What is meant by damping factor and why is it important

[tomelex]

the conclusion could be, that the speaker voice coil impedance (and mechanics) is the biggest factor (by a wide margin) in stopping the resonance condition, the speaker leads and amp output impedance coming in second, atleast through the lower range of frequencies, where we are usually concerned with base response and resonance, in short, mostly, it is the mechanical design of the speaker resonance, resistance, etc, is what causes it to flap about at resonance.

A SET amps higher output impedance plays with the FR, as well as generating a more complex harmonic structure from the very design of the SET itself. The simple ideal goal would be to stop all power going out to the speaker at its resonance point, or reduce it as it approaches resonance, the SET amp reduces its output power, the solid state amp reduces voltage. SET tubbiness at low frequencies is about harmonic distortions and poor output transformer design, the better the output transformer, the less the harmonic distortion at low frequencies and the "tighter" the bass due to that alone.

Output impedance does not "grip" the speaker to any extent, and you don't hear that, you hear FR variation. It is complex but at the very heart of amp speaker interface. Dons chart is instructive as is referenced a the post before this one though the solid state amp would have more FR variations than his model showed IME. Keep in mind that modeling complex speaker loads is not easy and there are way many variables in a real world measurement, which means every model is a model unto itself, Dons are accurate to the model speaker he created so to speak.

 

[Sal1950]

I really struggle to understand why speakers with passive crossovers are still being sold.

On active speakers, I would guess the majority of audiophiles want to get their own amplifiers and will always question any internal amps or manufacturer's choice, so there is market resistance,

That resistance will probably be extreme! Wide spread acceptance would mean the death of a large portion of High End audio and the loss of huge sources of advertising dollars.
From speakers like Kii 3 to the new Klipsch The Fifteen which has inputs for anything you can think of including phono, all you end up needing is the source component. Not good for commerce is a quote I've heard thrown around.

 

[DonH56]

the conclusion could be, that the speaker voice coil impedance (and mechanics) is the biggest factor (by a wide margin) in stopping the resonance condition, the speaker leads and amp output impedance coming in second, atleast through the lower range of frequencies, where we are usually concerned with base response and resonance, in short, mostly, it is the mechanical design of the speaker resonance, resistance, etc, is what causes it to flap about at resonance.

The design includes speaker (driver) and cabinet parameters in addition to crossover and so forth. The resonance in the bass is typically that of the driver interacting with the cabinet (ported or sealed).

"Stopping" the resonance requires adequate control of driver (cone, panel, whatever) movement so it faithfully follows the input. That is what led me to design my own subwoofer back in the early 1980's. That and I couldn't afford one of the big amps and a suitable amplifier of the day to drive it... I had to figure out another way to get a sub that would blend with my planar dynamic speakers. Sometimes it pays to be an EE...

Keep in mind that modeling complex speaker loads is not easy and there are way many variables in a real world measurement, which means every model is a model unto itself, Dons are accurate to the model speaker he created so to speak.

Good reminder. All my life I've been plagued by models that are not real enough to model what I want to see. Whether Hz, kHz, MHz, GHz, THz, models are always very hard to get right. Speaker models are challenging because you have to get not only a good electrical model but also the transfer function from electrical to acoustic right. Way back when I made a bunch of measurements with a VNA to get electrical parameters, then used a B&K measurement mic to see how the electrical and acoustic responses corresponded. I got pretty friendly with the professors who controlled access to the anechoic chamber...

 

[tomelex]

After reading Don's considered and respected response and what I wrote, I need to be clear about this, as I don't think I was too clear

given a steady amplitude input sinewave, the SET amp, when the speaker impedance increases, there is less output from the speaker, it provides less power to the speaker, and the typical solid state amp, when the speaker impedance increases, it provides the same voltage to the higher impedance, so less drive to the speaker. A SET amp is more a power drive, a solid state amp is more a voltage drive. Less amplitude variation is seen at the speaker with the solid state because its output impedance is like almost zero ohms.

 

[RayDunzl]

I don't think I was too clear

I don't think the above any clearer.

 

[DonH56]

After reading Don's considered and respected response and what I wrote, I need to be clear about this, as I don't think I was too clear

given a steady amplitude input sinewave, the SET amp, when the speaker impedance increases, there is less output from the speaker, it provides less power to the speaker, and the typical solid state amp, when the speaker impedance increases, it provides the same voltage to the higher impedance, so less drive to the speaker. A SET amp is more a power drive, a solid state amp is more a voltage drive. Less amplitude variation is seen at the speaker with the solid state because its output impedance is like almost zero ohms.

Hmmm... As output impedance rises the amplifier will "look" less and less like an ideal voltage source. The complete opposite would be an ideal current source but that would be a pretty unrealistic amplifier (some current-mode amplifiers excepted). Power is the product of voltage and current so 100 V and 1 A and 1 V and 100 A is the same power (100 W). Whilst power for the same voltage will drop with impedance (P = V^2 / R), meaning the power supplied to the speaker drops, to determine if the speaker's (acoustic) output drops you need to know more. For example, if the system is resonate at a particular frequency, then depending upon the design the impedance might spike upwards and so it takes much less power to produce the same (acoustic) output. Other resonances go the other way, producing a null in output, so it takes more input power for the same output SPL.

The design of a speaker system means looking at all the parameters and how the driver functions in the box with a given crossover network. You have to make everything work together. I am not a speaker designer, but the ones I have interacted with in the past generally start by assuming an ideal voltage source because that is how most amplifiers behave, at least to first order, then use models of real amplifiers and then the amplifiers themselves to perform final voicing of the speaker system. A tube amplifier typically has much higher output impedance than a typical SS amplifier so if you want your speaker to behave with a tube amp you have to make it look like a pretty constant load -- or voice it to sound like you want when driven by a tube amplifier. One reason Maggies work well with tubes is because the impedance is very nearly flat over frequency and almost purely resistive. Most conventional speakers have large peaks and valleys in their impedance and you have to decide of the resulting frequency variation matters or not. In some cases it really doesn't matter, and in others it may help determine the sound you want (or not). That also means that, for some speakers, a SS amp may actually produce a less-flat frequency response because the designer "voiced" it for a particular amplifier (tube or whatever).

SET's generally have limited dynamic range, making them most suitable for extremely efficient speakers. Those are often horn-loaded compression drivers, which are among if not the most efficient at converting electrical input to acoustic output. They also tend to produce among the lowest distortion for a given SPL, natch. But there are trades, of course, everything is a compromise.

"It's complicated."

 

[fas42]

IOW, amplifiers are not "perfect", not by a long shot - I've only come across one amplifier, in 30 years, that might be able to wear a badge saying that, without looking foolish ...

 

[tomelex]

darn, ok, emitted stuff and added stuff,

given a steady amplitude input sinewave, the SET amp, when the speaker impedance increases due to resonance, it provides less power to the speaker, and the typical solid state amp, when the speaker impedance increases, it provides the same voltage to the higher impedance, so less drive to the speaker which is at some resonance and therefore on its own wanting to put out more output. A SET amp is more a power drive (max transfer of power when source and load equal, in case of tube output being at several ohms compared to solid state at near zero...so tube amp "tiny bit"more a power source when compared to zero output impedance solid state amp which is a voltage source), a solid state amp is more a voltage drive because less amplitude variation is seen at the speaker with the solid state because its output impedance is like almost zero ohms

 

[DonH56]

I don't know what "power drive" means in this context; I use terms differently. Sounds like a marketing term for a pickup truck.

With a high-impedance load the SET and conventional SS amplifier will actually be closer to producing the same power output since the SET's higher output impedance will have less impact on the voltage across the speaker terminals. Either/both produce less power into a higher impedance at the same voltage. For audio circuits, by and large, maximizing power transfer is rarely a design goal, tube amplifiers using tapped output transformers the notable exception.

P = V^2/R = I^2*R

I do not know much about current SET design parameters so am not really sure what a typical SET output impedance and current capability might be. The handful of schematics I have seen are all over the map. I keep thinking I should produce a MOSFET single-ended class A amplifier and call it the solid-state SET, SSSET, but then sanity returns. Too many times nostalgia has endowed magical, mystical properties to gear I owned decades ago, and then when I manage to hear it again the magic is gone and I realize things really are better now. Not just audio gear... My grandmother was found of saying that those who long for the good old days didn't have to live through them. She also said whoever came up with the phrase "slept like a baby" never had one.

 

[Thomas savage]

Thanks for the excellent contributions you have all made in this thread , I really appreciate it

 

[tomelex]

look here:

http://www.transcendentsound.com/Amplifier_Output_Impedance.html

 

[stunta]

Just get active speakers so you can stop worrying about it.

Setting aside mass-market speakers, why don’t high end manufacturers make speakers with external crossovers in a box so people can still use any amp they want? ATC even makes passive pro audio speakers which is hard for me to understand..

 

[DonH56]

I suspect the folk who buy high-end loudspeakers are least likely to be competent to design their own crossovers and the manufacturers most likely to not want to kill the mystic that they alone have the secret sauce to audio (crossover) nirvana... That said there are a few, like Sanders, that provide an external DSP crossover you can tweak to your heart's (and mind's) content.

 

[Thomas savage]

Setting aside mass-market speakers, why don’t high end manufacturers make speakers with external crossovers in a box so people can still use any amp they want? ATC even makes passive pro audio speakers which is hard for me to understand..

I belive Vivid Audio give this option now.

 

[stalepie]

Is there any software that can simulate the effects of different output impedances? Or are there recordings that compare how different speakers sound when plugged into amps with different damping factors?

 

[Cosmik]

Is there any software that can simulate the effects of different output impedances? Or are there recordings that compare how different speakers sound when plugged into amps with different damping factors?

I guess that a system with a good damping factor might be able to play a recording/simulation of one with a poor one, but not vice versa. If so, the question becomes: why not just build all systems to have good damping factors?

 

[Wayne]

Just get active speakers so you can stop worrying about it.

@watchnerd: By "active speakers" were you referring to speakers with built in amplifiers AKA "powered speakers" and/or were you referring to the type of crossover or ??

Thanks

 

[Wombat]

Also, the SET guys are also not believers in high damping factor.

Add a 1 to 3 ohm resistor(suitably rated) between your SS amp and 8ohm speakers and you will get some tube amp effect. Tube amps of the past used 16ohm speakers for better damping although multi- tap OPs could achieve this for other driver impedances.

 

[tomelex]

Add a 1 to 3 ohm resistor(suitably rated) between your SS amp and 8ohm speakers and you will get some tube amp effect. Tube amps of the past used 16ohm speakers for better damping although multi- tap OPs could achieve this for other driver impedances.

True, some SET amp effect, but not very much in reality. The SET amp behavior is much more complex, and dynamic. These things make them fun to listen too. It is true that if you listen to he SET then say a decent solid state amp, you will notice difference, but personal preference will decide which you prefer, often folks find the SET amplifier more dynamic.

SET amps and output transformers have come a long way from your grand dads tube radio receiver (which many of them actually sound quite nice) while retaining the essential elements of the SET such as ultra low distortion at low power levels (where your music spends most of its time) and dynamics due to the tube/transformer/speaker interaction and what I call the chorus effect sound, kind of like reverb but not reverb.

Good SETs produce very few harmonics higher than the fourth, and that reduce IM quite a bit, but they make up for that by producing a whole bunch of more close in tones so in some ways its a wash.

Also the group delays contribute in some SETs to a "fat" sound which can be quite pleasing. And these units can be made with no feedback, where only some solid state amps can do that, and they have to separate the audio signal in to positive and negative halves in order to do that, which is never really ultimate high fi, more hi fi than a SET, yes, but not ultimate.

 

[Cosmik]

These things make them fun to listen too. It is true that if you listen to he SET then say a decent solid state amp, you will notice difference

Noticeable that you are listening to the amp and not through it. I think I am only interested in listening through a hi-fi system.
I think that a good hi-fi system can actually let you do this.