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Author Topic: Prosound Shootout 2007  (Read 43927 times)

Wayne Parham

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Re: Prosound Shootout 2007
« Reply #20 on: July 31, 2007, 09:31:08 pm »


Pascal Pincosy wrote on Tue, 31 July 2007 18:03

What's the plan for taking measurements this year? I'd like to see someone who is not affiliated with a manufacturer at the controls this year.


Me too, absolutely.  We had hoped to get one of the forum regulars that was unaffiliated with any manufacturer to perform the measurements at past Prosound Shootouts in 2005 and 2006.  When that couldn't be arranged, all the exhibitors discussed the problem of who would do it and we agreed to self-police.  It really wasn't a problem, but it is more objective if an outside party runs the show.  It's also allows the exhibitors to focus on setup rather than to divide their time between that and taking measurements.

We did have a formal test plan that worked pretty well for us.


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Ivan Beaver

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Re: Prosound Shootout 2007-Testing ideas-wasting time
« Reply #21 on: August 01, 2007, 05:36:10 pm »

Here is what I suggest so as not to waste to much time and get data and HAVE FUN!

This is derived from the shootout in NYC in Jan.

Since you are limited on time-you really need to make the most of it and make it enjoyable for those who have made the effort to attend.

While this was a great time to "mix it up" I think a lot of the people got tired of all the testing.  Mark was way to busy being sure to get it right and fair.  He had little time to mingle, whfcih I am sure he would have liked to do more of.

My suggestions.

Forget impedance.  There is no such thing as a 1 watt input anyway as the impedance varies with freq.  Just accept the manufacturers ratings.  Use a standard of 2.83V (2.828 to be exact Laughing ) as a reference and let the people viewing "determine" what they feel the wattage is at any particular point on the curve.

Just run a single test 28.28V (100watts for 8 ohms) and measure at 10 M.  This is the Danley standard so the cabinet frontal area will not affect the measurement any and 100 watts on a swept sine wave to actually get some driver a little into power compression and is more realistic of actual levels than 1 watt.  It will back calculate to 1W/1M for reference (@8 ohms)

If a cabinet is rated at 4 ohms, then just subtract 3dB from whatever freq you are looking at to derive the sensitivity.

I don't think you need 3 measurements that agree to have accurate data.  If you do, then you need a different analyser, because the one you are trying to use is obviously NOT accurate and cannot be trusted from loudspeaker to loudspeaker.

I suggest a TEF.  It is rock solid and if setup properly-the output level will not vary and can be easily calibrated with a calibrator for the best accuracy, not relying on "preset" data for calibration.

There is no reson to measure the amplifier you are using-if you EVEN think that there would be anything there that would affect the data, then you need a different-better quaily amplifier.

Distortion measurements can have some meaning, but most people would rather trust their ears.  I would rather spend the time listening to different cabinets than to be measuring distortion.

A really good idea is to use a speaker level switcher to switch between cabinets so side by side comparisons can be made.  It is often quite difficult to listen to a loudspeaker and then listen to another sevral minutes later and try to come to any real conclusions about the differences.

Danley uses a 6 channel unit that I built that shorts the unused outputs when not being used so the side by side cabinets do not interfer with each other (much).

As far as who is doing the testing-as long as it is done fair and NOTHING changes from test to test and with a qualified measurement system, then I have no problem with whoever drives.  I know the idea is that a manufacturer could "cheat" a little, but if they did, they (and their product/company) would never live it down and would be ridiculed and not trusted with every post they would make here.  To me it would simple be to much of a gamble to take-just to fudge some data.

What I did at NY was to get Mark to give me the raw data he had saved, on my stick, so if he tried (which I know he wouldn't) to manipulate the data, it would be different than mine, therefore causing problems/issues with the procedure.

Let the data and the cabinets stand for themselves and do a LOT more listening.  At NY we had the whole 2nd day for listening-and I wish we could have done some side by side tests, but the space restrictions made it really hard, but you do not have that problem and product can be more quickly moved in and out of the testing area.

Good luck with the shootout.

PS Be sure sure to get ahold of a BIG amplifier, you might need it for some of the cabinets.  Twisted Evil

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Wayne Parham

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Re: Prosound Shootout 2007-Test Procedures
« Reply #22 on: August 01, 2007, 08:35:54 pm »


Good suggestions, Ivan, thanks.  I agree with what you've said.

Ivan Beaver wrote on Wed, 01 August 2007 16:36

Since you are limited on time-you really need to make the most of it and make it enjoyable for those who have made the effort to attend.


That's for sure.  I've done a couple of these already and time is short during the event.

Ivan Beaver wrote on Wed, 01 August 2007 16:36

Forget impedance.  There is no such thing as a 1 watt input anyway as the impedance varies with freq.  Just accept the manufacturers ratings.  Use a standard of 2.83V (2.828 to be exact Laughing ) as a reference and let the people viewing "determine" what they feel the wattage is at any particular point on the curve.


That might be a good idea.  We measured every speaker with 28.3v at 10 meters.  I'm pretty happy with that dataset.  But I do like to have different power levels too, because many speakers change characteristics at high power levels.  The heat makes electro-mechanical parameters shift, and some speakers start to get peaky on the bottom end as a result.  We can also check distortion at these different power levels too, which is something I think most people want to know.

The impedance sweep is actually very easy.  Once we have it, a quick couple of buttons of the calculator tell you the voltage required to get 100 watts, 200 watts, 400 watts, 800 watts, and so on.  It's just not that much trouble and gives us some valuable data.

Then again, even a quick test takes time, and a bunch of quick tests make a long day.  So we may be better served doing fewer tests.  Maybe one at 28.3v and another at say 500 watts and another at 1000 watts or something like that.

Ivan Beaver wrote on Wed, 01 August 2007 16:36

I don't think you need 3 measurements that agree to have accurate data.  If you do, then you need a different analyser, because the one you are trying to use is obviously NOT accurate and cannot be trusted from loudspeaker to loudspeaker.


Absolutely.  I've seen some systems that I wouldn't trust without multiple dataset agreement.  But the LMS system is calibrated and is rock solid.  There is no need for three sweeps.

Ivan Beaver wrote on Wed, 01 August 2007 16:36

I suggest a TEF.  It is rock solid and if setup properly-the output level will not vary and can be easily calibrated with a calibrator for the best accuracy, not relying on "preset" data for calibration.


I personally like LMS.  It has worked very well for me.  But TEF would probably be great too.  I've always heard good things about it.  I don't want any of us to feel like we've been forced to use a system dictated to us though.  The group must be comfortable, not just one or two vocal participants.

I think the measurement system decision will likely be dictated by availability and familiarity.  I am thinking that probably with this bunch of folks, we are going to need to be very careful with each person's comfort level.  We would be best served with measurements made by an independent third party, someone we all trust.  But whether that is possible or not has yet to be seen.  One thing for sure, I don't want anyone there to be uncomfortable with the quality of measurements or the person performing and storing them.  I personally do not want any massaging of data, including smoothing.  I want the datasets to be published exactly as they are captured.  Scaling should be the same for all published response graphs too.

Ivan Beaver wrote on Wed, 01 August 2007 16:36

There is no reson to measure the amplifier you are using-if you EVEN think that there would be anything there that would affect the data, then you need a different-better quaily amplifier.


We've never had trouble with this.

Ivan Beaver wrote on Wed, 01 August 2007 16:36

Distortion measurements can have some meaning, but most people would rather trust their ears.  I would rather spend the time listening to different cabinets than to be measuring distortion.


Not me.  I want distortion graphs.  One of the biggest differences between direct radiators and horns is their distortion characteristics.  Horns have different distortion characteristics too.  I think it is interesting to see the trends as power levels are increased too.

Ivan Beaver wrote on Wed, 01 August 2007 16:36

As far as who is doing the testing-as long as it is done fair and NOTHING changes from test to test and with a qualified measurement system, then I have no problem with whoever drives.  I know the idea is that a manufacturer could "cheat" a little, but if they did, they (and their product/company) would never live it down and would be ridiculed and not trusted with every post they would make here.  To me it would simple be to much of a gamble to take-just to fudge some data.


I agree, but only if everyone present respects one another and are pretty familiar and friendly towards one another.  I think that's the way things should be and hopefully will get to be.  But I also think that thre are some smouldering resentments and trust issues between some of the guys that might consider coming.

I'm not just talking about some of the more vocal guys you might expect to be mistrustful, I'm also talking about people that have been publically quiet so they didn't get attacked by others or just generally to keep from rocking any boats.  I'd like everyone to feel comfortable and respected, not bullied or badgered.  I think that's possible.  At least, I hope so.

Ivan Beaver wrote on Wed, 01 August 2007 16:36

What I did at NY was to get Mark to give me the raw data he had saved, on my stick, so if he tried (which I know he wouldn't) to manipulate the data, it would be different than mine, therefore causing problems/issues with the procedure.


Please don't take this wrong.  You're trying to be helpful, and I really appreciate that.  I think you have an olive branch in your hand, and I do too.  So please just take this statement as objectively as possible.

You and Mark Seaton are both personal friends and business associates with Tom Danley.  The fact that the data was gathered, organized, processed and published by you and Tom made some people pretty uncomfortable.  They told me so.

Again, please don't take that wrong.  I saw what you guys did and I could tell you were trying to be fair.  But please understand that it's the same thing as if Danley had to trust measurements I made, processed and published.  He has been pretty vocal that he would be uncomfortable with that.  I understand, and I don't expect him to be forced to accept a situation that makes him uncomfortable either.

We'll need to work in a spirit of understanding and cooperation to find and agree on methods that everyone is comfortable with.
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Michael Hedden Jr.

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Re: Prosound Shootout 2007-Test Procedures
« Reply #23 on: August 01, 2007, 10:16:15 pm »

You and Mark Seaton are both personal friends and business associates with Tom Danley.  The fact that the data was gathered, organized, processed and published by you and Tom made some people pretty uncomfortable.  



Interesting that after the NY event there was quite a bit of folks asking for the data to be published.  Mark Seaton had already bitten off way more than he wanted to chew and wasn't going to waste any more time with it.  We waited several weeks and when nothing was done we published the data both organized and raw and put it up for peer review on the Danley site.
Tom spent several hours of his time putting that data together so folks that didn't own TEF could see the data.  If anyone has an issue with Tom Danley's credibility I'd love to hear about it.
The bigger issue we are dealing with is a very niche subject for the majority of our industry.  I've worked with TEF workshops around the country and you'll get maybe 30 folks to show up, it just isn't interesting to the majority of the industry.
Of the folks that are interested, few own serious measurement systems or are in a work environment that allows daily use of the systems which is the only way to develop aptitude on how to properly apply the systems.

Ivan Beaver is a dear friend and it has been my great pleasure to work with him for years.  Mark Seaton is also a good friend but doesn't work in any capacity with Danley Sound Labs.  Both Ivan and Mark are in the small minority of folks with the technical chops to do measurements right and you'll have a very difficult time finding their equals much less superiors.

Peer review is a way to insure integrity but most of the measurement Jedi's I know are too busy doing their own thing.
Three of them participated in some capacity with the NY shoot out and the response has been tepid at best.  What is the incentive of them or others, especially without ties to manufacturers participating in more?

Mike Hedden
Danley Sound Labs, Inc.
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John Roberts {JR}

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Re: Prosound Shootout 2007-Test Procedures
« Reply #24 on: August 01, 2007, 11:36:42 pm »


good luck...  Laughing

JR.


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Tim Padrick

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Re: Prosound Shootout 2007-Testing ideas-wasting time
« Reply #25 on: August 02, 2007, 12:05:57 am »

Ivan Beaver wrote on Wed, 01 August 2007 16:36

A really good idea is to use a speaker level switcher to switch between cabinets so side by side comparisons can be made.  It is often quite difficult to listen to a loudspeaker and then listen to another several minutes later and try to come to any real conclusions about the differences.


I find "immediate switching" comparisons to be much less telling than listening to 30 seconds of music, making the switch, and listening to another 30 seconds of music.  As I have never done this with "under 100Hz only" transducers, I will grant you that it may not work for subwoofers, unless they are run with (and properly aligned with) tops, which would be a very time consuming process that I'm sure would be outside the scope of the Shootout.

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Re: Prosound Shootout 2007-Testing ideas-wasting time
« Reply #26 on: August 02, 2007, 12:07:25 am »

Ivan Beaver wrote on Wed, 01 August 2007 16:36



Good luck with the shootout.

PS Be sure sure to get ahold of a BIG amplifier, you might need it for some of the cabinets.  Twisted Evil




May I suggest the Powersoft K10, I recently put one in at a nightclub install, and is now my sub amp of choice (makes a Lab Gruppen 6400 sound broken) Don't jump down my throat Lab Gruppen fans, I still love them.  I am just setting a very familiar subjective benchmark.

So unless Powersoft wants some press and decides to let you gents get your hands on the elusive yet to be seen K20,  please consider the Powersoft K10.  
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Ivan Beaver

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Re: Prosound Shootout 2007-Test Procedures-Impedance questions
« Reply #27 on: August 02, 2007, 08:20:16 am »

The impedance issue is where it really gets to be picky/touchy.  If you do an impedance sweep, then what is the actual impedance?  WHo is going to determine that?  It is generally considered NOT to be the lowest point on a curve, but rather a "average" that relates to a standard "number".  In just about every loudspeaker, there are more points that are much higher in impedance than those that are lower.

I do not know of any manufacturer (there might be some) that uses the lowest point on the curve as the impedance number.  So if you do that, then somehow you are saying that you are "better" than the rest of the industry and want to do things differently than currently accepted.  That is very open to discussion.

SO the nubmer you choose is now a determination by who?

And to further complicate it, you now have to reajdust the sending level to change the output voltage.  So now you have  adjusted something.  It is all of these little adjustments that start to be the "problem", and start to bring up question regarding how the data was collected.

What if you choose a different number in terms of the impedance than someone else does, then who is right?

I say put a constant voltage into all the loudspeakers and go from there.

I used to be in the other camp and was wanting to simply put 1 watt in(changing voltage with different impedance), but started to realize all of the issues this brings up and am now in the camp of 2.83V and figure out the wattage that was applied from there.  After all the wattage applied is different for all points on the curve and is only valid for one (and equal points of impedance).

WIth the TEF you can change the scales with post processing to account for different wattages/voltages so you can do a comparisom anyway you want. That is what Tom did after the NY shootout, but people were generally not interested ins seeing that, partly because they did not trust him, but I will tell you, Tom is one of the most anal people in this industry regarding real specs, and what he does can be trusted totally.  He was not trying to play any games, but just rather present data in a way that would be easier for some to understand.

I would rather trust data that simply had scales moved up or down by a certain amount of db, much sooner than changing levels between measurements and those levels would be based upon a "determination" by someone, that could be easily be a different number as judged by someone else.

THAT is your big variable

Regarding who is doing the measuring (they are not hiding behind a curtain(are they?), one hting to consider is qualifications.

Is it better to have someone who has no relation to a manufacturer and has little experience in doing all of these types of measurements or someone who does this all the time and is aware of all the issues/problems that arrise and can head them off ahead of time and ensure accurate data?

If some people don't trust others to do measurements with someone looking over their shoulder. then I think they personally have a problem.

I would rather have a  qualified person who does this for a living, anyday over someone who just does this on the side or part time or as a "hobby".  This is not saying anything about who has been making your measurements-I don't know who that is, but rather about the attitude of people regarding who is doing the measurements.

The ONLY agenda of the measurement person should be to collect accurate data in a way that is industry accepted so that people can make their own determinations about the suitability of a product for a particular project.  PERIOD.  If they do anything to make one product look better or worse, they need to be exposed as a fraud.  

The only way to ensure accurate/compariable data is to measure all of it the SAME way.  Then people can post process it anyway they want-either mentally or with a program to determine what is what.  IF you start changing drive levels, then it really gets hard to figure out what is what.
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Mark Coward

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Re: Prosound Shootout 2007-Testing ideas-wasting time
« Reply #28 on: August 02, 2007, 10:02:33 am »

I see that the Powersoft K10 is suggested. Where is the data published from the NY shootout? I read this in the NY shootout section on the JTR site, it doesn't say who is being quoted:
http://www.jtrspeakers.com/2007_shootout.html

Quote:


Many of the speakers did not leave unscathed as three out of the five subwoofers prior to the Growlers had fallen victim to the PowerSoft K10 amplifier’s 10,000 watts. One channel of the amplifier when hooked up to each of the two Growlers is capable of 4000 watts.


This is a little misleading according to the Powersoft and JTR specs, the Growlers are 8 ohm and the K10 is 2,000w RMS @ 8 ohm per channel. Both cabs on one side of the amp would be 4 ohm, and the amp is 4,000w RMS @ 4 ohm. The way I read the above, it sounds like it was one Growler per channel - but in either case, it would have been 2,000w max per cab.

I would really like to see some test results for power compression. What advantage is there in powering a 1,000w RMS driver with 2,000w RMS of amp, if power compression sets in at 500w?
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Wayne Parham

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Re: Prosound Shootout 2007-Test Procedures-Impedance questions
« Reply #29 on: August 02, 2007, 11:51:09 am »


Ivan Beaver wrote on Thu, 02 August 2007 07:20

The impedance issue is where it really gets to be picky/touchy.  If you do an impedance sweep, then what is the actual impedance?  WHo is going to determine that?  It is generally considered NOT to be the lowest point on a curve, but rather a "average" that relates to a standard "number".  In just about every loudspeaker, there are more points that are much higher in impedance than those that are lower.


The impedance sweep is quick and easy to do.  I see no reason to omit it.  At least then, people can see the exact impedance curve rather than depending on an advertised impedance value.

Many manufacturers have already expressed concern that without impedance being taken into consideration, their loudspeakers SPL appears to be lower than others.

We chose minimum impedance because it is a fixed tangible value.  Average impedance is subject to interpretation.  Minimum impedance works very well for setting power reference levels to compare SPL between speakers.

Ivan Beaver wrote on Thu, 02 August 2007 07:20

I used to be in the other camp and was wanting to simply put 1 watt in(changing voltage with different impedance), but started to realize all of the issues this brings up and am now in the camp of 2.83V and figure out the wattage that was applied from there.  After all the wattage applied is different for all points on the curve and is only valid for one (and equal points of impedance).


I agree with you about measuring using a fixed voltage.  In the technical sense, all measurements are made with a fixed voltage anyway.  Amps aren't contant-power sources.  But the point is, it's nice to gather data that reflects SPL at different reference levels, and many people are used to seeing power level references.

We measured using 28.3v, which from 10 meters away gives the same SPL as 2.83v at 1 meter.  We also measured using 100 watts at 10 meters.  This gave the same SPL as 1W/1M.  After that, we doubled power and ran another sweep, continuing to do this until we reached maximum power.  I kind of like that approach.  You get both voltage reference charts and power reference charts.

Ivan Beaver wrote on Thu, 02 August 2007 07:20

I do not know of any manufacturer (there might be some) that uses the lowest point on the curve as the impedance number.  So if you do that, then somehow you are saying that you are "better" than the rest of the industry and want to do things differently than currently accepted.  That is very open to discussion.


Most manufacturers publish an advertised impedance, which is the closest multiple of 4 or 8 ohms.  It's almost an arbitrary number.

Ivan Beaver wrote on Thu, 02 August 2007 07:20

SO the nubmer you choose is now a determination by who?


Exactly.  That's why we chose minimum impedance.  Minimum impedance isn't a value that requires interpretation or calculation.

Average impedance is always higher than minimum impedance.  Using minimum impedance to calculate power, one sends a smaller voltage to the speaker than they would if they calculated using average impedance.  The signal presented to the speaker then causes it to dissipate the expected power level at frequencies where impedance is minimum.  At other frequencies, where impedance is higher, power dissipation is lower.  So the measurement reflects a conservative SPL.  It is, however, uniformly done across all speakers without interpretation.

The only way to accurately find average impedance it to take the measured impedance chart and find the area under the curve.  But even this is subject to interpretation because you have to choose the frequency range to use.  If you use DC to 100Hz, average impedance will be lower than if you choose 20Hz to 20kHz.  At lower frequencies, reactive impedance from voice coil inductance isn't significant but at high frequencies, it dominates.  So no matter what you do, average impedance is an interpretation.

Sure, you can say the range chosen should be the intended bandwidth of the device.  But even that gives a little "wiggle room" because the band chosen for determining impedance can be shifted down, say from 30Hz-150Hz to DC-150Hz.  This would give a lower average impedance, even if precisely calculated using the area under the curve.  A small horn would be used over a different frequency range than a larger horn, so do you set a fixed band to calculate average impedance?  Or do you let someone pick it?  This leaves room for interpretation, which gives some ambiguity.  It lets the person driving make choices that can offset the results, even if average impedance is precisely calculated.

That's why I suggest minimum impedance be used.  If someone else has a suggestion for a method that can be accurately and uniformly applied, I'd love to hear it.

Ivan Beaver wrote on Thu, 02 August 2007 07:20

And to further complicate it, you now have to reajdust the sending level to change the output voltage.  So now you have  adjusted something.  It is all of these little adjustments that start to be the "problem", and start to bring up question regarding how the data was collected.


To measure SPL at a fixed power level across various loads, you have to adjust voltage to account for impedance, that's right.  But if you don't, then you have to massage the data to come up with the same thing.  I think it is much better to have the exhibitor right there, watching the dial and seeing the voltage level set for his speaker before the test is run.  He is then comfortable that his speaker has received the signal appropriate for the power tested for.  Then when he sees the charts published, he can be comfortable that his speaker got a fair test.

Ivan Beaver wrote on Thu, 02 August 2007 07:20

WIth the TEF you can change the scales with post processing to account for different wattages/voltages so you can do a comparisom anyway you want. That is what Tom did after the NY shootout, but people were generally not interested ins seeing that, partly because they did not trust him, but I will tell you, Tom is one of the most anal people in this industry regarding real specs, and what he does can be trusted totally.  He was not trying to play any games, but just rather present data in a way that would be easier for some to understand.


I don't think we should post-process because of the trust factor.

To adjust a response chart to account for impedance differences, you still have to calculate using an impedance figure.  This figure must be interpreted at some point, be it minimum impedance or average impedance.  Then the data has to be massaged to account for the difference.  I personally would prefer that the impedance be measured rather than using advertised impedance or some other arbitrary figure to calculate an offset and then later massage the data.

I would welcome looking at other approaches to calculate power, but I don't think we should avoid power-reference measurements, choosing to make only voltage-reference measurements instead.  I think we should do both.

Ivan Beaver wrote on Thu, 02 August 2007 07:20

Is it better to have someone who has no relation to a manufacturer and has little experience in doing all of these types of measurements or someone who does this all the time and is aware of all the issues/problems that arrise and can head them off ahead of time and ensure accurate data?


Naturally, it would be best if we had a qualified, independent and unaffiliated third-party.  If that's not possible, we should self-police.  But if we are going to self-police, we must be extra careful to make everyone comfortable.

Ivan Beaver wrote on Thu, 02 August 2007 07:20

If some people don't trust others to do measurements with someone looking over their shoulder. then I think they personally have a problem.


Absolutely.  The measurement process and data should be open for inspection.

That's how we did it the past two years.  I did the test plan and measurements in 2005, and everyone watched.  When I set the voltage levels for the fixed-power measurements, I showed the exhibitor being measured the impedance chart, picked the minimum impedance, calculated voltage required to set power and showed the exhibitor that.  Then turned the LMS oscillator on and set voltage, showing the exhibitor the meter.  Everyone watched, the whole thing was open and I think everyone felt comfortable with the process.

David Lee did the measurements in 2006 and he basically did the same thing, but with a different system (Praxis) which had a different setup.

I am definitely open to suggestions and don't think I should be the final decision-maker, just like I don't think you or Mark or Tom should be.  I think everyone would be better served with a concensus.  So I definitely appreciate your input.

I think we agree in most things, but there are a few I think we might still need to hash through.  Fixed-power measurements and impedance determination are two of them.  Please look through my comments above and tell me what you think.
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