Dampening for mid´s cabitnet chamber, B/W 683 S2

Jan 26, 2019
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#1
I´m modding my 683 S2 speakers by replacing the cap´s and resistors and also rewire internally by soldering directly to the driver´s.

When I uninstalled the midrange kevlar FST, I realized the cabinet housing was packed almost all the way up to the driver magnet with dampening wool, altough it was wool glued to the side wall´s, the back wall and at the down of the housing. The extra wool was just putten in without glue.

For the bass cabinet housing/chamber, there are just wool glued at the wall surface´s, not so much as for the midrange.

Do the midrange chamber really need more dampening than the bass chamber?? Or maybe the assembler just had some extra to get rid of!

I think if removing that extra dampening wool, the midrange sound may be better - or do anyone know if it´s really needed?


/ Mikael
 

Folsom

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Oct 26, 2015
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#2
You could try replacing it with polyfill. The wool might be thick enough to reflect some of the range. I wouldn't want to leave it with nothing, probably sound bad.
 
Jan 26, 2019
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#3
You could try replacing it with polyfill. The wool might be thick enough to reflect some of the range. I wouldn't want to leave it with nothing, probably sound bad.
Thank´s for your reply!

No, I will not leave without any dampening at all, as the back, side and down panels has wool glued to them. The question is if that´s enough, or if the complete chamber should be filled with that folded 70 * 30 cm (27 * 12 inch). Do the midrange chamber really demand more dampening than the bass chamber?
 

RogerD

Active Member
May 23, 2010
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BiggestLittleCity
#5
B&W is a well respected speaker company. They have done the calcs to achieve a satisfactory level of Q in your speaker.
You plan to upgrade the wiring,caps,and resistors seems reasonable....stay with the same values.
I would not fool with the dampening material...leave everything intact. My 2 cents
 

RogerD

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May 23, 2010
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BiggestLittleCity
#7
They're also known for some pretty tailed sound.
Do you think fooling with the Q by the owner will make a large improvement?
 

Folsom

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Oct 26, 2015
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#8
I think that they may have made the midrange sound unqiue with a material that may be a little reflective. Quick sale, but long term pleasure? I dunno. Pretty damn easy to swap back and forth so why give a shit?
 

RogerD

Active Member
May 23, 2010
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BiggestLittleCity
#9
I think that they may have made the midrange sound unqiue with a material that may be a little reflective. Quick sale, but long term pleasure? I dunno. Pretty damn easy to swap back and forth so why give a shit?
You’re right..I should only give a shit about what I can control. Thanks
 

mikaelmark

New Member
Jan 26, 2019
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#10
You´re maybe right, that I should had let the dampening be untouched to not change the parameter´s too much for the speaker!

But when look at the Youbute clip when B/W assembling the 800-series, they use dampeing just at the sides of the midrange chamber, I think.

As it´s possible to overdampening a listening room, then I think it should be also true for a speaker - and I do really not want a "dead" sound from the midrange.

Also, as the midrange driver movement´s are rather small compaired to a woofer driver, I don´t think the midange should need more dampening than the bass woofer.

This week, I has also replaced caps and resistors to a pair of 30 year´s old Techics 3-way speaker´s, and those only had a small dampening cloth hanging with nails inside the cabinet, between the midrange and woofer chamber. So I removed it and replaced it with some wool (from the B/W) and foam rubber at the same amount as I now have in the B/W -speaker´s.
 

Folsom

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Oct 26, 2015
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#11
The sides hardly do anything. A light stuffing is basically always desirable. Polyfill > specific stuff for it.

You can over dampen, but all it takes is a few screws and you can remove some.

The saved money, I'd try a little bit of polyfill.
 

mikaelmark

New Member
Jan 26, 2019
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#12
So you think there will be a need for more dampening filler than just for one sheet glued at each panel all around?

When looking at the assembling of the B/W 800-series, it look´s like they use Poly filler just for the sides, not the complete chamber space:

https://www.youtube.com/watch?v=sel-EoCEeC4 (2:50 into the video)
https://www.youtube.com/watch?v=V6r5SiiZbV8 (4:35 into the video)

The risk of changing the Q-value, I think is mostly for the bass and not the midrange as in my case.

If under or overdampening the enclosure/chamber, how will this affect the sound (at 400Hz – 4kHz region)?
 

Folsom

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Oct 26, 2015
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#13
The second video at 4:35 shows a complete stuffing. They didn't put it at the very front because that's where the driver is at. Just the sides would be literally just a 1" sheet around it.

You know, replacing that wool with polyfill might make it sound like an upgraded speaker... which they would charge you for! They Big 800's use polyfill, not wool...

One way to find out...

Damping, over possible reflections from wool would mean a cleaner midrange. I don't think the Q value is going to move a lot, since it already was stuffed.
 

mikaelmark

New Member
Jan 26, 2019
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#15
I ended up with standard white fabrication at all panels, except the front panel. Then I used a 10 inch x 10 inch (25cm x 25 cm) black dampening at about 15 grams, purchased from a car audio store - that I folded and packed lightly and filled about half the chamber. And at the bracing, I glued a piece of foam rubber.

https://www.mds.se/fibrex-hds.html

Some people also say sheep wool should be the best.
 

mikaelmark

New Member
Jan 26, 2019
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#16
I´m not quite sure Polyfill is the best damping, as sheep wool should be the very best. So yesterday, I went to a nearby farm and bough about 100 grams of genuine sheep wool from sheep derive from a small island here in Sweden. And today I packed the midrange chamber fifty fifty with sheep wool folded in synthetic dampening like a mexican wrap at a total weight of about 90% of the factory default´s Polyfill(?) synthetic, which I now only leave glued at the panels.
 

Folsom

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Oct 26, 2015
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#17
And the result?

Some things may dampen better, but may also cause reflections. There may be some trial and error.
 
Jan 26, 2019
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#18
As I also replaced all the cap´s, resistors and internal wiring, that are still burning in. They have played about 20 hours now and think still under transformation.

However, the sound are sooo nice and it seem´s much better than without the extra dampening. Thank you som much for you´re recommendation about using more dampening, Folsom!

I just hope there were no moth or other vermin in the sheep wool!
 

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