Concrete Cube

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jimbob
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Re: Concrete Cube

Unread post by jimbob » Tue Jun 11, 2019 3:59 pm

Does anyone know if Richard mentioned his thinking behind using the 5.25 inch driver as a midrange as opposed to the 6.5 inch?
Squeezebox Touch - Colin Wonfor mini pre - EWA M50 Power Amp - Modified NVA Cube 2 mk1 - SSP MK2 - LS6

NVA P90sa - NVA A60 MK1 - DIY Cubettes - SSC - LS3

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karatestu
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Re: Concrete Cube

Unread post by karatestu » Tue Jun 11, 2019 4:49 pm

No i don't think he did and if we had asked he probably wouldn't have given too much away :grin:

But i would think that it is more suited to the role. I think smaller cones tend to play the higher frequencies in a more stable manner without so many spikes in the curve. But then we want to attenuate the higher frequencies with doping :think: Also with the tweeter having only a single series capacitor to roll it off and protect from DC we don't want the tweeter to be going too low. They are more fragile after all.

Maybe it was also down to cost :o who knows. I am sure a 6.5" would work and so would a 8" as they do with the cube 2 and 1 designs. But we have a big 12 incher already covering bass duties. The mid obviously helps with this. I would say that it would be a suck it and see situation. If you are lacking in bass with a 12 incher (highly unlikely) then go for a bigger mid.
DIY inspired by Richard "The Doc" Dunn RIP

Daniel Quinn
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Re: Concrete Cube

Unread post by Daniel Quinn » Tue Jun 11, 2019 5:02 pm

Richard would have said. Try a 6inch for yourself and report back.

jimbob
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Re: Concrete Cube

Unread post by jimbob » Tue Jun 11, 2019 5:10 pm

Dan, I think that’s exactly what he would have said!

Stu, when used in an isobaric configuration do the bass units have to be doped differently. On one hand I’m thinking not but I seem to remember Richard saying that the top unit has the least doping, the middle a bit more then the bottom driver gets doped the most???
Squeezebox Touch - Colin Wonfor mini pre - EWA M50 Power Amp - Modified NVA Cube 2 mk1 - SSP MK2 - LS6

NVA P90sa - NVA A60 MK1 - DIY Cubettes - SSC - LS3

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karatestu
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Re: Concrete Cube

Unread post by karatestu » Tue Jun 11, 2019 5:21 pm

Mine are doped the same. I also remember Richard saying the cubix had progressively lower amounts of doping applied as you got to the last one. But we have a different situation here. We are not relying on one driver to do mid and bass. I think the last one probably had the same amount of dope as the cube 1 otherwise there would be a hole in the frequency response just before the tweeter took over.
DIY inspired by Richard "The Doc" Dunn RIP

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karatestu
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Re: Concrete Cube

Unread post by karatestu » Tue Jun 11, 2019 5:23 pm

And then what confuses matters further is the mids are sharing the enclosure with the bass driver.
DIY inspired by Richard "The Doc" Dunn RIP

jimbob
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Re: Concrete Cube

Unread post by jimbob » Tue Jun 11, 2019 5:33 pm

Have you heard the bbcube to determine how that affects the midrange driver?
Squeezebox Touch - Colin Wonfor mini pre - EWA M50 Power Amp - Modified NVA Cube 2 mk1 - SSP MK2 - LS6

NVA P90sa - NVA A60 MK1 - DIY Cubettes - SSC - LS3

jimbob
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Re: Concrete Cube

Unread post by jimbob » Tue Jun 11, 2019 6:07 pm

Also, how cube does the cube have to be? I’m pretty sure an upward firing driver would also work in a rectangular box too??
Squeezebox Touch - Colin Wonfor mini pre - EWA M50 Power Amp - Modified NVA Cube 2 mk1 - SSP MK2 - LS6

NVA P90sa - NVA A60 MK1 - DIY Cubettes - SSC - LS3

jimbob
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Joined: Wed Sep 26, 2012 8:35 pm
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Re: Concrete Cube

Unread post by jimbob » Tue Jun 11, 2019 6:12 pm

I’m thinking 355mm mdpe gas pipe. Wall thickness of approximately 20mm. Capped off at the bottom with 25mm plywood. A plywood insert at the top with a cut out for the bass driver. I haven’t decided on the length of the tube yet. A hole cut in the front for the tweeter and one in the side for the midrange.
Squeezebox Touch - Colin Wonfor mini pre - EWA M50 Power Amp - Modified NVA Cube 2 mk1 - SSP MK2 - LS6

NVA P90sa - NVA A60 MK1 - DIY Cubettes - SSC - LS3

jimbob
Posts: 639
Joined: Wed Sep 26, 2012 8:35 pm
Great Britain

Re: Concrete Cube

Unread post by jimbob » Tue Jun 11, 2019 6:13 pm

To make things simpler it could just be a 2 way using the 8 inch and a tweeter. Should be fairly heavy as it is but a cylinder could be lined with lead to add mass...
Squeezebox Touch - Colin Wonfor mini pre - EWA M50 Power Amp - Modified NVA Cube 2 mk1 - SSP MK2 - LS6

NVA P90sa - NVA A60 MK1 - DIY Cubettes - SSC - LS3

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