Doc modding Marantz imperial 7

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Latteman
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Re: Doc modding Marantz imperial 7

Unread post by Latteman »

Massive!
Analogue- DIY turntable from Thorens TD321, ARB unipivot Arm; Nagaoka SB mp200- phono 1
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Amplification-NVA P20 (modified) & A20LE (👍🏼)
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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

It will be 40cm x 40cm x 90cm when finished (16" × 16" × 36" in old money), unless the design changes again :roll: . Not big by Lindsay T's standards. Bigger than average though :grin:
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 »

Mine are 39x39x39” ish & I think they are big! & heavy so yours are gonna need a hernia
Analogue- DIY turntable from Thorens TD321, ARB unipivot Arm; Nagaoka SB mp200- phono 1
Digital Sources- Denon CEOL streamer/Cdp; iPhone Xr; Airport Express Cat7 & 8
Amplification-NVA P20 (modified) & A20LE (👍🏼)
Speakers- Diy Cubes; Ls6
Mini BMU to dc blocker

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

I have got some of the drivers mounted in the new enclosure. For a while i will be using the tweeters i already have until i can stomach dropping £410 on 6 visaton G25 ffl. :shock: i have just the two visaton tweeters and one of the 5 inchers left to do, and then all the wiring.

Made some adapter plates to fit in the driver rebates i have already made for the visatons for a much better fit than the way i had it before (tweeters taped on the side :lol: ).

As far as amps go i have not built my last two nva amps yet, so the mid drivers will have to be in parallel with the tweeters. Two 5 inchers wired in series and the series wired tweeters in parallel with them. Don't know if i dare risk putting the mid drivers in parallel and the tweeters in parallel with them. The impedance will be too low i think.
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 »

Latteman wrote:
Thu Jan 09, 2020 8:58 pm
Mine are 39x39x39” ish & I think they are big! & heavy so yours are gonna need a hernia
I have a sack barrow :lol: plus they are floorstanders so dont need lifting up. At least my kids wont be able to knock them over :lol: Being made of two sections that will make moving easier.
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Doc modding Marantz imperial 7

Unread post by Toontrev »

Thanks Stu for a fantastic, informative and entertaining thread, I don't think I've missed an episode.

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Toontrev wrote:
Fri Jan 10, 2020 11:57 am
Thanks Stu for a fantastic, informative and entertaining thread, I don't think I've missed an episode.
You're welcome :grin: Thanks for tuning in. I did feel like i was talking to myself for a while but then i should get over myself and expect that . I do try and make it interesting and informative with some recycling and heath robinson construction rolled in. Some of my conclusions may be all wrong but then you gotta trust yer ears.

On page 75 now :shock: I am sure i can make it 100 before it's over :guiness;
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

:dance: :dance: :dance: I have them up and running :dance: :dance: :dance:

It was a race this evening to get the speakers wired up internally. Only got 15 mins of listening time as i had to go home for my tea :cry:

I put the new 5" drivers up firing so i can dope them on the fly. Original 5 incher is down firing with magnet out. Visaton tweeter is font firing, B&W one is up firing, Mordaunt short tweeter is in firing and the full rangers used as tweeters are out firing.

The small full range drivers are open backed so i had to make a sort of back box for it. I cut out a circle of hardboard and stuck it on the inside of the cut out. The driver's depth when mounted is 1mm less than the thickness of the decking board so all i had to do was stick on the hardboard circle with decorators caulk which sealed all the holes. I had to route the wires down one of the decking board channels :grin:

The new upfiring 5 " mid bass have only had two thin coats of plastidip so far. I can't quite believe it but i am not sure they need any more doping :shock: :shock: :shock: . In my set up with multiple drivers it sounds damn fine.

It is very early days and i have only listened for 15 mins but the sound is so effortless, textured and detailed. Doubling up on the 5 " drivers has brought similar benefits to adding more tweeters. I am getting good at knowing what distortion sounds like as i keep stripping it away. The reduction in distortion is quite amazing. I am over the moon with the sound it is silky smooth and extremely dynamic with more hidden detail emerging from the reduction in distortion.

It sounds quieter but then RD always said that when we thought things were loud it was actually distortion. Splitting the work of one driver in to two really does reap large rewards with these cheap Chinese PA drivers. The drivers are moving much less (less excursion ) .

More to come when i have listened more :guiness;
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 remember the law of diminishing returns kicked in after adding the first additional tweeter. Further tweeters did bring improvements but nothing like the improvement from adding thr first.

I wonder if adding more 5" drivers will bring any improvements. I have room for two more on the top baffle :dance: At £10 a pop it would be rude not to :lol: Not sure the enclosure volume is big enough though :cry:
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 »

More thoughts. All theoretical of course and may or may not be happening.

I have the up firing 5 incher cone outwards and the down firing 5 incher magnet outwards and wired out of phase with the other. This is what is called a push pull arrangement and has it's own distortion reduction on top of that gained by sharing work out between two drivers.

Also by having two drivers on opposite sides of the enclosure there is some force cancellation. I have noticed that the top enclosure panels are vibrating much less now :dance: The extensive bracing must be helping with that.
DIY inspired by Richard "The Doc" Dunn RIP

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