Q&A # 137 - September 6, 1999

Staff

Q Can you explain to yours truly and a lot of Home Theater folks why the Motion Picture Studios are releasing most of the newer DVD movies in widescreen only? It really bothers me that they are getting away with this practice. If Secrets were to phone let's say 200 average purchasers who bought DVD players and ask them if they prefer to watch movies in widescreen or pan and scan (using the whole viewing area on the TV), I'm sure the numbers would be very high for using the whole screen. In the beginning, the first 100 or so DVD movies gave the consumer the option to watch either widescreen or normal viewing (pan & scan), but nowadays it's hard to find any. WHY is the big question???? I personally want the option to choose. I really feel that the studios don't care what the buying public think or they wouldn't be on this widescreen-only trip. So, I hope you will do a random survey and publish it. Then and only then will the studios wake up and start to give us (the buying public) what we want , not what they want.

A Surveys have already been done, and most people do prefer P&S, or whatever it takes to have the image occupy the entire TV screen. However, as you know, modern films are widescreen, which means that the only way to fit the entire image, the way the director intended, is to show it as a rectangle inside the 4:3 NTSC TV screen. Directors want the movie to be seen that way, as that is the way they made it for commercial theaters. It is very expensive to produce DVDs with both versions on the disc. That, plus the fact that HDTVs are 16:9, means that P&S is doomed because the 4:3 image will have blank areas at the sides when shown on a 16:9 TV, like the blank areas at the top and bottom when widescreen movies are shown on current TVs. At that point (HDTV), consumers will probably prefer the widescreen images.

Q I'm experiencing a 60 Hz hum coming from my center channel speaker (B&W HTM Matrix). It occurs whenever I turn the TV on, and the center channel amp is not even on. I disconnected the speaker cable from the amp, but the hum is still present. I don't know what is causing this problem. The HTM Matrix is on top of the TV. Another question is about using the crossover of my sub and pre/pro at the same time. I have a pair of Velodyne F-1500R subs which don't have a defeatable crossover. I am using B&W 805s for the front and an Acurus ACT3 as pre/pro. The problem is that I can only defeat the ACT3's crossover if the front (L,R) speakers are set at full-range which is a no-no for the tiny 805s. One dealer told me to just set the subs crossover to the highest frequency (120 Hz) and the problem is solved. Is this true or not?

A The hum in your center channel speaker is caused by the high voltage 60 Hz in the TV. It is inducing the hum in the speaker, so that is why it occurs even when the center speaker is disconnected. The speaker voice coil is acting like a secondary coil on a transformer. You need to shield the speaker from the TV (that is something you don't see mentioned very often!) You can do this by placing a steel cookie sheet under the speaker, or try raising the speaker above the TV a few inches by placing some paperback books under it. Once you see how much height is necessary, you can make something more attractive for a permanent placement.

Don't worry about using two crossovers in your pre/pro/sub configuration. I have not found that using two crossovers in series makes any significant different for the really low frequencies that are pertinent to subwoofers. However, I would suggest upgrading to the bass management feature on the ACT3 if you don't already have it, and then setting it to a low-pass of about 60 Hz out to the subwoofer. Then, as your salesperson mentioned, set the low pass on the sub to 120 Hz. This will minimize interaction between the two crossovers in the 60 Hz and below area.

Q I just got a pair of the original Carver Amazing speakers. The model with 2- 30" ribbons per side. I have a few questions for you about them. First, the person I got them from thought that there was a platinum crossover upgrade that I could install. Is there such an upgrade? Also from what I have read, the bass drivers have a very high Q. I was surprised by the lack of bass from them. I have seen pictures of the Amazing"s woofers, and they looked like regular drivers with a big surround and tiny magnets. My drivers have flat piston type cones with an aluminum appearance. And shouldn't the surround material be very light? Mine is quite normal. Almost like they have been replaced. If the other drivers I saw are better, can I swap them out? Finally, these speakers seem to need lots of power. Is there anyway to make them bi-ampable, so I could use two amp channels for each side? If you guys do not know or are busy could you point me in the right direction. The one site I found that repairs the ribbons, never responds to my e-mails! The reason I am asking you is because nobody else seems to know or respond.

A It sounds like you have one of the earlier models of the Amazings. Nevertheless, they are really great speakers. When I bought mine (the Mark IVs) years ago, I also got one extra ribbon and two extra woofers. But, I never have needed them. The reason for the design of the drivers is that the enclosure is open in the back. This results in a considerable amount of cancellation, but the overall speaker is slanted to help reduce this problem. I did read about a crossover modification, but trying to find one now that it has been years since they were manufactured will be difficult. Instead of going inside the existing crossover and trying to modify it for bi-amping, I would suggest just getting a more powerful amplifier (since the speakers are no longer manufactured, it would be a real problem for you if something went wrong and you needed new components). The Amazings need about 200 watts per channel to drive them properly. Bob Carver is in the middle of putting the Carver Corporation back in business, so you could contact them once they are open and running again. They may have some spare parts here and there.

Q I have a home theater setup that uses a Yamaha 793 receiver, two Bose 10-2 4 Ohm speakers, 2 Bose 2-2 rear speakers (8 Ohms), a pinnacle center-wide speaker (8 Ohms) and a pinnacle 250 watt powered subwoofer. The room in question is approximately 14 feet wide by 19 feet long with 8 foot ceilings. I also have a Toshiba 3107 DVD player. My question involves amplification. I have been generally satisfied with the sound, but I sometimes feel the setup is lacking when I really crank things up for an action DVD. The subwoofer seems up to the challenge but not the rest of the system. Should I replace the Yamaha with a more powerful receiver or add an amplifier as the Yamaha has pre-outs? If an amp is the suggestion, what would you recommend (possibly not much more than $1,000?)

A I suspect the 4 Ohm speakers are your problem, so I would suggest getting an outboard two-channel or three-channel power amplifier, rated at 100 watts per channel or greater. Adcom, Rotel, AudioSource, and others, make very nice two and three-channel power amplifiers in your price range. The new Outlaw Audio five-channel amp is sold only on the web, and as a result, it is also in your price range even though it is five channels.

Q What is ground loop hum and does it make the amp hum or the speakers? Is this the same as when hum is caused by a running electric motor? How is this dealt with? I live rurally and have heard that because of this I probably do not need a power conditioner but what is it that I do need? Whenever an electric motor is turned on anywhere in the house whether it is on the same circuit as the stereo or not, there is a loud hum coming from the amp. What can I do to fix this problem?

A Ground loop hum is caused by having several components all connected together (such as DVD player, TV, Receiver, Amplifiers), and the ground potential (voltage) is not the same in all of the components. As a result, current flows along the ground connection in the interconnect cables where it is not supposed to, and the current contains 60 Hz. You will hear this type of hum in your speakers. There is also 60 mechanical hum in transformers caused by such things as electric motors and variable brightness lamp rheostats. AC line conditioners can help sometimes, but there is no guarantee. We are testing a new design now that converts the incoming AC to DC then resynthesizes 60 Hz AC, and we will report on this soon.

Q I am thinking of upgrading my current home theater system by buying a pair of new front speakers and using my current front floor-standing speakers as rear speakers. The question is where to put these floor-standing speakers. My current rear speakers are mounted on the rear wall, so could I put my floor-standing speakers against the rear wall? If so, because the floor-standing speakers are lower than the sofa back, would the sofa back be a problem by shielding the sound from these floor-standing speakers? What's the ideal place for these rear floor-standing speakers?

A The couch may indeed block some of the sound, so I would suggest putting the speakers to the side of the couch rather than behind it. Aim the speakers towards the center of the room.

Q I recently added a DVD player to my home theater. I have always been impressed with the bass in Pro Logic mode with video cassettes. Upon adding the DVD and switching to the 5.1 analog inputs, the bass is reduced to almost nothing. After experimenting with speaker sizes, DVD processing strategies, switching between line-level or RCA sub connections and other decoder "tweaks", there was no improvement. However, after I switched to the L/R line outputs alone and using Pro Logic mode, I again have considerable bass. Why can't I get it with DD?

System:

Polk Audio RT12 (front)

Polk RT8 (rear)

Polk RT300 (center)

Polk PSW150 (sub)

Technics SA-AX720 (receiver)

Sony DVP S530D

A Many DVD players have bass management built-in, particularly the ones with 5.1 analog outputs, so you should check the settings in your DVD player to see how the LFE bass is being directed and if it has a menu to set the output level, as opposed to just looking at speaker size, which redirects the bass in those channels to the subwoofer. By your comments, you may have already done this. Since the two-channel analog outs are a downconversion from the 5.1 DD, the bass is in there somewhere, so it is a matter of finding out where it is going. If your DVD player is redirecting the LFE to the front left/right channels, for example, and your receiver is set to front left/right speakers being "Large", this could remove a lot of the bass from the subwoofer output. Set all speakers to "Large" in the DVD player menu as well as the receiver, and make sure the LFE setting in the DVD player is set to "On" if your receiver has the 0.1 analog input. If it does not, then set the LFE in the DVD player to redirect it to the front left/right.

Q I live in a small NYC apartment, and am trying to put together a home theater system that is space friendly (not to mention spouse approval). I currently use a Yamaha DSP-A3090 as my processor. My main speakers are Krix Esoterix 1 Mk 2s, and my center speaker is a Krix Centrix. I use a Yamaha MX-1000 amp to drive the main speakers and a Accusonic MB-400 mono amp to drive the center speaker. I plan to use the internal amp of the DSP-A3090 to drive the front and rear surround speakers. Which brings me to my question. What is your opinion of in-wall speakers, and are there any you would recommend I listen to?

A There are lots of nice in-wall speakers, but you would be taking a real chance putting them into an apartment owned by someone else (the landlord). Also, once you got them in the wall, you might not like the location. So, I would suggest getting some of the new flat panel speakers designed to go on the wall rather than in it, such as the Infinity FPS-1000 speakers. That way, if you like them, fine. If you don't like them, it is just a matter of packing them up and taking them back to the store. In-wall speakers leave the hole when you remove them. Flat panel speakers easily can be taken with you when you move.

� Copyright 1999 Secrets of Home Theater & High Fidelity
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