Small Advent Woofer - Repair - Some Measurements

[Pete B]

I have a Small Advent woofer that makes some clank sounds on full
excursion and believe that the VC former is deformed. I want to take
out the cone and need to break the spider glue joint - any suggestions
on a solvent? I should just pick one up on ebay but I want to open it up to see what's
going on, and if it can be fixed, fix it.

I've done repairs like this when I was a kid, and used MEK paint remover,
but is there something better/safer?

Edit: Tried nail polish remover and it was just not going to budge, so I worked on the inner end against
the voice coil and that joint broke with a crack, fairly easily the cone is out. I marked the former with
a sharpie so that I can re-glue it in the same spot, the old glue line is also easy to see.

The woofer must have bottomed badly and the part of the metal former that extends past the windings
bent in making noise against he pole piece. I bent that section back and then up toward the windings so
that if it hits again it will just pack in a bit tighter against the windings.
Did this all the way around the former as shown in this picture after the repair:



Edit: Got the cone and VC out and the former and wind height look exactly the same as the Large
Advent and the metalic, heat conductive former extends well into the big dust cap. The wire
is thicker since it is a 4 ohm woofer. Here are the dimensions:
Wind height: .63" or 15.5 mm this is about 5/8" height of double wound section
Wind height including single layer: .69" or 17.5 mm
VC ID: 1.55" or 39.5mm
VC OD: 1.665" or 42.3mm
Spider glue point to back of wind is 1.08"
VC Former total length is 1.88" or 47.7mm
DC resistance = 3.3 ohms

The VC looks to be 2 layer and about 2 turns are left off the top layer at the top end of the VC
only not the other end. This is a trick to improve motor linearity at high excursion. Picture:


I'm fairly certain that the pole piece is under cut also for better motor linearity.

Moving mass: cone + VC + all of foam, no spider weight = 62 grams
That is very high but it is what's required to get a low Fc in that small box.
All of the foam edge but none of the spider was included so I'm going to call this close enough.

Box volume: 7 x 10.5 x 19" = 1396.5 cu in or .8 cu ft

SA woofer seems to be built on a 10" frame, here a Legacy 10" woofer fits but the recess would
have to be opened up a bit. The Legacy woofer is not 4 ohm and the cone is not heavy enough:



Pete B.

 

[tarior]

Methylene Chloride?
Oh, you wanted safer. Can't think of anything.

If it were in front of me, I would probably just cut it apart, planning upon replacing the coil, spider and surround.

 

[62vauxhall]

I used GC Chemicals Radio-TV Service Solvent to get the VC form off an old Wharfedale woofer. Did not soften the glue immediately but slow and steady won the race.

 

[Doug G.]

It's been awhile but if it's that tannish, orangeish, opaque stuff, I've used lacquer thinner.

Doug

 

[Lo-Fidelity]

I have had some success with acetone.

 

[scoloheros]

I hope you discover a reasonable way to do that. I've wanted to do that a few times to save the cone and maybe even try to fix a voice coil wanting to keep things original.

 

[tarior]

If one doesn't mind destroying the voice coil, saving the cone usually isn't too difficult.

 

[sKiZo]

This should oughta break them cones loose for ya ...

or ...

If you carefully pry the seal away from the basket frame, won't the whole voice coil assembly pull right out?

 

[Pete B]

Edited my first post, the spider glue easily cracked on the inside at the voice coil.
Got it out.

 

[tarior]

IME, a clunk at high excursion (OLA/SAL) is often due to the coil separating from the spider, excessive air leakage from the enclosure, or the suspension itself becoming weak.

 

[Pete B]

Or driving it with 200+ watts with the volume too high.
The spider was glued tight.

 

[tarior]

LOL. That'll do it, too.

 

[tarior]

Those SALs sound so good, it makes you just want more. 199 watts gets 'em sounding great. 200 watts kills them.

 

[Pete B]

LOL, I've done a lot with the Larges, have not listened to working Smalls in 30+ years.

 

[Pete B]

Moving mass: cone + VC + all of foam, no spider weight = 62 grams
That is very high but it is what's required to get a low Fc in that small box.

 

[tarior]

That is a fair bit for a driver of that size.
Did ya' figure what ya' broke yet?

I've seen hard over-excursions knock a loop off the bottom off the coil, or crack/wrinkle the former.

 

[Pete B]

Yes, the part of the VC former that extends toward the back, bent inward and hit
the pole piece.
I bent it outward toward the windings so that the extra fit in the gap, if it bottoms
it will just compress a bit more toward the windings. I've done this before and it
works very well.

 

[Pete B]

I tried an Advent Legacy 10" woofer in the Small Advent woofer cutout expecting
it not to fit but it did fit the hole, the recess was slightly smaller at the round parts
and larger at the "ears" of the pincushion shape. The Small Advent woofer is much
closer to a 10" than and 8". The cone is very slightly smaller in diameter as compared
to the large Advent. The Legacy woofer would never perform like the SA woofer
since it does not have the cone mass, and it is closer to 6 ohms than 4.

 

[tarior]

Not that it has anything prescient to do with the price of tea in China, but I always thought the Advent Legacy was an underrated speaker.

I have a commercial account with MWA. Let me know if you need any parts. I can get them in the next time I order.

 

[Pete B]

Thanks I had an account back in 2005 but didn't order enough to keep it going, I might
take you up on that offer. You're reading my mind, that I'm thinking about modding a
driver to work in place of the SA woofer.
SA woofer is 3.3 RDC and a Legacy 1 woofer that I have here is 5.1R.

A 4 ohm version of the Legacy woofer, with the spitball dust cap grafted on for more
mass might do it. I recently noticed that the Legacy III woofer is dual voice coil, was
that for a bass switch to adjust for placement? Anyone know or have a Legacy III
crossover schematic?

Edit: Pic from ebay 6/8 ohm switch? on the Legacy III, so the windings are probably
different impedance. It would help to know the DCR with them in parallel: