Q&A # 98 - January 12, 1999

Staff

Q Well, I just read your rave review of the very expensive and esoteric Nordost Quattro Fil Cables . . . $1600 per meter pair. Now I am not trying to bait an argument or start a sensless polemic on whether or not wire = wire. Oddly enough I too own some nice Nordost as well as some Kimber (copper, silver streak, and KCAG) and I have some RSQ Reference stuff. Presently my Home theater is wired with TRIBUTARIES and my Stereo (tube) is Nordost. But I have bought the COMPARATOR from Wire World and much to my chagrin, could not hear much difference when I asked someone to do the switching for me. Do you have any opinions on ABX testing? I always thought my ears were discriminating and my systems had good resolution. Certainly the pedigree of the components were good. And I have spent an equal amount of $$ in ASC and RPG room treatments through the assistance of a skilled acoustician as I have for Speakers and Cables. The room has by far yielded the greatest results, simply amazing is the change. Especially in RT-60 times. So after buying the Comparator, I am wondering about some of my past wire purchases as well as some of my past electronic parts upgrades and mods.

A I am a firm believer in scientific testing, which includes single blind, double blind, and ABX. It's not always easy to do, but it is the best way to prove a difference exists. However, one cannot prove that a difference does not exist, only that it does exist, and even with this, one is dealing with a statistical chance that the proof is mistaken. The problem with any comparator device is that you have the jacks, internal conductors, and switch contacts in the signal path, so I am looking for some other way. When I listened to the Quattro Fil and heard a difference, I immediately thought I was imagining it, but when my mother in law subsequently made a reference to the sound quality, without my even mentioning that I had changed anything from the last time she was here, I knew there was something happening. Other studies have shown that different cables do indeed pass electrical signals differently, but we are still looking for clear proof that these differences are audible. In any case, perfectly good cables are available for reasonable prices, and the fact that many people cannot hear differences between cables means that whatever differences that do exist, if there are any audible ones, are very subtle. I use modest cable in my home theater system and am very happy with it.

Q When adjusting speaker levels, should I start at the maximum (+10 dB in my receiver) and leave the lower volume speaker at +10 dB, then reduce the levels of the others until they sound even, or start at 0 dB and raise the lower sounding speakers until they sound even?

A It would not make any difference, except that starting out with the system at full volume will not be good for your system or your ears. Pick a comfortable volume, look at the dB setting, then match your various speakers.

Q Does the Toshiba 3108, like a lot of other DVD players, downsample the 96/24 signal to 44.1 kHz? If so, is there a way I can avail myself of the full sound potential when playing 96/24 DADs?

A The current crop of DVD players will output decoded 96/24 as stereo analog through the stereo analog RCA jacks on the rear. They downconvert it to 48 kHz - 16 bit, through the digital output jack. So, in order to enjoy the 96/24 discs properly, just use the stereo analog output jacks on the DVD player instead of the digital one.

Q I'm very interested in learning more about all aspects of home theater and hi-fi. I grew up with, what I have now learned through reading your magazine, was a SE triode amp that my father used to entertain the neighborhood with in the 60s back in Belize (then British Honduras). I still have fond memories of the warm sound that the amp used to produce, but lost some interest in hi-fi when I became of age and everything became solid state. I had no idea that there were other people like me who actually preferred the sound of tube amps. I fully intend to build one but have no technical background in the field so I am reading everything I can get my hands on.

I would like you to include articles and tips for home theater and hi-fi enthusiasts who are in the process of building their homes. My wife and I will be building one in 1999, and it would be nice to prepare the rooms as much as possible while the house is actually going up. I suspect there should be some advantages in doing so. Include such topics as acoustics, lighting, wiring, building material outlets for audiophiles, etc.

Thanks in advance. I really am having a ball with your magazine. If there was a small price tag I would be more than willing to pay it.

A We have an SE Triode DIY project in preparation now. We are also experimenting with speakers that are designed for small output tube amplifiers, for incorporation into a DIY project. They won't necessarily be high sensitivity, but will have a very unusual design characteristic I think all tube enthusiasts will enjoy.

Q The following two lines are directly from a spec sheet on a subwoofer:

High Pass Passive 80/100 Hz, 6 dB/octave slope
Low Pass Active-Adj., 40 to 120 Hz

What I want to know is:

(1) What exactly do these mean?

(2) What do they allow you to do in terms of how you can manipulate the sound distribution from your speaker system?

(3) Do these represent the optimal set of capabilities for a sub to have?

A High pass means that the signal is being passed above the frequency specified (in this case, choice of 80 Hz or 100 Hz) and attenuated below that frequency. Passive means that the crossover components are between the power amplifier and the speaker. The slope of 6 dB/octave means that for each octave below 80 Hz, if that frequency choice was selected, the signal strength decreases by 6 dB. So, at 40 Hz, it would be 6 dB less in loudness than it was at 80 Hz. At 20 Hz, it would be 6 dB less than at 40 Hz. Low pass means that, at the crossover frequency specified, the signal is passed below that frequency and attenuated above that frequency. Active means that the crossover is placed between the preamplifier and power amplifier. Adjustable (Adj.) means a continuous adjustment range between 40 Hz and 120 Hz rather than just a choice of 40 Hz or 120 Hz. All modern subs have these basic capabilities. You should mostly be concerned about the ability of the subwoofer to move lots of air. This means a big driver and/or large excursion capability, and a big amplifier.

Q I have a Yamaha RX-V990 receiver and have recently installed a Panasonic A310 DVD player. I noticed that the 990, advertised as "Dolby Digital Ready", only has 5 inputs for the A-310 5.1 channel output, instead of the 6 that I expected. The 990 presumably derives the .1 channel signal from the others and directs it to my subwoofer. I notice that your reviewer likes the 990 very much (as stated in the review of the RX-V992), but I wonder if I am missing something in the low frequency sound of DVDs with this system. Do you think that I would have better low frequency effects with a true 6 channel system, or does the 990 manage to extract all of the LFE from the other channels? (By the way, the DVD audio sounds great compared to DPL, but I haven't heard any other DD systems for comparison.)

A The RX-V990 is one of the best receivers Yamaha ever made, but it does lack the sixth pass through for the LFE from outboard DD decoders. The latest receivers have all six, but earlier receivers don't. What I did was to connect the LFE output from the DD decoder to one of the line-level inputs on the subwoofer, and the subwoofer output of the receiver to the other line-level input on the subwoofer. What this meant, of course, was that when using the decoder, I would get not only low frequencies from the LFE channel, but low frequencies being extracted from the other channels in the receiver. But, I never experienced a problem doing it this way, and I wanted to make sure I was getting everything from the LFE as it came out of the DD decoder. Also, there are a few DVD movies with 5.0 sound rather than 5.1, meaning that that LFE channel is vacant. The sub out from the receiver would then be the only source of low frequencies to the subwoofer in this configuration (outboard decoder feeding five RCA jacks on the 990).

Q I am looking to upgrade my speakers, and am considering Martin Logan Aerius or SLT. My living room is large, with an open floor plan. Will the Logans do well in a space like this, or should I use a box speaker? Also, do you consider these speakers to have a laid back sound?

A Dipolar speakers (planar magnetic, ribbon, and electrostatic) do very well in an open space. In fact, where they run into problems is when they are too close to walls. I would consider the MLs to be clean, rather than laid back. Occasionally, this gives the impression of laid back, because metal tweeters in some box speakers are a little edgy, by comparison.

Q 1) When making speaker cables for the Left Front, Center, Right Front, Right Rear, Left Rear, and Subwoofer, what lengths of wire should be used? In other words, should all of the runs be the same length, or just the R/L fronts one length (i.e., 20 feet each) and the R/L rears another length (i.e., 30 feet each)?

2) What gauge wire should be used?

A I keep the front left/center/right speaker cables the same length, and the rear left/right speaker cables the same length. Don't use anything smaller than 18 gauge speaker wire. I have used 16 gauge routinely when wiring friends' home theaters, and the speakers are being driven by mass market receivers.

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