Q&A # 102 - February 9, 1999

Staff

Q If your receiver subwoofer output sends 80 Hz and below to the subwoofer, and (if it is like my receiver) it sends 80 Hz and above to the five speakers AND you set your subwoofer lowpass at 50 Hz, where does the 51 Hz to 79 Hz signal go? The subwoofer gets only <50 Hz, the speakers >80 Hz. BTW, I have the Harman Kardon AVR 80II. It's THX which means something in terms of High/Low pass.

A Since setting receivers to "small" means, in most cases, that they end up with everything below 80 Hz removed (and sent to the subwoofer instead), you have to either use the crossover bypass switch if your subwoofer has one, or set the crossover low pass on the subwoofer to a value near 80 Hz, depending on the crossover slope. Otherwise, the frequencies between the subwoofer low pass cutoff and the receiver high pass cutoff will be lost. What I do is use a low pass setting of about 70 Hz on the subwoofer when using bookshelf speakers, and with the receiver set to "small" for the speaker size, the rolloff (slope) below 80 Hz in the receiver, along with the rolloff above 70 Hz in the subwoofer, results in a smooth transition between the speakers and the subwoofer. Depending on the receiver and the speakers, it is sometimes necessary to change the lowpass setting on the sub to, say, 60 Hz. You have to just try it out and see. Nothing is engraved in stone. Whatever feels good, do it. A problem will occur if you have too much bass (overlap between the sub and speakers) in the area of 80 Hz. It sounds boomy, and this is very objectionable to me. Sometimes I get the best results if I set the receiver to "Large" for the speakers even when using bookshelf speakers, and then I set the low pass on the sub to about 50 Hz. For floorstanding speakers, I usually find the best sound at a subwoofer low pass setting of about 50 Hz. I don't ever set the low pass to 90 Hz or above. This causes boominess with most subwoofers.

Q I am in the process of buying a Toshiba TW40F80 widescreen television. The store where I will eventually be buying the television has a demo for sale at a considerable reduction. The question I have involves burn-in of the gray bars on the side which come on the screen in the 4:3 mode. Once I adjusted the TV the picture was fantastic. The only thing which is giving me concern is that when the TV is in widescreen mode, there is a slight (and I do mean slight, imperceptible most of the time but on occasion just enough that if you are looking you can see it) line or something that makes it possible to see where the 4:3 mode of the TV is or where the gray bars would be if it was in 4:3 mode. Is this normal for a widescreen or is it burn-in? I have heard that the gray bars were used instead of black so no burn in would happen. There is no other TV in the store to compare this to.

A So, you can see vertical lines on either side where the border of the gray bars would be in 4:3 mode? To me, this represents burn-in, probably from having the TV on in 4:3 mode for a long time in the store. Try it on one of the widescreen TVs in a different store. Of course, this is why it's on sale. If you buy it, even with the burn-in, you should get it at substantial reduction in price, as in 50%. Other than that, it is probable that you would eventually get burn-in with a brand new TV at home too, since most programs are in 4:3. The reason they use gray is so that even the blank bars get a mid-level dose of electrons. Otherwise, if the side bars were black, they are not getting much electron dose, and burn-in lines would be even more obvious. This brings up something we all need to consider when we ultimately go for a 16:9 TV, such as is the case with HDTV. Since most TV programming will be 4:3 for some time to come, we should probably watch the 4:3 programs with the brightness turned down very low, so that burn-in of the 4:3 edges will not happen so fast. Or perhaps just watch everything in 16:9 mode.

 

Q I have a Zenith TV that has a variable volume output and a Spacial Equalization mode which enhances the sound quality. I also have a Sony Pro-Logic receiver that recieves its input from the Varibale output on the TV. This allows me to adjust the volume using the TV and allows me to set a "high limit" on the amp so that the kids don't blow my speakers.

I have two questions:

1. Can I damage my amplifier by running the audio from the TV instead of through the VCR and using the VCR as the TV tuner?

2. Why do the rear sound effects increase so dramatically when I enable the SEQ mode on the TV, and can this damage the amp?

A In general, the variable line-level out from a TV goes from zero output up to the same level that it would be if it were a fixed level output rather than variable, and that level is about the same, or perhaps a little higher, as it is from the line-level audio output jacks on your VCR. It is not high enough to damage your amplifier, although it might cause obvious distortion if turned up all the way. The SEQ mode changes the phase relationships of mono signals in the two stereo channels, and this results in more of the signal going to the rear when using the Pro Logic mode of your receiver. It won't harm your equipment in any way. However, the mono signal normally might be going to your center channel, and with SEQ, some of it goes to the rear, so the sound might appear to be coming from the wrong place.

Q I was looking at a Pair of Infinity Reference Series Speakers, and they said that the woofer in it was a 6.5 inch Co-Injected driver with LMT. What I want to know is what does Co-Injected mean also what does LMT stand for?

A All manufacturers use marketing terminology that is designed to impress consumers. One of my favorites is in describing metal cone drivers as being coated with ceramic. What they are really saying is that the aluminum driver has aluminum oxide, or "rust" on the surface. But calling it ceramic, which from a material science standpoint it technically correct, sounds much better. "Polymer" is another one. It really means plastic or rubber. All are correct, but the difference is marketing. Some of the finest subwoofer cones in the world are made of paper pulp. Not very glamorous. The manufacturers don't worry about this mundane material because they don't need to. They sound fantastic, and that is the bottom line: the sound. Modern drivers are made of all kinds of exotic materials, but the question you really need to ask is, "how does it sound?" You should also add some other questions to the checklist. How does it look? Is it well built? Does it have the features I want? Is it a good value? Other than that, specs and advertisements are half informative and half entertainment.

Q What is the secret to getting good surround effect without having to have the volume up so loud that is bothersome to a wife who can't stand to go into a movie theater anymore due to the loud volume?

A I know the feeling. Try keeping the main volume control down a bit, with the center channel turned up a little more than the other channels so you can hear the dialogue. Also, set the crossover frequency of the subwoofer down to about 50 Hz - 60 Hz and turn the volume of the subwoofer up a bit. This will give you nice deep powerful bass, which is not so bothersome to the ears, moderate loudness dialogue, but the explosions won't have loud high frequencies.

Q I'm looking for cables to use with my surround speakers. I'm using XLO ER-11 for the front channels, so I'd consider XLO ER-14 for the surrounds. My question is if I need 40-feet long for each channel, would it affect the quality of sound for this kind of long-run cable? Or anything else that I should consider?

A There is no way around the fact that cables act as filters for the electrical signal. Select speaker cables that have low inductance. Most cable manufacturers can supply you with that information.

Q I have a 5.1 ready Pro Logic amp and am looking at the Technics SHAC500 for AC3/DTS decoding. I've learned that both the SHAC500 and the Sony EP9ES control volume in the digital domain so that answers my question of sound degradation through dual analogue volume controls when using such a decoder with an amp like mine. While the EP9ES should theoretically have no sound degradation due to its use of "a microcomputer-controlled static D/A output to control the current value (i) of the reference electrical source" (http://www.sony.com.sg/consumer/consumer/Hifi/Amplifiers/sdp-ep9es.html), some have suggested that other processors control digital volume by "stripping off bits" (the lower the volume on the processor the more bits that are stripped). How true is this and how badly will they degrade sound? I am asking this because I have an extra (stereo) integrated amp which I can hook up to the SHAC500 (for more available power) but want to control both amps using the SHAC500's master volume control. HELP! The SHAC500 is perfect for me in terms of cost and making the best of what I already have.

A The simplest digital control of volume involves dividing the original digital number, which represents the volume, by another number. Unfortunately, the resulting number from the division may have too many decimal places to be completely represented by a new digital value, and the leftover is discarded. So, part of the original digital data is lost. Modern digital volume controls have proprietary technology that goes much deeper than the marketing description allows. However, the bottom line as we have said many times is, how does it sound? The only real test is for you to go and listen to the SHAC500 before you buy, or to make sure you have a clear and adequate return policy if you buy sight (sound) unseen (unheard).

Q I am in the market for a DVD player. However I am not interested in DD/DTS because I haven't found a suitable centre for the PSB Stratus Gold. Do you know of a DVD player with good analog performance? Or better yet, do you know of a centre speaker to match the PSBs? I currently use the Chiro C-800 in Pro Logic and must admit that I prefer it to receiver digital surround setups.

A Assuming you have listened to the PSB center channel speakers and don't care for them, try the B&W CC6 or the Mirage. If you are getting a DVD player, it would be best to have DD/DTS capability in the back of your mind for the future. That is what DVD players are really for. Pro Logic sounds better to some listeners because Pro Logic makes use of a much larger bitstream when it is decoded from laserdiscs, and it is decoded from two channel analog when using VHS tapes. However, DVD two channel analog comes from a two channel DD track on the DVD, rather than a high bit rate two channel track. So, it would be better to use 5.1 DD and DTS when playing DVD movies.

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