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"This Harbeth User Group (HUG) is the Manufacturer's own managed forum dedicated to natural sound from microphone to ear, achievable by recognising and controlling the numerous confounding variables that exist along the audio chain. The Harbeth designer's objective is to make loudspeakers that contribute little of themselves to the music passing through them.

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Feb. 2018
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Rogers 5/8

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  • Rogers 5/8

    dear All,

    I have acquired the 2 passive cross overs for the Rogers 5/8 designed by Derek Hughes (contract engineer at Graham Audio) as an alternative to the active cross overs in the modified quads 405 ( bbc version), which means that you can use any amp with the speakers.

    I paid 800 ukp but wonder if the change in sound will really be different ? Do you have an opinion on that?

    thank you

    alexander ( Paris)



  • #2
    As the LS5/8 is a seriously odd, mangled design with the worst frequency response of any speaker I have ever measured (graph to follow) I feel sorry for you. I do not know if converting the speaker to passive will give you a different result, but as no two 5/8s have bass units with matching characteristics you have taken a universe of problems onto your shoulders.

    The overall frequency response shape of the real production 5/8, far, far removed from the theroetical position of the Design Report both in the extremely recessed midband and the early roll-off in the high frequencies (an inescapable factor with such a massive and wider tweeter diaphragm) is so bizarre, it is no wonder it never sold domestically.

    Maybe this is personal project to escape from the mayhem in your city at the moment? I have several pairs of 5/8 here, and frankly it's about time they were heaved into the skip. We could do with the space.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

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    • #3
      I'm looking forward to seeing the frequency response graph for the LS5/8.

      BTW. Don't dump them in the skip, they go for good money on E-Bay.

      Comment


      • #4
        Thank you v much , so you basically advocate to sell them and i do agree with you. However, can you think of a monitoring se up under 3000 E that will sound better ?
        [deleted} ? I listen to mostly ECM jazz abd really appreciate a precise sound . Any advise would be welcome !

        Kind Regards from Paris
        alexander

        {Moderator's comment: This Harbeth USer Group is not able to comment on the selection of purchase of alternative speaker brands. We are a Manufacturer's Forum}.

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        • #5
          Here are the cross overs for the Rogers 5/8 - let me know what you think about the circuit , any gut reactions ?
          Attached Files

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          • #6
            I'm really sorry but this forum is not the place to discuss this subject any further. The Harbeth User Group is owned and operated by Harbeth UK, and has no connection with antique Rogers speakers obsolete for twenty years or more.
            Alan A. Shaw
            Designer, owner
            Harbeth Audio UK

            Comment


            • #7
              Excuse me, Alan ! I totally understand. Which Harbeth speaker would you recommend to people who apprecaite a precise reproduction of the music, i.e. a monitoring set-up ?

              Comment


              • #8
                For about 3000 euro you have three Harbeth models to choose from, depending on budget, room size and type of music. I honestly think you cannot do better for the money.
                Ditch those old Rogers speakers and enjoy technical progresss.

                Comment


                • #9
                  Attached the shocking non-flatness of a real-world, ex-BBC LS5/8. They all have this general shape, but no two measure the same.

                  Obviously, forcing a 12" bass unit to behave as a midrange unit is completely mad and just cannot work properly as a high fidelity solution, especially even slightly off axis where the big, wide bass unit beams terribly. In studio use, used as designed with the sound engineer in the speaker's nearlfied (almost using them as super-size headphones) the beaming is not the main problem: the overall balance is. It is very important to completely understand the usage-case that the old BBC monitors were designed to be used in and not expect to tranplant them into a listening space for which they were not designed.

                  This, or similar space, is what the 3/5, 5/8 and 5/9 were designed to be used in:





                  The sad thing is that the three-way LS5/5, designed by Dudley Harwood and his final completed design, is a technical masterpiece but achieved at huge and unsustainable production cost featuring a 12" bass unit and 8" midrange - the same set-up as the Monitor 40. The passive crossover must have cost, in today's money GBP 1000 per speaker or more. Absolutely no cost spared and using the finest inductors money could buy.

                  The later two-way LS5/8 was convceived as a cost-down solution, dispensing with the midrange unit and introducing a bizarrely depressed midrange and early HF roll-off due to the fat tweeter diaphragm. Neither the woofer nor the tweeter (which even the BBC Design Report identifies as coloured but with no better commercial unit available) are in themselves ideal candidates for a Grade 1 monitor speaker. But by the time the 5/8 was introduced, the BBC was a very different and cost constrained organisation, and all BBC loudspeaker development ceased after the miserable lambasting that the (even later) LS5/9 received in the consumer hifi press.

                  You can see from the plots below the very effective way that Rogers cloned the overall shape of the active LS5/8 (lower trace) into an even lower cost passive PM510 (top trace).

                  Click image for larger version  Name:	58curves.jpg Views:	1 Size:	398.7 KB ID:	77888

                  Alan A. Shaw
                  Designer, owner
                  Harbeth Audio UK

                  Comment


                  • #10
                    Wow! Those curves sure do demonstrate that there is a very distinct step in the frequency response curve.

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