Damping Factor - Interesting article
@audiokinesis Duke, Thank you so much for your detailed response. I'll copy and paste it over on the Nenuphar speaker thread as I believe it is relevant, with respect amplifier pairings with the Nenuphar full range single driver / speaker. Your answers (and opinion) and real life findings from your experience as a speaker builder were extremely helpful! Thanks! |
I would expect it is not very high output impedance / current output driven, though it may have a relatively low damping factor and may have some current feedback. The issue is most speakers today are designed for an amplifier with high damping factor / low output impedance. Too high of output impedance and your bass response changes, and you screw up the cross-over points. All that is what I hear with Bakoon amplifiers.Which are class A/B but which are reputed to be zero negative feedback/high output impedance/ current drive/probably low damping factor amplifiers.In simple terms they simply sound incredibly clear and pure.Which I have really only heard elsewhere from expensive SET amps like the |
See my later post where I deleted one of my previous posts ... too much on the brain and wasn't paying enough attention. I was never implying that speaker response is not impacted by amplifier impedance. I was more questioning the "constant power" paradigm, not thinking about specific implementations that incorporate aspects of voltage and current control like the ultralinear tube configuration or mixed output feedback implementations in solid-state. As a speaker designer I can tell you that the difference between the two amplifier paradigms is significant, whether or not output transformers are involved. The relationship between the impedance curve and the speaker’s output level differs depending on the amplifier type, such that if the speaker’s impedance curve has significant peaks and dips, it will measure and sound different with the two amplifier types. |
How does damping factor apply to a zero feedback amp like an ayre .Generally speaking, the output impedance of a solid state amplifier can be so low with respect to most speakers that it can behave as a voltage source, even if it has no feedback. This is why there are zero feedback class D amps that also behave as a voltage source. One thing I've noticed a lot while working in high end audio is the phenomena known as 'tight bass'. I regard it as a coloration, since in real life tight bass doesn't seem to exist. The head engineer of Electro-Voice wrote an interesting article that pointed to this many years ago but I've failed to find a link to his article. Essentially though, it points out that no speaker made needs a damping factor more than about 20:1 and many need a damping factor much lower, some as low as 1:10 and you read that right (certain kinds of OB speakers). The sound difference you hear between systems that have much greater damping factors is often related to distortion rather than FR errors, due to how the brain interprets distortion (if often favors such tonality over actual FR errors or the lack thereof). |
Considering there are no speakers flat to 0.5db without equalization, let alone 0.1db, are we certain that a super high DF is going to result in the best on and off axis frequency response? What is likely to product worse cone breakup, a high DF or a low DF? According to this article DF=100 produces about 0.5dB variations typically, while DF=200 reduces it to 0.1dB. DF above 200 is inaudible. |
High damping factor directly into a driver as opposed to electrical dampening, can make high frequency ringing of the cone worse exacerbating some breakup modes. From a high level model, high DF can be like holding the voice coil stiff while the cone flexes. With low DF, the voice coil is not stationary and moves with the flex, and the increased resistance of the lower DF dissipates the energy of the motion. Very high level, almost like adding a resistor to a snubber. I should clarify, I am not saying a huge improvement, but the low DF will in many cases be better. |
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I posted this link on the Class D thread. A few questions into the interview Bruno Putzey talks about DF. Does the high damping factor of class D amplifiers negatively affect the subjective sound quality of some types of speakers https://audiophilestyle.com/ca/bits-and-bytes/purifi-audio-and-the-audiophile-style-readers-qa-with-... |
No offence to Bruno, but he doesn't sound like a very deep expert on transducers, but this is a critical point: Crossover filters are simply designed with the assumption of a voltage source. It’s a matter of standardisation. Otherwise how this particular speaker sounds when connected to that particular amp becomes rather unpredictable. It is one of the reasons active speakers have design flexibility that simply don't exist in traditional amp/speaker combinations. How low? For electrical damping of 8ohm speaker difference between DF=10 and DF=100 will be like 6.8ohm vs 6.08ohm (assuming 6ohm as resistance of 8ohm coil). It is about 12% difference in breaking current. Not to steal Atmasphere's thunder especially when I stuck my foot in my mouth yesterday, with current drive for speakers, impedance is infinite, but ideally you want a trade-off, so to atmasphere's point, you can use a combination of voltage and current feedback to achieve something close to constant power irrespective of impedance, but for that to work, you need drivers that match that characteristic. |
It is possible to make amplifier like that, but I found only car amp that delivers constant power: https://www.crutchfield.com/S-W0uT7l6IaIv/learn/amplifier-power-labs.html#:~:text=Constant%20Power&text=Normally%2C%20an%20amplifier%20will%20change,impedance%20changes%20happen%20during%20play. |
@kijanki @roberttdid was referring to the idea of an amplifier that operates as a power source rather than a voltage source.
Regarding Bruno's comment from the link above, speakers designed to operate in the Power Paradigm usually have level controls for the midrange and tweeter, as the voltage response of the amplifier is an unknown. If you look on speakers made in the 1950s these controls are fairly common. They are not there to help set up the speaker in a given room! |
@atmasphere That's how they describe this car amp: Speakers and subwoofers change their impedances depending on what frequency note is playing. Normally, an amplifier will change its output power according to what impedance it senses. The Constant Power circuitry Rockford Fosgate developed changes all that, allowing the amp to put out exactly the same power no matter what impedance changes happen during play. The constant power delivery doesn't necessarily mean it is maximum power (maximum power is delivered only when load impedance is the same as the source impedance). |
It is hard to say that a damping factor over 200 is inaudible, because the amps with very high damping factors do usually sound better. The huge power supplies needed to get a high DF also contribute in other ways. For example, my old 125 wpc Audire amps use 4 26,000 mf caps per channel (x 4 in my bi-amped system), while the contemporary Bryston with 200 wpc uses 2 4000 mf caps per channel. Guess which amp starts losing bass at high volume? Not the 125 wpc per channel one. |
