Q&A # 167 - March 8, 2000

Staff

Q Do I need a dedicated line for my A/V gear? The line I'm using now is also shared by a washing machine/ dryer and four 75W bulbs. Is it true that I cannot plug the power amps and the low power gear (DAC, pre/proc, CD player, etc.) on the same outlet, if so why? I also have aMmitsubishi WT-46805 RPTV and used the Video Essentials DVD to calibrate the TV. Do I still need an ISF technician to calibrate the TV?

A You only need a dedicated AC line if you are having problems such as tripping the circuit breaker. Most of the time, a separate line is not necessary. Noise will not necessarily be eliminated with a separate line, because they are all connected together via the neutral conductor back at the breaker box. If you are happy with the results of your own calibration, further calibration is not required.

Q I have some electrostatic speakers, and every once in a while, I can hear a popping noise if the volume is loud. What is it, and how can I fix it?

A Electrostatic speakers are sensitive to the humidity levels. When the humidity is very low, they can give off a popping noise at high volume. The membranes move close to the stators during loud passages, and there is an arcing of electricity from the membrane to the stators. To combat this, try using one of the misting humidifiers that increase the humidity without increasing the temperature in the room. Don't put it close to the speakers though. You just need to humidify the room a bit.

Q I have a Pioneer Elite AX-99 receiver with coaxial input for Dolby AC-3. My DSS satellite receiver has an optical output (none of the DSS receivers I checked had coaxial outputs). Is there a way to connect the two?

A There are converters available. Here is a link to get you started: Digital Cable Format Conversion http://www.minidisc.org/part_Digital_Cable_Format_Converters.html. 

Q I recently purchased a Hitachi 50EX39R projection TV, and was wondering if it's safe to play video games on it? The reason why I ask is because there's a warning in the Sony Playstation manual which states: "Unless your projection TV is an LCD type, do not connect your "PlayStation" to it without first referring to the user manual for the TV. Failure to do so may cause permanent damage to the TV screen." So would you happen to have any advice as to whether it would be safe to hook up a Sony Playstation to this projection TV?

A With your TV set in its default contrast position, video games can damage your TV, so can MSNBC, the home shopping network, and anything else that displays a fixed logo on the screen. If you want to play video games on your TV, you need to use Video Essentials or Avia to properly adjust the contrast setting. By doing that you will:

1. Get longer life from your TV

2. Probably get more detail from the picture because it is no longer blooming.

3. Be able to watch TV and play games without worrying about damaging your TV.

The bottom line though is just turn the brightness and contrast down from the way it is set as default when you first brought it home and turned it on.

Q I'm relatively new to audio and own an old set of Sonab 3-ways with six tweeters each that I rebuilt myself. I've never seen a design with more than four tweeters each before, and more than one is rare nowadays. It makes more sense to have just one, but is it just a matter of personal taste? I have limited money and want a secondary set for movies and stuff. The ones I have my eyes on are Pioneers ($320) that have a 12" woofer, 4" midrange, and a 2 1/2" paper cone tweeter. I like high notes, so is this going to sound bad? I had a pair of Klipsch bookshelves with a 1" soft dome tweeter and I loved them. Should I just wait until I can afford more elaborate speakers?

A Some of the finest speakers in the world only use two drivers, a tweeter and mid/bass, so it is not the number of drivers that makes the speaker good. Having several tweeters makes the sound more diffuse, so that it does not sound like it is coming from just one spot, but that is not necessarily good. It all depends on how well the speaker is designed. A paper coned tweeter can sound just fine, but you need to listen to them and then decide if you like them. Don't go on specs alone.

Q I recently bought an Onkyo TX-DS747 A/V receiver and am very impressed with it. I might also mention that it was a demo and half the retail price. I am running the sub out from the Onkyo into my old NAD 7080 receiver which is providing around 90 watts to a Gauss 8842 18" driver mounted in a very large acoustic suspension box with an 18 mH (millihenry) coil for filtering. My main channels are old JBL L030s which were built from a kit over 20 years ago. They sound really good with the new receiver. Also connected to the system is a Denon DRW-840 cassette deck, a Hitachi DV-P250U DVD player with the digital coax linked to the Onkyo, and a Hitachi UX615 Hi-Fi VCR. The JBLs and the sub are both very efficient speakers. I intend to purchase a mono amp to bring about 300 watts to the sub at some point. My question is what kind of center channel and surrounds should I be looking at, given the above info? I want dipoles for the rear channels. The JBLs use a 15" extended range driver and a bullet tweeter - would a center channel speaker with better midrange be a good idea. The speakers sound very good right now, and the sub complements the JBLs very well. Should I remove the coil from the sub if I am running it from the sub out on the Onkyo? Also, what type of speaker cable would be recommended for the JBLs and the sub?

A You will need to find a center and surrounds that are very efficient, in order to match volume levels with your other speakers. This narrows the list to other JBLs or perhaps Klipsch and a few other brands. For the subwoofer, the crossover frequency out of your receiver may be too high, and in fact, you might have to change the value of your inductor in order to get the right low-pass frequency. With the speakers you mentioned, it should be about 50 Hz, and I suspect the low-pass out of your receiver is much higher than that. So, first just listen to your system as is, and if it is boomy, calculate what your low-pass crossover frequency is and get the appropriate inductor for a low-pass crossover of about 50 Hz. We have given the formula for calculating this in a previous Q&A.

Q I've owned a pair of Adcom GFA-565 monoblock power amps for almost ten years now, driving a pair of M&K S-1B sats. I've sold the sats - time to move on - and bought into a pair of B&W 805s for my two-channel enjoyment. Visually, these are great looking speakers - if you're into design looks - , as well as great sounding. My primary question is that of speaker power handling. The Adcoms are 300 watts into 8 ohms. The B&Ws are rated at 120 watts power handling, 8 ohms. I do enjoy jazz at 9 - 10 o'clock volume dial levels. Am I still looking at a good match?

A Yes, I would say you are in good shape. Speakers can handle lots of power when it is clean. The problem comes when you try to crank the volume and the amplifier clips, which is not the case in your situation.

Q I'm considering using a Yamaha DSP-A1, which I currently own, as a preamp for a Rotel RMB-1095 five-channel power amp. My question is will I get a great improvement in terms of sound quality from this combination?

A You bet you will!. Although the DSP-A1 has very good amplifiers, all mass market receivers will be improved by using a good outboard five-channel amplifier, and the Rotel RMB-1095 is one of the best we have seen (we reviewed it recently).

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