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[Mark Wilkinson]

The problem is that there is no "sharp point" of the signal-so exactly where is the "arrival".

Yes, that lack of a "sharp point " has driven me crazy at times...

I'm thinking maybe a relatively steep 48dB low pass, and the use of linear phase x-overs, makes for a better grab handle for the delay finder....or perhaps better said, a 'grab plateau'.

I'm mean, if electrical x-over group delay variations have been nearly eliminated, shouldn't any freq the delay finder hooks onto within the passband read close to the same delay ?

I realize group delay variation's from the raw sub itself have to be taken into account too, and those variations if signifigant will screw the plateau idea up....
 ....but fortunately in the case of the labhorns and OS's, the raw sub phase looks nicely flat, so group delay variations are minimal here too.....
..... maybe all this together accounts for the delay finders' tight spread of measurements? ? And in this case maybe it doesn't matter too much, what freq it hooks on to ? ?

Just thinking out loud...make any sense?

[Ivan Beaver]

Yes, that lack of a "sharp point " has driven me crazy at times...

I'm thinking maybe a relatively steep 48dB low pass, and the use of linear phase x-overs, makes for a better grab handle for the delay finder....or perhaps better said, a 'grab plateau'.

I'm mean, if electrical x-over group delay variations have been nearly eliminated, shouldn't any freq the delay finder hooks onto within the passband read close to the same delay ?

I realize group delay variation's from the raw sub itself have to be taken into account too, and those variations if signifigant will screw the plateau idea up....
 ....but fortunately in the case of the labhorns and OS's, the raw sub phase looks nicely flat, so group delay variations are minimal here too.....
..... maybe all this together accounts for the delay finders' tight spread of measurements? ? And in this case maybe it doesn't matter too much, what freq it hooks on to ? ?

Just thinking out loud...make any sense?

Think of it like this.

Let's draw a line on the road.  And the "simple question" is "When does X cross the line".

A motorcycle is pretty easy to tell when it crosses.

But what about a tractor trailer?  Is "crossing" the front? the rear? the middle?  Exactly where is the "middle".  The whole vehicle? or just the trailer?

So with a low freq wave-what is the "arrival?  When it starts to get to the mic?  Or the largest point?

Does the delay finder lock onto the harmonic distortion? because it has a "sharper" impulse, or the larger "round" mound of the lower freq?

One easy way to get really confused-do this test.

Use a sub-cross it over in a "normal"  freq (let's say 100hz or lower).

Now use the delay finder in whatever program you are using.

Does the number it gives make any sense?  If you were to measure the physical distance from the mic to the cabinet-add the physical delay inside the cabinet and add any digital delay.

In most cases you will find that the presented time/distance is much longer than the actual distance.

The reason is that the program has a specific "point" that it is looking for.  Where that "point" is, varies.

As usual-there is not a "simple" answer.

And with many other things-the deeper you dig- the more you realize how far there is yet to dig.

[Mark Wilkinson]

One easy way to get really confused-do this test.

Use a sub-cross it over in a "normal"  freq (let's say 100hz or lower).

Now use the delay finder in whatever program you are using.

Does the number it gives make any sense?  If you were to measure the physical distance from the mic to the cabinet-add the physical delay inside the cabinet and add any digital delay.

In most cases you will find that the presented time/distance is much longer than the actual distance.

The reason is that the program has a specific "point" that it is looking for.  Where that "point" is, varies.

AFAICT, that is the exact test I did....maybe I'm missing something.....pls check out the testing methodology in orig post..thx.

If I'm not missing anything, here's what's so cool....the delay finder readings tie exactly! with expectations...
.....expectations being processor/ amp delay, plus physical mic distance, plus physical horn length.

And better yet, delay finder numbers repeat tightly .... none of the usual bouncing around.

Like I was saying in the last post, I'm really thinking the use of linear phase x-overs for sub testing (along with the inherent flat-ish phase of the horn subs) let's this be so.

I like your train analogy, but it doesn't seem like it's so much of a matter of when each the train cars cross the line in serial order. Aren't the cars (frequencies) all on parallel tracks heading toward the line? It seems like it's a matter of when a reference point on each of the cars' crosses the line, the reference point being phase angle. What I'm thinking is due to all the flat phase, all the cars' reference points are crossing the line at about the same time....choose almost any car I think, results won't vary much  !! 
Wish I could force smaart's delay finder to lock onto selected freqs....would be great to thoroughlycheck this out.

[Mac Kerr]

Wish I could force smaart's delay finder to lock onto selected freqs....would be great to thoroughlycheck this out.

What's so hard? Use a tone instead of pink noise. Smaart doesn't care what it's listening to when it is finding the delay, you only need full bandwidth for full bandwidth measurements. If you don't get repeatable results with the tone add some pink noise or music under it.

Mac

[David Sturzenbecher]

What's so hard? Use a tone instead of pink noise. Smaart doesn't care what it's listening to when it is finding the delay, you only need full bandwidth for full bandwidth measurements. If you don't get repeatable results with the tone add some pink noise or music under it.

Mac

Why are we still talking about the delay finder not working at sub freqs.   Everyone has watched this video right?
https://www.merlijnvanveen.nl/en/study-hall/120-why-the-impulse-response-won-t-work-for-subwoofers

[Mark Wilkinson]

@ Mac,  great, thx.....I've tried that before with just sine and couldn't get a lock....didn't think of adding some pink...


@ David,   Yes, excellent helpful video.

But I'm not talking about how the delay finder doesn't work for sub frequencies......

I'm reporting an experience/methodology where it does work, and apparently very accurately.

[Ivan Beaver]

But I'm not talking about how the delay finder doesn't work for sub frequencies......

I'm reporting an experience/methodology where it does work, and apparently very accurately.

Yes the times may be very close-that is just an indicator that the path lengths are close.

But does the numbers the delay finder gave you make sense in relation to the actual distance from the sub?

THAT-is the whole point of my post. 

As with any measurement system, just because you get a number-DOES NOT always mean that it is "correct".

As with many things audio, the question may have several "correct" answers.

It depends on SPECIFICALLY what "question" was asked of the measurement system.

[Mark Wilkinson]

But does the numbers the delay finder gave you make sense in relation to the actual distance from the sub?

THAT-is the whole point of my post. 

Hi Ivan,
 
YES, like I said,  the numbers in the delay finder accurately reflect the actual distance from the sub...

[Ivan Beaver]

Hi Ivan,
 
YES, like I said,  the numbers in the delay finder accurately reflect the actual distance from the sub...

I guess I sound like a "doubting thomas", but the delay distance "should" be greater than the actual distance, in order to account for the physical path length of the horn.

In every case that I can remember, the delay time was much, much longer than the actual distance between the mic and the cabinet.

[Art Welter]

I guess I sound like a "doubting thomas", but the delay distance "should" be greater than the actual distance, in order to account for the physical path length of the horn.

In every case that I can remember, the delay time was much, much longer than the actual distance between the mic and the cabinet.

The delay time will also include the delay present from a HP filter if it is engaged, though that is dependent on the crossover/DSP topology integration, some platforms don't change with the HP filter in or out, Bennett Prescott's reporting of the "Digital Tower of Babel" has still not been addressed by the various DSP makers.

If hurricane Matthew had not occupied about three (24 hour) days time, I'd already have measured the delay of a "new" pair of subs (using 20 year old Hartke woofers) that were half way finished before it appeared on the weather report's local radar.

Cheers,

Art (survivor of two hurricanes, multiple car, and four airplane crashes) Welter

My last name seems to define my life, according to Webster's dictionary...

[ProSoundWeb Community]