A friend of mine bought 3-piece sound system some time ago, and then asked me for some tips. We did a long letter exchange. Here are some of the topics we discussed. As you will see, we started from very particular questions and went to very general ones. I am explaining this because the thread starts with a question about the subwoofer. 2 piece sound systems have no separate subwoofer (which could be placed in the center of the room), but this does not make the information below irrelevant for them. Just read.
Warning: there IS some reality cracking near the end, but the rest could be pretty boring ;) If you are really interested in this stuff after reading this, find some scientific book/articles/etc... I do not claim for absolute exactness - some of the things I've learned by trial-an-error ;)It should be somewhere laid steady on the floor. If you lift it higher, you lose some of its sound. It doesn't matter where exactly it is - frequencies below 300Hz cannot be recognized as a direction, only as a presence or absence ;) However, don't be disappointed if you are ABLE to locate them - single signal of 100HZ could have many harmonics (odd or even), so if the subwoofer is not PERFECT one, you recognize its location, more or less.
Well, don't, it will make a resonance with the walls there. Every material, or structure, or whatever has its own resonances. Every distance between two final points (walls) has its own also. It is simple physics (positive and negative waves of the reflection/resonance): If a particular frequency hits some positive resonance of the distance, it will amplify. And if the frequency hits the negative resonance, it will dampen. In result there will be distortion of the resulting sound, because some frequencies are amplified, others are dampen, and the rest are not touched.
Big sound in a small distance is bad (too loud) - you will start to hear things (distortions) you should not.
Too big, or too small - it does not fit. But, you should know that BIG sound in small room is much worse (and even dangerous) than vice-versa.
The sound resonances of the speaker are multiplied by the sound resonances of the distances to the walls/between walls. That's why a room for listening to sound should be with different sizes in horizontal / vertical. Otherwise, you have a BAD sound. If, for example, the room is a cube 2.5x2.5x2.5 meters, resonances (possibly at 70-100Hz) will TRIPLE; Your sound box (or speaker) could have same or near resonance; all the resonances sum up, and the resulting sound IS BAD. If the room was 2x2.5x3m, the result would be not so bad, because it would have three different resonances.
At low frequencies the source of the sound is not only the speaker itself, but also the walls of the sound-box. That's why it is very important what material they are made from, and how far they are from other sound-reflecting walls.
Besides the resonance of the speaker and room themselves, there is additional resonance on the way of the low-frequency sound between the speaker and the walls around. So for the above 2.5x2.5m room, if one puts the speaker in the centre, there will be (e.g.) 1m to each wall. This will cause some very slight additional resonance, at much lower frequency (which could be even a desirable effect). While if the speaker/sound-box is in some corner, then the distance to the walls will be very small, and the resonance will be at a higher frequency AND with much higher volume. This may distort the original sound badly. NEVER put powerful low frequency speakers too sticked to some wall - there should be at least 10-20 cm. Of course, all this have some meaning if the volume of the sound is relatively high (but this does not mean that at quiet levels the sound is not distorted).
If your speaker sounds bad at lower frequencies, you should put some obstacles on the way of the sound between the speaker and/or walls - for example, a single piece of furniture (e.g. wardrobe), or a thick carpet on the wall can do wonders.
Ok, up to here I explained about lowest frequencies. (The harmonics are possible at all frequencies, though). An audio equipment (e.g. amplifier) should not make ANY harmonic distortion (i.e. additional sounds linear-depending on the input sound). while, the playing instruments are making as more as they can. It is THE way to distinguish two violas, for example.
There are also non-harmonic distortions, though, and they are hard to reduce. An amplifier with a coefficient of non-harmonic distortions 0.0001% may cost 100+ times more than one with 0.1%. Non-harmonic means they are not direct-depending on the input signal, but originate from some interaction between the parts in the amplifier and the input/output sound/level/frequency/angle-of-attack and many other characteristics.
For example, bad old transistor radios are distinguished from newer/better ones by that special "Transistor" sound.
Yes. The frequency-spectrum (i.e. how much of any frequencies are there for a certain single sound) of an sound-producing device characterises it completely. That spectrum is put as an base of all sound synthesizers - Roland, MIDI, soundblaster, etc. That's why you should be able to distinguish between an electronic and real piano. Ha-ha - to make an electronic piano sound like a real one, makes it cost MORE than the real one. ;)
The spectrum of a voice is used in some voice recognition systems - not what you talk, but the way you talk, if recognized or not, could open/lock a door, for example. But things there are quite complicated - just catch a cold and ...
It depends on the quality of the recording - can you make a difference between a real violin and recorded one? everything depends on the quality of the recording/playback... Of course, the brain + ears are miraculous spectrum analyzer. The artificial ones are still far, far away...
A little explanation of how sound levels and ratios are measured. Sound levels differ in exponential way: difference = square-root( 10^x ). The x in the above formulae is measured in "Bell"s, but as it is too big, the usable unit is deci-Bell (dB). So the formula for dBs will be: ratio = 10^(deciBells/20), i.e. real ratio of 40dB is 10^(100/20) = 100 times. (Human ear has a vast dynamic range - ratio from loudest to quietest sound that can be heard is above 1000 000 times: 120-130dB).
To measure a sound-level the ratio of the sound to some base is used - usually relatively to the loudest or the quietest heardable-sounds for the human ear. They are person specific, but there are some average "threshold of hearability" and average "threshold of pain". The levels in relation "to threshold of hearability" are measured in positive dB's; in relation to "threshold of pain" in negative (and zero) dB's.
One should be careful not to mix up the sound level (which is an absolute value, but is measured relative to some base) and the level-ratio - increasing or decreasing, which is pure relative.
Now, on to middle frequencies. The human ear has a particular frequency-response characteristic. A sound at 100Hz will be heard less strong than a sound with same level but at 1000Hz. There are a family of characteristic depending on the level (and also on the particular listener, but this later) - for example, at sound level +20dB the difference between MIDDLE and lower+high frequencies is almost 70dB!; while at level near to 100dB the graphics is almost flat.
**
Ear frequency-response:
quiet sound (10-20db)
0| ---
-20| / \
-40| / \
-70| / \
ratio,db|_______________________________
/frequency 20Hz 1kHz 20kHz
loud sound (>80db)
0| _/----------------------\_
-5|
ratio,db|_______________________________
/frequency 20Hz 1kHz 20kHz
To correct this situation, a reversed frequency characteristic should be applied:
quiet sound (10-20db)
0| \ /
-20| \ /
-40| \ /
-70| --_--
ratio,db|_______________________________
/frequency 20Hz 1kHz 20kHz
loud sound (>80db)
0| \_______________________/
-5|
ratio,db|_______________________________
/frequency 20Hz 1kHz 20kHz
...like these (If you ever saw an equaliser, it should be tuned (almost) this way. There are sometimes different curves for different types of music AND, of course, for different homes/halls.)
**
That's why middle-frequency speaker should be of VERY HIGH QUALITY - a human could make difference much easier, because of the higher ear-sensitivity to middle frequencies.
To correct this situation, almost all audio equipments has Loudness or Treble/(Middle/)Bass regulators - to make all the frequencies equally well-heard. Some of the Loudness regulators are coupled with the Volume regulator, thus changing the correction from very deep at quiet levels to almost flat at higher ones, automatically. Or they have equalizer, which is for more precise tuning of the curve, or a special chip that contains many different "psychological" curves - to simulate some more-real "frequency-response" characteristic.
Example: If you are at a symphonic concert, the level is about 100-110DB. If you listen to a record of the same concert in same room in same level, (almost) no need of any corrections. But if you decrease the volume (and/or change the room), in order to have the same feeling you should put some corrections.
And the more your ear is trained, the more whimsical it becomes - e.g. one could make difference between MPEG recording (in which the highest AND most strange frequencies are missing) and a tape/CD recording. Or between tape recording, vynil LP, and Digital mastered CD (but not always). While 95% of people do not make so much difference.
We go now to higher frequencies.
Higher the frequency -> higher the degree of absorbing AND higher the degree of directioning. Some higher frequency speakers have only 10-20 degrees angle of the sound produced - beyond this angle you are hearing not the original speaker sound, but some interference or reflection. That's why there is some specific "stereo-zone" for every different speakers. It is the polygon in which those 15 degree flows are crossing each other, and there you can heard original sound of Both left and right speaker.
There are ways of expanding the stereo zone (without changing the sound recording itself). The effect of so-called expanded-base stereo is to put some part of the left signal into right one, and vice versa, by mixing the left/right electric signals inside the amplifier. Thus the polygon is Artificially made wider; but the sound will become less clear (though you will not mention it if you a listening to some bla-blah kind of sounds/music). Another way is the so-called pseudo-quadro effect - by mixing the (resultant) sounds. Two additional high-frequency-only speakers, between main ones, with swapped left/right, or two additional speakers at the back, again with swapped left and right.
To achieve the best possible stereo zone inside a room one should take in consideration all reflecting or absorbing surfaces there and make some simple calculations (and/or drawing). Do not think that bigger the distance between speakers the wider the stereo zone. If a room is 3x5m, good places of the speakers could be beside the narrow wall (20-30cm from it), half a meter from the wider walls, and directed to the center of the opposite narrow wall. The stereo zone will be somewhere near that opposite narrow wall (draw a simple diagram, and you will see that). If you place the speakers along the wider wall, near corners, the stereo zone will be OUTSIDE the room, or will be very narrow.
Next way is real quadro or using some Digital Sound Processor to "simulate" the missing speakers, compensate for "lost-because-absorbed" sounds and to reduce "loud-because-resonanced" sounds. It works by a reverse engineering of the sound. i.e. What should be run through these speakers, to achieve a certain ear-"sound-image" (this way you could feel you are in a church, in a stadium, etc... - but if you listen only to one of the speakers, it could be very strange).
As you see, listening to music (with greater satisfaction) is an art itself ;)
Hey, I walked you around all the theory of "know-how-to-listen_AND_what-equipment_to-buy", he-he... Now some practical info.
The OLD lamp (vacuum tube) equipment is still used somewhere, because it has (almost) no non-harmonic nor harmonic distortions. The so called MOSFET transistors have nearly same characteristics, but require much less care. Therefore, if one buys a 10-15 year old MOSFET amplifier, IT WILL BE THE best. NEWER ONES are VERY expensive, because people do not care, and only some maniacs choose to buy them. It is possible to buy a good usual non-MOSFET amplifier, but it may cost even more. But it does not make so much difference as speakers.
It is not a company but technology - Metal-Oxid-Silicon Field-Effect Transistor. It is like simulating a lamp, but inside the crystal. The quality is same, i.e. very good.
Speakers: you could have a $200 amplifier + $1000 speakers, which will sound much better than $1000 amplifier and $300 speakers (as it usually is sold). They should be timber (or at least something made from timber if not even more special), and be 2 or 3 way. Up to now my best choice is one big (half-meter-cube) subwoofer specialized on frequencies below 100Hz, and 2 VERY GOOD speakers, for 100Hz and above (such a 3-piece set should be completed by the manufacturer, not by you). Of course, the methods of producing low-frequency sounds have different quality and also matters a lot, but it is too specific. OR, buy two middle size 2-3way speakers (e.g. 30x20x50cm). Buying 2 huge speakers is not a good idea - they need room. Oh, if you put them in a church, it could be exciting, but we usually do not live in churches... while alive ;)
Also, some sound-engineering could boost performance a lot. A room with 4m high ceiling will have much more deep sound than 2.5m usual one. Churches have very high vault-arch ceiling, do you remember ? All that arches, holes, isolation, etc... BTW, that sort of books are a bit hidden. The most nasty thing is, that even if you have an equipment for $10000, if your house is NOT designed for music-listening, you will not get what you would want to. And, re-building the house is a Pretty Expensive Affair - it will be cheaper to have a built-in organ ;)
Not the number, but the specific frequency that became in resonance with the molecular (or higher level) structure of the material; The glass itself has a big internal tensions, so it is breakable easy. Example: if you put your tweeters...
;-) - very higher frequency.speakers - on full power, and run some signal above 18Khz through them, maybe you will not here it, but all the windows around could fall down "in a salt-like-state", i.e. in many small pieces.
BTW, frequencies below 10Hz (around 6 Hz) are dangerous to humans/animals. They resonance with the heart's internal beat and could stop it. So, be careful with SUBWOOFERs. Oh, if you find a subwoofer that is able to produce 6Hz and costs less than $10000, tell me immediately ;) It could be very useful as a earthquake-simulator or something else ;)
Oh, you have very bad idea about tape recorders/players. For the bad ones, yes, you are right. For the good ones... Sometimes they sound better than a CD. You see, an analogous sound, recorded and played through analogous equipment may be better than if somewhere it goes digital and then back (we can't hear in digital ;). The digital one is almost same.
You see, one could buy an all-in-one-sound-boom-box for $100,$200, maybe $500. But really good things cost at least $200-$300 EACH. Tape deck should be more than $300, CD player, pre-amplifier, amplifier, speakers (EACH one of them), etc... So the least total cost of a good equipment is about US$1200-2000 (if new). But don't think that if something costs $2000 then it is automatically good.
Look into cassettes. Take a pencil and rotate the empty roll until a black/brown tape comes out, and look. It should be like mirror; If it has some dashes/scratches... your player is bad.
Take a ear-brushing cotton stick, put it in some clean alcohol and clean the heads of the deck AND the pressure roller(s) (let it "play" with open tray without cassette - it is easier this way).
All cassettes should have clean "pressuring-pillows" (in the middle, just where the head should enter, below the tape). Clean them with something small but sharp, like small knife, or small screwdriver... but very-carefully - sometimes the glue used to hold the pillow there is very weak.
This will not repair the head of your player - cheap heads are quickly worn out, and start to make nasties to the tapes. But it is not bad to have a clean things around... ANd if you buy new one, keep it clean... The mechanical stuff DOES NOT LIKE dirt.
It is a simple mathematics: the analogous play/record is never 100%. It always have some additional noise (regardless if it is 1% or 0.01%). On very good equipment one could make up to 5-6 sequential copies before the quality is lost; on bad ones - one. The video's are even more whimsical - not more than 2 copies.
If you copy a bad record to another cassette, it won't be worse. But if you try to copy a record much better than your equipment can play/record... the result will be not more that you equipment's quality.
That's why the digital sound become so widespread - it could be copied infinite times, and will be the same as 1st record. Note: I'm not saying it will be SAME as original sound, but as the record of it.
Never compare things ONLY with your previous equipment. Try to see/hear many types - expensive, cheap, etc.. IN USE. And always try them in the shop with your own records, tapes, CD's, etc... In the shops they put particular demo-things played on particular equipment in their particular halls/rooms/space/structure/etc, and it may feel OK, but, when you run your own record, or in your own home, it could be dreadful.
I remember when I was buying my speakers for that huge (for my pocket;) US$500 sum, all my friends that somehow knew about it went into the shop to watch/listen to the show. Oh, yes, it was a (1 hour) Show - they still remember it. I made the shop-assistant crazy, because I brought my own CD (Genesis '91), with one particular song on it (No12, the last one), and asked to get it running on full power on that speakers. ALL THE AMPLIFIERS (5 or 6, I did not count all of them that they have there) did not do the job - all they got overloaded. But, I proved for myself, that 1) the incredibly good sound of the speakers is not due to some particular combination/ SoundProcessor/ amplifier dependency; and 2) the speakers are really running 200Watts without problems. While the amplifiers claim to be 250W,300W - ha-ha, they just WERE NOT.
Be careful. In a shop, using some Digital Sound Processor one may make even nasty equipment to "sound" well. But if you have no such/same Digital Sound Processor ($500 or more) at home, he-he, you are deceived.
Oh, this is tough question. It could be 50%-50%, but it depends. Most modern cards costing more than $100 are good enough, but keep in mind, that the sound-reproduction parts (i.e. all that after the sound card generator - i.e. pre-amplifier, amplifier, speakers) should cost MORE than the generating one. Even may be much more in order to be able to listen to ALL that the sound card produces (as internal on-card amplifiers are usually cheap, they are not very good). BUT if it is five times better, you will start to notice/hear flaws - hisses, internal noises, etc... You just should make some reasonable deal. If you are using them for listening music, they should be very-good; if they are only for some stupidities around computers, don't care so much...
Hm, no, I haven't listened to but I have a vague idea. They put microphones on the exact places your years should be, with some additional things, like substitute for the head etc...
But I do know another important thing: if you are listening to a real sound, or one made by speakers around you, BOTH ears hear some part of it. While, wearing headphones, one ear can't hear what the other one can; so listening to stereo headphones is tiresome IF some of the left/right signals are not a bit mixed (remember the widening of the stereo-base above). For example, 5%left-signal+95%right-signal goes to right ear, and vice versa. People think that the headphones are uncomfortable, or that they crumple your ears, or the music is bad, etc... No. The real reason for being tired after headphone session is the above one. So, never use stereo headphones for long time if you have some other choice.
Bad (hurting) headphones are and will be bad headphones. At least, the phones should not cause any direct physical discomfort. When only that "mental" discomfort remains, it is better. But one could have a headache after long listening to comfortable headphones, without actually understanding why. It is so simple - the brain is overloaded with "wrong"-sound-pictures. While if having discomfort headphones, you will try to remove them as soon as possible ;)
As a quality, it should be same. Maybe DVD could put more than 75 minutes on a single CD. But, as every new technology, it will be made nasty, so to make you pay for everything they should or should not do... Keep that good old LPs, cassettes, CDs... NEVER run for a newest "brightest" technology... - though today this is the normal way of choosing anything. People tend to think "the newer - the better", which is not exactly so.
This is the "should-be" way of choosing anything - by thoroughly weighting all the pros' and con's... Yes, I could put an essay.. but who would read it? Nobody.
I don't know. I'm a bit disappointed by the way the people live - they do not give a f*** for such knowledge... They think their grandma had always used CDs, etc... Well, may be some time I'll put such an essay... or my be not... And, such advices are written in many audio/video NON_COLOURFUL books/magazines; does anybody reads them?
As you see, I put an essay. So ?
--------EOF--. SvD Jan'99