Common Confusion in Home Theater: Part 2

3d1As part of my mini-series of blog posts regarding topics of common confusion in home theater, below I cover speaker resistance and analog vs. digital amps in AV receivers. This series features excerpts from my new Kindle book Home Theater for the Internet Age.

  • Part 1: Volume in a zero dB world, updating firmware, and the disadvantages of Blu-ray
  • Part 3: PCM vs. bitstream and Blu-ray player upscaling/upconversion
  • Part 4: THX certification, DLNA network access, and distortion and THD
  • Part 5: HDMI (including cable length and controversial expensive cables)
  • Part 6: Closed-back vs. open-back around-ear headphones
  • Part 7: Understanding your room and room dynamics
  • Part 8: Room correction, speaker position, and more room dynamics
  • Part 9: Ethernet, component separates, and broadband internet routers

curtsig2 - trans
Curt Robbins


Speaker Resistance: 4 ohm vs. 8 ohm

When it comes to amplification wattage, the general rule is that more is better. But, as mentioned, the clarity and lack of distortion of the audio and video produced by any receiver is as important as the sheer power level. While bigger is typically better, the proper receiver selection involves knowing the speakers you’re getting. In terms of power and electrical current, there are two types of speakers: 4 ohm and 8 ohm. In a nutshell, 4 ohm speakers require less power than their 8 ohm siblings. Technically, 4 ohm speakers feature lower resistance, allowing more electrical current from your amplifier to flow through them.

When researching and shopping for AV receivers, you may find amplification power quoted as two different wattage numbers, one when paired with 4 ohm speakers (the higher figure) and another for 8 ohm models. If a manufacturer or reviewer quotes only one number, it’s traditionally the lower wattage, reflecting the case of driving more common 8 ohm speakers. Beware: Don’t read the higher 4 ohms wattage number and mistake it for the 8 ohm figure. This could convince you that you were purchasing much more power than you were actually getting, possibly allowing your speakers to lag and not reach their full potential.

To get an idea of the difference in power output from an amplifier when powering 4 ohm and 8 ohm speakers, consider that an average 125-watt amp (receiver) when pushing 8 ohm speakers will provide roughly 200 watts when connected to a lower impedance speaker of only 4 ohm. If your speaker selection includes 8 ohm models, you’ll want to investigate if your AV receiver candidates will sufficiently power your particular high-resistance choice. This is an area where personal testimonials—taken with a grain of salt and easily found on YouTube and web forums—are a great way to learn from the mistakes and successes of others.

Generally, especially if you have 8 ohm speakers, you want 100 or more watts per channel (but, again, this is highly dependent on your particular speakers and their specs). Although this book doesn’t delve into the nuances of volts, amps, and watts, it should be noted that multi-channel amplifiers that provide audio to at least five speakers in your home theater pump more watts per channel when driving only a stereo, or two-channel arrangement (the available power is simply spread over fewer channels). Thus, your research project becomes even more complex, because receivers show different performance levels when operating in five channels (movies) or two channels (music and much TV programming). Are you listening to a Led Zeppelin CD or watching The LEGO Movie on Blu-ray? And at what volume? Your receiver, when paired with your speakers, should provide enough clean power to be good at both.

Note that some digital amps can’t power 4 ohm speakers, going only as low as 6 ohm. Carefully compare the specs of the speakers and receiver you choose to power them to ensure that you won’t run into any roadblocks (or have to fall back on a reseller’s return policy).

Digital vs. Analog Amps

Just as display technology is rapidly advancing, with OLED and 4K on the horizon, so too are other areas of home theater technology, specifically receivers and amplifiers. AV receivers have traditionally included analog amplifiers, called Class A/B amps, a technology in use for the past few decades. When digital amps, called Class D, first appeared, their expense put them out of the reach of the average consumer. Pioneer Elite’s first receiver featuring a digital amp, in 2008 (only six years ago), was $7,000.

Like all technology, this highly efficient binary amplification has become much more affordable and begun appearing in receivers priced under $1,500 (sometimes with sub-$1,000 street prices). Digital amplification basically does more with less, minimizing power consumption while producing more accurate, robust amplification when necessary. The advantages of digital amps are especially apparent at louder volumes and when the unit is being taxed, delivering in the neighborhood of 80-90% efficiency. This means that 80-90% of the energy consumed by the digital amp is converted into more powerful sound produced by your speakers (compare this with Class A/B analog amps that, while often producing stellar sonic performance, average 30-60% efficiency). However, preference between Class A/B and Class D digital amps is subjective. Not everyone prefers digital amps.

If Tesla is the next step in the evolution of the automobile, then Class D is the new species in the evolution of affordable home theater amplification. While there will always be those who prefer old school analog (sometimes really old school, as in the case of expensive retro tube amps), digital power processing is the wave of the future. Many who complain about performance issues will be pleasantly surprised with the high-quality and affordable models that will pour onto the market during the next decade.

However, you need to remember: There’s a lot more to a receiver than its amplifier class. As you’ll hear echoed throughout this book, I’d rather have a receiver featuring a really good Class A/B amp than one with a mediocre Class D type. The quality of the audio produced by a receiver when paired with your particular speakers—not whether it features analog or digital amplification—is the real issue.


Curt Robbins is author of the following books from Amazon Kindle:

You can follow him on Twitter at @CurtRobbins, read his AV-related blog posts at rAVe Publications, and view his photos on Flickr.

Goodbye Yellow Brick Plasma

3d1[On October 28, LG announced that it is ending plasma display panel production. As you will learn below, LG was the last major manufacturer of plasma displays. Thus, this announcement effectively kills plasma display tech as we know it. Let’s hope OLED prices fall quickly for those who are in the market for a new TV.]


In early 2014, Panasonic—the Japanese manufacturer of what many reviewers and consumers considered to be the best collection of plasma display panels on the market—announced that it would cease production of these videophile-satisfying models. In official press releases, the company said this move would allow it to focus on 4K (Ultra HD), advanced LED designs, and next-generation OLED. The company cited low demand for plasma models and a need to refocus resources on future standards.

This was the 2:00 am last call at the home theater hobbyist’s saloon. Hard core videophiles quickly revamped their upgrade plans, examining their budgets and trying to decide if they wanted to purchase one final brand new Panasonic plasma TV before none were left to be had.

Later, in July 2014, Samsung announced that it would also cease production of plasma displays, similarly citing low demand and a desire to focus its resources in other areas. LG, the last man standing and lone producer of plasma panels, at the time said in official statements that it would continue to produce plasma sets “as long as there is a demand.” I see. Well, it just so happens that a couple of months earlier, in May, president of LG Electronics Japan, Lee Gyu-hong, explained in an interview with a Japanese news outlet that the company might stop making plasma TVs altogether if sales continued to slump.

This is the sad reality of the marketplace. Unfortunately, home theater hobbyists and quality-sensitive movie buffs—the type of folks who typically would choose a plasma display over its technically inferior LED cousin—aren’t the majority of the market. Despite their liberal spending habits for items like home theater receivers and widescreen display panels, this demographic was simply too small a slice of the pie to influence the few remaining manufacturers of plasma displays to continue production.

In the spring of 2013, I purchased two Panasonic plasma units, a 50-inch model and a 60-incher. They were 2012 models on which I got a killer end-of-model-year deal at one of Best Buy’s Magnolia stores. I’m extremely happy with these units, whether they’re playing streaming video from Netflix or true 1080 content from a Blu-ray disc. After only a year-and-a-half of ownership, and with a viable catalog of readily available 4K content still more theory than reality, I’m not yet compelled to replace either of these TVs.

plasma display panelWhile I’m sad to see plasma depart retailer showrooms, I also know—from the technology industry and Silicon Valley culture overall—that it’s just a matter of time until something becomes affordable that blows away both LED and plasma. And that technology would be OLED (Organic Light Emitting Diode, or Organic LED).

OLED sets can be amazingly thin. We’re talking 4 mm thin, like the spine of a magazine! When it comes to video, OLED models feature better everything. Black levels, refresh rates, color uniformity, off-angle viewing, color saturation…you name it, it’s better on OLED. These models can also produce a nearly infinite contrast ratio (if you want to see this with your own eyes, take a look at one of the OLED-equipped smartphones from LG, HTC, or Samsung). OLED is simply the next step in the evolution of home entertainment display technology. I can’t wait to fill my house with OLEDs. (If you want to learn more about OLED and how it stacks up to other display options, including front projection, check out Home Theater for the Internet Age.)

Of course, nobody in the middle class is going to be filling their homes with OLED display panels until the costs come down. Originally priced at close to $20,000, Samsung and LG are currently selling OLED sets for $10,000 for a 55-incher and $7,000 for a curved 55-inch model, respectively (ironically, LG’s flat 55-inch OLED model is more expensive at $10,000). LG also sells a 65-inch 4K curved (yuck) OLED model for $12,000 retail. This is the first 4K OLED model to break the 55-inch barrier. (It’s been very difficult for manufacturers to produce mass quantities of defect-free, larger-size OLED panels. This explains why the display tech was introduced in devices featuring the smallest, most easily manufactured screens: Smartphones.)

Slowly, but surely—especially as more 4K content becomes available and manufacturing processes improve yields—4K OLED models will come down in price. Just like the chicken and the egg, baby step by baby step, OLED models will become more affordable. For a short period, 1080 OLED models will be offered at very enticing prices. However, I recommend that you forego these killer deals for a true 4K OLED TV that will future-proof you for years to come. It’s going to be a long time before an affordable technology superior to OLED emerges and a resolution greater than 4K becomes standard.

Why no 4K plasma models? Unfortunately, the marriage of Ultra HD and plasma is, from a practical, profit-making manufacturing perspective, very difficult. In a nutshell, it’s cost-prohibitive for companies like Panasonic, Sony, LG, and Samsung to produce plasma sets at the higher resolution of 4K. In fact, 4K is the primary reason that every manufacturer is abandoning plasma production. 4K is their mantra—and plasma doesn’t go there.

Yes, cry a tear for resolution-impaired plasma tech and, if you’re so inclined, sob over the loss of your favorite Panasonic or Samsung model. But don’t fear a lack of innovation among display manufacturers or a slowdown in the evolution of consumer display technology. As long as you have a 1080 plasma (or LED) TV that makes you happy for the next three to five years, hold out for a 4K OLED panel in the size you want. Don’t jump on a 4K LED set, which is really just a half-baked bridge technology intended to help keep display panel manufacturers funded until 4K OLED TVs—the ultimate destination, in my humble opinion—become affordable and go mass market. And when that happens, OLED will make all other display technologies obsolete.

See ya, plasma. It was great knowin’ ya. But don’t fret for me. OLED and I are going to get along great. We just can’t afford to live in the same neighborhood right now.

curtsig2 - trans
Curt Robbins

[Originally published August 23; updated November 9.]

[See also Home Theater Basics, Home Theater: Surround Sound Basics, and Take My Remote, Please.]


Curt Robbins is author of the following books from Amazon Kindle:

You can follow him on Twitter at @CurtRobbins, read his AV-related blog posts at rAVe Publications, and view his photos on Flickr.