Understanding Home Theater Speakers: Part 2

3d1Speakers are arguably the most important part of any home theater setup. They’re certainly where one should invest the bulk of one’s money. You’ll keep good speakers a lot longer than any other home theater gear, especially AV receivers, disc players, and streaming media boxes.

Also check out the previous blog post, Understanding Home Theater Speakers: Part 1. The following is an excerpt from my Amazon Kindle book Home Theater for the Internet Age.

curtsig2 - trans
Curt Robbins


Center Channel

The center channel, as you’ve already learned, is dedicated to TV and movie dialog (it’s nice to hear the sound coming from where a character’s mouth appears) and enhancing the overall immersive quality of music emanating from the speakers facing you. As mentioned, it’s highly advised that your center is from the same series as your front mains. More powerful center channels feature more drivers. Thus, a basic config might be a single midrange or full-range driver, while a more sophisticated example would feature a couple of woofers, one or more midrange drivers, a tweeter, and maybe even ports.

It should be noted that most high-resolution surround sound music formats, such as SACD, and DVD-Audio, all give music publishers the ability to record a center channel as part of a song or album. (See the Disc-Based Music chapter for more information regarding these high-resolution music formats.) Center channel speakers range in cost from under $100 to several thousand.

Subwoofer

As you’ve already learned, a subwoofer is simply a speaker dedicated to the lowest audio frequencies, which you can literally feel in addition to hear. If you really want to shake the house or wake the neighbors, a large, powerful sub can do it. Barry White should have owned a sub company.

A sub is unique in that, unlike your other speakers, it’s a powered unit (300 to 800 watts is common). Don’t dismiss the capabilities of a high-quality 10, 12, or even 15-inch subwoofer. For movies especially, it will become one of your favorite speakers (and something you’ll want to turn down when the kids are asleep).

Omnidirectional

The subwoofer is also unusual among other speakers in that it’s mostly omnidirectional, meaning where it resides in the room and where it’s pointed (the direction in which it fires) are much less important than with your other speakers. This is nice for tucking it discretely behind a sofa or under an end table. Some models, like the uniquely slim $1,400 Paradigm MilleniaSub and the $2,000 REL Habitat1, are specifically designed for narrow spaces, such as under a sofa.

Most subwoofers feature a digital amp. While models with Class A/B analog amps are available, they’re less common. Incorporating a digital amp allows a model to be smaller, consume less energy, and perform with greater efficiency. Just to confuse things, there are also hybrid varieties that employ both analog and digital circuitry at a variety of prices and quality levels. Like other speakers, some subs feature relief ports, a nice addition because ported subs can produce greater output. Subs that aren’t ported are called sealed (just like headphones). The PB series from SVS is a good example, featuring models with between one and three ports each, priced from $500 to $2,000.

Driver Configs & Second Helpings

Like regular floor standing and surround speakers, subwoofers can feature one or more drivers that fire in a variety of directions. The most common configuration is side firing (like my 10-inch, 500-watt, single-driver sealed B&W ASW700) or down firing (like the 10-inch, 150-watt REL T-5). Klipsch’s best sub, part of its Palladium Series, features two 12” drivers powered by 1000 watts that are side firing and 90 degrees separated (this sub is arguably overkill for most rooms). The majority of subs feature a single side-firing driver that’s between 10 and 15 inches in diameter and commonly powered by 500 watts.

As you’ve learned, some home theater hobbyists add a second sub to their home theater, creating a more balanced low frequency experience with even greater impact. However, in dual-sub environments, placement is critical; typically, you don’t simply stack them on top of each other. The debate between one big sub or a couple of smaller units will never cease in the audiophile world. In the end, it’s determined by your room and budget.


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

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

Advertisements

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.