Q&A # 237 - July 18, 2001

Staff

Q Why do component video cables need 75 Ohm plugs? Isn't component video an analog signal?

A Component video sent to a projector or TV from your DVD player is analog, while the signal from a CD transport to a DAC is digital. However, both component video and digital signals are in the megahertz (MHz) frequency range. So are composite video and S-Video signals for that matter. That is why the old style antenna wire for an over-the-air broadcast reception is 75 Ohm. If the impedance of the connection is less than 75 Ohms, as many inexpensive cables have, the high frequency signal can reflect back into the cable at the connector junction, causing smearing. Having the connection higher than 75 Ohms, e.g., 110 Ohms, is not good either. It has to be 75 Ohms. Here is a link to an article that discusses video signals      http://www.cybertheater.com/Tech_Archive/YC_Comp_Format/yc_comp_format.html.

Q I have just set up my new system. I have the following:

Yamaha RX-V800
Pioneer DVD 414 (optical connect out with S-Video)
Digital Cable box (AT&T) - (cable connect to TV and RCA monster cable to Receiver)
Sanyo VCR (mono connect to TV)

When I first tested the speakers and DVD, everything performed well. I cycled through all the devices to see all the connections were working properly before I settled everything into the entertainment center. Now (the same day) when I view the cable TV, the audio is only heard through the center channel. If I use the DVD, I still get the 5.1 and everything sounds great.

Any ideas on why I only hear one speaker with the cable?

A The fact that it is coming from the center channel only, means that you have a mono signal. If it were only coming out of the left or right speaker, that would indicate one of the stereo cables is not connected. But, since you get it in the center, you have both cables connected, but it is mono. Check all your menu settings for the jacks you have the cable box outputs connected to on your receiver. Try connecting the cable box outputs to a different set of inputs on your receiver too. Since your VCR is mono, try disconnecting it from your receiver.

Q  I have a pair of Infinity Minuette Satellite Speakers which have frequency response 200 Hz - 20 kHz. Is this good enough to connect them for Front Effects of a Yamaha DSP-AX1? Will I lose some sound effects below 200 Hz, since the DSP-AX1 just delivers the frequencies below 90 Hz to the LFE (Subwoofer). Is that the reason why I can't hear the sound between 90 Hz - 200 Hz? I use B&W DM603 S2s for the mains, DM601 S2s for the rears, CC6 as the front center, and ASW1000 as Sub. What is a suitable rear center? Can I use a CC3 (or any suggestions)?

A The front effects channels are derived from the other channels, and appear to contain mostly some reverberation information that focuses in the midrange band. So, I think your Minuettes will be fine. In fact, I don't think the front effects were ever intended to be sent to anything but a set of small speakers. The CC3 should make an excellent rear center.

Q Because I enjoy many of the DVD-Video concert DVDs out there today, I am very interested in DVD-Audio, but disappointed in the lack of bass management shown by the first generation DVD-Audio players. I would think the majority of 5.1 systems in homes today are similar to mine and DON'T have full range front and surround speakers. Due to space limitations (and spousal acceptance factor), I have mini-monitor speakers all the way around and a great subwoofer to handle the bass. I want to add DVD-Audio, but I guess I'll just have to wait. What are you hearing from the equipment manufacturers as to their plans to fix the DVD-Audio bass management issue in second generation players? Anything coming out later this year that will apply proper bass management to the 5.1 outputs from the DVD-Audio player?

A Bass management is a thorny issue, because THX has stringent requirements as to what can be offered and still have THX certification. However, that seems to be loosening up, and better bass management is on the horizon. Both the Theta Casablanca II (currently under review here) and the Meridian processors have excellent bass management, but it is for digital inputs. That is because when the input is digital, DSP can be applied in a straightforward way before sending the signal to the DAC. When the incoming signal is analog, it would have to be converted to digital first, using an A/D converter, and that gets expensive. For mass market receivers, the 5.1 inputs needed by DVD-A just use the volume controls. No DSP is available with the 5.1 analog inputs. The 90 Hz crossovers for bass management in players and mass market receivers is just not good enough, as you say. We need crossovers for 40 Hz, 50 Hz, 60 Hz, 70 Hz, 80 Hz, 90 Hz, and 100 Hz at least. Because DSP chips can incorporate these things easily, it is just a matter of the manufacturers adding them to the programming. New DVD players are being released in August and September, so we will just have to wait and see what they offer, but I suspect it may be the third generation of DVD-A players that incorporate even barely satisfactory bass management.

Additional Comments by John Kotches: 1) One of the problems with DVD-A is insufficient DSP horsepower to do both the MLP unpack and bass management in the digital domain. Once the DSPs have sufficient horsepower to handle both within the time allocated, we'll see bass management in the digital domain. Personally I think it'll be 2003 before the DSPs with sufficient horsepower are in consumer players / processors / receivers.

2) Digital transmission of the signal is still not standardized for DVD-A, and even if it were, item 1 still applies.

3) Analog solutions from Paradigm, Mirage and (very soon) Outlaw make bass management doable if you can live with the number of cables.

Q I have a Yamaha DSP AX-1, B&W DM603 S2 (Main), DM601 S2 (Rear), CC6 (Center), and ASW1000 (Sub). Is it OK to set the mains, rears, and center as large? If not, what is the best setting for them?

A Yes, set them to "Large", and set your subwoofer crossover to 50 Hz.

Q I have a HK510, and I'm running 901VIs for my fronts, IL36c Infinity for my center  and my old Bose AM5s for surrounds. I just purchased a Velodyne CT20 sub. My question is how do I hook the sub up in order to bypass the 510's crossover and rely on the sub's internal crossover alone? And also if you could recommend a good pair of surrounds, I would appreciate it.

A The only way to do this is to use the HK510's Rec-Out jacks to your subwoofer. They are full range with no crossover. Get another pair of 901VIs for the rear.

Q I have two questions I would like to ask. First, I have an M&K MX-150THX subwoofer I bought two years ago. When the installers hooked it up, they used a splitter, and made a connection to both left/mono and right low level inputs. I haven't been able to make heads or tails of the manual, so I have always wondered if this was a correct way to connect it. Secondly, my wife has been bugging me to get a second satellite receiver for our bedroom. I've been thinking of moving my existing RCA receiver upstairs and upgrading with an HDTV capable receiver. I am wondering if I do that, will my existing receiver work with the HDTV dish?

A If the installers just took a single cable to the subwoofer, and split it so they could connect both the right and left input jacks, that is unnecessary. A splitter is usually for connecting a single output to the inputs of two separate amplifiers, such as with two subwoofers. An HDTV dish (oval shaped) will receiver regular satellite programming as well as HDTV, and it will work with both of your receivers. The old dish (round) would not work with the HDTV receiver. Make sure you get a dish with dual LNB rather than just one LNB. You need a separate LNB for each receiver. (The LNB is the component that sits on a rod in front of the dish, and collects the radio signal from the satellite that is focused by the dish.)

Q I just recently purchased Monster Cable's HTS 5000 Power conditioner/surge protector. I purchased it so that I could hopefully protect my gear, improve performance, and possibly eliminate a slight hum problem. The heart of my home theater A/V system is Sunfire's Cinema Grand, Theater Grand II, Sony's KL-53XBR45 RPTV, Carver TCBM-15 2x100 wpc, HHB 850 CDR, and
Polk's PSW-1200. I have several other components (turntables, DVD, VCR, LD, Mixer/pre-amp, etc, but these aren't necessarily hi-end expensive).

I have two concerns: First, a salesman told me that the Monster Conditioner could "limit current output," thereby weakening my system's performance. He said a previous customer complained about this problem while using Mark Levinson amps. Monster confirmed that it could be an issue, so the salesperson said. Is this only a problem if I am running electrostatic, ribbon, or magneplanar speakers? I use 8-ohm speakers all around.

The other concern is that I wish to plug all of my really expensive gear into this power conditioner. Can a typical home outlet withstand such a load just because it is run through a conditioner? The expensive components (amps, TV) all have large power consumption ratings (>300W). I would actually love to plug everything into the power conditioner, but I don't wish to overload the circuit. By the way, the conditioner hasn't arrived yet, so maybe this part of the question would be answered upon reviewing
the accompanying manual.

A If you want to plug everything into power conditioners, I would suggest buying more than one. It sounds like you would overload the single conditioner with all that equipment. I realize this is an additional expense, but it is minor compared to what you have spent on the components. Electrostatic speakers (ESLs) draw only a minimum amount of current themselves. It is the amplifier needed to drive them that draws the real current. Ribbon and planar magnetic speakers don't draw current on their own.

� Copyright 2001 Secrets of Home Theater & High Fidelity
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