R6.
Does that mean 10.3W for the resistor and 9.7W for the inductor, or does it mean 20W and 20W?
You are welcome.
But it's not that complex, the 0.1R is a thought experiment and a rather simple one. But for it to work, you have to ask "what does the amplifier see." Now I know that the amplifier is not a person, just simply asking a perspective view that we need to look at. When I use 80x number I was wondering if somebody would ask, just as you did. It was based by 8R/0.1 = 80, and nom more. The number is suggestive, that's all.
But I feel that misses the point. For example (relying in memory a bit here) Esa Merilainen said that adding a series 8R resistor (not parallel) and he suggested a reduction of distortion of 6dB because the ratio is 2:1. I did not take it any other way, other than as guidance. Now I am suggesting that using a parallel 8R actually might be the better option and certainly 0.1R is not.
I remember going back and having a related/similar discussion with Stuart Yaniger (SY) and he insisted the the amplifier should be viewed as a 'black box' and that the load had no effect on the amplifier. He had compartmentalised his view of the amplifier. The current triggered by the load, the loudspeaker, is a matter of "can the amplifier handle it or not" and this represents the compartmentalised view. The ability of the amplifier is the question of current headroom, can the amplifier supply current without getting into difficulty?
Again, the represents the SY compartmentalised view of the amplifier and makes the amplifier the 'black box' that he suggested.
I suggest otherwise.
Recently an audio magazine had an article about "how loudspeakers torture amplifiers" and so the compartmentalised view is being challenged. I am not only challenging it, I think it goes well beyond just torture. I am suggesting something along current modulations that can be moderated somewhat out by either a series (Esa suggestion) or parallel (my suggestion) resistor. But these resistors are just starting points, that they must point to more sophisticated solutions, even if they don't work 100% but are still worth aiming for.
I know what you have been asking for and my answer is still the same. I am not trying to be difficult, far from it. We will make it official in the traditional form that we have decided to use and not via social media. There will be time for that.
After that, maybe there will be a lively lounge discussion on the subject and everybody can air their views. It will likely be lively, but it will also be the right time. Hope you understand. But I would like us to get to that stage sooner rather than later. I look forward to it. It should be fun.
SY seems to be a well informed person.. did he really mean what you describe... care to provide a reference for this?
I'm sure he could have said that it should be viewed as a black box but in no way does this imply that it becomes load unaffected. I doubt he wrote so.
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