Damping Factor

[ID.]

I've been trying to read up on the relevance of the damping factor when looking at amp specs, and although I understand it to basically refer to the control of the mid/bass drivers, I have no idea how to intepret it when I read something like "Damping factor: 120 at 8 ohms".

The other thing I wondered about was whether it would be possible/practical to make an integrated amplifier with variable damping factor. I have auditioned a headphone amp where the user could adjust the damping factor and I thought it was a wonderful way to adjust the bass to one's preference or tighten up the bass on some looser and woolier closed headphones, but I have no idea whether something like this could be implemented in an integrated amplifier where much more power is involved. Thought anyone?

Thanks!

 

[hoopsontoast]

Dampening Factor is just the relationship between the Amplifiers Output Impedance (Usually less than 0.1 Ohms on most SS Amplifiers) and the speaker impedance.

So, with an 8 Ohm speaker, and output impedance of 0.1 Ohms you get a DF of 80.

http://www.hi-fiworld.co.uk/amplifiers/75-amp-tests/149-damping-factor.html

In most amplifier/speaker designs, its not an issue unless you plan to use an amp with a high output impedance, such as SET Valve Amps, and the like, which is why they often work with very overdamped speakers such as horn loaded designs.

 

[ID.]

Cheers. Mainly trying to work out whether I can get an idea of the sound just by reading the figures, but that is probably overly simplistic of me

 

[iQ Speakers]

Ive been looking into damping factor also I read it as the ability of an amp to boss control unruley speakers and current helps hear. As to figures that most of us dont understand, when somthing sounds good we can then look back at figures to see if there is a coralation. It then might give us an understanding of whaat to look out for, but ultimatley its the sound that matters.

 

[Vladimir]

High DF (or low output impedance) is important for the amp to fully control dynamic driver's pistonic movement (forward and back). The amp will push a cone forward by applying current through the voice coil surrounded with magnetic field from the magnet. That is the easy part, pushing forward, but a speaker cone has to come back due to the spring force coming from its surrounds. Moving the coil back will create current and send it back to the amplifier. An amplifier with lower output impedance aka higher damping, will absorb this incoming current better and the amp will stay unaffected in its performance.

However, this isn't linear, as in higher DF means higher performance. There isn't much benefit between DF of 1000 compared to DF of 80. Most of that excess DF is lost in the speaker cables, crossover and voice coil (amplifier output impedance plus all the impedance of all that wire and electronics). Anything beyond 40 is good. Once you get into 25 and lower, there might be audible artefacts. Valve amps have very high output impedances, DF in the order of 8 or 12, usually always under 20. An exception among solid state amps who typically all have DF higher than 40, is Naim with DF arround 20-ish. An amp with high DF will sound dry compared to a Naim or a valve amp. This lack of control over the drivers results in pleasant harmonic distortions that add certain richness to the sound when not pushed too loud. This is why Naim keeps their amps low tech, not that their engineers don't know how to make a high DF amp. It's what the Naim house sound is.

 

[drummerman]

Cheers. Mainly trying to work out whether I can get an idea of the sound just by reading the figures, but that is probably overly simplistic of me

Kind of, you'd also need to know the specifics/characteristics of the speakers ie. are they over/under damped.

With smaller speakers an amplifier which has a low(ish) df can sometimes sound nicer depending on what floats your boat. As Vlad said, Naim have always used low damping for their amplifiers, usually around 12 which puts them into the ball park of some valve amplifiers, not that they much sound like one but it does add to their (imho) inherent 'musicality' even if it can be a deviation from what some call is true fidelity.

Hegel, to name one, on the other hand, use very high damping for their amplifiers. This will control the woofers of speakers more rigidly but could, theoretically, end up sounding dry and overdamped with speakers that have similar characteristics.

You pays your money

 

[Vladimir]

Any amp with DF of above 40 will have the same control over your typical speaker. Therefore, a 10000000 DF amp will not sound colder than say a 80 DF amp. But as soon as you go bellow 25 DF, things change depending on the speakers more than the actual amp. In the 4 ohm region where large drivers carry LF, things are most critical, and amps with DF of 40 at 8 ohms (0.2 ohms / 8 ohms = 40), might have issues with some speakers (0.2 ohm / 4 ohms = 20) but typically unlikely to be something ungainly to listen to, you might even like it.

So what to look for in manufacturer declared technical specification. If you see a declared DF, always presume it's at 8 ohms because manufacturers love declaring 'optimistic' scenarios. If it's anything above 80, you are fine. If it's 40, you might want to play some drum, piano and bass guitar tracks and hear if you like the performance or you find it a bit mushy. If it's something like 1000, don't be too impressed, it doesn't matter at all as long as it's above 80.

addendum

I remember reading how during the 70s and 80s Japanese manufacturers boasted on having higher DF and lower THD amps than their US and UK competitors. Yamaha, Pioneer, Kenwood and Sony proudly advertised 1000 DF as a feature that produces clean precise sound and UK contradvertising said it only makes oriental amps sound clinical, cold and soulless. Ivor and Julian vs the big Japanese corporations is the fun part of hi-fi history and their legacy of 'specs hate' still marches on today. However the biggest japanese marketing slayer was Matti Otala hired by Harman, succesfully clearing the fog surrounding low THD + high DF and introduced IMD (intermodular distortion).

Eventually in the 90s no one cared about specs since hi-fi in general began diminishing as an industry.

 

[iQ Speakers]

Vlad please only post if you know what you're talking about*biggrin*

All interesting stuff though especially the Naim DF! Do you know what the Abrahamsen DF is?

 

[Vladimir]

Vlad please only post if you know what you're talking about*biggrin*

As long as andyjm, dave, lindsayt and matt don't chime in, I may pull it off. *secret*

All interesting stuff though especially the Naim DF! Do you know what the Abrahamsen DF is?

Ughh, no idea. *unknw* Abrahamsen are literally mute when it comes to boasting about performance. I had to manually count the capacitors in the V2.0 UP to realize it all stacks up to 100.000uF, a figure you expect in a Krell.

 

[iQ Speakers]

Well done you, I have now realised how important this is, a good spot, you really are wasted. I really appreciate your support.

 

[drummerman]

Vlad please only post if you know what you're talking about*biggrin*

As long as andyjm, dave, lindsayt and matt don't chime in, I may pull it off. *secret*

All interesting stuff though especially the Naim DF! Do you know what the Abrahamsen DF is?

Ughh, no idea. *unknw* Abrahamsen are literally mute when it comes to boasting about performance. I had to manually count the capacitors in the V2.0 UP to realize it all stacks up to 100.000uF, a figure you expect in a Krell.

... and yet it is still 'only' at 2x70w/ch amplifier.

Good value though for such a big thing.

 

[SteveR750]

Do you know what the output impedance is of the Abrahamsen amp? You can calculate the DF from that.

 

[iQ Speakers]

Steve I dont As Vlad says Abrahamsen keep things close to there chest including delivery info!

@Drummerman it really does not matter! though strange, if I was more technical maybe i could tell you why maybe Vlad could tell us?

 

[SteveR750]

Steve I dont As Vlad says Abrahamsen keep things close to there chest including delivery info!

@Drummerman it really does not matter! though strange, if I was more technical maybe i could tell you why maybe Vlad could tell us?

Easy enough to measure it.

 

[drummerman]

Steve I dont As Vlad says Abrahamsen keep things close to there chest including delivery info!

@Drummerman it really does not matter! though strange, if I was more technical maybe i could tell you why maybe Vlad could tell us?

It is simply over-engineered.

Nothing to complain about, especially at the price but it is in essence not much more powerful than a Cambridge Audio 651 and less so than their 8 series or a Roksan K2.

Where it may edge ahead is with very difficult to drive speakers.

I guess it's design 'ethos' harks back to some designs of twenty or so years back unless it is a Class A design and I missed that.

Like I said, I was, for a moment, very tempted but decided I like my cyrus'es to much and spend the cash on something else rather than hifi. If they'd updated the look I may have felt different.

Purely subjective and I appreciate some will disagree. Neither did I mean to put the product down in any way. Thinking about it I'd rather they've cut down on the power supply and spent the money elsewhere, perhaps more useable power for very inefficient speakers, a built in DAC (or a prettier exterior) but given the price, there is nowth wrong with it.

 

[Vladimir]

Being only 70Wpc in 8 ohms means it will not go very loud with low efficiency speakers in a large room. You simply buy bigger amp for bigger room and slugish speakers. The large PSU ensures it will soldier on through any nasty impedance and phase shift without affecting the original FR. It gives you the liberty to have a wider selection of speakers to chose from to your liking, and speakers are where most of the sound quality and character is situated in the hi-fi chain.

Recently we had a chap on the forum who bought a Quad 405 amp and he asked what speakers should he buy for the amp. My answer was simply "anything you want". That is the luxury of having a gutsy amp.

 

[iQ Speakers]

Drummerman you really need to hear one! And no offence taken I really think you would be surprised. It's all very well looking at specs but I'm beginning to think they almost mean didilly squat. And I studied electronics! No wonder I ended up in sales!

 

[drummerman]

Drummerman you really need to hear one! And no offence taken I really think you would be surprised. It's all very well looking at specs but I'm beginning to think they almost mean didilly squat. And I studied electronics! No wonder I ended up in sales!

There is a whole list of hifi I would like to listen to, your Abrahamsen one of them boggit.

 

[iQ Speakers]

I know the feeling you're more than welcome with no strings. Your opinion would be good or possibly bad!

 

[drummerman]

I know the feeling you're more than welcome with no strings. Your opinion would be good or possibly bad!

Appreciated. There are others whose opinion will probably be more relevant and which hopefully take you up on a similar offer.

 

[Vladimir]

*biggrin*

Part 1 and Part 2.

 

[tonky]

things to do.

 

[YiannisK]

Old thread I know but super interesting one. Could not resist

I was researching damping factor a bit as I am trying to understand bass response and amplifier-speaker pairing a bit more. So, I recently acquired a pair of B&W CM1 S2 speakers. I tried them with a few amps: Naim Nap 250DR (driven by Naim Dac V1), Naim Nait 5si, Rotel RA-12, Arcam A29. What is interesting is that the Naim amps have a low dampig factor and the Rotel has a (reported) super high damping factor (around 800). The B&Ws are reported to have boomy bass (as I also experienced both at home and in the audition) so perhaps we can put forward that they are less damped compared to other speakers (happy to be corrected if I got this wrong).

Approximate Damping Factor = Speaker Load (Nominal Resistance) / (Amplifier output impedance + 2* total speaker cable resistance)

I looked at stereophile for the above formula and I was also able to source data for Arcam, Naim and Rotel amps although not necessarily the exact models.

Interestingly, Arcam (A19 and P49) and Naim (5si and Supernait) are reported having a relatively higher output impedance as compared to other solid state amps. Naim Supernait for example has an output impedance of 0.3 ohms. The Arcam A19 and P49 are measured as having output impedance of 0.155-0.19 (across freq range). The Rotel RB-1090 power amplifer reviewed by sterophile is reported as having an output impedance of 0.1 - 0.16 (across freq range).

So if we take the above as 'indicative' impedances for the respective brands, assuming an 8ohm nominal speaker impedance (disregards impedance fluctuations across frequency), 2m of speaker cable with 0.01 ohm /meter resistance:

Rotel DF = 57.14 - 40

Naim DF = 23.5

Arcam DF = 41 - 34.8

Interestingly the Rotel stated High DF is not confirmed by the above calculation. Perhaps this is reduced in other ways (?)

Anyway, the Naim 250DR and Arcam A29 paired with the CM1 S2 occasionally sounded a bit boomy and uncontrolled in the bass. This was the the case when I auditioned but more so at my own living room (smaller space, speakers closer to thea wall) The Rotel had a stronger bass punch (a bit much actually) but it was slightly less boomy. This experience sort of correlates with the above DFs although the differnces are not that great.

Interestingly again... Arcam has double the DF (mostly) over the Naim. They sounded very similar when driving the CM1 S2s. The bass boomed a little. Caveat: The Nap 250DR was driven by a Naim Dac V1 while the Arcam A29 was fed by a Rega Dac (same as the Rotel). The source may imact a difference as well.

Not a methodologically valid experiment but I still found it interesting, especially considering Arcam and Naim. They latter is always discussed as good with pace and rhythm and timing while Arcam tends to be discussed as laid back, un dynamic, slow etc. Yet, if we look at the DFs, the Arcam appears to be better at controlling bass cones and Naim may be the one with a boomy, flabby bass.

.. proceeds to scratch head.

 

[James7]

Interesting post Yiannis, and nothing wrong I think with resurrecting a thread like this that deals with a specific, important element of music-making that is rarely discussed. I have come to think that damping factor is a really important element in amp-speaker synergy - there is no right answer here to what the damping factor should be (contrary to some suggestions that the higher the damping factor the better); rather it is a matter of system matching and some speakers, many modern speakers in fact, including the B + W you were listening to, seem to respond best to amps with a higher DF, while others (Triangle, Magnepan) seem to be better suited to amps with a lower DF. Spec sheets can help point in the right direction in terms of putting together an auditioning short-list, but as always listening is the key, and this is where your own findings are interesting.

 

[davedotco]

Back in the day, I am thinking 'olive' series Naim here, their damping factor was so low and their control at low frequencies so poor that they sounded slow and 'ploddy' with virtually any speakers with an extended bass response.

Naturally Naim blamed this on the speakers, accusing them of being 'out of tune' or lacking 'prat', thus consigning a whole generation of perfectly decent speakers to oblivion, as of course, it was the lack of control from their amplifier that was the real issue.