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[Mark Wilkinson]

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.

Can't blame you for doubting....I'm surprised too.

The delay distance was greater than the actual distance, like it should be. 
If I may re-quote what I wrote in reply #12 ..."the delay finder readings tie exactly! with expectations...
.....expectations being processor/ amp delay, plus physical mic distance, plus physical horn length"

When you asked earlier if I had reset the delay finder for each test, it prompted me to look at the stored traces' 'info' boxes to see what the delays were.
When i saw how tightly they were grouped, I said damn...never seen that before measuring subs.
So I'm like, how close are they to what I think they should be?
I measured the delay of signal processing alone, then added in the delay for distance from mic to subs, and finally added in delay for the horn length.
Bingo...the same.

If I get a chance today, I've got a set of experiments in mind to see if the above is repeatable, and dissect a little further...will report..

Art, glad to hear you are surviving being a "welter".....funny, thx !

[Art Welter]

Art, glad to hear you are surviving being a "welter".....funny, thx !

Mark,
It all seems funny afterwords :^)...

I'm trying to learn more from the mistakes of others than my own, but it seldom seems to work that way ;^).

Back to the question you raised in the first post:
"I'd be interested if people think this testing methodology holds water...."
It seems OK, but the Lab Sub minimum impedance is almost the the same as it's DCR, a pair with parallel drivers is only 2.145 ohms, which is almost a 6 dB sensitivity gain at 2.7 volt compared to a "one watt" voltage.

When that is taken into account the sensitivity no longer looks freakishly high.
"Freakishly High", sounds like a good band name..

Art

[Ivan Beaver]

If I may re-quote what I wrote in reply #12 ..."the delay finder readings tie exactly! with expectations...

But having the same arrival time is RELATIVE, not absolute.

The actual arrival time is absolute, the difference in arrival times is relative.

They each have their own merit and place.  But ARE NOT the same and should not be confused with each other.

[Mark Wilkinson]

But having the same arrival time is RELATIVE, not absolute.

Hi Ivan, the second part of that quote in reply #12 that was chopped off addressed the absolute....the absolute was correct too.

Speaking of absolute timing...that's where i started out this fine morning. 
Measured the electrical processing delay for 2 filters: one IIR, the other FIR.  Both being the same 24BW@27hz HPF and 48LR@100 LPF.
(Needed this first timing component for figuring absolute timing expectations out on the driveway...)

Also took about 10 delay finder 'pings' for both the FIR and IIR filters ....to see the spread of results.
The spread was about the same, 0.42ms vs 0.46ms.....so already I knew my idea about linear phase filters making it easier for delay finder was baloney.
Back to Merlijn's video !

But I went ahead and hauled out on the driveway, and marked off the usual 8m testing distance (2nd component of absolute timing.)

Then I got transfers with FIR x-over, and IIR x-over.
The delay finder ping spread for both FIR and IIR tightened up a little, maybe some form of averaging going on combining electrical and acoustical?? No clue...

Timing measurements for FIR and IIR  were the same, after their processing delay difference found earlier was accounted for.

The only good news in alot of useless testing, is that using either IIR or FIR bandpassed signal to sub, I got believable distances.
Both gave about a 10.5ms horn length, when mic distances and signal processor delay were removed.

 

[Mark Wilkinson]

Back to the question you raised in the first post:
"I'd be interested if people think this testing methodology holds water...."
It seems OK, but the Lab Sub minimum impedance is almost the the same as it's DCR, a pair with parallel drivers is only 2.145 ohms, which is almost a 6 dB sensitivity gain at 2.7 volt compared to a "one watt" voltage.

When that is taken into account the sensitivity no longer looks freakishly high.
"Freakishly High", sounds like a good band name..

Hi Art, afterwards and I also are all too well acquainted ; )

You know, I was a bit surprised at the sensitivity the labs measured.... but I dunno if anything's wrong...

And it get's more puzzling when thinking about impedance.  I've measured the labs impedance very carefully, 1,2,3, and 4 at a time.
Even measured a bank of 4 two different ways, as a box individually and as all 4 in series/parallel to equal one box.....to see if there was any diff.
 
In a 4 bank, I'd call a single lab with drivers in parallel a 5.5 ohm nominal...not dipping below 3 ohms.  I feel pretty solid here..

So I know this makes the numbers I posted look even more freakish ....

Here's more puzzle, I've been doing boatloads of testing a DIY on top of my two orbit shifters all summer long. Know the balance between the DIY and OS (4 ohm) very well.
I put the DIY on 2 labs after testing the other day, using settings for the OS subs, and the 2 labs were clearly stronger.

So I dunno...
I'm going off into hypothesis world like I always do, and am left wondering if a 2.83v bandpassed rms measured pink signal that I use has more energy than whatever  "2.83v signal" is normally used???
(But one weakness in that theory is the OS sensitivity I measured tied right to published spec.)

?? 

[Ivan Beaver]

I'm going off into hypothesis world like I always do, and am left wondering if a 2.83v bandpassed rms measured pink signal that I use has more energy than whatever  "2.83v signal" is normally used???

Here is an interesting experiment.

Use pink noise and band limit it pretty tight and measure the voltage.

Now don't touch any gains, and widen the freq bandwidth (higher and/or lower).

Notice how the voltage rises-even though the drive level does not.

So a wider bandwidth signal has more overall energy than a narrow bandwidth signal.

[Art Welter]

1)In a 4 bank, I'd call a single lab with drivers in parallel a 5.5 ohm nominal...not dipping below 3 ohms.  I feel pretty solid here..
So I know this makes the numbers I posted look even more freakish ....

2)I'm going off into hypothesis world like I always do, and am left wondering if a 2.83v bandpassed rms measured pink signal that I use has more energy than whatever  "2.83v signal" is normally used???
(But one weakness in that theory is the OS sensitivity I measured tied right to published spec.)

Mark,

1) Silas Pradetto did impedance testing with his Labs, the impedance minima is near the DCR. Unfortunately, his reports were lost in the transition from the old "LAB" to "Pro Sound Web".
A "nominal" impedance is just that, something of an average, but for sensitivity tests the impedance minima should be used. Wayne Parnham's PI subs, basically a larger Lab, also read near the Lab 12 DCR, and Hornresp simulations on nearly every FLH and TH I have designed all have impedance minima near the DCR of whatever driver used.

2)Unless things have changed since I last looked, Jeff does not publish a measured response for the Orbit Shifter, making the sensitivity a bit questionable, though it does appear to be an average of the pass band he references.

I have never been able to get what I consider a reliable "RMS" voltage using pink noise (probably due to cheap meters..), so have always used sine waves at various frequencies, setting the voltage ( 1.41V for 2 ohm, 2V for 4 ohm, 2.83 for 8 ohm etc.), at 60 Hz, where the meter should be most accurate. I do my testing at 2 meters, and subtract 6 dB for the inverse distance rule.
I also like to test at the excursion minima,  which usually happens to be the impedance minima, the speaker draws the most power at the frequency where forced air cooling is the least. After the sine wave tests (which also can be used to measure distortion) I then match them to the pink noise tests, so an accurate reference 1W/1M SPL is known.

Art

[Mark Wilkinson]

Here is an interesting experiment.

Yes, it is interesting. 
I've tried it before and found it shows that each octave, or any equal slice of an octave (ie 1/3)  or octaves (ie 3) , gives the same voltage.
I guess it's part of the pink noise definition...
the devil of the details is in these definitions huh?

[Mark Wilkinson]

Mark,

1) Silas Pradetto did impedance testing with his Labs, the impedance minima is near the DCR. Unfortunately, his reports were lost in the transition from the old "LAB" to "Pro Sound Web".
A "nominal" impedance is just that, something of an average, but for sensitivity tests the impedance minima should be used. Wayne Parnham's PI subs, basically a larger Lab, also read near the Lab 12 DCR, and Hornresp simulations on nearly every FLH and TH I have designed all have impedance minima near the DCR of whatever driver used.

2)Unless things have changed since I last looked, Jeff does not publish a measured response for the Orbit Shifter, making the sensitivity a bit questionable, though it does appear to be an average of the pass band he references.

I have never been able to get what I consider a reliable "RMS" voltage using pink noise (probably due to cheap meters..), so have always used sine waves at various frequencies, setting the voltage ( 1.41V for 2 ohm, 2V for 4 ohm, 2.83 for 8 ohm etc.), at 60 Hz, where the meter should be most accurate. I do my testing at 2 meters, and subtract 6 dB for the inverse distance rule.
I also like to test at the excursion minima,  which usually happens to be the impedance minima, the speaker draws the most power at the frequency where forced air cooling is the least. After the sine wave tests (which also can be used to measure distortion) I then match them to the pink noise tests, so an accurate reference 1W/1M SPL is known.

Art

Art, I can't try to address the info you offer re Silas, Wayne, and Hornresp.  I can only say I've measured the Lab's impedance with DATS, Terrasonde's ATB, and old school rms voltage and current, sine by sine. Measurements always tie closely, and I have to believe they reflect reality....  a 4 bank minima is right around 3 ohms, nominal something above 5 ohms.  (If I have time, I'll try to send my sub passband-noise and measure rms current and voltage to come up with a "measured nominal" next time I have em all out. I'd really like to see this kind of meas as a manufacturer spec (along with full imp curve of course) , where they specify the passband, and use measured voltage and current instead of 'pick a number').
 
I took a quick 1 Lab dats below just now, because all my old data is on a retired PC.  You'll see the minima isn't that far from DCR.
It's really cool how the minima's raise and maxima's  lower as you add boxes...shows the great design work by mr. Danley imo.... I don't have the right cabling make an easy to show 4 box test right now...

Also took a dats of an OS. I figure you know this site, but in case not, data-bass makes the best sub measurements I've found http://www.data-bass.com/data?page=system&id=119&mset=131

And yeah, that damn pink voltage can sure bounce around, can't it?  Even when I use a minute or so averaging, still end up with average to average variations up to 0.20 v.
For sensitivity, I just normalize whatever average shows up to 2.83v, and also normalize whatever SPL LEQ that was measured over the same period..

Oh, a bit of a swerve if I may...how do you measure distortion?  I've been trying with REW. Results seem reasonable, but I'd like a way to find some confirmation...thx.

1 Lab then 1 OS

[Art Welter]

1)I took a quick 1 Lab dats below just now, because all my old data is on a retired PC.  You'll see the minima isn't that far from DCR.
2)Also took a dats of an OS. I figure you know this site, but in case not, data-bass makes the best sub measurements I've found http://www.data-bass.com/data?page=system&id=119&mset=131
3)And yeah, that damn pink voltage can sure bounce around, can't it?  Even when I use a minute or so averaging, still end up with average to average variations up to 0.20 v.
For sensitivity, I just normalize whatever average shows up to 2.83v, and also normalize whatever SPL LEQ that was measured over the same period..
4)Oh, a bit of a swerve if I may...how do you measure distortion?  I've been trying with REW. Results seem reasonable, but I'd like a way to find some confirmation...thx.

Mark,

1) Yes, that's why it is easiest to just assume the impedance minima will be the same as the DCR.
2) Josh does great work, Jeff should just use his measurements on his site, but he gets all huffy when distortion is brought up ;^).
3) With only a VOM to measure voltage, I have no way to average the huge peaks and troughs.
4) I downloaded REW about a half year ago, but have hardly used it. Still going with the "old school" method, run a sine wave, look at the difference between it and the harmonics using an RTA, look up the difference on my handy-dandy nomograph, and after repeating the process every 5 Hz or so, hours later it's done 

The example below has a 124.7 dB fundamental, the second harmonic is 99.9 dB a 24.8 dB difference, I'd round down to the whole number, so distortion is around 6%.

Art

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