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Martin Audio RS802 & W-Bins - restoration project.

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audiofun View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote audiofun Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2014 at 10:20pm
Thanks for your input guys. It is all very helpfull :)

The refurb is in progres:


Regarding the faulty crossover network: I tried to find out what part is faulty by simply omitting piece by piece of the circuit elements and it turned out that one of the capacitors makes too much HF attenuation, this is the one:


The stuff is 27 years old... Is it possible to get such capacitor nowadays?

ps. Robbo, the plastic corners are gone ;)
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Post Options Post Options   Thanks (1) Thanks(1)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2014 at 10:24pm
oh yes, Wilmslow audio should be able to sell you one exactly like that, probably from the same manufacturer.

RS / CPC are also worth checking, but it is a popular hifi brand for capacitors.

probably about £2.
“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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Post Options Post Options   Thanks (1) Thanks(1)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2014 at 10:33pm
They are usually sold under the  brand name "Solen", for use in high spec hi-fi systems etc. Use either a 250 or (better) 400V DC rated type. If you can't get a 6 uF, make up the value from a couple of others in parallel.

Good to know it wasn't the soldering, I probably built that crossover...


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Post Options Post Options   Thanks (0) Thanks(0)   Quote audiofun Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2014 at 8:03am
Thanks for all the help.

A new issue came out: one of the 12" mids has a very slight cone rubbing. It doesn't sound like the wired side rub, it sounds like rubbing of the internal part of the coil. After a very close inspection I spotted that the outer suspension is slightly lower on one side. It looks like the whole membrane decresed under its own weight after being stored for years. I assume that caused a little coil shift in the gap - hence rubbing. When the speker is feeded with 200Hz of sine wave, the rubbing becomes audible. But even an ultra gentle push of the cone (from the opposite side to the lowered suspension) solves the rubbing problem.

Is it possible the gap is so small to allow for the above to happen?
If I install the speaker upside-down to the way it was fitted originally, is there a chance the cone will move back to its original position after a while?

Cheers,Tom


Edited by audiofun - 02 May 2014 at 8:05am
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Post Options Post Options   Thanks (1) Thanks(1)   Quote TONY.A.S.S. Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2014 at 8:16am
Just one other small thing here, the 6mf is not a standard one you'll find on the shelf. The nearest you'll get is 6.8mf, and in the overall scheme of things it won't make any difference, none that you would hear anyway.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Nitz V1505 Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2014 at 8:38am
Lovely cabs at a Brucey bargain price,well done.
Does the horn extender cover the whole cab or just the mid?
Would make sense if they cover the whole cab.

LET THE BASS ROLL LIKE THUNDER
& THE TOPS LIKE LIGHTNING.....
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Robbo Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2014 at 9:17am
ATC drivers have one of the most narrow voice coil gaps in the industry and because of this, they have always been prone to rubbing.
When you bolt the drivers back into the cabinets, it is worth turning the drivers around like you have suggested but it can also be cured by varying the tightness of the mounting bolts so that the chassis can be very slightly flexed to move the voice coil former away from the rubbing spot---obviously this has to be done with great care on a trial and error basis especially on the drivers that you have as the plastic sealing inserts prevent you from moving the cone manually to check for rub when the driver is mounted on its baffleboard.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Peter Jan Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2014 at 9:48am
Originally posted by Robbo Robbo wrote:

ATC drivers have one of the most narrow voice coil gaps in the industry and because of this, they have always been prone to rubbing.
When you bolt the drivers back into the cabinets, it is worth turning the drivers around like you have suggested but it can also be cured by varying the tightness of the mounting bolts so that the chassis can be very slightly flexed to move the voice coil former away from the rubbing spot---obviously this has to be done with great care on a trial and error basis especially on the drivers that you have as the plastic sealing inserts prevent you from moving the cone manually to check for rub when the driver is mounted on its baffleboard.

I usually put a ~5 Hz sinewave on the speaker, with just enough power to move the cone back and forth a few mm. So you can hear what's going on while tightening.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote jbl_man Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2014 at 11:00am
Of course,it has been known to put a 2p coin under one side of the frame when bolting them in the cabinets.......   Wink
Be seeing you.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2014 at 1:04pm
Originally posted by Peter Jan Peter Jan wrote:

Originally posted by Robbo Robbo wrote:

ATC drivers have one of the most narrow voice coil gaps in the industry and because of this, they have always been prone to rubbing.
When you bolt the drivers back into the cabinets, it is worth turning the drivers around like you have suggested but it can also be cured by varying the tightness of the mounting bolts so that the chassis can be very slightly flexed to move the voice coil former away from the rubbing spot---obviously this has to be done with great care on a trial and error basis especially on the drivers that you have as the plastic sealing inserts prevent you from moving the cone manually to check for rub when the driver is mounted on its baffleboard.

I usually put a ~5 Hz sinewave on the speaker, with just enough power to move the cone back and forth a few mm. So you can hear what's going on while tightening.

Both of the above are very good advice.

A slightly warped baffle board can cause this problem by putting a small twist in the cast chassis when the bolts are all tightened.

In any case, the bolts should be tightened up evenly in a criss-cross pattern, like when fitting a head to a car engine.

Tightening up the bolts whilst listening to a sinewave is similar to the advice given by JBL when refitting compression driver diaphragms (in their case 300 Hz or so)



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Post Options Post Options   Thanks (0) Thanks(0)   Quote audiofun Quote  Post ReplyReply Direct Link To This Post Posted: 26 August 2014 at 1:47pm
Hi all,
if anyone is interested in this refurb project, here;s a little update: the faulty cap has been replaced. The original was 6uF, the closest I've found was 6.8uF. As someone here suggested, there is no difference in performance, so far so good... the 802s sound super-sweet :)

You have suggested to use the tops with G-subs. The rs802s need to be crossed over @ 200Hz or even better a bit higher. I'm wondering about how the g-sub performs in the mid bass region? Anoher thing: the 2x18" design is simply too heavy and too big for me. What's more, g-sub wont give  enough height to stack mid-hi directly on it :/

My idea is to use the tops in stereo stacks, per side: 2x single 18" + 1x hd15 and the 802 on top of it. That would make a nice looking stack (same width of all the boxes and appropriate height for the mid-hi). In theory should also nicely cover the entire spectrum of human hearing.... But:

1. Would a singe hd15 work well as a kick? (Rog recommendation is to use them in multiples).
2. Do I really need to use the g-sub? Perhaps I could use other hi-power BR sub? Regarding the width of the stack I would prefer this project: http://h-audio.de/lautsprecherdaten/eighteensound/kits/18Sound_kit18.pdf

Any advise will be greatly appreciated.

Cheers,
Tom

EDIT: the plan is to use the speaker mainly for dance music (deep house, tech-house, etc). Occasionally bands. But I wouldn't use the speakers for heavy rock or any hardcore / distorted beats ;)


Edited by audiofun - 26 August 2014 at 1:59pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Robbo Quote  Post ReplyReply Direct Link To This Post Posted: 26 August 2014 at 3:01pm
Hi Tom--Nice to see that you are sorting them out---Have a look at the F1B cabinet spec on the Martin website and if you like the look of them then they would be ideal to go under your RS802 boxes---Then your next move would be to talk nicely to Jimmer on here as he had a mint pair of F1B boxes for sale with virtually brand new RCF drivers inside---If you can grab these off him then I don't think that anyone would complain if you copied them to build another pair of identical boxes in order to give you two 18" horn loaded per side and also just about the right height to stack your RS802 boxes on top--This would give you all the depth of bass and also great kick into the bargain and would be much better and simpler than going down the HD15 route and you could also run this system 3 way active instead of having to go 4 way active if you used the HD15 idea.I would definitely run your RS802 boxes two way active, just leave the passive Xover connected to give the JBL HF drivers some protection---Cheers--John.
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