Q&A # 147 - November 10, 1999

Staff

Q I'm looking for the "right" type of speaker cable for my brand new, high-end L/C/R midrange/tweeter monitors (Citation model 7.2, THX-certified monitors, $1,350 each). These monitors are rated "Class A" speakers for home theater purposes by one of the printed magazines. The rather favorable review found only one minor quibble for these speakers (quote): "If anything, the 5 to 7 kHz. range sounded a little reticent, resulting in a slightly veiled, darkish character that was consistent from program to program. From measurements, on-axis responses confirmed some lack of energy in the region around 1 kHz. and in the 5 - 7 kHz. region. Other than these small suckouts, the on-axis response was pretty flat, especially in the midrange" (end of quote). Conceptually speaking, is using a somewhat "bright" cable - such as the Nordost Blue Heaven - the right way to follow in order to ameliorate/counteract the reticence of my speakers in the 1 kHz and 5 - 7 kHz regions? Or should I choose a "warm" cable (such as those from Cardas) or an "intermediate" cable (such as JPS Labs' The Superconductor+)? One reputable dealer is recommending that I purchase the JPS Labs cable. According to him, this cable is half-way between the "bright" Nordost and the "warm" Cardas, and thus it is his No.1 recommendation. Also according to him, Nordost Blue Heaven would be a reasonable No.2 option. Would you agree with my dealer's recommendation? In general, what is your opinion on JPS the Superconductor+ cable compared to the Nordost Blue Heaven or to the similarly priced Nordost Red Dawn? Would you recommend JPS over Nordost, or vise versa, for my home theater application?

A Many speaker manufacturers put the valleys, or suckouts as the reviewer called them, in order to shape the sound that they produce. As I have mentioned previously, there are four frequency regions that I find very annoying when there are peaks: the 80 Hz region, which can make a speaker boomy, the 100  Hz  - 160 Hz region, which produces "chestiness" (voices sound too deep), 800 Hz, which can make a voice sound nasal, and 5 kHz - 6 kHz, where voices would sound overly sibilant ("s" in words sounds too strong). In this context, the review you mentioned might be a little naive, since the manufacturer probably designed those 1 kHz and 5 kHz - 7 kHz valleys on purpose. The dips in those regions make your speakers sound more appealing. That is one reason you like them so much. If a particular CD had extra sibilance, the slight dips in the 6 kHz region would tend to mitigate it. The same for CDs where a female singer might be too close to the microphone. Cables don't make the sound better. They degrade the signal, more or less. However, preferences tend to be very personal, so rather than say that you should select the most neutral cable, you should really go in and listen to your speakers, connected to the various models you mentioned. It might require going to several stores, if the one you mentioned does not have all three. In fact, you might even end up liking one that you have not encountered before.

Q I have finally obtained my Sunfire Stereo Amp and Classic Preamp. I'm very confused about my speaker selection with this combo. I'm looking for a $2,000 range speaker product to match the Sunfire pieces. I know it very subjective, but I would like some advice to test speakers in this price range. Two channel stereo is my only desire. I thought I liked the Def Tech 2000 or 2002, but the rap seems to be they are really for home theater.

A The Sunfire will drive any speaker because of its power. But since you say you are interested only in music rather than movies, I would suggest something that sounds good at low level. There are those speakers that sound good with music, but because they are marketed for home theater, they sound better at loud levels rather than when played softly. Monitor Audio's line is one of my favorites for musicality, and we use the Studio 20 SEs here as reference speakers, but they are more expensive than your budget. However, I would suggest listening to one of their other models, or perhaps looking for a pair of Studio 20s used (although they are so good, you might have trouble finding them). Dunlavy makes very neutral sounding speakers, which will be a real plus for you. We recently reviewed their SC-1/AVs.

Q I picked up an old Rotel amp at an auction sale with the intention of using it to power Room B speakers. It came with an EQ which the previous owner had looped through the pre-out/pre-ins. It worked fine for what I want. However, if I disconnect the EQ I get no sound. I saw in Q&A #141 mention of pre-out/pre-in shorting plugs. Does this mean that if I disconnect the EQ, I must insert these plugs? If so, will simply using RCA cables from out to in work? Or must I use special shorting plugs?

A If the EQ was looped through the recording loop, then it is just a matter of turning off the monitor switch. But, I suspect in your case, it is through the pre-out/main-in circuit, where you would, indeed, have to use plugs. But, they are not creating a short. Shorting plugs are for a different purpose (reducing hum in certain situations). Sometimes the necessary connectors are simply U-shaped pins that connect the center of the pre-out RCA with the center of the main-in RCA. You should use as short a connector as possible in any case. Monster Cable makes some that are only a couple of inches in length, and that is what I have used in the past. If you use RCA cables, get the shortest ones that you can find.

Q I recently purchased a used subwoofer (Velodyne F1500R) and would like some advice on placement. I plan on using a line level connection from my preamp to the sub, and line level back from the sub to the amp and main speakers using the sub to filter out the low frequencies (I am guessing about 50 Hz) on the return journey. What is the length of interconnect I should not exceed between the pre/sub and sub/amp? My concern is, does the line level signal degrade beyond a certain length? If the interconnect is of substantial length, i.e., 20-30 ft., is the time lapse between the signal emitting from the sub vs. the main speakers significant? Can human ears perceive the difference? Does the sub 'beef up' the high pass signal before sending it to the amp/main speaker? Or is the degradation cumulative from the run of line pre-sub and sub-main?

A The high-pass out to your main-ins for your front left/right speakers is 85 Hz on the Velodyne F1500R, so if your main speakers are anything but very small ones, you are better off not using the high-pass out from the subwoofer. Better just to drive them directly from the receiver amplifier. Set the low-pass to about 50 Hz  - 60 Hz, assuming your speakers are reasonably sized. Long interconnects might produce more hum, rather than a necessarily attenuated bass, so keep it short (6 feet or so). If you use a low-pass of 50 Hz, the sound from the sub will be pretty much non-directional, so you can put it anywhere you want, but keep it a couple of feet out from the wall, and un-equal distances from rear wall vs. side walls. The signal passes through the cable at almost the speed of light, so you will not have problems there. The subwoofer does not beef up the high-pass signal before sending it out (I assume you are thinking about signal amplifiers for cable TV).

Q I presently own a Bogen all-tube receiver model RP 230. It is certainly not a hi-end tube component, but it offers me the warmth I can't find in inexpensive digital receivers today . It's all point-to-point wired and, being a guitar player, I have a love for all things tube. I would like to purchase speakers for it but have very limited resources. Can you suggest some good sounding speakers for under $200 that are fairly efficient? The power amp section is approximately 20 watts per channel using dual 6V6 power tubes.

A Your price-point does restrict the possibilities, but try listening to the PSB Alphas, which are 91 dB sensitivity. We reviewed them in Volume 5, Number 3.

Q Hello, I'm looking for some educated opinions. I'm planning on putting together a modest home theater system, and I plan on doing the speaker construction myself. My question is about the center channel speaker. It seems that the MTM format is a very popular style with commercial manufacturers and DIY'ers alike. Through my internet researching for this project, I found that Brian Steele, of The Subwoofer DYI page, mentions that the MTM design has a poor horizontal off axis response, which would be advantageous to have with a home theater system, seeing as how not everyone is directly in front of the TV. Is the horizontal MTM format used for it's symmetry and aesthetic appeal, sacrificing horizontal dispersion? Or perhaps, not being that simple, neither of these? I'm trying to find out some info on this topic and I was wondering if you might have some insight.

A The MTM (two midrange drivers with a tweeter exactly in the middle and in line with the mids), when situated vertically, does give good dispersion side-to-side, but not to the ceiling and floor. That is one of their characteristics. So, as you say, when the MTM is placed on its side on top of a TV, it won't have good side dispersion for a wide audience. Some manufacturers do use the MTM as a center channel when selling a set of LCR speakers, because it keeps the costs down. They rotate the speaker binding posts and call it a center speaker. The dispersion to the side is reduced, but not simply non-existent. However, if the tweeter is between two mids, it might not be an MTM (D'Appolito design), if one of the mids is actually a woofer while the other mid is really the mid (as per the crossover network feeding them). Also, some seemingly MTMs have the tweeter out of the direct line that is drawn from the center of one mid to the center of the other. That changes the dispersion pattern.

Q I am starting to get a little confused about all of the new HDTV and DTV formats and specifications. I am in the market for a new TV and I was originally sold on the Sony Wegas. After reading many reviews of people having problems, I started having second thoughts and began searching. At first, all of the HDTV compatible TVs were way too expensive, but now they seem to be coming down in price. I saw a digitally compatible Panasonic (32XF56) that has 480i and 480p for the same price as the Sony. Then, I found a Toshiba (CN36X81) widescreen that has 1080i, 480i, and 480p compatibility for only $500 more than the Sony. My question is am I going to need 720p in the future, or will the Toshiba with the 1080i be enough? Also, are these TVs going to be like the DVD players with first, second, and third generations that have bugs that are being fixed each time? I don't want to spend that kind of money and then have to get a new TV anyway. Please shed some light on what I should be looking for and what the future of HDTV is.

A The direct view HDTVs that I have seen will handle 1080i but not 720p (720p requires a higher scanning frequency than 1080i). Also, most of the rear projection HDTVs have guns that are smaller than 9", and 9" guns are required to show all the info in a 1080i program. Eventually, 720p programming will be there, but right now, lots of programs are really just 480i line doubled to 480p. Real hi-def stuff is not all that common. As a result, the typical HDTV upconverts most or all of the incoming programs to a predetermined resolution, and many of them don't do a very good job. Plus, you don't have a choice of selecting the resolution you want to view it at. So, for the early adopters, it will be an interesting journey. One TV that I really like is the new Mitsubishi rear projection TV with 9" guns, and it will show 1080i. However, it will not show native 720p, because that scanning capability is too expensive right now. What makes me a little nervous is that DVD may go to 720p. The good news is that Mitsubishi is also coming out with a satellite decoder that will handle HDTV signals and is only about $1,000, much less than other HDTV decoders.

Q I am thinking of using the speakers in my TV as the center speaker for my home theater set up. However, the TV speaker input is the RCA type. How can I connect my center speaker output from my receiver to the TV speaker? Also, will there be any impedance problem?

A There are a couple of ways you could do this (I assume your receiver does not have a pre-out for the center). You could use the left or right line-level output from the recording loop in your receiver. For a stereo signal that has voices, the center channel is encoded into both the left and right channels. However, this would give you a skewed front soundstage that would require turning down one of the main channels (be sure also to turn the TV volume control all the way down first). The other is to just connect the speaker output from the receiver center channel to the TV RCA input jack. There would certainly be an impedance issue, but as long as you start out with the center channel volume and the TV volume control all the way down before you connect it, and then turn the volume up on the receiver and the TV very slowly, it probably will still work with a specific combination of receiver volume and TV volume control settings. If you do this, use a shielded interconnect cable (not a speaker cable), cutting the RCA jack off of one end, and connect the + leg from the receiver speaker binding post to the center conductor of the interconnect (the "hot" conductor", which is the one going to the center of the RCA jack), and the - leg from the receiver to the outside conductor of the interconnect. One last way is to disconnect the TV speakers from the TV amplifier and run a set of banana jacks to the outside of the TV. Then you can alternately connect the receiver's amplifier to the TV speakers or reconnect the TV's amplifier, depending on your preferences. Just be sure NOT to ever have the TV amplifier and the receiver amplifier connected to the speakers at the same time, and also, if your TV has two speakers, connect them in series to the receiver rather than in parallel.

� Copyright 1999 Secrets of Home Theater & High Fidelity
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