Q&A # 38 - November 18, 1997
Staff
Q I use a Sony SPD-EP9ES AC-3 decoder, and compared to my Proceed Pro Logic
decoder, the Sony is much more difficult to set the bass level.
The subwoofers have more work to do in AC-3 mode than in Pro Logic mode
since they have to produce the bass for all five channels plus the bass of
the
LFE channel. As soon as the LFE-active light is on, the woofers are
severely
overloaded. In "Top Gun", everything seems OK, but in "Crimson Tide" I heard a
loud
BANG from the woofers when the submarine explodes, while I almost got no
bass
at all in "The Lost World". Why is each title of LD's LFE level so
different? Do you have any suggestion on how to set the level of the LFE channel?
A It is easy to overdrive a subwoofer, because low frequencies demand so much power, and also, our ears are not as sensitive to low frequency distortion as they are to mid-range and high frequency distortion. So, we are apt to turn the subwoofer volume up too high. If you like intense, deep bass, it is very important to get a good subwoofer. The $399 jobs will just not cut it. They are fine if you are watching Jane Austin stories using a 70 watt mass market receiver, small satellite speakers, the subwoofer, and Pro Logic. But if you are into action films, DD (AC-3) and DTS, and like the room to shake, it takes a big, hunky subwoofer. Spend at least as much for your subwoofer as you do for the receiver or outboard power amplifier. DD and DTS are very demanding in the low frequencies, not so much because they have more of them, but because they dip down very low (lower than Pro Logic) which really asks a lot from the subwoofer amplifier. That bang you hear is the subwoofer amplifier clipping no doubt. The only way around this is to turn the volume down on the LFE channel in relation to the other channels. Every movie has a different amount of low frequency signal in the sound track. It all depends on what the director wanted to achieve. When I use a small subwoofer, I set the crossover frequency (low pass) to about 40 - 50 Hz and the volume control knob (on the subwoofer panel) to a low - mid level. That way, even if the bass is not quite as loud as I would like it, the bass that is there, is clean. You can also put the subwoofer in a corner, which will increase the bass output to the room. Even so, don't turn the subwoofer volume up too high. You should not be distracted from the movie by the bass. If a car blows up on the screen, and you think, "Wow. Listen to that bass," then the subwoofer volume is set too high. Although voices from the center channel are directed to your attention, bass is not. Those deep rumbles are supposed to add to your home theater sensation, not be the focus of it.
Q I own a set of B&W speakers with what I presume are "five way" binding
posts. Does this refer to five different ways of connecting loudspeaker
cable? If it does, exactly what are the five ways (I can think of four) and
more importantly, which method of loudspeaker cable connection provides the
best sound? Banana plugs? Spades tightened with a wrench?
Thanks for continuing to provide one of the best sources of audio
information I've found on the web or in print.
Aloha
A The five ways are bare wire wrap, bare wire in threaded post hole, banana plug, pin, and spade lug. You could also put one edge of a spade lug in the threaded post hole, and sometimes, even put a banana plug in the threaded post hole. I don't think any of them provide the "best" sound, but spade lugs are the most secure.
Q Thank you for your excellent web site. I
plan on upgrading my whole system next summer and will be looking at
adding a DVD player. However, I don't want to buy a large library of
films. I'd much rather have the opportunity to rent them at my local video
store. In my area, I have three major video outlets, Hollywood,
Blockbuster, and Warehouse. Curently, none of them offer either LDs
or DVDs to rent. At some point in the future, will we be able to rent
DVDs at these major chains? It just seems to me that if DVD and DTS
formats are to gain in popularity, the rental option for movies is a
must. Do you forsee this happening by next year, or will I be doomed to
buy movies?
A Video stores are starting to rent DVDs. Block Buster intends to start renting DVDs, and some of the stores have already begun. Tell your local video store that you want DVD. If they
get enough requests, they might just start sooner. It also depends on where you live. In Redwood City, California, I (JEJ) rent LDs and DVDs from two video stores. In Seattle, I (JEJ) have found two that rent them, one in the downtown area, and one in the university area. But these cities are both in regions that had early release of DVD (Spring, 1997). If you are in a small town, it will take a while, perhaps a year, before you are likely to see DVD rental. Usually, the stores that rent LDs also will rent DVDs. You can look up video stores in your city (or nearby city) using one of the Internet search engines. For example, in the www.hotbot.com search engine, I clicked "Find" "Businesses", then video and San Francisco, California, and got 171 stores that rent tape and video discs. At that point, you have to start calling them by phone to see if they rent LDs and DVDs (I located a couple of stores in San Francisco that way).
Q I have a Sony DVD7000 player with three separate component video
outputs
and a Lowe Calida 100hz digital TV with scart inputs as well as a
separate
composite input and S-Video input. Can the component video from the DVD be connected to any of the scart
inputs? The TV on the menu states it will accept RGB. However, I am not sure
what is the difference between component inputs and RGB inputs. If the
component video can be accepted by Scart either in RGB or component, what
cable is required or particularly what scart pins relate to the three Sony
outputs? With this TV, would I notice any difference between the component
video if it can be input compared to the S-Video or am I wasting my time
pursuing this matter? The TV instruction manual states nothing about component video
input but can clearly accept the RGB input by Scart.
A Component and RGB are different. Component is a form of RGB that has
gone through a simple resistor matrix. Both Meridian (SCART for overseas folks) and Faroudja offer DVD players with
RGB outs as well as component. Until a component-to-RGB converter becomes
available in the consumer market, you should use the S-Video.
Q I am very pleased with the color from my Toshiba 2107 DVD player using an S-Video link directly into my 35 inch direct view Sony. I am however, just
starting to experience audio problems where the center channel dialogue is
too faint and the front and rears seem excessively loud in many scenes. I
find myself more and more adjusting sound levels in the middle of movies,
which is troublesome especially when I have folks over to enjoy the show.
My understanding is that, in general, all speakers should be adjusted with
my receiver's 5.1 test tone to be equal. If so, I'm having problems, and
I'm also not sure where to adjust my powered sub's individual volume
control. Although I know you recommend the Video Essentials DVD, I felt
that 40 dollars was a lot to pay for a disc that I would not use very
often after initial settings, but now I'm thinking differently. Will the
VE disc help me or will I have to accept my thinking that different DVDs
have different audio peaks and dialogue tracks and I will have to manage
as best I can with my volume controls?
A The Delos DVD Spectacular disc has channel-balance pink noise. It sells for $24.95, and we reviewed it last week. With all the different formats of discs (LD Pro Logic, DD, and DTS; DVD Pro Logic and DD), I find that I have to tweak the sound for each movie. Not all the time, but many times. Mostly, it is the center channel that needs adjustment, followed by the rear surrounds, usually when I go from a DD movie to a Pro Logic movie. I don't use test tones though, because they don't necessarily correspond with the balance on a particular movie. I use test tones when initially setting up a new surround sound processor, but after that, I fine tune the audio everytime I put on a new movie.
Q What exactly is a test tone of 400Hz @ -20dBFS? How and why do we use it
as oppossed to a Test Tone of say 1KHz @ -10 or 0 dBFS? In very simple
language, how do you calibrate this tone with, let's say, a simple Radio Shack SPL
meter? Do we adjust gain/volume so the tone is equally loud in all
channels . . . and should this loudness be 75dB 85dB?
A Test tones from discs are set below maximum recording level, such as - 20 dB, mainly so you won't have a rude surprise (too loud!) when the test tone comes on. You could actually send it directly into a power amplifier for certain testing purposes, and it would be at way below clipping (about 2 watts from a 200 watt amplifier). At 0 dBFS, the tone is recorded at maximum level on the CD, so the amplifier would be at full output. Using a 400 Hz test tone, all the speakers in a surround sound system will reproduce it, so they should be set to the same level on your test meter, and 75 dB would be fine. Of course, that is just for general setup. After that is done and you are playing a movie, feel free to set individual channel volume according to personal preferences. The only rule to follow is one of having a good time.
Q My understanding is that typical Japanese A/V receivers such Onkyo or Yamaha have a lot of functions and features, but the sound fidelity is not so good. What do you
think? If so, are there any other A/V receivers which do not have that many functions but have good sound quality? I have to use the system with my family, and they do not want to go only with an integrated amp. Hope you
can give me a specific model and their prices since I am also in tight
budget.
A The mass market receivers are actually quite good these days, especially since they started putting speaker binding posts on (instead of those cheesy spring clips), as well as pre-ins and pre-outs for upgrades. The differences between these receivers and the high-performance processors are small and appropriate for those consumers who are particular to having every nuance of the sound come through. However, this does not extend to the really inexensive receivers, such as the $299 specials. Your family would probably be quite happy with something like the new Yamaha RX-V992 (MSRP $999), which has DD decoding built-in, along with pre-out jacks should you decide to add a more powerful amplifier later (in the meantime, stick with 8 Ohm speakers having at least 88 dB/w/m sensitivity). If you really want a stand-alone processor, wait until after the 1998 CES. I understand quite a few new models are being introduced there.
Q Since adding a DVD player and Dolby Digital processor to my
system, I've had a tendency to play movies at high volumes. While
playing the Dolby Digital trailers on "DVD Spectacular!" (reviewed in Secrets, V4 - N4), I'm pretty sure I heard every speaker clip, including the subwoofer. My amp is the Yamaha 2090 receiver with 100x3 watts in front and 35x2 watts in
rear. Now, I've never heard clipping before and don't know how to identify
it. So, if I did clip my speakers, how can I tell if any damage occurred?
What should I listen for? What are the signs of "fried" speakers?
A Yes, clipping is pretty easy to do with the new digital surround sound. It has a sharp crackling sound, and the music will sound mushy. If you only did it a couple of times and your speakers are still playing, it is unlikely any damage has been done. When the speakers are "fried", they don't play at all because the voice coil has broken. The tweeters are usually the first to go. I've cooked a few of them in my day. The interesting thing is that it is most often not having enough power (so the amplifier clips, producing square waves) rather than too much power that causes the damage.
� Copyright 1997
Secrets of Home Theater & High Fidelity
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