The Best Kept Secret of Spectral DMA-250/360? Damping Factor?
default -- Sat, 05/09/2009 - 03:51
Hello there!
Does anyone happen to know what is the damping factor of Spectral DMA-250/360 power amps,
and/or point me to where to find these specs? I failed to find them in the Spectral site and elsewhere.
Thanks!!
Amir
P.S., Please do save me any lectures of why the damping factor of a power amp is unimportant (or is important),
that it's just a number, like THD, and that the industry doesn't know yet what/how to measure things that teach us about
the sound, etc. etc. ALL I'm asking about are the numbers, such as 100 at 1KHz, or, better, 1000 between 1Hz-3MHz :-),
for one or both of the models, DMA-250/360. No numbers will make me buy of refrain from buying the amps. I'm just interested.
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Amir said: "Does anyone happen to know what is the damping factor of Spectral DMA-250/360 power amps,
and/or point me to where to find these specs? I failed to find them in the Spectral site and elsewhere."
It should be quite clear they do no publish this information, and I could tell you why but you asked not to be lectured. I will, though, give you a couple of hints: 1) stability down to 2ohms as published (power rating), and proven in my system down to 0.7ohms with my Martin Logan electrostatics at maximum power; 2) Peak output currents of 60 and 90 amps, as published... And I will also tell you that no Spectral user that I know of or read about has ever complained about overhang with these amps. Hope that's good enough.
Dear Eclipse,
Thank you for your response!
However, while seemingly attempting not to lecture me, you actually gave reasons (excuses?) why the damping factor numbers are unimportant/irrelevant in this case, without actually giving them, as specifically asked.
I may not be educated enough in electronics to understand what "stability ... down to 0.7ohms" and/or "Peak output currents of 60 and 90 amps" have to do with damping factor. I innocently thought damping factor had to do with IMPEDANCES (the ratio of the rated impedance of the loudspeaker to the source impedance) rather than power, current or stability.
Also, based on the fact that no Spectral user that you know, personally or publicly, has complained about overhang, I fail to conclude whether the damping factor is 10 or 10,000.
So I'm afraid that's not "good enough" as an answer to the specific question about the damping factor number(s), which may be indeed be unimportant and/or irrelevant, but, as I wrote, do interest me anyway... :-)
But thanks anyway,
Amir
Dampening factor is sort of just the relationship between the inupt impedence and the output impedence of an amp.
So in a way you CAN calculate an equivalent number for a Spectral amp.
But, as Eclipse says, the Spectrals are different.
Giving you a complete answer would require an entire article, and it would be called:
Reproducing the perfect square wave...
To start it off you could say that this is impossible, because to track a signal that closely you would have to have a circuit with
infinite bandwith/response... now, the less bandwith you have the more the amp will struggle whentracking changes in a signal...
You could say the more dampeningnfactor it will need...because it is slower to react, so it will have to react with more "force"...
So with a Spectral, you have an insane bandwith, an insanely low responsetime to every and all changes in the signal...
And an insane FORCE that it can react with.
So this is a quick answer for both the use of MIT cables and what the dampening factor actually has to say with a spectral.
Full power bandwith is 1 MHZ, the MIT kicks in at 800khz and acts as a heatsink for the above response.
What you have here is a passive feedback element with no feedback allowing the circuit in the amp to work superhard at the music signal...
This is a good thing because you now have temporal stability as well in the amp... less phase drifting if you will...
So lets sum it up:
Spectral has (most likely) a more uniform dampening caracteristic than other amplifiers... it's dampening factor within the audio band is most likely stronger and faster than any amount of signal that it passes... hence as eclipse says... the dampening can eclipse the audiosignal...
Now... the dampenign factor at the amp terminals and the voice coils of a speaker are two very different numbers!! the amps may have a number like say 2000! But the voicecoil in the speaker thinks it's 30 or thereabout...
Then we must consider the resistanse curve of the loudspeakers, the lower the impedense the more current the amp must apply "as a countermeasure" to maintain the "grip" on the speaker coil... or maintain dampening factor stability...
Now to the crux... why is the bass improved with increasing dampening factor? Well a quick answer is that all you can say is that the amp
has enough current to maintain "grip" as the current demands increase... and that is usually with decreasing frequency.
But this is wrong!!! frequency is irrelevant! all you need is enough current to maintain tracking, any frequency...
And since dampening factor really is a measure of ability to deliver current, and we need current to dampen the mass of the speaker cone with
the voice coil...
So the Spectral then uses the MIT cable to ensure that it does not try to dampen frequencies (or waste headroom) that the speakers are not eminating anyway...
It restricts poweroutput to a bandwith that is smart, and you get full usage of the dampening factor that is there!!!
And since the amp itself has an immense bandwith it is VERY quick to START to react, hence it utilices it's available "dampening factor" very effectively.
Or you could say, it can turn on a dime with more force than any speaker coil including the mass of the cone... so that the cone is at the correct place in the physical universe when the next waveform is demanded reproduced by the amp.
So Amir, I'm not sure if this is what you were after, and what I wrote is a verbal simplification of the issue. (I'm sure people will nitpick...)
Imp.
Right, forgot the number, now don't freak out here Ami...
I've tried to calculate it and I came up with the number 30
But for all intents and purposes We're gonna say at least 800 from DC to 100khz., and the reason for this is that I'm gonna
estimate that if this was a normal amp... it would have to have a dampening factor of ONE MILLION, to do what the Spectral can...
Dampeningfactor also gives us to a certain degree a measure of what kind of feedback topology the amp has, or what it could have...
So to get a really high number, normally one would have to have quite high feedback in the circuit, somewhere...
Imp.
Dear Imperial,
Thank you for your endeavor to explain!
I'm not freaking out, my name is Amir, not Ami, and it's damping factor, not dampening factor.
I may be quite wrong, but my understanding of damping factor is quite different from what I understood from your elaborate explanations -- I may have misunderstood the latter, and I apologize if I did.
My understanding is that damping factor does NOT depend on the amp's "active" abilities, such as power delivery, its abilities to reproduce square waves, how fast it reacts, and so on and so forth. Neither does the amp have to apply any current as a counter-measure to maintain the "grip" on the speaker coil, or any other components of your explanation.
My understanding is that damping factor pertains to a "passive" qualify of the amp -- its output impedance.
The idea, as I understand it, is as follows:
* Usually, woofers have large-mass cones, large coils and powerful magnets
* After some current has been actively applied by the amp, and the woofer's cone has moved from its middle position, it tends, due to its flexibility, to return to its middle position, and, due to its inertia, even continue to oscillate back and forth. This tendency exists even after the amp has stopped applying any current.
* When the cone moves, the large coils move relative to the powerful magnets and generate current
* If the output impedance of the amp is very low, the current would be very high
* Now we have very high current flowing in the coils, forcing the coils in the opposite direction to their current movement, causing them to stop moving, hence damping.
* The lower the output impedance, the higher the damping
* Please note than none of this relates to the amp's active intervention, though it appears to the speakers as if the amp has applied this current
* Actually, the amp ACTIVELY applies current ONLY according to the input signal
Please see http://en.wikipedia.org/wiki/Damping_factor for further details.
I don't know how you can COMPUTE the Spectral's damping factor without knowing its output impedance, which does not seem to be specified anywhere I could find.
The output impedance of an amp WITH a speaker cable is definitely different from the impedance without it, but, at least for comparing damping factors of different amps, it's always done without a cable. The fact that Spectral require an MIT cable is out of scope for this "standard" piece of data, as the "standard" damping factor of amps refers to a the ratio between a NOMINAL impedance (e.g., 8 Ohms) and the amp's output impedance without cable. Real-life situations can be quite different, with the cable having a significant effect, especially when long (hence the recommendation for short speaker cables), and the speaker's impedance can vary VERY significantly from its "nominal" impedance.
In any case, all of this does not answer my original question, especially with the addition of "Please do save me any lectures of why the damping factor of a power amp is unimportant (or is important)"… :-) I'm interested just in the number :-)
Enjoy your music!
Amir
P.S. 1: If woofer cones had been human, they'd surely have blamed the current induced by themselves on the amps' malicious intent of dominating and controlling them, impeding their free movement… :-)
P.S. 2: If my understanding is correct, the damping factor is not always interesting, especially with planar speakers, or speakers with built-in servo devices, such as some subwoofers.
P.S. 3: Actually, my interest in the Spectrals has decreased, since I left the Spectral route as impractical FOR ME, and have just ordered a pair of Parasound Halo JC 1 monoblocks (damping factor > 1200 at 20 Hz :-)), to be delivered some two months from now
P.S. 4: So, I wouldn't mind any misunderstandings of mine be corrected. At least I'll learn something… :-) That is, beyond the VERY useful and valuable understanding that the Spectrals are not for me, requiring Spectral preamps and MIT cables…. I do thank this forum members for helping me realize that.
You know, and I do hope you don't take this the wrong way amir, but I'd almost bet you are a woman? Are you? :)
Imp.
Wrong bet... I hope you don't gamble with your money :-)
A man. 54 years old, married.
Amir
Suave dude, suave!!!
Enjoy your Parasounds!!! They are very good! Indeed!
Imp.
Vmos Fet output transistors, and their behaviours... their resistance does not stay constant...
So with a Spectral, the damping factor varies, depending on the dampeningfactor of the speaker/cable/amp system... the impedance presented frequencywize so on and so fort by the speaker and how LOUD you are currently playing...
You see why Spectral does not give out a "number"...? It is more complex than just a number...
The designer speaks of the amp:
"Johnson: The Spectral philosophy has been to build products that are very fast and have very fast settling. Very fast capability means high bandwidths. High speed isn't important just to go from point A to point B quickly, but in preventing the circuit from having a memory that the musical even happened. Now I have a fresh start for the next event. That's speed. The electronics must settle down instantly from the loudest signal to the smallest signal, which is a ration of far more than a million to one. And they must do this within about ten millionths of a second.
...
A similar phenomenon happens with magnetic fields, particularly in power amplifiers. Even though the circuit inside might be very fast, the end result is not speed because you have to wait for the event. The feedback and compensation parts inside amplifiers store charge in a non-linear way when hit with a transient event. The charge then bleeds off after the event, creating a settling problem. You may not hear it as a sound, but you perceive that the sound is not particularly clear.
High speed isn't to get from point A to B fast. It's that you don't want anything to remain once you've gotten there."
You see, the secret is not the amp just alone, it's the cable AND the amp,driving a loudspeaker...
I tell you what, and maybe you understand... it's a slice of heaven... "slice" ...
:)
Imp.
Hi, Imp!
I see you are loyal to "dampening" and to referring to the amp's ACTIVE aspects, shifting the focus from damping factor to arguably unrelated areas.
I said the speakers' impedance varies, as of course do those of the cables and of the amp.
That's why when specifying damping factor, it's always done without any cable, using a NOMINAL speaker load (e.g., 8 Ohms). As to the amp's varying impedance, a single number is usually given for a specific frquency, such as > 1200 at 20 Hz (Parasound). Some manufacturers even specify the damping factor as >x at 20 Hz - 20 kHz.
I won't BET about it, but according to your style, you MUST be a woman -- man archetypally usually speak straight to the point and shut up when they don't understand things. The prejudice about women says they speak tirelessly about things they have no clue about and wander to realms way beyond the scope of the discussions. There are exceptions of both genders, but you fit all too accurately the prejudiced stereotype of one... :-)
Amir
Hahah!
Then I am glad to report, I am a man, and a musiclover! Age 36. unmarried, yet...
Amir! Enjoy the music, it is from my heart!! May the notes bring joy to your heart and soul, and to your spouse!
Imp.
Hi, IMP!
The woman part was IMPertinent on your part :-), but no hard feelings.
Thank you for your hearty wishes, and I hope you find a curvy woman to merge with your muscular body and enjoy music as well!!!
Enjoy!!!!!!
Amir
Oops, I apologize for my English -- not my native language.
By "curvy" I meant having the right curves at the right places :-)
Enjoy!!!
Amir
I like them curvy!
What can I say...
Imp.
Amir -
it appears you now want to lecture others, so here is why the damping factor doesn't matter... It's calculated based on the impedance of the source and load - therefore, it will vary between speakers as well as speaker cables (and of course the frequency), thus totally irrelevant. Also consider this: I attenuate my speakers bass with a 4ohm Caddock resistor (btw, the Wilson Alexandria X2 - and others - does too) - the speakers are biwirable, so I plug it in between the tweeter binding posts and the bass's and the speaker cables are connected to the tweeter posts. I have to "charge" this extra impedance somewhere - either the source or the load... If we charge it to the source, then the damping factor of my Spectral amp is roughly 8/4=2!!! But this is cheating - did I just convert my amp to a transformer-coupled tube amp (as far output impedance goes)? Then, because "Only the resistive part of the loudspeaker impedance is used" then it's best to charge it to the load, which makes the damping factor even larger than before (roughly 50% larger). So what did I just do??? My damping factor is either 2 or 50% larger than before? What???? Did I improve the handling of my bass and made it softer and tighter at the same time? What???? Nope, the quality and tightness of the bass is still the same, but the bass volume is clearly audibly less than before.
What the daming factor "number" and related "theory" simply fail to discuss is that the backward movement of the voice coil, which is said to generate the "reverse" current which needs to be damped and is PARTLY the result of the spider of the cone assembly, is actually ALSO due to the inverse phase of the signal from the amplifier! So this reverse current is only the current generated by the voice coil motor from the peak of its travel to the resting position (center), and beyond that (from the center to the other side) is due to the signal's reversed phase plus a little momentum from the driver's mass and the effect of the spider. Therefore, one can argue that the shorter the same voice coil travels (in the same magnetic field), the less potentially this reverse current??? What??? The louder, presumably, I play music (therefore, the longer the voice coil travels) the higher this reverse current. OK, then the sound must change with higher volumes - is this what we are looking for the damping factor to reduce??? Have you heard ANY good transformer-coupled tube amp (which have inherently high output impedances, thus very low "damping factor") sound audibly different in the bass???
The final fallacy of this damping factor thing is that it ignores the effects of the crossover, and what sort of damping ITSELF performs and its own impedance; thus, to simplify things, whoever invented this damping factor thing just chose to include the resistive part of the load's impedance, i.e. nonsense as far as amps and speakers are concerned, except perhaps for pure resistive loads like ribbon speakers with no crossovers (and there is no reverse current in that case anyway because there is no coil).
Cheers.
I just said:
> Have you heard ANY good transformer-coupled tube amp (which have inherently high output impedances, thus very low "damping factor") sound audibly different in the bass???
I meant to write: Have you heard ANY good transformer-coupled tube amp (which have inherently high output impedances, thus very low "damping factor") sound audibly different in the bass with varying volume???
Dear Eclipse and spaNNer,
You have evidently devoted some time to writing your essays about the irrelevance of damping factor. I'm not sure why you did it -- definitely not out of consideration for me -- I've EXPLICITLY requested NOT to be lectured about this. If I appeared to lecture others, in response to things that did not make sense to me, it does NOT mean I want THE LIGHT be forced on me against my explicit request.
In any case, I've lost interest in Spectral -- I understand it's a self-contained system, not to be mixed with non-Spectral/MIT components. Fine.
In the meantime, I've ordered a pair of Parasound Halo JC 1 monoblocks, which, by the way, have an irrelevant damping factor > 1200 at 20 Hz, though that's not at all why I ordered them. It'll take a while before they arrive, and, NO, I'm NOT interested in opinions about this, as I'm sure you have.
Please also be careful in your personal lives: if somebody smiles to you, it does NOT mean s/he wants to be raped by you, and if s/he says "NO", s/he might well mean it!!! In that case, you might end up in jail, unlike writing in free-speech forums.
Amir
Amir - lighten up, start writnig coherent arguments so that you don't confuse things and people's behaviors and intents (like you apparently have), and learn from others.
Dear Eclipse and spaNNer,
First, there is a reason why I specifically asked not to be lectured about damping factor. I didn't see the need at the time to invest in explaining why, as I didn't assume such lectures would be forced on me against my explicit request.
For me, and maybe for others, there is a certain way of reading equipment specs, with a BIG grain of salt, and with VERY limited significance attached. For example, frequency response of 20 Hz to 20 kHz +/- 3 dB can be considered OK, whereas +/- 0.03 dB COULD be conceived as 100 times better. The problem is that when you put the equipment in your room, the resulting frequency response may vary by TENS of dB-s, making the specs difference insignificant.
Likewise with damping factors. The basic idea makes SOME intuitive sense, regarding an amp's passive ability to dampen high-mass cones. It also makes sense that the higher the factor is, the better the damping for each given amp/speaker combination (especially for dynamic speakers with heavy woofer cones). However, I have no real sense of the quantitative meaning. What is the effect on the sound (if any)? Is 100 much better than 10? Is the perceived effect liner, logarithmic or what? Etc.
So, in general, the extent I believe specs might need to be considered might be limited to cases such as when:
*** You have no CLUE what sounds better and you can't audition… Poor you :-(
*** You have two pieces of equipment that sound equivalent to you and cost the same. You might then prefer the one with the better specs
Given that it was with the above in mind that I asked about the Spectral amps' damping factors, I believe you can see why I did not really require any lectures.
Second, I've never had any claims about being an electronics expert. Since I left university some 35(!) years ago, I have never busied myself with electronics, physics or differential equations. I have only some very basic knowledge and a bit of common sense to protect myself against self-appointed "gurus", "teachers" and "experts" like you.
Third, both of you made the same trivial mistake. BY DEFINITION, damping factor is a property of an AMP at a given nominal load. Anything beyond the amp's output terminals is out of scope. You cannot "charge" any added impedance to the amp, only to the output load. Likewise with "soldering, cabling, crossover components, and voice coil".
As to "people's behaviors and intents" -- we're all people here, and behaviors and intents do matter, at least for me.
Eclipse, you did help me understand things -- at my request-- in other threads, and I thank you for that, so that it's not a matter of unwillingness to "learn from others". It's different this time.
More about "intents", we do have here half authentic declarations of intent from spaNNer:
*** "One was that other people who read this forum get a rough idea of the concepts involved" -- those who know their stuff do not need such intentional gobbledygook, and those who don't won't understand much, so I don't buy it's an authentic willingness to help.
*** "The other purpose was explicitly to go against your instructions, and maybe enrage you some" -- I can easily believe THIS is authentic :-)
In every forum there are those who really want to contribute and/or be contributed to, and there are those who mainly/only want to show how smart they are and/or get whatever attention they can. I'm sorry to have encountered more than one of the latter type (not only spaNNer) in this forum.
Enjoy your music!
A
Amir -
last few comments:
First,
> Third, both of you made the same trivial mistake. BY DEFINITION, damping factor is a property of an AMP at a given nominal load
What you are actually alluding to is that some manufacturers do indeed calculate the damping factor as the INVERSE of its output impedance, and this is correct (some do), however this is not what the formula you pointed to says, nor is any real speaker's impedance nominal or constant, nor do we know how each manufacturer computes that number in order to be able to make intelligible decisions. Any which way you look at it, I don't think you can convince anyone with a little knowledge of the subject that this number matters. Instead, what matters tosome of "us" is the amplifier's current capability and stability into low impedances, in order for "us" to determine the amplifier's ability to control a load. And you don't have to agree with that, nor is anyone really trying to lecture you, just express an opinion, which - since you posted to a public forum - others are entitled to, and don't really have to respect your request to not be lectured - it doesn't work that way.
Finally, intents: it would be good to keep discussion entirely technical; your comments often veer off, like the above with respect to rape.
Eclipse,
*** I have NOT alluded to that "some manufacturers do indeed calculate the damping factor as the INVERSE of its output impedance".
*** What I wrote explicitly and meant was that damping factor is the "ratio between a NOMINAL impedance (e.g., 8 Ohms) and the amp's output impedance". I assume a nominal impedance could be a plain resistor.
*** As to "nor is any real speaker's impedance nominal or constant", I explicitly wrote "Real-life situations can be quite different, with the cable having a significant effect, especially when long (hence the recommendation for short speaker cables), and the speaker's impedance can vary VERY significantly from its "nominal" impedance."
*** "I don't think you can convince anyone with a little knowledge of the subject that this number matters" -- who ever said I was trying to convince anyone? First, I initially said that *I* was interested in the Spectral numbers, and out of curiosity only. Second, in my previous post I made very clear (I think) how small and limited significance I attach to specs in general and to damping factors in particular. How on earth did you arrive at attempting to convince anyone?
=================
All this just demonstrates that you have not read my posts in any depth -- you've been more in your "output mode" than input. Don't be surprised if such output is not wanted.
=================
*** As to "others are entitled to, and don't really have to respect your request to not be lectured" -- that's literally true. I know I was writing in a free-speech forum, only that I expected people, perhaps wrongly, to respect my request more than their wish to "show how smart they are and/or get whatever attention they can". How naive of me... :-(
*** As to "it doesn't work that way", it's only due to people like you, spaNNer and a few others, not because it CAN'T (or arguably shouldn't) go that way. It's like the fact that streets CAN remain clean (see in Japan), but there are people (not many in Japan) who throw cigarettes, cans, and other garbage in the streets, just like that. At least there are cleaning services for that, but in this and other free-speech forums, nobody cleans up, and people see fit to dump their garbage freely.
*** As to my exaggerated reference to rape -- that might be the general DIRECTION of how (overly sensitive?) people might feel when they are forced to do/read things pointed at them and ignoring their will about that.
Luckily, you are not of the worst kind. At least in some cases you do have positive contributions to make, and I keep reminding you that -- I haven't forgotten --but even you sometimes veer off… :-)
Amir
I think enough said... You get bogged down to semantics. As I said, as you can tell from the beginning of the thread, I respected your request not to be lectured, and did so only after you broke your own rule. Second, I understand your intention was not "convince" anyone at least originally, but then you got into the argument about the dumping factor - semantics again. We know you just wanted a number and there is no need to blast people - a simple 'thank you, but that's not what I was looking for' to SpaNNer would have been enough to end this thread must earlier.
Eclipse,
First, I never broke my own rule -- dear Imperial tried to help me by attempting to compute the damping factor. I tried to explain why this attempt was problematic.
Second, even if the above discussion seemed to you as lecturing Imperial, who has NOT requested not to be lectured, this does NOT break my own "rule", or more accurately REQUEST, which was about not lecturing against one's will.
Most arguments in this world are due to semantic issues, so that going back to definitions can often get people OUT of bogs.
Indeed a simple, inauthentic "thank you" to spaNNer could indeed have ended the discussion much earlier, but, as he admitted later, that's was not what he really asked for. Not to mention the contents of what he wrote…
There are a few behavioral norms in this (and other) forms that are really worth blasting.
On the one hand, you rightly keep asking people to speak coherently and to remain at technical levels/issues. On the other hand, you ignore basic manners, such as not doing things against people's requests, and prefer to ignore misbehaviors on your side. Maybe THIS doesn't work that way…
Regards,
Amir
Eclipse had two wise suggestions.
One was that I lighten up, so here is a bad joke that suits you:
Two pleb friends meet.
- Pleb A: With all these diseases around, I'm afraid of women
- Pleb B: So what do you do instead?
- Pleb A: Dogs!
- Pleb B: HOW LOW CAN YOU GET?!
- Pleb A: Chiwawa!
For you, spaNNer, being a chiwawa is not even getting low -- it's the real you. However, Pleb A doesn't get the most out of you. He should put you on a TV show -- a chiwawa that can participate in an Internet forum IS something of scoop!!!
While wrongly accusing others of breaking their own rules, Eclipse failed to follow his own second wise suggestion: he wrote "enough said" but continued writing fluently.
Well, I've had enough fun with you guys. Enjoy your lives in the forum!
It seems you have no other lives anyway and nothing better to do then poking your noses where they don't belong, especially when you obviously don't know the answers to the questions actually asked.
Bye bye!
Amir
Hi, Eclipse!
While I think it was not quite polite of you to ignore my explicit request, I think I over-reacted towards you.
Please accept my apology.
Best regards,
Amir