Doc modding Marantz imperial 7

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Tue Feb 07, 2017 5:00 pm

Thanks for the encouragement and good luck messages.

Ok Doc, will transfer funds in the next week, thanks.

There are two visaton tweeters mentioned on HFS. G20 and G25. G25 is slightly larger - is this the one to go with if space allows ?

I may need some advice with getting the xover (the few components there are) correct.

Bass driver - nothing
Mid - parallel cap ?, maybe series resistor ?
Tweeter - series cap and resistor

Having never played with a 3 way before I have some homework to do.

Stu
DIY inspired by Richard "The Doc" Dunn RIP

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Dr Bunsen Honeydew
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Re: Doc modding Marantz imperial 7

Unread post by Dr Bunsen Honeydew » Tue Feb 07, 2017 5:46 pm

G20 will be fine, or G25 if you want.

There will be two ways to do the bass and mid 1/ (Recommended) the drivers wired in series and no crossover components or padding. 2/ wired in parallel with a series capacitor of about 33mfd (adjust by ear) to the mid unit.

The tweeter done as usual with 3.3mfd cap and 12 ohm pad.

KISS applies (keep it simple)

Daniel Quinn
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Re: Doc modding Marantz imperial 7

Unread post by Daniel Quinn » Tue Feb 07, 2017 5:50 pm

When I built my 3 way floorstanders , I wired the 8 inch and 6 inch focal drivers in series with no capacitor and much preferred it , that was the first bit of advise the doc gave me nearly 8 years ago now .

but as always you should try for yourself for the sake of two 3.3uf capacitors [ about 10 quid from maplins}

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Dr Bunsen Honeydew
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Re: Doc modding Marantz imperial 7

Unread post by Dr Bunsen Honeydew » Tue Feb 07, 2017 5:53 pm

33mfd would be a lot more expensive for good ones. 3.3mfd tweeter, (approx) 33md mid.

Daniel Quinn
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Re: Doc modding Marantz imperial 7

Unread post by Daniel Quinn » Tue Feb 07, 2017 5:57 pm

oops yes it would , the price I quoted was for 3.3uf ;) not sure you get such a value from maplins


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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Wed Feb 08, 2017 7:20 pm

Speakers turned up today. I should be happy but 2 of the front corners are damaged by parcelfarce. Got them from a charity and their packing was very poor , one cardboard box around each speaker and nothing else. I am a bit mad :angry-screaming: :angry-screaming: :angry-screaming: but cant be arsed sending them back. Some bodging required.
DIY inspired by Richard "The Doc" Dunn RIP

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Dr Bunsen Honeydew
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Re: Doc modding Marantz imperial 7

Unread post by Dr Bunsen Honeydew » Thu Feb 09, 2017 12:00 pm

Can you repair them or back to square one.

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Thu Feb 09, 2017 6:00 pm

I am going to have a go at repairing them.

The front edges protrude 16mm in front of the baffle and one corner is damaged a good 12mm back ! the other speaker is not as bad.

I think there are two options.

1) Repair by gluing in some wood and finding some walnut veneer as close as a match as I can find

2) Remove the cabinet "bumper" that sticks out 16mm all the way around. This would bring it back to the same level as the front baffle. I would then probably paint or veneer the front baffle and the exposed chipboard that will be all the way around the perimeter of the cab. I could make new grilles that cover the entire front rather than the original ones that sit within the "bumpers". The original grilles are a bit grotty anyway.

The other problem I have come across is trying to fit all the drivers in. The 5" mid will be a problem and it wont fit in the port hole. I might have to do some serious bodging with this. I need more time to work this all out. Putting a whole new baffle on the front of the existing one may be an option here - a 19mm sheet of Baltic birch might do the job.

I have a lot of chin scratching to do.

Stu
DIY inspired by Richard "The Doc" Dunn RIP


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