What does it mean?

[BigBusa]

For the newbies here (me included) please explain some of the more commonly used terms ...

Timbre match

bass managment

interconnects

biwiring

imaging

There's tons more but I can't recall them right now.

Thanks!

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This message has been edited by BigBusa on 10-18-2001 at 06:40 AM

[myram]

Timbre match - the front 3 speakers all have the same tone to them. This is accomplished by all 3 front speakers having the same tweeters and mid-ranges. It makes for a seamless front stage.

bass managment - Being able to set crossover points, and bass output through your receiver. Thru this you can get your system to sound much better, with tighter bass, and complete coverage of sound.

interconnects - RCA cables, patch cords, or interconnects are all the same. They are the cables that connect your components that use an analog signal. The red & white connectors on your components are analog signals, and they use interconnects.

biwiring - Using seperate amps to power the woofer, and the midrange/tweeter of the same speaker. One amp would power just the woofer, and another amp would power the midrange/tweeter of the speaker.

imaging - The placement of sound to where is is appearing on the screen. If a person is walking from left to right on the screen, the sound should start in the left front speaker, then go to the center, then finish in the left fron speaker.

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Home Theater Page

[dbflash]

I think bi-wiring would be to use the same amp outputs but run 2 speaker wires to each speaker. one wire would go to HF and one would go to LF.

see www.davidmannaudio.com

Bi-amping would use two different amps.

danny

[Ray Garrison]

Okey dokey, here's my take on this... wanna bet there's some difference of opinion on what they mean?

Anywho...

Timbre match: When speakers match in "timbre", they will reproduce "tone" consistently. I know, answer a questions with a question... what's "tone"... best example I can think of is this. The idea that any specific note has a specific frequency is pretty easy to grasp - "middle C", for example, is 440 cycles per second, or 440 hertz. But there's more to it than just that. A guitar, for example, has five different "middle C's" on it. Each string can be used to play a 440 hertz note by placing your fingers at different positions on the fingerboard. however, even though the strings might all vibrate at the same frequency, and thus product the "same" note, they will sound different. Likewise, that middle C produced by an Oboe will sound different than one played on an English Horn, and a trombone sounds different than a French horn, and a flute sounds different that a recorder... you get the idea. When these different "tones" are reproduced on a speaker, the speaker is never going to get them exactly "right" - the better the speaker, the closer it will come, but no speaker is perfect. On a poor speaker, you might not be able to tell the difference between, say, a viola and a cello when they're playing the same notes, and on a good speaker you can probably tell wether two musicians are using cellos produced by the same artisian. The degree to which all the speakers in a system, whether two channel or multichannel, reproduce the same, consistant "tone" (or, another way to look at it, if all the speakers screw up the sound to the same degree in the same manner) is how well matched they are in "timbre". This is more of an issue with surround, or multichannel, systems than it is with two channel systems because, in a two channel system, the two speakers are usually either identicle or mirror images of each other, whereas in multichannel setups, the speakers may have different physical shapes and different radiation patterns, making timbre matching a greater challange.

bass managment: again, mainly in multichannel setups... if you have a system consisting of several little bitty speakers and a great walloping subwoofer, you'd like to be able to tell the electronics to take all the bass frequencies, keep them out of the main speaker array, and steer them to the subwoofer. Conversely, if you have all big, full range speakers and no subwoofer, you want the electronics to steer all the bass to the main speaker array. If you have full range front channel speakers and little rear channel speakers, then you want the bass in the front channel to go to the front channel, limit the bass going to the rear channel, and steer the rear channel bass to the subwoofer. This is bass management.

interconnects: aka patch cords. The things that connect your DVD or CD player to your receiver, or your preamp to your amp, or your turntable to your, well, you get the idea. Interconnects have different electrical requirements than speaker cables - instead of carrying lots of power (maybe hundreds of watts - say 5 amps at 20 volts into a 4 ohm speaker) from a VERY low impedence output (the amp) to a fairly low impedence input (the speaker), the interconnects are carrying a (typically) maximum of 2 volts and practically zero amps from a fairly low impedence output (the preamp) to a high impedence input (the amp). Interconnects range in price from free (included with equipment) to many, many THOUSANDS of dollars. See, for example, this link: http://www.nbscables.com/reviews/ces2000.html

biwiring: using two sets of wires to connect your speakers to your amplifier. SINGLE amplifier. Using two or more amps to drive one speaker is bi-amping, not bi-wiring. The reason to bi-wire speakers: some speakers are designed so that the parts of the crossover that go to the tweeter and the woofer are physically separate constructs, which are then connected together by placing "jumpers" on them that connect both parts together, so you can run one set of wires from the amp to the speaker. Some folks believe that separating the two halves of the crossover, and connecting each half to the amp with its own wire, sounds better. Note that you are connecting both of these wires to the same binding post on the amp, so from an electronic circuit design perspective, it's pretty tough to make a case that there's any difference between running two sets of wire from the amp to the two halves of the crossover, or simply running one wire and jumpering the two halves of the crossover together.

imaging: the ability of a music system to convey to you specifically where, phsically, a particular sound was created during the recording. For example, if we record a guy playing a guitar and another guy five feet behind him and a bit to the left playing another guitar (acoustic guitars, so we don't have to worry about where they put the amps and speakers when they made the recording), you'd hope that when you play this recording back, that's how it would sound. That is, you'd be able to say "Hey! There's a guy standing RIGHT THERE playing a guitar, and there's another guy a little behind him and to the left playing another guitar!" Systems that image poorly (and some folks accuse the Klipsch Heritage line of this, though that's not been my experience) might be able to convey to you that there's two different guys playing two different guitars, and you might even be able to say what BRAND of guitar if there speakers have excellent tone and really, really good timbre match ( )but you couldn't tell exactly where they were standing in relation to each other. On the other hand, there are some speakers that image like a sunnofabitch (Acoustic Energy AE-1's are my all time champs) but have lousy tone and timbre, to the point where you could tell if the guy playing the rear guitar LEANED BACK on a particular note, but you couldn't tell whether he's playing on steel or nylon strings.

Note that some of the more artsy-fartsy amongst us have started using two different terms that somewhat overlap - imaging, to refer to the ability to place performers within the left to right and front to back space, and "soundstaging", which seems to refer to how much space there is between each of the individual performers.

Boy, that was fun.

Ray

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Music is art

Audio is engineering

[dougdrake2]

Ray - What in tarnation are you doing running an IT shop? Too bad you don't get paid for your audio expertise. Thanks for that!

DD2

[BigBusa]

Wow, Thanks! You guys know your shiite!

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Does anyone have the Olympus Camedia CD that I could borrow via the USPS?

[Mr. Blorry]

I must agree with DD. That was spectacular, Ray. We need to box that up and place it somewhere on this site under the heading "Stereo Stuff 101"

[Marvel]

Uh, Ray,

A concert A is 440 Hz, so a middle C, slightly lower is around 261.?. I don't have my chart here at work.

Guess this makes up for my trying to explain power/watts/dBs!

Every octave up is a doubling of freq., so an octave higher than the A above middle C is 880 Hz. Going down an octave would cut the freq. in half.

But really Ray, your exlanations are GREAT!

Marvel

[discorules]

Hey Ray. You da man.

Do I have permission to reproduce or retransmit your eloquent explanation or are you gonna me charging keashhh?

[WMcD]

I might add to what Ray says. Not that I disagree. It is just a bit more complex. I'll try to give you the big picture, and integrate all the elements.

Musical notes have a primary frequency. Like A above C is standarized to 440 cycles per second. That would be a pure frequency if you're looking at the output of an electronic signal generator.

Musical instruments do not produce pure tones. Rather, typically, they produce additional overtones, or harmonics. Different terms for the same thing. These are frequencies which are multiples of the primary frequency. They are "octaves" up.

Note the term "octave" is based on eight notes. Eight whole notes up from A-440 is A-880 cycles per second, this is A again. You can see this on a piano keyboard. And you can keep that up for several octaves. Usually the strenght of the overtones vary from one instrument to another. Giving them a characteristic timbre.

Timbre describes in a loose way, the nature of overtones' power. A given note (same fundamental) played on different frets on a guitar will sound different. This is because there are more, or fewer, overtones, or harmonics. The timbre is different because the differing higher frequency content at any given octave up. Different instruments have different timbre while playing the same note, for the same reason. But they are all multiples of the fundamental.

Fuzz generators on electric guitars increase the overtones. This is because they clip the tops of the output signal from the guitar.

In a vague way, this a consideration of the freqency output spectrum of the instrument while playing a single, plucked string.

This is a type of "harmonic distortion". There are some second, third, fourth, etc., harmonics added to the primary or fundamental frequency. It gives musical character.

Turning to speakers, "timbre matching" is not a very good term. This is because it implies that the speaker is creating harmonic distortion. That may be so, but that is not the issue. I'll get to the "issue", below, but lets look at harmonic distortion, since the term is widely thrown about.

Harmonic distortion is the addition of the harmonics. It is not that harmonics are distorted. It is simply that harmonics have been added. The addition is the distortion. The waveform looks different. It, it self, is distorted.

This may occur, particularly when a speaker or amplifier is over driven. Lets assume you put in a pure tone of A-440. If there is harmonic distortion, you'll get 440 plus some 880 and some 1760 and some 3520 cycles per second ("Hertz" = cycles per second.). It occurs based on the same principle as the fuzz box. The tops of the pure sine wave is clipped off. Musical instuments do it all themselves.

I don't want to get into this too much more. But we're shifting back and forth between the 'time domain' and the 'frequency domain'. Take it as a fact that when a sine wave (time domain) is clipped, it creates harmonics (frequency domain). Frequency domain is what we see in a spectrum analyzer, or frequency response plot.

You may have read that harmonic distortion is not particularly objectionable. This is probably because, as mentioned above, the instrument is already putting out harmonics, so it is difficult to discern some additional harmonic content.

Lord I'm going off topic, and going farther. Let me add that PWK's thesis is that inefficent speakers have a nasty trait, which is, roughly, Doppler distortion.

You know Doppler effect. Train is coming toward you and sounding a whistle. When it is coming toward you, the pitch of the whistle you hear is higher than actual whistle frequency. As the train moves away away, the pitch of the whistle becomes lower. You hear" Eeee, Haaaaa.

Please observe that the actual frequency of the whistle doesn't change, but what we hear does. The motion of the train is causing a distortion of the note, or pitch, or fundamental frequency, of the whistle.

Take an ineffient bass driver producing a bass note with large excursion, and a treble note, too. The motion of the diaphragm is the train. The treble note is the whistle. There will be a shift of the perceived frequency of the treble note, as the diaphragm moves back and forth with the bass.

Here, it is not by an octave. Rather, the bass note changes the frequency of the treble according to motion. It can be very annoying to listen to because it induces non harmonic frequencies. The original instrument was not putting out these shifted treble frequencies. Just as the train whistle did not.

This is a type of distortion because the speaker is putting out a frequency which was not put into it. Call this distortion in the frequency domain.

What to do to reduce the Doppler effect? Putting a horn, somewhat like a megaphone, in front of the diaphram makes it more efficent. More efficent, less movement in the bass. Less movement . . . the train is not moving as fast. So less Doppler effect in the treble. Overall, a cleaner output. The output of the speaker tracks the input better.

So, back to the "issue" of timbre matching in speakers, and particularly, HT system with a smaller center speaker.

Actually, it is simple frequency response. No consideration of harmonic frequency or Doppler effect, with added frequencies. There may well be no additional frequencies created, be they harmonic or Doppler.

As mentioned by others, in a two channel "stereo" system, the left and right speakers are the same design and have the same frequency response. The frequency response may be flawed. But at least it is the same for each. If a signal is panned left to right, they have the same problems and the frequecy response doesn't change during the pan.

But lets add a center speaker. A good idea in my book. It allows better imaging. Your other question.

First case is that the center speaker of is the uniform, exact same design and therefore frequency response as the flanking units. Suppose a speaking actor, or sound effect, moves from left, to center, to right. This is "panning".

Even if the overall frequency response of the individual speakers is flawed, the output spectrum does not change during the pan.

This might be called "timbre match". But it doesn't tell the story.

Second case. The center channel speaker is not of the exact same design, perhaps smaller. Its frequency respose is different, perhaps lacking bass response. (Not adding overtones, though. So this is not a timbre issue, about overtones or harmonics, simply frequency response.) Now as there is a pan from left, to center to right, the bass drops out in the center channel. Seems un-natural. Sounded good left and right, but something is wrong when panned center.

The second case I've described above points out bass response. But that is just an easy to understand "thought experiment".

A more critical area is the midrange respose of the center speaker. This is where our hearing is most sensitive to frequecy response anomalies. Our ears are not good at hearing the direction of bass. This is why center and surround speakers can be set to "small" with a 70 Hz roll off. Let the subwoofer do the bass work.

None the less, it is critical that the frequency response in the midrange horn be the same in the center channel speaker as it is in the flanking speakers. It might not be called bass or treble but it is a matter of uniform response over the lower and upper ranges of the midrange.

Klipsch does this by using the same horn and drivers in the center channel midrange and tweeter. Other manufacturers do this too. Lacking that similarity, the overtones, harmonics, as generated by the insrument are not the same. Which is bad.

Is this "timbre matching" between speakers? In a very loose sense, yes. If the center does not have the same frequency response as the flanking units, the overtones from the instruments will not be reproduced correctly.

Okay, let's review. I agree with the concept of timbre in instruments. Harmonics. Some forms of distortion in speaker design recreate the overtones. However, timbre issues in three channel speakers are purely frequency response and not added frequencies.

I talk too much.

Regards,

Gil

Timbre, to my understanding, is the

[Ray Garrison]

See, the reason I run an IT shop is 'cause I say things like "middle C", for example, is 440 cycles per second, or 440 hertz" without really thinking about it.

A above middle C is 440 Hz, as both Gil and Marvel mentioned.

And yes, the reason that the different guitar strings sound different when playing the same frequency is that the harmonic overtones produced by the strings are different, and the total "harmonic envelope" that you hear is different because these harmonics are different.

I agree that the difference in timbre comes down to differences in frequency response, but would point out that it's very difficult to wrap your head around just what we mean by "frequency response". Do we include off-axis sound as well as the on-axis response, or not? If we do, and this will probably be different for different cabinet shapes even if the drivers and horns are identicle, how do we weight the off axis response vs the on axis to come up with a "this is how these things sound" specification? For a couple of extreme positions on this, look at Stereophile and Sound and Vision. Stereophile measures on axis response, and both horizontal and verticle deviations from this on axis response in excrutiating detail at five degree intervals, but these response curves are frequency at odds with what the subjective reviewer is writing that he heard. On the other hand, Sound and Vision prints ONE frequency response curve, with an arbitrary weighting of on and off axis response, and measures every speaker the same way regardless of the design of the speaker. I'm not sure EITHER method helps predict whether any two given speakers sound similar or not.

Ray

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Music is art

Audio is engineering

[Colin]

Great, great, great stuff!

my .02:

The term "imaging" is used loosely to discuss how well the stereo or HT set-up creates an artificial illusion of the artists and their musical instruments. We say that properly positioned speakers produce a great image. It is also used to describe the location of the artists and the musical instruments. We say the image of the guitar player was behind and to the right of the singer at center.

The image term does overlap with the soundstage term. But since both illusions are so important to me, let me clarify how I might use them differently.

Soundstage generally refers to the height, depth and width of the entire image. This includes how much space there is between the separate images. How big or small is the space that the "images" occupy? Was the singer and her piano tightly confined between the two front speakers, or did their images seem to be wider than the width of the speakers? How deep is the soundstage? If you pull the speakers out from the front wall - does the depth of the image increase?

Soundstage also refers to the shape or area of the illusion. The promise of 5 surround channels is that a soundstage might possibly be created which encloses the listener on all sides.

Creating an illusory soundstage with distinct sonic images within is not actually difficult to accomplish with two speakers. Put on a favorite piece with just a few instruments. Drag the speakers 2 to 4 feet away from the side and front walls. Go sit stereo center and tell me WHERE you hear the sounds coming from when you close your eyes. Is the singer coming from one speaker or the other? Or does she appear as if from some magical point right in front of you?

How successful any of this is depends on a list longer than the Ten Commandants. The speakers must be properly positioned away from too much and too little reflection. They should be the proper height. They must be in phase. (what? oh, not right now, we will discuss phase and test CDs a little later on) The walls may need dampening. The amplifier can aid or hinder the sonic illusion. The pre-amp may or may not help with this.

Recording quality makes a very big difference. Many recordings will crowd the main instruments together in the center channel. This helps create a focal image, but the soundstage may not be very wide and the images will sound like one is on top of the other. This may not be bad. The singer will sound as if she and the bass player, for example, are sharing the center of the stage of sound. The old black vinyl discs can be very good at this.

The amount of mid and upper bass will make a difference. The location of the mid and upper bass woofers will add to the 3D illusion.

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HORNS & subs; leather couch & feet up; lights out & tubes glowing!