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Harbeth Monitor 40 domestic specific

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  • #76
    Re: Support points for M40s

    Originally posted by Ned Mast
    ...I won't worry, but will simply enjoy the music. Ned
    That's the idea! The truth is that the mechanics of the cabinet is so extremely complicated that I don't think anyone comprehensively understands what is going on in micro-detail - least of all me. So, for me to give you an authoritative statement that you must/must not do this or that would be irresponsible. If it works and sounds good for you that it must be OK!
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

    Comment


    • #77
      New generation Monitor 40 [M40.1] - development status @ May 07

      As you may be aware, last year VIFA terminated the supply of our 12" (305mm) woofers without notice or explanation. We scoured the world for these and found enough to keep production running until the end of 2006. Derek and I set in motion an immediate plan to design our own 12" woofer which involves many detailed steps. This proves the point that our own Harbeth-made drivers give 100% security of supply and the precise performance we need but does demand a substantial engineering input upfront.

      ---------------------------------------------------------------------------------------------------

      Just as an example of the issues that need to be addressed here are a few:

      1. Check stock of M40 cabinets at Harbeth and then attempt to source a 12" chassis that will fit existing cabinet stock. Done.

      2. Design the metalwork for the magnet system, have metalwork made. Done.

      3. Design or find a suitable cone of the correct height, stiffness, weight and diameter and neck opening that will suit chassis in (1) above. Done.

      4. Identify a source of suitably powerful ferrite magnet rings. Arrange and test samples. Done.

      5. Design a voice coil of the correct resistance and dimensions to suit (2) and (3) above. Await for supplier to tool-up, as with all custom made parts. Done.

      6. Design or find a suitable rubber cone surround to suit (1) and (3) above. Done.

      7. Design or find a suitable dust cap to suit (3) ensuring cosmetic similarity with existing M40 VIFA woofer. Done.

      8. Bring together and glue (1) - (7) above in various experimental combinations. Done.

      9. Measure Thiele-Small parameters for all prototypes and tabulate results. Done.

      10. Run software simulator of various prototypes when used in a cabinet of M40 dimensions; adjust tuning as necessary. Verify results by acoustic measurement of actual drivers in M40 cabinet. Done.

      11. Select most promising 12" prototype for further refinement. When convinced mount 'final' driver in M40 cabinet. Done.

      12. Take M40 outside on warm windless day and measure under quasi-anechoic conditions. Underway.

      Covered here: http://www.harbeth.co.uk/usergroup/showthread.php?t=250
      ---------------------------------------------------------------------------------------------------

      We are now at this stage. I am currently optimising the M40s midrange driver by making detail adjustments and soon will be marrying the optimised 12" with the optimised midrange. Then, again outside, I will capture the entire acoustic measurements for all three drivers without a crossover but in the M40 cabinet and feed into the crossover simulator. Only then can system intergration work begin i.e. the crossover design and relative drive unit balance.

      There is still some work to be undertaken but the bulk of the core engineering is completed. I apologise that this has taken rather a long time and for those of you who have been waiting to take delivery of your M40s but we are working as fast as we can. Our goal, as always, is complete perfection.

      Attached: two pictures of the Harbeth designed and made M40 woofer undergoing magnetic strength evaluation and prototype assembly at the Harbeth UK factory. Also, a picture of the 'redband' (codeword) M40 midrange driver being adjusted according to my request.

      >
      Attached Files
      Alan A. Shaw
      Designer, owner
      Harbeth Audio UK

      Comment


      • #78
        Re: Harbeth Monitor 40 domestic specific

        This is great news Alan! I aspire to owning a pair of M40's one day.

        For the longest time I was deciding between Quads and M40's to eventually replace my C7's but a couple of recent Quad auditions made me realize that the Radial driver in my C7's have spoiled me for all other speakers!

        The bad news is that the price of the M40 seems to be climbing faster than I'm able to save for them!!!

        Comment


        • #79
          Re: Harbeth Monitor 40 domestic specific

          Thanks for the feedback. Some days I'm almost paralysed with indecision just in case I make a mistake so fine are the arguments and judgments at this level of precision.

          I have not heard the electrostatics that you mention myself but I have discussed their public demonstration with someone I greatly respect. Under, I suppose non-ideal conditions with unknown electronics, they were described to me as 'exceedingly bright' (i.e. boosted output and/or ringy in the higher frequencies) which to my mind would make them a dramatic contrast with their previous generations.

          Could this have been something to do with the electronics or the system setup? Possibly. Could this have been the result of deliberately tweaking them for a new market, a new audience where the brightness would be attractive? Maybe. Could it be that, just as RADIAL defines the (non) sonic signature of Harbeth, a new diaphragm film has been used and that is unfortunately imparting some of its inherent sonic thumb print on the perceived sound? Or could it just have been a bad listening day? Maybe all or any of the above! Or maybe my friend is just wrong.

          This is not the place to critique competitor speakers especially such unique ones with such an illustrious pedigree but I wonder if this reflects on what society at large thinks of as a 'reference sound'. I stress, I have not heard them.
          Alan A. Shaw
          Designer, owner
          Harbeth Audio UK

          Comment


          • #80
            The astonishing, transparent and natural SHL5

            As a P.S. I have just recalled helping out at Harbeth's exhibition room several years ago in some far off country.

            As you may know, I do not have hi-fi at home: if I did it would be impossible for me to be objective and I would be seduced by my own creation - a very slippery slope indeed. So it's always a treat to hear speakers - any speakers - in unfamiliar surroundings and to learn something new.

            Anyway - the point is that in a nearby (hotel bedroom) room along the corridor an electrostatic speaker was on demonstration, and as the doors were kept open their sales people visited our room and we theirs. I'd pop in for a few minutes every couple of hours and heard quite a selection of music over the three days.

            Even applying maximum objectivity and self honesty it was a shock (a pleasant one, but still a shock to me) was how astonishingly good the Super HL5 was in every way. It was cleaner, clearer, more true-to-life, better bass, sweeter and drove the room better. Above all, the SHL5 had no sonic signature, nothing at all that said 'this is a man made box'. Nobody was more surprised (and delighted) than me since I had read so much about electrostats but not really listened to one.

            Why surprised? Well, one reads so much wonderful theory about how electrostatics have such thin diaphragms that can trace the music etc. etc. and I'm sure that is all true, but does that necessarily mean that all electrostatics are great speakers? No it doesn't. The downside of the light, taut diaphragm is that it definitely has a Cling Film-like twang that, to my ears, is ever present and so evidently man-made. It could never be the signature of an instrument or voice since no instrument or human voice is generated by wobbling a large sheet in the air.

            Remind me to tell you of my experience in Japan when I was invited to be one of the first visitors to the new Stereo Sound listening room an couple of years ago! Again .... the wonderful SHL5.
            Alan A. Shaw
            Designer, owner
            Harbeth Audio UK

            Comment


            • #81
              New generation Monitor 40 (M40.1 provisional name)

              I have not been able to give my full attention to the User Group for several weeks. This is because of my commitment to the final stages of the design of the new Monitor 40. Now that I have virtually finished, I would like to take a short holiday. After I return, I will listen again and if I am completely satisfied, we can set a production start date for as early as possible.

              This project has been underway for over a year and has ranged through every single aspect of the design. The original objective was quite narrow; to replace the abruptly discontinued VIFA bass unit with a Harbeth designed, Harbeth made woofer. However, as the months progressed, I became deeper and deeper involved with the minute details of the design, and this led to numerous small improvements. So the bass unit is completely new - a 12" first for Harbeth and the midrange driver is a new version featuring a 9 ohm voice coil to keep the system impedance nice and high: a very easy load indeed.

              Unfortunately, the changes are so extensive that there is no practical upgrade path from the original model.

              You may be interested in my reasoning behind the overall system balance of the new M40.1. I believe that in the 10 years since production commenced we have filled most of the professional installations that demand a true-BBC monitor. Also, most BBC installations are Active, and this allows great flexibility in tuning the speaker to the studio acoustics which is not possible with the passive version as used at home. This has resulted in some users deciding to invest in room-EQ systems when I would like to save them the cost, trouble and inconvenience by making the M40 even more universally usable in ordinary rooms.

              The working life of a Harbeth is 15-20 years (or more) so the best potential for sales growth for the M40 is the domestic non-studio market; that is, ordinary rooms in your homes. With this in mind, I have decided that as the Active version offers whatever adjustments the pro user demands, I should concentrate on making the new M40 100% domestic friendly. That means, in the same size classic-BBC three-way box as the previous model ...

              1. A tighter, dryer bass thanks to the cast-chassis plastic-coned Harbeth-designed and made 12" woofer (compared to the pressed chassis, paper coned VIFA unit)
              2. Higher electrical resistance (and easier load)
              3. Even smoother frequency response by attending to micro-details in the response,
              4. Better on and above-axis response integration so less height critical due to complete redesign of the crossover (which uses less components)
              5. New 8" RADIAL midrange driver with 9 ohm voice coil and long-throw high-flux magnet

              and ....

              6. Overall system is noticeably more sensitive. About 4dB more sensitive than the original model so nearly the same sensitivity as the C7ES3. That's an astonishing increase in efficiency.

              Needless to say, it sounds 100% true to the Harbeth philosophy. What astonishes me is just how huge and unconstrained the sound stage is: as if the sound stage curves around the speakers and along the side walls. It must be related to the extremely well integrated responses.

              We have many back orders to complete so please order soon if you expect delivery in 2007. More details to follow: look out for the August 07 News & Views newsletter with pictures of the (grey box, pro-cabinet) prototype being tested recently by Derek and myself in the BBC anechoic chamber. Normal domestic veneers are and remain Cherry and Eucalyptus. Picture of my prototype crossover - fewer components than the original model. I will try and make time to design a new PCB on my laptop.

              Am I allowed a short holiday now - please?!

              >
              Attached Files
              Alan A. Shaw
              Designer, owner
              Harbeth Audio UK

              Comment


              • #82
                Harbeth Monitor 40: redesign ideas?

                Hi Alan,

                since you're in the process of re-designing the M40, have you considered reversing the positions of the tweeter and the mid on the domestic model? This would bring the tweeter down about 8 inches, thereby allowing listeners to raise the entire speaker to get rid of those bass reflections we've been hearing about.

                I understand that changing the position of the units will (slightly) alter the sound, but this might be alleviated through design of the crossover.

                After all, people don't sit on a high chair at home like the professionals do in a studio (at least I don't).

                On a related note, how would turning the entire speaker upside down affect the sound?

                Enjoy your holiday,

                Peter, Shanghai

                Comment


                • #83
                  Re: New generation Monitor 40 (M40.1 provisional name)

                  Thanks for keeping us updated Alan... sounds very promising. I can't wait to audition it.

                  Enjoy your well-deserved vacation!

                  Comment


                  • #84
                    Harbeth Monitor 40: redesign ideas?

                    Hello Peter,

                    You raise interesting points. Actually, now that my ears have rested I will start listening again to the prototype M40.1 (provisional name) tomorrow, and if I am still satisfied with the listening we will commit to production. As for the measurable in-room technical performance, this simply can not be bettered: the M40.1 measures as an astonishingly flat line in my quite ordinary listening room at the Cottage (described here before). So, I think - subject to a final listening test - that we can say that the design is now complete.

                    Every step of the path has been documented painstakingly in my Log Book complete with graphs, hand written notes, calculations, cut-and-pasted printouts and photographs and extends to over a hundred pages which, in time, I will share with you. Not only have I been acutely aware of the importance of doing a good job but of leaving a documented trail as I go in keeping with the legendary status that has followed the Mobitor 40 and of which even I, the original designer, am in awe of.

                    Now, you asked a couple of questions. To answer them:

                    Q1. Reversing the position of the tweeter and woofer?

                    A1: I considered this and quickly dismissed it again for the very same reason as when deciding on the original M40 layout some ten years ago. Forgive me if I make the point again: a good speaker should mimic what we hear in nature. I mean by this that as we walk about in our ordinary lives we are exposed to sound. Evolution has programmed us such that low sounds (like growling) make us instinctively look downwards to identify predators, and of course, dogs. Conversely, high pitched sounds are associated with height - bells and specifically birds in flight and in trees. If we place the tweeter at the top of the cabinet this natural order is maintained, but if we move the tweeter to the middle of the cabinet these is some subconscious stress - some confusion - as to the size and vector of the sound. This may or may not be noticeable on-axis at the sweet spot but it will be exacerbated off-axis. We can not assume that any of our listeners are sitting rigidly at the sweet spot! So, I strongly believe that the tweeter should be at the top of the cabinet.

                    Q2: Raise the speaker upwards by 8" (200mm) or so ....

                    A2: As we say in the User Guide, the Harbeth owner has a duty of care to members of his family to mount his speakers so that they can not topple over and injure anyone or damage the speakers. I do not think that it would be wise to put the heavy M40 on very tall stands unless they are of 'studio' industrial strength and the speakers screwed or strapped to them as they are in the studio. If they fall over off inappropriate stands they could seriously injure a child or animal.

                    Actually, the point that you make in Q1 and Q2 are at odds with each other. If the tweeter is at the top (as it is in the M40) then this allows you to use a low stand - ideal from the consideration of stability and safety.

                    Q3: Reflections from the floor ...

                    A3: As for bass reflections from the floor which are an inevitable part of listening to any speaker in any real domestic room - believe me you can not eliminate these unless you listen in an anechoic chamber. Fortunately, the ear is remarkably tolerant of these reflections which typically fall in the 150-300Hz region.

                    In the M40.1 design I have carefully adjusted the optimum crossover frequency of the bass to midrange unit to take into account the floor bounce.
                    Alan A. Shaw
                    Designer, owner
                    Harbeth Audio UK

                    Comment


                    • #85
                      New Monitor 40.1 questions ...

                      Dear Alan,

                      Thanks for shedding some light on the redesign of the M40. As one who ordered a pair earlier this year, I'm very excited to see that the new version will soon become reality! I hope you don't mind a few additional questions:

                      1) Since it appears you've taken the floor bounce into the equation in the M40.1, is there a specific stand height (or range of height) that you would consider to be optimum in most rooms?

                      2) In the 7ES3, the surround on the RADIAL driver was changed. Was this also done for the M40.1?

                      3) I noticed in the prototype that the tweeter guard was missing. Will the guards be left off in the production version as well? Leaving them off may be OK in a domestic environment, where the speakers will be more stationary, provided owners leave the grills on as instructed.

                      Eric

                      Comment


                      • #86
                        Re: New Monitor 40.1 questions ...

                        Hello Eric,

                        To answer:

                        1) This is an interesting question, because it follows the new design approach which I 'pioneered' with the Compact 7ES3 and clearly has been a great sonic (and commercial) success. Basically: the designer has to pick some point on the baffle from top to bottom which he considers to be his 'reference axis'. There is no textbook rule as to where this should be - it could even be near the bottom - and indeed that would be an ideal place to set it if the listener habitually lay on the floor (in a state of inebriation of stupefaction perhaps?). Normally though the reference axis will be in the upper half of the baffle, typically just below, on or just above the middle of the tweeter's dome. There are a number of factors to be taken into account before deciding where to chalk-mark the baffle; one concerns the best phase-match between the midrange and tweeter. Another concerns the likely position of the listener's ears when sitting in a normal chair.

                        In the studio - and I've measured this many times over the years - the listener's ears are always about 124cms above the floor when sitting at the mixing desk in a good roller chair with proper posture to avoid RSI and back problems. This rule does not apply at home - the domestic listener is sitting much lower - probably slouching in a soft chair so what may be the best design reference axis in-studio may not be suitable for home use. One advantage the studio user has though is that he can rake the speakers downwards, and we've made metal stands to do exactly that.

                        Now, in the case of the C7ES3 and again with the M40.1, I've been using a new version of my crossover/time alignment simulator which is about 10 times faster than the previous generation. That extra speed allows the calculation of electrical network components for the best possible integration on the reference axis to be made very quickly: not in itself a big deal. What I can do now though is to use the processing power to explore millions of other component/circuit possibilities to engineer as wide a vertical listening arc as possible on and above the reference axis that knits together the mid and HF driver's phase-tracking.

                        What this means in practice - and the C7ES3 proves this - is that the speaker is remarkably unfussy about stand height. You can listen just below, on or (10-15cms) above the reference axis and the driver integration is seamless. The same applies to the M40.1 so you can probably get great results (depending upon your ear height of course) in stands from, say, 12 - 20 inches. But I can't give you a rule that will apply in all rooms because I don't know about your ears, your chair or your seating posture!

                        2) Yes: the M40.1 uses the same surround as the new C7ES3's driver.

                        3) Currently the tweeter guards are off. I am advised that despite the risk from little fingers - and the substantial costs involved in replacing tweeters at the user's expense - that certain users seek what they consider to be the ultimate performance. My fear is that unprotected, there will be a risk of customer-damage. We will have to (reluctantly) draw a line at the point of manufacture and pass the duty of responsibility to the user as these tweeters are extremely expensive.
                        Alan A. Shaw
                        Designer, owner
                        Harbeth Audio UK

                        Comment


                        • #87
                          Re: M40.1 tweeter grille ...

                          Alan,
                          Thank you for the very detailed reply - good news on all three counts! Personally, I would prefer the tweeter guards off, but never attempted this with my M30's.

                          Comment


                          • #88
                            Re: M40.1 tweeter grille ...

                            A.S. wrote :

                            "We will have to (reluctantly) draw a line at the point of manufacture and pass the duty of responsibility to the user as these tweeters are extremely expensive."

                            Please excuse my ignorance, but I don't understand the sentence. Does it mean the grills will be on, off, or easily removable?

                            Personally, I'd prefer the safety and peace-of-mind of having grills. The new, more "transparent" grill in the C7-ES3 would seem ideal to me.

                            Comment


                            • #89
                              Re: M40.1 tweeter grille ...

                              What it means is this ....

                              "As users have requested that the tweeter's protective grille be removed the user must be aware that deletion of the grille at the manufacturing stage may result in user damage. The Harbeth factory can not be held responsible for the consequences of misuse by users".

                              At this final stage of the M40.1 development, the tweeter grilles have been deleted from old-stock M40 tweeters and the frequency response adjusted in the crossover network.
                              Alan A. Shaw
                              Designer, owner
                              Harbeth Audio UK

                              Comment


                              • #90
                                Re: M40 - removing tweeter grilles?

                                Originally posted by Eric Pitschmann
                                Personally, I would prefer the tweeter guards off, but never attempted this with my M30's.
                                Noted. Please do not attempt to remove the tweeter guards from existing M30 or M40 speakers.

                                The magnetic field is very strong and it is almost impossible to prevent the half-off, half-on grille being pulled by the magnetic field into contact with the diaphragm. This would be a very expensive mistake for the user as even the slightest crease of the delicate diaphragm will disturb the tweeter's performance.
                                Alan A. Shaw
                                Designer, owner
                                Harbeth Audio UK

                                Comment

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