Q&A # 41 - December 9, 1997
Staff
Q I am considering buying a sub in the $250 - $450 price range. I found several models in this price range that were given good reviews in
various magazines. (Such as Alantic Technology 162PBM, Energy ES-8,
Boston Acoustic CR400, Acoustics Research S10-HO, etc.) But it is hard to select the best as each magazine review usually has their unique best pick. I guess I have to rely on my own hearing. But I do
not know what to look for during an audition. Appreciate if you can give some advice.
Also, do you think that the size of driver (8", 10" or 12"), the configuration design (vent box vs. acoustic suspension, front-fire vs. downward firing), power rating (50W, 75W, 100W), and overall size
can be a selection factor? In another words, will it be true that a 12 inch driver design always
is better than a 8 inch driver design? Or a 100W sub better than a 75W? Overall size the larger the better?
A Excellent question. If all the subs had the same basic design, but only differed in the driver size and amplifier power, then yes, the bigger the driver and more powerful the amplifier, the better. Unfortunately, there are a lot of different designs, and you can't go just by the driver size or amplifier rating. For example the Sunfire subwoofer and the new Velodyne HGS-10 both have 10" drivers, but they put out incredible bass, as good as some 15" subs, because the excursion of the drivers is large, and the amplifiers are very powerful. But, in general, the larger the driver, the better, and the more powerful the amplifier, the better. This is especially so with the $500 (and less) subwoofers, as they tend to use conventional drivers with conventional amplifiers. Listening is the best test. Magazine reviews are just to get you started on your purchasing quests. Have the salesperson play some CD music with female vocals. If the sub sounds boomy or chesty (like the singer has been smoking three packs a day for twenty years), and the low pass crossover is set to 80 Hz or lower, then it is not so good. Also try a good laserdisc or DVD with something like "True Lies" at the chapter where Arnie says, "Here is my invitation" (I think it is chapter 4). Crank up the volume and see if the sub can handle it. If you hear a crackling sound from the sub or if the sub shuts down, its limits have been reached. Of course, every subwoofer can be pushed to its limits, but you want to make sure that your needs are met within the limits of the subwoofer that you purchase. If you play music but not action movies, or if you don't ever play your system very loud, the needs are much different than if you like to make the entire house shake.
Q Currently I own a mass market receiver (HK-25mkII) and am intending to buy a pair of speakers (Ruark Sceptre) that I like. Since my receiver has low power output (75watts/ch in stereo; 65watts/ch in surround), I wonder if it will cause any clipping and/or any harm to the receiver and/or to the speakers as they are rated at 150watts nominal in 8
ohms? If yes, can you suggest anything to help as I hope to use the receiver for sometime before buying another one?
A Mass market receivers don't have very big power supplies, so they can clip pretty easily. You would not damage your receiver, but it could damage the speakers if clipping were occurring a lot of the time. I would suggest just using the volume control carefully. For a typical receiver, don't turn it up past about 10 o'clock on the setting. When you get your new receiver, make sure it is one with pre-out jacks, and then later on, buy a five-channel power amplifier to go with it. They have much better power supplies.
Q I have been reading your site for a while, from down here in Australia. I am looking to buy a Dolby Digital receiver, like probably everyone
these days. Currently I have a Rotel RA960BX 60w/ch integrated amp. This is
pretty powerful, but I really like listening to loud music, so I bought a M&K
V125 subwoofer which is great. Now I'm looking for a more powerful
receiver with DD for DVD. My short list at the moment includes the Yamaha 992, 2092, the Onkyo
747 and 838, the Denon 3200 and 3600, the Pioneer VSX05 and 07TX, the
Sony DA80es and DA90esg and to round it out, the Kenwood 1080VR and
1090VR. I have the specifications on all of these, but because I really want to
make sure I buy a powerful enough receiver, I am trying to find out
information on the power supply for them. So my couple of questions are: Is it important for DD to have equal power to all speakers (the Onkyos don't, and I would have thought that more sound would naturally come from the front in movies still?) Which of these will sound best for stereo only? Should I keep my Rotel or will these be better than this? Could you give me a rough ordering of the loudness of each of these, since I must have clean, loud sound (especially in stereo)?
A In general, all the mass market receivers are pretty good these days, and will sound roughly the same. Differences will be found in the way the controls are laid out, and the number of features, e.g., DSP sound fields. In terms of loudness, look at the specification sheet and lay them out as to number of watts. Then look to see that they are rated into 8 Ohms, then as to whether they are at 20 Hz - 20 kHz or at 1 kHz. Ratings at 20 Hz - 20 kHz are better. Then look at the THD (Total Harmonic Distortion). If the center channel, and/or the rear channel(s) are rated at higher THD than the front left/right, this means the center and/or rear have less capability, even if it says the same number of watts. Since you are so concerned about the loudness and cleanliness of the two channel stereo, I would suggest getting a dedicated processor with a five-channel power amplifier. Of course, make sure the processor has 5.1 inputs for a DD processor, or has DD built-in. This will give you a cleaner sound (but dedicated processors generally have less features than the receivers, if that is important to you). If it is going to be a receiver, I would suggest the Yamaha RX-V2092. It's dynamite.
Q I am a radar engineering physicist and am very impressed with your willingness and ability to answer difficult technical questions. How
different is the experience when I call a manufacturer!
I have become a home theater enthusiast in the past year and am very
satisfied with my Harman Kardon Pro-Logic A/V receiver and CD player,
and Cambridge Soundworks Tower IIs, Center Stage, Powered Subwoofer, and
Optimus bookshelf speakers for surrounds. My source materials are VHS tape
with Dolby soundtracks and music CDs. As a professional engineer I often
purchase new components and technologies so I often feel like a guinea pig
testing hardware for the manufacturers. With my HT system I would rather
stay with mature technology, so I am not going to make the jump to digital
until (and unless) it becomes mature. My question is when do you forsee
this happening? When will digital A/V technology mature to the point of
some stability? Considering the upcoming HDTV, and the continuing flux of
DVD, Divx, DSS, and Cable, how long before it all becomes stable,
integrated, and mature?
A Because the market is so fiercely competitive, and because appearance of new technologies seems to be escalating, I suspect it will never become stable to the point we can feel safe in buying into it without fear of having something come along that is not backward compatible. Between now and HDTV release here in the US, there will be even another format which uses progressive line scanning at 525 lines, instead of the interlaced 525 lines we have right now. Digital VCRs are emerging, then HDTV, then 96 kHz/24 bit audio on DVD, then HDTV DVDs, HDTV digital VCRs, recordable DVD, etc., etc. It is unending. Back when color TV came out, many consumers waited and waited to get one, wondering when the technology would be stable. In the meantime, they missed color TV broadcasts. I guess what I am saying is that we should all just enjoy the technology as it comes along, buying what we feel comfortable with, to at least have some of the new toys. There are a few ways to protect yourself, such as getting a receiver with pre-in jacks and pre-out jacks, but in general, we take a risk every time we buy just about anything these days.
Q I am looking for a center channel for my home theater setup. I have a Kenwood KR-V990D AC-3 receiver, Carver Amazing front
speakers, Bose AM-5 rears, and a Tannoy subwoofer. I have read
a lot about timbre matching for the front three speakers.
What do you think would be a good match for my Carver fronts
for less than $400? Most of the electrostatic front speakers that I've seen (like
Martin-Logan Logos) are bags of money.
A I have a set of Carver Amazings too, and I think this is one of those cases where you should employ the "Phantom" mode for the center channel. Most of the sound goes to the center channel, and it would be extremely difficult to get a tonality match for the Amazings without going to something pretty big. This is especially so if your budget is $400.
Q I've been looking at Energy speakers, who I think also makes Mirage speakers also in Canada. The deal was around $2500: $950 for pair of C-8
(fronts), $400 for AC-4 (center), $680 for the rear speakers, and a sub
for about $580. Not sure if I could be getting better speakers for my
money? I was told Definite Technology were the speakers to get. What do you
think? Anything else out there I should be looking at? I'll be using
this system to go Digital for movies and also listen to music with lots of
bass.
A Energy is in the same range as the Def Tech. You really should listen to them all and make your choice based on what you hear. I
listen for several problem areas: one is boominess, which is the 80
Hz region; a second is chestiness (voice sounds too deep) in the 120
Hz region, then nasality in voices, which is in the 800 Hz region,
and finally, tizziness or sibilance, which is in the 5 kHz region.
For digital surround, I would recommend getting the same speakers in
the rear as in the front. A very good subwoofer is really important
too, especially if you really like deep bass.
Q I think that I fried one of my Klipsch KG 5.5 speakers. I was listening to a punk rock CD (I don't like punk, I was mocking it). It
has 17 different bands on it. One of the bands did a particularly bad job
of recording, and it has terrible distortion. All the other bands on this
Vans shoes Promo CD sound great. I was listening to the other bands really
loud with no distiorion. Then I switched it to track 12 and those terrible
sounds (guitar feedback and microphone distortion) came out. Ever since
then, my left channel woofers (two tens wired in series) have been making a
terrible crackling sounds every time I try to crank it up. Is the speaker
fried? Could it be the crossover? I've only had them for about five
months. What do you think Klipsch will tell me . . . Tough luck? Anyway,
what causes speakers and or crossovers to get fried or blown? What do you
think is wrong with my speaker? What causes distiortion?
A It is usually not having enough power rather than having too much that damages speakers. If the volume is too high with a small amplifier, clipping occurs, sending square waves to the speakers. The first to go is usually the tweeter. There can also be problems with the woofer voice coil getting out of alignment, causing it to rub against the magnet. Without hearing your woofers, it would be difficult for me to say what is wrong. However, you should do the following. First, switch the speakers from left to right, right to left and see if the crackling sound is still in the same speaker. If it is, then there is something wrong with the speaker, and since you have only had it for 6 months, it should still be under warranty. If the crackling sound is still in the same channel, but now coming out of the other speaker, then it is not the speaker. Make sure all your cable connections are clean and tight. Switch the cables around left to right, right to left. Try all combinations to locate which component has the problem and then get it repaired.
Q I have just purchased a Yamaha 992 receiver and a Toshiba 2107 DVD player. Is it better to use the digital connection between the DVD player and
receiver and allow the receiver to do the D/A conversion (i.e., "PCM Digital
mode") or is it better to select the "Analog" input, and allow the DVD
player's internal D/A converter to do the job for me? (PS I have a
relatively decent set of interconnects.)
A The only way to decide is to try them both and listen. Make sure you use a 75 Ohm coaxial interconnect between the digital out of the Toshiba and the digital input of the receiver for this comparison. Use a CD (I assume your question is about playing CDs on the DVD player) that has some splashy cymbals and also some violins. Listen for the detail in the sound. If the two DACs are different in their capability, you will here it in those fine details.
Q I am upgrading to AC-3 and
have been shopping around for AC-3 compatible DVDs and LDs. My confusion
lies in the labeling. For example, LD labels reflect the following
wording: "Digital Laserdisc", "Dolby Digital", "Digital Sound Stereo",
"THX", "Digital Sound", and "Matrix Surround Soundtrack". DVD labels
contain "Dolby Digital 5.1 Audio" or "Dolby Digital". The question is which
of these formats will give me an AC-3 six channel (5.1) soundtrack? Is
there a logo, other than "AC-3" , that denotes AC-3 compatibility?
A Digital Laserdisc, Digital Sound Stereo, Digital Sound, and Matrix Surround Soundtrack, are not AC-3 (DD). All laserdiscs have digital sound. There are two sets of LD sound tracks, digital and analog. In the case of a regular LD, there is a digital set and analog set of sound tracks. In the case of a laserdisc that has Dolby Digital (AC-3 or DD), the right analog channel contains the DD track, which is now a digital bitstream. The LD will be labeled as having Dolby Digital, DD, or AC-3. THX is a quality standard, not a format. Matrix Surround usually means the soundtrack has not been processed with Dolby encoders, but will decode with a surround sound processor. If the laserdisc is DTS, this is different, and it won't have a DD sound track on it. DVDs in the USA all have DD sound tracks, so you can safely rent or buy any DVD to use on your DVD player. Later on, there will be some DTS DVDs, but they will be clearly labeled (I hope). It is unlikely they will play on current DVD players. DTS laserdiscs are backward compatible with all LD players that have digital outputs. Divx DVDs are another matter, and they won't play on current DVD players. Divx plans to release players and the discs next year.
� Copyright 1997
Secrets of Home Theater & High Fidelity
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