Doc modding Marantz imperial 7

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Fri Jan 03, 2020 10:16 am

Ways to increase the efficiency of these speakers

* add more 5.25" mid bass drivers. The greatest increase in dB comes from having them closely coupled. That means having a few of them mounted on the top baffle as close together as possible. If the mids have their own amplifier then with clever wiring i can make a 4 ohm load which demands more current from the amplifier but still within safe margins. The load will be easy as there is no xover. Adding more drivers increases the required box volume though so no free lunch here.

The mids have the lowest efficiency out of all the drivers so adding more of these would be the way to go. Help from the room at the very lowest frequencies means i will not have to add more 12" bass drivers. Can't afford the extra box volume required anyway unless i go the in floor infinite baffle route (not written that off by any means).

Although i have added multiple tweeters the series wiring limits their output as does the fact they are not closely coupled (on different baffles).

*start with more efficient drivers - not going to happen, i am too invested in these drivers and at £10 a pop what's not to like. I have loads of bisonkit so it's a no brainer.

So i am going to end up with forward or up firing isobaric 12" bass drivers wired in parallel (or non isobaric in floor infinite baffle), several 5.25" mid bass wired in a combination of series and parallel depending on how many of them, several tweeters wired in a combination of series and parallel depending on matching output with the 5 inchers.
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 » Fri Jan 03, 2020 5:07 pm

I have managed to knock together a rough upper enclosure to house two 5" drivers (one up firing and the other down firing) and four Visaton tweeters (one up firing, one front firing and one to each side).

In the spirit of recycling as much as possible the side, front and back panels are 14cm x 2.5cm decking boards :lol: . I put the ribbed side to the inside of the cab and had to seal a few gaps at the corners :roll: Worked out well and its very solid. I chose them as the boards gave me just the right amount of height for the enclosure. Don't know what the treads will do for the back wave inside the cabinet. The top and bottom are made of crappy chipboard as you have come to expect from me.

Image

Shows the bottom panel of the enclosure with just the down firing 5" and the front firing and one side firing tweeter


Image

Shows the top panel with up firing 5" and hole for tweeter



This is going to be put on four legs (one in each corner) and placed above the lower bass cab with up firing isobaric pair of 12 inchers. Grille fabric will cover the area between the two cabs. Still needs some work on the driver rebates and a few other things. Not to forget i have two drivers to dope.
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 » Fri Jan 03, 2020 5:13 pm

It's obviously not a cube but to keep the height of the speaker down to a reasonable level i had to do this. If it gives me problems then a redesign will have to be done. The two 5" drivers are exactly in line so hopefully i can use threaded rods to attach the drivers to the baffles and provide some bracing at the same time (if it works out).

The 5.25" mid bass looks a bit lost in that panel all on it's own :lol:
DIY inspired by Richard "The Doc" Dunn RIP

Alfi
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Re: Doc modding Marantz imperial 7

Unread post by Alfi » Fri Jan 03, 2020 5:15 pm

This is what Doc loved Stu.. Chainsaw DIY and looking great for it! :clap: :clap: :clap:

Though having a fluted LP12 I'd have had the ribbed face to the outside just as a tongue in cheek a'hem, homage to Linn's DMS Briks :lol:

Alfi.
Heavily modified suspended sub-chassis turntable, Sole VIII sub-chassis, "In Sole" advanced polymer suspension, Ai bearing, Alphason HR100MCS, AT 33PTG, Norton Airpower clone. Technics SL110A, AT 1005, Soundsmith Denon DL103. Voyd the Voyd, ATP-12T, AT 33PTG. NVA BMU, NVA Phono 2 MC (2 power supplies), NVA P50 SA, NVA A40 Mk1 power amps, custom birch ply Allison 6/NVA Cube 1 clones, NVA TIS mk2 , SSC, LS6.

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Fri Jan 03, 2020 6:36 pm

Alfi wrote:
Fri Jan 03, 2020 5:15 pm
This is what Doc loved Stu.. Chainsaw DIY and looking great for it! :clap: :clap: :clap:

Though having a fluted LP12 I'd have had the ribbed face to the outside just as a tongue in cheek a'hem, homage to Linn's DMS Briks :lol:

Alfi.
Cheers Alfi :grin: I know doc enjoyed the Heath Robinson aspect of my bodgeneering. Unfortunately no chainsaw was hurt in the production of this. Just a chopsaw, jigsaw and hole saws.

This chopsaw to be exact

Image

I never thought about putting the fluted side on the outside as a Linn piss take :lol: :lol: :lol: I would do it but sealing the hole and the diffraction would have been a nightmare :shock:
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 » Fri Jan 03, 2020 6:45 pm

A reminder of how this adventure started 73 pages and three years ago.

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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 » Fri Jan 03, 2020 7:09 pm

Lookin good
Analogue- ARB modified Funk Firm Vector; Ortofon Mc 10 & MCa step up to Yaqin phono stage
Digital Sources- Little Dot Dac1, Musical Fidelity E600 & Apple TV
Amplification-NVA P20 & A20 (both modded)
Speakers- Diy BBCubes; 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 » Fri Jan 03, 2020 7:23 pm

I do intend to do something with those cabs. It took ages cutting the shed load of steel, painting it with hammerite and gluing in. There are some cheap Mivoc 12" drivers that will go nicely in these once doped. Their Vas is much lower than the doped kevlar ones and about right for the Marantz enclosure. An up firing 5" and front firing tweeter will finish the job off.

:dance:
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 » Fri Jan 03, 2020 7:31 pm

Latteman wrote:
Fri Jan 03, 2020 7:09 pm
Lookin good
Cheers Peter. I wouldn't go that far though :lol: :lol:

Having cut all four tweeter holes for the Visaton G25ffl tweeters, i need to buy six of the buggers. That's gonna hurt. Oh and another cab to do for the other channel :shock: When does it all end ?
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 » Fri Jan 03, 2020 7:48 pm

It never ends as then the listening and tinkering starts
Analogue- ARB modified Funk Firm Vector; Ortofon Mc 10 & MCa step up to Yaqin phono stage
Digital Sources- Little Dot Dac1, Musical Fidelity E600 & Apple TV
Amplification-NVA P20 & A20 (both modded)
Speakers- Diy BBCubes; Ls6
Mini BMU to dc blocker

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