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HINTS & TIPS

 

TAKING A STAND
I have recently purchased a set of Wharfedale Pacific speakers and have given no thought at all to positioning of the centre speaker, which unlike most other centres sits fairly high at approximately 10.5inches. It is quite bulky and I am worried about placing it on top of the TV. Few TV racks I’ve seen allow for the fact that many people have a DVD, VCR and amp as well as a centre speaker, particularly if it’s a tall one like mine.
Nick Kenny

A

AV furniture makers have an unenviable task, trying to accommodate the virtually limitless permutations of TVs, audio and video components and speakers and to make matters worse the size, shape and weight of all these things keep changing. Layout is also constrained to some extent by the TV, which restricts the height of the top shelf so that the centre of the screen remains at eye level, all of which leaves relatively little scope for designers to play around with shelf heights (see Quick Tip). Putting the speaker on top of the TV is usually a bad idea. TV cabinets these days tend to be quite thin and usually slope downwards, making anything on top unstable. Even if it stayed put it will probably block the ventilation holes.

 

If the TV is close to a wall you could mount the speaker on a shelf or bracket behind the TV or if you are handy with a saw and hammer you might like to have a look at the following web site (http://www.seanspot.com/ht/Tosh-Shelf/Tosh-Shelf.htm), which has plans for a simple speaker shelf that fits on top of the TV.

 

 

QUICK TIP

If you can’t find an off-the-shelf (no pun intended) AV rack to suit your setup or living room then why not have a chat with a local cabinetmaker or AV specialist? A custom or bespoke cabinet or shelving system can be made to fit in with your décor, it will make the best use of the space available and could even improve the sound of your system. It may not be as expensive as you think – provided you avoid too many exotic materials or design flourishes – and you’ll have a unique and hopefully elegant piece of furniture to enhance your living room.

 



IMPEDANCE IMPEDIMENT?

I recently upgraded my speakers to the M&K K Series. The three K-7s performing main/centre duties have an impedance of 4 ohms and the K-5s at the rear are 8 ohms. I am thinking of replacing my current amp with a Denon AVR-8303, Harmon Kardon AVR-5500 or Pioneer VSX-D2011-S. Will any of these receivers drive the speakers correctly? My old Yamaha amp has an impedance switch to make the necessary adjustment but I can't find this option on these receivers' spec sheets.
Ian Forster

A

Those three AV amplifiers are all rated for 8-ohm speakers, so you may have to re-think K7’s or your choice of amplifier if you want to keep everything neat and tidy. Very large impedance mis-matches (i.e. a 2-ohm load on an amp with an 8-ohm rating) can result in distorted sound and in extreme cases it can put a significant strain on an amplifier’s output stages, possibly causing it to overheat or worse. However, in the real world things are generally a bit more flexible, moreover manufacturers numbers always have a little bit of leeway built-in. In other words connecting a 4-ohm speaker to an amplifier with an 8-ohm output stage, and keeping the volume at a sensible level, almost certainly won’t cause a meltdown and there’s a good chance the components will work well together. Obviously it’s not something we can officially recommend, or take responsibility for if they do go up in a puff of smoke, but don’t dismiss the idea before you make your final decision. 

 

QUICK TIP

In an ideal world the impedance of a loudspeaker should be a perfect match with that of the amplifier used to drive it. This will ensure the greatest efficiency in the conversion of electrical power into acoustic energy but in practice this very rarely happens. The impedance of a speaker is a measurement of its resistance to an AC current, but it’s far from being a fixed quantity and can be affected by any number of influences, from the ambient temperature to the type and length of wire used to connect the speaker to the amplifier.

 

 

 

WIDE ASLEEP?
I have just bought a CyberHome CH 402 DVD player. I am using this as a second player in the family room, which does not have a widescreen TV. The problem is that I cannot get the DVD player to play in anything but wide screen. There is a pan and scan setting on the player but when I set it to this option nothing seems to happen and the film continues to play in widescreen with two very large black bars at the top and bottom. I have been using a Sony Playstation to play DVDs on this TV and they all play fine. Is there a problem with the player, i.e. the pan/scan facility not working?
Kendall Metcalfe

A

This machine, like pretty well all DVD players, has the option for 4:3 letterbox, 4:3 pan & scan or 16:9 picture shape. This setting is independent of anything on the disc or the TV the player is connected to and it will be applied to all DVDs played on that machine. The correct picture shape for your television would be 4:3PS (pan & scan), but it may be that the change isn’t being stored because you are trying to do it ‘on the fly’ whilst playing a disc. Have another go, remove the disc and go into the setup menu again and make the change, not forgetting to confirm the setting by selecting the Enter ‘button’ on the menu display.  If it still doesn’t stick then the player has a fault, probably in the firmware (the software program that controls the machine). If it’s any consolation it is a very rare condition, but one that the retailer’s service agent should be able to put right very quickly.

 

 


PUNY PIONEER?
I have a Pioneer NS-DV1 system hooked up to a Philips 32PW9523/25 TV but I think the speakers look puny and don't do the system justice. Are there any you would suggest? I quite like the look of the Wharfedale Diamond 8 speakers but don't know if the system amp will power them.
Dave Rawlinson

A

It sounds as though you are more concerned about the appearance of your speakers rather than audio performance, which is a slightly unusual approach but who are we to argue with your priorities?  In common with most ‘lifestyle’ systems the NS-DV1 relies on a set of small matched satellite speakers in collaboration with a sub-woofer and is designed to work best in small to medium sized rooms. Changing just the front or rear speakers will almost certainly unbalance and possibly ruin the surround sound effect so even if you’re not overly worried about performance you should still change all of the speaker together. Your Pioneer amplifier delivers perfectly reasonable 30 watts per channel into the five 8-ohm satellite speakers and the sub channel puts out 45 watts. Whilst there is no technical reason against it, speakers like those in the Diamond 8 range, which are rated up to 150 watts, are hardly going to get out of second gear and effects are going to lack any real substance. There are plenty of other smaller speaker packages that would be better suited to the Pioneer amp but we’re hesitant to make any specific recommendations without knowing more about your aesthetic preferences.

 

QUICK TIP

Speakers certainly don’t have to be boring black boxes and a growing number of manufacturers are experimenting with more radical designs that not only look stunning and they can also sound fantastic. However, beware of becoming a fashion victim; radically shaped enclosures that blend in perfectly with your current décor may well stick out like a sore thumb in a couple of year’s time when you redecorate. Classic speaker designs and traditional materials might not get the pulse racing but quality and style never go out of fashion.

 

 

LOSS OPPORTUNITY
My DVD and VCR have been stolen, so I need to re-equip but I want to reduce the number of boxes, leads and switches. I have a decent Panasonic 36-inch surround sound TV and don't want three sets of speakers. However, the TV's satellite speakers aren't too impressive, so a central amp/processor and decent speaker system might be required. I want DVD, CD, radio, digital TV (FreeView and/or Sky), X-Box (possibly also for DVD playback?), MP3/video, a hard disk recorder and a programmable remote control and I do not want to have to switch on 15 devices to get the system working,

Peter Gardner

A

One day, who knows all this may be possible with just one box (see Quick Tip) but back in the here and now, you are going to have to put up with at least three components to achieve everything you want. The DVD, CD, tuner, MP3, amplifier, surround-sound functions and speakers are certainly available in one box and home cinema systems like the Toshiba SD-42HK spring to mind. It performs well though the speakers are a weak point and may benefit from an upgrade, but at £300 or thereabouts it is good value. Your digital TV and video recording needs are neatly taken care of with a Sky+ box, though you might still want a VCR if you want to keep any recordings. A DVD recorder is another possibility but given that you’ve already covered DVD playback it would be overkill. We can’t do much about combining the X-Box with any other technologies; true, they can play DVDs but only just and you would still need a separate deck or decks for CD and MP3 playback. One universal remote should be able to take care of that little lot, and something like the One For All Mosaic will do it in style.

 

QUICK TIP

There is a potential one-box solution to home entertainment and that’s a PC. Most recent models can play DVDs, audio CDs and MP3 audio files, and with a big enough hard disc and the right software video recording is also possible. Radio and TV tuners are available as plug-in cards or adaptors and you can also get digital satellite receivers. Several of the more advanced sound cards have surround sound capabilities though you will still need an external multi-channel amplifier. The only downside is the noisy fans, the need for a keyboard and mouse to control everything, and the inevitable blue-screen crashes…

 

 

 

SPEAKERS TO DI FOR?
Could you please advise on a pair of surround speakers to match my KEF Reference 104aB fronts, my amp is a Denon-3801 and DVD player a Pioneer DV626. At the moment I am using a pair of KEF Q15s for the rears. Would I get a better sound buying a pair of dipole speakers?

Vic McIntosh

A

The monopole vs. dipole speaker debate has been going on for years. There’s very good arguments on both sides and there’s never going to be a clear winner, but here’s a few basic points that might help you to make up your mind. Monopole or conventional direct radiating speakers used in a 5.1 surround sound setup are normally placed just behind the listening position. Compared with a dipole setup, and all other things being equal, they will produce a sharper more highly defined soundfield. Purists and sound engineers tend to prefer this sort of arrangement, especially when listening to music, because it allows them to precisely ‘localise’ every sound and instrument in a recording. Monopoles also create a relatively small ‘sweet spot’, which is fine if there are only one or two people watching a movie in an average-sized living room, but it may not be so good for larger spaces and audiences. Dipole speakers are normally placed to the sides of the seating position and radiate the sound forwards and backwards. This creates a larger, more diffuse and enveloping soundfield, which tends to work better with spatial effects on movie soundtracks, like thunder and explosions. Dipoles also do a better job of recreating the ambience of a cinema where several monopole speakers arranged along the walls and behind the audience usually handle the surround channels. To sum up, smaller room, small audience and lots of music then stick with monopoles, larger room and a preference for action blockbuster movies then give dipoles a try.

 

 

DEFINITELY DIGITAL…

Could you tell me whether or not a change to an NTL digital signal will definitely improve my present NTL analogue signal both in terms of picture and sound quality? I have a 42inch Panasonic plasma; and now I have just bought a Phillips DVDR880 DVD recorder and seen what DVD looks like, I realise I have a very grainy picture for most terrestrial channels, therefore even DVD recordings are just as grainy and unacceptable. I have just agreed to try the digital option but NTL was not happy about giving me anything in writing to say my picture quality would definitely be better and seemed cagey about letting me cancel if I wasn't happy.
Trevor Saville

Q

It would have been amazing if NTL had given you anything in writing because picture quality is so subjective (see also Getting Started). This is well illustrated in your case because it sounds as though you have only recently come to the conclusion that your picture is ‘grainy’. Presumably it was acceptable before you acquired a 42-inch plasma TV and DVD recorder. Part of the reason the picture now looks inferior might be due to the fact that it’s a whole lot bigger, and a DVD recorder, unlike a VCR -- which tends to soften a video image -- captures everything, warts and all. In the end it depends on what sort of analogue signal you were getting. On a good day, with the wind in the right direction analogue TV should have sharper, better-defined colours, a wider contrast range, more detailed backgrounds and smoother movement. A digital picture might look cleaner, due to the lower noise levels, but you may notice coarser graduations in colours and shades, static backgrounds can appear to ‘freeze’ on some channels and rapid movement sometimes appears blocky or stuttering, making it look less natural. However, there should be no reason why NTL won’t switch you back to analogue if you are genuinely dissatisfied with the service.  

 

 

QUICK TIP

Cable companies like NTL are keen to encourage their existing subscribers to migrate from analogue to digital and it has comparatively little to do with improvements in picture and sound quality. The fact is digital cable is a heaven-sent opportunity for cash-strapped cable companies to sell its customers extra products and services. These include a much wider range of TV channels and subscription packages, there’s also telephone and broadband Internet access and in some areas potential money-spinners like video on demand and interactive facilities.

 

 

PLASMA FLICKER
Last Christmas I purchased a LG MZ42PZ17 plasma screen. I noticed when watching Sky+ that the picture quality is poor and also, when playing back a recorded programme, the sound was not in sync and the picture flickers when dark scenes are on the screen. I had an engineer look at the flickering and he said he would get back to me. He made a phone call and was told that LG knew of the problem and were looking into it. I later contacted the LG help desk and they told me there was nothing wrong with the screen but the Sky receiver was not compatible. I don't understand that because it also flickers with DVDs connected with component cables. Sky+ plays normal programmes okay, albeit at poor quality. I am now starting to get a bit fed up!
Michael Stoker

A

We’re not aware of any generic problems with this panel and all of the tests we’ve carried out, and the other reviews we’ve seen, indicate that it is a respectable, if unremarkable performer. There’s certainly no suggestion of a persistent flicker or sync fault. The fact that the engineer, LG’s Service department and the Helpline are not in agreement doesn’t surprise us but the lack of compatibility with Sky+ is a new one. To be honest it sounds a bit desperate and not very plausible either since a Sky+ box is just another AV source component, like a VCR or DVD player, with standard audio and video outputs. However, the real point is your panel (or the optional tuner box, if you have one) has what sounds like a genuine fault. The screen is still well within its warranty period and you are entitled to have it fixed or replaced, and you can tell them we said so!

 

QUICK TIP

Screen flicker is not something you see very often on plasma panels. In fact plasma screens are immune to a number of common maladies that afflict CRT-based displays. Picture linearity and geometry mis-alignment are unlikely to be a problem as the image is made up of a grid of fixed picture elements or pixels, rather than a spot ‘scanning’ across the inside of the picture tube. Picture roll and ‘tearing’ should also be a thing of the past as the image is processed digitally and less liable to suffer from synchronisation faults.

 

 

GETTING STARTED 1 – SHAPE SHIFTING

The picture shape option is a more or less standard feature on almost every DVD player’s setup menu and is used to configure the machine’s video output according to the type of TV it is used with. This is a manual setting because the player has no way of knowing what type of TV it is connected to. The material on a DVD will almost always be in widescreen format (unless it’s an old movie or TV programme). However, it is up to the player to alter the picture shape to suit the TV, which it does by adding black bars to the top and bottom of the picture, to create the 4:3 letterbox display, or crop the sides of the picture for the 4:3 pan & scan picture.

 

There is one further layer of control that determines the shape of the picture that ends up on a TV screen. Most recent widescreen TVs support a system known as automatic widescreen switching/signalling or ‘WSS’. This changes the picture on a 16:9 TV from a 4:3 format to widescreen mode under instruction from the source component. At the moment there are two commonly used WSS technologies, and they work quite differently. The first relies on the source component and display being connected by SCART lead, when the picture is in widescreen format the source component sends a switching signal on pin 8 of the SCART lead. The second method inserts a set of data bits or a ‘flag’ into picture line 23 of the video signal. Both systems are flawed and cross-brand support is patchy. There are also plenty of examples of video devices that inset WSS flags into composite and RGB signals but not into Component or Y/C video outputs.

 

 

GETTING STARTED 2 – PICTURE QUALITY

It is fair to say that in this country all TV broadcasters, whether terrestrial, cable or satellite meet and in most cases exceed the minimum Quality of Service (QoS) requirements laid down by industry bodies like the International Telecommunications Union (ITU), but how exactly is picture ‘quality’ determined?

 

With analogue transmissions the picture signal is a fixed entity and it is relatively easy to measure its progress at every stage of its journey, from the studio to the TV screen, using well established testing methods but it’s not quite so easy with digital TV. The problem is digital TV signals are highly compressed, to reduce the amount of data being transmitted. This is a non-linear process and varies constantly, so unless the measurements are carried out using static test patterns, the quality will appear to vary according to such things as the amount of movement on the screen. To complicate matters further there’s another variable to contend with, called ‘statistical multiplexing’. This allows broadcasters to jiggle around with the data rates in each video stream, to make the most efficient use of the bandwidth available to them. In other words a news or shopping channel, which shows mostly talking heads, will be apportioned less space than a film channel showing action movies containing a lot of fast movement.

 

The bottom line is that it is extremely difficult for engineers, let alone non-technical viewers to make authoritative judgements and pronouncements on the picture quality of digital television. It’s also difficult to make direct comparisons between digital and analogue picture quality, though many engineers maintain that analogue TV at its best still has the edge.

 

---end---

 

Ó R. Maybury 2003, 0104

 

 

 

 

 

 

 

 

 

 

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