Q&A # 117 - May 25, 1999

Staff

Q I have a curious question for you regarding the widescreen format. I have a decent home theater set up and I am really enjoying the qualities of both sound and picture with my set. But there seem to be quite a bit of variations in the "size" of the picture from one movie to another. That is, some have large black bars on top and bottom, while other have smaller ones. Is this due to the variations from one producer to another, i.e. WB and FOX? Or is it due to the "Reformatting" work? Another question is: I have a Yami 795 and as far as I know it is reported that DD has equal signal outputs or bandwidth to all channels, but most of the time the sound is fuller and louder in the front speakers, despite full range speakers in front and rear. I have tried to adjust the front speakers (L & R) to -10 dB (negative 10 dB) and turn up the volume (the center is quite loud), but the sound effects are still fuller in the front. Thus, is DD truly equal in all channels? If it is the case, what can I do to "equalize" the sound to make the rears "fuller"? (I don't want to have to use an outboard equalizer at this time). I would appreciate your suggestions.

A Although films in the US have settled down to either 1.85:1 or 2.35:1, the presentations on the home versions vary. This has to do with how the director wants them to be seen at home. Currently, they come pretty close to what they were at the movie theater, but there is still some variation. Because so many people dislike widescreen, some directors compromise a bit by cropping less at the top and bottom if the movie was shot with spherical lenses (as opposed to anamorphic lenses), or by cropping a bit from the sides, if the film was shot anamorphically, which produces the same effect on the TV (smaller blank areas at the top and bottom). Although 1.85:1 movies are almost entirely made with spherical lenses, 2.35:1 movies are split between being filmed with spherical lenses and anamorphic lenses. Sometimes the spherical ones are called "Super 35". This let the director show the movie at 2.35:1 at the theater, and then crop less at the top and bottom, but a little more at the sides, and show the movie at 4:3 (full TV screen) for the home version. Now that widescreen is becoming more acceptable, even the Super 35 movies are being presented at 2.35:1 in most of the home versions too, with a few DVDs having the full screen version on the other side of the disc.

DD and DTS 5.1 have full spectrum capability in all channels, and the sound in the rear seems to have full range, but it is still used mostly for sound effects, which provide ambience. The result is that the rear is usually much softer than the front left/center/right. I like more sound in the rear too, so I just crank the rear channels up somewhat. I also like a little more in the front left/right, as most of the sound comes from the center channel with movies. Since there is usually no separate volume control for the front left/right separate from the other channels, I have to turn the volume of the center and rears down, to get the balance I want. But, in any case, just remember that it is not a problem with DD or DTS. It is just the modest use of rear channel effects that is causing that sense of an inadequate feeling of being truly enveloped with sound.

Q I heard (if I am not mistaken here) that one of the best possible connections to blend your main speakers with a powered subwoofer is to use pre-out jacks for Front L and R of a receiver to connect it with a subwoofer, and then use the crossover of subwoofer to send the higher part of frequencies back to the main-ins of the receiver. In this respect, I have a question about the Denon 2700: it has pre-out jacks for the main speakers, but seemingly no main-in jacks. But it has a set of 6 channel inputs for an outboard decoder instead. Can these somehow be used to hook up a subwoofer in the above-described fashion or some other way?

A The main-in jacks connect to the power amplifiers, while the 5.1 input jacks go through the preamplifier and then to the power amplifiers. If you connected the front left/right pre-out jacks to the front left/right jacks on the 5.1 inputs, this would be connecting the output back to the input, and you would get oscillation. You could run the front left/right pre-outs to the subwoofer, and the sub's high-pass line level outputs to the rear left/right 5.1 input jacks, but that would cost you the rear left/right channels, since you could not connect the rear left/right outputs of your DD/DTS decoder to those inputs at the same time. So, I would suggest just using the front left/right pre-outs to your subwoofer, and either getting an outboard two-channel power amplifer to drive the high-pass frequencies out of the subwoofer, or not using the high-pass out at all.

Q I have been a NAD customer for 12+ years and enjoyed their products (hours of listening enjoyment without fatigue). I like basic passive surround systems and have used a Dynaco QD-1 extensively (have updated to the series II which has a printed circuit board instead of the military-like hard wiring everywhere and I feel that the reproduction is better). Anyway, I have been thinking about upgrading the amp and preamp. I currently have a NAD 1155 pre and a NAD 2200PE amp with PSB Golds (front) and PSB Ambient IIs (rear). I have narrowed it down to staying with NAD (liked your articles on the 208THX and the 218THX) or going with the lower offerings from Conrad-Johnson, i.e., PV10A (tube) and the MF 2200 (MOSFET). I asked CJ about their recommendations with my setup, and they suggested the MF 2250 (bipolar output instead of MOSFET). This has confused me somewhat. I have been reading about the wonderful combination of tube preamps and solid-state amps and have auditioned the PV10 with a MF 2100 and thought that they sounded extremely good (at least good enough to make me want to change). I had figured that going to CJ and a more tube-like setup (MOSFETs instead of bipolars) would be the way to go since I like good recorded music instead of movies and home theater. Therefore, NAD has been good to me and I highly recommend their products. Conrad-Johnson seems to be high-end equipment. Is the low-end of CJ that much better than the high-end of NAD (considering $1000 difference)? Is the MF 2250 a better amp than the MF 2200 or is CJ changing to meet the home theater needs by using bipolar in the output phase to enhance transients needed for chase scenes, star wars, and thunder?

A The combination of a tube preamplifier and MOSFET power amplifier is one of my favorites. I think as we move into an era with high sampling rate CDs (DVD Audio), such as Pioneer's 24/192 and Sony/Philips' SACD, we may see less of a need to worry about the smoothness of tubes, vs. MOSFETs, vs. bipolar transistors. However, that is a year or so away. In the meantime, and with our huge collections of 16/44.1 CDs, smoothness is an issue. MOSFET amplifiers are not easy to design. A good one needs lots of output devices because as they get warm, they conduct less current. As a result, if the amplifier does not have many MOSFETs, the sound will turn mushy as the amplifier gets hot during loud music playing. You might find a bipolar transistor power amplifier that outputs 200 watts per channel, based on perhaps six output transistors per channel (when bipolars get warmer, they conduct more current), while a MOSFET power amplifier might have twelve or sixteen MOSFETs in the output stage to produce those 200 watts. As a result, MOSFET amplifiers are expensive to build. They can be plenty fast though, depending on the design. Price is not the issue here, but rather, your sound preferences. Both NAD and CJ make very good products in the high-performance categories. NAD has a new version of the 208THX, with a different model number and silver finish chassis, that appears to be excellent (we are waiting to get one). It is rated at 200 watts per channel, with plenty of output MOSFETs, so you definitely should audition that one.

Q I have a Kenwood KR-V990D and a Sony DVD DVP-C600D. My question is can I hook the digital output jack of my DVD player to the laserdisc RF digital input on my receiver? And will the AC-3 Pro Logic work?

A The AC-3 RF input on receivers is only for use with the AC-3 RF output on laserdisc players. The RF input is expecting an undemodulated analog RF signal carrying the DD bitstream, rather than the digital bitstream itself. However, if your receiver has the AC-3 RF input, it most likely has a digital input for use with your DVD player, so use that input instead. AC-3 and Pro Logic are two different things. AC-3 (Dolby Digital or DD) is digital 5.1 surround sound, with full spectrum sound in all channels, except the 0.1 channel for the subwoofer. Pro Logic is a decoding technique for use with two channel analog stereo, and it decodes the two channels into four: Front left/right, Center, and Rear. Both AC-3 and Pro Logic are Dolby technologies, while DTS (also a 5.1 digital surround sound) is from Digital Theater Systems.

Q I want to wire my house audio for two sets of the seven channels output from my Yamaha DSP-A1. I was told that it would be better if I use another receiver to drive the extra sets of speakers. Is that a good idea, or will the A1 drive all the speakers?

Currently I have receiver preout to a tuner because the A1 doesn't have one built-in. Why is it that I have to turn the volume up on the receiver? I thought pre-outs are not controlled by the volume knob on the receiver?

A Your DSP-A1 can be used to drive both sets of speakers as long as you don't have both sets connected at the same time. Use a speaker selector so that you can operate one set or the other independently. Otherwise, get a multi-channel power amplifier to drive one set, and use the power amplifiers in the DSP-A1 to drive the other set. Pre-outs are affected by the volume control setting. Main-ins are not, and neither are the record-out jacks. If you have a volume control on your tuner, then use the record-out jacks from your receiver, assuming you don't have a cassette recorder in the system.

Q My home theater is a small room, only 10 feet wide, 13 long, and 8 high. I am running a Boston Acoustics THX speaker system, Series 1, Rotel power amp, and Lexicon THX decoder. I am having a problem getting a good depth of image. The left half of the room has drapes covering the window , the right side does not , and the back wall has nothing on it as well. The couch is only about 1.5 feet from the back wall. Is this the problem or is it something else? The equipment all checks out ok. When I watch a movie or listen to music, the sound is always a bit more prominent to the right of the room, even though the sound meter says otherwise.

A Yes, I am pretty sure your room is the problem. You might be able to correct it by putting some absorption material on the right wall, like a wall hanging (oriental rug for example). Your drapes on the left wall are absorbing the sound that would otherwise be reflected from that surface. Drapes are very good absorbers. You could also just hang similar drapes on the right wall, keeping them open during the day, and closing them when you are watching surround sound movies or listening to music in surround sound.

Q Is it OK to run surround speaker cables along together in a crawl space, or should I run them separately?

A I have never experienced problems with speaker cables being near each other, or with interconnects being near each other. However, be sure not to place the cables near to any AC supply cable. Also, don't place interconnects (cables that conduct signals from CD players, DVD players, etc.) next to speaker cables. Other than that, you should be fine with running the rear surround speaker cables near each other in the crawl space.

Q I have a two-channel stereo, 120 watt/ch integrated amplifier, with speaker selectors A&B. I would like to upgrade my system to surround sound, most specifically to DD and DTS decoding. What should I do? Do I have to buy a new receiver?

A Those old amplifiers can be very handy for something like this. Get a DD/DTS receiver that has pre-outs and pre-ins, and use your old amplifier with the front left/right pre-out jacks to drive the front channels. The amplifier power supply in your new receiver will be much better able to handle the center and rear left/right, without the drain of the front channels. Use a set of auxiliary jacks on your old amplifier, and set the volume control very low on both the new receiver and old amplifier when first turning the system on. You will have to adjust both volume controls to get it in a position where all channels are balanced.

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