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A Beovox MS150 Project

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sonavor
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sonavor posted on Fri, Mar 30 2012 5:31 AM

While delaying the completion of the Beomaster 6000 project (I have been recapping some other amplifiers before diving into the volume motor repair), I came across these Beovox MS150 speakers that are in need of restoration. The MS150 speakers have been on my radar for a while now but this was my first chance to get a pair and they were within driving distance (for me) to pick up...so no shipping. 

As you can see, the 8 inch and 10 inch drivers need new foam surrounds. That is to be expected. I haven't opened them up to check the crossovers yet but I am figuring I will be replacing those capacitors as well.  The real issue I will have is the top grill covers. Both speakers are missing those. Even without them I had to buy these speakers. If anyone has any spare top grill covers please let me know. 

I am also trying to decide the best place to order surrounds. I have bought surrounds off Ebay for several of my CX100, CX50, S55, S120.2 and RL140 speakers.  All of those refoam projects came out great. I imagine the same surrounds for the S120.2 8 inch driver should also work for the MS150. I will see if that company also supplies the 10 inch surrounds. 

In any case, parts will have to be ordered so it will be a couple weeks before I can really get started.  


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sonavor
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...with the grill covers (no top cover)


Peter
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Answered (Verified) Peter replied on Fri, Mar 30 2012 9:06 AM
Verified by Jason

When I had a pair of these, I had them reconed with a rubber surround. The sound was excellent - Recone Lab were so impressed they put them through their sound chamber - ruler flat response! They are the pair pictured here.

Peter

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sonavor
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Good suggestions Søren. I examined the driver again and took these photos. The center pole is definately going to determine if this can be fixed. I used a tripod to fix the camera directly over two opposite sides of the voice coil channel and I can now see that the center pole is not exactly centered.  It is centered enough to allow the voice coil to be removed but as the pictures show, the gap is not the same all the way around.  Ideally the center pole part would be pulled and re-aligned into correct center position again (epoxied in place).  I don't know if that is possible.  I will have to make some time to take it to the repair shop and see what they say.


sonavor
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Here is a picture of the 8 inch driver viewed from the bottom. You can see the ring where the center pole in mounted.


Dennis
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Dennis replied on Sat, Apr 14 2012 3:13 PM

@Sonavor: I am sorry to hear about your broken driver, but I hope it will be functional again. Otherwise you will have to look after a donerspeaker. I have a driver from a MC120.2, which is identical to yours, but the Post Service here in Denmark destroyed it a few years ago, and the basket doesn't seem repairable (It went to pieces). 

It’s about 1,5 year ago I chose to upgrade (Or what you would say) from a pair of Beovox MS150 to a pair of Beolab Penta MKIII. Since then I have regretted selling my Beovox MS150’s, which had to go at the time because of space problems. A few days ago I found a pair of Beovox MS150.2 that just were too good to pass. They are almost as new except for a few scratches on top. I don’t think I will be using them daily, but I’ve missed the sound and look of them, and it is nice to could be listening to them once in a while when they have been renovated at some time. I can also see that they have got desirable collector’s items through the past few years, and I’m very glad to own a pair of these beauties again. I will never part with these ones! The Beovox MS150's and Beovox MS150.2 are fantastic speakers, and I hope you also are going to be able to enjoy yours. Smile

 

- Dennis

 

sonavor
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With the stands too, nice.  It looks like you will be getting the woofer surrounds replaced soon. I am getting anxious to hear what the MS150's sound like. Right now my target date is sometime next week (maybe next weekend but hopefully sooner).

sonavor
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Tonight I shimmed and glued down the surround on the good 8 inch driver.  The width of the channel where the voice coil travels measured about 1.5 mm.  The diameter of the center pole is 7.5 cm. I cut two 23 cm long x 6 cm wide strips of my remaining 005 gauge acetate. I fit both strips into the channel.  Then I put smaller 005 gauge acetate strips between the two long strips to make the fit tighter. I could still move the cone but it was pretty snug.  I felt that was a good shim. As I already knew, the width of the channel I had to shim on this driver was quite a bit wider than the 10 inch driver.

The attached picture shows cutting the dust cap and the shims all in place.


sonavor
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Here is the 8 inch driver with the surround glued to the frame.  Tomorrow I will remove the shims and give it a test with my signal generator.


sonavor
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Managed to get the second 10 inch driver shimmed and the surround glued to the frame.  So both the 8 and 10 inch drivers will be ready to test tomorrow. I shimmed this second 10 inch driver a little tighter than the first.  I was able to re-use the long 005 gauge shim from the first one but I used 004 gauge shims for the second layer (instead of 003 gauge).


sonavor
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The 8 inch and 10 inch driver refoams are finished and came out as good as the first 10 inch driver.  I glued the dust caps back on already.  I was trying to decide if I wanted to quickly put the drivers back into the cabinets now and see what they sounded like (which meant I would also have to open one of my S120.2 cabinets to borrow the 8 inch driver)....but decided against it.  The speaker trim pieces still needed cleaning, the crossovers still have to be recapped and I want to clean up the cabinets.

I put the plastic trim pieces in a tub of warm, soapy water and cleaned them up. Next I took one of the cabinets and took out the 8 inch tube with the damping material. While working on the refoam of the 8 inch drivers I realized that I had a black plastic ring (a sleeve) with the driver that really should have stayed with the dampening tube. The tube also had places on each end where the paper was starting to unravel.  I place the plastic driver sleeve into the tube, applied some Aleene's Tacky glue at the edge of the tube and the inside of the tube. For the paper that was unravelling I used the same glue I used for the surrounds.  Here is a picture of the tube with the driver sleeve back in place.


Søren Mexico
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OMG you really run into everything possible with these speakers, its interesting to see what you are doing, waiting to see what happens with the bad driver, I hope it can be saved.

Collecting Vintage B&O is not a hobby, its a lifestyle.

sonavor
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I have the crossover for the cabinet removed and ready to recap. There are a couple of inductors that are not as secure as the should be so I will reapply some tacky glue where the original glue came off.  As I showed in earlier pictures of this project, it looks like someone has worked on the speakers before.  There were some spots I could tell were new glue instead of the original. The back of one of the inductors has a chip in it. That inductor is firmly in place though and appears to have original glue. I wonder how the chip would occur.  The trace side of the board is opposite the back of the tweeter and midrange housing so it is not exposed where it could get hit (if someone was poking around inside).  It would have had to be chipped when someone was working on the board I think.  Here is a picture.


sonavor
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The cabinets seem solid and everything seems intact.  This pair of MS150's just suffered through a long period of storage where they weren't in use.  But I also think they weren't in use because maybe there was a rattle in the cabinet.  Maybe loose inductors on the crossover PCB (judging by the fact several have been re-glued).  I don't think the 8 inch driver can be saved.  The center pole is solid enough where I can't move it by hand but it is loose.  It really needs someone with the right speaker tools to take it apart and reset it.

Søren Mexico
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sonavor:
That inductor is firmly in place though and appears to have original glue

The inductors on my 3707 was glued with a glue a lot darker than yours, 2 coils was loose from transport, I didn't use tacky glue, but silicone and let dry over night.

Collecting Vintage B&O is not a hobby, its a lifestyle.

sonavor
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The wood cabinet is the another task I will have to do.  Here is a picture of the bottom of one of the cabinets.  Both look the same.  You can see the remains of the duct tape that held on a plastic screen.  I am guessing the screen was to keep rats/mice out of the bass port while the speaker cabinet was in storage (surely it wasn't used like that).  My plan is to remove the remaining duct tape residue, tape off the black plastic bass port trim, then lightly sand the bottom of the speaker.  After that I will apply Søren Mexico's refinish treatment and see how it looks.  If I get it to look like his finishes I can proceed with the rest of the cabinet.


Søren Mexico
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Sanding will be very difficult with the bass port in, try Iso alc. on the tape remains, if it don't come of try with acetone, but careful with acetone on the plastic ring.

Collecting Vintage B&O is not a hobby, its a lifestyle.

sonavor
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I plan on taping off the plastic ring...maybe even removing it it if is easy.

On your earlier words Søren: "... you really run into everything possible with these speakers"
That set off an alarm in my head.  I have only concerned myself with the woofers and the crossovers.  What about the midrange and tweeters?  So I just tested the midrange and tweeter drivers.  One midrange is dead.  So out of 2 tweeters, 2 midranges, 2 eight inch woofers and 2 ten inch subwoofers - I have one bad midrange and one bad eight inch woofer to replace. 

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