Q&A # 269 - December 27, 2001

Staff

Q  Could you tell me if you re-calibrated the monitor used to judge the players for each player? Based on your review of the Panasonic RP-56, I purchased one and found the output between interlaced and progressive to be quite different in terms of contrast and color saturation. The progressive appears "washed out." I can adjust the picture controls on the Pioneer SD533, but wonder if what I am seeing is normal or if my DVD player is defective. The interlaced output appears quite similar to the Sony it is replacing. Of course no one in any local electronics store can give me a straight answer and Panasonic has not answered my e-mail.

A Yes, we re-calibrate our display with each output of a DVD player and with each and every DVD player. We cover this very issue in Part 1. The interlaced and progressive outputs follow different video standards and have different video levels. Even with that in mind, most DVD players fail to follow the standards. Why? Perhaps they want their DVD player to stand-out from another.

Q I am considering purchasing a Denon 3802 receiver for a customer in a home theater setup. My question is this, what is this 7th channel used for? What and where do I place speakers for it? I can't seem to find any answers to give to my customer about its use.

A When THX-EX and DTS-ES became available in home theater receivers, 5.1 became 6.1. The extra mono channel goes in the center rear, and is extracted from the rear left/right. There really is no such thing as 7.1, because the seventh channel is synthesized, but let's just call it 7.1 for simplicity. For some receivers, such as Yamaha of a few years ago, there are two front effects channels that go to the sides of the front left/right. For recent "7.1" receivers, the two extra channels go in the center rear with the original rear surrounds going in the rear left/right sides. This allows some decorrelation to be performed between the two center rear channels so that EX and ES presented in those two speakers will have more depth than if they were just both mono (like the old Pro Logic rear channels, which were mono and identical in both speakers unless decorrelation was performed). So, depending on the receiver (whether or not its 7.1 means it has EX and ES), the 6th and 7th speakers go in the center rear, with the regular rear surround speakers going to the rear but off to the sides.

Q I like the sound of the B&W 600 Series 2 speakers, but I am not sure which speaker as well as what subwoofer size and power would be appropriate for my room requirements for both music and HT listening. Would the LCR6 S2 for front, center, and surrounds with a nice subwoofer work, or will I need to go to a 3-way floor-standing model for the fronts with a quality subwoofer? The room they will have to fill is 20'x20' with 18' vaulted ceilings. The walls are log and the floors are wood so am not sure how this will affect the sound.

A With a room that big, I would suggest nice big floor-standers and also a big subwoofer (15" - 18"). Set the low-pass on the subwoofer to about 40Hz - 50 Hz. You should use area carpets on the floor, and perhaps some corner room absorption pillows in the upper corners of that vaulted ceiling.

Q I was just reading Brian Florian's article on the LFE channel and a question arose. I agree that listening to a system at 85 dB is too loud, but should you calibrate the system to 85 dB and then just turn the volume down or should you calibrate the speakers to a lower dB level?

A Correct calibration depends on what you're calibrating from. For internal tone generators and Video Essentials, the correct level is 75 dB for all channels. These tones are generated at -30 dB vs. Full Scale Signal. Avia is at -20 dB vs. Full Scale signal. Calibrate to these standards, then playback to volume of your choice after you've calibrated to the standard. This is a consistent way of communicating, as in "I listen at -15 dB vs. Reference". If you vary the calibration level, you no longer adhere to the reference, and what levels are out there become murky.

Q I have read a lot about power amplifiers having bridge mode. I can see some advantages and disadvantages with using an amp this way. Obviously one is that it increases its power delivery by taking its four ohm stereo rating and doubling that rating into an eight ohm single channel load. A disadvantage would be the cost of using a multi-channel amp for one channel. Are there any sound quality improvements with bridging? With the exception of the super amps, I have seen several amplifier manufactures that offer a bridge mode but state when bridging the amplifier not to drop the impedance below eight ohms. My understanding is that a speaker with a rating of eight ohms nominal impedance will drop well below eight ohms at a given frequency. Does this make bridge mode really not useable in some cases?

A The option of bridge mode is really just a convenience factor making the product more flexible. For example, a six-channel power amp that has bridging mode will let you use it to drive six speakers, or three speakers with bi-amping of the woofer and tweeter in each of the three speakers, or bridging to give you three powerful channels. Bridging turns the amp into sort of a balanced amplifier, but the decreased low-impedance drive characteristic could result in less depth to the bass, although you could also end up with less noise (common mode rejection) if your AC lines are really noisy. If high power is the most important factor to you, then buy a more powerful amplifier that does not require bridging to give you the power you want.

Q What qualifies and/or are the characteristics of a loudspeaker designated as a "studio monitor?"

A This is a designation of the Pro Market, where the speaker is used in a recording studio to play back what has just been recorded. I think it has been adapted to the consumer market just because it has a nice sounding name. The pro speakers are likely in a plain black enclosure. The consumer version has the same drivers but a nicer enclosure finish (veneer). Pro speakers are designed for loud volume so the studio can play the recordings back at a level that approaches the live musicians. This could result in the speakers not doing so well at low volume, so you have to choose carefully.

Q How do you set the crossover frequencies on a receiver? I have a Sony STR DE925. Bass is 100 Hz to 1.0kHz, mid 500 Hz to 5.0 kHz, treble1.0 kHz to 10 kHz.

A These settings on your receiver are EQ (tone controls), not crossover frequencies. Crossovers are for sending just high frequencies to tweeters and low frequencies to woofers, or subwoofers.

Q I just bought a 65" wide screen TV a Samsung Model HC1652W. I currently use my XBox to play DVDs, but it is not progressive scan. My TV automatically displays everything in 480p. Would buying a progressive scan DVD player make that much of a difference if my TV already displays it in 480p?

A Yes, a progressive scan DVD player would make a difference because your TV does not have 3-2 pull-down detection, and some resolution is lost when the player converts the digital video to an analog interlaced signal and your TV has to reconvert it to digital for deinterlacing and then goes back to analog.

� Copyright 2001 Secrets of Home Theater & High Fidelity
Return to Q&A Index.