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Old 3rd March 2010, 07:03 AM   #21
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Quote:
Originally Posted by anatech View Post
So, can you expand on what these reasons might be?
Chris, it is in the book. Buy a copy and read it. You'll probably learn something new... or at least a different view of what you already know.

dave
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Old 4th March 2010, 01:50 AM   #22
maxro is offline maxro  Canada
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Originally Posted by planet10 View Post
Hopefully makes it a collector's item.
According to Amazon.ca the first edition is $163.00.

The new one is only $22.50 (less than in the states) but it's out of stock. I put in an order anyway, as they tend to take the sale prices away after restocking.
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Old 4th March 2010, 02:43 AM   #23
anatech is offline anatech  Canada
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Hi Dave,
No, not to clear up the simple points I have raised. Especially not since I can see what I would consider to be incorrect assumptions posted and on his web site. It's Esa's book and Esa's comments. Like statements made anywhere else, the author should be able to explain the basis for the conclusions drawn without forcing people to buy the book in order to understand where the author is coming from. In fact, since there is no two way dialog going on in reading a book, sooner or later the concepts need to be discussed somewhere.

To be honest, clearing up a couple points I've raised will not endanger his book sales. In fact, touching on a couple points will raise curiosity and probably increase book sales. I have a decent library of books already, so I'm not adverse to paying for something that I will benefit from. If you saw my place, you'd understand this (then run screaming! ). My concerns rest with some things I have read that contradict what I have seen in my own experiments, they need to be clarified before I'll part with any $$. This is especially true when money is in short supply for me right now, I'm sure you'd agree if faced with the same situation yourself.

If you feel that you can answer some of my concerns / questions, I'd be happy to exchange email with you on this. I'd like to see your perspective on this.

Then we also have a new approach being used with sub-woofers like the Sunfire and others. They are treating the woofer as a piston only, with little regard for what T/S parameters indicate. I don't agree with the practice, but I guess if you throw enough power at a problem, it will go away.

Best, Chris
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Old 4th March 2010, 03:12 AM   #24
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Why not start here:

http://www.essex.ac.uk/csee/research...nt%20drive.pdf
http://www.essex.ac.uk/csee/research...0amplifier.pdf
http://www.firstwatt.com/downloads/cs-amps-speakers.pdf

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Old 4th March 2010, 04:06 AM   #25
anatech is offline anatech  Canada
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I've read some, and I'll try to check out the other links.

So thats the information, I was hoping the author would comment directly.

-Chris
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Old 4th March 2010, 06:36 PM   #26
UnixMan is offline UnixMan  Europe
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A limited preview of the book can be found on
Google Books
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Old 5th March 2010, 04:48 PM   #27
ETM is offline ETM  Finland
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Quote:
Originally Posted by keantoken
when you consider a coil moving through a magnetic field. That is a current source rather than voltage source, right?
A coil moving through a magnetic field is anyway a voltage source according to the formula e = Blv. It produces current only if there exists a current path, the current being then Blv/Z, where Z is the impedance of the path.

Quote:
Originally Posted by anatech
Hi Bear,
Yes, I realized that later. Your post really drove it home though.
What have you realized? Is this not a commercial area? What rule is being violated?

Chris,
Perhaps you really are somewhat open minded about these issues, as you say, but some of your commentary in its irrelevancy quite doesn't support this assumption.

Anyway, your point seems to be in essence that the common practice must be the best practice because it is the common practice. I don't think that way, and I understand the message can appear quite tough for those who do.

Quote:
Originally Posted by anatech
Any back emf results from current flow as the loudspeaker motor acts as a generator whenever the coil moves through the magnetic field.
Quote:
Originally Posted by anatech
the current is created as a direct result of the voice coil moving through the magnetic field. The exact same amount of current is created whether you drive the speaker with a high or low impedance. It is completely defined by the number of "lines of magnetic force" that are cut as the coil moves through "x" distance with "y" velocity.
Quote:
Originally Posted by anatech
As I mentioned earlier, every time the voice coil moves in any magnetic field, it will generate an opposing current to that current which caused the motion to begin with.
No, absolutely not. When a coil moves in a magnetic field it generates an EMF according to the formula EMF=Blv which defines a voltage source. This EMF voltage is generated irrespective of how the coil ends are connected. Current is generated only if there is a path for that current, i.e. if the coil is connected to some finite impedance. In a voltage driven system, the coil is connected to zero impedance, so the EMF-derived current is limited mainly only by the voice coil's resistance. In a current driven system, the coil sees, in principle, infinite impedance, so the EMF is not able to generate any current.

As for the damping, it is indeed only a matter of shaping the frequency response at the low end. When this is done by whatever means, the speaker is damped, and there is no further need to "arrest" anything.

As I said in post 10, the frequency response and transient response of any linear system are not separate things but one and the same thing only viewed in different ways. If any two linear systems have the same frequency response (amplitude & phase), then their transient responses (for any input) must also be equal - there cannot be any difference. This stems directly from the Fourier Transform and properties of linear systems. Therefore, if the frequency response of a loudspeaker that is designed for current operation is made equal to the frequency response of a loudspeaker designed for voltage operation, then all the transient properties of the two speakers are also automatically equal, and in this respect one cannot be better than other.

If you are still left with open concerns, please state them clearly one or two at a time, and I'll be happy to address them as soon as I can.
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Old 6th March 2010, 06:44 AM   #28
Gordy is offline Gordy  United Kingdom
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EMT; very interesting! I will be returning to continue reading this thread. Good luck with the book sales, and with your work in this field of endeavour.
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Old 6th March 2010, 10:32 AM   #29
SY is offline SY  United States
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Chris, the Mills and Hawksford paper is very worthwhile to read to get started. My question is more toward what this book covers that goes beyond their work, as opposed to just elaborating on well-known stuff like theirs (not that this would be necessarily a bad thing).
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Old 6th March 2010, 01:15 PM   #30
godfrey is online now godfrey  South Africa
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Is this not a commercial area? What rule is being violated?
IIRC, this thread was originally posted in another area, before being moved here.
No problems now.
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