Percieved impact of upgrading Lab12 VC to 3" - diyAudio
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Old 22nd October 2013, 02:58 AM   #1
sine143 is offline sine143  United States
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Default Percieved impact of upgrading Lab12 VC to 3"

After seeing the new QSC product go up, with what looks to be lab12 drivers (with 3" vc's) forum member MRGSR brought up the idea of a possible group buy on a 3" VC lab12. Minimum order is 50 from eminence for any OEM design.

First things first, how do we think this "upgrade" will effect TS parameters? what other changes to the driver will need to be made to accommodate (obviously different spider)?

My initial hunch (and this is coming from someone with admittedly very little knowledge of actual driver design, beyond a basic understanding of T/S specs), is that we will see an increase in LE, and possibly a rise in FS (smaller spider would likely be stiffer?) and a possible decrease in xmech due to said smaller spider size. The dustcap is already ginourmous, so cone topology would likely stay the same.

The big question. would this be a drop in replacement for lab12s in popular present day designs (labsub I'm looking at you and your thermal failure rate), and will it work BETTER (ie, more thermal powerhandling, better thermal dissapation rate)


footnote:

I've considered perhaps pursuing a lab12 that keeps the same VC, but adds a copper tube around the pole piece (a la, AE TD18h, which boasts a 2.5" coil and 1000 watt PE, granted a much higher xmax as well for better cooling). This would theoretically lower LE as well (although for sub use this is arguably a non issue with the labs already low 1.41 LE).

What do you guys think?
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Old 22nd October 2013, 03:41 AM   #2
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Changing the VC size likely changes absolutely every T/S parameter. The only one that may not change is Xmax, which if you follow Eminence's own convention, is simply the one-way voicecoil overhang (for overhung drivers). Sd also should remain the same, but that's about it.
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Old 22nd October 2013, 04:00 AM   #3
wg_ski is offline wg_ski  United States
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Keeping all the T/S the same would not be the goal. Improved dissiaption capability, along with a set of parameters compatible with 30 Hz tuned horns would be.
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Old 22nd October 2013, 06:35 AM   #4
djk is offline djk
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Not worth doing.

Make Wayne Parham's heatsink plug for them.
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Old 22nd October 2013, 02:24 PM   #5
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Design subs that have proper driver cooling and you don't need a giant voice coil.
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Old 22nd October 2013, 05:27 PM   #6
sine143 is offline sine143  United States
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Quote:
Originally Posted by wg_ski View Post
Keeping all the T/S the same would not be the goal. Improved dissiaption capability, along with a set of parameters compatible with 30 Hz tuned horns would be.
The easiest way to do that would be to minimize effects on T/s Parameters.

Quote:
Design subs that have proper driver cooling and you don't need a giant voice coil.
3" is not a giant voice coil. also, note that I also listed methods to improve driver cooling, sans increasing VC size (copper pole piece sleeve).
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Old 22nd October 2013, 05:42 PM   #7
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Keeping the voice coil dia same. Consider upgrading voice coil material such as fiber-glass former and modified winding material such as 4 layer flatwound copper wire or a different winding technique, such as inside/outside winding.
End result will be lower power compression at higher temperature.
Flatwound aluminum wire coil will also bring VC inductance down.

Last edited by SIDEWINDER 18X; 22nd October 2013 at 05:49 PM.
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Old 22nd October 2013, 05:58 PM   #8
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Eminence drivers have greater gap width in their motor structures. And Lab12 is no exception. The result is lower gap strength & poor thermal transfer from vc to t-yoke and front washer. If gap width can be altered and narrowed down, it can change and solve lots of issues.

Last edited by SIDEWINDER 18X; 22nd October 2013 at 06:09 PM.
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Old 22nd October 2013, 06:10 PM   #9
wg_ski is offline wg_ski  United States
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The greater gap width allows the use of round-wire voice coils, and gives lots of room for thermal expansion before things go haywire. But you get lesser performing drivers than you do with ribbon-wire VCs and tight tolerances. A lot less expensive, too. Look at Chinese drivers - they are even more extreme in this regard. And the stupid-high Qts values show it.

It would be interesting to see the result of a Lab12-form-factor driver with a more modern motor, and see if a pair ends up more useful than a single 18 of equivalent Sd.
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Old 22nd October 2013, 06:30 PM   #10
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Quote:
Originally Posted by wg_ski View Post
The greater gap width allows the use of round-wire voice coils, and gives lots of room for thermal expansion before things go haywire.
Similar rated and coil sized drivers with round wires are built with much lesser gap width than Eminence and are not Chinese. eg: RCF, 18Sound, Celestion, Meyer Sound/ Ciare and many others. And their faliure rate is lesser than Eminence.
and I had referred to flatwound ribbon voice coil not edgewound ribbon coils.
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