Q&A # 28 - September 9, 1997
Staff
Q What are even-ordered harmonics? Odd-ordered? Second order? Third Order?
What are square waves? Why is it that high end amplifiers that have more
THD sound better than a mass market amplifier that may have a lower THD?
Part of the explanation may be due to some amplifiers using an IC chip.
However, assuming that power to all five channels are discrete....
How important are interconnects? I recently read an e-mail from DAL
(Dunlavy) who conducted a blind listening test with interconnects. The
conclusion was that most of the people fell into the "placebo effect." I am
confident that using a better interconnect such as a Tara Labs Prism 22 in
lieu of the one supplied with the box will improve sound. But do the $400
interconnects really sound better than a $40 one? I suspect that the "Law
of Diminishing Returns" applies.
With regards to AC-3, I have a Marantz 770 which has 80 watts to the
front/center and 30 watts to the rear. Does this preclude me from being
able to fully utilize AC-3 since the recommendation is to have five
identical front firing speakers? Currently, I am using Mirage Bipolar 595i
in the front, Mirage center MC-3, and small Mirage rears.
Does one have to purchase the same subwoofer if they want to have two
subwoofers (i.e., how would it sound if I purchase a M&K V75 {sealed
subwoofer} with a Paradigm P-1000 {ported subwoofer})? Also, what do you
think about the subwoofer external crossovers if I decide to purchase
another subwoofer to complement my Paradigm P-1000?
A If you take a musical instrument, such as a guitar, and pluck one of the strings, the musical "note" you hear is actually a combination of many frequencies. The lowest one is the fundamental frequency, and is the one you associate with the tone, such as C Sharp or B Flat. Multiples of this fundamental are called harmonics. So, if the fundamental were, say, 100 Hz in frequency, the second harmonic would be at 200 Hz, the third at 300 Hz, the fourth at 400 Hz, and so on. There is no first harmonic, simply by definition. That's the fundamental frequency instead. The second harmonic, fourth, sixth, etc., are the even-ordered harmonics, and the third, fifth, seventh, etc., are the odd-ordered harmonics.
Musical instruments all produce harmonics to varying degrees. That is what gives them their identifying characteristics, so you can tell the instruments apart. Even-ordered harmonics are pleasing to the ear (consonant), while odd-ordered harmonics are irritating (dissonant). Most musical insruments have mainly even-ordered harmonics, but reed instruments, like clarinets and certain pipes in organs, have odd-ordered harmonics as well. These are all "natural" to the musical instruments. When the music is reproduced on a hi-fi system, harmonics are introduced that were not there to begin with. This is harmonic distortion. Most of it comes from speakers, but some comes from the amplifiers too. Levels above 0.5% harmonic distortion (0.5% of the energy is distortion, i.e., not part of the original signal) are audible. In order to lower the harmonic distortion, some manufacturers add negative feedback, which is signal from the output that is inverted and sent back to the input. This does several things: flattens the frequency response, lowers the output impedance, and lowers harmonic distortion. If it is not done correctly, however, the amount of lower order harmonic distortion (second, third) is reduced, but the amount of higher order harmonic distortion (fifth, sixth) is increased, and this is audible. Too much sibilance (the "S" in the human voice) is an indicator of problems with negative feedback. Although the specification sheet may state a low level of harmonic distortion, the actual sound may therefore be worsened.
If you look at the spec sheets for many high-end amplifiers, the harmonic distortion may state a value that is higher than some of the lower priced amplifiers. The high-end amps don't need to use as much negative feedback because they are better designs in the first place. So, although the spec sheet numbers look worse for the high-end amp, it sounds better. A square wave results from taking the fundamental frequency and adding an infinite number of its harmonics to it. "Clipping" is defined as when a certain amount of harmonic distortion is present, usually 1%. The more harmonic distortion present, the more the waveform looks like a square wave.
When making a square wave response test, if the resulting corners are rounded off, this indicates that higher frequencies (harmonics) are being deleted. Some would call this being "bandwidth limited". When only the leading edge of the square wave is rounded, this is somewhat different. To our ears, when the leading edge of the square wave response is rounded, the sound is a bit smoother than if the square wave reponse has sharp corners, although the sharp corner response is actually the more accurate. Again, perception is the key. If it is pleasing, then it really does not matter if it is true "hi-fi" or not. Tube amplifiers distort with mainly even-ordered harmonics, and some as high as 10% distortion, yet tube fanatics love the sound of them. The even-ordered harmonics add a richness to the sound, sort of like the harmony parts in a barbershop quartet singing louder. A "glorious mid-range" as tubeophiles say. Humans are hedonistic, so if it feels good, we do it, even if it is not "correct". That is what's important.
To us, cables and interconnects make a difference. But part of the problem is that the differences are subtle, and you have to listen to a lot of cables to begin picking up on what the differences are. Once you have identified the differences, then it is pretty easy to hear differences in subsequent listening to other cables. I don't think there is a law of diminishing returns here, because we have heard some really good inexpensive cables that we like better than some of the more expensive ones. For example, the Kimber PBJ Interconnects ($60/pair) and AudioQuest Jade Interconnects ($25/pair) are great. There are so many variables involved, such as number of conductors, size of conductors, shape of conductors, insulator (dielectric), the final price of the cables is not really the basis for judgement. You just have to listen to them. Whether you will like the sound or not depends on your perception. Very subjective, and therefore, very controversial.
AC-3 and DTS have full range to all the channels except the LFE (subwoofer). So, it would be best to have an identical set of full range speakers for the front and rear. In order of importance, I would say that having the same brand is first, followed by having full range all around. The subwoofer can take care of the sound that is lost by smaller speakers, although some ambience is not recovered. You may want to eventually get another set of Mirage 595is for the rear. Two different brand subs will not cause a problem, because low frequencies don't have an audible tonality. We use three different brands in the home theater test lab. As far as crossovers go, you may have to set each sub at a different low pass frequency if you run one from the LFE output on the AC-3 decoder and the other from the subwoofer output on the receiver, or if you run one with the rear speakers and the other with the front speakers.
Q Like anybody else who reads your online magazine, I truly appreciate and feel
that you've done a fantastic job of presenting the "true facts" about a lot
of things that a lot of so-called "hi-fi magazines" out there "forget" to
mention.
A few months ago, I bought a copy of ###### Magazine, and
they had an article comparing many LCD projectors from Sony, Sharp,
Zenith etc. After reading the article I still don't know what I should
buy for my first projector because they recommended all of them!
The only useful information that I could get out from that article is
that it said the Sony VPL400Q has 1.5 million pixels with video grade
and the Sharp has about 1.0 million with data grade.
I'm trying to determine the best LCD projector to buy with a
$4000-$5000 budget and I don't want to make a mistake. It seemed that
you didn't mention much about LCD projectors (I read most of your Q&A)
in your articles. Could you please give me some advice on this topic?
Which one should be more compatible with the future HDTV and DVD format?
A While LCD projectors have come along way, they still are not truly there
yet. They do have some good points, they need no convergence, you just plug
them in and go. They can deliver a fairly bright picture with their light
bulb. They are relatively inexpensive compared to CRT projectors. But they
do have some bad points. First is the "screen door" effect (the image on the projection screen looks like it has been stenciled with a screen door). Each year they
are able to reduce this effect. Some are not even visible, and these are usually
the pricier ones. LCD projectors and the new DLP projectors just can't
produce good blacks. They end up being kind of washed out and gray. Some
companies are doing all they can to make them great. Both Vidikron and Runco
are working miracles with them. For example, the Runco LCP-550 LCD is a
high-end projector at $8,995. It is pricey but it now includes Faroudja
video technology. You get the Faroudja color decoder, the BEST NTSC decoder
there is! A couple of the LCD projectors on the market are offering
component video inputs, which is a must. I believe both Sony and Vidikron
have this on their latest models. HDTV-compatibility would require that the projector be able to scan at 63 kHz (four times the basic NTSC scanning rate of 15.75 kHz), and have RGB/sync inputs. As long as the projector has an S-Video input (preferably component video inputs), it would be compatible with existing DVD players (in order to get the best picture).
Q I took some good advice from my first post about dealing with my
humming problem in my system, which was caused by my cable TV.
I went to Radio shack bought the 300 ohm to 75 ohm transformer, and the 300
ohm to 75 ohm transformer, hooked together the 300 ohm ends, inserted it into
my cable line at the wall jack, and PRESTO, the hum was significantly
reduced.
The problem, I still have a slight hum, but it is definitely noticeable when
there is no sound (music) or very low level parts of certain songs. This happens
obviously when I have both my pre-amp and amp on. If the amp is off, no
hum, same if I turn the pre-amp off, but there still exist a very, very
slight hum, with the amp, that is barely noticable though. Here is my system
rundown for reference:
amp -- Parasound HCA-806 80 watt x 6 channel
pre-amp -- Rotel RSP-960
CD player -- Parasound C/DC 1500 changer
front mains -- B&W P5
center -- B&W CC6
cables -- Kimber PBJ for the preamp-to-amp front speakers,
and older AudioQuest from CD player to preamp.
12 AWG Prolink (3 runs of 15ft. each) speaker cable
Radio Shack gold audio/video cable (15 ft run) from HiFi VCR
to preamp.
So, how do I get rid of the rest of this darn hum. Do you think it's the
unshielded PBJ cable?? I have also heard folks say removing the ground from
the amp will work, but I really don't want to do that. I have all of the
above components plugged into the same standard surge protector from the
same outlet. The TV/VCR/cable is plugged into a different outlet on the
other side of the room. Any help to reduce this hum would be greatly appreciated, thanks.
A Getting rid of all the hum in a large system (which you have) of separates is almost impossible. What I have found is that hum is very much affected by the way the cables are laying together. You can try shifting them around and listening to the hum level. Also, you might try plugging your TV and VCR into an extension cord which is then plugged into your surge protector, just to see if the different wall outlets are causing a ground loop. Some products depend on the ground connection, so it is, indeed, wise not to disconnect it. To reassure you, though, I have never been able to completely rid our systems of all hum. We have learned to live with small amounts of it.
Q I need some advice on speaker compatibility if is there is such a thing. I currently have a Yamaha 670 with a pair of B&W 602s. I moved away from the dealer that I purchased the B&Ws from. However, I found a reputable dealer
that does not carry B&W in my area. They suggested that I go with the
Paradigm line. Is this a good choice for a center, sub, and rears to top off
my Home theater system? And do you feel this is a good choice with my
current system?
A Your new dealer is recommending Paradigm because that is what they sell. Paradigm is fine, but you really should have the same brand for the other speakers. I would suggest finding a B&W dealer and getting another set of 602s as well as one of their center channel speakers. Contact B&W's website for a list of distributors [click here to go to their website]. They can be e-mailed from there for a dealer in your region. Having the same brand of subwoofer is not as important, so get whatever sounds good to you.
Q My system presently consists of a line doubled (LD200) front projection (Barco 808) system with Aerial Acoustics center & surround speakers. The left and right speakers are Sonus Faber Extremas. So the music system
actually links with a home theater one, with the Theta Casablanca
processor's left and right channels' analog outs connecting to an Audio
Research LS5's line level inputs (feeding the VT150 monoblocks). The screen
is 84 inches diagonal 4:3. Subwoofer is Velodyne.
What is the best position for the Sonus Fabers relative to the
screen? The Sonus Fabers need a considerable space behind them, but this
causes the soundfield and imaging to be relatively detached from the
screen, which descends against the front wall. If the Sonus Fabers were to
be pushed back closer to the front wall, which would improve the soundfield
and imaging for watching movies, then the 2-channel music only soundfield
and imaging would deteriorate. The electric screen cannot be moved closer to
the speakers because then the viewing distance gets too close. I hope that
you understand the problem here. Is there some sort of a compromise?
One simple but costly solution is to get a new pair of left and
right speakers and place them (along with the center) on the same
plane/axis as the screen.
A There are several possible solutions. One would be to put the Sonus Fabers close to the wall with some heavy wall treatment (sound absorption) behind them. You might also increase the distance between the two Sonus and toe them in more, with the speakers close to the wall. A third would be leave the Sonus away from the wall, turn off any time delay in the center channel, and add some time delay in the rear surrounds.
Q I would like to buy an RP TV monitor (no tuner, no speakers or audio amp, no features like PIP) with component/s-video/composite inputs.
My
thinking is that I will be able to use my VCR's tuner to watch cable. The DVD
signal will go directly to the TV-monitor. Is there a flaw in this
reasoning? If not, why is this kind of product almost non-existent? If
there are monitors like this will you please name a few?
A Sony used to offer a 32" XBR set that had no tuner, and they billed it as a
monitor. I thought this was a great concept. You could get the same
picture quality as their top of the line model at a lower cost because
you did not have the extra "junk" that adds up the price. I have not
seen this since!
I believe this is a niche market, most consumers want to be able to have a
tuner, PIP, Dolby Surround and the kitchen sink in their TVs, at least that
is what the manufacturers think. Ampro sells their low end data grade
projector in a RP box with no extra features for around $6,000. But this set requires
a line doubler, another couple of thousand. Until the TV people get enough
people asking for this, you probably will not see it.
Q I'm in the process of purchasing a used Meridian 565 and 518. I've
been looking
at these for a long time and am looking forward to upgrading my whole
system.
I currently have a Sony DVD player, Pioneer LD (analog-only out), and
Hitachi VCR. I plan to use the system about 75-80% for home theater. We're
looking to add DSS sometime this year (probably with a digital out).
Our family-room (A/V room) is 14 x 8, but the usable space is much
smaller due
to its configuration. In one long wall the TV is mounted in an old
converted
wet-bar. The back of the room (opposite the TV) opens into the
kitchen. In the
center of this wall is a kitchen counter/pass-thru with walkways on
either side
of the pass-thru. Not ideal (but we can't afford a new home right
now).
I'm looking for suggestions in three areas:
1) I'm not sold on the 562V due to price and lack of video
flexibility (no composite to S-Video, no composite). Plus it
seems overkill for audio right now when I only need to mix
two analog channels into the 565. Any suggestions? Is there
even a decent low-tech (high audio-quality) solution, even
if it means I have to get up and walk across the room to
switch between analog sources?
2) I also need an amp and speakers that will go well with the
Meridian gear. Of course, Meridian speakers would be nice,
but at $5000+ per pair (for their low end DSP5000) you can
burn a lot of money. Any speaker and amp suggestions?
I've heard Acurus and McCormack are good, but I don't know
much about them, including what they cost. I've looked at
the Sunfire CinemaGrand but haven't been able to do any ABX tests.
When it comes to speakers, well, there's just so many options
I don't know where to start. Front L/R speakers won't be much
problem space wise. The center will be tricky, but doable.
Due to the room configuration described above, the rear
speakers are going to be tough.
Would it be better to skimp a bit on the amp and buy better
speakers at the start? Which would be better to upgrade later?
3) I need to add a subwoofer too. Due to space constraints I'm
thinking the Sunfire would fit real nice, easily under an
end table in the corner of the room. This seems to be the
ideal placement for it per yours (and other) reviews. Is this
a good choice? Or should I look to something else?
Thanks for your help and advice. I've found your reviews interesting
and
informative over the past half year (since I found your site). In
particular,
Stacey's positive reviews have helped influence my decision to look
long and
hard at Meridian.
BTW, as a side question, how do you select components for evaluation? I
didn't see anything about this on your web site but I might have missed
it.
A Meridian has a new version of the 565 called the 561, it is a combined
562V and 565 in one unit. The 565 only has one analog input, so you will need a switcher. It also has
two digital inputs, 1 coax and 1 toslink (optical). Monster cable has a little 4 channel A/V
switcher coming in a couple of months, and it is part of their new Entec line
headed up by Peter Madnik (Former Audio Alchemy Guru). If you are not using
the 562V, you will have to plug the analog input directly into the 565,
bypassing the 518 altogether. The 518 only has digital inputs, so you could
plug your Sony DVD into there.
I (Stacey) am currently using the Sunfire CinemaGrand amp, and it works
wonderfully with the 565. I have it set up at this moment with 2 pairs of the
Mirage OM-6 loudspeakers (review coming), and I am very happy. The OM-6s are around $3,000 a
pair, but they have some new lower priced Omni-Polar speakers coming soon.
Remember, most speakers are damaged because of under powering them rather than over
powering them. I would go for the nice amp now and start with some smaller
bookshelf type speakers. B&W makes some nice speakers for this.
The Sunfire Subwoofer will fit virtually anywhere, it is so SMALL! (It is small
only in size, not performance.) They now have a MK II Version of their
sub, and we hope to have one soon for review.
Products for review are submitted by the manufacturers (e-mail, telephone, or snail mail request to submit the products), and by our own requests when we see or hear a product that looks interesting. The que for product review is growing with our reputation, and we are going to be adding some writers pretty soon. John Busenitz (an electrical engineer) has joined recently, and his first essay will be published in a week or so.
� Copyright 1997
Secrets of Home Theater & High Fidelity
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