Do you need new HDMI cables for HDR?

The latest TV technology is high dynamic range, or HDR. If you want to take advantage of this latest and greatest, you need an HDR TV (of course), an HDR-capable source (either a streaming app on your TV or a media streamer/UHD BD player) and HDR video to watch.

But do you need new HDMI cables? Surely those many-years-old, dust-covered, ultracheap cables you bought at Dollar World can't handle this new TV technology?

Well, amazingly enough, they probably can, unless they're really long. That's because there's no such thing as an HDR HDMI cable. Here's why.

Dumb pipe

HDMI cables are just a dumb pipe. They don't care (to an extent) what you send through them. There is no such thing as an "HDR HDMI" cable or an "HDMI 2.0" cable. That second one is important. HDMI cables don't have version numbers. The connections have version numbers. So your TV might be "HDMI 2.0a" (and indeed needs to be for HDR), but the cable you plug into it doesn't have a number. It's just an HDMI cable.

There are four basic types of HDMI cables in the home:

• High Speed with Ethernet
• Standard Speed with Ethernet
• High Speed without Ethernet
• Standard Speed without Ethernet

Nearly every HDMI cable you're likely to buy is the best one: High Speed with Ethernet. And they're cheap: about $6 for a 6-foot version on Amazon, for example.

There's no reason to buy a Standard Speed cable. Any true High Speed cable bought from 2010 onward will also do the same thing as a Standard Speed one (a cable older than 2009, though, is less likely to work).

There are some exceptions, which we'll get to in a moment. The main takeaway again is, there's no such thing as an HDR-capable HDMI cable. If the cable is a true High Speed HDMI cable, it can handle HDR. There's nothing special about the new technology, it's just additional data. Think of it as a little extra water down the pipe. As long as the water can fit in the pipe, the pipe doesn't care what's in it.

Oh, and if it doesn't have Ethernet, that's OK. Nothing uses HDMI Ethernet anyway, and probably nothing ever will.

Update 1/2017: There's been an update to the HDMI spec. The new version is called HDMI 2.1 and it adds several new features including a new cable type. You don't need the new cables or HDMI 2.1 (right now), but it's worth checking out so you've got all the latest info.

What you DO need

Every step in your AV chain (the expensive devices into which you plug the cables) generally must be HDMI 2.0a for HDR to work. As in, your TV, receiver and source all have to be HDMI 2.0a, and usually require HDCP 2.2 copy protection too. If your TV is HDR, it almost certainly has at least one HDMI input with 2.0a/2.2. If your receiver/sound bar is a few years old, it almost certainly does not.

So if you connect a UHD BD player to a 3-year-old receiver that only has HDMI 1.4, it won't matter that your TV is HDMI 2.0a/2.2. The HDR data gets "blocked" at the receiver (or technically, didn't get sent by the player once it saw the receiver was HDMI 1.4).

In this case you might need to upgrade your receiver, or connect your HDR source directly to your TV and send the audio separately to the receiver. That's why some devices, like the Samsung UBD-K8500 4K Blu-ray player, have two HDMI outputs: one "main" for both video and audio, and a second one for "audio only."

Exceptions for length

You maybe have noticed a few weasel words when I talked about your cables working with HDR. In theory your High Speed cable should work just fine. That's the beauty of HDMI, it's a dumb pipe, sending whatever you want over it.

However, despite labeling saying they're High Speed, not all High Speed cables were actually made to handle the maximum amount of High Speed data as specified by HDMI Licensing. Metaphorically speaking, it's like they specified High Speed cables had to be a 1-inch pipe but some companies actually made a 7-/8-inch pipe. This was no big deal when all anyone was sending was 1/2 inch of water. Now that you want the full bandwidth of that pipe, things could be a mess. Not a guarantee, but a possibility.

If the cable's only a meter long, it's probably fine. Even many longer cables will be fine. Long, inexpensive cables at the CNET lab and those used by several of our colleagues all work fine. The longer the cable, though, the more likely you are to have a problem. And, frustratingly, it largely depends on your gear. A 10-meter cable might work perfectly with TV A and Source B, but might not work at all with TV B and Source C.

In CNET's lab we've found that long cables (15 feet or longer) in combination with certain devices might fail with the highest-bandwidth 4K HDR signals. This is really the first time we've seen this issue, and we've seen it happen even with expensive "active" at very long lengths. They'll work with some devices but not with others.

The good news is...

It works, or it doesn't

If it works, it works. There's no "partial HDR" or "blurry 4K." HDMI is all or nothing. If you are getting 4K HDR, different cables won't make it look better. That's not how HDMI works.

If you're not getting 4K HDR, check all your settings. That's the most likely culprit. That said, it's possible for the cable to work fine with 1080p, and not give you a signal with 4K (giving you a black or flickering screen). It's possible for you to set 4K on all your gear, have it try to work and then default back to 1080p.

Annoyingly, there's no way to tell if your current cables will work with HDR just by looking at them. You'll have to try them and see. Assuming your TV is capable of showing HDR (check the manual), if the settings are correct on your source and you're watching HDR video, your TV should give you some indication that it's displaying HDR.

What to do

If you've double-checked all your settings and it's still not working, or you get an image but it cuts out, then you might need a new cable. You don't, however, need to spend copious amounts of money. Most likely a new cheap cable will work just fine.

If you just want to buy one cable that's sure to work, look for Premium Certified cables. These will be a little more expensive, but they're certified to work with 4K HDR content. This doesn't mean that others won't work, or even that the Certified versions will for sure. If you're buying a long cable and paying a lot for it, it's safest (as always) to get it from a place with a money-back return policy.

Many certified cables aren't that much more expensive. For example, Monoprice 's 6-foot non-certified cable is around $2.67. Its certified cable is $4.50, so you're not going to need a second mortgage. For 15 feet, which is less likely to be able to handle 4K HDR, the prices are $5.79 and $9.99 respectively.

But for most people, your current cables will work just fine even with the highest-bandwidth 4K HDR signals.

Got a question for Geoff? First, check out all the other articles he's written on topics such as why all HDMI cables are the same, LED LCD vs. OLED, why 4K TVs aren't worth it and more. Still have a question? Tweet at him @TechWriterGeoff then check out his travel photography on Instagram. He also thinks you should check out his sci-fi novel and its sequel.