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Q&A # 181 - June 4, 2000

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Q Is there any truth to fact that in order to get 96/24 audio you must use the analog outputs on your DVD player? And if so why?

A The first DVD players that had 96/24 DACs only used them to decode the signal and output analog audio. If you used the digital output jack, the 96/24 was down converted to 48/16. However, a few DVD players started showing up that would output 96/24 digital bitstreams, and they are more common now. You just have to look at the instruction manual of players you are considering to see what they do.

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Q I have a pair of Klipsch KLF 30s. I am moving, and my belongings are in storage. With my new setup, I want to have the speakers under my TV screen. How do you think the Klipsch would sound?

A They may actually sound better than when the center channel speaker (CC) was on top of the TV because TV screens cause some loading in the 100 Hz region. You can also put the CC speaker vertically under the TV, which is something you should try.

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Q My question deals with a choice of speakers for my surround sound system. My choices are basically between the Paradigm Reference ADP- 450 or the Paradigm Studio 40s. The main difference between the speakers are the dipole configuration of the ADP-450s and the monopole Studio 40s. I have heard a ton of different opinions on this, and I am not quite sure what to believe. First, I have heard that the dipole is the best way to go, especially for movies, and the do not draw TOO much attention to themselves. They are recommended by THX and many speaker companies. The second opinion that has become more popular lately is that the rears should be monopole with the invention of Dolby Digital and DTS providing a better, fuller sound to the rears, especially with the onset of multi-channel music just around the corner. So what is the best route to go with the future in mind, Monopole or Dipole rear speakers, and where should they be placed in respect to the listening area for optimum sound? Secondly, with a 400 watt per channel amplifier, would it be justified to use a full-range speaker for the rear channels for movies and multi-channel music? What about bipolar speakers for the rears? I want to make a decision for the rear channels that I will not regret within only a few years, and that will be equally effective for movies and music.

A The choice of monopole, bipole, or dipole is not so much a matter of the type of program material as it is your personal preferences. Monopoles give the most precise sound stage. Bipoles and dipoles have a more diffuse sound stage. This means that the sound seems to come from "over there somewhere" rather than obviously coming from the speaker enclosure. This is what is meant by the "not drawing attention to themselves" opinion you have heard. Bipoles have less cancellation between the two sides of the speakers, so they work nicely when facing sideways along the walls as rear surrounds. Dipoles have a lot of cancellation to the side, so the produce an extremely diffuse sound stage if placed sideways along a wall. Bipoles and dipoles are a little more difficult to place in the listening room, and I use monopoles all the way around, because I don't have the space to put every speaker in its ideal location. If you want the highest chance of getting a satisfactory setup, get monopoles for all channels. A high powered amplifier works great for music and movies regardless of the speakers, but I would suggest full range floor standers for front and rear. If you are getting the new EX system, probably two wall mounted speakers will be best for that channel (EX).

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Q I have bought a slightly used Sanyo projector model PLC 250 which has both Scart and S-Video connections. I am yet to buy a DVD player but am leaning towards some well reviewed budget models, namely Toshiba 2109, Pioneer 525, and Sony 525. I shall greatly appreciate your advice on the following: 1. What would provide better video quality - Scart or S-Video, given that the distance from the source to the projector is about 18 feet? 2. What connection between the DVD player and my Yamaha DSP-A2 would offer the best performance for DD & DTS: Optical or Digital Coaxial? I understand that the Tosh does not have an optical out, whereas the Pioneer and Sony both do. Is that a major factor against the Tosh, or is digital coax better anyway?

A I would recommend the S-Video connection, but 18 feet is a long distance. Make sure you get a good S-Video cable. Optical (Toslink) and coax digital cables seem to work about the same in my experience. I use Toslink though, just to eliminate ground loop problems and impedance problems, both of which are an issue with coax cables. The new Toshiba SD-6200 DVD Player appears to be superb, with component video, progressive scanning, dual disc exchange, and the ability to adjust the image to fill the screen (for those consumers who hate widescreen), as well as eliminating overscan loss of image edges. We will be reviewing this shortly

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Q I have recently set up a home theater system. It is based around EAD Theatermaster and Powermaster components. The sound is terrific, but I am wondering if someone can say some words about background noise. Not while playing music, or movies, but when nothing is playing. I still haven't received my furniture to place my equipment, so everything is still just sitting around on boxes, and on the floor. This makes most of the cables to be tumbled together. I am also using a Voltage converter for my CD player. This is close to all the cables. All this I would guess leads to noise in the system. What makes background/static noise on a system? How much noise will there be still with the "perfect" system?

A Noise is a result of numerous factors. One is the inherent noise in the component electronics. The transistors have a certain amount of noise that they generate, and you can't do anything about it. This type of noise is the "hiss" and is constant. Depending on how well the parts are shielded, you might get some hum that cannot be eliminated either. However, noise generated externally can usually be corrected. Electrical hum from ground loops or cables being too close to AC power cords, or mechanical hum induced by the rheostats in light dimmers can be fixed, or certainly reduced. Noise produced by poor AC supplies can sometimes be corrected by using balanced connections, if the component is fully balanced. If the interconnects are picking up noise, sometimes using balanced cables will fix it even if the component is not fully balanced. I have found that using fully balanced preamplifiers and power amplifiers, with balanced interconnects, reduces the noise to inaudibility. With so many components now in the typical home theater system, noise is getting to be a bigger problem than it used to be.

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Q 1) I recently purchased a Home Theater receiver (Denon AVR3300) and have had some questions in regards to setting up the speakers properly. If my front speakers (Boston Acoustics VR30s) have a low end frequency response of 42 Hz, and the sub's crossover lowest setting is 50 Hz, where would you recommend I set the crossover on the sub? The common answer seems to be "set it where it sounds best...", but there must be some guidelines/rules for properly blending the sub with the fronts. Also, the receiver allows me to set each speaker to either "large" or "small". When set to "small", all (?) frequencies below 80 Hz are directed to the sub along with the LFE. Based on my setup below, which speakers should be set "large" vs. "small"? Here's my current setup: Sub: VR500 (50 Hz -100 Hz adj.); Fronts: VR30 42 Hz -20 kHz currently set as 'large'; Center: VR12 58 Hz -20 kHz currently set as 'small'; Surrounds: VRS 100 Hz - 20 kHz currently set as 'small'. 2) In 2 channel stereo, what is it that causes the music to begin to sound 'distorted' at higher volumes? When I begin to crank up the volume (00 -05db) I can detect what I can only describe as the music begins to 'break up' a bit and sounds less clear and crisp. I guess my preference is to be able to crank up music as loud as I can take it without doing harm to my ears, but while maintaining a very clear, undistorted sound. Would you guess the source of the problem is in the speakers or the amps in the Denon? For what it's worth, if I remove the grill on the speakers at this volume, they don't seem to be over-stressed?

A Set your rear speakers to "Small", and the rest to "Large". Set your subwoofer crossover to 50 Hz. This will produce a hole in the rears, but this is better than having boominess due to overlap between the front speakers response and a low pass setting of 90 Hz. Your distortion is probably the Denon. Receivers are notorious for this. You can clear it up by using an outboard power amplifier for the front channels.

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Q I would like to buy an external DAC for my system. My preamp has no analog bypass and decodes everything to digital, so should I bypass the preamp and hook the DAC directly to the amplifier?


A Your success here will depend on the quality of the DAC in your preamp and the quality of the outboard DAC. An outboard DAC is not automatically better than the one in your preamplifier/processor. Also, it is critical to have a good 75 Ohm digital cable between the preamp and the outboard DAC, or use Toslink. Depending on the quality of the A/D converter in your preamp, the digital conversion may not make any noticeable degradation. I would suggest just trying the outboard DAC with a good return policy, in writing.

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Q I have just recently purchased a Velodyne HGS-15 sub and am having a love/hate relationship with it!. I love the sound. However I hate the two problems that I am having with it and would greatly appreciate your input. 1. My seating distance from this sub is approximately 15 feet, and I am hearing a mechanical type hum. This hum is there even when I have no interconnects attached to the back. Note that the sub has no ground connected to it and during normal scenes in a movie I cannot hear this hum, but during quiet scenes like say in "Pleasantville", I can hear it. I was told that the hum was only audible from about two feet away, but I can still hear it from 15 feet away. I put the volume on the sub only to about 20% up. Any way to fix this? 2. I have set the sub to turn on automatically whenever it gets a signal. However, the sub is also turning on sometimes whenever I turn my hallway light switch on, or furnace turns on (both are on separate circuits from the sub or audio equipment). I tried removing all grounds which did not work. I have a DC-1 as my preamp plugged into a Monster HTS 1000 surge suppresser. I believe that when the light switch/furnace is turned on, the switch may spark (sometimes) and cause the subwoofer to see a signal (somehow?) and turn on automatically. I already exchanged the sub for another HGS 15 and spent several hours trying different things - but still have the same above problems.

A If it is a mechanical hum, the power transformer in the subwoofer power amplifier is responding to noisy AC, which could be local in your house, or something from upstream (neighbors). If the noise is a "shhhh" type of sound, this is the servo feedback system in the Velodyne circuit, and it is normal for that speaker. The noise you are getting from your light switch and furnace can possibly be corrected by the use of switching suppressors, such as AudioPrism Quiet Line AC Modules ($130 for a set of four).


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