Amplifier Damping Factor - 1075 /1080 ?

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  • Stevebez
    Senior Member
    • Oct 2003
    • 458

    Amplifier Damping Factor - 1075 /1080 ?

    I am tempted to add a 1080 to my 1066/1075 setup to drive the fronts - which i plan to upgrade too from my meagre Boston Micros. This idea, encouragingly, seems to be a popular upgrade path of others too ! Upgraditis seems to be infectious! I have even considered whiping out the old soldering iron and solder sucker to tackle some Op Amps etc... but sanity has prevailed ... for now...

    Question re the damping factor (DF) which on the website info on the 1080 goes on how good the 1080 is with a DF of 1000. The 1075 has a DF of 180, if I remember correctly.

    What exactly does a higher DF mean in an amplifier? Why is there such a difference between the 1080 and the 1075?

    Thanks in advance to all those more technically gifted!

  • Stevebez
    Senior Member
    • Oct 2003
    • 458

    Found my own answer !!!

    Quite interesting... the DF refers to the ratio of internal impedance of the amplifier to the speaker system.

    DF = Speaker Impedance
    Amplifier Impedance

    e.g. DF = 8 ohms = 1000 (a la 1080)
    0.008 ohms

    Simply stated the DF is the ability of the amplifier to allow the speaker cone to return to its mean static state as soon as possible, from the momentum generated from a singular pulse.

    So if the amplifier damping factor was very low, the speaker cone would oscilate about its mean static position before it came to a standstill. This then adds colouration to the sound field, which to most is undersirable. So in this case the amplifier's internal impedance is high, the speaker cone would encounter resistance on rebound and then continue to bounce about its static mean position until it finally comes to rest. The amplifier acting like a trampoline for the speaker cone... perhaps desirable for those with BASS-IDITIS, but less desirable for those who want precision.

    An amplifier with a high (greater than 20) DF, is able to absorb the energy generated by the cone rebound, and thereby allowing the speaker to return to its mean static position as quickly as the speaker design will allow.

    So to comment on the DF of the 1075 , this seems ample while the DF of the 1080 seems like overkill, according to the literature I have read.

    Hope this enlightens some!

    Rgds Steve.

    P.S. Have my heart set on a 1080 now regardless!!!
    Ahhh the upgraditis hurts!


    • aud19
      Twin Moderator Emeritus
      • Aug 2003
      • 16706

      Overkill....that's what I look for in components! :T

      Good info to know Steve, thanks


      Need a new display? Questions about new display technologies? Visit RPTVs, plasmas, and other monitors @ HTguide


      • ThomasW
        Moderator Emeritus
        • Aug 2000
        • 10934

        Note that the damping factor changes significantly (sometimes by a factor of 10) if there are large value inductors in the signal path. As a result so called fullrange speakers (3-way or 4-way designs) drastically lower the damping factor of any amp.

        A good way avoid this is to have 2-way mains with an active sub (or use the LFE out from a pre/pro). The smaller inductors used in a 2-way systems, have much less effect on the damping factor.....


        IB subwoofer FAQ page

        "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson


        • Atorak
          • Feb 2004
          • 34

          Has anyone ever actually tested a 1075 against a 1080 with two fronts before? I just bought a 1075, but I never use the other 3 channels (yet)!

          The 1080 would also be a considerable jump in power, (125 vs. 200).

          I KNOW this is a Rotel forum, but anyone recommend the 'next level up' above a 1080? Heh, its always nice to dream about the future! Perhaps some monoblocks, or a nice krell. Any ideas?


          • Azeke
            Super Senior Member
            • Mar 2003
            • 2123

            I have actually tested the RMB-1095 vs. RB-1080, and IMHO the jump to a separate channel for the fronts (better control) is a pheasible upgrade, it provides a good return for your buck.

            I have not really considered going to Krell or other high-end components, due to budget restraints, but my basic philosphy is, it's better to have too
            much power, than not enough. In addition, I always try to get the best bang for my buck, and do the necessary research. I am happy with my current Rotel equipment. However, the upgraditis bug always looms near, and that's why I have learned not to compromise on the power amps, because it is a longer lasting product, ( providing some psuedo-relief against the upgraditis bug, I digressed 8) ).

            Your mileage may vary,



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