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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old Yesterday, 05:33 PM   #12741
gpapag is offline gpapag  Greece
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John Curl's Blowtorch preamplifier part III
Quote:
Originally Posted by 1audio View Post
Read through the white papers on the Hartley site. They mention a "magnetic" suspension they worked out in the 1950's along with a number of other interesting ideas.
Thanks Demian. Very informative white papers.
Almost all these interesting ideas were a subject of an issued patent. Check out “Luth, Harold J.”
I had heard a 10inch FR Hartley of such a construction and it was really good sounding

George
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Old Yesterday, 05:46 PM   #12742
TNT is offline TNT  Sweden
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Smart!

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Old Yesterday, 07:54 PM   #12743
john curl is offline john curl  United States
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I must complement everyone who is submitting these LINKS on various subjects. I find them invaluable to keep up to date.
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Old Yesterday, 08:25 PM   #12744
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by RNMarsh View Post
yes. That is cookie-cut from thin fiberglass sheet.... very stiff. The cone edge surround is rubber/cloth.... very flex.

Both have same affect as to tug on the VC/cone and cause distortion.


THx-RNMarsh
back in the day (1970-80-ish ?) ---- this is the Hartley Demian is talking about.....I had a stereo pair of the 18 inchers in a rear loaded folded transmission line (See Speaker Builder). measured flat to 16Hz in my room. At one time I laid them on their side and sat the original QUAD ESL on them... made the ESL about ear height.

I am not sure how well the magnetic suspension idea worked... didnt see any harmonic tests at that time. But , i think Ferro-fluid has replaced this idea.


Picture2 096.jpg

Hartley 218 drivers as subs for a custom built DynAudio 3-way (W-M-T-M-W).


When I did not need them...I gave them to my brother-in-Law who used them on stage in northern California clubs ... he is obviously a bass player. he loved the sound but not moving them. Each the size and weight of a refrigerator.


THx-RNMarsh

Last edited by RNMarsh; Yesterday at 08:43 PM.
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Old Yesterday, 09:16 PM   #12745
gpapag is offline gpapag  Greece
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John Curl's Blowtorch preamplifier part III
Quote:
Originally Posted by RNMarsh View Post
But , i think Ferro-fluid has replaced this idea.
It’s not the same concept.

Ferrofluid is concentrated along the width of the front plate and stays focused there.
It doesn’t move with the voice coil like the iron particles which are glued on the voice coil in the patent of Harold Luth.
Therefore with ferrofluid, the flux flow isn’t moving along with the voice coil.
Subsequently ferrofluid can not provide any magnetic restoration force.

George
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Old Yesterday, 09:17 PM   #12746
orjan is offline orjan  Sweden
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Quote:
Originally Posted by 1audio View Post
You could make a spider like the one above out of phosphor-bronze or beryllium-copper and use it for lead out connections as well.
Hi, If memory serves, Ted Jordan used that idea in his speakers.

/örjan
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Old Yesterday, 09:32 PM   #12747
scottjoplin is offline scottjoplin  Wales
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^ From here http://www.ejjordan.co.uk/PDFs/EJJ_1...W_titanium.pdf

"One very important requirement
for the suspension system is that it
must be completely linear over the
full range of cone displacement.
Failure to be so results in the very
high harmonic distortion apparent in
the extreme bass response of many
loudspeakers. The suspension system
itself must be mechanically stable,
and this requirement led to the use
c,f three tangentially disposed beryllium copper cantilevers (two of which
are used to carry the voice coil current). The cantilevers are attached
at their inner ends to a rigid insulating annulus surrounding the coil and
attached to the coil via a " lossy "
compliant medium the purpose of
which is to ensure that the mass of
the suspension system is decoupled
from the coil at high frequencies. "
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