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Speaker responsiveness

Discussion in 'Amps and Cabs [BG]' started by rd2rk, Jun 12, 2018.


  1. rd2rk

    rd2rk

    Jun 29, 2012
    I remember reading somewhere that speaker responsiveness (defined here as the time it takes for the speaker to return to neutral from full excursion) in two otherwise identical speakers is different between the 4ohm and 8ohm versions. I forget which was claimed to be faster (tighter sound?).

    Any truth in this?
     
  2. ddnidd1

    ddnidd1 Supporting Member

    An amplifier's Damping Factor would have some effect, but I've never heard of a speaker's impedance being an issue.
     
  3. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    Seems like this is a function of the physical materials a driver is made of to me. The spider and surround, specifically. I'm curious now.
     
  4. rd2rk

    rd2rk

    Jun 29, 2012
  5. Rick James

    Rick James

    Feb 24, 2007
    New Jersey
    No. There might be an audible difference if the signal in a voice coil functioned even remotely close to the speed of sound, but it functions around 3/4 the speed of light. It could be half that in the one compared to the other and you'd never know the difference.
    It seems so because it's so poorly written. This does a far better job of explaining why damping factor is a non-factor.
    http://www.cartchunk.org/audiotopics/DampingFactor.pdf

    If damping factor mattered nobody would use a tube amp.
     
  6. The way I look at it the speaker moves in and out reproducing the string vibrations at their various frequencies subject to the amplifier and EQ. If the speaker refused to go at the same frequency as the amplifier there would be some really hinky sound coming out, not a mere perception of ''slow''.
     
    BadExample and agedhorse like this.
  7. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    Maybe I'm not understanding the points being made here, but I think control of the driver whether it be via amp damping factor differences or speaker mechanical characteristics differences (e.g. associated with surround compliance reflected by spring/damping aspects, acoustic damping of the enclosure, etc.) will in fact affect tone and feel. However, at the frequencies we're discussing here the speed of sound is identical for all the frequencies and therefore I would attribute no difference in sound or feel to faster or slower sound propagation, speaker impedance, of anything else in the amp or cab (as it relates to the speed of sound).
     
    BadExample likes this.
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    If the speaker moved slower, the frequency would shift downward... which obviously does not happen.
     
  9. Raf Seibert

    Raf Seibert

    Dec 16, 2013
    Texas
    There you go again, confusing the issue with facts and science. :)
     
  10. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    Which makes perfect sense...frequency is essentially defined by time. However, I was more referring to the rate at which the speaker excursions at that frequency would decay...i.e. more of an amplitude aspect. I may be seeing this incorrectly, but the speaker itself is a mass with some inherent spring and damping characteristics (which are both mechanical and electrical, with some being frequency and thus impedance dependent). The enclosure completes the package and adds additional acoustical/physics factors). You would then have to add in the signal exciting that system and its rate of change and relative strength to have all the elements to define the problem.

    In my mind it's a very dynamic system with variables changing and affecting other variables across the frequency domain. How the amplifier behaves across the intended frequency range in its interactions with the driven system is neither a matter of speed of sound or electricity which are constants and therefore irrelevant. My sense is that whatever you put in as an AC signal will be audible at the same frequency and virtually immediately (at least if you're within a normal bass cable length of the cab). Now, how quickly/crisply/distinctly that signal changes for the listener will be an artifact of the total system (amp+cab), and while frequencies won't be altered, those artifacts will have some frequency dependence.

    Am I even close?
     
    BadExample likes this.
  11. rd2rk

    rd2rk

    Jun 29, 2012
    What I was thinking, and what the original poster (wherever it was I read it) was talking about. Most noticeable in lower frequencies (where we live), and maybe not AUDIBLE, but a FEEL thing. Both of the linked articles seem to confirm that the phenomena exists, and that what's debatable is how noticeable it is. We live in a world where people claim to be able to detect 1ms latency in an AI, or 1cent tuner error. Why not this?
     
    BadExample and Al Kraft like this.
  12. Rick James

    Rick James

    Feb 24, 2007
    New Jersey
    What you haven't taken into account is that the moving mass of an average driver weighs around 60 grams, while the motive force provided by the amp and driver motor dwarfs that by a very large margin. 100 watts is .13 horsepower, so the electrical circuit has no problems overcoming the mechanical inertia of the cone and suspension.
     
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  13. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    There is also a transducer's bandwidth, wider bandwidth is sometimes referred to as "faster"
     
    BadExample likes this.
  14. Now that's a definition of "faster'' I can get behind.

    Faster or slower 80 hz or 5khz is out of tune.
     
    aborgman, BadExample and Al Kraft like this.
  15. Interesting conversation, fellas. I'd expect if there was any difference between a 4 and an 8 ohm speaker of the same model, it would show on the TSP's as a difference in the Q('s), impedance curve and/or the sensitivity spec.
     
    agedhorse and Al Kraft like this.
  16. Red Planet

    Red Planet

    May 29, 2005
    Talking Rock GA
    OEM Manufacturing Supplier

    As I understand it the only difference between a 4 ohm and 8 ohm driver is the SPL I believe the 4 ohm drivers are not as efficient as 8 on drivers and I forget where I saw this all things being equal.
     
    Last edited: Jun 13, 2018 at 9:57 PM
  17. Rick James

    Rick James

    Feb 24, 2007
    New Jersey
    There's no difference in efficiency. For instance, the JBL 2118H is 8 ohm, the 2118J is 16 ohms, both have 2.1% efficiency. SPL sensitivity per watt is the same too. SPL sensitivity per volt with halved impedance is 3dB higher, but at the cost of doubled current draw. Maximum SPL is the same too, assuming they have the same xmax.
     
  18. That article is about amp damping btw that place used to be about 10 mils from me, they made great PA speakers, big heavy and massive. I think they're art of Mackie now. Woops, no I guess they're still doing some stuff. I'm glad to see they're still in business, they made the most solid sounding low frequency bins I've ever heard.
     
    Last edited: Jun 13, 2018 at 10:11 PM
  19. Red Planet

    Red Planet

    May 29, 2005
    Talking Rock GA
    OEM Manufacturing Supplier
    I think it has to do with the mass of voicecoil. I have seen many drivers rated at 4 ohns with a lower SPL. Many manufacturers only publish one set of specs.
     
  20. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    As had as we try, 8 ohm and 4 ohm versions of the "same speaker" will always be slightly different. The inductance of the VC is one challenge, as is the ratio of DCR to nominal impedance.
     
    Coolhandjjl likes this.