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Thread: Cree TW Series LED Bulbs.

  1. #1

    Default Cree TW Series LED Bulbs.

    Has anyone seen or tested the new high CRI Cree TW Series LED bulbs?
    http://www.cree.com/Lighting/Product...White-LED-Bulb

  2. #2
    *Flashaholic* PhotonWrangler's Avatar
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    Default Re: Cree TW Series LED Bulbs.

    At 13.5w instead of 9.5w for the original 60w equivalent, it seems like they're burning up a lot of energy to push through that "spectral notch." Wonder how much hotter it will run.

  3. #3

    Default Re: Cree TW Series LED Bulbs.

    Doesn't look like you can get your hands on them yet, although according to HD's web site you should be able to get them shortly - they are available for order, but about a 2 week wait.

    I'll be interested to see the test results, when someone with equipment gets his grubby little paws on one.

    Good news: $17.97 for the 40W, $19.97 for the 60W. 93 CRI and supposedly dimmable.

    Bad news: abysmal lumens per watt compared to the now-dead L-Prize bulb, but on the flip side you can actually buy these for less than $40 apiece, and they're still better than incans (although really no efficiency improvement compared to a standard CFL; hopefully the light quality is noticeably better.)
    Last edited by N8N; 09-17-2013 at 03:11 PM.

  4. #4

    Default Re: Cree TW Series LED Bulbs.

    The Neodynium glass is a cheap trick, which was acceptable for incadecents (e.g. GE Reveal), but a cynical gaming of the CRI index when used with LEDs.

  5. #5

    Default Re: Cree TW Series LED Bulbs.

    Well, it's being advertised as the first light to meet the California Energy Commission Lighting Quality spec

    http://www.energy.ca.gov/2012publica...12-016-SF.pdf8

    I'm sure that much like the L-Prize bulb, this one was specifically designed to meet the spec (and get contracts, etc.)

    Note that the California spec requires a power factor of >0.9 at full output which is why the L-prize didn't make the cut... wonder why they didn't factor that into their design, because I believe that it would meet all the other requirements. Irrelevant now in any case...

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    *Flashaholic* PhotonWrangler's Avatar
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    Default Re: Cree TW Series LED Bulbs.

    Quote Originally Posted by MattPete View Post
    The Neodynium glass is a cheap trick, which was acceptable for incadecents (e.g. GE Reveal), but a cynical gaming of the CRI index when used with LEDs.
    I am inclined to agree with you. It would make more sense to choose the LEDs and phosphors to fit their spectral distribution targets. Using a colored filter in front of the LEDs feels like we're going backwards. I'm no expert in phosphors but I have to wonder why the blue tinted glass is needed when the LEDs themselves are abundant in blue spectral content.

  7. #7

    Default Re: Cree TW Series LED Bulbs.

    Quote Originally Posted by PhotonWrangler View Post
    I am inclined to agree with you. It would make more sense to choose the LEDs and phosphors to fit their spectral distribution targets. Using a colored filter in front of the LEDs feels like we're going backwards. I'm no expert in phosphors but I have to wonder why the blue tinted glass is needed when the LEDs themselves are abundant in blue spectral content.
    Because it's a notch filter for the yellow part of the spectrum:


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    Flashaholic wws944's Avatar
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    Default Re: Cree TW Series LED Bulbs.

    Since Crees design is apparently able to handle a 13.5w power draw, it seems like a 75w equivalent LED in non-TW versions should be just around the corner.
    "Your light emits unnecessary heat" - Zar

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    Default Re: Cree TW Series LED Bulbs.

    Quote Originally Posted by PhotonWrangler View Post
    ...Using a colored filter in front of the LEDs feels like we're going backwards...
    Agreed - It's not a good technical solution. But, Cree is in business to sell product, and I'm pretty sure they've done their homework. People will buy this and be happy. Cree will make a profit. There's no 'cynical gaming' involved - just a business aiming a product at a target market (which doesn't include most of us, btw).

    I have this old catalog from 1938. In it, GE has 100 W incandescent lamps for $0.20 each. Their 'Daylight' 100 W incandescent lamps (which I assume were using neodymium glass) were almost twice the price - $0.35. I think Cree is doing the same thing 80 years later for the same reason...
    Last edited by brickbat; 09-17-2013 at 07:24 PM.
    Jim

  10. #10

    Default Re: Cree TW Series LED Bulbs.

    After seeing the new Cree LED retrofit, which had a glass bulb, I got to thinking, how would it affect the light if they had used neodymium glass? Would the effect be the same as with a regular incandescent bulb? (For those of you who are familiar with Chromalux "Daylight" or GE's "Reveal" bulbs, these use neodymium glass)

    Probably it is not be quite the same because LED has a different spectrum than incandescent. Filtering is not just about the overall color, it also effects the spectrum. It could potentially be used to raise the correlated color temperature without making the blue spike bigger. Yes, it would make the LED spectrum even a little more discontinuous, but nevertheless I have a feeling it might slightly raise the CRI index. The LED phosphor already has too much yellowish frequency light, and to a much lesser extent the neodymium glass also filters out a portion of the yellowish-green, so by reducing these, it would effectively increase the relative proportions of red and blue-green frequency light in the spectrum. Basically, the net result would be equivalent to "flattening out" the yellowish spectrum hump. The bandwidth of the yellow frequency being filtered out is also relatively narrow, so it would not result in too much color shift.

    Quote Originally Posted by PhotonWrangler View Post
    I am inclined to agree with you. It would make more sense to choose the LEDs and phosphors to fit their spectral distribution targets. Using a colored filter in front of the LEDs feels like we're going backwards. I'm no expert in phosphors but I have to wonder why the blue tinted glass is needed when the LEDs themselves are abundant in blue spectral content.
    Filters can potentially achieve spectrum changes that standard LED phosphors by themselves are unable to accomplish. Blue-green phosphors certainly exist, but would require violet frequency excitation.

    Something else that should be mentioned is that the amount of filtering can make a difference. For example, with neodymium glass (at least using an incandescent source), a lesser amount of filtering results in an increase in CCT, while excessive filtering results in a decrease in CCT. This is because, while the neodymium glass readily filters out the yellow, there is also some absorption elsewhere. Once all the yellow has been completely filtered out, additional filtering just starts taking away from the parts of the blue and green. So, if the filter absorbs more than one part of the spectrum, using too much filtering can potentially result in a color change toward a different color.
    Last edited by Anders Hoveland; 09-17-2013 at 08:59 PM.

  11. #11
    Flashaholic* LEDninja's Avatar
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    Default Re: Cree TW Series LED Bulbs.

    Incandescent spectrum


    CFL spectrum


    Cree XRE Q25A spectrum


    CreeTW spectrum
    Last edited by LEDninja; 11-11-2013 at 05:46 AM.

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    Default Cree TW Series LED Bulbs.

    In a quick test, the heatsink on a 13.5W TW unit easily got to 185 degrees F. Yup, these run hot.

    Interestingly, though, the TW and the regular unit have more red than the L-Prize, as judged by my inexact CD "spectrometer".

  13. #13
    Flashaholic* LEDninja's Avatar
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    Default Re: Cree TW Series LED Bulbs.

    Quote Originally Posted by BLH View Post
    Has anyone seen or tested the new high CRI Cree TW Series LED bulbs?
    http://www.cree.com/Lighting/Product...White-LED-Bulb
    electronupdate has a video review here:
    http://www.candlepowerforums.com/vb/...lbs&highlight=

  14. #14
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    Default Re: Cree TW Series LED Bulbs.

    Well, they have 75watt equivalents now.
    6.5K diving light, 5K cool-white, 4K neutral-white, 3K warm-white, 2.7K extra warm-white

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