Q I have been reading the major A/V publications for the past four years. As a current active consumer looking to upgrade my A/V equipment, I have become quite dismayed with the disparity in reviews. I am beginning to question the authenticity in what is being written. For example, very recently three different publications did reviews on a Sony ES line Dolby Digital receiver. One review suggested that it was basically not worth purchasing, the second suggested that although it's a fine performer others surpass, and the third reviewer stated that it was the best A/V receiver he had ever heard on both music and movies. What gives? These are all, what I hope, reputable journals. The same thing occured with the Carver 705x amp. It's too "bright", "all around solid performer", "thin in the upper octaves", "good for movies", or "one of the best sounding amps in the under $1,500 group." I have seen this over and over. Could you please offer some kind of rational explanation?

A The problem stems from the fact that our brains are not oscilloscopes or voltmeters, and what we hear is different than what we perceive. Perception depends on our past experiences and what we consider to be pleasurable. Age is not as important as one might think. During one of our tests, a seventy five year old woman listened to a couple of different amplifiers we had in the lab, and was able not only to distinguish between the two, but told me which one sounded better. In any case, reviews of audio equipment and A/V equipment are factors of what we feel to sound or look best. I have seen reviews that stated, "the listening belied the test equipment measurements", meaning that they really liked the sound in spite of high harmonic distortion measured on the bench. Although graphs and charts are helpful, the final analysis is how we perceive the performance, and this is subjective no matter what anyone says to the contrary. Thus, the different opinions on the equipment you mentioned. I feel that there are some basic concerns that readers want to know about: Does it look good?; Does it sound good?; Is it designed well?; and Is it worth the price? Every one of these concerns is based on subjectivity, and most magazines answer these questions in one way or another even if they don't break the analysis down to its parts. So, regardless of the approach the reviewer takes, the answers are very likely to be different, not only among various magazines, but among reviewers in the same magazine. What I do is find writers who seem to be on the same wavelength as I am about equipment that I have experience with, and then I pay attention to those reviewers' opinions in future articles.

Q My Harman Kardon power amplifier is rated at 100 Watts into 8 ohms for all 5 channels driven, and 150 Watts for 4 ohms. It also has a high current rating (HCC) of 80 amps. For 100 Watts into 8 ohms, the current required is 3.5 amps. For 150 Watts into 8 ohms the current is 6.1 amps. These are steady state currents. I assume the HCC of 80 amps refers to a transient or surge current capability to meet a dynamic load impedance that has suddenly dropped. Is this right and if so for how long can the amp deliver 80 amps!?

A The high current specification is basically what the output transistors are rated at. The power supply would not handle this for very long, perhaps a millisecond, but it is unlikely you would ever see a demand like this. Even with 4 Ohm loads and full output (150 watt/channel) into all five channels, this amounts to about 30 amps. If this were drawn for a second or two, the circuit breaker in your listening room would likely trip. The rail voltage is another limiting factor. No matter what the dynamics of the music, once the rail voltage is reached, that's it. If the power supply is not big enough, the rail voltage drops when the load is high. We are all up to our armpits in specifications. Those come from the marketing department, not the engineering department. When I shop for equipment, the last thing I ask to see is the spec sheet. First and foremost is how it performs to my eyes and ears. I crank it up, I crank it down (video color, brightness, sharpness, audio clarity, detail, harshness, mushiness), I lift it, look behind it, feel for sharp corners (an indication of manufacturing care), look at the connectors, the feet, and a few other things, and then, if I am in the mood to buy, I ask to see the specs.

Q Can an A/V receiver's power rating in RMS be greater than the speaker's power handling capability? If yes, what would the ratio be? Some vendors told me that it would be alright if the volume is kept low. Is it true?

2. Some manufacturers of A/V receivers and speakers advertise their product by specifying the power capability at 6 or 4 Ohms, but I noted that surround systems are always rated at 8 Ohms. Does it mean that if a receiver/speaker is capable of handling 100W of power at 4 Ohms, it can actually handle 50W at 8 Ohms?

3. Is it worthwhile investing in an amplifier with Lucasfilm Cinema Re-EQ and Timbre Match?

4. What would be the effect of running a THX certified amplifier with ordinary speakers?

A It is always best to get as much power as you can afford. This allows for greater dynamics during short term peaks (gun shots, kettle drums, thunder, twang of steel guitar). Most speakers can handle short term peaks that are pretty high, as long as the power is clean (not clipping). Typical good speakers for home theater and general audio use are rated at about 100 watts or so. An amplifier rated at 400 watts per channel would not pose a problem as long as you did not turn the volume up high on a continual basis. If you were listening at 20 watts average, and along came a transient peak that demanded 200 watts, it is likely that the speaker would handle it just fine. Damage occurs more often when there is not enough power, because a clipped signal is very hard on the speaker drivers.

The biggest concern is the quality of the amplifier. If you have 4 Ohm speakers, it is really important to get a good amplifier that can deliver clean power at 4 Ohms, which is not generally the case with many receivers. If you are using the power amplifiers in a receiver, try to stay with 8 Ohm speakers.

You might see THX re-eq in the receiver or processor, but not power amplifiers. THX certification in amplifiers means several things. One is that there is equal power in all channels. Also, it has to be at least 100 watts per channel, and have a certain amount of "overhead" power available for transient peaks. An amplifier can meet THX specs without being certified. It depends on whether the manufacturer wants to pay for the right to state it is certified, assuming it will meet the tests at THX. It is a marketing thing, and generally means it meets standards for home theater applications that THX feels should be met. I like the certification program, because it is an extra stamp of quality approval.

Ordinary speakers can meet THX specs without being certified too. Using a THX certified amplifier with non-THX certified speakers would not mean anything in particular.

Q My current system consists of a Yamaha 2092 receiver, a pair of Sonus Faber Concertinos, Onkyo Integra CD player C606, and NHT SW2Pi subwoofer. I think I'm gonna buy another pair of the Concertinos and the Sonus Faber Center (Solo) for the home theater set up in a near future. But right now, I focus more on the stereo music. I notice that the amplifiers in my Yamaha receiver are not good (powerful) enough, although rated at 100w x 5, to drive my Concertinos. That is why I'd like to add either a more decent stereo amp or 3-ch amp for music and video to my system. One of the sale persons told me that the addition of an amp would NOT improve the sound that much because the preamp in the Yamaha 2092 sucked!!!. My questions are: (1) Is the sale person correct? If so, could I use the Yamaha's processor coupled with the integrated amp? For example, use Classe CAP150 (or CAP80) as a preamp and amp for the front main channels L and R, and the Yamaha as the processor for Dolby Pro Logic and DD and its 3 amps for center and surround. (2) What amp is the perfect match for the Concertinos? I'm thinking about: B&K AV5000, Bryston 3B or 5B, Classe CAV100 (which is my favourite), Denon POA8200 or 8300, NAD or Adcom (125watts x 2).

A Although the 2092 preamp section doesn't "suck", it certainly will not do the Conertinos justice. I would suggest getting a five channel power amplifier, such as Classe, rather than a two or three channel one, and using the pre-outs of the 2092 to drive it. Also, you should get a better two channel preamp just to drive the front channels, and use the tape loop (or processor loop if it has one) to drive the front two channels when in home theater mode. When the tape loop is open, the CD player will go through the two channel preamp directly to the power amplifier for two-channel stero. When the tape loop is closed, the two channel analog will go from the preamp to the receiver, get decoded, and the front left right Pro Logic will go back to the preamp and out to the power amplifier. The pre-outs of the 2092 for the center and rear left/right are connected to the power amplifier, while the outputs of the new preamp are connected to the front left/right of the power amplifier for this to work properly.

Q Will the current DVD players be able to play the new DVDs that will hold 17+ gigs of info (and how long will it be until they come out)? Besides the aforementioned reason, I am holding off getting a player until they can play both DTS and DD. Your thoughts please...Thanks!

A DVDs have always been capable of storing 17 GB, and even the first DVD players could play all the data, but so far, movies have not required using all of the space. All DVD players have to be able to play dual layers, but the first movies on DVD did not make use of both layers. Some recent movies do have dual layers, and they work beautifully even on the first generation DVD players. DTS is another matter. A few DVD players with "DTS Digital Out" have been announced, including the Yamaha (see press release this week in Secrets). They are scheduled to be available in April, 1998. They require an external DTS decoder. Probably by late 1998, early 1999, we will see lots of mass market receivers that decode Pro Logic, DD, and DTS. Because of all the controversy over DTS in DVD players, we are going to wait until we have had the chance to test a production model DTS DVD player with older DTS decoders before we make any recommendations to the readership. The problem with first generation DVD players is that they did not have the ability to recognize the DTS "flag" on the disc which tells the player that there is a DTS track on the DVD and to output it accordingly. So, it means that all of us early adopters will have to buy new DVD players. It's very frustrating.

Q I have the Carver ALIII+ Speakers and I am absolutely crazy about them! At first I had a Carver TFM-55x amp powering both speakers and quickly realized this wasn't near enough. I now have two Carver A-760x stereo amps, one driving the ribbons and one driving the woofers. The speakers have come to life! Unreal! I am writing you to get your thoughts on these speakers, on their own merit, and in comparison to the Carver ribbon speakers of the past. I am just curious...I have looked high and low for reviews of these speakers and have found none! Also, based on a previous question I saw on your site, I have and highly recommend the Magnepan MGCC Center Channel Speaker with the Carvers up front. They make a wonderful match and the Maggie Center is the best I have heard to date!

A The original Carver Platinum Mark IV speakers used a 60" ribbon and four 12" cone woofers in each panel, while the Carver Silver Mark IV speakers had a 48" ribbon and three 12" cone woofers. Both designs were completely dipolar, including the woofers which were open at the back. Although they were great speakers, they were large and cumbersome. The ALIIIs use the same 48" ribbon as in the Silvers, but have a single enclosed ported cone woofer instead of a series of dipolar woofers. Instead of a wide panel with the ribbon on one side and the woofers on the other, the ribbon of the ALIII is above the woofer. This makes the ALIII more manageable but maintains much of the original sound of the Silvers. They are, indeed, very nice speakers, and the use of the Magnepan as a center channel is a good idea. Dipolar ribbons are awesome in home theater applications, but they are difficult to place and are still pretty big. Also, not everybody likes the dipolar sound.

Q While I view certain products in high end audio with a fair amount of skepticism, i.e., esoteric cables, line conditioners, and vibration control products, it does seem to me that vibration control units would have a clear impact on one application. If one were placing one's speakers on top of something other than a pair of quality speaker stands (like on a piece of furniture), a vibration control product might suffice as a substitute for the vibration isolation that a pair of good speaker stands would produce. Is this correct?

A Yes. However, there are several functions of a speaker stand. One is to isolate (decouple) the speaker from the floor, so that vibrations of the floor will not vibrate the speaker, and vibrations of the speaker will not vibrate the floor. Secondly, the speaker stand keeps the speaker away from surfaces that can reflect the sound emerging from the drivers (which interact with the driver sound to produce diffraction). The best speaker stands are those that have a shelf that is the same size as the end of the speaker resting on it (to minimize reflections from the shelf surface) and a small vertical profile supporting the shelf from the floor. Third, the stand puts the speaker at the right height with respect to your ears. Putting small speakers on furniture, end tables for example, will work alright, but put them at the front of the table so that there is a minimum of horizontal table in front of the speaker with respect to the listening position. Also, don't stack books or magazines under the table, since they would serve as reflective devices. To isolate the speaker from the wood table, you can use simple felt furniture pads. They have adhesive on one side, so I stick two of them face to face and put one set of pads underneath each of the four corners of the speaker. Then I rap my knuckles on the top of the speaker. If the isolation is sufficient, the table will not make any noise (try it first without any pads so you will hear the sound of the table that you are trying to eliminate).

Q I have a Yamaha DSP-A3090 which has a mono sub out and a right and left sub out. I currently have an M&K sub hooked up using the right/left sub out on the Yamaha directly to the right/left input on the sub. I am thinking of buying another M&K sub. Which would be the best way to hook them both up? Use a "y" adapter out of the left for one and repeat for the right output for the second sub or use a "y" adapter out of the mono output and send the left to one sub and the right to the other? Thanks for the filter settings I read on previous Q&A. I always wondered where to set my M&K's crossover with my Yamaha's 90 Hz high pass filter.

A The right/left sub outputs on the 3090 are stero sub outputs, I believe. Therefore just use one coax cable from the left sub out to the left sub, and another coax cable from the right sub out to the right sub. Even though the two subs will have slightly different signals, placement is still an issue. You will probably have to adjust the phase on one or both of them.

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