Right! However, "work" is not (always) the same as "movement".
If you start with a silent speaker and then apply a sine voltage exactly at the Helmholtz frequency, the cone will start moving and oscillating at this frequency for a short time. Once the Helmholtz resonance is fully established, (almost) all the electric energy injected to the driver is transferred to the resonating spring-mass system formed by the air mass in the port and the air spring (box volume). The energy is transferred from the driver to the air volume (mostly) by the cone applying pressure to the air, not by cone movement.
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For good order: all mechanical damping mechanisms in drivers are highly non-linear and should be minimized in order to achieve overall low distortion. A Qms of 10 is great.
Let's not get this misconception take hold on top of the others. A low Qms is not good. Anyone care to look up the specs of Purify or the drivers JBL produces for low distortion?
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Utterly impossible. Show measurements. Stick to Einstein and Feynman.
Cone movement is the begining, sure, and this is a transitory stage; when resonance is established and steady, the cone couldn't stay fix in space, otherwise how could the coil "inject" any energy into the system? Loudspeaker is indeed a real-world system and as such, couldn't maintain resonance without energy being fed into the system.. this in turn implies the cone to move to some extend...
Correct me where I'm wrong please.
Kal.
Correct me where I'm wrong please.
Kal.
In Elsinore news, upgrading some crossover parts from what I started with. Moving from Z-Superior to Audyn True Copper Max and moving to a Duelund resistor for the tweeter. Will have some of the old (barely used) parts for sale in time (good quality, e.g., Jantzen Z-Superior). Will also have a set of 8 never used SB17MFC35-8 speakers up for sale soon. I was lucky and found a set of the NRX speakers locally after having bought the MFCs. Prefer to stick to Canada and will make that note in my ad. Let me know if anyone is interested before I have a chance to post.
You are not wrong. I never meant to say that the cone excursion is exactly zero at the tuning frequency, at least not in a real-world system. Once the steady state is established after the initial build-up phase, the energy dissipated by the Helmholtz system needs to be balanced by the energy input from the driver. The cone excursion therefore cannot be exactly zero, but it is very small because the forces exerted by the Helmholtz resonator on the cone are large. Remember that the energy transfer is the product of "force x excursion".
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That worries me a bit. I simply used the "quote" button to quote your post #3461. If post #3461 was not written by you, it looks like someone else used your account to write this post. If so, you should check your login / password and maybe get in touch with a forum administrator.
mbrennwa,
You posted '64 and '65. The first one quotes boswald from '62 and the second quotes Joe from '61.
IIRC both originally said Joe Rasmussen. If you hover your cursor over the small blue arrow in the quotes, the links both show as belonging to '61 (I didn't change the blue post markers but I changed the name in '64)
(Edit: It happens
)
You posted '64 and '65. The first one quotes boswald from '62 and the second quotes Joe from '61.
IIRC both originally said Joe Rasmussen. If you hover your cursor over the small blue arrow in the quotes, the links both show as belonging to '61 (I didn't change the blue post markers but I changed the name in '64)
(Edit: It happens
)
I am not seeking an argument, especially when I already have a practical outcome that at least seems to work.
Encyclopedia Britannica:
When describing the motion of objects in terms of distance, time, and direction, physicists use the basic quantities of speed and velocity. Two terms, two distinct meanings. Yet, not uncommonly, we hear these terms used interchangeably. So, what’s the difference? Why is it incorrect to use the terms speed and velocity interchangeably?
The reason is simple. Speed is the time rate at which an object is moving along a path, while velocity is the rate and direction of an object’s movement. Put another way, speed is a scalar value, while velocity is a vector. For example, 50 km/hr (31 mph) describes the speed at which a car is traveling along a road, while 50 km/hr west describes the velocity at which it is traveling.
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Blatantly untrue. This is why I don't reply to you. Stick to A.N. Thiele and Richard H. Small.
Velocity is speed with a direction, speed has no direction.
Does the air in the box have a direction?
dave
Ask the vent. That is where it has to get to.
But maybe viewing the box dimensions as much smaller than the wavelengths and hence LF is just seen as changes of pressure inside the box and does not 'travel' in any direction? I am open to views on this and have thought along those lines too.
But... take a box, add a vent, measure the box tuning Fb, then add fill and be careful not to obstruct the vent, now the Fb of the box has dropped significantly as if the box size has increased.
Indeed you could have achieved a similar effect by actually physically increasing the box.
So what explains this?
How did the box all of a sudden act as if it volume increased by 30% - what is the mechanism at work?
I am very open to possible answers, but it seems to me there is an obvious answer. Maybe I am wrong, but I have not yet seen an answer that explains otherwise. But I seem to be in good company?
"The effective volume increase can be as much as 40% and is due primarily to a reduction in the speed of sound propagation through the filler material as compared to air." L. Beranek, Acoustics, 2nd Ed. 1986
Does not the word "propagation" indicate a direction?
Joe
Hi Daan
Sorry for the delay. It has been on my mind for a while to reply and things are slowly getting back to some near normality, except I am not sure what normality is these days.
I still remember our "Dash to Amsterdam" to get that tripod. Now that Tim De Paravicini has passed away, I recorded his lecture at ETF06 on your tripod. Now several of the guys, including Bjørn Aaholm, Kurt Steffensen and others, wants me to post it. I have to cut it down in size files (6) and I am no video editor. But I remember I gave you a copy of that lecture as well. I think it will be on Facebook, but never done it before.
____________________________
Now onto the Elsinores: About you having heard them? I don't think you have. There are two points to be made.
1. When Allen and I brought them to ETF06, I had not heard them before they got loaded into Allen's car. I did not know that Thomas had made a mis-wiring where in one speaker the Midrange part of the Xover went to the Bass and vice versa. It was not until when they were moved them to Bjørn Aaholm's room that it was discovered and corrected. He had brought a 3-Way design of his own and we did some comparisons. We were both pleased. But I recall that was Saturday night and only about 6 of us stayed up to 2AM listened, while Bjørn was providing Danish winter beer, cooled on the ledge just outside the window where it was about 4-5C.
2. That was Mk1 (which you did not hear properly) and can in no way be compared to the current Mk6. They have merged into a very different design. The progress has been very substantial and the Mk6 has morphed into a very different speaker.
No, I don't need social media at all!
People keep telling me about this "market" and I keep asking "what market is that?"
Elsinore speakers are a market? Nope!
To be honest, I don't use social media that often. Here on these all forums I average about 3 posts a week and sometimes not even one in an entire month. This year the posts have been very infrequent. This is on all social media. I sometimes have fun commenting on a few YouTube video under a nom-de-plume and they are about being witty observations.
So how do I survive, how do I pay the bills? I make an income doing a whole lot of other things that most here would know very little about.
YouTube: Don't Wait Until Tomorrow - Leo Sayer recorded on an All-Tube Front-End custom made by yours truly.
-------------- YOU ARE LISTENING TO THE "TUBE STATION" --------------
Here is another point, the Elsinores have actually made me lose money over time. Let me explain:
Joel Wesseling used to make the Waveguides in Canada and ship them world-wide with my blessing. Ask him how much I made? Zilch! But he wanted somebody else to take over.
I recall somebody in Sweden was going to take over making them. Alas, that fell through and I don't know why. Would I have made a cut? No. Same deal as with Joel.
So I made a decision that made no sense financially, but at least would stand as proof towards those who somehow think the Elsinores are a cash cow to me:
I asked an industrial designer friend of mine (Hi Alex) to help me out. I won't say how much it cost, but enough to say that it could have bought a very decent car and not a cheap one. The weight of Acetal (Delrin) is about half that of Joel's aluminium, so postage could come in just under 1Kg. Even now I am just getting my money back and the last of this batch will put me in the black. When I run out, I have to make another big decision (Hi Alex, need your help again) and I will be in the red again.
So really, can you blame me, I am a bit tired when people think that I need social media. I just don't!
But I have made a lot of friends. Try put a price on that.
Cheers, Joe
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I gave a number of explanations, and I thought that you actually read them. Reiterating some key aspects:
- Damping efficiency decreases with decreasing frequency, resulting in a lowering of the tuning frequency of the resonant system.
- Tortuosity leads to longer sound propagation paths.
- Increased thermal capacity reduces the speed of sound.
So why do you seem to ignore the explanations given in this thread?