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Re: Doc modding Marantz imperial 7
Posted: Wed Jun 23, 2021 3:58 pm
by karatestu
Making a thinner faceplate.
Sheet copper, brass or aluminum can be had in thicknesses of 0.4mm and 0.5mm. That should be strong enough for my needs. I have some 0.7mm copper sheet. Will the extra 0.3mm thickness matter in the grand scheme of things ? Copper isn't the easiest metal to work with but could be polished up to quite a shine
The steel faceplates I took off are 2mm plus a thin sorbothane layer.
Re: Doc modding Marantz imperial 7
Posted: Wed Jun 23, 2021 4:17 pm
by karatestu
Found some 38cm (15") stainless steel balls on Amazon. Slightly too big but wow. They do smaller ones too.
Stainless is hard to work and don't know it's acoustic properties. The listing doesn't give a wall thickness.
But
Re: Doc modding Marantz imperial 7
Posted: Wed Jun 23, 2021 5:09 pm
by karatestu
I think those stainless steel balls are too thin walled (1mm) to be any good unfortunately.
Re: Doc modding Marantz imperial 7
Posted: Thu Jun 24, 2021 12:38 pm
by karatestu
Good news (some) from the acrylic sphere supplier.
Yes I can have 350mm acrylic spheres with the opposing ends cut off for the bipolar drivers. They won't be able to do any thicker than 4mm wall thickness but that should be ok as it's a sphere and the holes in the two ends are small compared to the sphere diameter. The other bad news was they can't supply in black, only clear or opal (cloudy).
So, I either get opal and put some coloured LED's inside
or paint them with acrylic paint. Paint the insides or outside ?
The price inc cutting the ends off seems reasonable so I am putting together an email with what I want and a pencil drawing or two. Exciting
Re: Doc modding Marantz imperial 7
Posted: Thu Jun 24, 2021 1:44 pm
by Geoff.R.G
karatestu wrote: ↑Thu Jun 24, 2021 12:38 pm
Good news (some) from the acrylic sphere supplier.
Yes I can have 350mm acrylic spheres with the opposing ends cut off for the bipolar drivers. They won't be able to do any thicker than 4mm wall thickness but that should be ok as it's a sphere and the holes in the two ends are small compared to the sphere diameter. The other bad news was they can't supply in black, only clear or opal (cloudy).
So, I either get opal and put some coloured LED's inside
or paint them with acrylic paint. Paint the insides or outside ?
The price inc cutting the ends off seems reasonable so I am putting together an email with what I want and a pencil drawing or two. Exciting
I'd leave them unpainted.
Re: Doc modding Marantz imperial 7
Posted: Thu Jun 24, 2021 2:45 pm
by Latteman
Have u ever considered / researched a half cube / half sphere- a domed cube?
Top driver in the sphere half
Re: Doc modding Marantz imperial 7
Posted: Thu Jun 24, 2021 2:48 pm
by karatestu
Latteman wrote: ↑Thu Jun 24, 2021 2:45 pm
Have u ever considered / researched a half cube / half sphere- a domed cube?
Top driver in the sphere half
No, never thought about that configuration. I can't see it being as good as a full sphere. You have PM peter.
Re: Doc modding Marantz imperial 7
Posted: Thu Jun 24, 2021 2:49 pm
by karatestu
Geoff.R.G wrote: ↑Thu Jun 24, 2021 1:44 pm
I'd leave them unpainted.
Why is that Geoff ?(if you don't mind me asking).
Re: Doc modding Marantz imperial 7
Posted: Thu Jun 24, 2021 3:08 pm
by Geoff.R.G
Well, partly to get you to ask but mainly because, if you paint the spheres you won't know what they sound like unpainted. If you build them unpainted and then use them you can decide later whether painting them is/might be a good idea. Painting will make a difference but why not find out what the plain acrylic sounds like first?
Re: Doc modding Marantz imperial 7
Posted: Thu Jun 24, 2021 3:39 pm
by karatestu
Geoff.R.G wrote: ↑Thu Jun 24, 2021 3:08 pm
Well, partly to get you to ask but mainly because, if you paint the spheres you won't know what they sound like unpainted. If you build them unpainted and then use them you can decide later whether painting them is/might be a good idea. Painting will make a difference but why not find out what the plain acrylic sounds like first?
Thanks for your suggestion Geoff. I will do as you suggest. I would go for the opal which is a milky white colour and often used in plastic lamp shades. It's a pity these spheres can't be done in black . You can get black hemispheres and join the two together but the join will be visible and the whole thing not as strong.
Painting acrylic is a tough job i.e you have to prepare the surface really well and use the right primer which does not react with the acrylic and which will adhere well to it. Acrylic paint seems to get recommended.