Doc modding Marantz imperial 7

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

I keep saying this but my design is finished once I have tried these doped 6.5 inchers in a bipole configuration (up and down firing). If I am honest the 30cm cube I had with up and down firing 5.25 inchers and four tweeter tweeter pod was the best thing I have ever heard. Not missing the isobaric 12 inchers at all :dance:

The essential things in this design for me are (not in order of importance)

1) it must be a cube - that limits driver size and number of. if the box is to remain an acceptable size (30cm cube about my max but can go up to 32 cm3 if needed))
2) filterless mid bass is a must
3) no mid bass front or side firing allowed
4) bipole (opposing drivers in phase) - twice as many drivers dramatically reduces IM distortion, brings baffle step compensation for free :dance: and cancels most of the cabinet vibration especially if the back of the two opposing drivers are mechanically linked. Don't underestimate the effect of this one :naughty:
5) tweeter(s) must be behind the up firing mid bass - the increase in clarity and imaging was quite startling
6) multiple tweeter's firing in different directions bring decreased distortion & detail, better off axis listening and atmospheric sound
7) it sounds like real musicians in a real band who are at the top of their game and having lots fun therefore so am I
8) the band is not squirted at you through a funnel :lol:
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Latteman (Wed Jan 06, 2021 10:27 am) • Ithilstone (Wed Jan 06, 2021 10:41 pm)
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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

I have enlarged my cabs a little, making them approx 4 cm taller so they are not exactly a cube but it will have to do for now whilst I try the bipole 6.5 inchers. The 30 cm3 cab was slightly oversized for the 5.25 inch drivers which resulted in a very well behaved bass response when right up against the wall.

I might find that these slightly bigger 34 x 30 x 30 cabs are too small but it won't be by much. Although the 6.5 inchers have a bigger VAS they have a lower Qts. They might not be able to go all the way to the wall like the bipole 5.25 inchers but we shall see. If that is the case I will slightly increase the box volume to 32 cm3 and see what that does.
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Still can't decide if these speakers should have separate stands or if the stand should be integral to the cabinets :think: Stands would be easier and i have enough solid metal bar in brass , aluminum or stainless steel to make them. Aluminum 6 mm plate is available as well. The intention is to make this part of the speaker as strong as heavy as I can. (rightly or wrongly)

If I go stands then the top plate of the stand will reguire a 165 mm hole in it to let the down firing driver do it's thing. Three or four legs ? Can't decide :think:

If the stands are integral then I will have to drop the quartz tile idea and make the speakers out of wood I think. Not sure yet. Anyway, the idea would be to have the cabinet back panel extend all the way to the floor, attach a floor "plate" and then have one or two legs at the front.

Decisions, decisions :roll:
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Re: Doc modding Marantz imperial 7

Unread post by Latteman »

I tried stands based on heavy principles but found if cabinets are heavy then spikes to a support surface are good for agility rather than anything else I used
Your cabinets are big enough to stand on their own so try spikes to floor
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

:dance: :dance: :dance:

Cube's with bipolar (up & down firing in phase) 6.5 " mid bass are now up and running :guiness;

Image

I reused some baffle's that I made for the 5.25 " mid bass and made the cut out's bigger which wasn't easy to do neatly but got it done. The little tweeter "pod" only just fits behind the 6.5 incher. When I make the final build the mid bass will need to go a bit further forward to make a little more room.

Image

I joined the two opposing woofers mechanically with black plastic down pipe with holes cut in the sides like before. Works a treat once you have them just the right length. Hardly any cabinet vibration even with this crappy chipboard (when i say crap I mean really crap).

Mounted the drivers externally as I couldn't be arsed doing it the other way which takes longer and I couldn't wait to hear them.
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

That's it then. The journey is over and I have finally found my ideal speaker :dance: Only taken four years, countless drivers, bits of chipboard and 110 pages of this awful thread.

Maybe I shouldn't count my chickens too soon as these drivers are yet to run in. A touch more dope might be required but it is there or thereabouts. I have only applied the bison kit twice and no plastidip as yet but maybe that was just to make the whole thing a uniform colour ?

The box could do with being just a little larger I think. Currently I have 20 litres but I think another litre or two would be better . 30cm cube with 10mm walls (quartz tiles) gives an internal volume of 22 Litres. A 32cm cube with 20mm walls (wood & steel) would also be 22 Litres internal volume.

I won't be trying a bipole with 8 inchers as it will get too big and will need to be two 30 cm cubes on top of each other and I'm not going there. Will over power my room anyway. I have got to the limit of displacement and box size for my living room at home. I could easily live with the bipole using two 5.25 inchers but I think this one using 6.5 inchers is going to surpass it.
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Latteman (Wed Jan 06, 2021 6:00 pm) • Ithilstone (Wed Jan 06, 2021 10:32 pm)
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Here's an option I never thought of (until now) - a down firing 6.5" and an up firing 5.25" :think:
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Re: Doc modding Marantz imperial 7

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Stop Stop ✋
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karatestu (Thu Jan 07, 2021 11:24 am)
Analogue Source -
Denon DP47f- Ortofon mc20 supreme
Ifi Zen Phono
Doug Self balanced Pre amp
Akai 4000DS mk2 R2R
Digital Sources- IfI stream, Ifi Neo idsd Dac; Tidal / Radio Paradise
Amplification Nva 30vdc mono blocks
Speakers Lii Audio F-15 in Open Baffle; Ls6
Weiduka AC8.8- for digital sources
Mini BMU for analog sources

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Re: Doc modding Marantz imperial 7

Unread post by Ithilstone »

karatestu wrote: Wed Jan 06, 2021 4:28 pm I won't be trying a bipole with 8 inchers as...
Bugger I was actually waiting for this one most of all... ;]
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karatestu (Thu Jan 07, 2021 11:24 am)
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Re: Doc modding Marantz imperial 7

Unread post by Ithilstone »

Latteman wrote: Wed Jan 06, 2021 10:36 pm Stop Stop ✋
NOOOOO don't say that - Stu needs to carry on - he needs it as we need air ;] plus it is massively entertaining ;]
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karatestu (Thu Jan 07, 2021 11:24 am)
Nothing to see here...
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