Q&A # 207 - November 16, 2000

Staff

Q I bought an Onkyo Pro Logic decoder a couple of months ago. One of the specifications says its center power output is 22 W at 6 ohms 1 kHz (DIN), and 29 W at 6 ohms 1 kHz (EIAJ). What does DIN and EIAJ mean? How much difference does both make on the output power?

A DIN is Deutsches Institut f�r Normung, and EIAJ is Electronic Industries Association of Japan. They are institutes for setting and maintaining standards used in specifications. In the US, we have the National Beaureau of Standards (NBS). The standards include all sorts of things, not just Hi Fi. The most important standard for audio power is watts RMS, or Root Mean Square (often it is not capitalized), and across the entire spectrum, 20 Hz - 20 kHz, into a speaker load of 8 Ohms. When manufacturer specs deviate from this, it means the marketing department is trying to make the power spec look bigger. This includes stating the spec at 1 kHz and with only some of the channels being driven rather than all of them at the same time. It also includes stating the spec at 6 Ohms rather than 8 Ohms. Your decoder probably delivers around 12 watts RMS, 20 Hz  - 20 kHz, at 8 Ohms.

Q I have heard through the industry that 8" CRTs will no longer be available (Sony is only offering 7" and 9"). Can you give me some insight on what is going on in the CRT front projection market?

A  The CRT market has always been drive by the industrial market and not the home theater market. The industrial market is moving to digital display devices like DLP and DILA. (LCD has always been there.)

If you own a CRT you will not have to worry about getting replacement parts because companies will continue to product CRTs since there are so many out in the field (they need to have replacements for those who continue to use them).

Q I have seen some speakers whose bass drivers have cones that look very rough and irregular on the surface. Are these defects?

A You are referring to cones that are made from paper pulp. The pulp contains an adhesive, and when it is wet, the pulp is laid onto a mold that is in the shape of the cone. The pulp dries this way, and because of this, the final dried cone does not have the stress that a cone has from forcing its shape into an already dried sheet of thick paper. It is like a cast metal piece compared to a forged one. The cast metal has less stresses stored than a metal piece that has been hammered after cooling. The pulp cones are very expensive, and are usually found only in high-performance speakers.

Q I am new to home theater (but an old audio buff) and am confused about whether one needs a progressive scan DVD player if one uses a TV with a built-in line doubler. I saw my first progressively scanned DVD played on a TV that accepts progressive scanned signals not too long ago and was stunned by the image. I have to have that! But some articles I've read on the web imply that I do not need a progressive scan DVD player if I use a TV with a built-in line doubler. What's the scoop? Will I get the best picture quality if I use a progressive scan DVD player (such as the Toshiba 6200) even though my TV has a line doubler?

If you would entertain a second question, I am having a tough time deciding about a large TV. I have the sense that TVs are rapidly evolving both in price and performance, and that now is not the time to spend $2500 -$3000 to buy one. For example, I like the Mitsubishi WT-46807 (not much room for a larger screen in my house), but the literature says Mitsu guarantees to make available upgrades "so that the television you purchase today can be made compatible with near-future advances in digital television and digital interconnectivity." That's a nice policy, but it gives one pause. What near future advances do you think they are talking about?

A The key technology a progressive DVD player has over a standard line doubler is 3-2 pulldown (also called Inverse Telecine). This is what gave Faroudja the edge for many years. DVDO brought out the iScan plus which also performed 3-2 pulldown at a very low cost.

Some newer TVs like the 510, 610, and 710 from Pioneer also perform 3-2 pulldown. Would going for a progressive DVD player still offer improved picture quality? You bet!

TVs with line doublers (more correctly called de-interlacing) built-in must convert the incoming video signal to digital, perform the de-interlacing, then convert it back to analog. The quality of all parts may not be as good as they could (and from what we have seen are not!)

When 3-2 pulldown is being performed, the algorithms are looking for a duplicate field that is repeated. In the analog world, noise in the image will make two identical fields appear to be different (this makes it harder for the de-interlacer). A progressive DVD player is performing the de-interlacing without the fields every being in analog form. Those two duplicate fields are 100% identical bit-for-bit. It makes its job a lot easier. When one of the new DTVs receives a progressive signal, it should bypass the A/D stage so you are getting a very clean signal.

The upgrades policy of Mitsubishi is a marketing strategy, and it is genius. They have probably started making the circuits with boards that can easily be unplugged and replaced. Maybe some EPROMs in there too. However, even they probably don't know exactly what advances are coming.

Q I purchased a Yamaha DSP-A1 two years ago. Unfortunately, it did not come with component video in/out. With the newer DVDs and Hi-Def TV using the component video connections, I'm wondering if there is any way to upgrade the unit. My main reason for wanting to use the DSP-A1 as a pass through is for the on-screen menus. It is rather difficult to see the display on the DSP A1 sitting on the couch.

A Sorry, there is no way to upgrade your DSP-A1. Many receivers don't have the bandwidth to properly handle the component signal anyway.

You may wish to just set up a second input on your TV and use the coax or S-Video output of your DVD player for this input. This way, if you must look at an onscreen display, you can temporarily switch to that input, make your changes, then switch back to the component input.

Q I have pre-ordered a Sony Playstation 2 that I am planning to hook up to my home theater system. What interested me about the Playstation 2 was its DVD compatibility and digital output, which will allow the pass through of both DD and DTS. As an audio nut, I am FAR more interested in the sound quality of the games than the graphics. What intrigues me even more is the ability to
have a video game programmed with 5.1 surround sound. My question is this:  Sony's spec sheets state that the Playstation 2 only has an optical digital output. I have a B&K preamp (with built in decoding), but it only has coaxial digital connections. Is there a product/adapter that can convert the signal from the optical output of the Playstation 2 into the coaxial format I need for input into my preamp? The sound is the main reason I ordered the Playstation 2, and I would hate to be let down because Sony only gave it an optical digital output. I am certainly not going to replace a $2,000 preamp over it. Aren't coaxial digital connections far more common? Why would Sony include the less popular format if it were not planning on including BOTH formats??

A The coax output is called S/PDIF. The S stands for Sony. All of the Sony DSS receivers also only include the optical (called Toslink) digital output. I imagine they consider the market to be very small and not worth the inclusion of a coax output. Yes, there are boxes that will convert optical to coax and coax to optical. Here are some links: http://www.edirol.com/music_equipment/roland_accessories/midimanco2.html    http://www.hosatech.com/ODL.html    http://store.yahoo.com/soundloft/co31.html   http://www.midiguy.com/Namm/NamMman.html 

Q I have had a Rotel 965 A/V Receiver for a while, and I have noticed that when I put in a DTS movie ("Saving Private Ryan") during the DTS Promo, the sound turns in to a static that spikes. But then the movie is fine after that. I am wondering if this is a common experience? And would I need a DTS ES decoder for a DTS ES DVD such as "T2 Ultimate Edition"? The same problem happens for the whole movie with that DVD.

A The reason you hear what you do is because DTS has several flavors for their sound format. Some with and some without flags to tell your decoder what to do. Your surround processor must listen and detect what sound format is coming in. The noise you hear is your decoder outputting the DTS data before it realizes that it needs to switch to a DTS algorithm.

Is this a common experience? You bet. It various from processor to processor and even DVD to DVD. Some decoders simply mute the sound until they are sure, which often results in the very beginning without sound. Once it detects, it's OK (until you pause or a layer change).

You should not need a DTS ES receiver to listen to T2. It sounds like your decoder may need an upgrade. DTS claimed that their DTS ES was fully backwards compatible, but you are not the first to report having problems. You can just add that glitch to the long list of DTS issues not yet resolved.

Q This question stems from a Q&A posted August 3rd. In that post, you recommended setting all speakers to "Large" and sending all six pre-outs to the subwoofer. While I doubt some of my speakers could be described as "full range" (B&W DM 603 IIs for the fronts, DM 601 IIs for the rears and a CC6 for the center), this still sounds like a good idea. A quick test by ear and SPL meter with the low frequency sweep tracks on the Avia disc seems to suggest that my speakers will go down to 50-55 Hz. My question is, what is the best way to send all six pre-outs to the subwoofer? I have a Hsu Research TN1225HO sub with the 250W amp. Since the sub amp has three inputs, I've plugged in the left front, right front and subwoofer pre-outs from my receiver (a Denon AVR-3300) with good results. But this still leaves the center and surrounds. I tried using a cheap Radio-Shack Y-adapter to join the center and subwoofer channels into one at the subwoofer amp. Some tests with the Avia disc seemed to suggest that everything was working, at first. When I played the LFE channel sweep track, I could hear some of the subwoofer channel being sent back to the center channel. This was extremely subtle. I could only detect this effect by getting very close to the speaker or by putting a finger on the edge of the speaker cone. It can't be the sub simply setting up sympathetic vibrations in the center speaker as it was still there when I turned off the sub. This phantom signal did go away when I unplugged the center channel cable from the Y-adapter. Is this just a result of the cheap Y-adapter, or is it always the case that there is some signal leakage back through the pre-outs? I doubt this faint signal would make an audible difference, but I am concerned about doing damage to my receiver. But is that even an issue? I would like to drive all my speakers at full-range as my Hsu sub tends to be very easy to localize.

A In that Q&A, I was really just talking about using some, but not all, of the pre-outs to the subwoofer by using a Y adapter to split the pre-out to go to one of the subwoofer inputs, and the other leg of the Y adapter to a main power amplifier. What you are doing is joining the pre-outs to go to one input. This is not a good idea because you are sending the pre-out voltage of one channel back to the pre-out jack of another channel. It is low voltage, and may not harm your receiver, but it is certainly tempting fate. If you had done this at the speaker output level, where the voltage is higher, you probably would have burned some circuits out. So, disconnect the pre-outs from one another. You can just send the pre-outs of the front left right channels and subwoofer out to your subwoofer with good results. Practically all of the bass will be contained there. If you really want to have all the pre-outs going to subwoofers, you should get a second sub. Another HSU would let you have a connection for all six channels.

� Copyright 2000 Secrets of Home Theater & High Fidelity
Return to Q&A Index.