Doc modding Marantz imperial 7

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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 14, 2017 5:53 pm

Yup!

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Tue Feb 14, 2017 5:56 pm

Some more pics.

Image

Shows the back panel switches etc. Might reuse it without the xover and switches and new binding posts for bi amping.

Image

Shows the xover components. All getting binned :grin:

Image

The cab i have not sanded back yet is damaged on the top and bottom edges if you can see it. The cab i have already sanded back was much worse. The damage went back 12mm and was a close call as regards being able to remove enough wood to get rid of the damage.

The baffle is causing me a bit of head scratching. Trying to think of the best thing to do as regards trying to fit in the 5" mid and visaton tweeter.I don't know if the baffle will come out with a bit of persuasion (hammer applied from inside). I am a bit wary of doing this. Other option is to stick a new baffle over the front with the correct cut outs and just cut away the minimum that is needed on the original baffle. That will make one hell of a thick baffle, especially when the steel plate goes on as well.

Found some 5mm angle iron in my shed which i was thinking of sticking in the cabs along all the internal joins, then filling in the holes with plate. Going to be quite a weight ! :dance:

Stu
DIY inspired by Richard "The Doc" Dunn RIP

duke_dayspring
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Re: Doc modding Marantz imperial 7

Unread post by duke_dayspring » Tue Feb 14, 2017 6:23 pm

Dr Bunsen Honeydew wrote:33mfd would be a lot more expensive for good ones. 3.3mfd tweeter, (approx) 33md mid.
Howdy Doc,
Sorry for having to ask, but after looking for russian paper in oils on ebay, i've confused myself - Are we talking milli-farads, or micro-farads here? Some sellers seem to list both with the same numerical value - bastards
Also, what should I look for in terms of voltage rating? Have something in my head about wanting high voltage values for crossover caps, as in 100v +
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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 14, 2017 6:33 pm

Farad is the unit of capacitance. It is named after Michael Faraday.
The farad measures how much electric charge is accumulated on the capacitor.

Table of capacitance values in Farad
name symbol conversion example
picofarad pF 1pF=10-12F C=10pF
nanofarad nF 1nF=10-9F C=10nF
microfarad μF 1μF=10-6F C=10μF
millifarad mF 1mF=10-3F C=10mF
farad F C=10F
kilofarad kF 1kF=103F C=10kF
megafarad MF 1MF=106F C=10MF

the Russian ones I linked to were μF

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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 14, 2017 6:47 pm

You could use the port hole for midrange (may need a little opening out) and use the extra smaller hole for a supertweeter, I know of some cheap ones that will do the job http://www.ebay.co.uk/itm/SoundLAB-Tita ... 1188082925 a horn does a good job for super tweeter, you bring it in only at extreme HF. 1mfd will do the job.

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Tue Feb 14, 2017 9:13 pm

Thanks Doc for the suggestions.

I know the port will definitely need opening out, i think it is about 4" from memory. I will look into enlarging it downwards. The mid driver hole would then need blocking somehow.

The tweeter linked to (thanks doc) needs a cut out of 88mm or there abouts. I try to avoid metal dome tweeters if possible but i may have to go with one.The visaton G25 only needs 80mm but the mounting plate on the front is 104mm. I need to have a good long think. It might be doable with the original baffle.

I love working out problems, gets the grey matter going. Being a perfectionist really is a pain in the arse sometimes. :-?

Is edge diffraction audible when installing drivers with no rebates routed out of the baffle ?

Thanks, 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 14, 2017 9:30 pm

You missed the point. I am talking about using the midrange hole for the tweeter, tweeter hole for the supertweeter, port hole for the midrange, bass driver hole for bass driver, no holes need to be blocked. That was the point :grin:

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu » Wed Feb 15, 2017 7:41 am

Oh, sorry Doc for not getting it. Very interesting. I will have a think about that.

Going to cut some circles out of card and play arrange the shapes on the front of my speaker.

Thanks Doc.
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Doc modding Marantz imperial 7

Unread post by duke_dayspring » Wed Feb 15, 2017 10:56 am

Dr Bunsen Honeydew wrote:Farad is the unit of capacitance. It is named after Michael Faraday.
The farad measures how much electric charge is accumulated on the capacitor.

Table of capacitance values in Farad
name symbol conversion example
picofarad pF 1pF=10-12F C=10pF
nanofarad nF 1nF=10-9F C=10nF
microfarad μF 1μF=10-6F C=10μF
millifarad mF 1mF=10-3F C=10mF
farad F C=10F
kilofarad kF 1kF=103F C=10kF
megafarad MF 1MF=106F C=10MF

the Russian ones I linked to were μF
Would these work for the tweeters then? :
http://www.ebay.co.uk/itm/3-3-uF-500-V- ... NYI651sony ps lx310
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Dr Bunsen Honeydew
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Re: Doc modding Marantz imperial 7

Unread post by Dr Bunsen Honeydew » Wed Feb 15, 2017 11:18 am

Yes.

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