Q&A # 202 - October 24, 2000

Staff

Q I am confused about harmonic distortion. You said that a lower THD can sound worse than a higher one if it is a result of using lots of negative feedback. How can lower distortion be worse?

A Negative feedback will lower the Total Harmonic Distortion (THD), but it can increase higher order odd harmonics. So, although the actual number may be lower, say 0.005% compared to 0.1%, the increased amount of higher order odd harmonics will make it sound irritating. For example, here is a wav file that I made using a 500 Hz fundamental, along with the 1 kHz second harmonic, 2 kHz fourth harmonic, and 3 kHz sixth harmonic (Click here to download). Now, compare that to the sound of the 500 Hz fundamental, with the second, fourth, and sixth harmonics lowered, but with the addition of the seventh harmonic (odd ordered) (Click here to download). That seventh harmonic makes the sound very unpleasant, even though the other harmonics have all been lowered. This is what happens when lots of negative feedback is used. Although the THD spec goes down, the sound is worse. Mass market receiver manufacturers have been the major culprits in the past, but they seem to be getting the message, as I have seen marketing sheets that state they are toning down the use of all that negative feedback.

Q I am interested in purchasing an A/V receiver in the $275-$325 range.  Could  you recommend a product in that price range that is a good value? I would like it to include Dolby Digital and a good DAC. I am looking for the best sound for the money, so extra convenience or bells and whistles are not  important to me. I also wish to purchase a DVD player in the $200-$300 range, again only interested in the image and sound quality. Any suggestions about that? I use just a regular 24" monitor television and do not see any  upgrades in the near future to a high resolution TV or big screen.

A The best place I have found for receivers and DVD players in this price range is CostCo. They buy them in such quantities, the price is always rock bottom. At this point, the receivers all have DD and DTS built-in, and the DVD players all output DD and DTS, so you really can't go wrong. They tend to carry two models of receivers and three models of DVD players at any one time, but the turnaround is very fast, so if you see something you like, get it then and there. Next week, they might be gone.

Q I presently have five identical full-size speakers (MBQuart D55s) in my 5.1 setup. I have a pair of 12" subwoofers for the LFE. I have an extra D55 in case I ever upgrade to a 6.1 system (since the Newcastle 9080 does have a 6  channel direct feature). A friend advised that I take the center channel off the top of my TV, and instead run the center channel in series/parallel with two centers flanking the TV. Since the D55 is rated down to 28 Hz, if that manufacturer's statement is to be trusted, what possible benefit is there to using two centers?

My friend says that it just sounds better but cannot justify it. He first heard about it at a hi-fi store, but I don't much respect their opinion - it just seems like they want you to spend money and they try to give you the more-is-better bug whenever possible. I think it would look terrible among other things. Unfortunately, my hearing is not good enough to immediately discern anything but a real difference. But really the reason that I have not tried it is that the speakers are not fun to move around and rewire the way this little room is set up. Plus I am too much of a novice, and I'm  certain to create too much or too little of an impedance somewhere. So 
before my lazy butt even tries this, I would like to hear about a hypothetical benefit.

A There are a couple of reasons why it might sound better. One is if you really play movies loud. Having each center speaker doing only half the work would improve their distortion characteristics. A second is if people in your family tend to sit in a wide array. Putting the two centers so that one covers the left side and the other the right side could help. But, if your D55s are good speakers, and you don't play the system really loud, I don't see a benefit.

Q I am wondering if I have my system hooked up right? The video output on my VCR is connected into my TV's Video Input 1,
and the audio output of my VCR is connected to my AV receiver (Video 1 input).  Why is it when my VCR A/V output is connected straight into my A/V receiver (Video 1 input) and the (Video 1 output) is connected to my TV's input, I get the sound, but no picture?
A With the setup as is, you need to select Video Input 1 to get the picture, since you are feeding that input on your TV directly from the VCR. Select the Video 1 input on your receiver to get the sound. To make it more efficient, run the video output from your VCR and the audio output from your VCR to the Video 1 input on your receiver, and run the video output (usually called "Monitor") on your VCR to the Video Input 1.

Q I am an apartment dweller, and though I have vowed to wait until I move into a house to build the Ultimate Setup, I must have a quality system on which to watch movies. I was avoiding getting a DVD player and a surround sound system for fear that I would just about be all consumed with getting the ultimate system now, instead of waiting. I am going to be getting a Sony Playstation 2, a videogame system with DVD capabilities. (Before anybody scoffs at me, it has an optical out, which for me was enough considering I mostly wanted it as a videogame machine anyway.) In anticipation of this, I  have recently purchased a Home Theater in a Box setup made by Kenwood  (HTB-453). I was pretty proud of the purchase, since I managed to save myself from going over the deep end on the system. It's clear enough for me,  and although not earth shattering with a 50w subwoofer, it won't get me kicked out of my building. It doesn't have DTS decoding, but at $250 less than the Home Theater in a box which has the DTS decoder, plus, many friends suggesting to me that I can live without DTS, I'm pretty happy with it. Now, I am  currently looking for a new TV, since my current one does not have an S-Video input. To add to my madness, a RPTV is not out of my budget, since the company I work for has an arrangement with a certain manufacturer.

I read though the primer, and there was mention of RPTVs having a problem keeping the RGB aligned over 100% of the screen. I was wondering if this was just an older article, or if RPTVs are still known to have this problem. The model I am considering is the Panasonic PT-61G54. I have been unable to find anything on it except on the Panasonic website. Are there any opinions on
it? Also, care to make any conjecture about the Sony Playstation 2? Since it is a second generation machine, I figured it would be adequate as a DVD player. The fact that they included an optical output kind of eased my questions about whether it was a "serious" machine. Any comment on the fact that it uses the same laser to read DVDs and CDs? I am really curious to hear what
serious Home Theater Enthusiasts have to say about a machine that will hopefully close the gap between Video Game consoles and Home Theater.

A Projectors that have the red, green, and blue coming out of three separate lenses, such as CRT projectors, will always have a little problem with complete alignment since they are projecting from three different angles. Projectors with only one lens, such as the LCD and DLP projectors, don't have that problem. In any case, the issue is minor. CRT projectors still give a superb image. There are some Rear Projector LCD and DLP units out there now, so you should check into them. The DLP projectors, in particular, will give wonderful brightness.

We have a writer working on a review of the Playstation right now, and another writer working on articles for computer use in Home Theater. Using the same laser for CD and DVD does reduce the quality of CD performance. For your current system, it probably will not be noticeable, but later on, you will want to have a dedicated CD player or DVD player with dual lasers.

Q Recently in your Q& A section, you wrote: "We have also started to see inexpensive gadgets that convert composite to
S-Video so that you can connect all your components to the S-Video jacks on  your receiver and switch in the one you want to use, so that the final signal  comes out of one S-Video jack to your TV. On most receivers, you can't route an incoming composite video signal (VHS VCR) to the S-Video output from the  receiver that goes to the TV. But, keep in mind this is strictly for convenience in switching your sources. It will not improve the signal."  Who makes these "inexpensive gadgets" converting composite to S-Video? I
can' t find any. I need one for my VCR, and one for my cable box. I am tired of getting up and hitting tv/video on the TV.

A Here are some links for them:(1) http://www.svideotorca.com/videoware/rcatosvideo.html  (2) http://www.audioadvisor.com/product.cfm?productid=3282  (3) http://www.homs-smarthome.com/8290.html (4) http://www.besthometheater.com/c2sconverter.html.

Q I am currently using a Yamaha DSP-A1 as my amplifier, but I also have a  Rotel RB-976 that I am not using. I was wondering whether using the Rotel in one of its modes (5, 3, 2  channels) would improve the performance, or if the Rotel would not change anything or even degrade the quality? Am I right to think that the 2 or 3 channel mode would be the best to use? My main stereo speakers are Monitor audio MA-202 (possible bi-wire), my center a Castle Keep, and my surround Castle Richmond.

A Yes, you can use the Rotel 976 to improve the sound, and you might be able to do this in a bi-amp configuration by removing the bus bar that connects the tweeter and mid/woofer on the rear of the Monitor Audio speakers, and using the speaker output from the DSP-A1 to drive either the tweeter or mid/woofer and the Rotel (bridged to 150 watts per channel) to drive the tweeter or mid/woofer (connect the pre-out jack on the DSP-A1 to the Rotel). It is critical that you remove that bus bar on the speakers first though, so don't forget to do that.

Q I have a pair of D1200si MBQuart subwoofers. It is my understanding that having two subs increases the LFE by 6 dB rather than 3 dB. And I read one of your posts which said that having two subs is better because they do not have to work as hard as one sub to get the same bass. When does diminishing returns kick in? I might have a chance to get a third sub relatively cheap. Maybe I should just save the money and try to get one of the Velodyne 15"s that I see recommended here.

A Use of two subs will indeed increase your potential output by 6 dB, but placement is very important. Otherwise, you can actually get a reduction in power because the two subs work against each other rather than with each other. You have to experiment with the placement. Sometimes, just stacking one on top of the other works best. Make sure the phase switch on both is at the same setting if you put them one on top of the other.

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