Damping Factor: What is it & is it Important?

[@gregorykellerman3876]

I've given this a bit of thought recently because of claims that people make about amplifiers 'sounding' different. One thing that comes to my mind is the effect of amplifier compensation. It seems that applying that at the voltage gain stage tends to use up the 'headroom' of the differential amp. I'm guessing that is why distortion rises at higher frequencies. It seems then since this lowers feedback at higher frequencies that the output impedance would necessarily rise too. Hence the 'different' sound of amplifiers. While I'm on the subject it seems to me that since bipolar transistors have large swings in current with minor changes in voltage, they would give a lower output impedance since they don't need the voltage feedback thru the loop like an FET. BTW, a most excellent and informative video. Signed, an audiophile from the 70's. Also, I'd welcome any feedback. :-) KC9WVR

[@andybonneau9209]

Dueling audio files. Nice! Very interesting subject Tony.

[@davidocampoi9602]

The best explanation about Damping Factor. Thanks Tony.

[@southerner66]

I once worked on a guitar amp that presented with a strange distortion problem. The input to the output stage was clean, but the output signal had an unusual distortion component clearly visible on a scope. It turned out to be a cone resonance coming from the speaker at certain frequencies that was reflected back through the output transformer. It looked at first like the problem originated in the output stage, but it was generated by the speaker itself. The cone had softened with age. And the guitar amp had no NFB around the output transformer, so there was not much the amplifier could do to damp this speaker cone resonance. You could feel the speaker cone doing this with your hand like a ripple on the surface. A new speaker of the same type made the problem disappear. This is also one reason why there's a certain dynamic synergy between tube guitar amps and particular speakers.

[@petertimp5416]

Great explanation. Thanks😊

[@HameshBhirgoo]

Thank you very much Sir for your time and explanation on this subject.

[@Bassotronics]

When I was a lil lad, I used to take a LED bulb, connect it to the speaker terminals, tap the cone and watch the LED light glow.

[@unclewilbur8976]

Awesome video. There was a LOT of information explained here!!! I understood a small percentage of this. But this small % of learned information was significant!!!! I understand some things much better!!! Now if I could understand all of this I’d be so happy.

[@alfonsodelafreg259]

I have constructed bass modules with dual voice coil drivers. The second voice coil is used, with a shorting resister, to dampen the driver. Works quite well to clean up the response.

[@rebootedelectronics]

Good info, Tony! I remember struggling to solve an issue with a Pioneer SX-880 that would go into protection any time the volume control went near or over the 12 o'clock position. I noticed that if you turned on Loudness or the bass hit hard, it would trigger at considerably less than that. I figured the main filter caps must be going bad and causing clipping. To my surprise, the power supply checked out fine, bias and DC offset were reasonable, and it produced full output wattage with a 1kHz test tone into 8 ohm dummy loads without ever triggering the protection circuit. However, the second you hooked speakers up to it and played music, the DC offset was all over the place. That led me down a learning rabbit hole about damping factor and I was eventually able to get it working properly again by replacing pretty much all of the transistors in the output stage. I'll admit, I took a little bit of the shotgun approach, but I had already replaced the electrolytic caps and tested everything else in the output stage. Anyway, this video is a much better explanation than what I learned back then. Thank you!!!

[@User0207-l6g]

A viewer for many years, thanks for sharing your vast knowledge of electronics and vintage audio equipment. As a side note, the quality of your videos is more than adequate for purpose, keep up the good work and don't focus upon the negative comments that frequent the interwebs. I was wondering if you could, or perhaps already have compiled a listing of transistors, varistors, diodes, etc. that are currently available to the vintage audio restorer that should be stockpiled. As the industry continues its migration to surface mount components it is becoming increasingly difficult to source electronic components needed for vintage audio repair. Identifying and stockpiling these components is essential if the hobby is to continue. Some items I have recently encountered are; 1) 1S1211 & 1S2076 diodes (rumored replaceable with 1N4148); 2) 2SC853 (NEC transistor). Thanks again and keep up the good work.

[@Wil_Bloodworth]

You beat me to it... I was just going to start working on a video about damping factor. I'm honestly glad you put it out before me.

[@jerryrevellame50]

nice explanation thankz

[@paulb4661]

Excellent episode, thank you! As a side note though, moving mass increase (Mms) lowers the damping, not the other way around. Damping of fundamental resonance is the product of the motor strength related damping (Qe) and suspension related damipng (Qm). In both of corresponding equations, the moving mass is in the numerator.

[@Dutchamp]

Very interesting you are very good to explain it in understandable language. This isnt easy matter

[@paulschreuder4211]

Dampingfactor sticky! Great video Tony.

[@kenielsen]

Excellent👌

[@sguttag]

I work in cinema and when wiring surround speakers, we try to avoid any series strings because it will crush damping factor, which results in a muddy/sloppy bass. If you wire two 8Ω speakers in series, each speaker has, effectively, an 8Ω resistor in series with it. You also tend to get a less efficient system as the power output of a solid-state amplifier into 16Ω is going to be less than into 4Ω (if you wired in parallel). Most modern commercial amplifiers will work down to 2Ω (typically with an increase in some THD). So, for 8Ω speakers, I'll wire 4-5 in parallel before introducing a series-parallel string (some amps, most notably, the QSC DCA 1222 will work down to 1.6Ω). For a 6 speaker string, I'll wire 3 in parallel, another group of 3 in parallel and then series the two groups. That only puts a 2.7Ω impedance in series with any speaker. Not ideal but for surround speakers, certainly workable and leaves you with 5.3Ω to the amplifier, which is in its sweet spot of power/THD. Naturally, one can add more amplifier channels to avoid the series but few exhibitors would want to spend the extra money. I might add...that is an interesting driver you have there. Front vented with a whizzer cone "tweeter."

[@paulb4661]

An 8ohm nominal impedance woofer in a an enclosure will be a much more demanding load for a class AB amplifier than this. You can approximate actual power dissipation of output devices by multiplying impedance modulus at a chosen frequency by the cosine of the phase angle and then squaring the result. You are basically trying to source or sink large current with the output voltage approaching 0.

[@Obsfucation]

On the other end of the spectrum is what we do in Dolby Atmos cinemas: each of the surround speakers (

[@sguttag]

@@Obsfucation Yeah, same here. Most of the surround speakers we use for Dolby Atmos are 4Ω speakers too. The Dolby DMA can be a handy amplifier though almost all of our systems are Q-SYS based so we use DPA-Q and now CX-Q amplifiers, which come in 4 and 8 channel varieties. So, they take about twice as much rack space as a 32-channel DMA but they also handle more power and provide better protection to the speakers. I've had some issues with Dolby's AES67 implementation with "others" (e.g. Q-SYS) as opposed to just keeping it all in-house Dolby. It's nice to find another Cinema person on Tony's channel...one of the best on KZbin, in my opinion.

[@Obsfucation]

@@sguttag Actually, I'm now retired and living in Panama.

[@PossibleAudio]

That's really cool Tony. A lot for me to take in. Answers many questions concerning speaker control and how the amplifier uses feedback. Thank you!

[@wagsman9999]

Wow. Great explanation. Thank you. The role of feedback makes a lot of sense.

[@Selavylisbon]

Excellent, as usual. I've been following your channel for years and learned so much, thank you!

[@duroxkilo]

amazingly concise information right here :) thanks again mr Tony

[@Alex.M.S.]

Thanks for another very informative video, Tony! It just happens that I ran into this damping factor effect reather by accident when I decided to put suppresion diodes on the output of an amplifier I am modifying and improving. I only added the diodes just because I have seen them used in some old amp designs and I wanted to see what happens but to my very pleasent surprize it made my speakers sound way better and I believe louder too. Before this any beat in the music at high volume would make the speaker pop out very much but now they keep the cone in check and I can increase the volume without much mechanical distorsions from the speakers at the volume I used to listen to and it seems that the bass and vocals are a lot more clean and clear. I am actually blown away how well the speakers perform now, even though they are some old RFT cabinets with cheap QTX woofers in them.

[@danielsamson9505]

This is the whole subject. Thank you.

[@mackfisher4487]

Tony, you would make a great Physics professor or an electrical electrical engineering professor teaching a couple classes of physics. this stuff is fun

[@Satchmoeddie]

1930s. Impedance is an AC function. Permanent magnet speakers came out in the 1920s and were commercially used more and more into the 1930s & 40s. The original suspensions were made from spring steel and they actually did look just like a spider with it's legs flexing the spider's body (the cone) up and down. Cheese cloth was usually glued all across the back of the frame to keep dirt out of the magnet gap. Now we use the concentric pleated cloth or woven fiber disc suspensions but it's still called a spider.

[@Stelios.Posantzis]

Excellent explanation video of how the damping factor affects the loudspeaker behaviour and what its contribution is in the audio chain. Some really obvious facts are laid out that sometimes audiophiles and audio gear enthusiasts forget. It is good to get back to basics and make sure we got these covered with a proper grounding in the subject.

[@greengrayradio1394]

Very good description of damping factor, Tony!

[@welderfixer]

Tony, if had 10 percent of your knowledge and skill I'd be rather dangerous with a soldering iron. Thank you for all you do.

[@mackfisher4487]

Love your old Lincoln welder icon

[@welderfixer]

@@mackfisher4487 Thank you. I repair welders and generators for a living and once in a great while I get one that is in showroom condition, but needs a bit of TLC. I wish everyone would take better care of all of their equipment. All the best to you and yours.

[@meadowlarkaudio7066]

Superior damping is one of two reasons why eliminating the passive filter, and its typically substantial impedance, greatly improves signal tracking. The other is that the filter itself is a resonant circuit. Those are two a several compelling reasons to execute the filter with a digital signal processor ahead of amplification.

[@paulb4661]

Indeed, ended up with a 2.6kG,10mm² flat ribbon air core in series with the LMF to achieve the DCR of 1% of that of the driver coil itself. Cost arm and a leg. Went for a toroidal core for the LF and matched that, despite its 12mH inductance, and at a much more reasonable cost.

[@meadowlarkaudio7066]

@@paulb4661 12mH is a big value. I've put a lot of speakers on the market, and can't recall exceeding 5mH; even that hurts. To a less noticeable extent, the issue is present for MF and HF drivers. For the most part I think we fail to perceive the degradation in those drivers' performance because most guys have never run a tweeter without a passive high pass, or midrange without a passive bandpass, either typically also adds a shelving resistor. So, yeah, lossy and ringy. I think, especially at modest price points for three-ways, that the iffy perception of midrange 'believability' is one of the reasons some guys prefer two-ways. Ideally, you'd want both of those drivers directly coupled to the amp. The other cause for LF wobble is the vented alignment; you're intentionally adding resonance to meet your FA objectives. If not for the need to hit that extension target, ideally you'd want to run a critically damped LF system. But, yeah, you can't put a well damped LF system with a wimpy bottom on the market and succeed at selling it. Happily, the solutions to all of those problems comes quickly to hand by multiamping and running DSP. I haven't designed a speaker any other way since 2012, slammed that door shut. 😊

[@RicardoPenders]

I always love the way you explain things. Very interesting topic.

[@jorgeschmaedecke4629]

The true measurement of damping factor (internal resistance of the amplifier) ​​in solid state amplifiers is done with the negative feedback connected to the voltage amplifier output and not to the current amplifier output (Speaker output). For DC stability of the amplifier one should add a DC servo amplifier to obtain the offset adjustment. In my experience the best results are obtained with amplifiers that are designed in this way.

[@JurgenVonS]

I have an amplifier like that. The sound is very good.

[@pglick123]

Nice class. I have this amp and a pair of old Altecs, so now I know what to do.

[@retroriff]

Nice video Tony. Where it really matters is the type and topology of the device. Solid state or tube and all it's variants. Current gain or voltage gain , devices will better be seen on a spectrum analyzer which is a way better indicator of sound quality in the early design stage. Transfer function is very different in both technologies. Keep up the great work.

[@paulluke-w8p]

Negative Feedback affects the Gain , Bandwith and Distortion of an Amp. More Feedback reduces the Gain and Distortion but increases the Bandwith. Less Feedbach increases the Gain and Distortion but reduces the Bandwidth. Given the small change in signal level when you adjusted the "Damping" Control tells me only a small change was made to to the Feedback . Makes me wonder if this a "Hi-Fi feature" 😄 However you didn't test to see if the "Damping" control affected the Freq Response of the Negative Feedbacb loop. If it does I'd think the "Damping" control was being used to modify the overal Tonal qualities of the Amp.

[@netlogic1ify]

Great video and explanation. I love it ❤

[@jetblakink]

Very very interesting... subbed

[@Douglas_Blake_579]

Nicely done Tony. Very informative. I was hoping you'd show the effect of an 8 ohm resistor across that speaker. It would have demonstrated that almost any damping factor greater than 1 at the voice coil is adequate.

[@xraytonyb]

I made a note of that in the video, but I didn't actually show it. Thanks for the comment

[@SHOGUNofSAIDO]

This is a verryyy long TickTock video. Its worth it :)

[@Slartibartfas042]

I totally agree: It is definitely worth any single second watching! Finally a real good video giving a lot of answers, I never saw here at youtube! Many thanks to Tony!

[@mcgjohn22]

great video. there are some expensive tube amps now with variable damping factor from VTL.

[@Sans_Solo_]

Very good informative video. Thanks Tony. (Like the intro part very much too) Also remember the old trick of connecting two speaker drivers together then pushing in one cone and seeing the other react/move out?

[@dhpbear2]

I guess that damping factor is very low for a tube amp considering it's a high-impedance current-source, unlike a solid state amp being a low impedance voltage source.

[@h1nicolas]

In the circuit diagram, the damping factor switch has two sets of selectors. One set changes the feedback gain and the other set places resistors in the GND return path of the speakers. The resistors placed in series with GND return are 0 ohm (Normal), 0.02 ohm (Medium) the final one is the 0.02 ohm and 0.11 ohm (comprising of two 0.22 ohm, 2 watt) resistor combined in series (0.13 ohm) (Soft). The gain change is most likely used to correct the loss of amplitude by placing these resistors in series i.e. volt drop across GND return resistors. For 0 ohm series resistor, gain is 29.9dB, for 0.02 ohm series resistor gain is 31.5dB and for 0.13 ohm resistor the gain is 35.9dB. Not sure exactly how the switch it connected, but is also seems like the volt drops across the GND return resistors could be part of the feedback. If so, the more current passing through these GND return resistors give higher volt drops adding to the feedback signal and killing the forward drive since it is negative feedback.

[@nabman_]

@xraytonyb Tony, another great video and excellent explanation and demonstration. What's your take on damping headphones in solid state amps that use drop resistors off the output and where the resistors are about 10x the impedence of the headphones? Does feedback take care of that effectively too?

[@mikepxg6406]

Its raining here in UK we have a very high DAMPing factor at the moment

[@unclefrogy743]

it looks like then that damping factor is as was demonstrated frequency dependent in practice. I understand that all speakers have different resonances and are also frequency dependent. So the designers of amps must have to add damping in a general way and can not be so exacting and aim for a broad frequency response of damping and probably a lighter touch then they would use if they were optimizing for a specific set of drivers in a speaker set where it would be more important. I know that speaker design has a large proportion of artistic creativity involved it is not just engendering math so it seems that there is also not just a little of the same kind of artistic judgement that goes into amp design as well, just like which speakers to use with which amp is an important consideration in trying to set up an undistorted audio system Interesting there are more factors I had never thought about before fun to learn new things thanks Tony ! the video image quality with the new set up is improving right along!

[@ibrahimkocaalioglu]

A design came to my mind. Single stage amplifier with positive and negative rails. Adjust the no signal point such that the collector of the transistor is zero volts. This way you connect the speaker directly to the amplifier without a dc blocking cap.

[@HyyskanPolttaja]

There are tons of amplifiers using your 'design' already. So stop wasting your time writing that patent application... 😁

[@dennbash]

Tony thank you for your time and excellent explanation. Could you please share the e202 drawing?

[@andymouse]

When you showed the coil I thought it was a Pork Pie, not sure if you have them where you live as the pastry is a little different it's called 'hot water crust pastry' and as you expect its made with hot water and fat, usually Lard but if your posh you can use beef dripping. There ! you taught me something and I hope you have learnt a bit too !

[@viktorbond6445]

Good job

[@Obsfucation]

xrayTonyB: I'm curious about the design of the Accuphase integrated amp you're using for your demonstration. The schematic and parts list in the service manual clearly shows 1 ohm/3 watt emitter resistors on the O/P devices. That seems anomalously high of a value and/or too deficient in it's power rating. At 100 watts into 8 ohms it seems that you'll have 3.13 watts of dissipation per resistor. Beyond the obvious risk of damaging the resistors and, probably, the PCB they may be soldered to is the excessive waste of that power. I wonder if you can give me some insight into what's actually in that unit and how that can work reliably along with your opinion as to why such a high value is used. Thanks and keep up the good work!

[@russellhltn1396]

100W in 8 ohms is 3.54 amps. However, there are two resistors per side, for 1.77 Amp each. That's 3.13W each. But that's only for one half of the cycle, The other half it gets to cool off. So, I think the net result is power dissipation is closer to 1.6W per resistor.

[@Obsfucation]

@@russellhltn1396 True enough but, it's rated for 4 ohm operation and although it's only good for 140 watts and maybe it's adequate I still don't understand the point of throwing away all that power for no particular reason. The prevention of thermal runaway and the NF from such a high value seems overkill and counterproductive. On the other hand; it is 50 years old so I guess it's too late for Accuphase to change it. :)

[@johnhopkins6260]

Kenwood "Sigma Drive" (aka "servo"?): Basic M1 power amplifier (intent: reduce the problems associated with overly long speaker wires...as well as enhance low frequency performance) Hence: For speaker pair A, M1 has 8 terminals at the back... M1 also has standard 4-terminal for Speaker pair B (i.e. no SigmaDrive function) misunderstanding how to connect these repeatedly caused damage; Thus, "New" Basic M1A "DLD" amp had standard 4 terminals: "SigmaDrive' (aka "servo") function was done at the amplifier output terminals. Kenwood also offered SigmaDrive wire: 2x2.5mm + 2x1.5mm (for "sense" wires) in the same insulation... Customers refused... and regularly ruined their amps. FWIW, I own 2 matched sets of Basic C1+M1... and a C2+M1A set. C1(preamp) has higher voltage output... C2 Lower Vout... C1 preout Voltage is too high for M1A power amp, C2 preamp out voltage is too low for M1... M1A power amp input sensitivity is adjustable. Read the damn manual!!! I would trade/sell my entire Kenwood Basic collection for a Kenwood L1000 series set (they used XLR and Speakon connectors!!)

[@zulumax1]

34:00 In the late 1980's Kenwood made amplifiers that had extra sensor wires called "Sigma Drive" that were small gauge that ran all the way from the amp to the speakers. Kenwood KA-9X was a 120 wpc integrated amplifier which used class G amplifier, split dual rail power supply, (30v/70v) and had a damping factor of 1000 at 50 Hz. They quit doing that because people would get the wires crossed up and damage the amp.

[@zulumax1]

P.S. Yes, that was negative feedback that the marketing folks decided to rename to something more exotic sounding.

[@123xqp]

@@zulumax1 it's ike the kelvin sensing in a 4 wire multimeter setup. I don't think it's -ve fb in and of itself, but simply moves the speaker cables inside the existing - ve fb loop to compensate for any voltage drop on those cables. Of course, any non-linear effects in those cables would already have been tweaked out by swapping them end for end 😅

[@zulumax1]

@@123xqp more of a sales gimmick. Probably a placebo effect fooling oneself more than anything you might hear. I will have to see if schematic is available on hifiengine

[@brunomahle1618]

IIRC, the info sheet for an AR 3 specs an amplifier with a damping factor of 1.

[@soundman2604]

Seems like the lower the damping factor the better the sound is for me, especially in he mid range.

[@barnyardstory]

I hear you man. I keep my files in a draw so I don't have to listen to them.

[@Stelios.Posantzis]

What would be a great natural follow up to this would be a comparison between an active and a passive system. The great mystery though would be why some might prefer a passive system (with the same exact drivers).

[@gino3286]

because they can play more with different amps and cables They treat audio equipment as children treat their toys

[@Stelios.Posantzis]

@@gino3286 It is correct that audio gear are toys for adults but active systems are even more toys.

[@gino3286]

@@Stelios.Posantzis no one of my audiophile friends use actives They are often changing amps and cables and make endless comparisons With actives you just need a preamp and some XLRs and its done The game stops too early

[@zulumax1]

46:40 I have a couple of Adcom 545 mk II amplifiers that have the warm feedback mod done to them. What is it? It is a second resistor with a bypass capacitor parallel across it, installed in series with the stock feedback resistor. The gain increased and I am sure the damping factor dropped some, but the sound is more tube like and less fatiguing to listen to.

[@georgebliss964]

If less damping is wanted, then the insertion of a resistor in series with the speaker would do the trick.

[@duroxkilo]

45:02 i am now curios if the minimum impedance selector does something similar (referring to the option on some amps to select 8, 6, 4 ohm speakers). i remember reading someplace that at some point manufacturers in an effort to get compliant w/ regulations (overheating, fire hazard, etc) implemented the 4ohm speaker switch and what is does is limit the power/current on the transistors so that amps run cooler (but also arguably weaker) when used w/ 4ohm loads. apologies if i am mixing up things, i am not educated at all in this field :)

[@paulb4661]

The most common method was to engage lower voltage secondary windings of the mains transformer in 4ohm mode and higher ones in 8ohm mode.

[@duroxkilo]

@@paulb4661 thanks

[@GaRbAllZ]

I have never thought of a speaker being a tank circuit...

[@Douglas_Blake_579]

Part of... the voice coil does have inductance so impedance varies with frequency. The crossover has reactive parts also.

[@davids4610]

I'm at 5 minutes and it's feeling very Mr. Wizzard

[@xraytonyb]

Help me!

[@davids4610]

@@xraytonybfantastic video Tony, thanks.Fascinating.

[@petercelestion7661]

That's why damping factor is not as important then output impedance and resistance of a speaker cable is These two have much more contribution to how a system sounds like

[@pistachioaudiophile]

Now there are two audiofiles? 😮

[@wb8vqv]

I notice you are using the green 10Mhz GPSDO and distribution amp. All of my test equipment have different 10Mhz reference input voltage requirements. So my question is, did you use any attenuators between the distribution amp and your individual pieces of test gear or just or just hook them up direct? I'm hesitant to hook mine up without attenuators for fear of blowing an input. Thanks, Dave

[@johngore5127]

Considering the fact that the transformer is the last component for the audio to go thru doesn't this make a difference in the resultant sound?

[@pauldow1648]

I'd like a 55 resistance, please .

[@gearheadted9210]

dampening really comes into play with killer rabits

[@muradbeq3800]

Please I need to know about phase modulation Thanks

[@scottgremko4426]

👍❤

[@donepearce]

Damping is all about resistance, not impedance. The resistive part is the only part that can dissipate energy. This is what causes damping. And the resitance is the sum of the speaker's resistance and the amplifiers resistance. This is because they appear in series. The ratio of speaker resitance to amplifier resitance is a meaningless concept dreamt up by probably an amplifier marketing department.

[@enchanter976]

Greetings, I'm looking to purchase a class d power amplifier for bass duty use and it's claims a damping factor of 5000 Approx 2.5kw @8ohms 4kw @4ohmms 6kw /channel @ 2ohms Is this 5k damping factor possible?

[@poormanselectronicsbench2021]

I enjoyed the video, and the topic, but, using your method, I think you were doing a dis-service to the general technique of measuring rated damping factors. From everything have seen, it is measured at an amp's max rated output as, the output transistors are biased on more than at the levels you are measuring at, and will have less of a Vce drop ( along with a lower internal C-E resistance) than at reduced power, so, the measurements will be different.

[@martyh9309]

There are a lot of high end solid state amplifiers that use 0 global feedback. And some have adjustable feedback that is user adjustable. More feedback will lower output impedance of the amplifier. Amount of feedack is audible as more introduces more phase error into the output.

[@noel3422]

Is that an old hepner speaker?

[@Foxtrot1967]

It's a Hefner. Pulled from a set of speakers from the Playboy mansion estate sale.

[@BenjiKimba]

And, is it important ?

[@jdmccorful]

Enjoyed; great session! Lots to mull over. Will probably rerun a couple times. I understand why you say it's not an important "spec" to you. "Variation, the spice of life." Thanks, Professor! Oh, love the Sanwa.

[@muradbeq3800]

Please I need to know about phase modulation Thanks