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pos
10-25-2014, 03:59 AM
It is known to most here that VC wire tend to heat with power, and the change of resistance that heat provoke has direct consequences on the response of the driver, shifting its BR alignment and reducing its sensitivity, ultimately limiting the maximum possible SPL.

This is the so-called "power compression" effect. JBL and other transducers manufacturers have been using vented motors and heavy metal parts to dissipate that heat and reduce the long term effect of it, improving long term maximum SPL.

But this phenomenon also has a less known immediate "compression" effect on peaks on which external dissipation techniques have no effect, because it does not have enough time to take place.
One way of dealing with this phenomenon is to use current drive amplifiers, but that is another subject.

Earl Geddes calls this effect "thermal modulation", and this phenomenon has also been brought to consideration recently by Charles Sprinkle here (https://www.youtube.com/watch?v=CDmzfpf3fCk#t=985), with what he calls dynamic compression.

This immediate effect has to be dealt with within the VC itself, by either increasing the mass of the VC (the bigger the VC the less it will heat), or by using special alloys whose resistance stays more stable with heat.

That is what Doug Button patented (http://www.google.com/patents/US5664023) for JBL in 1994, and called TCR:
http://www.jblpro.com/www/jbl-story/innovation/technology/material-innovations/tcr-voice-coil-wire

The M2 brochure explicitly states that this material is used in the 2216nd transducer, but it is not made clear in the EDS (http://www.audioheritage.org/vbulletin/showthread.php?33565-2216Nd), and to my limited knowledge no other transducer has been reported to be using that type of wire before, not even the 1500AL series.

Is that the case? Is the 2216nd the only woofer to use TCR wires?

Robh3606
10-25-2014, 05:03 AM
Hello Pos

Thanks I have been looking for that patent. I had no idea it was that old. As far as I know it's the only driver using it. Can't figure out why it's has not been more widely used unless there is an issue with using it in manufacturing and it took awhile to find a way to use it? Special solders it fatigues or what have you. Just a guess on my part. May be we will find out why.

There are some good conversations about it over on DIY. Earl is a big advocate of that type of compression. He seems to think that it is a real issue with conventional tweeters.

Rob

pos
10-25-2014, 01:04 PM
Hello Rob

Geddes says B&C is using a similar alloy which does not infringe the patent but brings ~90% of the effect...
I think it is a shame that power compression is always looked at and addressed in its "long term" effect.
Even the TCR description focuses on max SPL and not dynamic.
It was interesting to hear Charles Sprinkle speak about dynamic! :)

ivica
05-04-2015, 05:46 AM
It is known to most here that VC wire tend to heat with power, and the change of resistance that heat provoke has direct consequences on the response of the driver, shifting its BR alignment and reducing its sensitivity, ultimately limiting the maximum possible SPL.

This is the so-called "power compression" effect. JBL and other transducers manufacturers have been using vented motors and heavy metal parts to dissipate that heat and reduce the long term effect of it, improving long term maximum SPL.

But this phenomenon also has a less known immediate "compression" effect on peaks on which external dissipation techniques have no effect, because it does not have enough time to take place.
One way of dealing with this phenomenon is to use current drive amplifiers, but that is another subject.

Earl Geddes calls this effect "thermal modulation", and this phenomenon has also been brought to consideration recently by Charles Sprinkle here (https://www.youtube.com/watch?v=CDmzfpf3fCk#t=985), with what he calls dynamic compression.

This immediate effect has to be dealt with within the VC itself, by either increasing the mass of the VC (the bigger the VC the less it will heat), or by using special alloys whose resistance stays more stable with heat.

That is what Doug Button patented (http://www.google.com/patents/US5664023) for JBL in 1994, and called TCR:
http://www.jblpro.com/www/jbl-story/innovation/technology/material-innovations/tcr-voice-coil-wire

The M2 brochure explicitly states that this material is used in the 2216nd transducer, but it is not made clear in the EDS (http://www.audioheritage.org/vbulletin/showthread.php?33565-2216Nd), and to my limited knowledge no other transducer has been reported to be using that type of wire before, not even the 1500AL series.

Is that the case? Is the 2216nd the only woofer to use TCR wires?

Hi POS,

Thank You for the links and that You have reminded us about TCR. Here , I think, we have to be aware that TCR {aluminum alloy } has about 3 time less weight then copper (reducing the total movable mass by some percentage, may be 1/2 or 1/3), but about 3 time LARGER resistance per length., expecting the same wire length ( in order to get the same force ~BL). All that under home listening levels.

regards
ivica

1audiohack
05-04-2015, 06:43 AM
Hi All;

Warning , topic swerve!

When I first read about this wire I became very interested in it for a different application, stator windings in alternators. In off road racing with lights and cooling fans and all the electronics (GPS, engine management and data etc) we have trucks with average power demands of 140 Amps. The safe area of operation for an automotive type alternator in an endurance application is 70% of rated output. A 200 Amp racing alternator will settle right at about 140A output when it's good and hot and if you ask more from it, ie if the demand pulls the system voltage below about 13.5V it will fail. These alternators currently cost about $1200.USD and the cost of changing one during an event due to lost time can be incalculable. These trucks all use two of these alternators simultaneously.

So I thought hey if we could wind the stators out of this new magic wire, maybe we could run them closer to their rated output longer.

Back to JBL. I have had the good fortune to speak to Jerry Morro in person twice. On one occasion I asked him some very direct questions about this wire and since my questions had nothing to do with loudspeakers I hoped he would share with me, and he did.

In brief, there is no "something for nothing" and a very real issue with this wire is that it takes considerably more space to achieve the same ampacity as copper.

This I think is the rub in a single coil driver. It would be easier to split the Re between two coils and end up with something easy to drive while maintaining gap flux density. I imagine, and here I am guessing, that trying to get enough of this wire into a single coil while trying to obtain the desired gap flux density in a top plate of 1.600" like the 1500Al series drivers have, could be nearly impossible.

Barry.

ivica
05-04-2015, 09:22 AM
Hi All;

Warning , topic swerve!

When I first read about this wire I became very interested in it for a different application, stator windings in alternators. In off road racing with lights and cooling fans and all the electronics (GPS, engine management and data etc) we have trucks with average power demands of 140 Amps. The safe area of operation for an automotive type alternator in an endurance application is 70% of rated output. A 200 Amp racing alternator will settle right at about 140A output when it's good and hot and if you ask more from it, ie if the demand pulls the system voltage below about 13.5V it will fail. These alternators currently cost about $1200.USD and the cost of changing one during an event due to lost time can be incalculable. These trucks all use two of these alternators simultaneously.

So I thought hey if we could wind the stators out of this new magic wire, maybe we could run them closer to their rated output longer.

Back to JBL. I have had the good fortune to speak to Jerry Morro in person twice. On one occasion I asked him some very direct questions about this wire and since my questions had nothing to do with loudspeakers I hoped he would share with me, and he did.

In brief, there is no "something for nothing" and a very real issue with this wire is that it takes considerably more space to achieve the same ampacity as copper.

This I think is the rub in a single coil driver. It would be easier to split the Re between two coils and end up with something easy to drive while maintaining gap flux density. I imagine, and here I am guessing, that trying to get enough of this wire into a single coil while trying to obtain the desired gap flux density in a top plate of 1.600" like the 1500Al series drivers have, could be nearly impossible.

Barry.

Hi Barry,

I believe that using such high resistivity wire Al-Mg for the generator, would be a problem as using the same wire cross-section area stator internal resistance would be about 3 times larger then using copper wire, so 3 times more thermal dissipation would be introduced, so to reduce such things You would have to use sqrt(3)=1.73 larger wire diameter then when copper used wire. (almost double). May be using squired cross-section wire can help a little, wire become about 1.36 the size of the copper round cross-section wire, so your generator would be larger, but the total weight would be may be the same (more iron and less copper)

regrds
ivica

Hoerninger
05-04-2015, 10:12 AM
Just for your convenience try
http://www.pat2pdf.org/
with
5664023
resulting in
http://www.pat2pdf.org/patents/pat5664023.pdf
____________
Peter

ivica
05-04-2015, 11:39 AM
Just for your convenience try
http://www.pat2pdf.org/
with
5664023
resulting in
http://www.pat2pdf.org/patents/pat5664023.pdf
____________
Peter

may be as POS 'said':
http://www.google.com/patents/US5664023

rgards
ivica

Hoerninger
05-04-2015, 01:51 PM
may be as POS 'said ...
Of course, but easier to download and read.
___________
Peter

pos
05-23-2017, 06:48 AM
It appears from this thread (http://www.audioheritage.org/vbulletin/showthread.php?39756-My-visit-to-Greg-Timbers-home-invited-by-Greg-Burns-of-Home-Audio-Sound&p=405800#post405800) that the 2213Nd-2 in the 4312E also uses low TCR voice coil material (as would have the 1501AL-3 if Greg and Jerry would have been given the chance to design a new Everest...).


Also, Jerry Morro stopped by as well. It was great hearing his stories about woofer design as well. How had the engineering staff remained historically in tact, that potentially the next Everest woofers would have used TCR wire, like that used in the 2216 and 4312E woofer. Instead of trickle down tech, it would have been trickle up.