Q&A # 225 - April 6, 2001

Staff

Q How much difference does it make in the image quality when a DVD is produced in 16:9 Enhanced or Anamorphic?

A It makes a huge difference with 16: 9 TVs because, with anamorphic production, the image occupies what would have been blank space otherwise. So, when it is viewed, it is stretched horizontally. The result is a significant improvement in the image resolution. It looks sharper. For standard TVs, the player downconverts the image, so there is no real advantage. The anamorphic image on a DVD is different than the anamorphic image on a film such as Panavision^� or CinemaScope^�. With anamorphic film, it is simply squeezed horizontally when the film is exposed in the camera and unsqueezed when it is projected. The entire 4:3 film space is used, and most of the time, it is a 2.35:1 movie that is being presented. It is squeezed and unsqueezed 2:1. More image is stored on an individual area of the film this way, and it does result in some loss of resolution compared to having the unsqueezed wide image on 70mm film rather than the squeezed image on 35mm film. With the anamorphic DVD, image is stored where there would normally be black bars at the top and bottom, and when viewed on a 16:9 TV, it is expanded horizontally to give the wider aspect ratio. The process can be used for 16:9 (1.85:1) as well as 2.35:1 movies, or any wide aspect ratio for that matter (such as the 2.76:1 ratio for "Ben Hur"). So, for a 16:9 movie, the image occupies the entire 4:3 space (all 480 lines), and is expanded horizontally for a 16:9 TV. All 480 lines of the 16:9 TV are used to show the movie, without any zooming. If the DVD is non-anamorphic, not all of the 480 lines are used, and it has to be zoomed to fill the screen on the 16:9 TV, which means not nearly as sharp a picture.

Q I am still kind of confused as to the advantage of bipolar and dipolar speakers. Is there a definition that would better describe them? I look at the pictures on your site and understand the concept but how could it be used to my advantage in home audio?

A If you've ever been to a movie theater with surround sound of any kind, you may have noticed that there aren't just two speakers shoved into the back corners of the room like we do at home. There are several speakers around the sides and back of the room. In a classic Dolby Stereo setup, all those surround speakers are one big array. In Dolby Digital, DTS, and SDDS, all the speakers to left of center are the left surround array and all those to the right of center are the right array.

Now an array of 8-12 speakers on each side has quite a different sound than a single speaker. You are in fact "surrounded" by sound in that it is coming from seemingly everywhere.

When a soundtrack artist assembles a soundtrack, they mix and weave the elements while listening to their work over a system much the same as found in the cinema. In relation to what we're talking about here, this means that the surround sound effects are going to be tailored to sound "correct" over the speaker arrays found in the theater.

Many home theaters use just a pair of speakers for the surround channels, one for left surround and one for right. In many cases this results in surround sound effects being too "directional" in that you hear them as coming from one of the two speakers in question. But a good number of enthusiasts feel strongly that this is not the effect which the soundtrack artist intended, so they look for ways to recreate that cinema sound at home.

Within the small, tight acoustic spaces of home theater, a pair of dipole speakers are the most practical way of emulating the "type" of sound produced by those speaker arrays in the cinema.

You may have noted in our primer that dipoles have drivers on opposing sides which are moving out of phase (one cone is moving out of the enclosure while the other is moving inward). Dipoles get mounted to the direct left and right of the home theater audience such that the speaker elements are firing forward and backward, but not directly at the audience. This has two effects: for one, sound is distributed evenly through the room, thus "surrounding" you in sound. Secondly, because the "null" of the dipole is facing the audience, and the drivers are out of phase, the sound is almost totally unlocalizable (i.e., your ear-brain can't tell exactly where the sound is coming from).

Bipolar speakers are similar to dipoles in that they have drivers firing in opposite directions. But they fire in phase with each other (both cones move inward or outward at the same time). Bipolar designs are found mostly in exotic main speakers (not surround) with the "front" drivers firing at you (as any normal speaker would) and the "back" speakers firing at the wall behind the speakers. So in addition to the sound coming right from the speaker, there is also "reflected" sound reaching your ears (the sound from the "back" drivers bounces around before reaching your ears). Some feel this gives a more life like musical presentation since real-life instruments also radiate sound in all directions.

Q My Kenwood 1080 receiver has no pre-outs. I would like to add an outboard amplifier sometime soon. I saw Radio Shack selling an in-line  converter for adding an amplifier to car stereos. Would this work for home receivers as well? Would it provide the same quality of upgrade?


A It probably would work OK, but you are not going to realize the potential quality of the new power amplifier by using a band aid like this. You are really much, much better off by purchasing a new receiver with more power built in. You could also just use a power resistor between the speaker output and the power amplifier input, but again, you are going to lose some of the sound quality.

Q I have a system that consists of a pair of Krix Esoterix 1 Mk2s, Krix Centrix Center, Krix Equinox Rears, and Krix Seismix 5 Subwoofer.  I have a Denon AVR-5800 amp and have it set up with the center and rear speakers set to Small (so bass is directed to the sub) but have the front speakers set to Large. I have read that it may be better to set the front speakers to Small as well even though the Esoterix are full range speakers. What do you recommend?

A I assume you are thinking that because the rears are set to small, the others should be as well, so as to balance the tonality. However, when you have full range speakers like the Esoterix, those speakers should be set to Large. Setting speakers to Small is to take care of the fact that small speakers can't respond to low frequencies, and those frequencies in the movie would be lost. But, the crossovers in the majority of receivers and processors is too high (80 Hz and up). This results in the area of 50 Hz to the crossover frequency going to the subwoofer, and you can tell where they are coming from, messing up the sound stage.

Q I have a question concerning surround speakers. My setup at present is a Yamaha receiver Dolby Digital (793), two Pinnacle Gold Reference Tower mains, a Pinnacle centerwide speaker (all 8 ohm impedance), a Pinnacle 250 watt powered subwoofer, and two old Bose 2-2 8 ohm as the surrounds. I would like to replace these surrounds but I don't have floor space for two more tower speakers so I am looking at smaller speakers I can wall mount. Is it a good idea to match the fronts and get the Pinnacle gold reference mini-monitor speakers or is there some other brand of speaker that I can wall mount that you might recommend? I do plan to get the Outlaw 750 amplifier (165 watts times 5) sometime in the future.

A What you are asking is that, because your rear speaker space is your weakest situation, should you get small speakers in the front to match small speakers in the rear. I would say that the best situation is full range speakers all the way around, followed by full range in front and small in the rear, with the least desirable position as having small speakers all the way around. What we are talking about here, of course, is the sound, not the aesthetics of the furniture. As long as you have the same brand of speakers everywhere, the tonality should match. If you really want to have the same size in front and rear, then try to find some monitors that you can mount on the wall, but having a - 3 dB response no higher than 50 Hz. Set them to Large in your receiver's bass management menu, and set your subwoofer to about 50 Hz for the low pass crossover frequency.

Q Can you suggest some further reading for descriptions of classes of amplifier operation you mentioned in your primer? In particular, I am interested in Class H.

A Here is a link http://www.win.net/audtatious/audio/ampclass.html.

Q I was reading one of your very interesting articles and, as a possible buyer of a DVD player, I noticed that you have written that the Pioneer DV-525 has a built-in Dolby Digital decoder. Are you sure of this?

A The sentence in that review was confusing, and I have edited it for clarification. All DVD players have always had DD decoders, but some players have DD and DTS DACs for 5.1 analog output. All new players also decode DTS, but they are just starting to have DTS 5.1 analog output. From now on, we will specify whether the player has 5.1 analog out, and not worry about the confusing term "decoder".

Q When I zoom in a 2.35:1 movie to fill the screen on my 4:3 TV, the images look sharper, and I think I count more scan lines. Is this because of the line doubler or is it because of the progressive mode on this TV? I am not really getting the 480 lines as a I think I should with 2.35:1 movie on my 4:3 HDTV.

A There are always 480 visible lines on the TV in NTSC. It is how many of those lines that are occupied by picture and how many by black bars that give you the final view. Even with a line doubler, you are still seeing 480 lines, but with each scan, all 480 lines have picture, rather than just having the odd numbered or even numbered lines having picture. There are lots of variables to consider: Anamorphic or non-anamorphic DVD as the source, progressive or interlaced output setting, 4:3 TV or 16:9 TV. You just have to try various combinations out with your setup, and whatever you like best, you use.

� Copyright 2001 Secrets of Home Theater & High Fidelity
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