Long HDMI Cable Bench Tests - Monster Cable Shootout

Discussion in 'A/V Interconnects, Cables & Power Conditioning' started by admin, Jul 8, 2008.

  1. admin Audioholics Robot Staff Member

    admin
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    I decided to write this article the first time I saw another writer say "HDMI is digital - it either works or it doesn't." Then I saw that statement get repeated over and over. The problem is that HDMI isn't like a digital coax audio cable - it can degrade partially and produce sparkles and snow. We'll illustrate some of this below. It took nearly 6 months to research and prepare for this experiment. I intended to acquire as many HDMI cables as possible and focus on empirical testing of mostly longer lengths to show the differences that abound when you exceed 5 meters. The exercise, I believed, would save many consumers from losing lots of money and time - on a number of levels.
    [​IMG]

    Discuss "Long HDMI Cable Bench Tests - Monster Cable Shootout" here. Read the article.
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  2. Djizasse Senior Audioholic

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    After reading this article it seems that it does not matter what HDMI cables we buy, if they're short.

    But I've seen some people report handshake problems and artifacts with cheap HDMI cables, problems that were solved with buying a more expensive cable. I've also seen people reporting having no problems with the same cheap cables.

    I guess that cheaper cables are more susceptible to EMI, I imagine that some setups generate more EMI than others and that cable position in the setup may also magnify the interference. I would really like to see some EMI tests with HDMI cables. One thing is generating a signal and analysing it after it crosses a cable, other is submiting the test to some sort of EMI.
  3. Clint DeBoer Banned

    Clint DeBoer
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    It would be cool to test that using some sort of standardized source/method. We were unfortunately strapped for time in what we could do... and with that many cables to plow through it took a while.
  4. MinusTheBear Audioholic Ninja

    MinusTheBear
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    Score one for Monoprice HDMI cables. For a price to performance ratio I guess you can't beat them. I guess M cable lawyers will have to re-think any future lawsuits against Audioholics after this positive and uplifting review of the performance of their HDMI cables:eek::rolleyes:
  5. itschris Moderator

    itschris
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    Great article. Hats off.

    I'm not sure about the "any cable" if it's a short run either. I ran into all kinds of problems with the stock cable that came with my OPPO player, which has subsequently been put to use by neighbor between his SA8300 and his TV. Not a single issue. It's odd that it works in one scenario but not another.

    But like you said, there will be a number of exceptions, though I believe the overall impressions are completely on base.
  6. avliner Audioholic Chief

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    Clint,

    nice and educative reading, indeed!

    I've read a lot of complaints on HDMI stuff as well, most notedly the @#$$% handshaking issues, though.

    Lucky me, so far, as I've never had any issues whatsoever, either with short or long run cables. I do own a 50' cable from AVR to PJ which is basically unknown, but seems to have good quality, though.

    BTW Clint, have you heard about TORPEDO brand before? That's the 50' cable I'm talking about! I've got it about a year ago down in New Orleans for a very good price though.

    Regards, Chuck
  7. KurtBJC Audioholic

    KurtBJC
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    Hey, Clint: a question, and a note:

    The HDMI spec requires high-bitrate testing (which, in the case of the spec, is done only at 340 MHz/3.4 Gbps) to be done with something called the "reference cable equalizer" in line. I believe this is done by software. However, Monster (which I understand supplied the use of the gear) likes to do its high-bitrate testing without the reference equalizer. Were your tests done without the equalizer?

    The reason I ask is this: I think that the results, if done without the reference EQ, are probably not meaningful above the 1.65 Gbps rate (second column of your chart). Let me give you an example of why this is so.

    When we submitted our 25-foot Series-1 HDMI cable for testing at the HDMI ATC (Authorized Testing Center), which does the official, impartial HDMI testing, we examined our eye-patterns to figure out whether we were likely to pass a longer length. As you probably know, the testing for Category 2 is run at 165 MHz clock unequalized, and 340 MHz clock equalized. The product development engineer at Belden (Dave DeSmidt) and I examined these eyes and did a sort of graphical estimate, based on performance at 25 feet, of what the performance would look like at greater distances--specifically, at what distance we would cross from pass to fail. What we found was that while we were very close to failing the 165MHz (1.65 Gbps) test, and would probably not pass it beyond about 27 or 28 feet, we were very far from failing the 340MHz (3.4 Gbps) test. We estimated that our failure point for the 3.4Gbps rate would come at a whopping 81 feet.

    High-bitrate equipment is supposed to have EQ circuitry, and this is the concept behind running these tests in this fashion. Accordingly, the non-equalized testing which Monster likes to do is not reflective of a real-world usage condition. So, for example, your chart shows our 30 foot cable failing the 3.4 Gbps test, but we know from ATC eye patterns that the cable will pass that test, equalized, with enormous margin to spare; and, because the equipment made to handle these speeds will contain similar EQ circuitry, the cable not only will pass the ATC test but will perform perfectly in use.

    By the way, we are now looking at a new testing solution from Tektronix which may make eye-pattern testing much more affordable, and I'm hoping to buy it within the next year. If we do, I'll let you know, and we'll start publishing some detailed eye-pattern analyses of our own. Currently, the problem, as you note, is that the test gear is quite costly.

    Kurt
    Blue Jeans Cable
  8. Clint DeBoer Banned

    Clint DeBoer
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    I'm very interested in the new testing equipment you're looking at. These tests were done a bit differently than the ATC, simply because MC wasn't going to take the time to rejigger the software to fit our exact requirements... As a result there is no jitter introduced in the source signal, etc.

    Those looking at our results should indeed be aware that there is EQ circuitry which makes these results less significant. What you're seeing in these tests is pure cable, no EQ, with varying bandwidths. They are "naked" as it were. Taking HDMI 1.3 into account the results can only get better.
  9. KurtBJC Audioholic

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    I didn't realize that; actually, looking at the eyes I should have noticed that they couldn't have any source jitter because the traces just aren't wide enough. That's a pretty huge problem in terms of being able to rely upon the tests--we have found vast differences between test results with and without jitter, and the HDMI spec requires quite a large injection of jitter to make it work. If you'd injected the jitter, a huge number of those "pass" results would have moved into the "fail" category--even, in some cases, on fairly short cables.

    I will let you know if we do acquire a test setup; it may still not be the full ATC setup, but we won't buy it if it won't let us model every aspect of the ATC testing.

    Kurt
    Blue Jeans Cable
  10. Adam Audioholic Jedi

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    Adam,
  11. smurphy522 Full Audioholic

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    A wonderful and praise-worthy test!

    By not bashing Monster it appears Audioholics has possibly extended their lawsuit by another quarter.

    However with so much truth being revealed everyday I fear it is only a matter of time before Tom and Clint get a notice from Monster's lawyers.
  12. Jim Robbins Audioholic

    Jim Robbins
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    In my personal experience, about 6 months ago, I was looking for a longer HDMI cable for my theater setup. I had been using a 10M (33ft) DVI Gear SHR cable from my HD-DVD player to my 720p Panasonic projector and all was well. I decided to upgrade my receiver to the Denon 3808ci and it was a couple feet farther than the HD player, so I bought the 35ft Blue Jeans cable (their newest series) and hooked it up to a new Panasonic AE2000U 1080p projector.

    No signal would get from the Denon to the Panasonic through the BJC HDMI cable. I was able to hook it directly up to my cable box, which output 1080i, and it would sync. But if it was hooked up to the PS3 or HD-DVD player, it wouldn't. And of course, even at 480p from the Denon, it also wouldn't sync. It was just black. I was very frustrated because I had just put this cable in the wall and ripped out the 2 foot shorter DVI gear cable.

    Well, I hooked the DVI gear cable back up and everything worked from the receiver. No more blank screen, and all was well, except I had to cut some corners with my old cable.

    I just returned the Blue Jeans Cable and used the DVI Gear cable. They proposed that the cable might have been bad, which may very well have been the case, but I had already put the DVI Gear cable back in the wall so I didn't want to mess with it again.

    For what it's worth, I think the 10m / 33ft mark might have been the breaking point for either company's cable in my particular situation. Perhaps that's why the 12m DVI gear cable automatically includes the active signal device. *shrug*

    Later...
  13. birdonthebeach Full Audioholic

    birdonthebeach
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    I think we should begin referring to Gene, Clint and Tom as the MONSTERS OF HOME AUDIO AND VIDEO...
  14. avliner Audioholic Chief

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    I wouldn't bet on that, though...

    ...I've heard thru the grapevine that AH is just about ready to release the review of Monsters, Inc. motion picture; therefore...;):):D:(:p

    Regards, Chuck
  15. Dezoris Audioholic

    Dezoris
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    I have done 3 installs with the BJC Series-1 Belden Bonded-Pair from Blue jeans at 30 and 35 feet using a 1.3 Yamaha and the AE2000U with no issues.
    Sounds like a bad cable.

    But this article is going to be reference material on the net for HDMI cables.
    Well done.
  16. mtrycrafts Audioholic Slumlord

    mtrycrafts
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    Perhaps it is not the cable but the signal sensitivity required at the receiving end? Some may need a stronger signal than another unit? Perhaps these difficulties are at the borderlines?
  17. KurtBJC Audioholic

    KurtBJC
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    A lot of these sorts of inconsistencies in cable performance crop up--we hear about them all the time and it can be hard to figure out just what's going on. We do have some ideas, though, which probably explain a large part of it all.

    First, there is the mysterious and weird realm of the DDC (Digital Display Channel). Excessive capacitance can be a real problem here because this is not an impedance-matched circuit and the impedance is typically run "low into high." Not a problem at short lengths, because this is low-speed data, but it can become a problem at longer lengths. It is very hard, unfortunately, to limit DDC capacitance very effectively--and, at some length, the impedance mismatch itself will start to make a mess of it.

    Second, intermediate devices (switches, boosters, splitters, etc.) sometimes are active when they appear to be passive, and sometimes are linked to the 5v DC channel. In some cases even when there's an external power supply hooked up, the continuity from the 5v pin to the power supply for the device may be connected, and this is potentially problematic because the 5v is intended as an "on" indicator, not as a source of significant current. When the cable length is long, and when something is loaded on this line, there can be a voltage drop at the display end, with somewhat unpredictable consequences.

    Third, it has always been true that devices vary in their ability to generate strong and clean signal or to properly interpret weak and dirty signal. The differences here can be profound; we have found cases where a given source to one display through a given cable will go one distance, and changing out the display cuts the working distance to half.

    Fourth, the jack/plug interface is problematic. Some jack/plug combinations are fairly tolerant of a bit of side stress or up/down stress on the interface, while others are not. Users often interpret the funkiness of the jack/plug interface as meaning that the cable is intermittent, because when they wiggle the end they can get it to work--but we find that, while cable intermittency at the connector is always a possibility, we are usually unable to reproduce reported intermittency when the cable is tested.

    Fifth, it is certainly clear that cables can introduce problems which can screw the signal up. Not only is impedance control difficult, but crosstalk or skew can mess things up very badly. There is a tremendous amount of pressure on the market to keep costs down and we have seen some nasty cable assemblies.

    Sixth, it is likely that sometimes a cable swap fixes an issue simply because it's a swap. Unplugging and replugging reinitializes (or should) the HDMI interface, and so if what is really needed is a sort of HDMI "reboot" a cable swap will do that, leading to the perception that the swapped-out cable was broken and the new one is good, when both may be good.

    This list is not exhaustive. There are all manner of potential issues with device interaction, especially when there is switching, boosting, EQing, et cetera in the mix; and whenever you think you've seen or thought of everything, something else happens.

    Kurt
    Blue Jeans Cable
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  18. mtrycrafts Audioholic Slumlord

    mtrycrafts
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    By chance any of the longer cables had 24ga or 22 ga wire in them and if that made a difference compared to others with small wires?
  19. avliner Audioholic Chief

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    Kurt,

    all I gotta say is: hats off to you, for the excellent explantion!
    As the old says goes: not all that glitters...:rolleyes:
  20. LXIX Audiophyte

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    What good sports...

    I have to say you guys have been pretty critical of Monster over the years (rightfully so in most cases).

    I find it refreshing that they would allow you to conduct this testing with their spare rig... as opposed to telling you to go and pound sand.

    With that said, I still question their motives, after all it has been stated that they are conducting a raw test without EQ and this is not part of the standard above a given citrate.

    Is Monster trying to prove that they build a cable that is sooooo far beyond spec that it can handle anything that may arise, or were they hoping to make others look bad?

    Only Monster knows for sure.

    P.S. Great article by the way, I only wish you had used the cables from founding members of HDMI LLC like Sony and Panasonic. It would have been interesting to see how they held up given their involvement in the evolution of the standard.
    LXIX,

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