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Wood speaker stands; anyone compared them to metal?

Helen Bach said:
I didn't say he made glulams, I am saying the term cld is often applied (erroneously) to several layers of different (or the same) materials, glued together. These are glulams, not cld. As you point out, cld is (in its simplest form) made of a layer of material to be damped, then a viscoelastic layer, and finally the constraining layer. BUT, cld only works if all the layers bend a little, to stretch the VE layer, and thereby incur losses by shearing. And that 'very thin' layer is also important, (as is the thin panels). If you look at his demo of how things bend (a very good illustration, IMHO) you will see how much effort is needed. I'm sure those forces are not produced in a loudspeaker cabinet. For cld to work properly, all layers have to be thin, very thin. Of course, all this is academic if single layer products are used which have greater damping ability. The ones illustrated/demo'ed do not seem to have much damping, cld or not.
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CLD is more effective than the BBC 'thin wall / thick damping' for an equivalent thickness material (stiffer and with better damping).
So If you think CLD is ineffective, you must believe the BBC were completely wasting their time with the thin wall / thick damping speaker cabinets.

Also, in the video when the guy let go of that 'tiny little' weight that was attached to a wire, and took a measurement, the difference was easily measured and significant. Do you really believe that little weight was heavy enough, and had enough force to bend the material? Because you are saying the material has to be bent significantly before CLD will have an effect, and that is clearly wrong.
 
Fatmarley said:
CLD is more effective than the BBC 'thin wall / thick damping' for an equivalent thickness material.

So If you think CLD is ineffective, you must believe the BBC were completely wasting their time with the thin wall / thick damping speaker cabinets.
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The BBC research is 50 years old... And if I'm not mistaken weight and portability rated high in the design brief.
 
tuga said:
The BBC research is 50 years old... And if I'm not mistaken weight and portability rated high in the design brief.
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Yes, and it's still used now by some manufacturers.

For all I know, the BBC may have considered CLD but didn't bother due to cost and/or weight reasons. I'm sure the BBC had their reasons to do what they did, and I'm not disputing that, I'm just trying to show Hellnback that CLD is effective.
 
Fatmarley said:
CLD is more effective than the BBC 'thin wall / thick damping' for an equivalent thickness material (stiffer and with better damping).
So If you think CLD is ineffective, you must believe the BBC were completely wasting their time with the thin wall / thick damping speaker cabinets.
Click to expand...

The thing that is often overlooked with the BBC designs IMO is the thin-wall was only part of it. Screwed rather than glued baffles are I suspect at least as significant in breaking resonance, as is the very conscious decision to keep resonance low in frequency and low in Q. There was a lot of joined-up thinking there that is IMHO miles ahead of the dumb glued heavy MDF boxes the modern hi-fi world is now littered with at all price-points. It is the difference between real scientific research and some random audiophile brand with a table saw, a few off the shelf drivers, and little if any clue about physics. As stated upthread it is interesting to contrast just how much further along pro-audio brands (Neumann, Genelec etc) have taken cabinet design in past decades. That the classic BBC designs still command so much respect 50 years later shows just how stagnant home audio speaker design has become.

PS The thing I liked about the video upthread was about five of the six or so alleged benefits for MDF the guy gave were that it was very cheap. That’s it in a nutshell. I would love to hear those Voight speakers.
 
Fatmarley said:
CLD is more effective than the BBC 'thin wall / thick damping' for an equivalent thickness material (stiffer and with better damping).
So If you think CLD is ineffective, you must believe the BBC were completely wasting their time with the thin wall / thick damping speaker cabinets.

Also, in the video when the guy let go of that 'tiny little' weight that was attached to a wire, and took a measurement, the difference was easily measured and significant. Do you really believe that little weight was heavy enough, and had enough force to bend the material? Because you are saying the material has to be bent significantly before CLD will have an effect, and that is clearly wrong.
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I didn't state cld was ineffective, I said that from the results shown in the video, it seems a huge amount of work has been done with very little reward. My conclusion is that cld was NOT at work here, and the FACT that some single materials have MUCH better damping. The BBC boxes were not cld either! but they worked out OK. And yes, the viscoelastic layer has to bend, to use shearing to dissipate the energy. The substrate (that layer to be damped) and the constraining layer will also have to bend, microscopically, but they do bend. Thick panels do not. If you refuse to believe me, just read a few hundred scientific papers on the subject, as I have. I don't see cld helping much with loudspeaker damping, unless it's on the aluminium cylinders in the JR149 design (thin aluminium, which has a damping factor (without cld) of 0.004 (equivalent to a Q factor of 250!!), or just less that the SQRT of sod all).

I agree with Tony (a lot) on this subject, especially about mdf, which has very low amounts of intrinsic damping.
 
Tony L said:
The thing that is often overlooked with the BBC designs IMO is the thin-wall was only part of it. Screwed rather than glued baffles are I suspect at least as significant in breaking resonance, as is the very conscious decision to keep resonance low in frequency and low in Q. There was a lot of joined-up thinking there that is IMHO miles ahead of the dumb glued heavy MDF boxes the modern hi-fi world is now littered with at all price-points. It is the difference between real scientific research and some random audiophile brand with a table saw, a few off the shelf drivers, and little if any clue about physics. As stated upthread it is interesting to contrast just how much further along pro-audio brands (Neumann, Genelec etc) have taken cabinet design in past decades. That the classic BBC designs still command so much respect 50 years later shows just how stagnant home audio speaker design has become.

PS The thing I liked about the video upthread was about five of the six or so alleged benefits for MDF the guy gave were that it was very cheap. That’s it in a nutshell. I would love to hear those Voight speakers.
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I learnt about sound transmission at college, and sound will still travel through screws. The only way to reduce it significantly is to decouple the baffle.
 
Helen Bach said:
I didn't state cld was ineffective, I said that from the results shown in the video, it seems a huge amount of work has been done with very little reward. My conclusion is that cld was NOT at work here, and the FACT that some single materials have MUCH better damping. The BBC boxes were not cld either! but they worked out OK. And yes, the viscoelastic layer has to bend, to use shearing to dissipate the energy. The substrate (that layer to be damped) and the constraining layer will also have to bend, microscopically, but they do bend. Thick panels do not. If you refuse to believe me, just read a few hundred scientific papers on the subject, as I have. I don't see cld helping much with loudspeaker damping, unless it's on the aluminium cylinders in the JR149 design (thin aluminium, which has a damping factor (without cld) of 0.004 (equivalent to a Q factor of 250!!), or just less that the SQRT of sod all).

I agree with Tony (a lot) on this subject, especially about mdf, which has very low amounts of intrinsic damping.
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I'm about to go to bed, but will correct your post tomorrow :)

EDIT: It's quite obviously going to be one of those circular arguments, and I'm much happier in my life since I stopped getting engaged in those, so - You win :)

I also agree with Tony regarding MDF BTW.
 
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It should be fairly simple (and cheap) to DIY some wooden speaker stands if you can use a tape measure and some hand tools. That way you can make them to any height you like and any design. If it proves to be what your after great, if not no big loss.
 
Fatmarley said:
I learnt about sound transmission at college, and sound will still travel through screws. The only way to reduce it significantly is to decouple the baffle.
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…and we find ourselves back at bolt-tightness! I don’t actually have much experience with BBC designs yet as I’ve not pulled my LS3/5As to bits and I don’t really count Harbeths (they are MDF cabs with a nod to BBC construction, but are very different really). The Lockwood cabs, which are very much their own thing, have a layer of ‘draft excluder’ between the rear panel and the cab and bolt tightness here is certainly audible. As usual little beyond finger-tight seems right to my ears, and I suspect some degree of randomisation is good. The whole cabinets are remarkably dead given their size, no discernible ‘note’. The Harbeth cabs responded to baffle/back panel screw tension too. I’d like to play around with some proper old-school BBC boxes one day, e.g. LS5/8s or whatever in this regard. To be honest I don’t view LS3/5As as being big enough to count as thin wall. I suspect much of their secret is the screwed baffle, material choices and damping. They are actually quite heavy for their size, they certainly weigh a lot more than the (MDF) Spendor S3/5Rs, I suspect more than the 149s too, but I’d need to check that.
 
Fatmarley said:
Yes, and it's still used now by some manufacturers.

For all I know, the BBC may have considered CLD but didn't bother due to cost and/or weight reasons. I'm sure the BBC had their reasons to do what they did, and I'm not disputing that, I'm just trying to show Hellnback that CLD is effective.
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And those manufacturers are using modern damping materials to improve on the BBC's design, which was driven in a large part by keep manufacturing costs down and the weight low.
But if you look at Stereophile's cabinet resonance measurements Falcon's, Harbeth's, Spendor's and Stirling's designs still produce very significant resonances, for example:

615HLS5fig2.jpg

Harbeth Super HL5plus, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of top panel (source)

This is the conclusion of the BBC RD's paper "Factors in the design of loudspeaker cabinets" (PDF):

Wv6TTq8.png
 
tuga said:
But if you look at Stereophile's cabinet resonance measurements Falcon's, Harbeth's, Spendor's and Stirling's designs still produce very significant resonances, for example:
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As stated above I personally don’t view Harbeth as anything other than BBC influenced/marketed. Their cabinets are MDF, a material that didn’t even exist back when the BBC did all the research. It is also a material with entirely different properties to the damped ply of say a LS3/6. You can play an SHL5 like a conga drum, it is a remarkably resonant box!

PS I have a lot of respect for the Kef LS50. One of the most interesting home audio speaker designs of the past 40 years IMHO. In no way would I describe it as the typically lazy glued MDF box, a huge amount of real research went into all aspects of driver and cabinet design. My only criticism is it is manufactured in a dictatorship with an appalling human rights record, but so is the iPad I’m typing this response on.
 
Tony L said:
As stated above I personally don’t view Harbeth as anything other than BBC influenced/marketed. Their cabinets are MDF, a material that didn’t even exist back when the BBC did all the research. It is also a material with entirely different properties to the damped ply of say a LS3/6. You can play an SHL5 like a conga drum, it is a remarkably resonant box!

PS I have a lot of respect for the Kef LS50. One of the most interesting home audio speaker designs of the past 40 years IMHO. In no way would I describe it as the typically lazy glued MDF box, a huge amount of real research went into all aspects of driver and cabinet design. My only criticism is it is manufactured in a dictatorship with an appalling human rights record, but so is the iPad I’m typing this response on.
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My Stirlings are built to BBC spec and they produce as much resonance as the SHL5s:

214SLS36fig2.jpg

Stirling BBC LS3/6, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of top panel (source)


Economic growth and consumerism are the culprits of this current environmental disaster that we are facing. The whole thing is unsustainable.
 
tuga said:
Areas with constrained layer damping can be seen in this photo:

9B6dCXx.jpg
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Are you sure they have CLD? It looks like the braces may have a gap filled with damping compound where they fix to the inside of the enclosure, but I don't see CLD. Tannoy did something very similar with their DMT studio monitors.
 
Fatmarley said:
Are you sure they have CLD? It looks like the braces may have a gap filled with damping compound where they fix to the inside of the enclosure, but I don't see CLD. Tannoy did something very similar with their DMT studio monitors.
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From the white paper I understand that Kef calls it CLD.
 
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