John Curl's Blowtorch preamplifier part II - Page 3495 - diyAudio
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Old 12th February 2013, 06:05 PM   #34941
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Quote:
Originally Posted by SY View Post
It's a very nice table- I used an SL15 as well because it came with a superb cartridge (). it did have some cyclic subsonic output,
Due to some resonnance of this particular cartridge and the arm, or the motor of the arm during movements ?
What has become of this turntable, you do not have it any more ?
I'm looking for a replacement head for it, and i have no idea.
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Old 12th February 2013, 06:18 PM   #34942
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It was from the arm motor. I never noticed it until I got speakers that went a bit lower than ESL-57 or LS3/5A. I ended up giving the turntable away after I got my VPI. I'll bet there's still some around on Ebay...
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Old 12th February 2013, 06:18 PM   #34943
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Using a record jacket at the "null" direction from a pair of dipoles (Quad esl 63's) is pretty close to a test of controlled directivity. The secondary attenuated local reflections seem to be enough to be audible.
As would likely be the case if you removed all the furniture and other stuff from the room.

se
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Old 12th February 2013, 06:44 PM   #34944
RNMarsh is offline RNMarsh  United States
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Originally Posted by scott wurcer View Post
If I really wanted one I would just go for Stax. BTW how do planar drivers eliminate the head/driver cavity effect?
The HiFiman has reduced that affect quit a bit... open back, a lot of damping material and who knows. Its a LOT less mushy/blurry sounding in the bass compared to most that use the cavity resonance to boost bass.

Show me the xDSL circuit and I'll go buy a Stax headphone. Thx-RNMarsh

Last edited by RNMarsh; 12th February 2013 at 06:46 PM. Reason: Planars and Electrostatics -
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Old 12th February 2013, 06:46 PM   #34945
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A Stax'O'phone
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Old 12th February 2013, 06:52 PM   #34946
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RnMarsh,
I don't see how opening the back affects the cavity side of the headphone except as regards reflected waves back through the diaphragm even if the rear chamber is damped? Unless the diaphragm was perforated how does it change the head side of the cavity resonance?
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Old 12th February 2013, 06:59 PM   #34947
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Originally Posted by sofaspud View Post
Jan, just curious... were you motivated at all to find this chip by the other thread, NXP Semiconductors cleaning house ?
No, not at all, didn't even know that thread.
Just would make my next project a bit easier.

jan
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Old 12th February 2013, 07:58 PM   #34948
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Originally Posted by Kindhornman View Post
RnMarsh,
I don't see how opening the back affects the cavity side of the headphone except as regards reflected waves back through the diaphragm even if the rear chamber is damped? Unless the diaphragm was perforated how does it change the head side of the cavity resonance?
The volume is the volume -- that doesnt change, of course. The affect of fully enclosing the diaphram does affect the bass and its damping. The same way as a sealed enclosure or a tuned port would. They have done a very good job of integrating all the factors with thier driver characteristics. And, I dont hear what is attributed to the cavity space as much as most others. Thx-RNMarsh
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Old 12th February 2013, 09:42 PM   #34949
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Originally Posted by john curl View Post
Max, I might say that while I have experimented with such 'platforms' but I would never have thought that valve springs were useful for them. What is the approximate resonant frequency, anyway, that you normally get? Is it below 5 Hz for example?
.
Hi John, under heavy speakers the resonance is at a few Hz.
Under equipment rack with shelves made of kitchen top stone similarly low resonance.
Works for me.

Dan.
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Old 12th February 2013, 09:54 PM   #34950
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Max,
It is amazing the lack of understanding of a spring and vibration damping you are demonstrating here. Take your car as an example. Leave the springs in the car and remove the dampers. Now drive down the road and tell me that the mass of the car will stop those springs from going into an oscillation.
The front shocks on my car are rooted. Going over speed bumps or stabbing the brakes can indeed cause a slow oscillation of the body wrt the road.
On smooth roads this behavior is of little consequence, indeed it floats and rides nicely.
Rough surfaces can induce a higher frequency resonance, but that is the unsprung mass resonating (think spring rate/tyre compliance) but still not a lot of transfer into the cabin of the car.

Quote:
Same goes for internal to an engine. If you have every worked on a cylinder head you would know that there is always more than one spring at a minimum. .
My car has one spring only per valve....that was the case when I last rebuilt the head.
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