Doc modding Marantz imperial 7

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Firebug1
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Re: Doc modding Marantz imperial 7

Unread post by Firebug1 »

That is going to an epic build up 😀
Rega by Michael Lim\Teac\NVA\SA Mantra30\AQ Nightowl Carbon
...the Gods you worship are steel, at the altar of rock 'n' roll you kneel...

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Latteman
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Re: Doc modding Marantz imperial 7

Unread post by Latteman »

😎🤪
Epic
Analogue- DIY turntable donor from Thorens TD321, DIY Tonearm; Nagaoka SB mp200- Yaqin M-23B
Digital Sources- Denon CEOL streamer/Cdp; iPhone Xr; Cat7 & 8
Amplification-NVA P20 (modified) & A20LE (👍🏼)
Speakers- Diy ‘Isobaric Cubes’; Ls6
Dc blocker to mini BMU

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Latteman
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Re: Doc modding Marantz imperial 7

Unread post by Latteman »

Hi Stu- u are further along on your quest, I’m still designing
Got these to try-

https://www.ebay.co.uk/itm/254568265860

I have replaced the linn tweeters in my small cubette clones- currently no resistor as the previous units matched the Royd 5” mid bass up firing driver
It’s more detailed but also louder almost shrill compared to previous tweeters
Using the denon all in one as a pre it allows me to adjust the dB of the ‘treble’ which helps reduce volume/ shrillness a lot but I feel it also affects detail
I can either add a ‘padding resistor’, change the cap value or change the Royd to a 16ohm Richard Allen driver.
Oh the joy🤣
Analogue- DIY turntable donor from Thorens TD321, DIY Tonearm; Nagaoka SB mp200- Yaqin M-23B
Digital Sources- Denon CEOL streamer/Cdp; iPhone Xr; Cat7 & 8
Amplification-NVA P20 (modified) & A20LE (👍🏼)
Speakers- Diy ‘Isobaric Cubes’; Ls6
Dc blocker to mini BMU

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

I can't find any pics on the net of cream speakers but a few white ones. :(

Peter, you just need to add several more tweeters that will sort it right out :grin:
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Latteman (Sat Aug 15, 2020 3:20 pm)
DIY inspired by Richard "The Doc" Dunn RIP

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Over the last few weeks I have had small bits of time here and there to get on with these concrete bass cabinets. It's slow progress and quite labour intensive. With the use or a circular saw & track, various squares and rulers I have cut the panels for one speaker. Two 30 cm wide & two 40 cm wide. They fit together very nicely to make a structure 40 cm (w) x 40 cm (d) x 60 cm (h).

But I am removing some of the concrete as I thought 5 cm panel thickness was a bit over the top. Tapping them gives a nice low thud. So after cutting the panels (slabs) I set about removing the unwanted material to make them 2 cm thick with blocks for bolting them together. I am going to use glue as well but thought I should bolt them in each corner and half way down each side.

Here is one 40 cm x 60 cm panel being seen to with a hammer and chisel.

Image
DIY inspired by Richard "The Doc" Dunn RIP

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Have to be very careful knocking the bits out so as not to break the piece which would mean starting again. If you have ever worked with stone and concrete you will know what I mean.

Here is a 30 cm x 60cm panel which has had all the excess concrete removed. It's a right pain in the arse to do.

Image

Doing it like this gives me as much internal volume as I can get relative to the outside dimensions. Imagine just using 5 cm thick slabs - I think that is overkill personally and wasting a lot of space never mind the weight. The slabs are much lighter when the material has been removed. Plus, their resonant frequency has changed. Tapping a carved one and then an untouched one it is evident that the resonant frequency is higher now.
DIY inspired by Richard "The Doc" Dunn RIP

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

I like the rough and uneven texture of the inside of the panel. It may help with internal sound waves or it may not (bollox alert :law-policered: ). It is quite satisfying when tapping away with a hammer and chisel and then suddenly the pitch changes and you are aware that the concrete has given, a crack appears and then the piece comes away.

Anyway, I have only done two of the panels so far and here is the pile of little cubes removed from the slabs.

Image

Because I did this mainly when it was raining I was forced to do it in one of the farm buildings. Now everything in there is covered in white concrete dust including my Daihatsu Fourtrak :roll:
DIY inspired by Richard "The Doc" Dunn RIP

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Here's a pic of the panels put together with only two which have had concrete removed. You will get the gist.

Image

The slabs are a bit rough looking but once power washed, plastered and sanded they should be ready for the final finishing. Can't get any plaster at the moment though :cry: Never mind, I have two more slabs to remove concrete from and then start on the other speaker.

Image

The circular saw and track really did a good accurate job as all the panels fit together very nicely. The saw is an evolution which you power tools snobs will no doubt be turning your nose up at right about now :music-tool: :obscene-buttred: . But it did an excellent job. I had to adjust it a little when I first got it because the blade was not exactly 90 degrees to the base but that was easy to do and now it just gets on with the job.
DIY inspired by Richard "The Doc" Dunn RIP

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Next tool on the shopping list is a router. Will be essential for the wooden upper enclosure. Apparently you can use it on aluminum (with the right bit I assume) so I will also use it to cut the hole in the aluminum baffle for the bass drivers. If that turns out to be bollox then it will have to be the multiple drill hole method all around the inside of the hole and a jigsaw. Angle grinder to finish off. I hope I can use a router as it will be a lot neater (and quicker) although not externally visible (except to my inner most thoughts).
DIY inspired by Richard "The Doc" Dunn RIP

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Latteman
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Re: Doc modding Marantz imperial 7

Unread post by Latteman »

Bloody ell
Cracking job- real labour of love ✅
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karatestu (Wed Aug 26, 2020 6:20 am)
Analogue- DIY turntable donor from Thorens TD321, DIY Tonearm; Nagaoka SB mp200- Yaqin M-23B
Digital Sources- Denon CEOL streamer/Cdp; iPhone Xr; Cat7 & 8
Amplification-NVA P20 (modified) & A20LE (👍🏼)
Speakers- Diy ‘Isobaric Cubes’; Ls6
Dc blocker to mini BMU

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