Damping factor

[Paul C]

"If your speakers are demanding, would it help to add a "zobel" circuit to flatten the imperdance and would this give a low df amplifier a lighter load?"

No.

Zobel's flatten the impedance curve, but that is to make the crossover react more consistently.

Weak tube amps have trouble with some speakers because they are tube amps, just the nature of the beast.

I will never be convinced that tube amps sound better than solid state. Is there a difference in sound? Yes. When a tube amp is driven into distortion, that distortion has a less objectionable sound than when a solid state amp clips. But the rest of the time, no, it doesn't sound better. I know some disagree, after all, they paid thousands for their tube amps. They must sound better, right? :saywhat:

 

[Grainger49]

I haven't read through the whole thread, maybe this is redundant.

Damping factor is defined as the ratio of the output impedance to the speaker impedance. That is a DF of 100 @ 8 ohms is an output impedance of 0.08 ohms.

More specifically the higher the damping factor, the better the amplifier can stop a woofer from cycling when the sound has stopped. That is, no overhang in the bass.

Maybe hat helps, maybe not.

 

[crooner]

A very high damping factor is almost always an indication that gobs of negative feedback are used in the amplifier. Not good.... :nono:

 

[theophile]

Mhardy and Grainger nailed it.

Damping factor is simply a ratio betweem output impedence of the amp and the impedence of the speakers.

Nothing more,nothing less. :yes:

Axel mentioned the Kenwood amps with Sigma Drive.My Basic M2 is one of those amps.I'm pretty sure it has a damping factor of 1000.
O.K. that is simply a number,and what we listen to is music not numbers(digital excepted ).However,what I will say is the Kenwood Basic M2(not the M2A,it didn't have Sigma Drive :thumbsdn: )has a level of bass subtlety(along with definition,oomph,detail etc)which is simply astounding,a real eye opener! :yes:
I'd love to hear something which does a better job,but there's nothing to complain about with the M2. :thmbsp:

 

[Kegger]

I will never be convinced that tube amps sound better than solid state. Is there a difference in sound? Yes. When a tube amp is driven into distortion, that distortion has a less objectionable sound than when a solid state amp clips. But the rest of the time, no, it doesn't sound better. I know some disagree, after all, they paid thousands for their tube amps. They must sound better, right? :saywhat:

Actually I've got some pretty cheap tube amps that sound better then most solid state to.
And they do sound different then solid state even when not clipping.

 

[Kegger]

Axel mentioned the Kenwood amps with Sigma Drive.My Basic M2 is one of those amps.I'm pretty sure it has a damping factor of 1000.
O.K. that is simply a number,and what we listen to is music not numbers(digital excepted ).However,what I will say is the Kenwood Basic M2(not the M2A,it didn't have Sigma Drive :thumbsdn: )has a level of bass subtlety(along with definition,oomph,detail etc)which is simply astounding,a real eye opener! :yes:
I'd love to hear something which does a better job,but there's nothing to complain about with the M2. :thmbsp:

Just curious if you've opened up both the m2 and the m2a?
I can't remember for sure if I have but thought there was little if any diiference inside.

And yes you are correct both the m2 and m2a have a rated damping factor of 1000 at 50hz.

 

[crooner]

Ideally you should never hear your amps clipping. If you do, you are most likely underpowered. That's the beauty of high power solid-state, clipping is virtually eliminated.

I remember my Dynaco Stereo 70 clipping and it reminded me of a worn out record at the inner grooves. Tons and tons of even order harmonics. Very objectionable, IMO.

Actually I've got some pretty cheap tube amps that sound better then most solid state to.
And they do sound different then solid state even when not clipping.

 

[wineslob]

Ideally you should never hear your amps clipping. If you do, you are most likely underpowered. That's the beauty of high power solid-state, clipping is virtually eliminated.

I remember my Dynaco Stereo 70 clipping and it reminded me of a worn out record at the inner grooves. Tons and tons of even order harmonics. Very objectionable, IMO.

That will never happen. A clipping amp produces all kinds of nasty distortion. A S.S. amp will produce more "bad" distortions than a tube amp, and will take out a speaker in a milisecond, I've done it, in my younger days.\

As far as DF, the article worked with dynamic load speakers, with Apogees, Maggies, and other resistance load speakers, DF is more critical for keeping those large diaphrams in control.

 

[Kegger]

Ideally you should never hear your amps clipping. If you do, you are most likely underpowered. That's the beauty of high power solid-state, clipping is virtually eliminated.

I remember my Dynaco Stereo 70 clipping and it reminded me of a worn out record at the inner grooves. Tons and tons of even order harmonics. Very objectionable, IMO.

Never had even a hint of clipping on any tube amp I've used.
Put them in the right situation and no issues.

40 watts of tube power on a decent impeadance load, 90db speaker or higher and your fine.

Damping factor hasn't been an issue either, most vintage speakers are a pretty friendly load.

If you have a difficult load then yah you generally better get a balsy solid state amp.
(Hense why I have the big kenwoods)

 

[jtgofish]

All these posts highlight the arse about nature that is modern Hi Fi.In the 60s and earlier low powered tube amps were the norm so speakers had to be efficient and easy loads.Then came transistors and speakers had to be built to handle power and this is when they started to sound bad.
Anybody who says that transistor amps sound better than tubes simply has not heard the magic synergy between efficient speakers and tube amps.You cannot expect tube amps to sound good on modern mainstream speakers.But on the right speakers the relative inferiority of transistors becomes obvious.
Todays speakers are the automotive equivalent of a car that weighs 4 tons/tonnes and then needs a massive engine to power it.You are never going to match the performance of a light car with less powerful engine but an equivalent weight to power ratio.And this is the beauty of efficient speakers-they are very responsive,nimble and dynamic sounding[less smeared if you like].
But the whole industry has been hijacked by power output/handling performance because it is an easy concept to market even to the most stupid.And which country led it down this path of Hummeresque excess where More Has Got To Be Better is enshrined in its Constitution?

JT

 

[tcdriver]

The BEST Damping factor

The best damping factor for any given situation depends on what you are driving. When good speaker designers design a speaker one of the factors they take into account is the ability of the amplifier to drive the speaker. Many designers assume that the amplifier will have a reasonably high damping factor because most modern solid state amplifiers do have high damping factors.

If one designs a loudspeaker for use with a tube single ended low damping factor amplifier, then one will probably design an over damped speaker. The amplifier's low damping will then interact with the over damped speaker to give the optimum sound. A high damping factor amplifier will not sound as good on this type of speaker.

Back in the day, (mid-fifties), many high quality amplifiers came with a damping factor control that would allow the user to adjust the amplifier damping to best match the speaker they were using. What a brilliant idea.

 

[markn2wae]

Poor DF like air in the brake line.

Think of damping as back pressure in your cars exhaust system.

Another analogy to car systems-

Think of the amp. as the master cylinder and the brake(s) as the speakers and the speaker lines as the brake lines.

If you have air in your brake lines, (poor damping factor and\or too small a speaker wire gage) the brakes apply sluggishly (or not at all!), but when you bleed all the air out and of course fix the leak(s), the brakes apply firmly and responsively. (good damping factor and \or heaver speaker lines).

My experience with the speaker line issue was "back in the days" when I used anything I could get for speaker wire it was used, I thought four conductor phone wire was great, two wires for each speaker and a nice neat "run" to the back of the amp.

I went to 14 gage wire when I heard a friends stereo and it was great sounding (same speaker types and sizes, same power rating amps etc.).

Now I don't use anything smaller than #12 wire unless it is for small "bedroom" systems and\or short runs. (4 feet or less).

Mark T.

 

[crooner]

It might never happen in your particular setup but tube amplifier clipping is not at all uncommon. I remember driving my MC275 to clipping numerous times. Speakers were 89 dB SPL in sensitivity, not terribly inneficient. And that thing was a powerhouse in tube amplifier terms!

That will never happen.

 

[crooner]

It depends on how well behaved the amplifier is at the point of clipping. Poorly designed units will indeed produce nasty distortion artifacts. The state-of-the-art designs of the 1970s are quite stable in this regard. Then we have McIntosh's Power Guard which works very well indeed.

However, having tons of power in reserve will effectively safeguard against clipping, even without Power Guard...

n. A clipping amp produces all kinds of nasty distortion. A S.S. amp will produce more "bad" distortions than a tube amp, and will take out a speaker in a milisecond, I've done it, in my younger days.\

 

[theophile]

Just replying to a Question of Kegger's.

Kegger,
I've had a quick look inside both without the advantage of having both side by side,and many months apart.Given that qualification,I'd say that 99% of parts are common to both the M2A and M2.The obvious difference is the Sigma Drive which is design-wise,all to do with the negative-feedback loop.

It would need a service manual for the respective circuit diagrams to reveal just how complex or otherwise Kenwood went with this idea. :scratch2:
One would have to think that they weren't too happy with it(or it cost too much),however it was used in a lot of their statement products of the time.
On the note of tube amp clipping,there was an article in the abso!ute sound magazine in the 90's concerning tube amp power compared to solid state by a fellow with a German sounding name.He measured and showed graphs and concluded that tubes are more powerful.I would refer those who are curious to go to the TAS website and do a search or send them a e-mail.

 

[Kegger]

Theophile, thanks!

I thought they were pretty much the same except that feedback deal/wire that runs to the speakers.
I had heard of some having issues with it and being hard to repair, that would be my guess why they/
kenwood quit using it, probably more user error then anything else, but none the less.

Thanks.

 

[wineslob]

It might never happen in your particular setup but tube amplifier clipping is not at all uncommon. I remember driving my MC275 to clipping numerous times. Speakers were 89 dB SPL in sensitivity, not terribly inneficient. And that thing was a powerhouse in tube amplifier terms!

What I was refering to was the statement that a solid state amp will "virtually" eliminate clipping. That is simply not true. Any amp can be driven into clipping (Flame Linear, anyone?). I have never seen an amp that was well behaved when clipping. Now with MacIntosh the clipping is almost eliminated and kept under control with the sound guard circuitry. Very few amps employ such designs (soundcraftsmen was another). Yes a better built amp will behave better at clipping than others, but I wouldent want to bet my speakers on it. As far as tube amp clipping, you are correct, at clipping a tube amp is "softer".
One other interesting note, the new ICE based amps in this reguard are very delicate, and will die in a flat second. At least from the owners that have reported such things.

 

[crooner]

Let's not confuse amplifier instability due to oscillation with actual clipping. I believe the first Phase Linears were unstable at all signal levels and many times well below clipping. Early quasi-complementary output circuitry and low beta cutoff power transistors were responsible for this. These shortcomings were solved by the late 1970s.

That said, the higher power you have available the less likelihood you will encounter hard clipping. Also, having the treble control boosted on your preamp will certainly mean death to your tweeters if you clip the amplifier. One good reason not to use tone controls at all. I don't...

As for Power Guard, there's no clipping whatsoever when using it, a reason why McIntosh refused for many years to reintroduce tube amplifiers...

 

[wualta]

This quick experiment may help conceptualize woofer damping a little. You can do it if you have a spare high-compliance woofer lying around somewhere, the bigger the cone the better. Something designed for a sealed box is ideal.

Tap the woofer cone and watch it bounce. Now short the woofer terminals with a screwdriver or a clip lead and tap the cone again. In some cases the cone will appear to be stuck and will barely move at all.

An amp with a very low output impedance will act like that dead short across a woofer-- or it would except for that @$%&#! pesky passive crossover, may its name be erased.

By doing this experiment you can get an idea of the amount of control an amp has over a woofer, but you can also guess that there won't be much if any audible difference (with modern speaker systems) between an amp with a DF of 100 and a DF of 1000, just as there's not much difference between a dead short and .001 ohm and not much difference between that and .01 ohm. They're all pretty [we could say asymptotically] close to a dead short.

Add in the series impedance of a cheap passive crossover with tiny-gauge coils and you could probably make that range go from 10 to 1000. You begin to see why some people are attracted to electronic crossovers and biamping.

Of course, if you're a speaker designer and know what kind of amp will be driving your speakers, you can design the two to work together, as has been mentioned in connection with tube amps in the First Golden Era, the 1950s. But people, being the perverse creatures they are, will want to connect up their favorite random amp. In that case, designing in high self-damping (bigger magnet, lower DCR voice coil) isn't a bad idea. You can always flabbify a woofer with series resistance (really skinny speaker wire, really horrid cheap crossover) if you want to, but going the other way isn't as easy.

Just some random thoughts from a chronically random person.

 

[crooner]

Great post Wualta, thanks for sharing!