In article ,
Harold and Susan Vordos wrote:
"DoN. Nichols" wrote in message
...
In article ,
Harold and Susan Vordos wrote:
snip-
What I would be more concerned about with that length is
possible loss of control of speaker overtravel, thanks to the added
resistance.
That's something I didn't understand. I guess that relates to a systems
ability to dampen. Feel free to correct me if I'm wrong.
You are correct. Perhaps a short explanation will help you to
understand. First off -- you want the minimum output impedance from
your amplifier, so when it wants to put out precisely 2.37 volts, it
*really* produces 2.37 volts, regardless of load (within reason -- a
short circuit can't be driven by the amp.
Now -- when you start to move the speaker cone, you do so by
applying a voltage to the voice coil. But when that coil moves in the
magnetic field, it generates a voltage of its own. If you draw current
from that, it loads down the motion of the cone, drawing energy from it.
(Like a motor overspeed will act as a generator.) The lower the
impedance of the amplifier -- and *everything* between the amplifier and
the speaker coil -- the more this motion-generated voltage will produce
a current in the opposite direction to slow down or stop the speaker.
If it is allowed to overshoot, it will introduce motion into the air
(sound) which does *not* correspond to the original recorded sound --
which we call distortion (one of many forms).
Speakers, BTW, should not be considered separate from their
enclosures. If you get a good quality speaker, and just put it cone up
on a table, and connect a 1.5V flashlight battery to it, you will hear a
"thump" sound. That means that there is a lot of low frequency
involved.
Now -- in an enclosure, the sound will be closer to a "click",
which is the true representation of the voltage step produced by the
battery. The better the speaker enclosure, and its match to the
speaker, the cleaner the "click" sound will be, and the less "thump".
(That "thump" translates into a boost in the bass curve compared to the
higher frequencies -- a "boomy" sound.)
The perfect match will produce a very clean and clear "click".
However -- if you add a resistor in series with the battery and speaker
voice coil, you will lose some of that clean click as the speaker
overshoots, comes back, undershoots, and so on until it finally stops
moving -- until you disconnect the battery.
That helps. My wife won't listen to classical, though I used
to. But we are pretty much in agreement for the rest. (And we met
through the local Folklore Society. :-)
Too bad she hasn't warmed up to the classics. That kind of listening really
has a place, at least in our lives.
Yep -- but with all else considered, I have no real complaints.
She even puts up with my shop. :-)
[ ... ]
And you certainly would not wish to subject good vinyl
recordings to the mangling from a changer.
Exactly. Regardless of how they may be perceived by others, to me they are
valuable and in some cases not available on other formats. I cherish each
and every record I have and intend to have them available for play in the
future. I'm not one of those that think they're better than a CD, not even
as good as far as I'm concerned, but if that's the only way I can have a
given performance, I'd rather have it that way than not have it. Not all
old recordings have been remastered, as you likely know.
You know -- you can get small CD recorders so you can play the
record *once* more into the recorder, and burn a CD from that, which you
can then use for many years without subjecting either the vinyl record
or the stylus (which will probably also become difficult to replace) to
more wear.
[ ... ]
Here is the URL for their web site:
http://www.hafler.com/
Thanks for the link, which I will pursue as quickly as possible, if for no
other reason, to get a better understanding. It's highly unlikely I'd make
any decisions before finishing the house, not wanting to add anything to my
plate at this time. I'm already wasting too much time talking with everyone
on RCM, which I thoroughly enjoy. I've learned a great deal along the way,
too.
I know how you feel about that. :-)
I was playing with electroncs long before I got a chance at
machine tools. The shop class in high school only taught woodworking,
which was not a good fit for me.
I share that with you. I've never enjoyed working with wood.
It does not stay put when you shape it. :-)
It was not until I was working at an
Army R&D lab that I got a chance to learn machining from a couple of
resident machinists -- and I have been glad that I did. (Of course,
before that, I was trying to do things like building a tape deck for
10-1/2" reels from scratch -- mostly with hand tools and an electric
drill motor -- and files and coping saws. :-)
After looking at the high level of precision used in building the Crown we
own, and the sophisticated controls it has, I can't even begin to understand
how a novice would go about building such a device. I really admire your
courage! I trust you were not successful, not with hand tools. g
Well ... I was successful enough so I could play tapes on it.
The motors which I used for spindle motors did not allow really good
control of fast tape motion, so I had to wait for it to run off the
supply reel. And in particular, I did not have the tools to make proper
brakes.
I was using various things which I had picked up at a surplus
vendor, including a mount for a pair of 1/4" ID ball bearings for the
spindle. I "turned" the capstan spindle with a file (after mounting
it), and used a micrometer to check my progress, until I got something
which could drive the tape at the proper speed.
I did add a saber saw to rough shape things like the pinch
roller arm, and the end-of-tape tension sensor arm, which I then
finished by filing. Those went into found bearing assemblies like that
for the capstan spindle.
I also had a "drill press" stand for the drill motor, and
quickly learned the problems with those for even an attempt at precision
work. :-)
The electronics part was easier for me, as it needed fewer
specialized tools.
Some years later, I was coming out of a hamfest (think giant
electroncs flea market), when I saw someone else walking in with a tape
deck with no elecronics. I asked him if he was taking it in to sell,
and he said "yes". So -- I bought it -- at all of $2.50 IIRC. That had
an interesting capstan motor -- it was an "inverted rotor" design -- the
rotor surrounded the coils and poles. And it was set up with three
windings, for 15 IPS, 7.5 IPS, and 3.75 IPS. I had to put new heads in
it, but everything else was as I needed it -- for several years, until
the motor burned out its windings, at which point I dove into attempting
to rewind it. I never got it quite right -- too fine a wire, I think.
That tape deck was made for military (I think Navy) use, based
on its nameplates, but was nicely built.
But -- I then picked up an Ampex 440B recorder at a surplus
sale, and later a Revox A700, so I was all set from then until I moved
to DATs for recording. *Those* I bought new. :-)
Enjoy,
DoN.
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