There is no single, more important, piece of advice I can give you than this: As of this date -- April, 2018 -- you should be using *ONLY* HDMI Ultra HD Premium Certified cables for *ALL* of your HDMI connections.
The most common point of failure in Home Theater setups is the HDMI cabling. HDMI is only simple, twisted-pair copper cabling, with rather inexpensive electronics controlling the signals at either end. And yet it is being asked to carry substantially higher bandwidth signals these days than when it first came out. It can be tremendously frustrating to put together a fine collection of the newest A/V gear, only to discover you can not get a reliable audio or video signal out of it!
And even more so if you know the HDMI cabling you are using worked just FINE with your prior gear. Heck, it may even be running inside the walls where it is a real nuisance to replace!
The people who control the standards for HDMI are well aware of this problem. Back when 4K video was just a gleam in their eye they promulgated a set of specifications for what was labeled "High Speed" cables. These were supposed to go beyond the needs of the 1080p video of the time, and be good to go when people upgraded to 4K.
But there WAS no 4K gear at the time, so the standards folks built a test rig. This rig was supposed to emulate the WORST "High Speed" cable that could still pass the "High Speed" specification tests. When paired at each end with new (still in development) HDMI transmitter and receiver chips, the test rig demonstrated that things would Just Work. That real "High Speed" cables would be OK in the brave new world of 4K video, once the real, 4K transmitter and receiver chips finally appeared in new, 4K products.
Now that word "real" for the cabling is important, because another big problem with HDMI at the time was bogus cables. Cables that were labeled as having been designed to a certain specification when in fact no such effort had been made. So the point of the test was to say that REAL "High Speed" cables would be OK -- and so any cable that failed must not be REAL.
Alas, when the actual 4K hardware started coming together, there was a sad awakening. Even REAL "High Speed" cables failed at an alarming rate!
The industry quickly came together and did what they probably should have done in the first place: They promulgated a NEW specification for HDMI cables, which rejoices in the name "HDMI Ultra HD Premium Certified". Or "Premium Certified" for short.
While they were at it, they upgraded many aspects of the cable specification -- including, for example, plug design, and survivability in the face of bending. But the biggest single factor is that the new specification required that cable designs actually be tested against real world, 4K signals. No more emulation!
In addition, the HDMI folks also decided to tackle the issue of those bogus cables. Premium Certified cables now come with a fancy, new hologram label that identifies you are actually getting what you think you are getting, and makes it easier for the industry to crack down on fraud attempts. That label looks like this:
You can actually get a free iOS or Android smartphone app which will read that "QR Code" pattern on the label and confirm that the physical label is matched to the cable you are buying!
Even though Premium Certified cables are built to this new, stricter standard, the NIFTY thing is that they need not be expensive! There are multiple vendors offering reasonably priced cables like this. For example, check out Monoprice or Blue Jeans Cable.
The bottom line is that Premium Certified HDMI cables really are just flat out better. And since they are not expensive, these are the cables you should use for ANY HDMI connection -- even when you are not going to be stressing the cable by passing 4K video.
And beware! Because their are still plenty of "High Speed" HDMI cables still being sold out there -- often still labeled as "Good for 4K". Again, these are cables designed to the PRIOR HDMI cabling design standard.
When setting up your cabling, there are a few other considerations to keep in mind, and these apply even when using Premium Certified cables. First of all, cables are specified and tested for a single length of cable between a pair of devices. *ANYTHING* in the cable path may be the source of problems. This would include daisy chained cables, shorty "port saver" cables, HDMI switch boxes, any sort of HDMI gizmo in line with the cabling, and (gasp!) HDMI wall plates! I can't begin to tell you how many times people have discovered their HDMI wall plates are the source of their problems.
Wall plates are those things that look like wall power outlets which you install to tidy up the ends of in-wall HDMI cabling. The problem is, the wall plate works by fanning out the signal wires from the cable on one side, and then fanning them back in for the cable on the other side. And that alone is enough to cause high bandwidth HDMI signals to fail.
The second consideration is length. Most people are aware that HDMI cables will have problems if the cable run is too long. And indeed one of the existing issues with Premium Certified cables is that it is tough to meet the specifications when the cable length gets over about 15 feet. (There ARE some, few, Premium Certified cables out to about 25 feet at this point.) If you have a longer run, you need to consider an alternate -- more expensive -- style of HDMI cabling such as optical fiber with HDMI adapters at each end.
But what most folks DON'T realize is that *SHORT* HDMI cables can also cause problems!
The electronics in the transmitter and receiver chips at either end of the cable attempt to make that simple twisted-pair cabling work even for high bandwidth signals by correcting for the expected degradation of the signal as it traverses the length of the cable. This "Equalization" only works by making some assumptions about how much (and what type) of signal degradation will be present. And first and foremost, that means making an assumption about the length of the cable between the two devices.
And the design point for Equalization is a 6 foot (2 meter) cable!
That means that cables both longer and shorter than 6 foot length will differ from the assumptions built into the electronics. This is EVEN MORE of a problem if the device at either end of the cable is an older HDMI device using older chips that use less sophisticated Equalization methods.
Now just as some people have managed to use longish HDMI cables with no problems, other folks will have successfully used short cables with no problems. Tolerances in the design and manufacture see to that.
But to keep the odds ever in your favor, the ideal cable length for HDMI between any two devices would be 6 feet.
Now if you need a long run, of course you won't be able to do that. But if you have two devices sitting right next to each other, you should *STILL* use a 6 foot HDMI cable between them.
This is just the opposite advice to what you'll get when buying Analog audio interconnect cables for example -- where shorter is invariably better.
So buy only Premium Certified HDMI cables, and whenever possible buy them in 6 foot length.
You'll be glad you did!
--Bob