Choosing a home theater receiver can be a daunting task. Receivers have more specifications than any other part, and adding HDTV to the mix just makes it worse. In the old days, manufacturers would compete to build the best unit, and you could hear the improvement. Today, receiver technology is mature, and so manufacturers have no problem building a suitable component. The bigger risk is that they cut corners to save a few dollars. Here are a few specifications that matter the most:

Power
Manufacturers know that power is the first spec consumers check. Thus, there is more muddling of power specs than any other. A proper power specification reads something like “100 Watts per Channel (W/Ch.) into 8 ohms from 20Hz to 20KHz with no more than 0.1% THD” (where THD stands for Total Harmonic Distortion). A power specification that does not contain all five numbers is meaningless. As receivers are turned up to maximum volume, their distortion can increase exponentially. A 100W/Ch. receiver with either a high (> 0.1%) or non-existent THD spec could really be a useful 50W/Ch. receiver that can be turned up higher if you don’t mind it sounding bad.  Also, power is relative to the “load” of the speaker. 100W/Ch. into 8 ohms could be specified as 133W into 6 ohms, or even 200W/Ch. into 4 ohms. So with no load specification, you can’t do any comparison, and power values measured into different loads must be adjusted to be meaningful. (Note: Using a smaller load than specified for a receiver can damage it.) 

Finally, what good is a specification that’s valid across only a small part of the audio spectrum? You want your receiver to “obey” its specifications for all the sounds that you hear.  Thus, the frequency range must be part of any useful specification. 20Hz to 20KHz is considered the normal range for hearing, but specs between 25Hz and 18KHz are probably fine if all the other numbers are good. Bottom line: A receiver that doesn’t have all five numbers clearly specified is hiding something, and you should probably look elsewhere. Onkyo is one good manufacturer who does their power specifications properly. 

How Much Power?
Another common question is “How much power do I need?” The usual answer is “less than you think.” Most of the time, your system is putting out only a small amount of its rated power. The maximum value is used only for peaks (but still, you don’t want the peaks to sound distorted). Correctly specified, 100W/Ch. can be sufficient for most small-to-medium size home theaters, and surround channels require less power than the front three. 

Don’t obsess about small differences in power between units. Because we hear logarithmically, the smallest different in volume that is noticeable to the ear is produced by a doubling of power. Thus, the differences between, for example, a 90W/Ch., 100W/Ch., or 110W/Ch. receiver are not noticeable. 

Still, it’s always a good idea not to skimp on power too much. If your receiver is so under-powered that you’re frequently turning it up near maximum volume, you run the risk that it will “clip,” putting out a severely distorted signals that can damage your speakers. 

Input/Output
You should examine your other video source equipment to determine the highest quality output format for each one. S-Video (round, multi-pin connector), is significantly better than composite video (single RCA connection), and component video (three RCA connectors), is a little better than S-Video. The best format is HDMI, which is an all-digital format used for high-definition video. You should make sure that the receiver you choose has sufficient inputs in your best available formats, as well as a few HDMI inputs for future upgrades. 

Note that the content carried on HDMI cables is encrypted using a method called HDCP. It’s important to check whether the receiver functions with “HDCP passthru” or “HDCP repeater” capability. An “HDCP passthru” device passes the complete encrypted signal through untouched, but a “repeater” will decrypt the incoming signal and re-encrypt it on output. This allows the receiver to tap off the audio so that it can send it through your home theater speakers.  Without the “repeater” feature, you need to run another set of audio cables from your TV (or set top box, dvd player etc.) back to your receiver to drive your the audio out to your speakers. 

THX
THX certification means that your system meets the minimum standards that George Lucas (creator of Star Wars and the THX format) feels are necessary for you to properly enjoy his movies. While this standard is important, many less expensive receivers, if they meet the other specifications mentioned here, will also give you a thoroughly enjoyable listening experience. 

There are certainly other specifications to consider, including processing modes, tuner sensitivity, video conversion capabilities, iPod, XM, Sirius, and general Internet readiness, and multi-zones. But regardless of your specific needs, you should start with the basics described here. Check out some models in our slideshow and happy hunting!