aluminum or copper voice coil?

[sundownz Pro Seller]

Aluminum wiring in houses tends to burn, that's why they switched over sometime in the 70's for safety reasons.

This was due to dis-similar materials on the connectors with varying expansion ratios loosening over time - thus creating heat from the loose connection and eventually fires.

 

[sundownz Pro Seller]

The real factor is the ratio of motor force factor to the MMS and not just MMS... unless you are running a very high frequency where the downward shifting FS will hurt score with the copper.

Example:

Z v.2 Copper ratio is 0.59

Z v.2 Aluminum ratio is 0.62

My testing showed zero SPL difference between the two coils -- in theory the aluminum should have been 0.1 louder based on the ratio but in real life they metered the same... up until over 6kw where copper was a bit louder as power compression was lower.

But on the SA-8 :

Copper : 0.51

Aluminum : 0.54

In this case they are also still very close... but we tested at 68 Hz -- so the much higher FS of the aluminum coil overrode the ratio and gave us a gain of ~0.8 dB or so.

 

[Haunz 10+ year member]

alum cools faster

The thermal conductivity of copper is considerably greater then aluminum... //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

This really isn't rocket science.. with one aluminum and one copper coil of equal mass, wind height, adhesive, former, ect, the copper coil will handle slightly more power.. additionally, because the windings of the copper coil will be considerably smaller you can use a tighter gap for increased BL...

The only reason to use aluminum, as far as I am concearned, is to save money.... (same as with house wiring)

 

[SPLaudio 5,000+ posts]

copper takes longer too cool. you wont have a copper and alum coil the same ww and same weight,lol. tighter gap than copper use alum flatwound. are you mad frenchy?

 

[Haunz 10+ year member]

copper takes longer too cool. you wont have a copper and alum coil the same ww and same weight,lol. tighter gap than copper use alum flatwound. are you mad frenchy?

If you want to compare apples to apples you need to compare two coils with the same mass... period... and to be fair in other terms of performance wind height should also be the same... I can get aluminum & copper round in a wide variety of gauges as well as flat, and edge wound, at any wind height... so there is no reason why a direct comparison shouldn't be made...

As far as copper taking longer to cool, try looking up the thermal conductivity... //content.invisioncic.com/y282845/emoticons/*******.gif.a649d21efc0d1fd4890a6428166586c1.gif

 

[Kyle_Keating 10+ year member]

if both coils are = then the alum will be louder. the copper will handle the power betterfordaily though...

SPLsens is based on BL, Re, Mms and Cone area. The difference between Cu and Al is 3 times the mass but only 2/3rs the Resistance. There is a thermal conductivity difference to in favor of copper, but we'll ignore large signal differences for now.

There is no way to tell is Cu will be more or less sensitive than than AL because the Mms also depends on the rest of the soft-parts. For example, lets say the coil only made up 1% of that mass - In that case copper would out perform aluminum on all fronts. Now lets say it made up 99% of the moving mass - AL would be the clear choice.

 

[CHUCKmfnNORRIS 10+ year member]

are you all still arguing on what metal cools faster?

 

[SPLaudio 5,000+ posts]

nobody is arguing this is the sub section and we can have more indepth conversations.

its better that is x louder than y,lol.

sorry if it bores you guys...

 

[SPLaudio 5,000+ posts]

if there is people more knowledgable than you about something always listen, im always open to being skooled...

 

[CHUCKmfnNORRIS 10+ year member]

yeah i know, i've been reading all the posts and have learned a lot after what i thought was a quick easy answer.

 

[hispls 5,000+ posts]

The thermal conductivity of copper is considerably greater then aluminum... //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

This really isn't rocket science.. with one aluminum and one copper coil of equal mass, wind height, adhesive, former, ect, the copper coil will handle slightly more power.. additionally, because the windings of the copper coil will be considerably smaller you can use a tighter gap for increased BL...

The only reason to use aluminum, as far as I am concearned, is to save money.... (same as with house wiring)

Would there be significant difference in coils of equal mass and height as far as gauge of the coil wire and thermal power handling?

 

[sundownz Pro Seller]

Yes, there would be a difference in mass if the coils were even somewhat similar (if they were of equal mass they wouldn't even be close)... example :

4-layer copper / 63.5mm former / 45mm WW / 7.01 ohm = 0.48mm diameter wire / ~113 grams / 67.74 mm OD

4-layer CCAW / 63.5mm former / 45mm WW / 7.06 ohm = 0.54mm diameter wire / ~40 grams / 68.19 mm OD

If we try to make them of equal mass the CCAW coil would need to be about 97mm long given a DCR close to the above (7.17 in this case).

-----

Using just a sample driver with 110-grams non coil mass -- top plate gap adjusted to be equal from CCAW to the Copper :

COPPER:

Motor Force Factor = 109

Total MMS = 223 grams

Ratio = 0.488

CCAW:

Motor Force Factor = 84

Total MMS = 149 grams

Ratio = 0.563

In this scenario the CCAW would be about 0.5 dB louder assuming FS isn't having a big impact on the score in your setup.

But to examine Kyle's point further about coil mass as a percentage of total mass lets make the non-coil mass 250 grams :

COPPER:

Motor Force Factor = 109

Total MMS = 363 grams

Ratio = 0.300

CCAW:

Motor Force Factor = 84

Total MMS = 289 grams

Ratio = 0.290

Note that the CCAW coil now has a worse ratio.

Moral of the story ? It depends on what you goal is in the design process... copper, aluminum, and CCAW all have their place based on application.

 

[sundownz Pro Seller]

I miss this type of discussion -- we should have them more often.

 

[denim 5,000+ posts]

I miss this type of discussion -- we should have them more often.

Might be the best technical topic here in a while. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[VWBobby 10+ year member]

Indeed. I've only recently been visiting, but there definitely needs to be more discussion like this and a lot less bickering.