Heatsinks for DIY LED lamps

[organic-fanatic]

@SupraSPL ...Did you ever digest this data ?
I was all set to go with 4.9 for passive untill iread this post, the 4.9 @ 7 inch with a thicker base should have advantage over the 5.88 @ 6 inch on paper.
Can you test your 4.9 with no air movement to compare with the 5.88 data without air.?
Also the 10.08 profile with cobs mounted close to the edge is very interesting, what does this data tell us ?
Could it be that since they are so close to the edge that the heat escapes that much faster ? And all that extra metal is unnecessary?
Can you take a measurements of the 10.08 opposite of the cob on the heatsink and move outwards from the center maybe every 1/4 inch or fin toward the center of the heatsink, to find out the point of diminishing return if there is one.
If this theory is proved, for example the 10.08 with its thicker base, could be bought at maybe 4inchs the cut in 3 for 3 cobs at a descent savings.
thank you for all your help and effor

 

[Joe T Vanelli]

@SupraSPL
Hey man,
I'm living in a centimeter country =) but I don't get how you converted inch in cm on page 1.
In the first chart f.e. is written a surface area of 13,09 square inch and 84,43 square centimeter.
On http://www.inches-to-cm.com/ I found the factor of 1in = 2,54 cm. I'm confused.

 

[bggrass]

@SupraSPL
Hey man,
I'm living in a centimeter country =) but I don't get how you converted inch in cm on page 1.
In the first chart f.e. is written a surface area of 13,09 square inch and 84,43 square centimeter.
On http://www.inches-to-cm.com/ I found the factor of 1in = 2,54 cm. I'm confused.

1 sq in = 6.452 sq cm.

Keep in mind it is square.

2.54cm x 2.54cm = 6.4516 sq. cm

 

[Joe T Vanelli]

1 sq in = 6.452 sq cm.

Keep in mind it is square.

2.54cm x 2.54cm = 6.4516 sq. cm

Thanks

 

[hicpic]

Thanks for this info. It always warms my heart that people put forth such effort that clearly has no tangible benefit to themselves, but helps the community at large.

I'm planing on my first diy led grow light. I would prefer a passively cooled build for the sake of simplicity. I would appreciate if someone could check my math on this.

(6) cxb3590 @ 35watts driven by (1) HLG 240h - c1050 which run at 61% efficiency yielding:

103 watts of heat to dissipate. Using 17 in2 per watt for passive cooling that would be about 1750 in2 needed.

If I had a 5.375" heat sink (from heatsinkusa.com) i would get 1926 in2 from a 36" section. I got that number from using the 53.3 in2 surface area per inch of the 5.375" size according to that excellent chart from SupraSPL.

Does my math jive? Also specs listed the weight as "Weight per Inch: .37". Is that 0.37 lb/inch? About 13 pounds for a 36" sections sounds reasonable.

 

[modular]

Hey Bro,

What does the 750R and 750M stand for? Are those prices for 750mm lengths?

If you are actively cooling then it should be ok but I cant recall the active cooling calculation. For passive you want 120cm^2 / heat watt which works out costing a bomb for a bloom light.

A third option I have been reconsidering for my first coulple of lights is the CPU cooler option. I found these on ebay which are virtually identical specs to the GlacialTech Igloo 7223 that doz posted about, with free shipping.

http://www.ebay.com.au/itm/New-4200-RPM-Heatsink-Fan-Cocket-754-939-940-for-AMD-CPU-Athlon-64-HK-Shipping-/231676284129?hash=item35f0fb8ce1:g:HxEAAOSwMmBV6WgR

Hey guys, did you guys work out what is the best heat sink option for the people located in AU & NZ?

I'm planning on starting with the configuration of (4) cxb 3590s @1400ma powered by a MW HLG 185h-c1400 driver.

I would like to create a modular type of fixture design that I can easily expand at a later stage.

It appears heatsinkusa.com is out of the equation as standard shipping to Australia is $86 US on top of the cost of the heatsink.

Did anyone get around to testing any of the heatsinks available from Conrad Heatsinks?

@SupraSPL from earlier posts I get the impression you don't think the previously discussed heatsinks from Conrad won't be suitable for passive cooling, would any of the heatsinks from their range be useable to passively cool a (4) cxb 3590 configuration?

http://www.conradheatsinks.com/products/flat100_350.html

If the shipping is too expensive to justify purchasing from heatsinkusa.com and their isn't a suitable heatsink available from Conrad would you recommend mounting directly to the back of 4 CPU coolers such as the Arctic Alpine 64 Pro?

Thanks in advance

 

[SupraSPL]

The widest profile MF35 might be the best for passive cooling because it will have the most openings. Fin spacing and base thickness are good, but the fin height might be taller than ideal for passive. It looks like these are not available at custom cut lengths? If so maximum length is 151.5mm (~6inches)

Since they are not cut to length, that also means it would be tricky/inefficient to use active cooling with the wider profiles because the profile width would be longer than the fins. So that would require multiple ans to hit every fin channel or with a single fan some would simply not get air flow.

In these charts I adjusted the passive cooling recommendation upward to 160cm²/heat W to possibly make up for the fin height. But when it comes down to the best thing to do would be test one and what heatsink temps you get with a digital temp probe.

 

[SupraSPL]

All that said, for places in the world where sourcing ideal heatsinks is a challenge, a good option might be to use CPU coolers. Their cooling performance is top notch and if you pack a lot of power onto one CPU cooler, the cooling can be very efficient and cost very little.

 

[jewbag]

Thanks for this info. It always warms my heart that people put forth such effort that clearly has no tangible benefit to themselves, but helps the community at large.

I'm planing on my first diy led grow light. I would prefer a passively cooled build for the sake of simplicity. I would appreciate if someone could check my math on this.

(6) cxb3590 @ 35watts driven by (1) HLG 240h - c1050 which run at 61% efficiency yielding:

103 watts of heat to dissipate. Using 17 in2 per watt for passive cooling that would be about 1750 in2 needed.

If I had a 5.375" heat sink (from heatsinkusa.com) i would get 1926 in2 from a 36" section. I got that number from using the 53.3 in2 surface area per inch of the 5.375" size according to that excellent chart from SupraSPL.

Does my math jive? Also specs listed the weight as "Weight per Inch: .37". Is that 0.37 lb/inch? About 13 pounds for a 36" sections sounds reasonable.

I am building this exact light. According to the diy cob calculator done by @bggrass this light will produce 88 heat watts which requires about 1500 in^2 or 31" of 5.375" profile to cool passively. I believe supra recommended using the 5.88" profile rather than the 5.375", though I'm not sure. I got six 7.5" long sections of the 5.88" profile.

 

[Corso312]

Was talking to my brother in law at Xmas, he's the guy who is going to help me build my light.. He thinks a copper heat sink would be the way to go.. Supra you agree?

 

[Led Newbie Oz]

I went a heat sink from fastron (Aussie supplier) posted their detail on the previous page.
I ended up going for "H4" profile as it was cheaper ($34 per piece) for a 80cm section.
If I had the spare cash I would have gone for the "H42" ($120ish per 80cm) passively cooled.
Postage a kinda sucked at $70.

The H4 fastron heat sink and shroud (under construciton )

 

[Led Newbie Oz]

All that said, for places in the world where sourcing ideal heatsinks is a challenge, a good option might be to use CPU coolers. Their cooling performance is top notch and if you pack a lot of power onto one CPU cooler, the cooling can be very efficient and cost very little.

Did you check these out, might be an option for those of us in Aus/Nz

 

[SupraSPL]

I am building this exact light. According to the diy cob calculator done by @bggrass this light will produce 88 heat watts which requires about 1500 in^2 or 31" of 5.375" profile to cool passively. I believe supra recommended using the 5.88" profile rather than the 5.375", though I'm not sure. I got six 7.5" long sections of the 5.88" profile.

Yes I think the 4.9" or 5.8" are more passive-friendly than the 5.375" because of its slightly smaller fin spacing and slightly taller fins. The 5.88" is cheapest. Updated these hopefully slightly easier to use, each is shown in 6" length

 

[klx]

Hey guys, did you guys work out what is the best heat sink option for the people located in AU & NZ?

I'm planning on starting with the configuration of (4) cxb 3590s @1400ma powered by a MW HLG 185h-c1400 driver.

I would like to create a modular type of fixture design that I can easily expand at a later stage.

It appears heatsinkusa.com is out of the equation as standard shipping to Australia is $86 US on top of the cost of the heatsink.

Did anyone get around to testing any of the heatsinks available from Conrad Heatsinks?

@SupraSPL from earlier posts I get the impression you don't think the previously discussed heatsinks from Conrad won't be suitable for passive cooling, would any of the heatsinks from their range be useable to passively cool a (4) cxb 3590 configuration?

http://www.conradheatsinks.com/products/flat100_350.html

If the shipping is too expensive to justify purchasing from heatsinkusa.com and their isn't a suitable heatsink available from Conrad would you recommend mounting directly to the back of 4 CPU coolers such as the Arctic Alpine 64 Pro?

Thanks in advance

Hey mate,

If you really wanna go passive you can talk to these guys if you in Oz. Shipping might hurt to NZ. they do custom lengths:

http://www.fastron.com.au/powere_1e.php

For me, I settled on these CPU coolers below and if you just going with 4 COBs they might be useful for you to get a better spread. Worse case you can always go passive later as these are only 6 bucks with free shipping:

http://www.ebay.com.au/itm/New-4200-RPM-Heatsink-Fan-Cocket-754-939-940-for-AMD-CPU-Athlon-64-HK-Shipping-/231676284129?hash=item35f0fb8ce1:g:HxEAAOSwMmBV6WgR

Cheers.

 

[SupraSPL]

Was talking to my brother in law at Xmas, he's the guy who is going to help me build my light.. He thinks a copper heat sink would be the way to go.. Supra you agree?

Copper conducts heat significantly better than aluminum, but it cost more. So when you look at it with cost in mind, you could have more mass and more surface area for the same price by using aluminum, therefore aluminum outperforms copper in practice.


So it makes sense to use copper strategically, some heatsinks use both, copper for the base to move the bulk of the heat quickly away from the junction, then aluminum to spread the heat to many fins with a lot of surface area. If I understand correctly, given the same amount of energy, aluminum will increase in temperature more than copper, increasing the efficiency of the transfer of heat into the air.


For heatsinks that use active cooling, you can use copper efficiently by using a thick copper base and lots of surface area from thin plates. That is the idea behind the heat pipe design. When I tested a relatively small heatpipe cooler, it performed worse than the chunky aluminum style (Arctic 11 for example). When I tested a heavy duty copper heatpipe style it performed equally as well as the Arctic 11 style.



But so far the very best performing heatsink I have tested was a radial style with heavy copper core:

 

[SupraSPL]

I am building this exact light. According to the diy cob calculator done by @bggrass this light will produce 88 heat watts which requires about 1500 in^2 or 31" of 5.375" profile to cool passively. I believe supra recommended using the 5.88" profile rather than the 5.375", though I'm not sure. I got six 7.5" long sections of the 5.88" profile.

Yes I think the 4.9" or 5.88" are ideal for passive cooling. The 5.375" has slightly less fin spacing and slightly taller fins.

 

[modular]

The widest profile MF35 might be the best for passive cooling because it will have the most openings. Fin spacing and base thickness are good, but the fin height might be taller than ideal for passive. It looks like these are not available at custom cut lengths? If so maximum length is 151.5mm (~6inches)

Since they are not cut to length, that also means it would be tricky/inefficient to use active cooling with the wider profiles because the profile width would be longer than the fins. So that would require multiple ans to hit every fin channel or with a single fan some would simply not get air flow.

In these charts I adjusted the passive cooling recommendation upward to 160cm²/heat W to possibly make up for the fin height. But when it comes down to the best thing to do would be test one and what heatsink temps you get with a digital temp probe.

View attachment 3572673

Thanks so much for taking the time to upload those charts man, that is super helpful

@klx @Led Newbie Oz Cheers for the heads up guys, will definitely shoot an email through to Fastron. I'm actually based in Melbourne, so I'm hoping I might be able to pickup the order to save on shipping.

Would be super interested to hear what @SupraSPL thinks about Fastrons H42 model and how is compares to Conrads M35 model.

Thanks again for all the input, props SupraSPL for this invaluable resource

 

[Led Newbie Oz]

Thanks so much for taking the time to upload those charts man, that is super helpful

@klx @Led Newbie Oz Cheers for the heads up guys, will definitely shoot an email through to Fastron. I'm actually based in Melbourne, so I'm hoping I might be able to pickup the order to save on shipping.

Would be super interested to hear what @SupraSPL thinks about Fastrons H42 model and how is compares to Conrads M35 model.

Thanks again for all the input, props SupraSPL for this invaluable resource

Have you purchased your Cobs yet?
Cutter Electronics is based in Aus, prices are good and you will save the paypay fee and shipping.

https://www.cutter.com.au/

Haven't order through them so can vouch for them.
Will be ordering off them in the new-year, will update.

 

[modular]

The widest profile MF35 might be the best for passive cooling because it will have the most openings. Fin spacing and base thickness are good, but the fin height might be taller than ideal for passive. It looks like these are not available at custom cut lengths? If so maximum length is 151.5mm (~6inches)

Since they are not cut to length, that also means it would be tricky/inefficient to use active cooling with the wider profiles because the profile width would be longer than the fins. So that would require multiple ans to hit every fin channel or with a single fan some would simply not get air flow.

In these charts I adjusted the passive cooling recommendation upward to 160cm²/heat W to possibly make up for the fin height. But when it comes down to the best thing to do would be test one and what heatsink temps you get with a digital temp probe.

View attachment 3572673

Thanks so much for taking the time to upload those charts man, that is super helpful

@klx @Led Newbie Oz Cheers for the heads up guys, will definitely shoot an email through to Fastron. I'm actually based in Melbourne, so I'm hoping I might be able to pickup the order to save on shipping.

Would be super interested to hear what @SupraSPL thinks about Fastron's H42 model and how is compares to Conrad's M35 model.

Thanks again for all the input, props SupraSPL for this invaluable resource

 

[hicpic]

Man this thread flies.

I am building this exact light. According to the diy cob calculator done by @bggrass this light will produce 88 heat watts which requires about 1500 in^2 or 31" of 5.375" profile to cool passively. I believe supra recommended using the 5.88" profile rather than the 5.375", though I'm not sure. I got six 7.5" long sections of the 5.88" profile.

Neat, still in the process of building? Did you go with or without lenses?

Yes I think the 4.9" or 5.88" are ideal for passive cooling. The 5.375" has slightly less fin spacing and slightly taller fins.

Ah, should have read into the thread. I just figured most surface area would be best. Didn't think fin spacing needed to be taken into account. Guess if I needed 1500 in 2 in the 4.9", that would be 41" of heat sink.....as my garden is only 34" long maybe active is the way to go.

 

[hicpic]

Man, this thread flies.

I am building this exact light. According to the diy cob calculator done by @bggrass this light will produce 88 heat watts which requires about 1500 in^2 or 31" of 5.375" profile to cool passively. I believe supra recommended using the 5.88" profile rather than the 5.375", though I'm not sure. I got six 7.5" long sections of the 5.88" profile.

Yes I think the 4.9" or 5.8" are more passive-friendly than the 5.375" because of its slightly smaller fin spacing and slightly taller fins. The 5.88" is cheapest. Updated these hopefully slightly easier to use, each is shown in 6" length

View attachment 3572685
View attachment 3572686
View attachment 3572687
View attachment 3572688

Thank for the info again. I originally just went with max surface areas. I didn't think I needed to take into account fin spacing/thickness/etc. I figured they have done the homework and provided what was optimum and I was basically just choosing dimensions. I guess form 1500 in2 of surface area I would need about 41" of the 4.9". That maybe a bit big for my purposes, my garden is only about 35" long. Maybe I'll go active, or maybe 6 smaller pieces arranged parallel. I would have liked the simplicity of 1 giant piece, but part of the fun of DIY if learning and adapting.

On an unrelated note, this is my 3rd attempt to post a reply. I didn't see any of the other 2 make it. But if they did and I'm repeating myself, my bad.

 

[welight]

Have you purchased your Cobs yet?
Cutter Electronics is based in Aus, prices are good and you will save the paypay fee and shipping.

https://www.cutter.com.au/

Haven't order through them so can vouch for them.
Will be ordering off them in the new-year, will update.

Thanks for the boost, we also stock the Mechatronix range of heatsinks in Melbourne, drop me a line if we can assist
cheers
Mark

 

[SupraSPL]

Because it is available in cut lengths, this could be a great option for active cooling. Any idea the price a 1 meter?

 

[modular]

Have you purchased your Cobs yet?
Cutter Electronics is based in Aus, prices are good and you will save the paypay fee and shipping.

https://www.cutter.com.au/

Haven't order through them so can vouch for them.
Will be ordering off them in the new-year, will update.

Hey man, yep will most likely be ordering from these guys stumbled across their discount code thread a couple days ago and couldn't believe they are local.

how did you go with your fastron heatsink, is your fixture actively or passively cooled?

Would be keen to see more close up images of the actual heatsink? How was the quality?

Cheers

 

[modular]

Awesome, thanks @SupraSPL

Would the H42 profile be any good for passive cooling or would you recommend I take the active cooling route?

Thanks again for all your help, really appreciate it. Super excited to start building my panel, will definitely post some images in the coming weeks

 

[BOBBY_G]

I am building this exact light. According to the diy cob calculator done by @bggrass

link to said calculator?

thanks!

 

[jewbag]

@hicpic I have most of the parts and plan on building it this coming week if all goes well. growmau5 and greengenes' youtube vids are my main resource right now for learning how to build this, so check that out if you haven't. No optics yet for the cobs but I probably will eventually when I learn how to best utilize them.

@BOBBY_G www.rollitup.org/t/diy-cob-led-calculator.890214/

 

[PicklesRus]

One of the tried and true CPU coolers many DIYers are using:

100W CPU Coolers:
http://www.newegg.com/Product/Product.aspx?Item=N82E16835186070&nm_mc=KNC-GoogleAdwords-PC&cm_mmc=KNC-GoogleAdwords-PC-_-pla-_-CPU+Fans+&+Heatsinks-_-N82E16835186070&gclid=CL_Ds4Ogk8ICFSgQ7Aod8X8AJQ

I have some of these on order to test with very high dissipation Vero29:
150W CPU Coolers:
http://www.newegg.com/Product/Product.aspx?Item=N82E16835186093&nm_mc=KNC-GoogleAdwords-PC&cm_mmc=KNC-GoogleAdwords-PC-_-pla-_-CPU+Fans+&+Heatsinks-_-N82E16835186093&gclid=CO2fw46gk8ICFQ4Q7Aod6nAAJA

This is a passive CPU heatsink from a 1U rack and is rated at 95W TDP. Does that mean it can dissipate 95W of heat (I.e. It's more than enough for a single soft run cob?). It seems to good to be true as these are so small compared to the other passive designs discussed here.

 

[sanjuan]

Onlinemetals.com is selling overstock 48 inch 1 x 1 x 0.125" 6061 T6 aluminum angle for about half price ($2.91). Use SDMVB for $5 off shipping.

 

[bmgnoot]

it seems we've been hammering out a lot of DiY builds on 5.886" cuts as heatsinkusa is out of stock until mid january. debating whether or not i want to change the order to 4.9" just have my light built to get some plants under it asap. Going passive cooled in a 4x4 tent so a 4.9" x 41" would be a tight squeeze but suppose it would fit. already have another round of 12x CXB3590 3500k CD 36v ordered from kingbrite so i dont want that ultimate power lying around my place not being put to good use! slightly less surface area for slightly more $. what you guys think?

 

[bmgnoot]

seems we've been hammering out a lot of DiY builds on 5.886" as HeatsinkUSA is out of stock or very limited depending on the length you want. they weren't able to fill my order (3x @ 38") and said it would be mid January for a restock. i think she said extruder is undergoing yearly maintenance or something like that. I've already got 12x CXB3590 3500k CD 36v on the way from kingbrite so i dont want all that potential sitting around not being put to good use for 2-3 weeks, especially with plants ready to go under them. in a 4x4 tent it should be alrightish albeit a bit of a tight squeeze with the 4.9" x 41" but then again its slightly less surface area for slightly more money to change the order. probably will do it anyway, thoughts?

 

[klx]

link to said calculator?

thanks!

http://rollitup.org/t/diy-cob-led-calculator.890214/

 

[Led Newbie Oz]

View attachment 3573331

Because it is available in cut lengths, this could be a great option for active cooling. Any idea the price a 1 meter?

Price for H42/750mm $116.05 each, 1-2 days
So I would guess like $130-140 for a 1 meter piece.

The weight of the H42 is something to be considered @ 9.259 kg/M

 

[Led Newbie Oz]

Hey man, yep will most likely be ordering from these guys stumbled across their discount code thread a couple days ago and couldn't believe they are local.

how did you go with your fastron heatsink, is your fixture actively or passively cooled?

Would be keen to see more close up images of the actual heatsink? How was the quality?

Cheers

Fastron where great.
Shipping took 2 days for payment.
The fixture will be actively cooled by these:
www.msy.com.au/pc.../3080-noctua-nf-b9-1600-92mm-case-fan.htm
Will be powering the fans using:
http://au.mouser.com/ProductDetail/Mean-Well/APV-12-12/?qs=DNaZHaGatO18Qhe0x8zzqQ==

The H/S quality was good, straight and smooth.

As for the shroud, if you go actively cooled.
I read in mau5capades (Growmauu5 thread) how he joined his local makers club.
So I went looking for a local alternative (as i don't own a pedestal drill/ finger brake)
Luckily in Australia there is a great resource in Mens sheds:

http://mensshed.org/

http://www.mensheds.org.au/

Find one in your area that has metal working facilities.

 

[PurpleBuz]

This is a passive CPU heatsink from a 1U rack and is rated at 95W TDP. Does that mean it can dissipate 95W of heat (I.e. It's more than enough for a single soft run cob?). It seems to good to be true as these are so small compared to the other passive designs discussed here.

View attachment 3573942

These heatsinks are designed for the air flow inside of a rack mounted server, so while they are technically passive they get a lot of fan air flow through them. I have done some testing on a similar copper hp passive heatsink, and they do require something extra (fan or another heatsink) to pull the heat away. They do a really great job of rapidly spreading the heat away from the cob.

if one shops carefully, you can find used server heatsinks on ebay cheap.. My next light will be using server copper heatsinks that cost me about $4.00 each.

 

[modular]

Fastron where great.
Shipping took 2 days for payment.
The fixture will be actively cooled by these:
www.msy.com.au/pc.../3080-noctua-nf-b9-1600-92mm-case-fan.htm
Will be powering the fans using:
http://au.mouser.com/ProductDetail/Mean-Well/APV-12-12/?qs=DNaZHaGatO18Qhe0x8zzqQ==

The H/S quality was good, straight and smooth.

As for the shroud, if you go actively cooled.
I read in mau5capades (Growmauu5 thread) how he joined his local makers club.
So I went looking for a local alternative (as i don't own a pedestal drill/ finger brake)
Luckily in Australia there is a great resource in Mens sheds:

http://mensshed.org/

http://www.mensheds.org.au/

Find one in your area that has metal working facilities.

Thanks for that info man, waiting to hear back from fastron regarding pricing. Still undecided if I'm going to go active or passive.

What are people's thoughts? Will just be starting with 4 cxb3590s running at 50watts each powered by a HLG-185h-c1400. Will only be growing 2 (3 max) plants at a time in a small grow space of 3 x 4 x 6 feet.

What would you guys do, actively or passively cooled? The idea of passively cooled is appealing because the simplicity of the design and wiring, as well as the less noise due to no fans. However if is going to much more practical and efficient at keeping the cobs nice and cool in such a confined space, I will go actively cooled.

Would appreciate some help

 

[PicklesRus]

These heatsinks are designed for the air flow inside of a rack mounted server, so while they are technically passive they get a lot of fan air flow through them. I have done some testing on a similar copper hp passive heatsink, and they do require something extra (fan or another heatsink) to pull the heat away. They do a really great job of rapidly spreading the heat away from the cob.

if one shops carefully, you can find used server heatsinks on ebay cheap.. My next light will be using server copper heatsinks that cost me about $4.00 each.

That gave me a crazy and completely unnecessary idea, gut a 1u server and build an led light inside it, and build a grow tent out of a server rack.

 

[PurpleBuz]

That gave me a crazy and completely unnecessary idea, gut a 1u server and build an led light inside it, and build a grow tent out of a server rack.

lol that's too funny.

 

[bassman999]

These are from Flip Chip Opto, the Luna 300 in 3000K and 4000K 80cri. They are $70 each and can handle over 600 watts Max. They are also a short drive from me.

I still want to see some efficiency numbers on these from like 50-150 watts

 

[Hampsteri]

Last time i bought these and price was 2,5 euros. They are used heat sinks from HP DL380 G5 server and i removed a cover and just made 57mm hole to it cos i used 60mm fan. It stays pretty cool no matter what u give between 5-12 volts with 50 watt ledchip. Weight is almost 700g.

 

[modular]

Hey mate,

If you really wanna go passive you can talk to these guys if you in Oz. Shipping might hurt to NZ. they do custom lengths:

http://www.fastron.com.au/powere_1e.php

For me, I settled on these CPU coolers below and if you just going with 4 COBs they might be useful for you to get a better spread. Worse case you can always go passive later as these are only 6 bucks with free shipping:

http://www.ebay.com.au/itm/New-4200-RPM-Heatsink-Fan-Cocket-754-939-940-for-AMD-CPU-Athlon-64-HK-Shipping-/231676284129?hash=item35f0fb8ce1:g:HxEAAOSwMmBV6WgR

Cheers.

Hey man, how did you find these fans?

After re-reading this thread in an attempt to properly digest all the information, I reckon you nailed it and I'm going to take yours and @SupraSPL 's advice. I'm going to go the actively cooled CPU cooler route to start with and may experiment with a passively cooled fixture at a later date

Now to decide on a CPU cooler with attached heatsink.. Leaning towards the tried and tested Arctic Alpine 11, was wondering how these compare to the ones you posted a link to and something like GlacialTech "Igloo 7223" that @doz posted a little while back?

Thanks to everyone for all the help

 

[klx]

Cant comment on the Arctics or the Alpines as couldnt find them locally. I just trawled ebay for similar sized and specced coolers and found those. I dont have COBs on them yet but they are overkill for cooling. Going to run them at lower voltage to keep noise down as will eventually have 32 of them running.

Good luck and anyway at $6 they cheap as.