Doc modding Marantz imperial 7

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karatestu
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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Latteman wrote:
Fri Jan 03, 2020 7:48 pm
It never ends as then the listening and tinkering starts
I know you are right but i want a finished pair of speakers which look and sound good, hopefully before the end of the decade :lol:

I have problems with diy deadlines because there is always something else to try and it niggles away at me :roll:
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 »

Found this which has a few similarities to the design i am playing with. It is a JBL Aquarius 4, which i had never heard of until now. This has a port :shock: and does not have a driver firing upwards in the top enclosure. It is slot loaded where the down firing and up firing drivers meet.

I am not sure my design would be referred to as slot loaded as mine will be open on all four sides rather than just one side. EDIT - the JBL is open on all sides as well :roll: Also i am not sure that there is a driver firing down wards from the top enclosure :roll: My bad. It is described as a loading plug with stuffed trap ????? Looks like a diffuser.

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http://www.audioheritage.org/html/pr ... s.htm
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Got both upper enclosures nearly finished now. Put some bracing in between the two large panels with one strengthening the small strip left between the 5" and tweeter cutout. Used some old hand tool shafts - some nice hardwood. I knew i kept hold of them for a reason :lol:

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Going to dope my two new 5.25" drivers now. Doing it in the shed this time as last time i did some doping i had a headache or two from the fumes.
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 notice the Linn Isobarik had the mid and tweeter mounted the opposite way around to mine. Linn had the tweeter at the back of the top panel where as i have it at the front.

Not sure what difference it will make ???? I could rotate the top panel and try it both ways (if i can be arsed).
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Found a different sealant to use when mounting drivers etc. It's gutter sealant in a tube to be applied by a gun. It doesn't go completely hard and it's black :dance: I don't need it to be an adhesive as i use screws so is just the job. With all the removing of drivers and panels that i do when experimenting it should make things easier. Decorator's caulk is ok but it does adhere things together ( not as bad as silicone sealant though).
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Doc modding Marantz imperial 7

Unread post by Latteman »

I use black silicon sealant for fixing drivers, have used gasket sealant too but that is much more permanent.
The ‘roof’ of my speaker is a very heavy ceramic and granite tile mix that couples to the rest of the speaker with draft excluder so easy access if needed
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 »

Decided to mask off the surround of the new 5" drivers. I remember Doc saying that it did not matter if dope went on the surround but i am paranoid after reading on classic speaker pages that it has an effect on resonant frequency.

Look like little flowers :grin:

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Idecided to give them a couple of coats of plastidip to start with and then have a listen. Some dust caps have melted after being doped with bison kit so i thought it would be wise to put a layer of plastidip between them. Paranoid ? Maybe.

After the plastidip was applied

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Going to have a quick listen tomorrow and then apply some bison kit :dance:
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

I needed to get the 5" drivers and tweeters out of my little semi omni cuboids in preparation for mounting them in the new enclosures. When i mounted them originally i used silicone sealant. The buggers are very hard to get out in one piece. Way back i had to remove one of the 5 inchers to sort a buzz that was caused by one of the lead out wires touching the cone. I remember i had to jack it out with a bottle jack.

So, i went and got the jack :lol:

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There was a disconcerting noise as i jacked it up which was the sealant stretching before letting go. No drivers were damaged in this procedure. I learned a while back not to use silicone for mounting drivers again :roll:

I couldn't jack the tweeters out so found a length of 3x3 wood (longer than the cabinet depth) and arranged it with one end on the concrete floor and the other on the back off the tweeter magnet. Pushed down on the little cab and hey presto the tweeter was free. Turned out a lot easier than getting the 5 inchers out.

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Stay tuned for the next episode :epopc:
DIY inspired by Richard "The Doc" Dunn RIP

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Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Needed some tunes whilst my little cabs are out of operation. So taped this crappy full ranger in that i liberated from a knackered portable cd player.

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Sounds good enough for the time being whilst i get the new enclosure done. It has highlighted one thing though. Point & squirt sucks :lol: :lol: :lol: The volume is quite a bit louder now so this little full ranger must be a bit more efficient than the doped 5 inchers. When i get the new enclosure finished with two 5 inchers in it i will gain some efficiency there :dance:

I just plugged the back of the old cuboid with some foam and put a bit on the top to cover the old cut out for the 5 incher.

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Don't it look glorious :lol: Tomasz will love this one :grin: It's just to see me through til the other cab is done. I am enjoying the distortion . It's not half bad actually.
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 »

Here's a vague mock up of what i am trying to do. I am using the old big bass cube for now until i can build another out of concrete to the same footprint as the new top enclosure (40cm x 40cm). The new bass box won't be a cube anymore as i will need the height to be greater than width or depth to get the required box volume.

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I have it just resting on some bits of cut up fence post that i have used for all sorts of things with this speaker experiment. Bits of cardboard were needed to get the right height.

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I have the magnets of the two drivers touching at the moment. I don't know yet whether they will remain touching. It could possibly be a good idea to have some pressure applied to both drivers to keep them rock steady. Not sure about this or how to achieve it yet. Thinking cap is on :think: :think:

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The idea of having the magnets out on both drivers was to reduce the higher frequencies produced by both drivers as the dust cap is now firing into the respective enclosures. Also i wonder if the cone now being convex rather than concave aids the omni directional dispersion of the sound waves.Not sure on that one, it could all be bollocks.

For the bass enclosure i have to have the magnet facing out to use the clamshell configuration. I don't have to do it with the 5 incher however. The chassis frame is hindering the sound waves however,. Without going and asking a question at diyaudio :roll: it is all speculation (you can't trust everything people tell you anyway). That area between the cabs is going to covered with grille cloth eventually to hide a multitude of sins :lol: :lol: :lol:
DIY inspired by Richard "The Doc" Dunn RIP

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