Avance Concrete 180 Restoration

Got myself some "new" speakers, for almost nothing :D

I think thay are oldies but goodies, with a enclosure made of concretefiber, and equiped with a ScanSpeak 3/4 inch tweeter, a Vifa M21WO ... woofer and a passive radiator also Vifa M21 ....

They are from back in the late 70'es and was considered as very good speakers of the time.

There is sound in both, but they need at least new surrond for all woofers.
They also need a new coat of paint and new fabric for the grill.

The filter looks really good, with 4 big Rifa foil caps and ok looking coils. Only a single 10uF alu cap will need changing ... might change the terminals as well, but don't really have to.

Now first things first, restoration of the woofers:

Have looked at both Alles over (zelfbouw) Hifi - Audio and Alles om uw luidsprekers te repareren, foamranden, rubber randen, diafragma's enzovoorts. Does anyone have experience with these companies?
Speaker Repair Shop seems to be almost half price .... so tempted to order ned surrounds there.
Next question is rubber of foam?
Originally made with foam, so that will of course work. Rubber will last somewhat longer, but might add a bit of moving mass, and change compliance a bit .... not sure what effect it will have on Rms.
Any experience here?

The membranes looks ok, but I'm considering whether I should give them a thin layer of new coating. If so what coat should I use?
Have some polyester which will give a pretty hard layer. This might change the breakup a bit, and might have to be corrected in the filter.
This will also add a bit og mass.
On the orher hand, the added mass will also give a lover fs, and might give a few Hz at the low end. It will also lower the sensivity a little, which is not a problem as they seem really sensitive as speakers go today ... and today enough amplifier power is not a problem as it was in the 70'es.
Could also add an extra magnet to the active woofers.

Any thoughts??

Looking forward to getting these beauties up to date again ;)

Kind regards Baldin
 

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Will go for the Foam. Ready to order now, and have found the right type.

Removed the old foam today. Really sticky stuff.
A small sharp wood chisel proved most efficient to remove the stuff.
Used alcohol to clean the last stuff off.

Some came on the membrane an was a bit hard to get off.

I'll give them a thin layer of black spray paint to make them look good before putting the new foam on.

Stay tuned :))
 

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Refoaming

All 4 woofers have now been refoamed.
I used AudioFriends.nl, which can be recommended.

It was actually not that difficult. I was a bit afraid that it would be hard to center the drivers in the magnet gap, so that the voice coil will not scratch. But I just started gluing the surround to the membrane, let that dry and then glued the outer rim of the surround to the basket and just made sure that everything looked symmetrical. I think that most of the centering is done by the spider anyway.

Before I refoamed them I gave the membrane a very thin layer of black spray paint. Think the result looks really good.

I changed the 10 uF electrolytic in the filter with 3 x 3.3 uF MKT, and re wired everything with 2.5 mm2 cable.

The box is really stiff as it is made of fiber concrete, but it also has a tendency to ring when knocking on it. I therefore use some damping rubber used for cars glued to the inside. Think it has helped some, but it is not a miracle cure. I used “No More Nails” to glue it to the inside. Great working stuff, that sets immediately, but a bit expensive also.

Now I’m looking forward to put it all together and put them up for a listening test :D
 

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Restoration almost done

Almost done. Think they look really good :)
Only thing missing is new fabric on the grill.

But how does this speaker sound?

Well I was afraid that they didn't have enough low bass, but that is not the case at all.
The sound is rich and without sharp edges. They sound relaxed but with ok resolution and room. Not bad at all for a speaker more than 25 years old :)
 

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Ok I found out today, that I had my subs on yesterday when I tested the Avance speakers ..... well with a little help from 2 x 12" JBL's in 120 l vented can make any speaker sound rich and bass strong ;) ... so with the subs off, they still sound really good, but somewhat lean and will probably need a little bass boost, but with a 8" and a passive 8" in each speaker, they will be able to handle it.
... still it has been worth the money and effort bringing these speakers back to life.

A small comment on the concrete box ... now sitting next to my normal main speakers made in MDF, and doing the knocking test, the concrete box is much more enert, and the MDF has a much more distinct sound .... guess it did help to put the rubber on the inside, and I will say concrete is a fine material for a speaker :)