Cob vs Strips

I've made my own strip light before with bridgelux. I'm curious though what's the deal with cobs, I used to be interested in them until I found out how easy strips were but seems like folks still build cobs. What's the pros and cons between the two, how do they compare for those that have had both?

taproot said:

I've made my own strip light before with bridgelux. I'm curious though what's the deal with cobs, I used to be interested in them until I found out how easy strips were but seems like folks still build cobs. What's the pros and cons between the two, how do they compare for those that have had both?

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biggest diff i'd say is distance between tops and light. strips might be more efficient, idk but cobs need a heatsink.

sureshot138 said:

biggest diff i'd say is distance between tops and light. strips might be more efficient, idk but cobs need a heatsink.

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A lot of people use heat sinks with strips but a lot don't either when they run them at or lower than <50% total power.

I'd say biggest difference is the light distribution.

Yeah, COBs have alot more W/cm2 so they need more cooling.
With strips passive cooling is the way and depending how soft you run them you could get away with barely the strip's own aluminium.

I like using both together Cobs ain't quite as efficient but they'll get up in them guts

There really isn’t a pro vs cons. Strips are better overall. Light distribution, cost, efficiency. There is a common misconception the cobs have better penetration, however penetration is better with light sources that are spread out as opposed to being concentrated.

I'll tell you one difference not mentioned.

Safety. You can light a cigarette on a COB.

nxsov180db said:

There really isn’t a pro vs cons. Strips are better overall. Light distribution, cost, efficiency. There is a common misconception the cobs have better penetration, however penetration is better with light sources that are spread out as opposed to being concentrated.

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Theres a difference in throw. You can easily build a light with strips which is homogeneous in diode density. But that will give a hot spot in the centre due to cross lighting. Which accentuates with hanging height.
Cobs are more like point like, you can put one each towards the corners and tweak until you actually get it more even than with strips. Or just put strips in the centre and a small cob in each corner.

For throw i prefer boards though, but more of them. At least 4 for a square space. It allows you more control cause a strip will always generate more hotspotting towards the middle while bords or cobs you can control this by running you corner cobs harder on a separate driver than your centre cobs. Its a more complicated build but doable with cobs/boards but not really with strips.

Rocket Soul said:

Theres a difference in throw. You can easily build a light with strips which is homogeneous in diode density. But that will give a hot spot in the centre due to cross lighting. Which accentuates with hanging height.
Cobs are more like point like, you can put one each towards the corners and tweak until you actually get it more even than with strips. Or just put strips in the centre and a small cob in each corner.

For throw i prefer boards though, but more of them. At least 4 for a square space. It allows you more control cause a strip will always generate more hotspotting towards the middle while bords or cobs you can control this by running you corner cobs harder on a separate driver than your centre cobs. Its a more complicated build but doable with cobs/boards but not really with strips.

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Good points.
Built my DIY strip lights in the way that few outermost strips are little more closely mounted.
Just to compensate the middle part a tad.

cage said:

Good points.
Built my DIY strip lights in the way that few outermost strips are little more closely mounted.
Just to compensate the middle part a tad.

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Ots a good work around but as is will only work on one dimension, depth or width. For a perfectly square space you a bit stuck unless you make a square/frame like thing, something like this:

This actually have a another spread even feature, the perimeter has separate dimming, double driver control, and each of the strips have a veg and flower spectrum, which can also be run both at the same time for extra low mA per diode. This one is still my favourite build, its was done for an auto tent where client wanted veg and bloom, but then i got carried away during covid and got him some red sup and figured out the double driver solution. It was well worth it, my client told me he got 350g outta 100w , tent was just over 2.5x2.5. sadly hes still gotta get back to growing, and i wont toot my own horn too much; 350 g of personal stash is not the same as 350 comercial since he was counting a lot of stuff id categorize as fluff and not top shelf. But a nice stash for covid lockdowns which had his country severly locked down.

taproot said:

I've made my own strip light before with bridgelux. I'm curious though what's the deal with cobs, I used to be interested in them until I found out how easy strips were but seems like folks still build cobs. What's the pros and cons between the two, how do they compare for those that have had both?

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They have diffrent uses. Cobs especialy with good lenses will penetrate downwards and hold a higher ppfd verticly rather than spred the light width wise as much. Although you can adjust the width some by using 180° spred or 120° or 90° or 60° . But the more out wards/ width wise you spred the light the less strength downwards. So for example if you want to grow 7-8 ft tall plants and have the buds grow top to bottom good then cobs are great but you will probably need higher ceilings. They use cobs in light houses with specialist lenses wich throw out strong light deep deep into the sky ( smd spred out on flat board wouldnt be able to do that) Oh and cobs can end up costing more as they require specialist cooling sinks and lenses .
With smd led chips used on a flat big surface are better for spreding light width ways more. But cant penetrate downwards as much and after a 1ft or 2ft away the strenght of light will quickly drop. But for tents as they arnt very tall the smd chip boards seem to be more suitable as its cheeper to cool as a flat sheet with smd chips spred out over it cool ok, so its much cheeper for manufactures to make. But you would only get about 2-3 ft of good solid growth with them wich is ideal for tents.
So cobs for strong verticle penetration and smd on board for horizontal spred. Hope that helps

TheWholeTruth said:

They have diffrent uses. Cobs especialy with good lenses will penetrate downwards and hold a higher ppfd verticly rather than spred the light width wise as much. Although you can adjust the width some by using 180° spred or 120° or 90° or 60° . But the more out wards/ width wise you spred the light the less strength downwards. So for example if you want to grow 7-8 ft tall plants and have the buds grow top to bottom good then cobs are great but you will probably need higher ceilings. They use cobs in light houses with specialist lenses wich throw out strong light deep deep into the sky ( smd spred out on flat board wouldnt be able to do that) Oh and cobs can end up costing more as they require specialist cooling sinks and lenses .
With smd led chips used on a flat big surface are better for spreding light width ways more. But cant penetrate downwards as much and after a 1ft or 2ft away the strenght of light will quickly drop. But for tents as they arnt very tall the smd chip boards seem to be more suitable as its cheeper to cool as a flat sheet with smd chips spred out over it cool ok, so its much cheeper for manufactures to make. But you would only get about 2-3 ft of good solid growth with them wich is ideal for tents.
So cobs for strong verticle penetration and smd on board for horizontal spred. Hope that helps

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No matter what you do with cobs and lenses, 3-4 leaves deep into the cannopy there is not enough light for the light down cannopy to really be driving bud formation. Buds all the way down as a function of light is a myth imho; ive seen solid 5g nugs growing low in about 50ppfd environment. If i had the same 50 ppfd on the top id get nothing but the larfiest larf. Those buds growing big in 50ppfd is getting their energy from the top cannopy and they are more a function of pruning lowers and sucker branches, in order to not waste plant energy.

You may be right with a very deleafed grow or a strain if the cannopy is very forgiving (i cant remember the word opposite to dense) but if you got anything like a full cannopy this lense thing isnt going to make as much impact as how you prep your plant for flower.

You are completely right if you have very high hanging height; especially the cobs around the walls or perimeter of the cannopy, lenses help here in order to not lose light to the walls. Bu assuming the cobs in the middle of a large open space wont lose light majorly to walls they are better left uncovered as these will be helped by crosslighting. Light is never lost to air, if just spreads, the case for lenses is not good over a large cannopy but as you say excellent for light houses.

Penetration is one of my pet peeves, to the point i refer to it as the P-word. Nobody seems to be able to actually define it further than buds all the way down (which is covered above), and when defined as light levels in lower cannopy its never really measurable, even if employing stuff like reflectors and lenses - they can help shape the light above the cannopy but they do little inside the cannopy.

You could say that penetration is a function of spectrum though as the lower you go the more green light you find, this is one of the reasons blurple never produced well.

Ymmv

But when your running 6 or 7' plants you more than likely do not have a flat even canopy, more like a mountain range where the strips don't reach the bottom, I have been running malawi gold atm untrained except topping they benefit very well from cob lighting

Rocket Soul said:

No matter what you do with cobs and lenses, 3-4 leaves deep into the cannopy there is not enough light for the light down cannopy to really be driving bud formation. Buds all the way down as a function of light is a myth imho; ive seen solid 5g nugs growing low in about 50ppfd environment. If i had the same 50 ppfd on the top id get nothing but the larfiest larf. Those buds growing big in 50ppfd is getting their energy from the top cannopy and they are more a function of pruning lowers and sucker branches, in order to not waste plant energy.

You may be right with a very deleafed grow or a strain if the cannopy is very forgiving (i cant remember the word opposite to dense) but if you got anything like a full cannopy this lense thing isnt going to make as much impact as how you prep your plant for flower.

You are completely right if you have very high hanging height; especially the cobs around the walls or perimeter of the cannopy, lenses help here in order to not lose light to the walls. Bu assuming the cobs in the middle of a large open space wont lose light majorly to walls they are better left uncovered as these will be helped by crosslighting. Light is never lost to air, if just spreads, the case for lenses is not good over a large cannopy but as you say excellent for light houses.

Penetration is one of my pet peeves, to the point i refer to it as the P-word. Nobody seems to be able to actually define it further than buds all the way down (which is covered above), and when defined as light levels in lower cannopy its never really measurable, even if employing stuff like reflectors and lenses - they can help shape the light above the cannopy but they do little inside the cannopy.

You could say that penetration is a function of spectrum though as the lower you go the more green light you find, this is one of the reasons blurple never produced well.

Ymmv

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Can you put up the exact cobs you used, wat lenses they were and the meteral they were made from, aswell as the lense spread. If light houses are being fited with cobs that can beam out huge distances that says enough. Eg try puting a plant in a 5x5 x 7 tent with 600 wats of smd led chip with a big board or bars. And then do the same with a 600wat cob with the right lense on and put your plant under it. I gaurantee you the plant will be fine with 600 wats of smd on a big board or bars but try that with the 600wat cob and its going to burn the plant right the way through. Ive seen it with my own eyes. Just becase certain midrange cobs are sold to growers dont mean thats all that out ther. Iv seen cobs at like 2000 wats ect. Try putting your plant under one in a tent and tell if it survives over night.
Not sure why you would even grow with 50ppfd ? Try something that gives you a 1000 ppfd at 6ft away. You do realise they used to use glass bulbs in light houses for the reason so ppl can see them from a distance. So if they are putting cobs in them the light still has to travel the same distance and be able to punch through the dark, the clouds, distant acumilated city lights, fogs, mists ect otherwise planes would be crashing into them. So they can penetrate right through a plant and litteraly fry it to a crisp.
If your growing big buds with 50ppfd youve made a break through, im not sure wat ppfd a candle gives but afew of them should be around 50ppfd.

TheWholeTruth said:

Can you put up the exact cobs you used, wat lenses they were and the meteral they were made from, aswell as the lense spread. If light houses are being fited with cobs that can beam out huge distances that says enough. Eg try puting a plant in a 5x5 x 7 tent with 600 wats of smd led chip with a big board or bars. And then do the same with a 600wat cob with the right lense on and put your plant under it. I gaurantee you the plant will be fine with 600 wats of smd on a big board or bars but try that with the 600wat cob and its going to burn the plant right the way through. Ive seen it with my own eyes. Just becase certain midrange cobs are sold to growers dont mean thats all that out ther. Iv seen cobs at like 2000 wats ect. Try putting your plant under one in a tent and tell if it survives over night.
Not sure why you would even grow with 50ppfd ? Try something that gives you a 1000 ppfd at 6ft away. You do realise they used to use glass bulbs in light houses for the reason so ppl can see them from a distance. So if they are putting cobs in them the light still has to travel the same distance and be able to punch through the dark, the clouds, distant acumilated city lights, fogs, mists ect otherwise planes would be crashing into them. So they can penetrate right through a plant and litteraly fry it to a crisp.
If your growing big buds with 50ppfd youve made a break through, im not sure wat ppfd a candle gives but afew of them should be around 50ppfd.

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Dude, just get a ppfd meter down the cannopy of your grow with lenses and youll see what im talking about. Behind the leaf theres shadow. Doesnt matter how you shape the light before it hits the leaf, behind the leaf theres shadow.

If youre growing like this you could easily show me penetration thru the cannopy with a light meter. Of course, if you use a lense focusing a 600w cob onto a plants top cannopy you will fry the plant. Cause yeah, all of what youre saying about your lighthouse. Frying a plant is not penetration and doesnt mean that youll have light under the top cannopy cause its in shadow. Can you get a super strong lense on a cob and make it penetrate a mountain or a wall? Why not? Shadow, it litterally wont go thru things that are not transparent yeah some light goes thru the leaf, thats for sure. How much? Not enough to build buds on its own. Yet there are buds right?


If you fry the plant youre not penetrating, youre burning leaves so once dead theyre dead and gone, hence just air which is also... Transparent.

Check out this thread with measurements of lightlevels in top mid and lower cannopy.https://www.rollitup.org/t/far-red-light-penetrates-the-canopy-more-than-you-think.1096796/#post-17482432

1000/70/10 ppfd. I can guarantee you there was buds in mid cannopy. Fair enough its boards, now show me what you get with your lenses grow, down cannopy about 2feet.


When i say buds at 50ppfd, yes, but my top cannopy is at 1000. Depending how i managed budsites i can get buds of good size towards the bottom, where i have around 50ppfd. No shit. The plant can grow buds with low pofd intracannopy cause it already harvested the light at top cannopy.

If you seen this youre talking about then show us, im betting we will never see any photos showing 800ppfd in mid cannopy cause it seems like youre plain theorising, never actually measured this. Just saw something and felt wow. What youre talking about is focusing light which of course works. Until it hits a solid material which isnt transparent, then you get shadow. Yes a little light goes thru but your insane if you think that little light is what is growing the buds down cannopy, its all

Ill try to see if i can get pics next time im at the grow.

Edit: sorry, i may be getting abrasive on this issue apologize if im getting rough around the edges, the P-word gets me in a bad way

Light sources from different angles is what penetrates, not a single focused beam of light lol. A single focused beam of light is good for seeing at a distance through fog (aka light houses). With plants you need light from a different direction than directly above, people even use side lighting to help with this lol. This is also why ppl running 100 light rooms hang the lights all the way up high at the ceiling, ppfd doesn’t change but the multiple light sources increase the penetration.

nxsov180db said:

Light sources from different angles is what penetrates, not a single focused beam of light lol. A single focused beam of light is good for seeing at a distance through fog (aka light houses). With plants you need light from a different direction than directly above, people even use side lighting to help with this lol. This is also why ppl running 100 light rooms hang the lights all the way up high at the ceiling, ppfd doesn’t change but the multiple light sources increase the penetration.

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Yes, but even so the "penetration" as in bud formation deep into the cannopy is fairly independant of the light levels that hit the lower bud. As ive stated even in low light conditions of buds 40-50cm down; we can get nice hard bud at about 50ppfd as long as weve done the plant management well: not letting them stretch too much as this spends the plants energy and also not letting each and ever budsite flower; too many buds and you spread the plant to thin to generate the right type of bud formation. This is why the P-word peeves me; the thing that people talk about as penetration is not as light dependant as people think. If there is a light component id say its the spectrum: green penetrates deeper, both in the cannopy and in the leaf. This is why old blurples didnt give "penetration" every ounce of light gets absorbed in the top, as well as in the first layer of the thylakoid which means less photosynthesis and less buds in the lowers.

Penetration is a bit of a myth, you just have to know how to grow Well, how to manage your plant. As soon as we dont do this well, and in function of the plants at hand, we get fluffy bottoms. Even though its the same light on the cannopy every run.

The amount of myths about penetration are legion: you need lenses, you need the light to be super intense at the source, cobs and hid can do it and mid powers dont, its just a bunch of grow bro misunderstanding. Confounding of variables, and then chest beating on the forums with no actual critical testing or support.

Id like to say sorry if im.abrasive, not really my intention. I think my keenness to argue here stems from a long history of arguing with growbro arguments about P which is really frustrating; its generally met with arguments that tend towards "feels like/looks like" with little rational content or treatment: intuitive reasoning or at worst magical thinking. This is not to be taken that i dont appreciate this type of "knowing" which comes from experience and intuition and time in the grow, its absolutely necessary as a preparatory stage to reasoning. I take an equal offense to bad science, for example Bugbee has a few experimental designs that really are WTF. The problem with both approaches is when there is both good thinking (rational and intuitive) which ends up hiding the flaws and obfuscating the truth. A good science paper with just a small little flaw in thinking can produce results which the gets thrown about at no end, again based on the belief that what comes out of my mouth can never be wrong.

No matter how you do it you need to have cultivate some doubt in your thinking. Especially if your used to being "right", then how the F will you know when your wrong and when its time to digg out your heels and start looking at things differently. One of the main tennets of science is that it has to be able to generate more testable science and never be a dead end. Growbroing tends towards just believing stuff cause its clear to you and that leaves little possibility to advancing knowledge.

Imo these two types of thinking would do best to try to understand eachother and get closer and actually learn how to get closer to Truth by listening to eachother. Science can be blind to the bigger picture since it has to be so rigorous in order to be validatable. This means it you need to maintain variables constant, during a whole grow. This is not the situation of any grow really, as a grower you need to be able to look at your plants, understand what theyre telling you and react consequently and change whatever is dragging the grow down. This where a more intuitive understanding is usefull, to know when to depart from the rational cause all those small signs that make up a bigger picture is telling you to change something.

I still maintain my arguments re penetration as not even definable or measureable in the terms most people use

But im sorry i dont need to put anyone down for just thinking differently. Its also the whole deal that writing online you cant really translate intuitive reasoning to good and valid arguments - when one does ones best to make such arguments it gets so frustrating to be met by the "feels like" type arguments. Mea culpa lets not have a flame war.

Rocket Soul said:

Dude, just get a ppfd meter down the cannopy of your grow with lenses and youll see what im talking about. Behind the leaf theres shadow. Doesnt matter how you shape the light before it hits the leaf, behind the leaf theres shadow.

If youre growing like this you could easily show me penetration thru the cannopy with a light meter. Of course, if you use a lense focusing a 600w cob onto a plants top cannopy you will fry the plant. Cause yeah, all of what youre saying about your lighthouse. Frying a plant is not penetration and doesnt mean that youll have light under the top cannopy cause its in shadow. Can you get a super strong lense on a cob and make it penetrate a mountain or a wall? Why not? Shadow, it litterally wont go thru things that are not transparent yeah some light goes thru the leaf, thats for sure. How much? Not enough to build buds on its own. Yet there are buds right?


If you fry the plant youre not penetrating, youre burning leaves so once dead theyre dead and gone, hence just air which is also... Transparent.

Check out this thread with measurements of lightlevels in top mid and lower cannopy.https://www.rollitup.org/t/far-red-light-penetrates-the-canopy-more-than-you-think.1096796/#post-17482432

1000/70/10 ppfd. I can guarantee you there was buds in mid cannopy. Fair enough its boards, now show me what you get with your lenses grow, down cannopy about 2feet.


When i say buds at 50ppfd, yes, but my top cannopy is at 1000. Depending how i managed budsites i can get buds of good size towards the bottom, where i have around 50ppfd. No shit. The plant can grow buds with low pofd intracannopy cause it already harvested the light at top cannopy.

If you seen this youre talking about then show us, im betting we will never see any photos showing 800ppfd in mid cannopy cause it seems like youre plain theorising, never actually measured this. Just saw something and felt wow. What youre talking about is focusing light which of course works. Until it hits a solid material which isnt transparent, then you get shadow. Yes a little light goes thru but your insane if you think that little light is what is growing the buds down cannopy, its all

Ill try to see if i can get pics next time im at the grow.

Edit: sorry, i may be getting abrasive on this issue apologize if im getting rough around the edges, the P-word gets me in a bad way

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I dont think you unserstand the same shadow is still there with hid and the sun. The way around that with the sun is it huge so the daylight comes from all over multiple angles. With led the shodows are over come by using more than one point of light. Ther is always going to be some shadow no mater what but thats why there are leaves and ther in multiple places of the plant. The leaves even angle towards the nearest strongest point of light. The more light they can take up,not just afew on the top but accumilate from all over the more its going to put into the plant. One other thing your ppfd meter cant read some wave lengths good, some wavelenghts punch right through the leaves sort of like x-rays. The plant dont see like a human. And for a more better understanding of the ppfd the plant gets try messuring ppfd from every leaf on the plant at the angle it faces. Any way i dont think its a good idea to have the plants grow so close together that no air and light can pass through nothing but the top of the canopy. Also it would depend on growing style as scrog is based around making use of the width to spread rather than growing multiple bigger 5 - 7ft plants. So the grow style,and place mater to fit the right lighting solution.
So my first comment still stands and was to do with the two diffrent styles of led we use cob and smd chips spread out over a board or bars and what the tech is more suited to and designed to do which is what the op asked.

TheWholeTruth said:

I dont think you unserstand the same shadow is still there with hid and the sun. The way around that with the sun is it huge so the daylight comes from all over multiple angles. With led the shodows are over come by using more than one point of light. Ther is always going to be some shadow no mater what but thats why there are leaves and ther in multiple places of the plant. The leaves even angle towards the nearest strongest point of light. The more light they can take up,not just afew on the top but accumilate from all over the more its going to put into the plant. One other thing your ppfd meter cant read some wave lengths good, some wavelenghts punch right through the leaves sort of like x-rays. The plant dont see like a human. And for a more better understanding of the ppfd the plant gets try messuring ppfd from every leaf on the plant at the angle it faces. Any way i dont think its a good idea to have the plants grow so close together that no air and light can pass through nothing but the top of the canopy. Also it would depend on growing style as scrog is based around making use of the width to spread rather than growing multiple bigger 5 - 7ft plants. So the grow style,and place mater to fit the right lighting solution.
So my first comment still stands and was to do with the two diffrent styles of led we use cob and smd chips spread out over a board or bars and what the tech is more suited to and designed to do which is what the op asked.

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I dont know if were talking past eachother. My argument is that lenses will not increase penetration, just that and if you "measure" P with how many buds you get on lowers youre barking up the wrong tree.
I actually agree with most of what you say in this last comment what youre talking about is diffused lighting vrs parallel or focused lighting, yes diffused light is present both from boards and the sun, but in the case of the sun its only half of the story. Sun light is parallel above the atmosphere, as straight as can be as even though the sun is huge in its origin its so far away that once ots reaches the sun its considered both pointlike and parallel. Once it hits the atmosphere (or once somewhat obscured by cloud cover) it gets scattered: this is the part of the sunlight that "comes from all directions" as you describe. But its only part of yhe story as all sun light dont get scattered, some of that parallel light also gets thru. This light can be compared to what you describe as lensed focused lighting and definitely wont be very present going down into the cannopy.

I completely agree that spectrum plays a part here, green does penetrate further into both the leaf itself and further down cannopy, as ive noted above and linked to @Prawn Connery s tests. (Which also show the same trend as below, very little light present after first leaf cannopy)

Have a look at this post by an old retired member, hes posted par and spectrum shots of his original light source, one leaf, two leafs and three leafs over the sensor:

Numbers arent perfect since its repeated measurements but the trend is clear: no matter how many leaves he puts infront of the spectrometer the par readings is never over 2% of the original. Hardly xray like, most light always gets absorbed or at least not passing thru to light the lower cannopy effectively. Sure its not the same as the previous example but the trend is there; there simply is no evidence that the lower buds are formed dependent on how much light is going thru leaf or cannopy.

So where do these buds get their growth from? From the energy harvested on top. Why are they sometimes big and other times small? Depends on how many places the plant needs to support from the light harvested from the top cannopy.

An extremely strong light can "penetrate" further down but not based on going thru the leaf, its based on that those leaves in the top getting +1000ppfd will shirvel up, go thru fade and get yellow then purple (depending on strain etc) and then allow light to further down. But thats a different issue, its not penetrating its destroying the top of cannopy.

Ive been around this block before trying to figure it out and there simply isnt any evidence that focusing the light will get you bigger lowers unless it some way removes the higher leaves. And you can still get good lowers by managing your budsites.

The rest of what youre saying I'm completely onboard, diffused lighting will go further down etc. But the only purpose i see for lenses is shaping the light BEFORE it hits the cannopy and is usefull if that light would hit the wall instesd of the cannopy due to being on the perimeter.

I hope i make sense in this, youre clearly thinking and reasoning about things that are fairly above the general paygrade around her and that is more than many here so i dont wanna step on your toes, i just want to help you to think about this in a diffrent way which is better supported by the evidence at hand. I apologize if i dont have pics at hand of those large buds thriving in low light of lower cannopy but i promise you i have seen it and being a bit perplexed about it, made some test to get to my conclusions. I urge you to do the same if you get the chance, nothing like convincing yourself, especially when it goes against the way youre thinking cause thats when you actually grow your knowledge