I have a set of the above speakers. They have not been used a lot
during their lifetime; however, from day one I noticed and complained
that there was intermittent static or flickering being heard from the
speakers.

I have had my AMP (NAD) repaired several times becuause this
seemed to be the source of the problem. Unfortunately, this was not
the
case. I have used different amps and all seem to have the same
problem:
intermittent static and flickering and even "cutting-out". I have been

using Kimber Cable bi-amplable cables.

Any idea what is going on and if it is worthwhile to have them
repaired?

Thanks


--

Sounds like a rubbing voice coil. This could come under warrenty if time
has not expired. Another good guess is that the kimber wire is polluting
the electron flow where end termination causes reflection and energy
cancellation nulls, try exchanging each end for end to get the polarity
right.


--

wrote:
Sounds like a rubbing voice coil. This could come under warrenty if time
has not expired. Another good guess is that the kimber wire is polluting
the electron flow where end termination causes reflection and energy
cancellation nulls, try exchanging each end for end to get the polarity
right.

Unfortunately, my warranty has long expired, unless Mission has a
goodwill warranty that I am not aware of. But, I did complain about
this from the beginning.

I even took the speakers a few years back to an authorized repair
centre and the owner of the shop took an multitester to the connections
and said everything was fine.

Would/could the rubbing voice coil affect both speakers? Would
something like this be expensive to repair?

I am hoping that it indeed could be the Kimber cable since the speaker
wire is the constant.


--

wrote:
Sounds like a rubbing voice coil.

Agreed.

This could come under warrenty if time
has not expired.


Another good guess is that the kimber wire is polluting
the electron flow where end termination causes reflection and energy
cancellation nulls, try exchanging each end for end to get the polarity
right.


You *are* joking, I take it.....
S.


--

Marko wrote:
wrote:
Sounds like a rubbing voice coil. This could come under warrenty if time
has not expired. Another good guess is that the kimber wire is polluting
the electron flow where end termination causes reflection and energy
cancellation nulls, try exchanging each end for end to get the polarity
right.

Unfortunately, my warranty has long expired, unless Mission has a
goodwill warranty that I am not aware of. But, I did complain about
this from the beginning.

I even took the speakers a few years back to an authorized repair
centre and the owner of the shop took an multitester to the connections
and said everything was fine.

This will test only the DC resistance, and check for an open or short
circuit. A rubbing voice coil is a mechanical problem, which will not
change the DC resistance to any appreciable extent.


Would/could the rubbing voice coil affect both speakers? Would
something like this be expensive to repair?

Unlikely, but possible that it could affect both 'speakers. If both
units *are* affected, then both faulty drive units will need changing.
It is usually the bass 'speaker that rubs, tweeters, in my experience,
just stop working, although I did have one once that went low output,
even though still working.

As to cost, new bass units can be anything from £10 to £50 or so each.
Mission's repair department should be able to advise a price and
availablity.



I am hoping that it indeed could be the Kimber cable since the speaker
wire is the constant.

Unlikely, but to satisfy yourself it isn't the cable, just change the
Kimber for anything else, even light flex will do to check that the
distortion goes away.

Fault-finding is generally a logical, step-by-step process, and only
ever change one thing at a time, or you can very easily become confused.
I would check, in order, the bass units,(if the drive cone is rubbing,
you can feel it if you push the bass cone gently). Then the cable (it's
easiest, but the least likely), then change the power amp.



S.


--

Marko wrote:
I have a set of the above speakers. They have not been used a lot
during their lifetime; however, from day one I noticed and complained
that there was intermittent static or flickering being heard from the
speakers.

The case for insisting on return privileges, though that's water under
the bridge for you at this point.

I have had my AMP (NAD) repaired several times becuause this
seemed to be the source of the problem. Unfortunately, this was not
the
case. I have used different amps and all seem to have the same
problem:
intermittent static and flickering and even "cutting-out".

What's really odd here is that this is happening in both channels. It's
possible that there was a manufacturing defect in both woofers, but
even then it's unlikely that the sound would "cut out" in both speakers
simultaneously. Try listening up close, and see if the problem is
predominantly in one speaker or the other.

I have been

using Kimber Cable bi-amplable cables.

Unlikely to be the problem in both channels, but $5 at the hardware
store could eliminate them as a suspect.

Any idea what is going on and if it is worthwhile to have them
repaired?

Not if you're going to take them to the same shop you've been using!

bob


--

Any idea what is going on and if it is worthwhile to have them
repaired?


Before anyone can even have a clue as to what is going on here, you
need to answer a whole bunch of questions, starting with:

1. Does the 'flicker' as you describe it occur on both speakers?
2. Is it equally distributed or does it seem to favor one speaker or
another?
3. Is it irrespective of source or does it seem to favor one source or
another?
4. If it favors one source, which is it?
5. Does it seem to happen at only certain times and/or with certain
types of music?
6. Is it volume-dependent?
7. Briefly describe your listening area, musical preferences, average
volume for listening and _ALL_ the equipment attached to your system.

But if I were to have a gun pointed at my head to make ONE (1) SWAG
(super-wild-ass-guess) at this, I would suggest moving parts and static
being the root-cause. Something like the TT being grounded to the
receiver via the ground-lug (vs. either input shield), and the receiver
itself having a poor internal common ground.... typical of NAD units,
by the way and not repairable in the sense that it is not seen as a
defect.

But try to answer those questions so that we have some valid
information upon which to venture an informed guess.

Excepting thoroughly moused (chewed, damaged, frayed) kimber-wire, it
won't be that. And if it is truly symmetrical, it is unlikely to be the
drivers unless they have been subjected to severe abuse and/or the
surrounds have shrunken or torn pulling the cone to one side or
another. You should have heard either of the above conditions long
before the coils began to rub, however.

Peter Wieck
Wyncote, PA


--

Thanks, now I am totally confused. I have set-aside my speakers and
amp in storage which is a total waste for the last 5 years. I want to
bring them back out of hibernation.

I emailed Mission UK and this is what they wrote me which really makes
me wonder who's been smoking what. Please post your opinons on what
was written to me:

"I'm afraid that too me it is a clear case of the speakers tweeters
being
damaged by the amp. Your amplifier is no way powerful enough for the
753
loudspeakers. These speakers require around 150w per channel to drive
the
efficiently. The tweeters can be repaired with the use of a diaphram
and the
cost of the diaphram is =A327.20 inc carriage for two. I'm afraid that I
am
unable to recommend a repair agent in Canada as our Canadian
distributor
recently went out of business and we are currently looking for a
replacement
company."



wrote:
Any idea what is going on and if it is worthwhile to have them
Before anyone can even have a clue as to what is going on here, you
need to answer a whole bunch of questions, starting with:

1. Does the 'flicker' as you describe it occur on both speakers?
2. Is it equally distributed or does it seem to favor one speaker or
another?
3. Is it irrespective of source or does it seem to favor one source or
another?
4. If it favors one source, which is it?
5. Does it seem to happen at only certain times and/or with certain
types of music?
6. Is it volume-dependent?
7. Briefly describe your listening area, musical preferences, average
volume for listening and _ALL_ the equipment attached to your system.

But if I were to have a gun pointed at my head to make ONE (1) SWAG
(super-wild-ass-guess) at this, I would suggest moving parts and static
being the root-cause. Something like the TT being grounded to the
receiver via the ground-lug (vs. either input shield), and the receiver
itself having a poor internal common ground.... typical of NAD units,
by the way and not repairable in the sense that it is not seen as a
defect.

But try to answer those questions so that we have some valid
information upon which to venture an informed guess.

Excepting thoroughly moused (chewed, damaged, frayed) kimber-wire, it
won't be that. And if it is truly symmetrical, it is unlikely to be the
drivers unless they have been subjected to severe abuse and/or the
surrounds have shrunken or torn pulling the cone to one side or
another. You should have heard either of the above conditions long
before the coils began to rub, however.
=20
Peter Wieck
Wyncote, PA
=20
=20
--


--

Marko wrote:
Thanks, now I am totally confused. I have set-aside my speakers and
amp in storage which is a total waste for the last 5 years. I want to
bring them back out of hibernation.

I emailed Mission UK and this is what they wrote me which really makes
me wonder who's been smoking what. Please post your opinons on what
was written to me:

"I'm afraid that too me it is a clear case of the speakers tweeters
being
damaged by the amp. Your amplifier is no way powerful enough for the
753
loudspeakers. These speakers require around 150w per channel to drive
the
efficiently. The tweeters can be repaired with the use of a diaphram
and the
cost of the diaphram is =A327.20 inc carriage for two. I'm afraid that I
am
unable to recommend a repair agent in Canada as our Canadian
distributor
recently went out of business and we are currently looking for a
replacement
company."

According to the published specs, the recommended amplifier power for
these speakers is 35-150 w/ch. So either the published specs are wrong,
or your correspondent from Mission is full of crap. I'd go for Door
Number 2.

That isn't to say that his diagnosis--damaged tweeters--is necessarily
wrong. But as the responses in this thread should make clear,
diagnosing an audio problem based on someone's verbal description isn't
easy. A reputable manufacturer would suggest a possible diagnosis and
send you to a repair shop for confirmation. I would have thought
Mission was a reputable manufacturer.

bob


--

Marko wrote:
Thanks, now I am totally confused. I have set-aside my speakers and
amp in storage which is a total waste for the last 5 years. I want to
bring them back out of hibernation.

I emailed Mission UK and this is what they wrote me which really makes
me wonder who's been smoking what. Please post your opinons on what
was written to me:

"I'm afraid that too me it is a clear case of the speakers tweeters
being
damaged by the amp. Your amplifier is no way powerful enough for the
753
loudspeakers. These speakers require around 150w per channel to drive
the
efficiently.

This is possible as they describe it under very specific conditions,
more-or-less as follows (and others please add to this thumbnail sketch
if you feel it is unclear):

Underpowered amps damage speakers far more often than over-powered amps
*WHEN* they are driven to clipping. Solid-state amps will send straight
DC into speakers under certain conditions when they clip, and that will
fry voice-coils. If certain conditions obtain, all that DC energy would
also go into the tweeters... and they would go *poof*. I assume that
Mission is sending you a diaphram & coil combination, and that they
assume that the coils are damaged. NOTE: This is another guess.

Would you please try to answer the questions I asked, so as to try to
get to a better diagnosis. It is my opinion that we simply do not have
enough information to diagnose this correctly.

Peter Wieck
Wyncote, PA


--

Oops, sorry for not answering the questions, I thought I did. Here
are they are below:

1=2E Does the 'flicker' as you describe it occur on both speakers?
Yes, it happens in both speakers but NOT at the same time. I switched
the same cables around I still have the problem.

2=2E Is it equally distributed or does it seem to favor one speaker or
another?
It favors the right speaker more so, but swapping speaker wire followed
it to the other speaker ie. seems to be one channel, but I could be
mistaken it was long time ago it was tested

3=2E Is it irrespective of source or does it seem to favor one source or
another? 4. If it favors one source, which is it?
No difference on what the source is. Happens with all.

5=2E Does it seem to happen at only certain times and/or with certain
types of music?
It happens after the amp has been on for a bit, say, 20 minutes.
Sometimes, it doesnt happen for a few hours. It's happened watching
a dvd as well as listening to FM music and CD.
6=2E Is it volume-dependent?
No, but one channel or speaker? seems to have less volume than the
other. I even made mention of this in the repair shop and it was
tweaked and it loooked ok on the scope. At home it wasn't fine. But,
I honestly cant recall since it's not hooked up and it's in storage.

7=2E Briefly describe your listening area, musical preferences, average
volume for listening and _ALL_ the equipment attached to your system.

Amp has been on a coffee table surrounded by a DVD player or CD player,
sometimes plugged into the electrical outlet, sometimes not. Sometimes
the devices are connected to the amp other times they are not. It has
happened in all cases. Volume according to the below link has been
around 7, 8, 9 o'clock position. Music varies from classical, jazz,
pop, classic (Eagles), Pink Floyd to talk.

Here is some new info on the amp from the link:
http://207.228.230.231/info/NAD_7100.pdf

POWER AMP SECTION
Continuous output power into 8=BD * 60W (17dBW)
Rated distortion (THD 20Hz - 20kHz) 0.03%
Clipping power (maximum continuous power per channel) 70W
IHF Dynamic headroom at 8=BD +6dB
IHF dynamic power (maximum short term power per channel) 8=BD 200W
(23dBW)
4=BD 250W (24dBW)
2=BD 330W (25dBW)
Damping factor (ref. 8=BD, 50Hz) 100
Input impedance 10k=BD / 600pFInput sensitivity (for rated power into
8=BD) 850mV
Frequency response 3Hz - 100kHz +0, -3dB
Signal/noise ratio ref. 1W 100dB
ref. rated power 117dB
THD (20Hz - 20kHz) 0.03%

If I missed something let me know.

Just typing out loud heere, Maybe I should get my amp out of storage
and start using it with the current a/v setup to see how it runs but
the cables are completely different. I guess i will have to go out and
buy some new speakerwire to connect to the amp.

Thanks


--

Just typing out loud heere, Maybe I should get my amp out of storage
and start using it with the current a/v setup to see how it runs but
the cables are completely different. I guess i will have to go out and
buy some new speakerwire to connect to the amp.

Nope, nothing missed really. You are not using a TT, nor are you using
an open-reel tape deck, two primary static sources. So that blows up my
initial SWAG.

Confirming a couple of points:

This DOES NOT happen from turn-on with your amp, but only after some
(varying) period of warm-up.

It tends to favor one channel... that is if you swap the speaker leads
**AT THE SPEAKER, NOT AT THE AMP** the chirping follows the leads.

Typically you listen at a substantial or low volume? It is hard to know
what 7,8,9 means. On my AR, Dynaco, Scott, Citation amps, that is very
low volume as the pointer starts at 6:00 on turn-on. On others with the
pointer starting at 12:00, that is quite loud. I am assuming that the
NAD is like most with the pointer starting at/near 6:00, and therefore
relatively low volume. So clipping should not have been a problem given
your taste and source.

If all of this is true, we can pretty-much eliminate the speakers as
the problem. Do you have another amp to test the speakers? That should
be your very first test.

For the record, I am prejudiced. I DO NOT LIKE NAD electronics. When
they work, they sound fine, even pretty good. But they so-seldom work.
They are easy to service, however the circuit design and parts used are
so marginal that repeated failure is nearly always assured. So any
advice I give you to that end will pretty much start off with junking
the NAD, especially if another known-good amp cures the speaker
problems.

So, beg/borrow another decent integrated amp, hook up the speakers and
have-at. To assure a valid test, also attempt to beg/borrow another
source (preferably a CD player or very good tuner), new cables, new
patch-cords, the only original items should be the speakers. All clear?
Then introduce your own source(s). Still all clear? Then introduce your
own patch cords. Still all clear? Then your speaker cables. Still all
clear? Ring in the NAD. If the problem surfaces, junk it. If not, then
it was an ephemeral problem and you have cured it.

Note that each change will require at least several hours of testing.

I gather you are Canadian? If so, when you heat your house in the
winter, the results could be extremely low humidity. Any source of
static within your system could be exaggerated by your environment. A
well-designed amp should not be affected, however.

But, I suspect that the problem will not surface until the NAD
reappears.

Peter Wieck
Wyncote, PA


--