TG "The Loudspeaker" Build (Sort of)

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Nick
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#151 Re: TG "The Loudspeaker" Build (Sort of)

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simon wrote: Mon May 13, 2024 9:49 pm Yes very interesting. I can't help thinking that getting an adequately balanced platter, with suitable thickness, roundness and centrality would be exceptionally difficult for DIYers though.
Unless I missed something, that why I said plinth. I was thinking of what the l07-d was made like

"The aluminum subframe is cast into the main section of the plinth, which is composed of a concrete resin. Kenwood calls this material ARCB, which stands for Anti-Resonance Compression Base. These two components form two thirds of the plinth. The remaining part is a one and three-sixteenths inch thick mahogany composite sub-plinth. The mahogany sub-plinth is attached to the ARCB section with 34 screws."
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#152 Re: TG "The Loudspeaker" Build (Sort of)

Post by simon »

So you did. You know better than to trust me these days ;-). The "problem" gets a whole lot simpler! Though the 25kg H&S limit must be in danger!
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#153 Re: TG "The Loudspeaker" Build (Sort of)

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Though the 25kg H&S limit must be in danger!
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#154 Re: TG "The Loudspeaker" Build (Sort of)

Post by simon »

Did someone say boatanchor? :-D
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#155 Re: TG "The Loudspeaker" Build (Sort of)

Post by Morgan Jones »

That's no boat anchor, that's quality stuff!

I got back from Retrokit on Sunday and was asked by SWMBO whether I'd bought any bargains and admitted that I had. I said I had bought, "Some DMMs, and a few other bits." One of the meters (Solartron 7075) is rather large. 19" rack-mounting, 2U high and as deep as it is wide. But saved from being a boat anchor by having a beautiful display and working. Eight nice big orange seven-segment LEDs. And in beautiful condition for something made in the early 80s - obviously never raced or rallied. Damn heavy, mind. A thing of rare beauty. Can't talk to a computer, though.
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#156 Re: TG "The Loudspeaker" Build (Sort of)

Post by Ant »

Nick wrote: Tue May 14, 2024 2:20 pm
Though the 25kg H&S limit must be in danger!
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One day ill have one......
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#157 Re: TG "The Loudspeaker" Build (Sort of)

Post by simon »

Morgan Jones wrote: Tue May 14, 2024 4:58 pm That's no boat anchor, that's quality stuff!
It was a reference to some of the back-breaking amps that we used to build rather than besmirching the fine turntable.
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#158 Re: TG "The Loudspeaker" Build (Sort of)

Post by Morgan Jones »

Ah, I should have added a smiley face or summat. Since breaking my back (for the second time) I have vowed to make lighter electronics. But it always seems to be heavy. :?
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#159 Re: TG "The Loudspeaker" Build (Sort of)

Post by simon »

Blimey, once would be bad enough but twice is terrible. I hope you've recovered well.

Even simple valve amps end up heavy. What surprises me is how the same amps have become much heavier over the years when I pick them up.....
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#160 Re: TG "The Loudspeaker" Build (Sort of)

Post by Morgan Jones »

I've been lucky; fully recovered. But I aim to avoid a third event.

They do, and obey the law of variable gravity that should be taught in schools; mass is proportional to distance carried and age of carrier.
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#161 Re: TG "The Loudspeaker" Build (Sort of)

Post by simon »

Very wise!
Morgan Jones wrote: Tue May 07, 2024 11:55 am There's a very interesting paper by Tappan about panel resonances. Essentially, braces should be added that minimise the diameter of inscribed circles. And that means that the most effective braces go along the length of a panel, not across the short dimension. An initially counterintuitive result, but it explains why tranmission lines have clean bass. It's not that their loading is anything other than a degenerate reflex, it's that their panels don't boom.
I've had a look for that paper but it looks to be $33 from AES.

https://www.aes.org/e-lib/browse.cfm?elib=848

I did come across your article on the Arpeggio speakers on DIYAudio which discussed bracing.

https://www.diyaudio.com/community/thre ... er.158899/

I think the gist is:
- panels should be braced along their length
- don't use "ribs" use full width bracing to connect opposite sides (with plenty of holes cut inside)
- larger front surface area and shallower cabinets are better
- lighter materials "engineered" to be more rigid, or CLD type construction is good, but more tricky to construct

Is that a reasonable summary?

Misty's bracing looks pretty beefy (and that just sounds wrong).
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#162 Re: TG "The Loudspeaker" Build (Sort of)

Post by Morgan Jones »

I only have an ancient photocopy of the Tappan paper, but it really can be summarised by the "position braces to minimise the size of inscribed circles" idea.

Your summary of my box thoughts is correct, although I had to reread my article to realise that CLD = constrained layer damping.
Last edited by Morgan Jones on Wed May 15, 2024 1:53 pm, edited 1 time in total.
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#163 Re: TG "The Loudspeaker" Build (Sort of)

Post by Cressy Snr »

Constrained Layer Damping:
A layer of elastic material is sandwiched between two stiff materials. Basically the elastic material turns the vibration of the two stiff outer layers into heat.
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#164 Re: TG "The Loudspeaker" Build (Sort of)

Post by simon »

Morgan Jones wrote: Wed May 15, 2024 1:43 pm I only have an ancient photocopy of the Tappan paper, but it really can be summarised by the "position braces to minimise the size of inscribed circles" idea.
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#165 Re: TG "The Loudspeaker" Build (Sort of)

Post by MistyBlue »

simon wrote: Wed May 15, 2024 12:34 pm

Misty's bracing looks pretty beefy (and that just sounds wrong).

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