|
High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
|
|
|
High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
|
In Reply to: RE: What makes a driver High Efficiency? posted by claudej1@aol.com on May 30, 2023 at 14:35:07:
This is complicated as there is more involved than just motor strength.
What you have is a mass and spring (moving mass and driver plus box compliance or spring) Those two reactance's have a resonance where the two reactance's are equal but opposite and cancel out. AS you approach resonance, you see the parallel L and C's effects cancel out and at Fb resonance the only load you see in the impedance peak is the Qm mechanical losses and a tiny amount of radiation resistance (big ohms).
The motor is connected to this moving stuff and so is the radiator.
The bigger and more massive the moving system, the larger the BL has to be to have the same amount of "control" on the moving system.
The amplifier (in modern times) is assumed to be a low impedance voltage source. It used to be a selling point that the amplifier's output impedance was tiny with respect to the load and the ratio expressed as "damping factor".
In loudspeaker land, the driver has a DC resistance (Rdc) in series with the motor so the amount of "control" is limited by that Rdc (BL and Rdc controlling motor part of the driver Qe). The amplifier appears to be a small resistance in series also but if the load were 4 ohms and the DF 100, the amplifier looks like 4/100 Ohms. Around 20 or 30 DF is where making it larger has very little/ less and less effect.
A series resistance that is significant (say an Ohm) begins to modulate the normal frequency response, where ever there is a low impedance, there is a new small dip or depression added and so the shape of the response curve is altered by the addition of a version of the shape of the impedance curve.
Morricab brings up an obscure but real issue.
The assumption is when you add negative feed back to make a closed loop, you lower the output impedance accordingly as well as lower the distortion. That is true to the degree there is open loop gain left to do those things at what ever frequency it is.
If one connects a capacitance across an amplifiers output and drives it with an impossible to follow signal like a square wave, theoretically what one would see is the square wave rounded off in an R/C low pass filter (amplifier output R and load C).
In reality, normally what one gets is a ringing square wave showing not a simple but a more complex and reactive source, showing an amplifier over shooting and damping often with a definable Q.
In my own fooling around, what found was if one made an amplifier with a low output Z without -feed back, it did behave like an R/C.
I think what one can say is in a closed loop reactive loads can use up the open loop gain that normally gives the good measurements.
How big is this stuff?? I don't know but at least with an amplifier, it's possible to set up a null test where one can listen to the difference between the input signal and output signal, much harder with loudspeakers but the generation loss test works.
Tom
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: What makes a driver High Efficiency? - tomservo 07:03:48 05/31/23 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
