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tonality modulation and
cubic exponentiation of distortion levels
Most speakers are to be driven from a low impedance. Crossovers are designed that way. Woofers resonate at a certain frequency where the impedance gets high. Driving from a current source will produce much more output power at this frequency. So driving from a poorly damped valve amp will change the frequency response. Simple as that.
tonality modulation and
cubic exponentiation of distortion levels
Most speakers are to be driven from a low impedance. Crossovers are designed that way. Woofers resonate at a certain frequency where the impedance gets high. Driving from a current source will produce much more output power at this frequency. So driving from a poorly damped valve amp will change the frequency response. Simple as that.
Solid state fans can start with their amplifier which has a damping factor (DF) of perhaps 50, 100, or 200 . . . DF, referred to an 8 Ohm load.
Then, they can take a resistor with one end connected to the Red output terminal of the amplifier, and the other end of the resistor connected to the Hot lead of the speaker cable (resistor in series with the speaker load).
Examples of approximate damping factors they will get, referred to an 8 Ohm load:
A 1/2 Ohm resistor gives a damping factor of 16
A 1 Ohm resistor gives a damping factor of 8;
A 1.66 Ohm resistor gives a damping factor of 4.8. At this point, the power output to the 8 Ohm speaker, is 1/2 of the original amplifier power.
A 2 Ohm resistor gives a damping factor of 4;
A 4 Ohm resistor gives a damping factor of 2;
An 8 Ohm resistor gives a damping factor of 1 (Unity). At this point, the power output to the 8 Ohm speaker, is 1/4 of the original amplifier power.
Start the listening test with moderate volume, and no resistor. Then, turn the volume up, the higher the resistance, the higher the volume to match the reference of the sound that you got with no resistor.
Late Edit:
* * * I have tried it a number of times over the years, on solid state amplifiers, and tube amplifiers, and different speakers.
Caution: many tube amplifiers can work with an 8 Ohm series resistor; But some can Not.
Damping factor . . . What would you like it to be?
Decide on a DF number, and insert the resistor; listen.
Try it, just to see what it sounds like on Your Speakers.
Note: From 20Hz to 20kHz, at some frequencies, many "8 Ohm speakers" impedance varies from much less than 8 Ohms to much more than 8 Ohms.
Have Fun!
Then, they can take a resistor with one end connected to the Red output terminal of the amplifier, and the other end of the resistor connected to the Hot lead of the speaker cable (resistor in series with the speaker load).
Examples of approximate damping factors they will get, referred to an 8 Ohm load:
A 1/2 Ohm resistor gives a damping factor of 16
A 1 Ohm resistor gives a damping factor of 8;
A 1.66 Ohm resistor gives a damping factor of 4.8. At this point, the power output to the 8 Ohm speaker, is 1/2 of the original amplifier power.
A 2 Ohm resistor gives a damping factor of 4;
A 4 Ohm resistor gives a damping factor of 2;
An 8 Ohm resistor gives a damping factor of 1 (Unity). At this point, the power output to the 8 Ohm speaker, is 1/4 of the original amplifier power.
Start the listening test with moderate volume, and no resistor. Then, turn the volume up, the higher the resistance, the higher the volume to match the reference of the sound that you got with no resistor.
Late Edit:
* * * I have tried it a number of times over the years, on solid state amplifiers, and tube amplifiers, and different speakers.
Caution: many tube amplifiers can work with an 8 Ohm series resistor; But some can Not.
Damping factor . . . What would you like it to be?
Decide on a DF number, and insert the resistor; listen.
Try it, just to see what it sounds like on Your Speakers.
Note: From 20Hz to 20kHz, at some frequencies, many "8 Ohm speakers" impedance varies from much less than 8 Ohms to much more than 8 Ohms.
Have Fun!
Last edited:
baudouin0,
I absolutely heard differences, in frequency response, woofer damping, and distortion.
All done with my youthful ears, and my opinions. I never did a dbt for these 'tests'.
dbt is extremely difficult, if not impossible.
How do you set up the volume to make the sound levels the same, you can not, because of the changes to the frequency response versus damping factor.
Same sound levels at some, and different sound levels at other frequencies.
Your Mileage May Vary.
In fact, Your Mileage Will Vary (YMWV).
You have different amplifiers, different speakers, and different ears.
Again, Have Fun!
I absolutely heard differences, in frequency response, woofer damping, and distortion.
All done with my youthful ears, and my opinions. I never did a dbt for these 'tests'.
dbt is extremely difficult, if not impossible.
How do you set up the volume to make the sound levels the same, you can not, because of the changes to the frequency response versus damping factor.
Same sound levels at some, and different sound levels at other frequencies.
Your Mileage May Vary.
In fact, Your Mileage Will Vary (YMWV).
You have different amplifiers, different speakers, and different ears.
Again, Have Fun!
For the last couple of years I've been routinely adding 10 ohm to my class-D amps. Very simple. Kills the power -- but hey, what else am I going to do with 99.5 excess watts? And if you do the Ohm's Law, you can see that the amplifier runs a lot cooler as well when it's only loaded with 18 ohm. The kids are small; the WAF's hearing is extremely acute; I dream of a small 5W class A MOSFET with nutube pre.
It smooths out the highs for the CHN-50 and Alpair 5. The h.f do get turned up slightly, which is a slight downside because they're already quite bright, so it's not actually the point. The point is the reduced harshness when they start hitting their limits with break-up modes. Hence, more tubey.
Sorry, my Post 104 had a calculation error in it:
It started with SS amplifier with a damping factor of at least 50.
Then I calculated numbers for different series resistors between the amplifier Red output terminal, and the Hot of the loudspeaker cable.
My Mistake:
I wrote: A 1.66 Ohm resistor gives a damping factor of 4.8. At this point, the power output to the 8 Ohm speaker, is 1/2 of the original amplifier power.
That is incorrect.
The correct numbers, for a series resistor is more approximately:
Series resistor 3.3 Ohms, Damping Factor 2.42, and the maximum output power is 1/2, Versus the amplifier's maximum output power when there is no series resistor.
I do not know of a way to edit that post, more than 1/2 hour from the original post.
Thanks!
It started with SS amplifier with a damping factor of at least 50.
Then I calculated numbers for different series resistors between the amplifier Red output terminal, and the Hot of the loudspeaker cable.
My Mistake:
I wrote: A 1.66 Ohm resistor gives a damping factor of 4.8. At this point, the power output to the 8 Ohm speaker, is 1/2 of the original amplifier power.
That is incorrect.
The correct numbers, for a series resistor is more approximately:
Series resistor 3.3 Ohms, Damping Factor 2.42, and the maximum output power is 1/2, Versus the amplifier's maximum output power when there is no series resistor.
I do not know of a way to edit that post, more than 1/2 hour from the original post.
Thanks!