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Damping Factor - Interesting article

Benchmark Media published interesting article on Damping Factor.  I already knew that it does not make much difference for the damping of the membrane, but low output impedance is necessary to drive changing impedance ot the speaker (ideal voltage source).  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.

https://benchmarkmedia.com/blogs/application_notes/audio-myth-damping-factor-isnt-much-of-a-factor?omnisendAttributionID=email_campaign_5eda3b728a48f72deaf34bf2&omnisendContactID=5cf9266b15b61cc5a2a4dee7&utm_campaign=campaign%3A+AUDIO+MYTH+-+%22DAMPING+FACTOR+ISN%27T+MUCH+OF+A+FACTOR%22+%285eda3b728a48f72deaf34bf2%29&utm_medium=email&utm_source=omnisend

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erik_squires
16,051 posts
 
I just looked at the speaker load Stereophile uses:

https://www.stereophile.com/reference/60/index.html


That is a very easy to drive load compared to a lot of the speakers they review today, or are typical. I wrote to them in the hopes they update it. This speaker is a much more typical load:

https://www.stereophile.com/content/bowers-amp-wilkins-804-diamond-loudspeaker

I am 100% sure they will ignore me.

It's' my impression (with no formal data) that speakers have tended towards harder-to-drive as SS amplifiers got bigger, beefier and more expensive.  Even the DIY speakers I make have a tough time staying above 3 Ohms to get decent sensitivity out of them.

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kijanki OP
4,428 posts
 
@bifwynne  Benchmark selected 8 ohm speaker with 13 - 2.6 ohm impedance variation.  One ohm of output impedance would reduce signal to 13/14 and 2.6/3.6 respectively.  Ratio of reduced signals would be 1.286  (28.6% difference) = 2.18dB   It would be much less for my 6ohm speakers that have minimum impedance of 3.6ohm 
yyzsantabarbara
4,808 posts
 
Today I received the Benchmark StarQuad XLR that is referenced in this article. They are replacing 2 Audience Au24 and Au24 SE cables that cost over $1000 combined some years back. The 2 StarQuad’s were $200. It should be an interesting comparison. I expect no difference with my Benchmark gear but audible difference with other gear.
douglas_schroeder
3,281 posts
 
Read my review of the Gold Note PA-1175 MkII Amplifier  with switchable damping factor. It appears at Dagogo.com 
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kijanki OP
4,428 posts
 
@douglas_schroeder  Yes, the difference between DF=20 and DF=2000 seems to be huge, but not for the purpose of damping.  Amplifier with DF=2000 has very low output impedance and will provide steady voltage (ideal voltage source) at all frequencies while speaker impedance vary greatly.   It will affect the sound because of that.  Damping is different story.  When we apply positive voltage speaker membrane moves forward.  When membrane moves forward on its own speaker generates also positive voltage, but now current flows from speaker to amplifier.  Opposite direction of this current produces opposite action on the membrane and membrane stops.  This current depends on back EMF produced by the speaker and impedance in the circuit/loop.  This loop contains speaker internal impedance, impedance of speaker wire and the output impedance of an amp.   Let's assume for a moment that wire is perfect.  Total resistance in the circuit will be resistive portion of the speaker impedance - most likely 6 ohm for 8 ohm speaker and resistance of the amps output.  At DF=20 total resistance in the circuit will be 6 ohm + 8/20 ohm = 6.4 ohm  while for DF=2000 it will be 6 ohm + 8/2000 ohm = 6.004 ohm.   Ratio of braking current in the circuit will be equal to ratio of total resistance - in this case difference of 6.6%.  Is it audible?  Perhaps for trained ears, but it is not as dramatic as DF=20 vs DF=2000.  There will be more sound change from less than perfect driving, than lower damping IMHO.  For DF=200 vs DF=2000 difference in damping will be 0.6%.
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