Isn't the wide yellow band desirable? What do you mean "makes up" for? What is the best spectrum?
I think he was talking about a light source with a higher cri. Like a cmh for example. The 3000k spectral curve is nice no doubt...but I'd think a high cri version would be even better if it could maintain efficiency the same.
Like the spectral dot type cobs. High cri with bold claims about the performance even with lower efficiency...then say a cxa 3070.
Regarding the red /amber/yellow/green ....=>
click!
"Makes up ' ..Maybe wrong expression ..
At low irradiances ( 200-300 umol/sec/Sq.m ) Warm white 3000K ( 80 CRI ) ,if used solely ,
will grow some bud ...Thing is that at such irradiances ,the green wls percentage will envoke
Shade Avoidance Syndrome ... Not necessarily with a negative impact in yield ,but neither with a 'positive' ..
But with a certain impact at the morphology/physical appearance of the plant(s) ...
(Extended leaf stems ,for example ...Large ,thin (thus 'sensitive' ) leaves ...Etc ..)
At such low irradiances ,green wls are not necessary ..
Better that % of power ,to've been at red or amber wls instead of green ..
Blue & red led combinations,still are the most efficient at those flux densities ...
Given the fact that they are used as supplementary illumination to greenhouses and
with bedding / flooring growing techniques ...
And output power spreaded over large surface / area ...
Nothin' can beat them ,at this type of horticulture ...
Still ...
They are used for plants that they do need more than 300umol/sec/m^2 to grow...
(peppers and tomatoes are some exceptions ,but then B&R combos are used as supplemental illumination,
to natural sunlight ,in nothern countries ...)
If leds are to be used as the solely source of illumination and at high irradiances ...
Then green wls ( 520-550 nm ) are mandatory ...
Yellow wls(550-590 nm ) are also mandatory ..
Amber (590-610 ) wls are mandatory ...
Low reds (610-640 )are mandatory ..
Deep reds (640-700) are mandatory ...
Mandatory ,if we 're still referring to the highest photosynthetic activity possible ,under i.e. 700umol/sec/m^2 ,
for 12 continuous hours ,at same power (irradiance ) levels ...
You can still supply 700 umol/sec/m^2(or more ) of red & blue wls ...
And ,of course saturate or even fry the plants ...
(it won't even take half of the 12 hour exposure duration,for photosaturation to 'kick in ' )
( Do not expect high yields at this exact situation described...
Test it ...Get the best blue & red leds ,available on the market ...
And try to grow with 700umol/sec/m^2 of blue and red ... Try it ..
I dare you ...And then compare it with plants grown under same quanta flux density
of white light ,coming from a CXA 3000K ... )
..Anyway ...Warm white led light ,probably can grow plants ,in the best possible manner ,
achieved by solid state light ..
It takes the right leds/arrays (efficient ) and plenty of power ,to make it work ...
And here it gets 'complicated' ....
In my fixture ,to give you an example ,
4x CXA3070 3000K Z4 are driven up to ~
2A ...
For an average -stable-operating
Tc =45C ,the leds efficiency is
~33% ...
(Slightly better radiometric efficiency than a HPS 400W ) ..
The leds have a total electrical power of
312.3 Watts.
To keep Tc=45C ,the fixture has active cooling ..
So total (
@Plug ) power of fixture is about
340W (fans at lowest setting ,CXAs @2 A )
(with fan psu,cc led drivers,MCU,LCD display,Voltage reg along with fans ..)
Output irradiance is about
103 Watts ..
15-17 Watts lower that the output of a 400W hps ...
But with same or even more quanta flux (umols/sec ) ,than the 400W HPS ..
(Due to more output in red wls ,of the CXA 3000K than in HPS )
So 4x CXA 3070 driven @2A ,one can assume that is the SSL replacement of a 400W HPS ..
(with slightly better el efficiency,way longer service life,slightly lower output power in W ,better spectrum and better
heat management of a 400W HPS..)
And all that in a pretty reasonable price tag ...
.....
Now ....
What about if ...
If instead I had used
16x CXA ,but driven at
500mA ?
For the same Tc temperature ..
Efficiency of arrays would have been
46% !!!
The el.power (total ) would have been
272 Watt.
Output light power (total) would have been
~125 Watt !
Given the -slightly- better spectrum ....
At this case ,I've surpassed by far the growing efficiency of a 400W HPS ...
Fan Power for keeping the TC at 45 C ,is also lower ..(more arrays ,lower driving current )
Thing is ...I would have needed 16x CXA arrays ,16x CC drivers ..more heatsink mateial ..
More space ,thus multiple panels or even larger case ..And so on ...
And ,of course ,I would 've needed another ..'cash budget' ..Way bigger/larger ....
Anyway ...
No matter what or how ...
The CXA3070 array is trully a '
breakthrough' in led horticulture ...
(At last ...)
It can be used either hard driven -and few parts needed - to grow like a HPS does ..
( With Very closely 'alike' characteristics ..Spectrum,efficiency,el.power ,irradiance ,etc )
Or it can surpass ,in every characteristic the average 400-600-1000 W hps ..
If used as 'many and soft driven ' and not as ' few but hard driven '
Trully utilising less energy ,to grow more efficiently,better & higher yielding plants ,than the HIDs ...
And-of course- still ,price/total cost is the greatest 'discouraging' / limiting factor ,at such case ..
Secret with CXA3070 array is ...are ..two of them ...
-Good cooling ...
-High irradiances ...
You won't believe in your own eyes ,what this array can do ,
if these two ..' conditions' are fulfilled ..
(
solely by itself..Without any other type of leds added )
Cheers.