Do you time align your drivers ?

[1audiohack]

Real quick a couple of easy experiments to try with suprising results.

The issue at crossover with two drivers emitting the same frequency can be demonstated with the help of a friend, two small speakers like a pair of pro II's and a pink noise generator.

Drive the speakers at a comfortable level with pink noise, have your friend hold both speakers, one in each hand right next to each other with the sides touching and the front faces even with each other while you listen 10 feet or so away. Have him (or her) slide one speaker forward a few inches then back and observe the changes in what you hear, and let us know. Some say on the alignment issue, if your going to miss, miss big. You will see why.

The issue with the effects of the room, or some of them.

While listening in your usual spot, simply cup your hands behind your ears (giving your self Micky Mouse or Dumbo ears) and note the difference when your not hearing as much of the back of the room. When you do that out doors (like if you have a patio system) the sound does not change that much, in most "living rooms" the change is , well,,, try it. You might end up with a thick fiberglass pillow for you listening pleasure.

I have a pair of Altc 604 8-G's that I haven't listened to in some time and do have the desire to set them back up and get active with them. My real job and life just keep getting in the way.

Best,
Barry.

[ginetto61]

Real quick a couple of easy experiments to try with suprising results....
Best, Barry.

Really interesting Barry. Thank you very much.
Moreover I would be extremely interested to know anything about your time alignment procedure as well.
If now, as I understand, you are very busy please feel free in the future to mail me.
Thank you sincerely again.
Kind regards,
gino

P.S. when you talked about BAJE 1000 you mean BAJA 1000 ?? if not what's BAJE 1000 event ? I am quite curious

[robertbartsch]

Some of this "advanced" theory makes for interesting reading but little else.

About 30 years ago, I pulled some VOTT drivers from a non-time-aligned cab and built time-aligned cabs and installed the Altec divers. At the time, this theory was being advocated in Stereo and High Fidelity magazines as a very important development and space age theory and concluded it is absolute necessary for pure fidelity enjoyment.

Anyway, for me, the results were unimpressive and I would assume any blind tests using similar drivers in similar rooms, etc would result in no significant differences for listeners. After a few months the drivers returned to the factory cabs.

I think this theory is similar to the wonders of magic speaker cables that costs hundreds of buxs but produce no measurable improvment.

[4313B]

I think this theory is similar to the wonders of magic speaker cables that costs hundreds of buxs but produce no measurable improvment.

Actually the improvements are measurable. The breakdown occurs when people are asked whether or not they care. Yeah, they can hear a difference... So what!? Then they go back to listening contentedly to their iPods...

[Mr. Widget]

Actually the improvements are measurable. The breakdown occurs when people are asked whether or not they care. Yeah, they can hear a difference... So what!? Then they go back to listening contentedly to their iPods...

The measured differences are readily seen... huge in fact. Not like some BS cable theory or bringing RF design parameters into an audio discussion.

...and the changes are readily heard, if you set up an A/B comparison.

All that said, most speaker system designs do not lend themselves to a true time aligned design and most of us, even those of us who do not use MP3 files as a source can still be happy with them.


Widget

[ginetto61]

Please excuse me if I insist in on a topic so debatable
But I swear this is the last question I have
If I understand correctly a time aligned speaker usually defines a speaker which have the centers of emission of its drivers on the same vertical plane
Am I correct ?
Thank you very much to everyone
Kind regards,
gino

[Mr. Widget]

If I understand correctly a time aligned speaker usually defines a speaker which have the centers of emission of its drivers on the same vertical plane

That would be some people's definition.

I am not so sure that design will truly yield a perfect impulse or step response. If this response isn't perfect, then the design isn't truly time aligned.


Widget

[jcrobso]

Time or phase alignment sounds very good if you can do it correctly, but alas it is not easy to do. Aligning the voice coils may not be the only problem, don't forget about phase delays caused by the crossover. There are many things to consider, without the necessary test gear you will just be using the SWAG* method.


*Scientific Wild Ass Guess.

[ginetto61]

That would be some people's definition.
I am not so sure that design will truly yield a perfect impulse or step response.
If this response isn't perfect, then the design isn't truly time aligned.
Widget

Thank you very much Mr Widget
Very clear now. The impulse response is the tool.
Kind regards,
gino

[robertbartsch]

I beleive time aligned systems refer to having all the drivers placed so the voice coils of each are all on the same plane (e.g. verticle).

For systems imploying compression drivers and horns, this is no small task since the VC is usually deep away from the baffle/woofer VC.

Yeh, crossovers also cause time delay but trying to cancel this is beyond most hobists.

[1audiohack]

Originally Posted by ginetto61
I swear this is the last question I have

I hope not! That would end all our fun.

I can't type in a hurry, yes I meant Baja 1000.

The Klipsch review is, in typical Richard Heyser style, very informative, Nyquist plots are so cool. Thanks Grumpy, I didn't have that one.

As easy as it is to do, I'll bet no one does the two small speaker experiment. It is hard to believe how much a couple of inches, or micro seconds of time changes the sound when two drivers are radiating the same sound in close proximity to each other. It colors what you hear to a degree that will surprise you. Try it,,, I double dog dare you!

Have a good weekend all,
Barry.

[4343]

I hope not! That would end all our fun.

I can't type in a hurry, yes I meant Baja 1000.
...

Have a good weekend all,
Barry.

Say Hi to my bud Vince at VMAR Racing if you see him. He used to run a Bug with the surfboard on top... Not sure if he's still racing, last time I saw him was a month or so back, we were both driving north past the Bay Bridge and happened to both take Ashby Ave exit and came to a stop side by side at the first stoplight... He was in some sort of Smart Car sized vehicle with his VMAR Racing decal on the back, I yelled out "Hey Man, where's the surfboard", then asked him if that's what he was taking to Baja?. Just got a huge grin back...

[Ian Mackenzie]

Perhaps the point to appreciate is that you can only time align in one point is space.

Therefore, if the listener were 2.5 meters from the loudspeaker the designer can only setup the time alignment of two or more drivers at that distance.

The reason is that if an arch or radius was drawn vertically at 2.5 metres with the horn on axis and the woofer centre placed at a distance of 46 cm below the horn centre the true plane of focus as far a s time alignment is concerned would be 4cm closure to the listener as viewed from the woofer. This is simple geometry.

What is means is that the system will not pass a perfect square way (phase response) at the crossover point unless the woofer and the horn at aligned at that point. At progressively higher frequencies the amplitude response at the crossover point is is more sensitive the time displacement factor "D" because the wavelengths are shorter.

So a 50% displacement error at 4000 hertz (in terms of distance) would only be a 12.5 % error at 1000 hertz (for the same distance)

The human ear is apparently most sensitive in the 1 - 4 hertz region while significant delay known as group delay is readily dectectable at low frequencies where the delay could be 10's of milliseconds behind the upper fequencies.

Provided the crossover slopes are reasonably steep (18 -24 db)the response variations caused by poor time alignment at not a major factor.

Unfortunately other factors come into play that cause the sound stage to collapase other than time alignment such as "how" the power response of the woofer and horn sum at the crossover point.

The paper on the 4430-4435 discusses that stuff in great detail.

There is no question the 4435 images better than the 4345 in the right environment but that does not mean the 4345 or the 4343 are not more fun the listen too!

[Robh3606]

Which reminds me... how is your Array project coming?

Hello 4313B

I am about where I thought I would be. I am doing some renovations got most of my Sheetrock up yesterday so I get to tape and Spackle todayNot my favorite part of the job. Target is still Thanksgiving.

Perhaps the point to appreciate is that you can only time align in one point is space.

Agreed but if you try some measurements you see the most change in the vertical. The horizontal seems to hang together so as long as you have the "window" height right I doubt normal distance changes are going to be that significant where you would have audible consequences as long as the driver spacing is reasonable. You are still going to get a tight step response package. It would also seem that you would want to avoid a 3K crossover point like the plague.

Rob

[Allanvh5150]

That would be some people's definition.

I am not so sure that design will truly yield a perfect impulse or step response. If this response isn't perfect, then the design isn't truly time aligned.


Widget

To be truely time aligned I guess the front baffle would have to be curved to focus the sound on one point.......

Allan.