corroding voice coils

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Today I had a very interesting conversation with Lowthers. One question I asked was:What is the difference between silver voice coils and aluminium ones? They said that the silver coils give a smoother response than the aluminium coils, but that the aluminium coils have more "attack". This difference I put down to the fact that silver, being heavier than aluminium, would be more sluggish than aluminium.

Their second point though, really did give me something to think about: They said that aluminium coils need to be in regular use, otherwise they corrode.

Is there anything to this? I really don't think that Lowther is pushing silver coils, because the price difference is not that great.
Does anyone have any experience of aluminium voice coils corroding in drivers that have been idle for a sometime?


Cilla
 
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Hi Cilla,

Interesting. I wonder if they were referring to the bobbins? The reason I'm asking is that the coil wire, as you know, is coated and has very little ability to corrode.

Mind you, I've not heard of a silver bobbin so who knows what they were referring to. Doesn't make a lot of sense to me.

I'm wondering if we should change the title of the thread to corroding instead of corrosive? Wat u tink?
 
Voice Coil Corrosion

Hello Cilla:

In the decade that I have been involved with Lowthers I have never seen a corroded voice coil. They are built from enameled wire, and then have a varnish coating over them.

Once a customer complained that his voice coils were corroded, but that turned out to be nothing but the Hi-Ferric coating applied to them.
 
Hello Jon,

Is the ferric compound applied to aluminium voice coil prior to any coating? If so, would an electro-chemical reaction take place between the ferrous oxides and aluminium if, as is likely, oxygen is trapped - creating aluminium oxide?

I'm mystified by Lowthers comment; they don't seem to have anything to gain by it.


Cilla
 
Hi Cilla:

Based on second hand information, this is my understanding of how it works.

Wire comes in enameled, and they wind it into the voice coil. It is then attached to the voice coil with varnish. Hi-Ferric material is then brushed by hand onto the voice coil. The voice coil is then baked to make sure the Hi-Ferric is cured properly and will adhere to the the voice coil.

Not sure how any moisture could withstand the baking process, and if it did how it would penetrate the varnish and the enamel. Basically, I would not worry about this happening.

That being said, I like the sound of the silver better.
 
Voice Coil corrosion - again

Hi Cilla:

That area theoretically may corrode depending on the solder used. Use of aluminum wire and copper wire, combined with the contents of the solder may result in a galvanic reaction. (hee hee, I still remember that stuff) . Again, never an issue with any drivers I have ever seen.

There is no reason why using the drivers would somehow prevent corrosion from occurring here, so that part does not make sense. Wonder why they believe this?
 
I Have had this very issue with my driver, i have an early pair of ex4's and just one connection came apart about 3 years ago

i carefully resoldered it and stuck it down with pva

my veiw is that the heaver copper connecting wire was not stuck to the cone correctly allowing a little movement, as it came off very easily .. and there was a clean break...
9 months ago the other side went so i did the same with that

i will trade the driver if it happens again..

my speakers have been in regular use since they where bought.

regardless of possible quality issue i would not be without them


going slightly off track...

the main complaints about lowthers is that they can sound too forwards.. and my experience is that using a BLH for bass,
it has to be big enough to produce enough bass, otherwise the sound is not balanced..

i used mine in a BLH for 6 years until i converted to OB this year
using a couple of goodmans 12" ( 61 & 301) for support

i think the sound is much more balanced now.. with much more detail in the bass and a more natural sound..

.. and with 3 drivers a side i get more volume than in the BLH

steve
 
steve shiels said:

the main complaints about lowthers is that they can sound too forwards.. and my experience is that using a BLH for bass,
it has to be big enough to produce enough bass, otherwise the sound is not balanced..



Exaxtly! Most Lowther implementations sound shouty because noting is done to correct for the rising FR of the drivers. I use a contour filter in my Lowther based MLTL's to accomplish this and I routinely get comments about how smooth and balanced the sound is. I guess that people expect Lowther speakers to be shouty and are amazed that it doesn't have to be.

Bob
 
Jon.

"I wonder why they believe this?".........:scratch:

The solder they use certainly isn't ordinary: Nothing ever is with Lowther. I suppose its part of their allure and attraction.


Steve,

If that happened to me I would have sent them back!

As to the balance problems you experienced with your BLH, I'm having the reverse problem. At present I can only achieve a nice balance if I use a duvet suitably stuffed into the mouth. Thats one reason why I'm why I'm exchanging the EX3 for the EX4.



Cilla
 
Bob Brines said:



Exaxtly! Most Lowther implementations sound shouty because noting is done to correct for the rising FR of the drivers. I use a contour filter in my Lowther based MLTL's to accomplish this and I routinely get comments about how smooth and balanced the sound is. I guess that people expect Lowther speakers to be shouty and are amazed that it doesn't have to be.

Bob

Bob That one way of doing it, i did it by proping up the lower mids and the bass
after no crossover in the horns.. i was not happy at all about the effect to the sound of a simple cross over with the baffles, it was not untill i removed it and looked at using the baffle to roll off/ boost where i thought and then found some complementary supporting drivers that i'm happy...
they are now i my view, much more of a balanced sound than i had...
my lowthers have been played alongside many others including aer and fostex, some of the fostex drivers sound rougher and more peaky..

amp matching is critical, I use home made SE DHT 's
and am very happy now with OB's.. more than i was with horns..
i think horns can be made to do uncoloured bass.. but when made out of wood ?? mmm

pdan said:
Jon.

"I wonder why they believe this?".........:scratch:

The solder they use certainly isn't ordinary: Nothing ever is with Lowther. I suppose its part of their allure and attraction.


Steve,

If that happened to me I would have sent them back!

As to the balance problems you experienced with your BLH, I'm having the reverse problem. At present I can only achieve a nice balance if I use a duvet suitably stuffed into the mouth. Thats one reason why I'm why I'm exchanging the EX3 for the EX4.



Cilla

I tried to send them back but i'd had them for 4 years... they would not have it at all...

you will not be disapointed with the ex4, i exchanged dx3 for ex4 in 2001

i had just built my 3rd pair of horns 3.6m 38 hz tratrix horn with quite a large mouth ..22" x 36"..

the dx3 where lost.. the top end went and they sounded too off balance..

the ex4 transformed them.... but i was worried that the extra money would be wasted.. until they started playing..

i was happy for about 3 years until i started to notice the colour in the bass, i realised all the cabinets i had heard where the same to some degree..amorphous cored outputs helped ...
but last years after an afternoon of OB's ( fostex/eminence) vs my horns a/b'd.. the the difference in the bass became apparent

been a baffle convert ever since i got them to sound ok with the lowthers drivers.. the goodmans are up with the lowthers, and sound very good together, very fast tight and detailed bass, and lower mids support the lowther mids and top end.. good enough for me anyway..
the big eminence bass drivers in comparison are slower and less detailed as bass helpers..
like a dynamic and lifelike sound... and i've very happy

I have run some of the Hi fi world forum meets over the last few years so there have been lots of kit to compare with...

my horns are on the gallery there

steve
 
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