Q&A # 261 - November 1, 2001

Staff

Q You mentioned that the McIntosh MC-602 works well in a home theater. Is it really beneficial to have all that power?

A Yes, because movie sound tracks for action films tend to be very dynamic. If you use an average of 5 watts per channel for a typical part of the movie, and the volume is at 70 dB, it may go to 90 dB during an action scene (explosion, gun fire, etc.) The additional 20 dB require 100 times as much amplifier power as at 70 dB, meaning 500 watts. If I were installing a custom home theater for someone, I would have no hesitancy to put in three MC-602s. I couldn't afford that for myself, but there are a lot of people who can, so why not have bottomless power?

Q Below you'll find a tip listed on someone's website which from what I've read seems counter to what should be done when setting the subwoofer low pass filter level & counter to what you guys reccomend.  So what's up with this tip of theirs?

"A common mistake made when adding a subwoofer to a video system is to duplicate the low pass filter, thus dramatically changing (for the worse) the sound and transient response of the sub.

Most surround processor have a separate subwoofer output that includes a crossover slope. That is, the sub output on a surround processor is already rolled off, containing no high frequency information. If you place this already rolled off subwoofer information into a subwoofer input that is not specifically designed for this type of output (most are not), you will then wind up with two roll-offs, giving you results that are less than optimal.

The easiest way to make sure this is not a problem, is to turn the subwoofer's low pass filter control up as high as it will go. By turning the control to its highest frequency setting, only the roll-off built into the surround processor's subwoofer output will be active and the two will not interfere with each other.

Some video processors allow you to turn off the internal roll-off of the processor allowing you to use the built in one on the subwoofer itself.

In most cases, however, it is easier and preferable to simply turn the roll-off of the subwoofer up as high as it will go, which is usually
around 120 Hz."

A This procedure works fine as long as the processor's low-pass frequency is what you want, such as 50 Hz. Mass market receivers have low-pass frequencies that are too high though, e.g., 120 Hz, 90 Hz, etc. So, in that case, you would have to set the subwoofer's low-pass to something more reasonable, such as 50 Hz, so that it won't sound boomy. Keep in mind that this assumes you are not crossing over your speakers in the other channels to that 120 Hz. If you are, then the sub's low-pass should be turned all the way up. Otherwise, you would have a hole between the receiver's crossover and the subwoofer's crossover.

Q I am considering purchasing B&W's HTM1 center channel speaker. Your strong review of this product has convinced me that this is a wise upgrade. My question to you is this - will this center channel fit on top of a Sony 36" direct view TV? The speaker weighs over 45 pounds. Also, the depth of the speaker measures over 12" - will it fit without a custom built shelf ? I read your review of the B&W HTM2 and also know that this is an option. I am looking forward to your feedback.

A With a 36" TV, it should fit, but I would suggest making a cutout of the base dimensions of the speaker and taking it to a dealer to make sure it will fit on top. Remember also that the slope of the TV might make it tilt too far backward, and you could need to put something underneath the rear of the speaker to make it tilt at a lower angle. I use rubber bumpers (they look like half a rubber handball) to accomplish this on my TV.

Q  I have a Toshiba SD-5109 progressive scan DVD player (Colorstream). I am considering purchasing an In Focus Data/Video projector that is HDTV compatible (1080i and 720p). Can a projector that isn't made for Colorstream still up-convert the signal? In any event, should I expect images near the quality of two Colorstream compatible products or something much less?

A Colorstream is just Toshiba's marketing term for progressive scan video. It is no different than the progressive scan signal from other brands. You are going to have a ball with the player and projector. Progressive scan looks fantastic on the big screen. Put the projector where it will be on a permanent basis and use a bed sheet to see where you want the image and how big it will be. Use the sheet for a while and make sure you are happy with that size, say over a period of two weeks.  Then order the screen to fit that size image.  Regardless of whether you feed the projector progressive scan or interlaced, it will show a progressive scan image on the screen. It would just take the interlaced signal and de-interlace it. Try it both ways (progressive output vs. interlaced output from the player) so you can see the difference.

Q I have a Sony 10HT projector and am feeding it 720p from a scaler. In doing this, I found I cannot adjust the aspect ratio on the projector. Why is this so?

A In 720p mode, the Sony locks into 16x9, as 720p is always a 16x9 format. You will not lose resolution if you change aspect ratio on the scaler - the Sony samples at a much higher resolution for 720p signals than it does for 480p signals.

Q I currently own a Toshiba SD-9100, and know that there have been numerous new models released, both on the high-end and budget-end of the spectrum, and I am wondering what are the major advantages I would see if I upgraded my current DVD player. I am not as worried about HDCD capabilities, but trying to get an idea if the sound and picture technologies have greatly improved on the DVD players since I purchased my 9100, to the point that it is worth investing in new equipment.

A The basic picture and sound are much the same as they were several years ago, taking into account individual player advantages and disadvantages compared to one another, which is the case now as it was then. There are a handful of features that are worth upgrading to, assuming that you want those features. One is DTS capability, one is progressive scan video, and one is DVD-A. I am talking in general terms here, not just with respect to your specific player. If you don't have an interest in these features, then don't upgrade. The picture and sound were great when DVD players were first introduced.

Q I'm using my digital cable box to select channels and to view the guide info provided by my cable vendor (Cox Communications). Thus I first run my cable outlet into my cable box and then feed my TV the RF output of the cable box. Am I degrading my cable signal by following this path or should I somehow feed the TV (using its tuner for channel selection) first from my cable outlet (sacrificing the guide info)? The only other outputs on the cable box are R/L audio out and a composite video out. Would this composite video output provide a better picture than the RF output in my current setup?

A Yes, if you have composite video jacks on your TV, use the composite video out from the cable box rather than the RF connection. You will still see the program guide. Even better, use the S-Video out from the cable box if you have an S-Video input jack on the TV. Connect the audio R/L output jacks from the cable box to the TV also, for the stereo audio.

Q  I have been experiencing what can only be described as intermittent hum bars when viewing DVDs in progressive output mode on a Sony DVP-NS700P DVD player connected via component input to a Hitachi 43UWX10B HD monitor. There is no set pattern as to when they appear, and cannot be reproduced on the same scene twice. It does not matter if the DVDs are anamorphic, non-anamorphic, 2.35, or 1.85. They are very closely spaced and roll from bottom to top. If I pause the DVD player while this is happening, the speed at which the bars roll actually slows down, almost to the point of stopping. When I hit play, they speed back up. However, when I switch the DVD player into interlaced mode, the problem does not occur. I can actually switch back and forth between progressive and interlaced modes and see the bars come and go respectively. I took the first unit back, as I thought it was probably defective. But, the second unit is doing the same thing. This almost sounds like what people were experiencing with the Denon 2800 when they were first released. I have not heard any other complaints or recalls for the Sony DVP-NS700P. This is very annoying when it occurs. It is hard to see in brightly lit scenes, but is most prominent in darker scenes. And again, it only happens randomly. Sometimes I can watch an entire two hour movie and never see it. Could this be some kind of incompatibility with the Hitachi monitor and the Sony DVD? Or could it be something else? I have all of my components plugged into a Monster Power line conditioner, so hopefully that should be filtering out any kind of electrical fluctuations. It's just really weird that it does it in progressive mode but not interlaced mode.

A Yes, I have seen this problem too, and on a Toshiba DVD player, so it is not specific to any one brand. I found that it was being caused by a ground loop between the component video cables and the analog audio cables coming out of the DVD player. When I disconnected the analog audio cables, the video hum bars disappeared, when viewing progressive scan DVD. I use a Toslink optical digital cable to carry the digital audio from the DVD player to the processor, so the ground loop cannot travel through there. If your player only has digital coax output, you may need to get a coax to Toslink converter, assuming your receiver has Toslink digital input for the audio. This brings up another question that we get very often, namely whether coax or Toslink digital cables are better. I have not found one to deliver better audio than the other, but Toslink sure cures some ground loop problems now and then.

� Copyright 2001 Secrets of Home Theater & High Fidelity
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