Concept of time delay?

[steamer]

I currently use a simple Rane 2way without a time delay function.I have been kicking around the idea of upgrading to an active with it.

I am trying to understand how to implement delay in my system.I have my speakers stacked at this time.From the bottom up it is the Bagend sub,Scala bass bin then on top the 511B/902.The concept of driver alingment in the vertical plane makes sense.What has me confused is the speed of various freqencies.Am I right thinking that a 10000hz sound would reach the listening position faster than say a 20hz sound?I have read that delay is implemented on the high freqency driver to bring the drivers back into or compensate for misalignment of the drivers.In my mind I am thinking that the high frequency driver is not phisically aligned to begin with and because of the higher frequencies reproduced it should seem closer in alignment than the phisical orientation would suggest.I remember reading somewhere about moving the tweeter back to the rear of a K-horn to improve the response as compared to the mid driver in the time domain.

I hope I have worded this correct.

Greg

[D-MAN]

Negative - the SPEED of sound (regardless of frequency) is a "fixed" constant. Figure about 1130 feet per second (70 deg. F at sea level).

The difference between what the tweeter puts out and what the subwoofer puts out is a matter of diaphragm position, angle of dispersion and distance from the listening position, where ever that may be, resulting in differences in TIME as the sounds arrive at the listening position delayed by the distances or paths taken to get there.

DM

[steamer]

Thanks,

I figured the speed of sound was constant,your explanation makes sense concerning arrival time perception.So many variables in this hobby.

Greg

[Guest " "]

steamer, I sent you a PM

[Guest " "]

There is some very good material about time alignment in the below paper

http://www.alkeng.com/dload/esxover.pdf

While not quite the same as time delay, there is some overlap in the understanding of one and the understanding of the other, in my view anyway.

[colterphoto1]

But remember the higher frequencies, being 'lighter' than the bass waves, tend to drift upwards toward the ceiling, whilst the heavier bass notes tend to roll across the floor. Do not leave this vital information out of your calculations.

just kidding, but a lot of newbie audiophiles will actually bite at this one!

[djk]

"But remember the higher frequencies, being 'lighter' than the bass waves, tend to drift upwards toward the ceiling, whilst the heavier bass notes tend to roll across the floor. Do not leave this vital information out of your calculations. "

Actually, when you are outside it does make a difference. Temperature and humidity changes affect how you have to angle the HF horns.

[DrWho]

Something even more trippy is that the rarefactions travel faster than the compression wave...so if you're far enough away you stop hearing sound altogether until you move a little bit further and now you're hearing the rarefaction before the compression (or is it the other way around? I forget)

A very loose rule of thumb for time delay is to measure the distance from your listening position to each driver. If you have a folded bass bin then you need to include the path length of the entire horn. For every foot that the HF driver is closer than the LF driver you need to add 1ms of delay to the HF driver.

[steamer]

But remember the higher frequencies, being 'lighter' than the bass waves, tend to drift upwards toward the ceiling, whilst the heavier bass notes tend to roll across the floor. Do not leave this vital information out of your calculations.

just kidding, but a lot of newbie audiophiles will actually bite at this one!

LOL!!!!

No I didnt fall for it but paused...not for long.

Greg

[chops]

Now would any of this apply to my current setup?

Since I'm running the Cornwalls as bass bins, the K33 driver is right on the front baffle (motorboard). However, with the 511B horn, the 902 driver is over a foot back behind the motorboard, so wouldn't that already naturally correct a little bit for the time alignment?

[steamer]

Something even more trippy is that the rarefactions travel faster than the compression wave...so if you're far enough away you stop hearing sound altogether until you move a little bit further and now you're hearing the rarefaction before the compression (or is it the other way around? I forget)

A very loose rule of thumb for time delay is to measure the distance from your listening position to each driver. If you have a folded bass bin then you need to include the path length of the entire horn. For every foot that the HF driver is closer than the LF driver you need to add 1ms of delay to the HF driver.

Mike,

Maybe I have this wrong but you suggest adding delay for every foot CLOSER.Do you mean further away the HF driver is from the LF driver?

Greg

[steamer]

Something even more trippy is that the rarefactions travel faster than the compression wave...so if you're far enough away you stop hearing sound altogether until you move a little bit further and now you're hearing the rarefaction before the compression (or is it the other way around? I forget)

A very loose rule of thumb for time delay is to measure the distance from your listening position to each driver. If you have a folded bass bin then you need to include the path length of the entire horn. For every foot that the HF driver is closer than the LF driver you need to add 1ms of delay to the HF driver.

BTW,what is the distance for the sound wave in the Scala bass bin?

Greg

[steamer]

Now would any of this apply to my current setup?

Since I'm running the Cornwalls as bass bins, the K33 driver is right on the front baffle (motorboard). However, with the 511B horn, the 902 driver is over a foot back behind the motorboard, so wouldn't that already naturally correct a little bit for the time alignment?

Charles,

That was my impression before I posted this thread,but it is not so.

Greg

[DrWho]

The lascala bass bin is about a 4 foot path from the driver to the exit of the horn? So from the isntant the driver starts playing, there will be 4ms before sound makes it out the front. I believe the altec HF section is about 18 inches long? So it takes 1.5ms for the sound to get to the front. You will want to delay the HF section by 2.5ms so that the wavefronts lineup at the motorboard.

The drivers with the shorter propogation distance are the ones getting the delay.

[djk]

The LaScala woofer air path is about 36" to the dustcap. A digital delay is required for the mid and HF drivers.

The Cornwall woofer delay may be compensated for with an all-pass delay network, but the tweeter needs a digital delay. If you use a wide-band HF driver (Altec, JBL, etc) and don't need a tweeter, then a passive all-pass may be incorporated in the woofer circuit of the crossover.

Greg: If you are willing to invest $8 for a memory battery, I can loan you a digital crossover I am not using.

[steamer]

The LaScala woofer air path is about 36" to the dustcap. A digital delay is required for the mid and HF drivers.

The Cornwall woofer delay may be compensated for with an all-pass delay network, but the tweeter needs a digital delay. If you use a wide-band HF driver (Altec, JBL, etc) and don't need a tweeter, then a passive all-pass may be incorporated in the woofer circuit of the crossover.

Greg: If you are willing to invest $8 for a memory battery, I can loan you a digital crossover I am not using.

djk,

I would enjoy that very much.I have sent PM.Back to the question at hand I came up with about 1.5 ms.for a dealy setting to the HF driver.36" minus 18"=18" or 1.5'.

Thanks,Greg

[steamer]

The lascala bass bin is about a 4 foot path from the driver to the exit of the horn? So from the isntant the driver starts playing, there will be 4ms before sound makes it out the front. I believe the altec HF section is about 18 inches long? So it takes 1.5ms for the sound to get to the front. You will want to delay the HF section by 2.5ms so that the wavefronts lineup at the motorboard.

The drivers with the shorter propogation distance are the ones getting the delay.

Mike,

That makes more sense.I didnt take into account the path length of the horn bass bin but only the physical alingnment of the drivers.

Thanks,

Greg

[colterphoto1]

Here's an extra credit problem Doc-

How many ms is it before the human ear perceives the sounds as coming from different sources or that it interferes with phasing or musicality?

And if the speaker designer included this time difference in their original voicing, will using an outboard delay possibly cause other problems in the soundwave?

Damn man, the more I read your posts the smarter you get! Roy is going to have to hire you to keep you from competing in a few years.

Michael

[sunnysal]

I think bell labs (the old bell labs famed in song and story) did some tests where they posited about 3-5ms as the threshold, they moved drivers back and forth on rails...however I found some old posts by john curl on the subject and thought they might be interesting as well...

""Differences in phase produce no effect on the ear. This is known as Ohm's law, having been discovered by G.S. Ohm (1787-1854), the discoverer of the still better known electrical law." How about that, folks?
Anyone who has owned a K-horn knows this isn't completely so.
Back in the late '60's, Richard Heyser mentioned at an AES convention that perhaps a 2 ft or less time difference between speaker drivers (all kinds of phase shift) might be audible in some instances. Interestingly enough, both Richard Heyser and I both owned K-horns and we were good friends with Paul Klipsch. Klipsch got up and said 'bullshit'. I was there, I know.
About 8 years later, a paper on human hearing was put into 'The Preceedings of the IEEE', by M. Schroeder, which opened up a whole world of understanding phase sensitivity in the human ear. Richard Heyser said to me that: "Now everyone will understand", but I retorted: "But, Richard, who reads 'The Proceedings of the IEEE', except you and me?" At the same time, another audio consultant, Ed Long, the inventor of the term "time align" started working on absolute polarity. He found that some music and speech was very polarized, and easily heard. Other stuff was so multimiked, both in and out of polarity, that resolution was difficult, if possible at all. Over the following years, Clark Johnsen wrote a book on it, and most of my friends are very serious about its effects."

"Forty years ago, when I first got serious with high fidelity, we were told that the ear was 'phase deaf'. In 1965, I first met Paul Klipsch, and over lunch he would tell us about <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Bell labs research etc, that the ear could not hear several feet of time difference between speaker drivers. We were true believers and many serious audioiphiles got a K-horn or two. After a few years listening to these speakers, I realized that I couldn't image stereo with the speakers very well. Smaller sources seemed to do it better. Still later, when working with the Grateful Dead and becoming familiar with the Jerry Gracia's voice, I realized that the K-horn would NOT reproduce Jerry's voice accurately, in fact it sounded like someone else. This got me to sell my K-horns over 20 years ago, and get speakers more 'time aligned' . Today, this is obvious, and speaker designers worry about small time delays, but it wasn't considered relevant 35 years ago, and any speaker designer who serious worried about it would be considered a nut. This is how we make progresss.

In the modern realm, dick heyser wrote a lot on this subject and concluded it is an important factor in good sound.

regards, tony

[colterphoto1]

Thanks for the information, but I'm puzzled as to one bit.

You mean to say that some people thought Jerry Garcia had a 'voice'?