Q&A # 155 - January 3, 2000

Staff

Q I'm looking for a 4.7 Ohm 10W resistor for a crossover, and can only get a 7.5 and 12.5, each rated at 12 W. Would the resulting difference of 0.01 Ohm make  an audible difference? Also, please explain what differences in performance the wattage values make.

A I'm assuming that you're putting the resistors in parallel, resulting in 4.69 Ohms to the nearest hundredth. Will that 1/100th of an Ohm be audible? Not a chance. In fact, you'd be lucky to get a 4.70 Ohm resistor with that kind of tolerance, since a 4.7 Ohm resistor with a 1% tolerance would be anywhere from 4.65 to 4.75 Ohms. The difference in output would be far below 1/10th of a dB under the most extreme circumstances. Don't worry, you're fine. As for the 12 watt rating vs. 10 watts, that's simply the power handling capacity of the resistor itself. That's not to say that the speaker which is hooked up to that part of the network will never be able to get more than 10-12 watts, since the power absorbed will be only a fraction of the total. For a ten watt spec, it sounds like a tweeter attenuator, or perhaps part of a Zobel network. The difference in power handling won't make a big difference, but if anything, assuming it's non-inductive (only really relevant for the tweeter section), it will be better. When resistors heat up (including the voice coil) they become more resistive. This, in turn, causes dynamic compression (in drivers) and changes the frequency-based relationship between the drivers and the crossover components. Essentially, the more power you feed the speaker system, the more the crossover properties shift, which is generally a bad thing. On the other hand, if you're playing music that loud, a slight change in crossover slopes may not be that noticeable compared to the ringing in your ears the next day. But, the higher the power-handling capacity, the less the element heats up, and the lower the effect. All in all, no reason not to use the combination that you mentioned.

Q I see that now there are some progressive scan DVD players now hitting the market. I assume for SD and HDTVs. I recently bought a DVD player and am in the process of building up a DVD library of classic and other movies that I enjoy. When digital TV becomes the standard and high definition DVD players are out, will I need to replace all my software? Will the movie studios bring out their old movies in some kind of new high definition format? In other words, I'm wondering if it is a smart thing or not to build up a movie library right now.

A Digital audio and video offer so much more possibilities for change than analog, I think we are going to see a non-ending progression of advancement. DVD may go to 720p, but probably not for about 5 years. The studios and consumers are just now getting the library of 480p material. If you wait, you will not be able to enjoy your classics for several years. Not only that, but once 720p DVD gets here (if it does), there will probably be some other thing on the horizon, perhaps 1080p DVD. So, go ahead and buy your DVD movies. Live for the moment, as they say. Also, don't forget, a progressive scan DVD player will show your current library of DVDs on an HDTV with a much better picture than you are seeing now. We will be reviewing some of these products soon, and the image is superb.

Q I currently have a Sunfire Cinema Grand 5 channel amplifier. I wish to upgrade to a Cinepro 2k5 II or 3k6 II. Is there much difference between the Sunfire and the Cinepros in regards to quality output? Is it worth upgrading?

A The Sunfire uses digital switching, while the Cinepro is a Class A/B amplifier, but they are very similar in sound and in price. If you want to upgrade, go for the Sunfire Cinema Grand Signature or Cinepro 3k6II, both of which will give you a lot more power than what you have now. The 3k6II has a sixth channel in case you want to go for Dolby Digital and DTS 6.1 sound, which some receivers for the year 2000 have.

Q In your opinion, which surround speakers for today's movies (for Dolby Digital or DTS) provide the best and worst results? 1. Direct radiating 2. Bi-rads (i.e., radiating from one left and one right side) 3. Dipoles (radiating front and back) 4. Bipoles (radiating front and back) 5. Omni poles (radiating all over?) Where should these speakers be placed?

A This was probably more of an issue when we only had Pro Logic, but with full range digital sound, it is really just a matter of how you like your sound. I like to use the same type of speakers in the rear as I have in the front, if not exactly the same models. Otherwise, the surround soundstage doesn't sound right. The more direction of radiation, the more diffuse your sound will be. You can experiment with this a bit by placing your two front speakers back to back and facing them front/back or sideways, and then connecting one speaker in phase or out of phase with the other (by reversing the binding post connections on one speaker). You need to use a mono signal for this experiment. This will give you an idea of bipolar vs. dipolar sound.

Q I recently purchased an SD-2109 DVD player and noticed that it has some audio output at 96 kHz. The manual for my Sony SDP-E800 Dolby Digital decoder says that "it is only compatible with digital components using 32/44.1/48kHz sampling frequencies. It is not compatible with 96kHz." Can I use the Sony to decode the audio from the Toshiba or are they really incompatible?

A Some DVD players output 96 kHz digital bitstreams, but most do not. However, your DD decoder specifies that it will not decode 96 kHz bitstreams, so it does not make any difference. However, your DVD player will decode the 96 kHz bitstream into two-channel stereo analog, so just use the analog jacks from your DVD player to your receiver (not the decoder) for 96 kHz discs.

Q I am purchasing my first home theater system for a studio apartment, so I am looking for smaller surround sound speakers. I am willing to invest approx $1,200 for the 5pc surround speaker system and receiver. I want to be able to enjoy clear sound at low volume, and I want to enjoy renting movies without having sound distortion. A sales rep recommended the Jamo surround package Apollo, with an Onkyo TXD5474. Would this be adequate for my needs? Do you have any recommendations?

A Jamo and Onkyo are fine. Just make sure that whatever receiver you buy has built-in Dolby Digital and DTS decoding (as opposed to "DD-ready").

Q We recently decided to purchase our first DVD player and this has led us to the decision that we are going to replace our 19 year old receiver (Vector Research VR-1000) with a new A/V receiver. We have narrowed our search down to one of the 100-105W/ch receivers (Onkyo Integra DTR-7, Nakamichi AV-10, Denon AVR-3300). We are also replacing our 14 year old CD player (Hitachi DA-501) and speakers (Bose SE-5). It is the search for speakers that we are having our most difficult decision-making. We both enjoy music to a greater extent than movies, so we have been searching for a couple of towers for our front speakers for both music and HT. Surprisingly, we both enjoy the addition of a subwoofer (even for music), especially when the crossover is set quite low (50 - 60 Hz). We have also enjoyed the use of a center speaker, as it puts the main part of the movie sound around the TV (the old 2-speaker stereo never came close). It is during the use of the rear/surround speakers that both of us become quite annoyed. In virtually every demonstration of a movie's surround sound, both of us found the sound coming from the back or the side quite annoying and unnatural. We have spent several hours in closed rooms watching and listening to movies and find the use of rear/surround speakers disturbing at best. We are probably in the minority on this one, but we have come to the conclusion that we would rather spend extra on the other 4 speakers than to purchase all 6 speakers. In numerous setups where the surround sound actually came from the front speakers we found this to be quite enjoyable and natural sounding. Even some of the people who listened to our preferred setup were surprised to find that the rear/surround speakers were turned off. We have decided on speakers made by a company called Canton. While we are not really familiar with them, we found their entire line of speakers to be thoroughly satisfying in all aspects of music listening. Our original intent was to purchase their AS-25 Movie pack, which consisted of 5 small, nearly full range (40 Hz - 30 kHz) speakers (Plus XL/AV 400) and a 10" subwoofer (AS-25). Given our recent movie listening experiences and our preference for music, we are deciding on 2 front towers (Ergo 92 DC), a center speaker (Ergo CM 51), and a subwoofer (AS-30) that will cost 50% more than the 6 speaker setup, but to us, the sound these speakers make is worth it! We are quite excited about the new A/V receiver, CD player, and DVD player. We are wondering, though, whether our decision to skip the rear/surround speakers will cause us a problem in the future? Even beyond our current dislike for the "surround" experience, our room's layout does not provide a side or rear wall to place the surrounds. A ceiling mount is also out of the question (for aesthetic reasons). Do you have any reason why our decision is not a sound one (no pun intended)? Are there any pros/cons you can give to our proposed setup?

A I see absolutely no problem with your choices. Plus, if you decide later on to add the surround speakers, you just connect them to your receiver and away you go. Most receivers have various modes that will allow you to combine all the sound into the front three speakers. Just check your instruction manual to see which ones do that.

Q I recently started building a new home theater system. I've purchased the following equipment: Denon AVR-1600 digital surround receiver 60w per channel, Pioneer DV-525 DVD player, Polk Audio CS-150 center channel speaker, and an ASC-BSW powered sub. My television is a Mitsubishi CS-27205, which I plan to replace when funds allow. My front main speakers are Pioneer CS-R590s from my old system which I need some advice in replacing, (price range under $400). Also, I need some advice on rear channel speakers. So far the system looks and sounds good except for a humming noise coming from my TV. The noise is really noticeable during low volume or silent parts of movies. I turned off each component one at a time and narrowed it down to the TV. I turned the TV off and the noise went away. Is this harmful to my system? If not, it's still very annoying. One last problem I have with my TV is thin light blue horizontal lines about an inch apart across the screen. It's not noticeable when viewing movies in standard view, but when watching in letterbox, the blue lines are visible in the black bars and during scenes with low light. Your comments and guidance would be appreciated.

A I suspect your problem may be interference from the cable TV connection (assuming you have one). Try disconnecting the incoming TV cable and see if that eliminates the hum. If so, then get a ground isolation device that goes between the incoming cable and your TV. Mondial makes one that can be purchased from Audio Advisor.

� Copyright 2000 Secrets of Home Theater & High Fidelity
Return to Q&A Index.