I rescued a pair of Beovox M70s (without grills or stands) from a very nice guy who insisted on demonstrating them for me by playing the tuner section of an Altec Lansing receiver from "back in the day."  Who knew Altec Lansing once made home receivers?

Anyway, wouldn't have been a problem, except the otherwise very nice guy was driving the Altec Lansing well into the clipping stage of its amplifier stage.  A loud "bang" would come from the right channel every 30 to 60 seconds!  I was afraid for the poor little guys.

Here's what fifty bucks (!) will buy you in the depressed economy of Central Florida.

The front and the back of the cabinet are a very rigid plastic (seems the same as what I ran into with my S40 refurb project), and the sides, top and bottom are best described as "rough wood vinyl that is restorable."

I listened to a bit of music with them back at the house on the floor of my garage without any care to placement.  They sounded musical and ready to rock.  After verifying all the drivers were working (or rather, seemed to be working), I took them inside the house to open them up.

The best news so far:  rubber surrounds!

Rubber surrounds part 2!

The woofer cone seems a plastic of some sort, the same feel as Infinity woofers from the 80s.  Didn't seem like the polypropylene Vifa woofers I worked with a little in the 80s and 90s.

This phase link is a paper cone with rubber surround.

The infamous, gigantic dome midrange.

I am looking forward to taking a look under the hood of this tweeter. 

What's the story with this grill?  Is it aesthetic?  For dispersion?  Just to protect what's behind it?

If you're after the crossover, don't go through the woofer! 

The back of an M70 comes off by removing 8 screws in the back.

With the damping material removed, you can see a wooden brace, phase link subenclosure (which also serves as a brace since it butts up against the back of the cabinet), and the crossover network.

A closeup of the crossover network.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10 capacitors!

Here's the other crossover.  You can see they're different.

The serial numbers of the two speakers are quite different as well.  Both speakers have a label that says, "HT M70 Type 6304."  But the one from above has the serial number 174020.  The one whose crossover is pictured below has the serial number 1227022.

The only history I have for these speakers is that the nice guy I rescued them from never really used them, and he got them "from some guy out in the country."

To my eye, the wood vinyls of the two speakers are subtly different.  This difference did not show up in any of the pictures I took, though.

First up for these speakers will be some more listening - hooked up to the BM 2400 I think!  New caps are already ordered, and I think I'll try refinishing the cabinets for the first time.

I am not looking forward to rebuilding these crossovers, but I'm guessing it's got to be done.

Nice project !

The woofer was changed in production from s/n 1442001 and the tweeter can be one of two types.
The crossover is seen in several different versions accordingly, the capacitor kit you ordered, covers this.
One crossover seems to have been repaired (a couple of new caps) but otherwise they look identical.

You really should glue the magnet to the metal basket on the filler unit. It has a tendency to work lose,
especially in transport, and then the center piece and magnet will snap to one side, sandwiching the coil
and blocking the cone.
A bit of 2-comp. epoxy on the magnet edge where it meets with the metal chassis will help keep it alive.

Same problem is seen in the Beovox P45 speakers, where the woofers are of the same build as
the M70 filler (though not with identical specs).

Martin

Dillen:

Nice project !

The woofer was changed in production from s/n 1442001 and the tweeter can be one of two types.

Wondered why they diferent from a pair I refoamed a  few years back. Had two pairs. One got refoamed and the other stripped for parts. Still got the tweeters and one of the large dome midrange units. Think the midrange were made by ITT iirc.

Craig

Dillen:

One crossover seems to have been repaired (a couple of new caps) but otherwise they look identical.

The second posted crossover photo would be "original" then?

I figured the first one had been messed with based on the woofer lead being spliced into the main lead. 

Why fix something if you aren't going to do it right?

Dillen:

You really should glue the magnet to the metal basket on the filler unit. It has a tendency to work lose,
especially in transport, and then the center piece and magnet will snap to one side, sandwiching the coil
and blocking the cone.
A bit of 2-comp. epoxy on the magnet edge where it meets with the metal chassis will help keep it alive.

To turn an American phrase upside down:  is it easier done than said?

Wait a minute, maybe I get it:  do I need to just remove the driver and put a bead of epoxy all the way around where they mate, as though I were caulking a bathtub?

I didn't notice the spliced leads and I don't have a crossover here to compare with at present but aren't the
woofer leads going the same place electrically on both crossovers ?
Looks as if the lead was spliced simply because it was otherwise too short, I'm sure
you can see it better than I.

Yes, much easier done than said and bathtub caulking sounds about right.

Martin

Well, I had to take a break from all things B&O for awhile because I got a full-time job.  Coupled with full-time grad school and a family, I just had no spare time so I put the M70s away for awhile and stopped posting to the site.

Winning second prize in last month's draw got the itch going again, I must say.  So I'm finished with grad school in a bit over a month, so I figured, what the heck, let's get those M70s back out.  Who cares if we don't have time.  We will sleep after school is over and let the hobby (obsession) back in!

There is ample evidence these M70s are not a "matched pair."  Just look at them.  Exhibit B.  (Exhibit A is above, serial numbers not even close to each other).

The crossover mounts are different.  One speaker has the wood strip attached by a groove in the side, and the other is attached to a block that is in turn attached to the side.

The rest of Exhibit C.

Both boxes have seen better days.  The sides weren't so bad, but most of the corners had taken a blow, and both tops were very scratched.  Since the pair doesn't look like a pair, I decided this set would be my first foray into refinishing.

I bought an orbital sander yesterday and some tinted (red oak) wood filler.  I touched them up a bit with the filler and hit them with some 60 grit with the orbital sander.

Before:

After hitting the speakers with the 60 grit, I hit them with some 220 grit by hand.  Bummer that in order to get the scratches completely out, I ended up sanding off all the veneer at the corners. 

For the finish, of course the local DIY store didn't have "Rosewood," so I went with a "Red Mahogany."  I was pretty sure it would be darker than original (I'd used "Red Mahogany" before [on mahogany]), but that might be OK so as to hide remaining blemishes.

The product I used was "Minwax Wood Finish Red Mahogany."

After sanding, before wood finish:

And now the cabinets sit in the garage drying.

Meanwhile, I've bought all new Solen capacitors (9 per box!) and new resistors (10 per box!).  I've salvaged the 4 inductors from each box and will reuse them. 

Of course I took the drivers out before refinishing the cabinets.  I'm going to check part numbers on the drivers and make sure they are the same across both sides.  Then I'm going to perform the epoxy surgery on the phase link as per Martin's direction above.

At least one of the drivers also needs work on the connection (a woofer - a little hot glue should fix it I think).  By the way, above I wrote the woofers are some plastic - I must've been on crack that day because they're paper.

I'm still trying to decide how to actually put the crossovers together.  Using Solens (huge) creates a real estate problem.  Below is a bread board showing all the parts.  I put this together to test different brands of capacitors before I settled on Solens.

Wow Rich, what a project!! Very cool.

Keep it up!

This was the worst corner before the attempted refinish - on a top no less.

This is the same worst corner after the attempted refinish.

Fixed worst corner doesn't look too bad, huh?  Unfortunately, the main goal of making two matching speakers did not work.  Looks like the one on the right needs an entire second coat, and the one on the right just needs a bit of spotty touch-up.  I'll do that at the very end of this project.

Meanwhile, I think I've figured out what I'm going to do about the crossover network, but I'm not going to spoil the surprise.  I invested in a 2.75" hole drill for putting my favorite terminal cups into my Beovox restores.  Cut a beautiful hole.