Q&A # 43 - December 23, 1997

Staff

Q My Sony SAT-B2 is set for transponder #2 (default). Other transponders have a stronger signal. Why am I not able to change transponders using the on screen setup program? Also, is there any way to change transponders, i.e., internal dip switches or the like?

A I too have experienced this On my DSS, SAT-A2, transponder 9 has the strongest signal. I have not been able to make the box keep the setting. My parents own the RCA model and when you change its transponder, it stays on what you selected. The Sony manual says you should only change this when instructed by a service tech. Perhaps they have some secret to make it stay. Any signal above 70 will look the same, whether it is 70 or 90. But having the stronger signal will be better in adverse weather conditions. That 90 will drop in bad weather and still look great, but the 70 might dip below what it needs to be.

Q I'm really tired of people telling me that I need massive amounts of power to enjoy good home cinema and music sound. My room size is 15' x 15'. Who needs 1000 watts just to listen to a couple of CDs or films? I've just bought a Rotel THX System (RSP 980 and the RSP 985) with 5 x 100 watts of power. I think it sounds good enough for me. Hope I did not make a wrong choice. My bass speaker has its own power supply of about 150 watts each. That's good enough isn't it?

Would a bass speaker with 300 watts of power play much better than a bass speaker that only has 150 watts of power? Please, straighten me out on this matter. As I am building bass-reflex speakers, would there be any difference between using one reflex tube or two reflex tubes?

A Satisfactory power depends on several factors. One is how the power is rated. You have to look at the spec sheet to see. It should be rated continuous rms into 8 Ohms at 20 Hz - 20 kHz with THD (Total Harmonic Distortion) less than 0.5%. If it says at 6 Ohms (for example 80 watts at 6 Ohms compared to another amplifier that says 80 watts at 8 Ohms), or at 1 kHz, or at 0.7% THD, this is not quite as good. The mass market receivers don't have big power supplies, so they often push the ratings a bit, usually by saying the center channel has its rated output measured at 1 kHz, or the THD is more than 0.5% at the rated output. All amplifiers get to a point where the THD starts to rise as the output is increased. Let's say it is 0.1% for most of its output. When the output approaches clipping, the THD increases. It reaches 0.5%, 1%, 5%, 10%, etc. "Clipping" is often defined to be when the THD reaches 1%. The output rating can be selected anywhere along this curve. If the ouput rating is chosen where THD is at 0.7%, it will be a larger number than if it is chosen at 0.5% or at 0.1%. It is a game of specsmanship. They all do it, and it's not a problem as long as you go in for the purchase with your eyes wide open. A second factor is the rating of the speaker. For small amplifiers, it is better to use 8 Ohm speakers with a sensitivity of 89 dB/w/m or higher. So, assuming the amplifiers are of the same quality, you would get more volume from a 93 dB/w/m 8 Ohm speaker with a 150 watt amplifier than an 89 dB/w/m 8 Ohm speaker with a 300 watt amplifier. The third factor is the user's particular needs. If you just want to listen to chamber music as background while reading, this is much different than listening to pipe organ concerts and action films.

The Rotels you mentioned are fine. We reviewed them some time ago. Movies are very demanding, especially action films, and if you like to crank things up. The 100 w/ch of the RB-985 will deliver most of the crash boom, but not all the dynamics that a more powerful amplifier would. On the other hand, it will be much more capable than the 100 watt amplifiers in mass market receivers. So, again, power ratings are not absolute, but rather, very relative things. As far as the port tubes in your DIY speakers go, it is very important to use care with the design parameters when building speaker enclosures. I'm sure you know that you can't just take any old 15" driver and build a box of whatever size fits next to the bookcase, and put a port of random dimensions in it. Best to use one of the software packages available from magazines like "Speaker Builder" and do the job right. Port dimensions will be calculated for you when using this software. However, regardless of the speaker design, the bass will be better with the 300 watt amplifier than the 150 watt amplifier to drive that speaker. Low frequencies are extremely demanding on an amplifier.

Q Is there any way to tape from the newer VCRs to another VCR without the signal changing from good to bad?

A If you are copying movie rental tapes, you will likely run into copy protection, which will give you a terrible copy. There are some copy protection defeating boxes available in the back of audio and video publications, and sometimes they include a disclaimer about legality in their ads, but I have a feeling they know exactly what they will be used for. If you are copying your own recordings from one VCR to another, even without the copy protection, there will always be a little degradation with the current analog VCRs. One way to minimize the loss is to connect the video and audio outputs of the playing VCR directly to the video and audio inputs of the recording VCR, and not going through a receiver. When digital VCRs become the norm, you should be able (theoretically) to make perfect copies, and this really worries the movie producers.

Q Help! My system is plugged into an outlet that is obviously on the same power line as another outlet. Whenever I have my system on and I (doing my own house cleaning) switch on the vacuum cleaner which is plugged into the adjacent outlet, I hear short and sharp clicking, snapping or crackling sounds coming out of my speakers (even with no music playing). I tried using a computer multi-socket extension with surge protector and double noise filters for my system but notice it only helped a little. I just keep forgetting to switch off my system before I begin to vacuum and it happens often. How badly can this damage my system? Is this what is referred to as "loud transients" that can damage tweeters? My system sounds okay though it doesn't seem as refined as before. I'm not sure if my dissatisfaction is because of slight damage to the speakers or I'm just ready to move on to hi-fi from "lo-fi" (my speakers are Wharfedale Modus). Can damage be progressive or does a speaker just "blow"?

A Electrical interference of the type you describe is very difficult to eliminate, because the motors create RF that can travel not only through the house wiring but also be picked up by all the cables in your hi-fi system (they act as antennae). Power conditioners can reduce the RF coming in from the AC supply, but do nothing for the RF picked up by the components' AC cords and interconnects (they are in the circuit AFTER the AC power conditioner). However, I don't think you have done any damage to your tweeters. The transients that you heard about are from the music being played, not electrical interference from motors. When the amplifier runs out of power, a transient will cause clipping, and this type of distortion can damage speakers, but the tweeter, specifically, would most likely either work or not work. Woofers can sometimes be damaged so that they still work, but make strange sounds, like the voice coil rubbing against the side. Your dissatisfaction is probably an urge to get a set of better components, like you suggest.

Q I have been looking into the purchase of some Martin Logans (either the SL3 or the Aerius i's) for the dual application for home theater and music. My local dealers, while helpful, tell me that their application for home theater might not cut it. Their reasoning for this is "The Martin Logans do not achieve the higher SPLs required for the broad range of dynamics used for home theater." The logic doesn't quite make sense to me. I think these speakers sound incredible with great detail, but just a little lacking in the bass area. Since I would be using a sub/subs, this problem doesn't concern me too much. Can you give a little comment on the use of Martin Logans for home theater with a pair of Aerius i's or SL3s, for example, mated with Martin Logans new "center" channel included? Will a setup like this reach appropriate levels to be a convincing home theater application with the right amplification? While on that topic, can you also recommend a couple amplifiers that would mate with these speakers for both home theater and music, whether a 5 channel, or separate 2 and 3 channel amps?

A While it is true that many electrostatic speakers don't achieve the kind of loudness that some cone driver speakers, the advantage of the electrostatics is their astonishing detail and transparency. I heard a set of MLs (I think they were Aerius and the ML center channel speaker) in a home theater configuration at one of the hi-fi shows, and they were spectacular. Five electrostatic speakers can produce PLENTY of SPLs, more than enough to satisfy just about anyone. I think we watch movies with the sound too high anyway. However, you will need plenty of amplifier power, as electrostatics require it. We are testing a pair of full range electrostatics right now, and our 750 w/ch LLano monoblock power amplifiers are just right, so get as much power as you can afford, along with at least one massive subwoofer. I would suggest a minimum of 200 w/ch for all five channels (8 Ohm rating). The one that comes to mind is the Sunfire CinemaGrand, since it will drive speakers down to 2 Ohms. Electrostatics are notorious for dipping to low impedances at certain frequencies. I feel electrostatics would make a great home theater sound, but the amplifier will be critical, so choose carefully.

Q I noticed in your last review, you mentioned something called room gain. What is room gain?

A Room gain is an amount of loudness which is added to the anechoic output of a speaker, depending on the frequency, and is produced by the room containing the speaker. It usually refers to low frequencies, e.g., from a subwoofer. If you measure the output of the subwoofer in the room, using an SPL meter, the measurement already includes the room gain. If you measure it hanging off a bridge, you can theoretically add room gain, at the rate of 3 dB per nearby boundary, but there are more complex issues which affect the real world performance, like room resonances, the panel resonances of the boundaries, etc. The anechoic measurement, hanging off the bridge (or anechoic chamber), would provide the most reliable measurement. The next best thing is a parking lot, for which 3 dB of "room gain" is already included when you take the measurement, which leaves 6 dB more possible in an ideal corner. However, that's optimistic, since most non-concrete boundaries resonate at subwoofer frequencies and therefore pass much of the energy through instead of reflecting it. The purpose of room gain calculations is to figure out what the room response would be like, based on anechoic measurements. This "predicts" the output of the speaker in a "typical" or "Ideal" room. The actual output in any one room may be different than the prediction, depending on what the walls are made of, furniture, shape, size, etc. If you've measured the room response in the first place, you've got something more valid than any calculation (prediction) for that room, but which has limited application to other rooms, for which anechoic measurements are useful, but also limited. In the last review (Sunfire Sub MK-II), we had one too many calculations, adding room gain when it was already there. That has been corrected.

Q The KEF Q15 has been said to have good "imaging". Any comments on their Uni-Q design (I see very little reviews/comments on these speakers)? What are "imaging" and "soundstaging" anyway? I know these are subjective criterias in rating a speaker but it helps to know what they mean. What other terms are used to describe speakers?

A The Uni-Q concept is a nice one, but it is expensive to build speakers that way. Putting the tweeter at the center of the low frequency driver is not easy to do. The bottom line, though, is the sound. We have tested only one model of KEF, and it did not use the Uni-Q design. KEF in general have had good press. We should do some reviews of their other models. There is a vast number of words used to describe the sound, and most of them, like soundstage and imaging are difficult to grasp. Soundstaging means the three dimensional layout of the sound. In other words, can you hear the left to right and front to back arrangement of the instruments? Imaging refers to a precise localization of an instrument in space. Does the trumpet come from a general area and sound sort of like a trumpet or does it sound clear and precisely like a trumpet coming from two feet to the right of the left speaker? The Uni-Q design will help imaging because all of the frequencies produced by that trumpet are coming from one place in the speaker enclosure rather than several places (such as when there are drivers located in different spots in the enclosure, with the high frequencies coming from one spot and the mid-range coming from another).

Q I am just wondering if one can use a Dolby Pro Logic receiver's front channels and its sub out for the front speakers and the powered sub, and add a two-channel amp to power the two rear speakers to achieve DD results when used with a DVD player with a built-in decoder. What are the pros and cons for this setup?

A Your idea is very workable, and there are really not any cons at all. However, to do it, you need a set of 5.1 input jacks on the receiver to connect the five analog outputs from the DVD player's built-in decoder. You also need pre-out jacks for the rear channels on the receiver, to connect the two-channel power amplifier.

Q I would like to start by thanking you for a wonderful publication. Your insights and advice have dramatically influenced my audio thinking and buying decisions. When I first started reading your publication (about 6 months ago) I had a few hundred dollars worth of equipment and nothing but a casual interest in higher-end audio. Well, a few months, and a few thousand dollars later, I'm the proud owner of a reasonably "happening" audio/theater system. I ended getting a great deal on a Yamaha 990 & DDP-1, as per the advice of Dr. Johnson. I really like this system, in that it allows me to get in on the fun, while providing a great deal of flexibility for future expansion without a hugh financial commitment. Adding to the 990 & DDP-1, I picked up a decent JVC 32" TV, a Panasonic S-VHS player, and last but not least a Sony DVP-S7000. I went with the Sony due to finding a unit with the much coveted "switches" at a very fair price. Also, I needed a decent CD player, and no other DVD unit I listened to even came close in the CD department. One of my next steps will be to get a decent 5 channel amp; and from what I've heard so far, I will probably save my pennies for a Sunfire CinemaGrand.

Now to the point. Before I purchase the amp I need to address the weakest link in my system, which are my speakers. I know that speaker selection can be a very subjective process, but I still feel better consulting those that have had opportunity to listen to a much broader range of systems than myself. Currently, I've been driving an older pair of Infinity SM-150s for mains (1-1" tweeter, 2-4" mids, 1-15" Bass Drvr), and a pair of Pinnacle P7 bookshelves for the rear. The SM-150s are very efficient, loud, and produce a significant dynamic range, but the low-end gets a bit muddy, and the mids & highs are not as detailed as I would like. I have considered purchasing the SM Infinity center, sub, & surrounds to tide me over until I can do better, but I would rather put the money into the speakers I will be happy with, even after I get the new amp.

I have been approaching the speaker decision from an "audio first" perspective. I've been a drummer (mostly contemporary Jazz & some rock) for more than 20 years, so music is on the top of my list in terms of Audio vs. Theater performance. I am primarily looking for speakers that will allow me to hear great detail throughout the sonic spectrum at very loud volumes. This is partially for my own enjoyment, but it's also so I can pick out exactly what each musician is doing (especially the drummer). Hits, accents, and subtle nuances need to be as loud & clear as possible. I'm thinking that speakers with this kind of musical detail should also make for excellent HT? BTW, the listening area is about 20x20.

Unfortunately, I don't have an unlimited budget, so I'm trying to find the ultimate combination Music/Theater set of mains for around $1500 (new or used). So far I have listened to both Sat/Sub & floorstanding full range speaker combinations. These are some that stood out in my sat/sub listening: Dynaudio Contour 1.3's, PSB Stratus Mini's, Totem Mod 1's, Paradigm Ref 20s. All the minis were used with a Sunfire Sub. Although, I appreciated the mid & high detail of the minis, the bottom end being handled by the Sunfire created a distracting gap in the spectrum for most all of the music I played. But if I had to pick a winner here it would be the Dynaudio Contour 1.3s. For the floorstanders, the standouts were the PSB Stratus Golds, the Von Sweikert VR3s, and the Vandersteen C2s & C3s. I realize it's impossible to listen to all the speakers available today, but I'm sure you've listened to more than I have, and based on this information could give some "sound" advice.

Having said all that, here are my questions: 1) What has been your experience, if any, with the above mentioned speakers? 2) What other speakers should I be listening to? 3) What do you think is the best combination Music/HT speaker for under $2000? 4) Is there a Sat/Sub combination that is truly seamless for music? 5) Is there an amp that can compete with the Sunfire for both music & HT in that price range? 6) What would be a good preamp to mate with the Sunfire or (?) when I'm ready to move the 990 to my office or BR? 7) And finally, what do you think are the best low cost interconnects (Audio & S-Video) & speaker wire?

As you can tell, I'm pretty excited about all this stuff. In large part thanks to you guys! Keep up the great work.

A Matching subwoofers to the other speakers is not easy, but what I have found is that it's best to use larger speakers in the home theater system, if you use a really powerful subwoofer with them. Also, the phase of the subwoofer output can be blended to the rest of the system only at one frequency, because of the crossover (as you get away from the chosen crossover frequency, the phase of the signal changes). That's common across all subwoofers, except for the Bag End, which specializes in time alignment. Judging from your musical interests, I would suggest getting full range (down to 40 Hz) speakers for all channels, which can handle the high power capability of the Sunfire CinemaGrand amplifier, and also getting a powerful subwoofer which you would set to around 40 Hz- 50 Hz low pass frequency. Go for speakers that use 6 1/2" - 7" drivers rather than larger ones, as this will make the sound tighter and less muddy in the bass. The subwoofer will handle the really low stuff. This will give you deep bass, but not overlap with the rest of the speakers in a way that produces boominess. You have already listened to some great speakers. We have listened to them too (at shows), but not reviewed them. The only others I would suggest are the B&W DM-602s.

� Copyright 1997 Secrets of Home Theater & High Fidelity
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