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Home Theater Receiver Buying Guide

The complete guide to what you must know...


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Audio Signal Processing

A receiver may perform a number of audio signal processing functions, depending on the input source and depending on user preferences.  These include digital audio (PCM) decoding, simulated soundfields, bass management, and THX post-processing.

Digital Audio (PCM) Decoding

For digital sources like audio CD, you can connect the CD player using a pair of analog stereo connectors.  In this case the audio signal is already converted from digital to analog form by the CD player and no further decoding is required.  Alternatively, you can use the CD player as a CD transport and hook it up to the receiver using the digital audio output.  If you use the digital audio connection, then the receiver's audio digital-to-analog converter (DAC) is used to convert the raw Pulse Code Modulation (PCM) digital audio signal to analog.  The receiver's audio DAC is usually 24-bit word length and samples at 96 kHz.  Better receivers will have audio DACs with higher sampling rates (up to 192 kHz), or quality audio DACs made by Burr-Brown or Analog Devices.  Unless you have a high performance audio CD player or any digital source with high quality audio DACs, we recommend that you connect the CD player to the receiver via one of the digital audio connections.  This will allow you to use the receiver's audio DAC and simultaneously minimize degradation that usually plagues analog connections.

Simulated Soundfields

Many receiver manufacturers include a number of simulated soundfields (sometimes referred to as DSP modes) effects to imitate the acoustic environment of various real-world venues (e.g., jazz club, concert hall, cathedral, stadium) by adding synthesized early reflections and reverberations.  While listening to these soundfields can be fun, audio purists will find little value with these simulated soundfields as they do not serve the artists' or performers' intentions.  And while it's nice for receivers to include this feature, it should not become a primary consideration when choosing among different receivers.

Bass Management

The receiver's bass management function re-directs the bass frequencies from any channel to those loudspeakers that can handle the low frequency bass information (e.g., full-range floorstanding loudspeakers, subwoofer).  This ensures that the low frequency audio signals are not lost when you're using a system of bookshelf or satellite speakers.  If you have five full-range loudspeakers and a subwoofer (few of us do), bass management is not a concern.  But if you don't, it is essential that you look for a receiver with complete bass management functionality.  Bass management is usually performed in the digital domain by DSP circuitry.

With bass management, you set up your system by telling the receiver whether you have large (full range) or small (satellite or bookshelf) loudspeakers for the center channel, the two front left/right mains, and the surround sound channels.  If you have a subwoofer, you should note the crossover frequency.  Frequencies above the crossover frequency are allowed to pass, while frequencies below the crossover frequency are re-directed to the subwoofer (if present) or to a full-range speaker (if any are present).  Many receivers will have a fixed crossover frequency of 80 Hz (the standard set by the THX specification), while better receivers will allow you to fine tune the crossover frequency to suit your system's performance.

Editor's Note: If you plan to adopt the new high resolution, multi-channel DVD-Audio and Super Audio CD formats, you will also need bass management if you have small bookshelf, satellite, or surround speakers.  When buying a DVD-Audio player or SACD player, look for one that has full bass management functionality, because few receivers offer an appropriate bass management function for these high resolution audio formats.  If your DVD-Audio player or SACD player lacks bass management, and you want a receiver that performs bass management, look for one that performs bass management in the analog domain.  This will avoid additional analog-to-digital and digital-to-analog conversions that would severely degrade the pristine high resolution analog signal coming from the DVD-Audio or SACD player.  Digital domain bass management requires A/D conversion, to get the audio signal into the digital domain, where the digital signal processing techniques are used, then another D/A conversion to get the signal back in analog form for amplification.  Digital domain bass management may be acceptable if the DACs are at least 24-bit/192 kHz.

THX Post-Processing

The more expensive receivers will include THX post-processing, as part of the Home THX certification program.  THX post-processing consists of the following:

  • THX Re-Equalization: THX-certified movie soundtracks are originally mixed and optimized for the acoustic space of commercial movie theaters.  The THX Re-Equalization post-processing function is simply an equalizer preset to Home THX specifications to remove just the right amount of brightness (excessive energy in high frequencies) that sound designers use to compensate for high frequency dissipation in a large movie theater.  In our opinion, this is the most value-added of the four THX post-processing functions listed here.

  • THX Surround Decorrelation: For Dolby Surround soundtracks where the surround channel is mono, THX includes a decorrelation algorithm to make the left and right surround channels slightly different from each other in order to achieve a more natural and enveloping surround sound experience.  This function is not used when the surround channels are discrete (independently encoded) and are truly different as in many Dolby Digital 5.1 and DTS 5.1 soundtracks.

  • THX Timbre Matching: THX recognizes that the same sound coming from different directions will sound differently because of the nature of human hearing, so they attempt to match the timbre (the quality of the sound) of the sound coming from various loudspeaker locations in a typical home theater configuration.  Note, this does not attempt to match the sound produced by different brand or type of loudspeakers.  In fact, this function assumes that you already have a home theater loudspeaker system that already matches in tonal characteristics.  We think this is the second most value-added THX post-processing.

  • THX Subwoofer Crossover: This THX post-processing is similar to the bass management function we discussed above.  Here, THX re-directs all bass frequencies below 80 Hz from the front channels (left, center, and right) to the subwoofer output.  For Dolby Digital and DTS 5.1 sources with a LFE channel, the re-directed bass frequencies are added to those in the LFE channel.  This function works when you have a subwoofer as part of your loudspeaker array.

The Home THX standards for amplification performance will be discussed in a later section, as well as the difference between "THX Ultra" and "THX Select".

THX certification is a nice-to-have feature for mid-priced receivers ($700-$1500),
but is a serious consideration for high-priced receivers (over $1500).

Amplification

You may have heard "more power is better" when it comes to receiver amplification.  Well, we're here to tell you that it's pretty much true (to a certain extent)!  But here's the kicker: there are a few other facts you must know and consider in choosing the amount (and quality) of amplification that you will need.  Amplification is the process where a receiver takes a low voltage analog audio signal (usually a few Volts) and amplifies it to a powerful analog signal with enough current to control and drive the loudspeaker's array of drivers to produce the sound that we hear.  First, we'll talk about the number of channels, then how receiver amplification power is specified and how much power you will need.

Number of Channels

As we mentioned above, the current de facto standard are the 5.1-channel surround sound formats such as Dolby Digital and DTS.  This means 5 channels of full frequency, plus a single ".1" low frequency effects (LFE) channel for an optional subwoofer.  5.1-channel receivers have 5 channels of amplification for the full frequency channels, while the ".1" subwoofer output is not amplified for use with an active subwoofer (one with a built-in power amplifier) or a passive subwoofer in conjunction with a separate amplifier.

The new and emerging surround sound formats are the 6.1-channel extended surround sound formats, with the addition of a full-frequency back surround channel.  Though there is a single audio signal for the back surround, two loudspeakers driven off of that signal is usually recommended for a more continuous soundfield.  So if you are considering the 6.1-channel formats, many mid-priced receivers will have 6 channels of built-in amplification, some with an option to use a separate power amplifier for the second back surround loudspeaker.  The more expensive receivers will have 7 channels of built-in amplification to allow the use of two back surround loudspeakers.  In any case, the ".1" subwoofer output is not amplified.

Amplifier Power Ratings

There are a number of aspects to a receiver's power rating, all of which should be considered carefully:

Continuous (RMS) Power. Amplification power is usually given in units of Watts (just as the wattage of a light bulb is a general indicator of how much light the bulb can emit).  Since music and movie soundtracks can have long loud passages, we are interested in how much power a receiver can continuously put out to drive the loudspeakers during these extended demanding aural passages.  For this reason, we should not be interested in the peak power of a receiver, the amount of power a receiver can deliver for a very brief duration before running out of "steam".  Rather, we are interested in a receiver's continuous power output, which ensures that the receiver will have enough "steam" to drive the loudspeakers during long passages of demanding audio material.  Continuous power is usually expressed in terms of "Watts RMS" (root mean square) or "Watts continuous".  Do not give credence to or compare receivers based on power specifications that say "Watts peak".

Frequency Range. Ideally, our ears can hear sounds as low as 20 Hz (bass frequencies) to as high as 20,000 Hz (treble frequencies).  This full range of audio frequencies should be reproduced by a home theater system.  In doing their part, receivers should be adept at amplifying audio signals in the full range of 20 Hz to 20 kHz in order to maintain a realistic reproduction of music and movie soundtracks.  The frequency range portion of a receiver's power rating is usually given as "20 Hz to 20 kHz", or equivalently "full bandwidth".  Anything less than this range of frequencies is unacceptable.

Channels Driven Simultaneously. Movie soundtracks often have loud passages where all channels (center, left, right, left surround, and right surround) erupt to loud sound levels.  These loud passages are very demanding as all 5-channels are driven hard at the same time.  Better home theater receivers will have power specifications that say "all channels driven simultaneously" for the rated power output.  Those receiver with specifications that don't say "all channels driven simultaneously" are likely to provide the rated power output for only one or two channels driven simultaneously.  Like the continuous power specification, those that lack this capability may run out of "steam" during loud passages where all channels are driven hard.  But this specification is less important between the two.  Only high performance receivers will have "all channels driven simultaneously" in its power rating, so unless you're in the market for a receiver of that caliber, this is something you can forego.

Speaker Impedance. Most loudspeakers have a nominal impedance (or resistance) of 8 ohms.  Some will have a value of 4 ohms, which means that they will draw twice as much current from receivers than those with 8 ohms (assuming all else are equal).  Most receivers have no problems driving loudspeakers with 8 ohms nominal impedance, but only some have enough "juice" to effectively drive the more demanding loudspeakers with 4 ohms nominal impedance.  Most receivers are specified with power output "into 8 ohms".  If you have a loudspeaker with 6 ohms or 4 ohms nominal impedance, look for receivers that specify power output "into 4 ohms".  Those that only specify "into 8 ohms" will still drive 4-ohm or 6-ohm loudspeakers, but its performance will be much less than if they were driving 8-ohm loudspeakers.  Additionally its power output into the 4-ohm loudspeaker will not be known.  If you have 4-ohm loudspeakers, it would be ideal if a receiver's specification give two numbers, one for 8-ohm loudspeaker loads and another for 4-ohm loads.

Editor's Note: A perfect power amplifier can deliver double the power when the loudspeaker impedance is halved.  For example, a high-end power amplifier can deliver "120 Watts into 8 ohms" or "240 Watts into 4 ohms".  But few, if any, receivers can achieve this level of performance.

Total Harmonic Distortion (THD). This is a measure of how "clean" a receiver can amplify audio signals.  If you enjoy music at louder volume levels, you will want to pay extra attention to this part of a receiver's power specification.  Since harmonic distortion is a bad thing, lower numbers for THD are better.  Typical values are 0.05% to 0.08% THD for a "clean" receiver, but any value below 0.1% THD is acceptable.  Don't compare THD values for receivers of different brands too closely since there are some slight variations as to how this number is measured across different manufacturers.  Use it to compare receivers with the same brand, but across brands only a difference of 0.03% THD or greater should be considered noteworthy.

If you want a good home theater experience and your budget is flexible enough,
we strongly recommend choosing a receiver with a power specification that
reads something like "100 Watts RMS into 8 ohms per channel,
20 Hz to 20 kHz, all channels driven simultaneously,
with no more than 0.08% THD".

This kind of specification will ensure that your loudspeakers are getting the power they need to reproduce demanding movie soundtracks and music with the highest possible fidelity.  (We'll talk about how much power you really need in the next section.)

Compared to the two-channel stereo receivers of a decade ago, today's home theater receivers have at least five channels of amplification.  While the digital components of a receiver have significantly increased in computational power at the same time as getting much cheaper, the power amplification components have not benefited from an equal drop in price.  Consequently, to make home theater receivers affordable and price competitive with the two-channel stereo receivers of yesteryear, manufacturers have started to use innovative technologies as well as "cut corners" to meet specific price points.

Specsmanship. To meet certain consumer-friendly price points, equipment manufacturers are practicing what is called specsmanship.  This is a practice where manufacturers dress up or cover certain performance specifications in a manner where a casual, ill-informed consumer is likely to miss out on the not-so-subtle differences.  The three parts of the power amplification subject to specsmanship are: continuous (RMS) power, frequency range, and channels driven simultaneously.  Instead of specifying continuous or RMS power, manufacturers use peak power in the specification for their entry-level receivers.  Instead of specifying power over the full range of audible frequencies, manufacturers specify the power for only one frequency (usually 1,000 Hz or 1 kHz).  And instead of specifying power as "all channels driven simultaneously", manufacturers simply say nothing.  So a power specification with specsmanship reads something like: "100 Watts peak @ 1,000 Hz, 0.10% THD".  In our opinion, the two most onerous practices in specsmanship are in the continuous (RMS) power and frequency range part of the power specification.  It is to our disappointment that the FTC (Federal Trade Commission) has allowed such specsmanship practices for peak power and power specification for a single frequency, without making a concerted effort to educate the consumer.  There's nothing wrong with buying an entry-level receiver from a manufacturer who uses this type of specsmanship, so long as you (the consumer) are aware of the not-so-subtle differences.  Many receivers under $600 are subject to specsmanship, but those that cost more are not necessarily exempt.  And now that you're informed, you can intelligently compare receivers apples-to-apples and know what you're getting.

How Much Amplifier Power Do I Need?

Now that you know how amplification power is rated, the next step is determining how much power you will need.  Surely, more power is better, but most of us live with fixed budgets, so practically speaking, we need to know how much is enough.  The amount of power you need will depend on a number of factors.  The most important factors are your loudspeaker's sensitivity, the size of your room, and how much headroom you want in your system.

Loudspeaker Sensitivity.  A loudspeaker's sensitivity is a measure of how much sound the loudspeaker puts out for a given amount of power input from a receiver.  Usually, it is expressed in terms of decibels (dB) sound pressure level (SPL) per 1 Watt of amplifier power measured at 1 meter from the speaker.  Different loudspeaker designs will have different sensitivities.  Most loudspeakers have sensitivities in the range of 85 to 91 dB SPL/1W/1m.  Frequently, it is understood that sensitivity is measure with 1 Watt of power input at 1 meter, so sensitivity is usually expressed as just "dB".  The higher the number, the more sensitive or the louder the sound output from a loudspeaker given the same power input.  Since sensitivity is measured in decibels, a 3 dB difference in sensitivity means a doubling or halving of amplification power to achieve the same loudness (SPL).  In other words, a loudspeaker with a sensitivity of 87 dB requires twice the amplification power of a loudspeaker with a sensitivity of 90 dB.  A power amplifier delivering 100 Watts of power into the 87 dB loudspeaker produces the same loudness as a power amplifier delivering 50 Watts of power into the 90 dB loudspeaker.  This is why loudspeaker sensitivity is an important consideration when determining the power required from a receiver.

Editor's Note: For an 8-ohm loudspeaker, power input of 1 Watt corresponds to 2.83 Volts.  But some loudspeaker manufacturers specify their 4-ohm loudspeaker's sensitivity with a 2.83 Volt signal, which corresponds to 2 Watts of amplification power.  This gives a false impression that their 4-ohm loudspeaker is more sensitive than it really is.

Size of Your Room. Larger rooms will require more amplification.  As a rule of thumb, use the following table to determine the power amplification of your receiver.  This table assumes that you want your home theater system to be able to play at movie theater reference volume levels.  First, look up your speaker's sensitivity in the first column, then find the size of your home theater room as measured in cubic feet in columns 2-4.  Compute the room size by multiplying the width and length and height of your room in feet.  Then look up the value of the minimum suggested amplification power (expressed in Watts per channel).  (Example: A loudspeaker with a sensitivity of 88 dB in a room that is 2,500 cu. ft. should be driven by a receiver with at least 64 Watts per channel.)  If you find that your power amplification requirements exceed 170 Watts per channel, you may want to consider a system of separates, a pre-amplifier and a power amplifier (that can output more than 170 Watts per channel) instead of an integrated one-unit receiver.  The most powerful receiver (Denon AVR-5803) produces 170 Watts per channel into 8 ohms.

 
Guideline for Minimum Receiver Power Amplification

(minimum recommended power, in Watts per channel)
(v1.0)

 Loudspeaker Sensitivity
[dB]
Room Size
Small
(less than 2,000 cu. ft.)
Medium
(between 2,000 and 3,000 cu. ft.)
Large
(larger than 3,000 cu. ft.)
85 96 128 192
86 76 101 152
87 60 81 121
88 48 64 96
89 38 51 76
90 30 40 61
91 24 32 48
92 19 25 38

 
Note 1: This table is based on the Home THX Program's recommendation of achieving a peak sound pressure level (SPL) of 105 dB, which can be achieved with 64 Watts into a loudspeaker sensitivity of 88 dB.  Typical listening levels are usually in the range of 80 to 90 dB SPL.
Note 2: If your array of loudspeakers vary in terms of sensitivity, use the lowest sensitivity number from the front, center, or right loudspeakers.  The sensitivity of the surround sound loudspeakers are secondary when it comes to figuring the minimum power amplification.

Headroom. Keep in mind that the table above indicates the minimum amplification power you'll need.  Usually, you will want more power in case you move your home theater to a larger room or simply to have what is called headroom.  Headroom is the power reserve that is above and beyond what you normally need in steady-state that allows your system to respond to very brief loud passages.  This is particularly important if you're a big fan of action movies with lots of explosions.  So yes, buy the most powerful receiver you can afford, but keep in mind how amplifier power ratings are specified.

THX Certification: Comes in Two Sizes

For home theater receivers, the Home THX program covers certain post-processing functions (discussed in a previous section) and power amplification requirements.  The post-processing functions make sure that the soundtrack mixed for a commercial movie theater is compensated for proper reproduction in a home theater environment.  The power amplification specifications make sure that when a THX-certified receiver is used with THX-certified loudspeakers, the system produces sound quality that meets THX standards.  And that means an awesome home theater experience.  For receiver power amplification (and loudspeakers too for that matter), there are two basic levels of THX certification.  THX Select certification is for components that are certified to perform in a mid-sized home theater environment of up to 2,000 cubic feet.  (The volume of a room, expressed in cubic feet, is computed by multiplying the length by the width by the height of the room.  For example, a room that is 18 feet wide by 14 feet wide by 9 feet high, has a volume of 18 x 14 x 9 = 2,268 cubic feet.)  The more stringent THX Ultra certification (which is equivalent to the original, plain "THX" certification) is given to components that meet the THX performance standards for larger home theater environments of up to 3,000 cubic feet.  Theoretically, if you have a home theater environment that is 2,000 cubic feet or less, THX Select certified receivers and loudspeakers should deliver about the same presentation standards as the higher-end THX Ultra certified components.  Both THX Ultra and THX Select levels of certification call for the same post-processing functions.

"THX Select" certification                 "THX Ultra" certification
THX Select                      THX Ultra

THX Ultra2, more of a good thing?  In September 2001, THX updated the Home THX program to the THX Ultra2 specifications.  In short, THX refined the THX post-processing functions, refined the receiver performance specifications, and added the THX Ultra2 music surround sound mode, where a 7.1-channel surround sound experience can be derived from music and movie program materials originally recorded in stereo or encoded as Dolby Surround Pro-Logic in 2-channel.  Right now, THX Ultra2 certification is only available for high-end receivers.

Do you need to buy a home theater receiver with THX certification?  Certainly not.  While a THX-certified receiver paired with a THX-certified loudspeaker system can guarantee excellent results, you can achieve the same (or better) performance with components that are not THX-certified.  Certain receiver and loudspeaker system manufacturers produce excellent products that perform very well, but they have chosen not to seek THX certification and pay the associated Home THX program licensing fees.  Obviously, these costs would be passed onto the consumer as higher prices.  If you want to put together a home theater system in a fool-proof manner that guarantees excellent performance and you don't mind paying a little extra for THX-certified components and loudspeaker systems, by all means look for the THX Select, THX Ultra, or THX Ultra2 logos.

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In This Buying Guide:

 

> Introduction

> What is a Receiver and What Does It Do?

> Surround Sound Decoding

> Audio Signal Processing

> Amplification

> THX Certification

> Switching

> AM/FM Stereo Tuner

> User Interface

> Construction & Build Quality

> Upgradeability & "Future Proofing"

> Alternatives to a Receiver

> Comparing Receivers

> Auditioning Receivers

> Where to Buy & Find the Best Deals

 


DVD & Blu-ray Release Dates

 

> August 2010

> September 2010

> October 2010

> November 2010

> December 2010

> January 2011

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