Q&A # 121 - June 22, 1999

Staff

Q My name is Chris and I have come to a fork in the road. Seven years ago I purchased a Carver CT-17 preamp, TFM-15 amp, SD/A-350 CD player, and two Dahlquist-28 speakers with the intention that I would be able to add to this system in the future to complete an excellent surround sound effect. I have only now just been able to do this, and have concerns that completing the Pro Logic surround system might not be the best move. I have faith in Bob Carver, which was a deciding factor in purchasing his products, so I ask for your help/advice. Is Dolby Digital superior to Sonic Holography, it would seem so to me? Can I purchase a Dolby Digital decoder to complement my current system? Should I scrap my current system, or what are the most useable components, and what purchases do you suggest for modest home-theater with the potential to update/increase the performance? In other words, I don't know how to update this system in the present environment, and don't want to waste money. Can you help me please?

A Sonic Holography is one of Bob's inventions for giving two-channel stereo more depth and presence. It is a very cool feature that I hope he resurrects on some of his new products. However, DD is a completely different animal, being discrete five-channel sound. Sonic Holography could be applied to it, but we will have to wait and see what he does. In the meantime, I would suggest getting a DD/DTS receiver that has pre-outs, like a Yamaha RX-V795, and using your TFM-15 power amplifier to drive a pair of speakers in another room.

Q I have a Denon POA-T3 power amp connected to my Denon AVR3600 receiver. While the receiver has a remote power on/off switch, the power amp does not. Given that I use my stereo 3 days X 4 hours a week, should I leave the power amp turned on all the time or should I turn it on only when I use it? Is there danger in wearing out the amp if I choose one over the other? Can you please let me know which option will prolong the life of the power amp?

A There are several options here. One is to leave the power amplifier on all the time, which should not hurt it at all. Secondly, you can turn it on and off each day just as you do the receiver. This won't hurt it, but I assume you are asking the question in part because you don't want to manually turn it on. Lastly, you can buy an AC line conditioner that has an auto turn on feature. The Rotel  RLC-900 does this, at $199. It lets you use the switched AC outlet on the back of your receiver (make sure there is a switched outlet as some receivers have only unswitched outlets) to activate the line conditioner, which then turns on your power amplifier. You plug your power amp into the line conditioner and the line conditioner into the AC wall outlet. The receiver also has to be plugged into the wall outlet, or a surge protector that is on all the time, so it can turn on the line conditioner. Regardless of which method you use, your power amplifier will not suffer. The only type of amplifier that I would recommend always turning off after you use it is a tube amplifier.

Q I have a question on the delay time setting for AC-3 processor. My processor is the Technics SHAC500D which has both AC-3 (DD) and DTS decoding. It has both center and surround channels delay settings. The manual simply says that to add 1ms delay for every foot difference in distance relative to the main speaker, e.g., if the difference between the surround and main speaker distance is 10 feet, then add 10ms to the surround delay. But how should this distance be measured? Should it be (A) a direct "line-of-sight" distance from my listening position to the speaker location? Or (B) the horizontal distance regardless of how high the speakers are mounted? "A" will be greater than "B" in this case, as I mounted the surrounds about 7 feet from the floor level. I noted for either case that the delay setting will round up/down to about the same number, given that the processor surround delay time setting is only available at every 5ms intervals from 0ms to 15ms. But I just wish to find out how the sound wave really travels.

A What the manual is referring to is the difference in the distance from your listening position to the front speakers compared to the distance from your listening position to the rear surround speakers. Let's say it is 10 feet from your couch to the front speakers and 5 feet from your couch to the rear surround speakers (line of sight, whether they are on a stand or on the wall). Because your surround speakers are 5 feet closer, you need to delay the sound coming from those rear speakers by 5 milliseconds. So, you would choose the 5ms setting. Since you have settings in 5ms increments, just choose the one that comes out nearest to the calculated number. But, the final analysis is the listening. If there is an echo kind of sound to the movie, then change the delay up or down one setting and see if the echo is decreased. Leave it at the setting with the least amount of echo.

Q My current speaker's are Polk's RM5300 sub satellite system which are powered by a Yamaha RX-V2095. I use the system for both music and home theater and am interested in upgrading the speakers because I am not satisfied with the sound in the mid to lower frequencies. I do not have a lot of room for main speakers which is what attracted me to this system. Further, my listening room is irregular so it works well to have smaller main speakers that are wall mounted and can be pointed to the main listening position. I think that the crossover frequency between the satellites and sub in this system is over 150 Hz. Can I replace the sub in this system with a true subwoofer and expect a significant improvement?

A I would say probably not. Subwoofers don't perform very well in the above 100 Hz range due to their large box size. They sound boomy and chesty in that range. Also, the sound above 50 Hz becomes directional, and this can seriously mess up the soundstage, which is what I think you are finding objectionable. So, I suggest getting some bookshelf type speakers that you can live with, and which will respond well in the > 70 Hz regions. Something like the B&W DM-602s would be great, although they would be a little more difficult to put on the wall. However, if you want better sound, that is the sort of thing that has to be dealt with. You will probably also have to get a different subwoofer, something like a Sunfire or Velodyne HGS-10, and set the low-pass to about 50 Hz.

Q Do I need to spend a decent amount of $$ on speaker wire to run my NHT 1.5 surrounds, or is gauge the most important factor?

A Speaker cable does make a difference, but it will be less so with the rear speakers since they are primarily used for effects. If you want the least expensive cable, then get 14 - 16 gauge zip cord. It's about $10 for a 100 foot spool at electronic supply stores. Otherwise, something like Nordost 2-Flat (that is what I use for the rear surrounds) is excellent, and it is about $2/foot.

Q I have a Sony STRDE925 digital receiver, and my main and center speakers are 8 Ohms, while my rear speakers are 6 Ohms. Should I set the switch to 4 or to 8 Ohms on the back of my receiver?

A If it had been your front speakers that were 6 Ohms, I would have said set your receiver to 4 Ohms. But since it is your rear speakers that are 6 Ohms, and the rear channels do not have a lot of high intensity sound going to them, you can set your receiver to 8 Ohms.

Q I'm currently looking to upgrade my Home Theater receiver. The problem is, I don't know which way to go. For a budget of $2000, should I get a higher end receiver or low/ mid priced separates? Sound quality is number one in my selection criteria. I could go a little over the budget if the sound quality justifies. I'm curious about the B&K AVR202, DENON AVR5700, and NAD T770 (if it offers DTS). Now, since I'm getting serious about this stuff, so I'm thinking that maybe I should get some low to mid priced separates instead. I saw in the ads some attractive five-channel amps like Rotel RB-985 and Carver AV-705x for roughly the same price and less than $1,000. For the preamp, I don't know yet. In your opinion, what would sound better: 1. get a high end receiver from B&K, DENON, etc., or 2. get the separates using one of the amps I mentioned above and buy a pre/pro that costs $1,000+? By the way, I'm using four B&W CDM1 SEs, CDM CSE (center), and ASW 1000 (subwoofer).

A For $1,000 you won't find much selection of preamp/processors that have DD and DTS, along with many features. So, keeping your $2,000 budget in mind, I would suggest getting the Denon AVR-5700 if you can find it for that price, or getting something like a Yamaha RX-V995 at $1,000 and the Carver AV-705x to use with the pre-outs on the 995. Either way, you will have the quality sound you are looking for.

Q On a few DVDs I have noticed that the audio and video are slightly out of synchronization. This can be annoying with closeups of people talking, giving the impression of a dubbed foreign film. Is this a problem with the transfer of the movie to DVD, a problem with my specific copy of the disc, or with my equipment? I have a Panasonic DVD A310 player with built-in DD decoder and a Yamaha RX-V990 receiver using the 5.1 channel inputs.

A Movies often have a difference between the image and the voices because we sit 30 feet or more away from the screen in commercial movie theaters. If this is not compensated for in the home version, the sound of voices arrives before their mouths speak it. You can take care of this problem by increasing the delay for the center channel in your receiver.

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