Q&A # 129 - July 28, 1999

Staff

Q As a long time home cinema enthusiast, I have from time to time experimented with rear speaker placement. It seems to be very difficult to get an even spread across the room with only two speakers, no matter whether I place them to the side or behind me. I believe Lexicon and Meridian processors have outputs for an additional pair of rear speakers, but I wonder if this is possible to achieve on lesser equipment like my Sony STR-DA50ES coupled with a Chiro C-500 amp. If I split the rear channel output from my receiver, using two phono Y connectors and use an additional 2 channel power amp, would it work? And also, why limit this to just two pairs of speakers? If you have a really large room, would it not be better to literally surround yourself with rear speakers, just like in a movie theater?

A I think what you are looking for is more dispersion of the rear channels. This has become more of a problem with DD and DTS than it was with Pro Logic, because digital surround provides stereo in the rear, with some very discrete sound effects. You can achieve more dispersion, and a wider soundstage, using several methods. One is to put the rear speakers farther away from your sitting position. If your couch is near the rear wall, then try putting them farther to the sides. Also, try aiming the rear speakers towards the center of the room rather than directly at the couch. Another method would be to use dipolar or bipolar speakers. The last resort would be to use additional speakers as you have suggested. You could do this two ways. One is to just add another pair of speakers to your current receiver's rear outputs, but you should first try wiring the speakers in series rather than in parallel. Otherwise, your amplifier might be overdriven. The other way is to split the outputs and add the second amplifier as you mentioned. As to the movie theater setup, remember, you HAVE a movie theater at your home. Commercial theaters compromise the speaker arrangement due to the large audience. That is why they have so many speakers. They need to make sure everyone gets some semblance of surround sound. With all the great products available to consumers now, we can easily obtain a much better sound at home than at the commercial theater. Sounds like you are on your way to doing just that.

Q This question comes to you from far-away India. I am planning to buy the Yamaha RX-V795 receiver. I was told by the dealer here that the Yamaha NS-70 speakers would not be appropriate for the receiver since the speakers have a 6 Ohm impedance while the receiver expects speakers of 8 Ohm impedance. This sounds ridiculous since a lot of home theater speakers seem to have 6 Ohm impedance. The Yamaha also has a high current capacity so it should be able to handle the lower impedance, shouldn't it? I would value your comments on this. My second question is: The Yamaha web site lists this amp as having a max power output of 125W (x 5). Most reviews I have seen on it say it has a power output of 85W (x 5). Which is the correct figure? What power output should an ideal set of speakers for this receiver be able to handle? Can I use, for instance, the Tannoy Mercury M3 speakers for the front and rear speakers?

A Regardless of the correct specifications (probably 85 watts), you should use speakers that have no less than 6 Ohm impedance. The receiver does not "expect" any particular impedance. It will just perform better with 8 Ohms than 4 Ohms, if you turn up the volume. Speakers of 6 Ohms should be fine, especially if they are high efficiency (90 dB/w/m or higher).

Q I have a question regarding room size versus speaker size. I currently have my stereo in a room that is approximately 12' x 13'. I recently bought a pair of Klipsch KLF20s (1" tweeter, 1.5" midrange, two 10" woofers, 100 dB sensitivity). I am using my old Klipsch KG4s for rear speakers (1" tweeter, two 8" woofers on the front of the speaker with a 12" passive woofer on the back), a Klipsch KLF-C7 center channel speaker (1" tweeter and two 8" woofers), and two subwoofers (a 15" and a 12"). I have a Yamaha RX-V795 receiver. My question is whether or not, in general and all other things being equal, the sound quality of the system with speakers of this size might be better in a bigger room. I could put the stereo in a room that is approximately 11' x 24', but before I take the time of disconnecting, moving and reconnecting everything to check, I thought I would ask your opinion. I realize that neither room has good dimensions for home theater, but those are my choices.

A Going to the larger room will allow you more flexibility in getting a larger soundstage, but there is no reason why you can't have perfectly good surround sound in a room 12' x 13'. The bass would also be somewhat deeper in the larger room, by putting the subwoofer farther from your sitting position. Midrange and treble will not likely be affected though.

Q In your DIY article on the Thrifty Thumper, it mentions running a powered sub from a head phone jack. Is this a good idea? I have a Yamaha 396 amp (50w) and was thinking about a sub, but this would rob my main speakers (Tannoy M2s - nice bass, but I want some punch) of power. Therefore, I was wondering what the limitations were of the headphone jack method (good sound quality, etc?). Or could I run the sub from the CD player headphone jack?

A Headphone jacks usually come from inexpensive op amps, but the nice thing about using them for your subwoofer setup is that the main volume control changes the output on the headphone, so you would not have to be manually adjusting the subwoofer each time you change the main volume. Otherwise, if you use the rec-out jack, where the volume control does not affect its output, you have to reach behind the subwoofer and adjust the volume there when you change the main volume control. Headphone jacks don't have very good sound quality, but the bass is not as affected as the mids and highs, so you should be fine using it with your subwoofer. In case there is an impedance mismatch, however, you should listen for any problems with getting enough output in the subwoofer. If this happens, then use the rec-out from your Yamaha.

Q I have a Yamaha DSP-A2070 amp. it only supports Pro Logic. I would like to upgrade with a Yamaha DSP-E492. What's the scoop?

A The E492 is for receivers that only have two channels or for receivers that do not have a set of 5.1 input jacks. Plus, it does not decode Dolby Digital. It only makes your system DD-Ready. You would still need a DD decoder, such as the Yamaha DDP-2. If the 2070 does not have the 5.1 inputs, then the E492 will be fine for your purposes, as long as you remember you still need the DD decoder. However, the 492 only has 60 watts of amplifier power, which is not very much for Dolby Digital purposes. The 492 plus a DD decoder is going to make your system complicated with a lot of wires going every which way. I would suggest just putting your money into a new receiver that already has DD and DTS built-in. You will have more power, more features, and a heck of lot more comfort.

Q Is PAL / NTSC a factor in DVDs themselves? I know that one must have a PAL player to work with a PAL TV and an NTSC player for NTSC TVs. But I wish to know if the DVDs themselves are produced to work only on one system or another.

A Yes they are. The MPEG video on DVD is stored preformatted for either PAL or NTSC. There are a few differences between the two systems. First is picture size and pixel aspect ratio (720 x 576 for PAL and 720 x 480 for NTSC),. Secondly, the frame rate is 25 FPS for PAL and 20.97 FPS for NTSC. Third, the audio is MPEG for PAL and Dolby Digital for NTSC. There are DVD players out there that will play both formats. They do some converting on the fly, but they work. Most PAL players will output Dolby Digital, but US players will not output MPEG. The Meridian 800 can convert both ways, but it is on the higher end of the price scale, and I am sure there are much more affordable players out there to do both.

Q I am moving into a new house and need a new TV. The sitting room is 13' x 15', and I'll be watching TV across the 13' part. Can you tell me what is the minimum and the optimal size of TV I should get? I am looking at a Sony FD 36" Trinitron or a rear projection (no  idea which one is good). Since I have a surround system, I don't really need all the fancy features and would like to either save some $$$ or get a better/bigger picture for my money.

A Lets take a look at your 13'. This is the length of your room, but how far back from the wall or TV will you be sitting? The rule of thumb is 3 - 6 times the screens height (how far back you should be). If you have a trained eye for video, you probably will not be happy unless you are 8 times back. For most, 4 times is a perfectly acceptable distance. Otherwise, your big screen looks small from such a large distance back. This is for a standard NTSC TV to avoid seeing the line structure. If you had an HDTV system or a line doubled picture then you can cut that number in half (in other words, you can sit closer). If for example, your TV is 2' deep, that only gives you 11' from the TV, providing your couch or chair is against the back wall. Since most TV sizes are given in the diagonal measurement instead of the height, you need to slightly alter the formula. Instead of using height, you can use diagonal, so you multiply the diagonal measurement times 2.4. If you are going for a 36" 4:3 TV, 36 x 2.4 gives you 86.4" or 7.2'. If you can get up to 10' back, you will be very happy with a 50" 4:3 TV. These are just suggestions though. Measure how far back you are going to sit and then take a tape measure to your local video store. Once there, measure the distance back from the TVs you are interested in and watch them for a while. Spend 20 minutes looking at the picture, not 20 seconds. Are you going to be using DVD? If so, look for a TV with component (not to be confused with composite) video inputs. If you are going to watch a lot more standard TV and movies on the weekends, you might want a 4:3 TV. But if you get a 4:3 TV, try and find one with the new "squeeze" feature. The new Sony Wega TVs coming have this feature. It allows you to get the most out of DVD without going to a 16x9 TV.

Watching letterboxed movies on a 4:3 TV makes me want to sit closer. I used to have a 60" rear projection TV, and when I watched heavily letterboxed movies on it, I would sit so close, I could rest my feet on the base of the TV. I decided that in the future, I would find the TV that I liked the best when shopping, and then buy one size larger.

Q I read Stacey Spears' August '97 review of Toshiba's TW40F80 and was wondering if you had any information about a new TW40 coming out this summer/fall? I understand that the current TW40H80 is due to be replaced with a model that is HDTV ready. Any information about this model?

A I read about the 40" replacement a few months back, but we have no details at this time. I did hear the MSRP would be around $2,999. I doubt if it will support 720p, which for sporting events, is a must.

� Copyright 1999 Secrets of Home Theater & High Fidelity
Return to Q&A Index.