TheFlash

Teak Posselt Albatross - job done!

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Super Wammer
Posted (edited)
On 03/01/2020 at 22:24, Tony_J said:

Send me the cab dimensions and driver specs and I will give it a go...

Thanks Tony. If you can be bothered as, having already committed to duplicating the superficially identical black MDF ones, this is more out of academic intrigue than a practical concern.

Internal dimensions at base: 165mm x 165mm. Back panel is vertical, front panel slopes (straight not curved). Internal width maintained throughout, internal depth reduces to 0mm at an estimated height of 1600mm. If it was a straight box these dimensions would give 6.76 litres internal volume, so I think it must be 3.38 litres. I'm not at all sure if/how the shape affects the calcs, will leave that to you.

These same dimensions apply to the black MDF cabs too of course. It will be interesting to see how the two actual ports relate to the calcs.

Drivers on teak ones are:

For reference, drivers on black MDF ones are same Morel tweeter and

An intriguing exercise!

Edited by TheFlash
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Posted (edited)

Thanks Nigel. Couple more details...what (internal) height is the centre of the woofer above the base board? and what are the (internal) dimensions/location of the ports? (Internal diameter and length)

I'll have a go but may well be tomorrow/Monday before I get to it - visitors around until then.

Edited by Tony_J
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Super Wammer
3 hours ago, TheFlash said:

If it was a straight box these dimensions would give 6.76 litres internal volume...

That’s pretty tiny, if you consider that the smallest bookshelf ATC is just 7 litres.  I’ve not checked the maths though, just trying to think about an estimated volume.

 Interesting to speculate what the designer had in mind.  Did I read somewhere in another of your Posselt threads it was about lifelike imaging or height? 

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Super Wammer
1 hour ago, Nopiano said:

That’s pretty tiny, if you consider that the smallest bookshelf ATC is just 7 litres.  I’ve not checked the maths though, just trying to think about an estimated volume.

 Interesting to speculate what the designer had in mind.  Did I read somewhere in another of your Posselt threads it was about lifelike imaging or height? 

I make the volume 21.78 litres

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Super Wammer
44 minutes ago, Fourlegs said:

I make the volume 21.78 litres

Where did I go wrong?

65mm x 65mm x 1600mm = 6760cc = 6.76 litres. Divide by two as the profile is diagonal line across the box.

Be gentle.

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Super Wammer
1 hour ago, Nopiano said:

That’s pretty tiny, if you consider that the smallest bookshelf ATC is just 7 litres.  I’ve not checked the maths though, just trying to think about an estimated volume.

 Interesting to speculate what the designer had in mind.  Did I read somewhere in another of your Posselt threads it was about lifelike imaging or height? 

Yes, it was all about imaging I believe. I've only listened to the black ones for a few hours on various amps but my memory is of the sound sort of hanging there, neither boxed in nor with pinpoint accuracy.

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4 minutes ago, TheFlash said:

Where did I go wrong?

65mm x 65mm x 1600mm = 6760cc = 6.76 litres. Divide by two as the profile is diagonal line across the box.

Be gentle.

I suspect the 65mm should be 650mm. Possibly?

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Super Wammer
Posted (edited)
5 hours ago, Tony_J said:

Thanks Nigel. Couple more details...what (internal) height is the centre of the woofer above the base board? and what are the (internal) dimensions/location of the ports? (Internal diameter and length)

I'll have a go but may well be tomorrow/Monday before I get to it - visitors around until then.

Centre of woofers 750mm and 955mm above outside of base. Allow 20mm for thickness of wood at base: 730mm and 935mm.

The only port is the bass reflex port 110mm diameter. Not using external slider on this: https://www.ebay.co.uk/itm/132845277768

Edited by TheFlash
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Super Wammer
6 minutes ago, rabski said:

I suspect the 65mm should be 650mm. Possibly?

Yeah, I've cocked up haven't I... embarrassing reversion to inches!

165mm x 165mm x 1600mm = 43.56 litres /2 = 21.78 litres. Like Nick said. :$

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1 minute ago, TheFlash said:

Yeah, I've cocked up haven't I... embarrassing reversion to inches!

165mm x 165mm x 1600mm = 43.56 litres /2 = 21.78 litres. Like Nick said. :$

See. It turns out measurements are important :D

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Super Wammer
16 minutes ago, rabski said:

See. It turns out measurements are important :D

It's not size that matters, it's what you do with it.

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1 hour ago, TheFlash said:

It's not size that matters, it's what you do with it.

that's what Mrs. Flash said :D

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Super Wammer
5 hours ago, TheFlash said:

Yeah, I've cocked up haven't I... embarrassing reversion to inches!

165mm x 165mm x 1600mm = 43.56 litres /2 = 21.78 litres. Like Nick said. :$

That’s more like it!  About the volume of a largish stand mounted speaker, or about half that of the SCM40s. 

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Super Wammer
19 minutes ago, Nopiano said:

That’s more like it!  About the volume of a largish stand mounted speaker, or about half that of the SCM40s. 

:minikev:

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What an interesting project, I’m envious.

You certainly wouldn’t expect two pairs of speakers, ostensibly the same, to actually be so radically different given the more than superficial resemblance.

I’m not too surprised that MDF out performs solid teak as a cabinet material. Most solid wood “rings” with a higher resonance frequency than resinous MDF, so ironically the cheaper and “inferior” material is often the better choice for cabinet designs which are based on the principle of being heavily damped and inert. Mind you, I remember once using bitumen panels on a DIY modification to deaden the cabinet, only to find the sound was deadened too, losing most of its bounce and vitality, so things are not black and white.

I have never been to the Kegworth event, but I really will try this year, as I’d especially like to hear the results of your experiments.

If you need any geometry, volumes or other calculations performed, just let me know, as this is my field of work, and I will gladly help you. (see DIY tetrahedron speaker in caption).

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