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Author Topic: TEF 25 PROBLEMS!!! and TEF Subwoofer meaurements.  (Read 5351 times)

Antone Atmarama Bajor

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TEF 25 PROBLEMS!!! and TEF Subwoofer meaurements.
« on: July 29, 2005, 01:59:50 am »

    I noticed that Mark S. said he has a TEF 25.

I was wondering if anyone has been having as much trouble with the Goldline Sound Lab 6.7.X as I have.  Especialy with the TEF 25.

    I get tons of eroneous Data from the TEF 25, and in the internal loop back in the TEF 25 There is a 6 degree phase shift just measuring itself.

   I also have lots of trouble with the SL software crashing with our TEF 20, Half of the features in polar don't seem to work correctly.  It defaults to rediculus sweep setings for impedance and frequency TDS tests.  

    We are assembling a laundry list of Sound Lab and TEF 25 problems, and are planing on sending it to Goldline and telling them if they can't fix the problems and make it work.  We have to return it.  Its to critical a piece of equipment to be as unreliable as it is currently.  We collect better data with the DOS version of the TEF software.

    On a lighter note.  What are the best ways of testing LF response of a subwoofer with the TEF.  We don't have the luxury of a wide open parking lot with no vertical reflective surfaces nearby.  And to do good high res LF sweeps you need to open up the filter ear by almost a 100ft.  If I wan't not so High res sweeps say 30Hz Acuracy Then we may be able to do it.  But that really limits the LF Resolution.

    Anyhow any tips?

Sum-    
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Tom Danley

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Re: TEF 25 PROBLEMS!!! and TEF Subwoofer meaurements.
« Reply #1 on: July 29, 2005, 11:58:45 am »

Hi

While I can’t speak to the new unit (TEF25), I have a 20 and have had a 12, 12 plus and the original TEF 10.   If you have already downloaded the latest core updates and such and that didn’t fix it, try running it from a different computer.  The only problems I have had were “something” to do with the computer communicating with the TEF.
I guess “IBM compatible” still covers a good deal of ground internally.

When you say “6 degrees of phase error in loop back”, do you mean it shows up at 20KHz? (possibly suggesting a very short time error).
So far as measuring subwoofers, I can make some suggestions so far as using the TEF 20.

You mention you have about 100 feet of open space outdoors, cool.

For A vs B comparisons it doesn’t matter so much but if you want to get real 1 Watt 1 Meter ground plane sensitivity, it is more involved.
You will want to be further than one meter from anything with the size of a subwoofer, in theory, the source is emanating from a hole on the ground (burring an array of subs in a parking lot would be a pain).  You want to be far enough away so that the size of the boxes does not introduce too much error.

A distance of 10 meters is –20 dB from 1 meter so far as inverse square law and driving the system with 10 times the “1 Watt” voltage (+ 20 dB over 1 Watt) results in a 1 Watt 1 Meter equivalent.
This is a large enough distance so that the “error” from not doing it properly is insignificant.  
While 10 meters makes the math easy, the down side is that all VC drivers begin to show the effects of heating when driven above about 1/6 to 1/10 rated power, depending on the system, 100Watts may be into that region.

Any other distance can be used too but the closer you are to the source, the greater the error is and the further away you are, the larger the reflected sound level.
The latter would not be a concern if you were in a big flat empty field.

Use your “speaker” icon to produce and set the test voltage at 60 HZ, most DVM’s are calibrated at 60 HZ.
Lets say you had a sub with a 40 HZ low cutoff.

In “parameters” set the upper and lower frequency limits (say 20 HZ to 200Hz) and select some small value for sweep time, like 3 seconds or so.
Click “best resolution”
Typically, depending how much detail you want to see, enter a resolution frequency value that is about 1/10 to 1/6 of the corner frequency.
For seeing “everything”. Set the resolution to about 1/10 the low frequency sweep limit.
Remember to keep the upper frequency limit to some reasonable limit, the higher it is, the longer the measurement will take.

Because of the TEF’s increasing resolution with increasing frequency, set the smoothing.
Your ear has about a 1/6 octave critical bandwidth so a smoothing factor of about 16% octave corresponds to what your ears could resolve under the right conditions so use more or less depending.

Also, being a ground plane measurement, you want to place the mic on the ground or really on some scrap of plywood etc.

Hope this helps, have fun.

Tom Danley

Danley Sound Labs












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Mark Seaton

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Re: TEF 25 PROBLEMS!!! and TEF Subwoofer meaurements.
« Reply #2 on: July 29, 2005, 12:11:04 pm »

sumsound wrote on Fri, 29 July 2005 00:59

    I noticed that Mark S. said he has a TEF 25.

I was wondering if anyone has been having as much trouble with the Goldline Sound Lab 6.7.X as I have.  Especialy with the TEF 25.

    I get tons of eroneous Data from the TEF 25, and in the internal loop back in the TEF 25 There is a 6 degree phase shift just measuring itself.

   I also have lots of trouble with the SL software crashing with our TEF 20, Half of the features in polar don't seem to work correctly.  It defaults to rediculus sweep setings for impedance and frequency TDS tests.  

    We are assembling a laundry list of Sound Lab and TEF 25 problems, and are planing on sending it to Goldline and telling them if they can't fix the problems and make it work.  We have to return it.  Its to critical a piece of equipment to be as unreliable as it is currently.  We collect better data with the DOS version of the TEF software.

    On a lighter note.  What are the best ways of testing LF response of a subwoofer with the TEF.  We don't have the luxury of a wide open parking lot with no vertical reflective surfaces nearby.  And to do good high res LF sweeps you need to open up the filter ear by almost a 100ft.  If I wan't not so High res sweeps say 30Hz Acuracy Then we may be able to do it.  But that really limits the LF Resolution.

    Anyhow any tips?

Sum-    



Hi Sum,

I don't think there are all that many TEF users on the LABsub forum.  The TEF20 has no problems with accuracy, only in that it will measure exactly what you tell it to.  As with any measurement system, it is very possible to gather data that really tells you nothing.  With the unique parameters able to be adjusted in a TDS measurement there are a few more ways to get erroneous data than with other platforms.

Gold-Line has had some trouble with some quirks in the Windoze software.  The majority of the problems with the TEF20 have been related to the differences in computer setups.  Talk to Lou' at Gold-Line about the problems, as those are probably fixable.  The TEF25 had a rocky start with the software but now seems to be behaving relatively well.  They are double checking what is causing the artificial nose-dive of the very start of the TDS measurement.  For low frequency resolution, always use reverse sweeps, and always sweep a little bit wider than the bandwidth you want to examine.  Also watch out for not having enough resolution at low frequencies, where the absolute ideal is to have the filter width about 1/10th the lowest frequency of interest.  In other words, you can have extremely high confidence in data above 20Hz with the maximum filter resolution of 2Hz in the TEF20 or 25.  This doesn't mean that information below there is not valid, but you do have to be aware of potential problems with resolution and such as you go lower toward the 6Hz lower limit of the software.

My own TEF25 has been behaving largely as expected.  I also have the luxury of knowing that I'm essentially using the same setup that Gold-Line has in house in that I run an HP laptop and use the TEF-04 mic.

Do realize that Gold-Line often has multi-day workshops on the use of the TEF.  It's hardly a "point and shoot" product.

Regards,
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Mark Seaton
Seaton Sound, Inc.
"Make no little plans; they have no magic to stir men's blood..." - Daniel H. Burnham

Antone Atmarama Bajor

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Re: TEF 25 PROBLEMS!!! and TEF Subwoofer measurements.
« Reply #3 on: July 30, 2005, 02:01:44 pm »

     I just talked to Louis Yesterday, He's going to send us the bata software which he says is more thoroughly tested than.  6.7.1

    We're excited about 92kHz being activated.  A whole octave more resolution.

    As far as the space goes for testing subwoofers  100ft.  We don't have we might have 20 Or 30 ft.  Long maybe 100 Ft long parking lot sandwiched between 2 2 story warehouses. So not so good for doing long low sweeps, its going to let in all that good reflection between the buildings.

    I've got space on my property  We just need to haul the test rig over I guess with the TEF 25 up and running well hopefully That will be slightly easier.

    I've seen my bosses old TEF12 but I'm afraid of it.  It makes me want to cry.  

 By the way I was wondring about the validity of doing impedance sweeps under more power than 1k Ohm @ 1V.  Un fortunately the TEF 20 only can handle 1VRMS.  So I'm limited to 1V @ 1 Ohm or so.  But the TEF 25 can handle +24dBV  So I can explore it a little more.

 I need to double check my tests but I was testing a dual VC subwoofer with the TEF with its standard bridge and Fs stayed the same in all VC configurations.  When I tested it with a 1 Ohm bridge I was reading Fs the same at single coil and Parallel But the FS shifted up 10Hz in Series.  Odd!?

    Anyhow Happy hunting time to go do a gig.

-Sum

   
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Too Tall (Curtis H. List)

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Re: TEF 25 PROBLEMS!!! and TEF Subwoofer measurements.
« Reply #4 on: August 01, 2005, 10:44:34 am »

sumsound wrote on Sat, 30 July 2005 14:01

     I just talked to Louis Yesterday, He's going to send us the bata software which he says is more thoroughly tested than.  6.7.1

    We're excited about 92kHz being activated.  A whole octave more resolution.



Praxis will go up to 24bit/192kHz (if the soundcard is up to it), but I have not found a use for it yet.

96kHz comes in very handy for doing distortion measurements.

sumsound wrote on Sat, 30 July 2005 14:01


    As far as the space goes for testing subwoofers  100ft.  We don't have we might have 20 Or 30 ft.  Long maybe 100 Ft long parking lot sandwiched between 2 2 story warehouses. So not so good for doing long low sweeps, its going to let in all that good reflection between the buildings.



I have found that if the building has large garage doors that open a large percentage of the wall area you do not get much of a reflection from it. Something to consider when you decide where to put the speaker and mic.


sumsound wrote on Sat, 30 July 2005 14:01


    I've got space on my property  We just need to haul the test rig over I guess with the TEF 25 up and running well hopefully That will be slightly easier.

    I've seen my bosses old TEF12 but I'm afraid of it.  It makes me want to cry.  



Just in case you can not resolve your problems with Goldline may I suggest you look at Praxis for your needs-
http://www.libinst.com/

I am somewhat familiar with the TEF12, but it has been over 10 years since I played with one personally. A long time friend bought it back in the mid 80s. I learned how to use it in a rudimentary way back then and can totally relate to it making you want to “cry”. Back then classes were required to use something that was definitely NOT user friendly

The TEF20 is somewhat easier to use and the TEF25 might even be easier yet. That said I think you still need to learn WHY it works so you know what happens when you change a parameter. IOW except for getting lost in DOS menus you need to be able to set the TEF12 correctly to be able to use the TEF25 effectively.

One thing you have in your favor is that Tom and Mark seem willing to help. Also I have no reason to think that Goldline will not help you in any way they can short of coming to your house to wash the windows.

The TEF has been an exceptional product for years. This allowed them to sell something that was difficult to use. But that time has come when it is no longer “exceptional” and has competition on all sides. A few years ago if you wanted to “verify” any acoustical measurement a “TEF” was the default standard. These days most will gladly except a “Smaart” measurement.


sumsound wrote on Sat, 30 July 2005 14:01


 By the way I was wondring about the validity of doing impedance sweeps under more power than 1k Ohm @ 1V.  Un fortunately the TEF 20 only can handle 1VRMS.  So I'm limited to 1V @ 1 Ohm or so.




You can build a probe with a resistor L-PAD to reduce the voltage to a safe level. Praxis uses one as a matter of course on all measurement. Normally you take the reference right from the output of the power amp (for SPL and impedance) with the software compensating for the size of the L-Pad you use. With the standard probe Praxis is safe to about 30volts peak or 20volts RMS.

If you are brave you can push the voltage up around 200 volts peak, but at that point the wire used for hooking up on the end of the provided probes that come with Praxis may break down. There is a setting for telling Praxis what size resistor you are using so the program can show correct levels. Up around 200 volts peak it will go no higher no matter what size resistor you put into the program.

There are some severe warnings and the author washes his hand of you above 100 volts peak.

sumsound wrote on Sat, 30 July 2005 14:01


But the TEF 25 can handle +24dBV  So I can explore it a little more.

 I need to double check my tests but I was testing a dual VC subwoofer with the TEF with its standard bridge and Fs stayed the same in all VC configurations.  When I tested it with a 1 Ohm bridge I was reading Fs the same at single coil and Parallel But the FS shifted up 10Hz in Series.  Odd!?

    Anyhow Happy hunting time to go do a gig.

-Sum

   


Good Luck








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Too Tall
        Curtis H. List    
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Independent Live Sound Engineer (and I'm Tall Too!)
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