Popping sound from Acoustats

[pictu...@my-deja.com]

Hi,
I was hoping someone could give me a little help with a small problem I
am having with my pair af Aucoustat Spectra 1400's. One of the panels
has developed a periodic popping noise, as if it is building up static
and discharging it. I took off the grill cloth and tightened the screws
holding the electrostatic elemenent to the frame (they were a little
loose) and the popping stopped for a time. When it came back I found
that by snugging down the screws a little more I could make it go away.
After about a week unfortunately it has returned. I don't want to
tighten the screws any further. What could be causing this?
Any help is greatly appreciated,
Eric

PS: Otherwise I love the speakers!

Sent via Deja.com http://www.deja.com/
Before you buy.

[r_mac...@my-deja.com]

In article <84bekq$l89$1...@nnrp1.deja.com>,
pictu...@my-deja.com wrote:
G'day Eric,

It sounds like you have a bias voltage discharge occuring between
either the diaphragm and a wire stator or to earth.

Are you able to localise the area where the popping comes from? or
better still, if you look inside the panel whilst the room is dark, can
you see the spark that occurs with the pop?

If so, mark the area with a felt tip pen to determine whether the
discharge is to the stator or to earth.

There are a few methods you can use to try to fix the problem without
dismantling the panel.

The problem could be caused by some foreign material between the
diaphragm and stator or frame. Try CAREFULLY vacuuming this area to
remove any dead insects, fluff etc. Use the vacuum on partial suction
setting.

If this doesn't work you can try re-insulating the stator.

The easiest way is to carefully brush a coat or two of conformal
coating onto the PVC insulation of the stator in the area that the
spark (pop) occurs. ( conformal coating is the stuff thats used to
insulate printed circuit boards and comes in cans or aerosols)
Make sure you get it on the face that is adjacent to the diaphragm,
maybe a curved brush would help here. This will seal any flaws in the
original insulation.

The same technique can be used if the discharge is to earth.

Worst case, you can try spraying a light coat of conformal coating into
the area that pops. This will coat the diaphragm with an insulator and
may fix the problem.

The problem can also be caused by a slack diaphragm. If you can
localise the popping you can try supporting the diaphragm with a small
piece of rubber shaped to fit between the wires of the stator. Push it
in until it just touches the diaphragm and then do the same from the
other side so that the diaphragm is sandwiched between them. If this
works leave it be! if it doesn't, at least you can take them out.

One word of warning.

If you use conformal coating or any other solvent based insulator, you
absolutely MUST discharge the panel before using them. Any spark will
ignite the solvents and cause a fire.

Discharge the panel by first unplugging from the mains. Leave for an
hour or two. Then carefully connect the three wires of the panel
together. This will neutralise any charge remaining. The speaker will
then be safe to work on.

Have fun

Rob Mackinlay

[pictu...@my-deja.com]

Hi Rob,
Thanks for the detailed information. I will follow advice and see if I
can localise the ppping. I can definitely hear where it comes from,
although it was in the top of the panel until I tightened those screws
then it moved to the the bottom (about 1/4 of the way up). That went
away for a while after tightening screws in that area but has returned.
The top haas stayed quiet. I will see if I can see it in the dark and
let you know.
Thanks again,
Eric

In article <84bp8b$sl0$1...@nnrp1.deja.com>,

[Lance Dow]

"pictu...@my-deja.com" wrote:

> Thanks for the detailed information. I will follow advice and see if I
> can localise the ppping. I can definitely hear where it comes from,
> although it was in the top of the panel until I tightened those screws
> then it moved to the the bottom (about 1/4 of the way up). That went
> away for a while after tightening screws in that area but has returned.
> The top haas stayed quiet. I will see if I can see it in the dark and
> let you know.

This sounds to me like your diaphragm is loose. Sounds like you have wrinkles,
which move as you tighten different parts of the frame. You may have to resort
to some gentle heat treatment here.

Regards

Lance

[pictu...@my-deja.com]

In article <386A9A58...@ldow.freeserve.co.uk>,
Lance Dow <ell...@ldow.freeserve.co.uk> wrote:

>
> This sounds to me like your diaphragm is loose. Sounds like you have
wrinkles,
> which move as you tighten different parts of the frame. You may have
to resort
> to some gentle heat treatment here.
>

Thanks Lance,
How would I go about that though? With a hair dryer?
Thanks again,
Eric

[D. Middelkoop]

G'day Eric,
You should also consider a static discharge because the high-voltage
power-supply has drifted upwards, and gives a too high output.
Try using the power-supply of the other panel to see if this is the
culprit.
Dick.

In article <84dcl2$vqo$1...@nnrp1.deja.com>,
pictu...@my-deja.com wrote:
> Hi Rob,

> Thanks for the detailed information. I will follow advice and see if I
> can localise the ppping. I can definitely hear where it comes from,
> although it was in the top of the panel until I tightened those screws
> then it moved to the the bottom (about 1/4 of the way up). That went
> away for a while after tightening screws in that area but has
returned.
> The top haas stayed quiet. I will see if I can see it in the dark and
> let you know.

[r_mac...@my-deja.com]

In article <84fs83$len$1...@nnrp1.deja.com>,

pictu...@my-deja.com wrote:
> In article <386A9A58...@ldow.freeserve.co.uk>,
> Lance Dow <ell...@ldow.freeserve.co.uk> wrote:
>
> >
> > This sounds to me like your diaphragm is loose. Sounds like you have
> wrinkles,
> > which move as you tighten different parts of the frame. You may have
> to resort
> > to some gentle heat treatment here.
> >
>
> Thanks Lance,
> How would I go about that though? With a hair dryer?
> Thanks again,
> Eric
>

Hi Eric,

Be careful when trying to shrink back a diaphragm with these speakers.

The high density polystyrene support matrix can easily be softened by
the heat and, as it's coefficient of expansion is quite high, will
probably suffer localised distortion. This could then cause the stator
wires to become closer to the diaphragm in this area and may lead to
another set of problems.

The adhesive that bonds the wires to the matrix may also be adversly
affected by the heat leading to buzzes and rattles caused by loose
wires.

Best regards and happy new year to all.

Rob Mackinlay