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Acer K750 LED/Laser Hybrid DLP Projector Review

Is Acer's K750 a glimpse of the future?

by Steve Withers Sep 10, 2012

  • Home AV review

    33
    22,340

    SRP: £1850.00

    Introduction

    As great as projectors are, they tend to have one major drawback - they use a bulb. That means heat, extensive cooling, inconsistent performance and ultimately replacement. Your projector might look lovely and bright when you first set it up but you can bet that brightness will have dropped off considerably after 500 hours of use. That means, within a year, the brightness is 50% of what it was new and by two years it'll have fallen off a cliff! The use of LEDs instead of a traditional bulb seemed to offer a solution but expensive implementation and problems with brightness has resulted in projector manufacturers failing to embrace them the way TV manufacturers have. Lasers offered an alternative approach - bright, consistent, pure - but a health and safety nightmare. Just think how many times you've accidentally looked into the lens of your projector!

    Then some bright spark came up with a great idea; what if you combined the benefits of LED and laser, creating a hybrid light source that has brightness, long life and consistency but isn't going to blind any unsuspecting consumers? Say hello to the LED/Laser hybrid - a light source that combines red and blue LEDs with a blue laser that is bounced off a phosphor disc to generate green. The reason for bouncing the laser off a phosphor disc is two-fold; firstly it greatly increases the brightness of the projector because green forms the largest part of the visible spectrum, and secondly it isn't direct laser light so no one's sight is at risk. We first caught a glimpse of this new approach when we saw Panasonic's new professional projector back in June and we were intrigued. However, the Panasonic isn't released until January and in the meantime, another manufacturer has beaten them to the punch.

    Which brings us neatly to Acer's new K750. Ordinarily we wouldn't review data grade projectors because they're aimed at a very different market to the AV crowd. A data grade projector is designed to be used in schools and boardrooms and as such the priority is on bright images and saturated colours; no one is looking for inky blacks or comprehensive calibration controls. However the K750 uses a LED/Laser hybrid light source, promising 20,000 hours of life and 1,500 lumens, so if it can deliver in other areas it might make an interesting alternative for the AV enthusiast. Aside from the new light source, the K750 is essentially a single chip DLP projector and at £1,850 it is reasonably expensive for a 2D projector in what is a highly competitive market place. Still it could be a small price to pay for an entirely new tech, so let's step into a brave new world and find out.

    Design and Connections

    We mentioned up front that the K750 is aimed at the data grade projector market and this is obvious from its appearance. The chassis has that unmistakable white and silver finish that has graced a thousand boardrooms and lecture halls. The dimensions are suitably bijou for a projector that is designed to be mobile, measuring 321 x 231 x 87mm and weighing in at 3.95kg, which is surprisingly heavy given the plastic construction. Despite that the build quality looks good and the projector has a robust and well-made feel to it. There are intake vents and fans on the right side as you face the projector, some basic manual controls at the top rear and connections at the back. The chassis sits on four feet, all of which can be adjusted to aid installation.


    The lens of the K750 is offset to the right as you face it, there is an IR receiver on the far right and there are manual controls around the lens for adjusting the zoom and focus. As is often the case with cheaper DLP projectors, there are no lens shift controls, so it is important to position the projector correctly when installing it. The projector needs to be position level with the bottom of the screen (or top if ceiling mounted), so be aware of factors such as seating. The lens array appears adequate but no one is expecting the kind high quality glass used on projectors aimed at the home cinema market, and there is a removable plastic lens cap. As mentioned in the introduction, the K750 is a single chip DLP 1080p 2D projector that uses a new LED/Laser hybrid light source, which should help eliminate the rainbow artefacts associated with colour wheels. In the box, along with a remote control, power cable and a user's guide, you also get a composite video cable, a VGA cable and a carrying case.


    The connections at the rear cover the basic requirements for a projector, with two HDMI inputs, a VGA connector and legacy connectors for S-video and composite video. There is also a RS-232 connector, although it uses a DIN style socket rather than the usual serial connector. There are 3.5mm input and output jacks for the built-in speakers, the presence of which betrays the K750's intended market. There is also a three pin power socket and an exhaust fan.


    The remote control is small, made of white plastic and whilst it's comfortable to hold and easy to use with one hand, was rather lacking in the ergonomics department. There is a menu button just above centre with directional keys but just below centre there are also directional keys which, as it turned out, did nothing. In fact the remote is used with many different models, so a lot of the buttons did nothing. There are however some useful buttons such as on/off, aspect ratio and one for cycling through the sources, although you can also select a source directly using the number keys. The majority of the buttons are unlikely to ever be pressed but we were pleased to see that there was a backlight that illuminated the most commonly used buttons.

    Menus and Setup

    The basic set up was very straightforward and Acer even include a grid to help line the image up with your screen when you first turn the K750 on. What is immediately obvious when you do turn it on is that it's up and running in a matter of seconds. The same is true when you switch it off and this immediacy is one of the major advantages of the hybrid technology and an obvious benefit in schools and offices where people have a habit of turning projectors off at the mains. The longer life time is another clear advantage in an environment where the projector can be on all day.

    Once you've performed a basic setup and connected a device via HDMI, the next thing you notice is that the handshaking is quite slow. Whilst this is not a big deal in a classroom it can get quite annoying when trying to play a Blu-ray and the screen keeps going black as the output frequency changes between trailers, menu and film. The K750 should automatically sync to the input and most of the time it did, except on one occasion where it failed to sync properly, causing us to stop the Blu-ray and start again.

    If we found the remote control annoying to use at times, the menu system was equally as frustrating and required some getting used to. Whilst it is relatively simple to follow and clearly laid out, the navigation is less intuitive. To access sub-menus you needed to move right, pressing enter would take you back to the previous screen, in lieu of a dedicated return button. Until we got used to this, we constantly kept finding ourselves jumping out of the menu we wanted to be in, which necessitated the use of a few expletives. The choices within the menu are Colour, Image, Setting, Management, Audio, Timer and Language.


    Despite the name, the Colour menu controls all the picture features and not just those related to colour. The K750 comes with a number of display modes including Bright, Presentation, Standard, Movie, Dark Cinema, Game, Sports and User. The default setting is Standard but for home cinema use, the Dark Cinema mode would seem most appropriate. Interestingly if you change any of the settings, such as Brightness, Contrast etc., the display mode switches to User. This means that if you can't make any changes to the preset picture modes and if you want to optimise the projector for your viewing environment you have to use the User mode.

    Within the Colour menu there are controls for the Wall Colour, which will adjust for the colour of your walls (black in our case), Brightness, Contrast, Saturation, Tint, Gamma and HDMI Colour Range. There is also a Colour Temperature sub-menu that includes a white balance control for calibrating the greyscale and a Colour Management System (CMS) for calibrating the colour gamut. Finally there is an Advanced sub-menu, where you can control the Noise Reduction, Sharpness, Brilliant Colour, White Peaking, Film Mode and Black Extension.

    The Image menu includes controls for the position of the projector (front, rear, ceiling), the aspect ratio (16:9 is the correct choice), keystone corrections (should never be used to avoid introducing scaling artefacts) and HDMI scan information.


    The Setting menu allows you to select the menu location, the security features, perform a reset and control the Picture-In-Picture (PIP) functions. The Management menu allows you to select the ECO Mode, the High Altitude mode, Auto Shutdown, the Lamp Hour Elapse and the Lamp Hour Reset (unlikely you would ever use this).


    The Audio menu controls the built-in speakers and amplification, allowing you to adjust the volume or mute it and set the volume for the noises made by the projector when it powers on or off or there is an alarm. The Timer menu allows you to select the timer location, the timer period and the timer display. The final menu, Language, allows you to select the menu language.

    Out-of-the-Box Measurements

    Since you can't make any changes to even the basic settings without defaulting to the User mode, these measurements are for the Dark Cinema mode which is the most accurate of the presets. Aside from selecting Dark Cinema, the only other changes we could initially make were to select an aspect ratio of 16:9 and a wall colour of Black.


    As you can see the greyscale performance is quite poor with large and noticeable DeltaEs (errors) across the board. If you look at the RGB Balance, you can see there is a lack of blue energy which is why it is tracking below our target and there is a big excess of green, especially at 90-100IRE. There is also too much red in the mid range, a fact that could be seen in actual content, along with a green tinge to peak whites. Gamma is also tracking below our target of 2.2, hitting 2.0 for most of the curve and clipping massively at around 90IRE. As a result the overall image appears washed out and there is a loss of detail in bright white objects.


    Oh dear, the colour gamut is all over the place with large errors in green which is skewing yellow and cyan and equally large errors in blue which is doing the same to magenta. The triangle and squares are the target coordinates for the Rec.709 colour gamut, which is the industry standard used for Blu-rays, high definition TV and PAL DVDs. As you can see green's luminance is too high and also it has a huge error in hue which is, in turn, pulling cyan and yellow away from their target coordinates. Red is also too bright and also over-saturated, whilst conversely blue is lacking in brightness but is over-saturated to quite a large degree. These colour errors were quite obvious on viewing material, with cyan and yellow appearing green and flesh tones having an anaemic look to them. The K750 includes a Colour Management System and it's going to need to be highly effective, if it's going to fix all this.

    Calibrated Measurements

    Moving on to the User mode, we started by setting the Brightness and Contrast correctly using Pluge patterns and then we checked the Sharpness control using an appropriate test pattern. We also made sure that the Saturation and Tint controls were centred, turned on Film Mode and turned off Noise Reduction, Brilliant Colour, White Peaking and Black Extension.


    The User Colour Temperature sub-menu gives you access to the white balance control that adjusts the greyscale, which initially had far too much green and not enough blue. This was similar to the Dark Cinema preset but the difference was that all three colours were tracking parallel to one another. This meant that by turning the green gain control down a few notches, the RGB tracking immediately began to hit our target of 100 and all the DeltaEs were reduced to below 1. We were also able to bring the Gamma in line with our target of 2.2 by experimenting with different settings.

    When we had finished the greyscale and gamma performance were of a reference standard, which rather surprised us. Having said that, there appeared to be no logic to many of the calibration controls, they were fairly crude in terms of fine tuning and the menu covered our test patterns, making the process quite laborious. We also discovered that changing the CMS also affected the greyscale, so there was a lot of toing and froing. We got there in the end but it wasn't easy and it's clear that calibration isn't a priority to Acer, which given their target market isn't a surprise.


    Moving on to the colour gamut, we started by checking the measurements now that the greyscale had been calibrated and was hitting the industry standard of D65. Whilst there were minor improvements, there were still some very large errors, so we went into the CMS and started by centring the Skin Colour control and then moving it in either direction. We expected it to affect magenta but it didn't really appear to have any impact at all, so we left at the centre setting. We then moved on to the CMS itself, which appeared to be quite comprehensive, offering controls for all three primary and secondary colours and allowing you to adjust luminance (brightness), colour (saturation) and hue (tint).

    Once again the controls could be quite crude and the menu covered out test patterns but we were able to improve most aspects of the colour gamut. We were however unable to improve the huge hue error in green or the under-saturated cyan, which we assume are limitations in the LED/Laser hybrid light source. As a result, green had a yellow tinge but otherwise the colour performance was much improved. Whilst not perfect, at least the luminance numbers were accurate, which is important because our eyes are most sensitive to errors in colour brightness. Unfortunately our eyes are also most sensitive to errors in green because that colour forms the largest part of the visible spectrum. So any LED/Laser projector aimed at the home cinema market will need to improve accuracy of green.

    Video Processing

    The video processing on the K750 was reasonable but not exceptional, which considering its primary audience is hardly surprising. Using the SMPTE 133 test pattern it was able to correctly scale the standard definition images without any loss of detail or unwanted ringing. With the video deinterlacing test the results were not quite as impressive with some jaggies on the rotating line. In the motion adaptive deinterlacing test the performance was also mediocre, with jaggies on the bottom two lines. In the cadence tests the K750 correctly detected the 2:3 (NTSC - USA/Japan) format but failed to lock onto the 2:2 (PAL - European) format. However, it had no problems displaying mixed film material with scrolling video text and was able to reproduce the text without any shredding or blurring.

    The K750 performed better in the tests with high definition content and with the player set to 1080i the projector correctly deinterlaced and displayed both the video and film resolution tests (provided the aspect ratio is set to 16:9) and showed excellent scaling and filtering performance as well as good resolution enhancement. With 1080i material the projector had no difficulties in showing video text overlaid on film based material and also handled 24p content without any problems. On the Spears & Munsil Blu-ray disc, the K750 passed most of the tests including the Dynamic Range High test, showing all the video levels above reference white (235) up to peak white (255) and the Dynamic Range Low test, showing detail down to video level 17 which represents reference black. In fact the only test that K750 had problems with was the peaks for the luma channels of the three primary colours, where blue and red were both clipping.

    Picture Performance

    Despite the fact that the K750 is primarily aimed at the data grade projector market, we actually found that it was capable of producing a very watchable picture. Whilst not perfect, it is likely that most people wouldn't notice some of the errors in colour and thanks to the superb greyscale performance, there was a solid basis for the overall image. The reasonably good video processing also helped and whilst there were some jaggies on upscaled standard definition content, this obviously wasn't the case with high definition content, which actually looked quite impressive.

    Since the K750 is a single chip DLP projector, it inherits all the benefits of that technology and some of the disadvantages. The use of a single chip means perfect convergence, so even if the lens itself isn't of as high quality as some projectors, the K750 can deliver some very detailed images. This was especially true of high definition content, where the projector could take advantage of the higher resolution. The downside was that the sharp image could expose any weaknesses in source material. As we would expect from a DLP projector it also handled motion superbly, with 24p material in particular showing movement that was smooth and judder free. This is one of the major strengths of DLP and the K750 performed admirably, reproducing movement and camera pans with clarity and detail. There was none of the smearing or loss of detail that you will often get with LCD based projectors.

    Of course DLP also has its limitations and one of those is black levels. The better the blacks on a projector, the better the dynamic range and the more solid and film-like the image appears. The blacks on the K750 were mediocre, appearing more like a very dark grey and this detracted from the impact of the image, robbing it of some of its dynamic range. Acer claim an on/off contrast ratio of 100,000:1 but God knows how they measured that; we measured it nearer to 1,000:1 after calibration. DLP projectors often perform better when it comes to ANSI contrast ratio measurements and here the K750 measured 750:1, so in terms of even intra-frame dynamic range it was pretty respectable. Shadow detail was also limited, although we were able to improve this by setting the Brightness control correctly.

    The big selling point of the K750 is the LED/Laser hybrid light source which Acer claim can deliver 1,500 lumens. This number must have been the result of the same creative mathematics used to produce the claimed contrast ratio. Once you had turned off all the features that maxed out the light output, which created errors and clipped the whites, and used a screen larger than a postage stamp, the actual brightness was a more sobering 800 lumens. However this is actually pretty good and the K750 was capable of lighting up a reasonably large screen without any issues and still delivering images with plenty of impact. It's also worth remembering that the LED/Laser hybrid light source won't dim like a regular bulb, so the K750 should be able to maintain those levels of brightness during its lifetime. The other advantage of using a LED/Laser hybrid light source with a DLP projector is that is should eliminate rainbows and whilst this is mostly true, people that are very susceptible might still see them occasionally.

    Conclusion

    6
    AVForumsSCORE
    OUT OF
    10

    The Good

    • Reference greyscale after calibration
    • Excellent motion handling
    • Very good image detail
    • Respectable ANSI contrast
    • Average lifespan of at least 20,000 hours for LED/Laser
    • Near instantaneous on/off without the need for warming up or cooling down

    The Bad

    • Mediocre black levels
    • Errors in colour gamut that couldn't be corrected with CMS
    • Despite use of LEDs there are still very occasional rainbow artefacts
    • Inaccurate preset picture modes
    • Unable to adjust preset picture modes
    • Fans can be a little noisy
    I own this 0
    I want this 0
    I had this 0

    Acer K750 LED/Laser Hybrid DLP Projector Review

    The Acer K750 has the classic white and silver look of a data grade projector. It is small, compact and designed to be mobile. Whilst constructed of plastic, the build quality is actually quite good and has a robust feel. There are a basic set of connections at the back and the K750 comes with a reasonably effective remote that at least has a back light. Setup is relatively straightforward but the lack of lens shift means that careful placement is necessary. The menu system is well laid out, if a little idiosyncratic and there is a reasonable set of calibration controls.

    The best out-of-the-box setting is Dark Cinema but this is subject to some sizeable errors and can't be tweaked in the menus. Instead you need to use the User menu and the calibration controls in order to get a reasonably accurate picture. The greyscale was actually capable of a reference performance but even with a colour management system, there were errors in green that could not be corrected. This is presumably a by-product of the LED/Laser hybrid light source. The video processing was reasonably good, especially with high definition content but there were jaggies on the standard definition tests and the K750 failed to detect 2:2 cadence.

    Despite the fact that the K750 is primarily aimed at the data grade projector market, we actually found that it was capable of producing a very watchable picture. Whilst not perfect, it is likely that most people wouldn't notice some of the errors in colour and thanks to the superb greyscale performance, there was a solid basis for the overall image. Since the K750 is a single chip DLP projector it can deliver some very detailed images and it also handled motion superbly, with 24p material in particular showing movement that was smooth and judder free. This is one of the major strengths of DLP and the K750 performed admirably, reproducing movement and camera pans with clarity and detail. There was none of the smearing or loss of detail that you will often get with LCD based projectors.

    Of course DLP also has its limitations and one of those is black levels. The better the blacks on a projector, the better the dynamic range and the more solid and film-like the image appears. The blacks on the K750 were mediocre, appearing more like a very dark grey and this detracted from the impact of the image, robbing it of some of its dynamic range. Acer claim an on/off contrast ratio of 100,000:1 but God knows how they measured that; we measured it nearer to 1,000:1 after calibration. DLP projectors often perform better when it comes to ANSI contrast ratio measurements and here the K750 measured 750:1, so in terms of intra-frame dynamic range, it was quite respectable. Shadow detail was also limited, although we were able to improve this by setting the Brightness control correctly.

    The big selling point of the K750 is the LED/Laser hybrid light source which Acer claim can deliver 1,500 lumens. This number must have been the result of the same creative mathematics used to produce the claimed contrast ratio. Once you had turned off all the features that maxed out the light output, which created errors and clipped the whites, and used a screen larger than a postage stamp, the actual brightness was a more sobering 800 lumens. However this is actually pretty good and the K750 was capable of lighting up a reasonably large screen without any issues and still delivering images with plenty of impact. It's also worth remembering that the LED/Laser hybrid light source won't dim like a regular bulb, so the K750 should be able to maintain those levels of brightness during its lifetime. The other advantage of using a LED/Laser hybrid light source with a DLP projector is that is should eliminate rainbows and whilst this is mostly true, people that are very susceptible might still see them occasionally.

    The Acer K750 is primarily aimed at the data grade projector market and as such there are limitations that don't make it ideal for use in a home cinema. However the LED/Laser hybrid light source certainly has potential and if it can be used effectively in a projector aimed squarely at the home cinema market, it could finally mean the end of traditional bulb based projectors.


    The Rundown

    3D Picture Quality

    7

    Features

    4

    Ease Of Use

    6

    Build Quality

    6

    Value For Money

    6

    Verdict

    6

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