Long HDMI Cable Bench Tests - Monster Cable Shootout

[admin]

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.


Discuss "Long HDMI Cable Bench Tests - Monster Cable Shootout" here. Read the article.

[Djizasse]

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.

[Clint DeBoer]

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.

[MinusTheBear]

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

[itschris]

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.

[avliner]

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

[KurtBJC]

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

[Clint DeBoer]

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.

[KurtBJC]

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.

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

[Adam]

I still have to read through the AH article (I'm at work), but seeing the thread title reminded of another test that I mentioned here last year.

Part 1: http://gizmodo.com/gadgets/field-not...ble-266616.php

Part 2: http://gizmodo.com/gadgets/hdmi-cabl...t-2-268788.php

I found it quite interesting. I'll hit the AH article tonight when I get home.

Adam