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MCM1900 Rebuild


colterphoto1

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Hi gang, yer old buddy Michael C here with more fun projects from Roadie's!

Last time we visited the mighty MCM system, I posted a thread called MWM Rebuild which showed installation of new woofers and door gasket in the double 15" bins. This set was sold but in typical Colter fashion, there's another right behind it. I picked up this set in FL while I worked at Klipsch. You should have seen the look on Hunter's face when the FedX truck unloaded ONE TON of Klipsch gear that day. The KP600 set was on two pallets, four MWM-S on a large pallet, and the MSM and MSSM cabs took up a forth. Marshall GLA51 was a logistical godsend on the FL end of the trip and put me up (and put up with me) for a couple of nights while we readied the shipment.

Since we've covered the bass bins in detail before I'll concentrate on the other cabinets in the series in this thread. Feel free to ask questions.

This particular set is my dream system. The complete 4 way MCM1900 as envisioned by PWK and Associates, this set is the 'Roadie friendly' MWM-S single woofer bins (says so in the literature), and everything but the piezo packs are black fibreglass with complete aluminum trim. Just beautiful. Previously toured in FL and the East Coast by a Rock and Funk band, this sat in a large mini-barn in Sarasota for a decade or so. As an aside the same guy owned both this and KP600. What they toured with was the SW and LF bins of the Kp600 which provided dual 18 and dual 15 in lightweight enclosures, with the Mid bass and high horns of the MCM system. This avoided trucking the large MWM-S bass bins.

So here it is in the truck, awaiting delivery to the FedX terminal in FL, late summer 2007

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crud, had this written and somehow it didn't update the thread...

Here is the pallet of MWM-S-BG at the freight dock. Behind that panel inside the bottom MWM is two MTM tweeter packs, two M4 passive networks, a milk crate of cables, loose K41, and components from a termite-laden KSM2 that got tossed in the dumpster at the last moment.

I wish I kept a better journal but here's the basic outline of the trip.

I flew into Tampa, stayed overnight, hiked a couple miles to the local UHaul and picked up truck.

Drove to Sarasota to fetch speakers. I recall the first song on the truck stereo being 'Highway Star' so I was golden.

Met Rodney, inspected, paid for, and loaded all speakers. Locked truck and left it there at his place. It was the weekend and I had to wait for Monday AM for the FedX freight dock to open.

Marshall (who I'd never even met outside of these Forums) drove all the way from Ockachobee, picked me up and took me back to his place where he would force me to smoke funny cigars, listen to EuroTrash music at the Wall of Voodoo, and hang out at the Sheriff's office.

Over the next couple of days we snagged plywood, pallets, hardware, and straps to build custom sized pallets for transport of these monstrosities.

Monday am- we load up tools and pallets in his truck, Marshall drives me to Sarasota where I get in the rental and we both drive up to Tampa to the freight dock.

HERE'S THE TRICKY PART- we unload ONE TON of Klipsch speakers and stack them on the pallets in the configuration we'd lost a lot of sleep over. Using screw hooks and straps to tie the whole mess together we hand over the load to FedX. Elapsed time- something like 40 minutes. We still had to deliver the rental truck and get me to the airport to hightail it back to Indy. I don't think I've ever sweat so much in my life. We had to pick up every one of those speakers TWICE, and can you imagine stacking those speakers that high while being in a hurry? That MWM stack is over 6' tall!

I have to thank Marshall once again for all his help, without which this trip would have been a nightmare. It was absolutely essential that I have help at this end of the journey and his logistical support was second to none!

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Last summer some time, before Roadie's was built, I replaced the woofers with brand new OEM KP43-E's. Yes I belive in using the real deal, Mr. Paul would have liked it that way. These were the cast frame units so some modification of the frames was necessary. See the previous thread for details on this procedure.

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This set has midbass and high cabinets somewhat different that the earlier set that was sold. In those, the HF driver was a single large Gauss H4000 driver that could only be accessed by taking the cabinet apart.

Three bolts on either side of the cabinet disengaged the steel yoke that supports the throat/driver

Remove jack cup and detach wires from driver

Remove all screws from the mouth flange of the horn

Invert the cabinet onto it's face and lift the cabinet away from the horn/driver combo.

Royal pain, eh?

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Here's the set I'm working on with the more familiar and much more common K4M manifold and 4 (yes four) K55 drivers. In this setup, access is more simply through metal panels on either side of the horn box.

The same type of hatchway treatment was given to the MSSM mid bass module that was originally not part of the MCM1900 design but was quickly added to the series. On the older set, the Gauss 10" driver on the MSSM was accessed by removing two short strips of the aluminum trim and pulling a wood panel out of the bottom of the cabinet. Again- PITA. The new system works much better and the metal cover is supported by a 1/2" plywood reinforcment and the same batting material that you find in old CW cabinets. The newer mid bass driver is a K41, which is an EVM-10L.

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Because these had been in storage for so long, there was actually mud dauber's nests in the throat of the manifold so I had to strip down the HF section to clean that out. Also wanted to test each K55 individually. Looks like these had some work done on them in the past, not surprising given their hard road life. In each MSM, I have two K55V and two K55M. My guess is that as they blew drivers they bought the newer ones at the time, which would have been the M's.

Here's the manifold, beauty of design isn't it?

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Disassembling the K4M from the yoke is a knuckle buster, but I'm learning patience.

Gasket was destroyed but I had a spare from another 2" throat Klipsch project. My test for K55 throat gaskets is bend them in two, if the still flex, great. If they snap, steal some from another speaker and get spares from BEC. He makes em up by the dozens. Always spritz a little WD40 on connectors to get rid of corrosion and make it easier for next time. So here's the parts..

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Testing all K55 drivers, I found that all four of the K55V's are blown. Lucky for me, those are the ones that have spares available from Klipsch. I had a lot of fear about getting into these but once I got going (in the right frame of mind) it wasn't such a big deal. Doing the same thing repetitively helps build confidence and speed.

I apologize for not taking photos but will remedy this in another thread, mmk? Here's the text though.

Remove all screws from the housing and pull out charred, cracked vc and diaphragm. It's an interesting shape, an inverted dome- cool!

The solder lug K55V's had corrosion on the back side of the phase plug which was removed with some ScotchBrite (I just keep green around), and little wipe of WD40 to keep corrosion from returning.

There was some corrosion on the face of the magnet assembly so after covering the opening to the back housing and vc gap with blue tape, I carefully removed it also. You want to keep junk from falling in the gap.

Next step is cleaning the gap. Take blue tape and fold in triangular 'flag' shape and run several corners of this around the gap until it comes out clean. About two flags (6 corners) per gap usually did the trick.

Heat the solder tabs and remove any old leads and solder so you have a clean hold for new leads. Drill out the hole if you can't remove all the solder.

Insert new diaphragm against the phase plug (there are two indexing pins so you can't go wrong. BEING CAREFUL TO ORIENT THE MARKED SIDE OF THE DIAPHRAGM with the positive terminal. I blew this on the first one, had to open it back up (careful) to check and not wanted to resolder, just remarked the terminals.

Carefully insert the top plate/diaphragm down into the magnet taking care not to damage the edge of the vc former.

Solder the small leads to the terminals without overheating. Use a clean hot iron for this.

I ran some music through it to test the vc, using an old AA network for mid frequency output. Kept the music playing to help 'center' the vc as I tightened all the screws.

Voila- done.

The next photo would have been of probably 12 K55's of different types. I'm not going to take them out now.

The wiring is pretty simple once you read it. All the red lines go to the left including the input from the jack cup. The factory installed jumpers in the barrier strip are arranged so that the drivers are run in series/parallel so the impedance is correct. If the wires are soldered to the solder lugs you will have removed the wire from the barrier strip- do not screw the wires back down until you've screwed the drivers on and make sure to put them back in locations so that you have enough wire to get where you're going. Nothing like having to back a couple out to swap them.

And tighten things down nice and snug. These are Pro speakers after all.

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After 8 of those (whew), we move on to the mid bass module. The K41 is no longer available, but my local sound shop can get recone kits for the EVM-10L so I have one out for repair. Here's the condition of one I removed from the MSSM. This is one reason that I alway tear everything down for inspection and cleaning. Yes that's bug poo and parts....[+o(]

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REALLY nasty, eh? I normally use a soft bristle paint brush for cleaning. Not so on this baby. It took a pretty vigorous scrubbing with a short bristle 'fingernail' type brush to get the gunk off but I finally got it cleaned up. This was a working speaker and the recone is $75. I'm poor remember?

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After brushing and wiping with slightly damp cloth, I hit it with SEM vinyl spray coating. This is much lighter and more flexible than any paint and has proven to be a winner for toughening up old cones. Thanks Mr. Paint!

But what is revealed? @#%^& bugs have chewed a couple holes in my cones! WTF??

That's ok, a Roadie tool kit always has a bottle of clear fingernail polish (always carry clear so the other fellas on the crew don't worry about you), and some, umm rice paper, yeah, that's it! [H]

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Cut paper to approx larger than the hole as the paper's probably thin there too. This can also be used for those unsightly screwdriver holes and small tears (not including the obligitory Ritchie Blackmore plunging-headstock-of-Strat-through-Marshall-Stack variety). The manufacturer conveniently put a small adhesive strip there to hold the patch in place while we work. KEWL!

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adhere patch to back side of cone and daub a little fingernail polish over it extending over the edges of the patch.

if you have trouble placing the patch, a Roadie's tool kit usually contains a pair of hemostadt (see 'rice paper') that are helpful tech aids

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