Q&A # 222 - March 14, 2001

Staff

Q We at Analog Devices were riveted by your reviews of video performance in DVD players. You see, we spend significant time creating the video encoder that is found inside of the new Sony player. We were designed out of the **** player about 6 months ago as they went with a cheaper encoder. The impact of going with a cheaper encoder was very evident! Your work on the I to P technology was very thorough and accurate. We do not make chips for this part of the player, but we have watched the technology closely and agree with your conclusions.

Please let us know how we can be helpful to you as you review the players. We have an intense focus on delivering THE best video output quality to the DVD player market.

Regards,

Roger K. Smith

Video Product Line Manager
Analog Devices

A Thanks for your compliments. Stacey will be in touch with you about suggestions.

Q I am currently putting together a home theater system and would like to know the best way to connect the pieces for optimum performance (DVD to TV, DVD to Receiver, VCR to Receiver, DVD-A to Receiver, VCR to TV).

I will be using an Integra DTR 7.1 receiver (THX), Toshiba SD9200 Progressive Scan DVD (DVD-A as well), Sony Wega XBR 36" TV, and an old Sony Hi-Fi VCR. What are the best type of connectors to use for the best performance? I have a catalog from a notable cable/connector company and am overwhelmed by the sheer number of different types of connectors and cabling.

A For beginners, Radio Shack is a good place to shop for cables. Use their Gold Patch interconnects (with RCA plugs) for connecting most of your components together. Use an S-Video cable (Radio Shack has several lengths) for connecting your DVD player video out to the TV. Use a Toslink optical cable for the audio connection between the DVD player and your receiver. I like 6 foot interconnects in home theater because it gives me some breathing room when sliding components in and out for plugging or unplugging the cables.

Q (1) I am buying a new construction home that has been pre-wired for surround in the ceiling about 18" off of each corner. The room is 17' long by 15.5' wide and has a 9.5' ceiling. The L-shaped sectional couch will be on the back wall, which has a window spanning about 10' centered. Any thoughts on the best speaker for good rear imaging in a 5.1 setup? I am concerned with being limited to the back of the room. My future wife did not want speakers on the side walls and there is only a slight chance I can move the couch off of the wall a foot. What about ceiling speakers?

(2) The salesman also suggested Definitive in-wall bipolars. What do you you think?

(3) Unfortunately, the dealer that I really like only carries B&W in-walls, not Definitive. He says they will be timbre matched. Speaker upgrades are in my future, and I don't want to be restricted by the rear surround speakers.  I also would like some consideration as to which way I should point a bipolar array if chosen; front to back or side ways.

(4) What about direct fire, bouncing off a wall?

A (1) Ceiling speakers are a difficult thing. Anything with somewhat wide and even dispersion (smaller cones or some kind of mechanical dispersion mechanism) will give you a reasonable balance if you're sitting in a location that's more or less an equal distance between the speakers, and the channels are level-matched and time-aligned. The problem with speakers facing directly down (from the ceiling) is that almost all speakers are at least a little directional. If you sit more to the left, not only are you closer to the left than the right, but you're also in a more direct path, so that the surround soundfield will collapse towards that speaker.

In contrast, if the speakers are more to the side, and elevated, and pointing to aim slightly over your head, the directionality of the speaker, if it's consistent with frequency (i.e., has a relatively flat off-axis frequency response) works for you by lowering its output in your direction as you slide closer to it, making the surround soundfield more stable as a function of seating. You could use a mechanical lift to lower a small bookshelf type speaker out of the ceiling, or use a speaker that has its own angling built in, either by recessing itself or by using a motor to pop out and angle out when triggered. I saw some KEF models that did that a few years ago, but they were quite noisy, so I don't know what your other half would think about it. There are also some models of speakers that let you turn the angle of the tweeter.

Mounting speakers from the ceiling, as opposed to in-ceiling, gives you more options in term of angles, assuming you get a mounting bracket that will accommodate it. You don't want to have anything falling on your soon to be wife's head when there's an explosion. That's a good way to lose the whole theater.

Another option is to get some in-wall type dipolar speakers. Atlantic Technology and B&W come immediately to mind. Then, as you move more toward the speaker, the output in your direction becomes less and less, to the point that if you're directly under it, the only output you'll hear from it (if it's working correctly) will be the reflected sound. You give up some of the directionality potential of surround information in terms of localization with dipoles, but for your situation, it might be the best compromise.

In fact, if you mounted them in the conventional method in which the drivers fire forward and backward (as opposed to sideways), and they're to the sides, a la THX, you won't get any direct sound from either so long as you're sitting between them, in which case it could work out quite well. However the person sitting on the other part of the L couch will always be out of luck.

(2) Bipolars in an in-wall situation won't be too much different than a uni-directional, standard speaker. But they may be slightly closer to a dipolar radiation pattern, in that they will be slightly less directional but not close enough. A bipolar speaker radiates sound forward and backward in phase, as opposed to a dipolar speaker which puts the sound out of phase, so that in the direction where the output is equal (straight out from the wall between the two driver directions) the output cancels. So, there is no direct sound, and the surround speakers become difficult to localize, and the surround soundfield is diffuse, but more stable in your case because of it.

(3) I believe that those are dipolar, or at least have dipolar operation as an option, in which case I'd lean towards that too, with a slant towards the front/rear orientation of the drivers. Bipolar front to back will give you more directionality, if they're off to the side of you. It will be the opposite if you place them behind you.

(4) The nice thing about a unidirectional speaker is that you can use the wall to increase the amount of reflected sound. However, if you were to use the reflected sound exclusively, I think that perhaps a dipolar speaker would be better suited for the task.

Q I have an older Marantz Gold Receiver, Model SR225. It has a limited number of inputs, and I would like to use the Phono input for something other than a turntable. I have a Marantz Turntable, which works fine. However, when I try and hook up another source to the Phono input, such as a VCR or CD Player, nothing works as it should. Can this input be used for anything other than a turntable? The only difference I can tell is that my turntable does have a ground wire.

A The phono input has much greater sensitivity than other inputs. The CD input, Aux input, Tuner input, etc., have a sensitivity such that it takes perhaps 1 or 2 volts to fully drive the power amplifiers in the receiver. Phono inputs, by comparison, only need perhaps 10 millivolts (one hundredth of a volt) to drive them. So, what happens when you plug your CD player analog output into the phono input of your receiver, is that the phono input is over driven, because the output of the CD player might be up near a volt. Don't use the phono input for those other components. Instead, get a switcher, like those sold at Radio Shack, to let you add more inputs.

Q What is the best type of speaker cable to use when the surrounds are 40 feet from the receiver?

A Use heavy gauge cables, such as 12 or 13 gauge.

Q I've got a DVD player and an A/V receiver both with a built in DD 5.1 decoder. I wonder what is best: (1) to connect the 5.1 analog output jacks from the DVD to the A/V receiver and let the A/V do the work, or (2) to use the optical coax (I don't know if, in this case, the DD signal is decoded or not).

A Although the sound quality between the two choices might very well be the same, you are better off with using the optical (it is not a coax cable by the way), because this is the only way you will have access to the various DSP modes (sound fields) that come with all receivers. If you use the 5.1 analog connections, this bypasses DSP modes in the receiver, and goes to the volume control, then the power amplifiers. The Toslink optical connection, as well as any coax digital connection, does contain the DD signal and the DTS signal, undecoded. The 5.1 connection will contain the DD decoded signal, and may or may not contain the DTS decoded signal, depending on the model and how new it is.

Q Your latest article on Pro Logic II is incredible. You guys are mopping the floors with all the other A/V publications. More more, more!!

A Well, our intent isn't to mop floors with anyone, but thanks for the compliments.

Q This question is about burn-in on RPTV. You see gray bars on some sets and black bars on other sets. Some claim that black is the absence of all color, so the phosphors aren't being scanned, so you don't have to worry about burning in black bars, but you do have to worry about gray bars. Some have said that the black bars over time will cause a contrast difference between where the movie is played and the black bars are displayed. What's the story on burn in?

A If I had to choose between black bars and gray bars, I would choose gray, because then, all areas of the TV screen are being used, and you are less likely to see lines that separate the bars over time. However, even the black bars are receiving a little bit of electron exposure, as they are scanned, but just don't get very much.

� Copyright 2001 Secrets of Home Theater & High Fidelity
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