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HUG - here for all audio enthusiasts

Since its inception ten years ago, the Harbeth User Group's ambition has been to create a lasting knowledge archive. Knowledge is based on facts and observations. Knowledge is timeless. Knowledge is human independent and replicatable. However, we live in new world where thanks to social media, 'facts' have become flexible and personal. HUG operates in that real world.

HUG has two approaches to contributor's Posts. If you have, like us, a scientific mind and are curious about how the ear works, how it can lead us to make the right - and wrong - decisions, and about the technical ins and outs of audio equipment, how it's designed and what choices the designer makes, then the factual area of HUG is for you. The objective methods of comparing audio equipment under controlled conditions has been thoroughly examined here on HUG and elsewhere and can be easily understood and tried with negligible technical knowledge.

Alternatively, if you just like chatting about audio and subjectivity rules for you, then the Subjective Soundings sub-forum is you. If upon examination we think that Posts are better suited to one sub-forum than than the other, they will be redirected during Moderation, which is applied throughout the site.

Questions and Posts about, for example, 'does amplifier A sounds better than amplifier B' or 'which speaker stands or cables are best' are suitable for the Subjective Soundings area.

The Moderators' decision is final in all matters regarding what appears here. That said, very few Posts are rejected. HUG Moderation individually spell and layout checks Posts for clarity but due to the workload, Posts in the Subjective Soundings area, from Oct. 2016 will not be. We regret that but we are unable to accept Posts that present what we consider to be free advertising for products that Harbeth does not make.

That's it! Enjoy!

{Updated Nov. 2016A}
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Harbeth vs. 'accepted wisdom'

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  • #16
    Originally posted by A.S. View Post
    No, we have not used birch ply for about 15 years except in the LS3/5a. Harbeth LS3/5a's were always birch ply but the other manufacturers changed to MDF as far as I know.
    Hi Alan,

    Just bumped into this post. I'm interested in the reason for the change from birch ply to MDF. What are the pluses/minuses of birch ply and MDF for loudspeaker cabinet?

    Comment


    • #17
      Originally posted by audisp View Post
      Hi Alan,

      Just bumped into this post. I'm interested in the reason for the change from birch ply to MDF. What are the pluses/minuses of birch ply and MDF for loudspeaker cabinet?
      Me too. Although I note that Alan's quote doesn't actually say that he uses MDF - he's referring to other manufacturers of one specific model.

      If not birch ply, what? I'd like to know because birch ply is very expensive and relatively hard to find in DIY-quantities - alternative suggestions welcome :-)

      All the best,

      Mark

      Comment


      • #18
        We have not used plywood for about (guessing) fifteen or twenty years. MDF is so much easier to work with. And the price is reasonable.
        Alan A. Shaw
        Designer, owner
        Harbeth Audio UK

        Comment


        • #19
          Thank you - I also like working with MDF, although I worry about the dust problems. Glad to hear that its use in "thinwall" construction is perfectly viable in your experience... I know that Rogers used it in their "thinwall" domestic models as well (e.g. LS7).

          Interestingly, the last sheet of birch ply I bought didn't have the right number of veneers. It was 12mm and had 5 (IIRC) thick layers instead of the expected 9. No idea what this might have done to the acoustic properties in a speaker cabinet, but as my project involved exposed end-grain, I couldn't use it. Nor could I return it because a relative had brought it from a timber merchant on my behalf. A sign of the times, perhaps...

          You mention the problems of assembling boxes with mitred joints. Assuming the box is veneered once it's been glued together, why not use a "proper" joint? I've always been taught to avoid mitred joints if possible - I only resort to them when using veneered stock.

          Comment


          • #20
            Making a cabinet from a flat panel ...

            Yes, I'd expect 5 layer ply and 9 layer to have different acoustic properties. How different I couldn't say.

            Actually, our cabinets are made by first laminating veneer onto MDF that is just wider than the final front to back depth of the cabinet then V-cutting the corners at exactly 90 degrees. Then the 'wrap' is folded up into the cabinet. It is nothing short of a miracle that a perfect box results from machining the long, flat panel as extreme skill is required.

            Cabinet makers hate to work with thin-wall cabinets. They are the most difficult, frustrating and labour intensive box structure with hundreds of interdependent variables all waiting to catch-out the inattentive worker. Just finding a source who is willing to even attempt to make a perfect thin-wall box is a serious undertaking. The reject rate can easily be 30% when you come to close-up the wrap into a box if you are not extremely skilled. And to do it in quantity to our standard is a nightmare for all concerned.

            By contrast, modern thick-wall cabinets - even very sexy looking ones - are a pleasure for a cabinet maker to produce with zero rejects. Attached a picture of a stack of C7ES3 'wraps' v-cut ready to be folded up into cabinets and then the bitumenn damping layer applied to tune the structure. You are looking at the inside - the white softwood bearers provide an anchor for the front and back to be screwed in.

            As you can see, this 'BBC thin-wall' construction is a completely different animal to any other modern cabinet. Nobody with an eye to cost reduction (and a simple, stress free manufacturing life!) would chose this type of cabinet! This is the really difficult end of the cabinet making business and not one cabinet maker in ten would even attempt it.

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

            Comment


            • #21
              The house I am refurbishing in Nicosia has some furniture from the early 1950s. My Father-in-Law commissioned it from a neighbourhood carpenter and he tells me it was delivered on a hand cart - piece by piece as it was finished.

              Immediately after World War II wood was in very short supply, especially on an island like Cyprus. Carpenters had to make do, and did with great skill. This 1950s furniture is "thin wall". The dining table has a thin plywood top braced underneath with cross pieces every 4 inches. Below you will see a link to an image of a small cabinet which takes the weight of a 32" TV, a Squeezebox and DAC, a Quad 405 Power Amp and a Shuttle PC. The vertical and horizontal members are not solid, but fabricated by two pieces of plywood and solid wood sides. The door has a similar construction. If you look carefully you will see the bottom left corner is not square but curved, with the plywood bent to shape. Incredible craftsmanship has been applied to very poor materials!




              It does seem that about the time the BBC was introducing "thinwall" cabinets these particular carpentry skills were more common. The so called "Utility" furniture on sale in UK after WWII used the same techniques to save precious wood.

              The speakers in the picture are not thinwall and can be lifted by one man only with difficulty.

              I am considering some small Harbeths for a flat we have in UK.

              Comment


              • #22
                Alan

                Do the advantages of thin wall construction increase with the size of the cabinet?

                Does thin wall design still pay back in your smallest speakers?

                I am thinking a small panel has less opportunity to add colouration, but then the whole issue is so counter-intuitive.

                Comment


                • #23
                  Originally posted by A.S. View Post
                  The subject of 'thin-wall' cabinets is of great importance as it is the essence of the 'Harbeth sound'. I've made this little screen-video by explaining some key graphs in Dudley Harwood's 1977 BBC report (formerly head of BBC audio section, and Harbeth's founder). This video runs for 5 minutes, and will stream as it plays on the PC or MAC using the Adobe Flash format - if you need to update your free Flash player the appropriate link will open for you.

                  Link to Harbeth talk-through on 'thin-wall cabinets' (Alan Shaw talks you through BBC research)

                  If you find this interesting or informative please tell us so we can consider making more. There's 50+ years of pragmatic BBC audio research to illustrate and talk through! This was made in one take, unrehearsed and it's easy to make more of these if you wish.

                  P.S. I do hope that this is not too 'rough and ready'.
                  Hi Alan, this is very interesting and informative. Go on and make more of these and cover BBC audio research as much as possible. Thank you. Cyro.

                  {Moderator's comment: Your feedback is noted -- thank you. We cannot be expected to invest time producing these if nobody makes the effort to feed back to us. There are many subjects we could cover. It takes hours or days to plan, record, edit and upload. Without feedback we deduce that there is no interest in the subject.}

                  Comment


                  • #24
                    Harbeth videos - a sign of Harbeths commitment

                    I would certainly have a strong interest in watching however many videos along this line that Harbeth chooses to produce and post. Besides being an interesting subject in its own right, I think the deep commitment to a particular body of research is one of the things that makes Harbeth unique as a company.

                    Comment


                    • #25
                      Harbeth videos always welcom

                      I second cyro's motion-I'd also watch as many of those BBC video theorums as you're willing to create and post. Not only do I love the Harbeth Sound, I'm also quite taken with the BBC history behind them.

                      Cheers!

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                      • #26
                        Videos and essays

                        I too would welcome informative videos and essays.

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                        • #27
                          More vidoes

                          Although I did comment shortly after the original post, I'll add this as an additional encouragement to Alan to produce more of this kind of informative and educational video.

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                          • #28
                            Just can`t wait so changed veneer choice!

                            Alan, thanks for the thoughful tutorial. It is this type of insight into Harbeth design, the overall philosophy of your company and team, and performance of your product that helped me decide recently to purchase the C7-ES3. Because of current backorders (must be a good book to bill ratio for Harbeth these days), I adjusted my order this evening to an alternate veneer that I can't, but must, wait to receive hopefully sooner than later. With best regards......FWLarson

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