Doc modding Marantz imperial 7

A place for DIY project discussions.
User avatar
Firebug1
Posts: 594
Joined: Thu Nov 20, 2014 5:07 am
Has thanked: 181 times
Been thanked: 67 times
Finland

Re: Doc modding Marantz imperial 7

Unread post by Firebug1 »

Looking much, much better than those chipboard boxes. Do you know anyone who does figure painting? Excume my bad english but I cant't find a right term... I hope you understand what I'm trying to say. Anyway, some paint theme, like a robot or football, just might look good on them. You probably get the idea.
These users thanked the author Firebug1 for the post:
karatestu (Sat Nov 06, 2021 12:36 pm)
Rega by Michael Lim\Teac\NVA\
SA Mantra30\Audio Technica ATH-A900X
...the Gods you worship are steel, at the altar of rock 'n' roll you kneel...

Vinyl-ant
Posts: 602
Joined: Sat Jul 01, 2017 12:51 pm
Location: South yorkshire
Has thanked: 0
Been thanked: 182 times
Contact:
Great Britain

Re: Doc modding Marantz imperial 7

Unread post by Vinyl-ant »

Nice job with the cutting stu, plasma cutters are great bits if kit
Id be tempted to sit the tweeter eyeball in a shallow cone, put some rubber blobs onside the cone to decouple the eyeball from the cone and use the cone as a diffuser for the bass driver. and you can then rotate the tweeter eyeball to wherever you want it to sit. And it will stay where you put it. Should then give you a wider dispersion for the bass driver
These users thanked the author Vinyl-ant for the post:
karatestu (Sat Nov 06, 2021 12:53 pm)
I am (barely....) in the hi-fi trade
Status: Manufacturer
Company Name bte designs
Www.bte-designs.weebly.com

User avatar
karatestu
Posts: 5109
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1291 times
Been thanked: 787 times
Great Britain

Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Vinyl-ant wrote: Sat Nov 06, 2021 12:39 pm Nice job with the cutting stu, plasma cutters are great bits if kit
Id be tempted to sit the tweeter eyeball in a shallow cone, put some rubber blobs onside the cone to decouple the eyeball from the cone and use the cone as a diffuser for the bass driver. and you can then rotate the tweeter eyeball to wherever you want it to sit. And it will stay where you put it. Should then give you a wider dispersion for the bass driver
Thanks Ant. It was quite an arse clenching time cutting those holes.

Good idea with the cone pointing down towards the mid bass. I will have a think about it. It would have to be shallow to keel the 2" as close to the mid bass as I can. I can't get within quarter wavelength distance between the two drivers (wavelength at xover of 7kHz is too small) but every little helps.
DIY inspired by Richard "The Doc" Dunn RIP

User avatar
CN211276
Posts: 5437
Joined: Tue Aug 09, 2016 9:29 am
Location: Cardiff
Has thanked: 664 times
Been thanked: 473 times
EUROPEAN_UNION

Re: Doc modding Marantz imperial 7

Unread post by CN211276 »

Black is my preferred colour. Have to admit that most of this thread is over my head.
These users thanked the author CN211276 for the post:
karatestu (Sat Nov 06, 2021 1:02 pm)
Main System
NVA BMU, P90SA/A80s (latest spec), Cube 1s, TIS, TISC(LS7)
Sonore OpticalRendu, Chord Mscaler & Qutest, Sbooster PSs
Network Acoustics Eno, ifi iPurifier3, AQ JB FMJ, Cisco 2940 & 2960
DH Labs ethernet, BNC & USB cables, Farnells cat 8 ethernet cable

Second System
NVA P20, A20, Cubettes, LS3, SSP
Sonore MicroRendu, Topping E30 MCRU PSs, AQ Carbon USB cable & JB

Headphones
Grado SR325e/Chord Mojo, Beyerdynamic Avetho/AQ DF Red & JB FMJ

RIP Doc

User avatar
karatestu
Posts: 5109
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1291 times
Been thanked: 787 times
Great Britain

Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Firebug1 wrote: Sat Nov 06, 2021 12:30 pm Looking much, much better than those chipboard boxes. Do you know anyone who does figure painting? Excume my bad english but I cant't find a right term... I hope you understand what I'm trying to say. Anyway, some paint theme, like a robot or football, just might look good on them. You probably get the idea.
It's not hard to improve on those crap chipboard cubes :grin: They were always a means to an end.

I understand what you mean about getting an artist to paint them. I could let my 7 &11 year old kids do one each :lol:
DIY inspired by Richard "The Doc" Dunn RIP

User avatar
karatestu
Posts: 5109
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1291 times
Been thanked: 787 times
Great Britain

Re: Doc modding Marantz imperial 7

Unread post by karatestu »

CN211276 wrote: Sat Nov 06, 2021 1:00 pm Black is my preferred colour. Have to admit that most of this thread is over my head.
Your opinion is appreciated. Everybody can comment on aesthetics even if the physics is over their head, and I am listening.

:guiness;
These users thanked the author karatestu for the post:
CN211276 (Sat Nov 06, 2021 1:28 pm)
DIY inspired by Richard "The Doc" Dunn RIP

Vinyl-ant
Posts: 602
Joined: Sat Jul 01, 2017 12:51 pm
Location: South yorkshire
Has thanked: 0
Been thanked: 182 times
Contact:
Great Britain

Re: Doc modding Marantz imperial 7

Unread post by Vinyl-ant »

Stu that sb tweeter driver should be capable of crossing over much lower than 7k, i have some sb tweeters that i used in my last metronomes that i crossed over at about 4k, i used an inductor to roll off the top of the 6 inch mid/bass driver because at the top of its response it was ragged as hell and used a cap to bring the tweeter in much lower down than usual. It worked nicely.
Dont tie yourself to a certain cuttoff, and remember that the crossover aint a brick wall. a simple 1st order 6db per octave rollof can be surprisingly useful, and also give a less audibly obvious phase shift imo. Its always a good place to start, crossovers only need be as complicated as they need to be, no more no less.
In terms of complication, less isnt always more, and more is not always more
These users thanked the author Vinyl-ant for the post:
karatestu (Sat Nov 06, 2021 1:52 pm)
I am (barely....) in the hi-fi trade
Status: Manufacturer
Company Name bte designs
Www.bte-designs.weebly.com

User avatar
karatestu
Posts: 5109
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1291 times
Been thanked: 787 times
Great Britain

Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Vinyl-ant wrote: Sat Nov 06, 2021 1:39 pm Stu that sb tweeter driver should be capable of crossing over much lower than 7k, i have some sb tweeters that i used in my last metronomes that i crossed over at about 4k, i used an inductor to roll off the top of the 6 inch mid/bass driver because at the top of its response it was ragged as hell and used a cap to bring the tweeter in much lower down than usual. It worked nicely.
Dont tie yourself to a certain cuttoff, and remember that the crossover aint a brick wall. a simple 1st order 6db per octave rollof can be surprisingly useful, and also give a less audibly obvious phase shift imo. Its always a good place to start, crossovers only need be as complicated as they need to be, no more no less.
In terms of complication, less isnt always more, and more is not always more
All valid points.

In good old Doc style I currently have no filter on the mid bass, I bring in the 2" tweeter with a 1st order passive line level high pass where the mid bass rolls off acoustically.

I have thought of crossing over at 1kHz with a passive line level xover for a number of reasons. The 2" full ranger really is a gem and is highly recommended by many on diyaudio.com. It might improve imaging. There is a dip in the human ear's sensitivity at around 1kHz. Crossing over there will give each driver a fair share of the frequencies- just over 4 octaves each. I can definitely get the two drivers within quarter wavelength distance at ikHz. With the mid bass rolling off at 1kHz it won't be directional like it is at 7kHz. There will be more music coming from the forward firing 2" which might be good.
DIY inspired by Richard "The Doc" Dunn RIP

User avatar
karatestu
Posts: 5109
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1291 times
Been thanked: 787 times
Great Britain

Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Bigger steel hemispheres are available up to 90cm diameter :shock: A 50cm diameter sphere is 62 litres. Big enough for a 12 incher :think:
DIY inspired by Richard "The Doc" Dunn RIP

User avatar
karatestu
Posts: 5109
Joined: Sun Jan 08, 2017 4:40 pm
Location: North Yorkshire
Has thanked: 1291 times
Been thanked: 787 times
Great Britain

Re: Doc modding Marantz imperial 7

Unread post by karatestu »

Right, to progress this any further I need to buy some baltic birch ply and a router.

The ply is to make some driver mounting rings and a spacer which is sandwiched between the two steel hemispheres. Also I might make the single hollow leg and circular base out of birch ply as well. Translam style so the ply's are visible
DIY inspired by Richard "The Doc" Dunn RIP

Post Reply