time delay for newbies ?

[seti]

I googled "time delay" but didn't find what I was looking for. I was

wondering if anyone here could point me to some documentation or link

on time delay. I am trying to figure out why the Jubilee's in Hope, AR

sounded so bloody good except for the obvious brilliant design. I

remember the Behringer electronic crossover and understand that pretty

well but I don't really understand the whole time delay subject. Any

info much appreciated!

Seti

[Duke Spinner]

well ...say in the K-Horn ....

ya got a 6' bass horn, a 2' mid horn, ;n a 1" tweet

all the motors are on different centers

sooooooo ........the sounds all reach you at different times..

and we haven't included what the passive xover does to phase angle

Dr. Who dug up a figure i had seen before, on the KH ....6ms delay on the bass horn

that is responsible for the "tubby" bass

[seti]

So if you are using time delay you are making the bass bin, squaker,

and tweeter reach you at the same time? Is there an audible difference?

How much does this affect the way the say khorn or jubilee sound? What

were PWK's thoughts on this?

thanks

seti

[tofu]

i predict a long thread ahead

[mikebse2a3]

So if you are using time delay you are making the bass bin, squaker, and tweeter reach you at the same time? Is there an audible difference? How much does this affect the way the say khorn or jubilee sound? What were PWK's thoughts on this?

thanks

seti

Ah! if it was only so easy as to add time delay.

Adjusting for time delay on speakers with drivers mounted in different Vertical and Horizontal planes faces very real limitations because any correction adjustment you make will only be good for a certain listening axis. If you move off that axis you will loose the time alignment you have just made. Some manufactures deal with this by using coaxially mounted drivers and their crossovers being adjusted into time alignment although most are still comprimised designs due to the fact that the coaxially mounted drivers just cover the mid/high freq. ranges and they are added to low frequency drivers mounted in different vertical planes. These will have a very defined listening window in which the time alignment is acceptable.

The orginal Quad 63 and its later versions if I remember correctly might be one of the few speakers that had good time alignment in both its vertical and horizontal listening axis's. If I remember correctly also there was a Professional Monitor with 15" woofer with a coaxially mounted Horn that was designed with good time alignment.

anyway one sight you can read about some of this is

Click here: THIEL Technical Information

you might also check out www.vandersteen.com

By the way there are other time delays that you should be concerned with and those are created by the reflections from the walls/floor/ceiling that reach you within a 20ms to 30ms time frame after the first arrival from the speaker has reached you. These create very audible problems with clarity, imaging and tonal balance.

Some books that describe the importance of this are;

Sound System Engineering by Don Davis and Carolyn Davis

The Master Handbook of Acoustics by F. Alton Everest

mike[]

[pauln]

Time delay is interesting from a viewpoint of sound, but as far as listening to music, you don't hear it. It is measurable by instruments, but not your ear/brain - we don't hear a complex wave as a complex wave; we decompose the complex wave into its separate frequency components and hear the sound as different pitches. PWK never believed staggered speaker distances made a hoot of difference to the ear - he was right.

[Duke Spinner]

, but as far as listening to music, you don't hear it. It is measurable by instruments, but not your ear/brain -.

Apparently that's not what Altec, and JBL belive

Altec ...604, point source, with delay/ phase in the X-Over

JBL ....4430 ....4435....L-200 ....L-300....250 Ti....XPL.....Array series ----- motor alignment

[DrWho]

The concept behind time-delay is to delay the signal going to the drivers

that are arriving earlier in time. So in the case of the khorn, the tweeter is

delayed 7ms and the squaker is delayed 6ms so that all the wavefronts

arrive at the same time.

When using a vertically centered system (aka, the drivers are all

centered and directly above each other), time-delay correction will

inheritantly correct for differences in the depth plane, but also in

the horizontal plane. However, you will have issues in the vertical

plane - where as you move around, the distance between drivers changes.

So ideally you would want them mounted as close together as possible.

(Similarly, a horizontally centered system (like most center channels)

can be corrected for in the depth and the vertical planes, but will

have issues in the horizontal plane).

As far as the audibility goes, here is a demo track for you to hear for yourself:

http://forums.klipsch.com/forums/622024/PostAttachment.aspx

Btw, within a certain window of time our ears no longer distinguish

between individual seperately occuring sounds, but rather interpret the

"average sound" over that period of time. The end audible result is a

smearing or harshness associated with the "two" sounds being merged

into one. So even though the delay isn't sufficient to warrant being

heard as two distinct and different sounds, our ears still percieve an

overall difference between a time-aligned and a time-delayed signal.

I believe Heiser is the one leading research in this area and you can find his writings "TIME DELAY SPECTROMETRY

edited by John R. Prohs." here:

http://www.aes.org/publications/anth.cfm

(all the way at the bottom)

[pauln]

The concept behind time-delay is to delay the signal going to the drivers that are arriving earlier in time. So in the case of the khorn, the tweeter is delayed 7ms and the squaker is delayed 6ms so that all the wavefronts arrive at the same time.

When using a vertically centered system (aka, the drivers are all centered and directly above each other), time-delay correction will inheritantly correct for differences in the depth plane, but also in the horizontal plane. However, you will have issues in the vertical plane - where as you move around, the distance between drivers changes. So ideally you would want them mounted as close together as possible.

(Similarly, a horizontally centered system (like most center channels) can be corrected for in the depth and the vertical planes, but will have issues in the horizontal plane).

As far as the audibility goes, here is a demo track for you to hear for yourself:

http://forums.klipsch.com/forums/622024/PostAttachment.aspx

Btw, within a certain window of time our ears no longer distinguish between individual seperately occuring sounds, but rather interpret the "average sound" over that period of time. The end audible result is a smearing or harshness associated with the "two" sounds being merged into one. So even though the delay isn't sufficient to warrant being heard as two distinct and different sounds, our ears still percieve an overall difference between a time-aligned and a time-delayed signal.

I believe Heiser is the one leading research in this area and you can find his writings "TIME DELAY SPECTROMETRY edited by John R. Prohs." here:

http://www.aes.org/publications/anth.cfm

(all the way at the bottom)

I think this is misleading, or at least confused. You are mixing the hearing of two pitches with the hearing of a single same sound repeated closely in time. If you have two identical sounds getting closer together in time there will come a point where you no longer hear them as two, but become one. This is because they are both the same sound (identical source). If the two sounds are different (different pitch, for example), this does not happen. Small time delays that time spread different frequencies (advance the violin to the cello) make no difference. This is because they are two different sounds (different sources).

Our ears do not percieve a difference between the time-aligned and time-delayed signal. You can't just map physics of sound waves to how the ear/brain listens and hears music. There is much more going on here. If different sounds interacted in your ear/brain as you describe, aligning drivers would be the least of our worries - you would not be able to distinguish the different sources of sound (you would not hear them as separate independant instruments - it would all be a mishmash of noise from a complex wave from which we could never extract any information. It would be like watching static on TV.

On the other hand, in cross-overs a steep filter engenders large timing errors which DELAY THE HIGHER FREQUENCIES. The stock networks in mine (AL-4) are sixth order (very steep at 36dB/octave), so maybe my LaScalas are already time-aligned out of the box?

[TBrennan]

It's certain that time delay can be heard as is evidenced by the original finding of the problem at MGM in the early 1930s "double tap" incident and Hilliard's subsequent examination of the problem.

However PWK rightfully was of the mind that speakers can have worse problems than time delay, it's not like any are perfect. PWK thought that the virtues of his folded horn outweighed the time delay problem. To have the benefits of the horn he had to live with some downsides. No big deal, pick your compromises.

[DrWho]

I think this is

misleading, or at least confused. You are mixing the hearing of

two pitches with the hearing of a single same sound repeated closely in

time. If you have two identical sounds getting closer together in time

there will come a point where you no longer hear them as two, but

become one. This is because they are both the same sound (identical

source). If the two sounds are different (different pitch, for

example), this does not happen. Small time delays that time spread

different frequencies (advance the violin to the cello) make no

difference. This is because they are two different sounds (different

sources).

Our ears do not percieve a difference between the

time-aligned and time-delayed signal. You can't just map physics of

sound waves to how the ear/brain listens and hears music. There is much

more going on here. If different sounds interacted in your ear/brain as

you describe, aligning drivers would be the least of our worries - you

would not be able to distinguish the different sources of sound (you

would not hear them as separate independant instruments - it would all

be a mishmash of noise from a complex wave from which we could never

extract any information. It would be like watching static on TV.

On the other hand, in cross-overs a steep filter engenders large timing errors which DELAY THE HIGHER FREQUENCIES.

The stock networks in mine (AL-4) are sixth order (very steep at

36dB/octave), so maybe my LaScalas are already time-aligned out of the

box?

Yes, there is a minimum time frame over which our ears combine

everything and interpret it as a single sound...but this doesn't mean

delaying part of the specturm is going to sound the same. The physical

wave forms are drastically different in regards to amplitude and

frequencies present, over any specificied segment of time. We don't

need to argue it because there is a

perfectly good sound sample provided here that demonstrates the

audibility

with a 2000Hz crossover and 9ms of delay on the low end. You don't even

need a good system to hear the difference. It was like night and day at

Colter's place on a pair of crappy labtec computer speakers! Have you even bothered to listen to the demo?

Btw, the steep crossovers are minimizing comb-filtering, which isn't

the same thing as the problems introduced by time delay...even though

both problems deal with the physical location of the drivers. Even with

no crossover overlap you will still problems due to time-delay. But if

you're talking about group delay in the crossover that is another

issue....but certainly won't be on the order of ms. I believe the

number given in class was on the order of microseconds...(come on,

we're talking about electrons flowing through wire here)

There are quite a few more manufacturers concerned with time-delay as

well. Just to throw in a favorite, Tannoy has been doing a lot of work

with coax designs (in fact, every speaker they build is coaxial) and

they are probably one of the few companies that I can confidently say

they sound better than klipsch....but then again, they cost a whole

heck of a lot more too []

[pauln]

Dr Who, you are not getting the distinction - not "everything" is combined in your ears to a single sound - only true if the "different" very short duration sounds are the same sound spread through a short enough period. Different sounds of different pitch do not combine like that.

I wrote that you can't map the physics to the ear. This means that while it is true that the physical measured waveform is different in its total complex shape when you vary the contibuting phase of the different pitches, the ear does not distinguish these phase differences. It hears the different pitchs independently.

The "perfectly good " sound sample was probably derived using digital and I don't think that is the best way to demonstrate anything that bears on musical sound. That's my bias. I did listen, thought a more natural selection of instruments might have served better, and heard no difference on my built-in speakers of my laptop (1/4 inch woofers!), so maybe I didn't hear much in the bass, yet I do hold the forum high score -42dB on the bass distortion test using these same laptop speakers.

http://forums.klipsch.com/forums/624148/ShowPost.aspx

Ultimately, I just don't hear a problem with "mis-aligned" drivers. In live music the sources are all over the place. A large orchestra may have a front to back range of many yards. The violins and basses may be separated by 10 yards. The ear hears music, not a complex phase mis-aligned waveform. If slight delays were a poblem, think about what might happen when you hear a single note sustained through time. Do the parts of the wave that are a few ms apart from each other cause a problem in hearing the sound? That is, for a particular instant in time corresponding to your hearing of the sound, is that sound goofed up because there is sound already before and after that instant within the few ms bracket that causes the sound of the instant to be fouled? I know this is hard to explain, but think about what must happen if sound delays are allowed to behave as you posit. You would not have a sense of hearing anything like how we experience music.

[DrWho]

Different sounds of different pitch do not combine like that...

the ear does not distinguish these phase differences. It hears the different pitchs independently.

But the phase relationships between the various frequencies

cause amplitude shifts that the ear will detect. Also, the attack of

the note will be drug out slightly into 3 secions: First, you have just

the HF parts for 7ms, then you have the HF and LF combined, and then

finally just the LF note by itself for 7ms. Yes, it happens over a

short period of time (within the Haas window) so no "echo" will be

percieved, but for 2/3 of the states there is only "half" of the

spectrum playing at a time - and this changes the timbre. For a single

note that drags out for a longer period of time it of course becomes

less noticeable, but the complex harmonic structure of music is

changing far faster - which means you are getting a lot of bleed over,

which means a totally different set of combination tones - so all sorts

of new frequencies and amplitudes are being produced.

The analogy to a live orchestra is flawed because it's not the

time-arrival of all the instruments that we're worried about, but

rather the time-arrival of the frequency spectrum. For instance, a

cello playing a 50Hz fundamental has a 10kHz harmonic. Regardless if

this cello is in the front row or the back row, the frequency spectrum

(combination of all the harmonics) arrives at the same time. If we

could somehow delay the upper harmonics (higher frequencies), we would

drastically change the timbre of the instrument.

Btw, those were cellos in the recording (combined with other instruments of course).

I also feel your bias against the digital manipulation has no grounds

whatsoever, but I would be more than willing to perform the same

process on any piece of material considered "suitable."

[pauln]

I appeciate your bearing with me. So now we have a single instrument like the cello whose note comprises a spectrum of harmonics, and when reproduced with staggered drivers the high end of the spectrum reaches me before the lower part, and the fundamental comes last. I think I see this - but is the timbre change perceived? And you are right about the orchestra - I was posing the high and low frequencies as coming from different instruments, but your example of a single instrument is correct, and I see how in reproduction with mis-aligned drivers the highs would precede the lows for not just a single instrument but for the whole source signal.

I'm still not convinced that this is audible. Is it possible that the Haas effect covers this as well, or something like the Haas effect that pertains to the relayed distribution of highs before lows such that the percieved sound is heard whole and fine? The reason I wonder is because we don't really hear in real time. The time frame of the brain is different from the real time outside where the music is physically happening. I have written elsehwhere about this. As a musician, I can play my guitar with a drummer in a way wherein both of us are playing 12 tones per second in perfect synchrony. This should be quite impossible, but it happens on hundreds of stages every night. I have examined this closely and have realized that the passage of time in the sense of music within the mind is not squared at all with the external clock time of reality. All musicians know this to some degree. It's hard to explain, but the way that we hear is only loosely related to the physics of sound, yet the ability to coordinate and present a unified and coherent performance to the audiance is clear and profound. I guess what I mean is that the reproduced delay of lows to highs may be a measurable fact, but I don't think the heard timbre change necessarily follows. You might naturally infer that it does, but again, physics of sound does not map directly to the way we hear. I think that something like the Haas effect may be in play. Or maybe with the high end rolloff of tubes, or the highend rolloff with aged ears the mis-alignment of early highs to later lows becomes less of an issue... or maybe I just like tubby bass?

I guess the important thing is to keep inquiring.

[seti]

Wow thanks for the replies abit over my head[*-)] I guess it was not an easy question.

[DrWho]

Wow thanks for the replies abit over my head[*-)] I guess it was not an easy question.

lol, go read Heiser's writings - I haven't read them yet, but the

people that have claim it is extremely easy to understand, even for

someone totally unfamiliar with the subject.

I think one reason the Jubilee sounded so good was because it is a

simpler design than the khorn and there are certain beneficial

attributes to having a 2 way design versus a 3 way. The Jubilee bass

section also handles the mids much better than the khorn bass section.

For the record, I don't think time delay is the sole reason for what I

percieve to be the tubbiness of the khorn (in the sense that the low

frequencies are arriving late). There are plenty of other factors which

seem to have been corrected for with the jubilee.

[6foot8]

Seti...go here http://www.prosoundweb.com/sr/tech/live/latency.php for a decent article on time delay.

Most research suggests that anything under 20ms is undetectable even when the subjects are aware of the delay. I have the pro cinema Jubilees in my media room and use a fully active crossover. I sit 28 feet away from the speakers and do not employ time delay correction at that distance.

[DrWho]

Seti...go here http://www.prosoundweb.com/sr/tech/live/latency.php for a decent article on time delay.

Most

research suggests that anything under 20ms is undetectable even when

the subjects are aware of the delay. I have the pro cinema

Jubilees in my media room and use a fully active

crossover. I sit 28 feet away from the speakers and do not

employ time delay correction at that distance.

woh there, that article is talking about the Haas effect and

comb-filtering due to delay of the entire spectrum. This is a

completely different subject and should not be confused with the

current topic.

Btw, have you tried time delay correction on your system? You can

hardly claim it is not needed if you haven't experienced the difference

[]

[6foot8]

Yes i have tried it and no it's not worth the effort. Too many other weak links of greater significance to worry about.

[6foot8]

btw didn't mean to butt in on your topic, only thought it may be pertinent or helpfull to someone else.

I'm outta here.