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Why don`t we see more widespread use of PUSH PULL Double VC speakers?

190.56.57.129
Posted on January 17, 2012 at 13:17:14
nicolas


 
PUSH PULL DOUBLE VOICE COIL DYNAMIC SPEAKER

Why don`t we see more widespread use of this voice coil (VC) arrangement especially in Prosound. It seems to have many benefits including doubling acceleration, quadrupling power output all without requiring more power input. Additionally it does not seem to require major chassis modifications over single VC designs. What are the negatives?

Yes longer double VC has more resistance greater heat etc but many woofers already have double VC and using only single magnetic gap.

 

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RE: Why don`t we see more widespread use of PUSH PULL Double VC speakers?, posted on January 17, 2012 at 23:17:12
David Yost
Audiophile

Posts: 959
Location: Atlanta
Joined: May 12, 2006
 Please post an example of the type of speaker you are talking about. I am having trouble visualizing what it is you have in mind.

 

RE: Why don`t we see more widespread use of PUSH PULL Double VC speakers?, posted on January 18, 2012 at 05:39:03
Bill Fitzmaurice
Industry Professional

Posts: 5371
Location: New England
Joined: October 20, 2002
 "Please post an example of the type of speaker you are talking about."

Perhaps something like the JBL 2268.

 

RE: Why don`t we see more widespread use of PUSH PULL Double VC speakers?, posted on January 18, 2012 at 06:36:24
b.l.zeebub
Audiophile

Posts: 9361
Location: 52deg 28'N,1deg56'W
Joined: April 17, 2006
 JBL was what came to my mind too.
Could be that they have a patent out on that though which would explain everything.

 

RE: Why don`t we see more widespread use of PUSH PULL Double VC speakers?, posted on January 18, 2012 at 10:24:09
rafaroxlm@yahoo.com
Audiophile

Posts: 158
Joined: July 30, 2005
 Believe PP double VCs look like post below. Image did not come out on this one. And yes because of close to doubling velocity because of PP double VC they have the potential to quadruple power output since Power output is related to volume of air X its velocity square. Seems similar to projectile (bullets) equations Energy= E=MASS x VELOCITY squared
Rafaro

 

RE: Why don`t we see more widespread use of PUSH PULL Double VC speakers?, posted on January 18, 2012 at 10:28:45
rafaroxlm@yahoo.com
Audiophile

Posts: 158
Joined: July 30, 2005



PP DVC
Rafaro

 

Have a look at this:, posted on January 18, 2012 at 10:59:32
b.l.zeebub
Audiophile

Posts: 9361
Location: 52deg 28'N,1deg56'W
Joined: April 17, 2006
 http://www.jblpro.com/pub/technote/JBL_TN%201-33%20rev3.pdf

 

RE: doubling acceleration, quadrupling power output all without requiring more power input., posted on January 18, 2012 at 12:50:41
badman
Reviewer

Posts: 8801
Location: Tustin, CA (Orange County)
Joined: March 10, 2001
 I call BS. Got a source? Seems to me a given amount of flux must be distributed between the gaps. There is no output benefit that I can tell. The only advantage is in improvements in power handling and linearity.



Bass is supposed to sound big. 6.5" is not a woofer size.


 

RE: Why don`t we see more widespread use of PUSH PULL Double VC speakers?, posted on January 18, 2012 at 14:09:35
David Yost
Audiophile

Posts: 959
Location: Atlanta
Joined: May 12, 2006
 Hello, Nicolas

In the JBL technical paper, at least, none of the benefits you mention are described. Instead, they claim reduced weight, more compact magnet structures, better heat dissipation, inherent magnet shielding, etc. IOW, there doesn't seem to be much advantage to the double VC outside of PA or stage/studio monitor use.

 

The Nagle speaker, posted on January 18, 2012 at 15:59:14
Iron Knee
Audiophile

Posts: 955
Location: Middle Florida
Joined: May 17, 2009
 Tenna "mindblowers" were such an example. The pnp pushed one coil and the npn pull the other coil, all on the same bobbin.


 

RE: The Nagle speaker, posted on January 18, 2012 at 18:19:14
djk
Manufacturer

Posts: 6135
Joined: June 17, 2000

They used two NPN devices connected to the center-tap on the voice-coil.

 

RE: The Nagle speaker, posted on January 19, 2012 at 10:41:21
Iron Knee
Audiophile

Posts: 955
Location: Middle Florida
Joined: May 17, 2009
 I Must have mis-read. Thank you for the correction.

 

RE: Why don`t we see more widespread use of PUSH PULL Double VC speakers?, posted on January 20, 2012 at 23:08:02
Head_Unit
Audiophile

Posts: 269
Location: Los Angeles
Joined: February 5, 2004
 First off, it's not used in autosound because it increases the speaker depth. That also kills it for current on-wall home designs, in-TV designs, and of course deeper doesn't work well for in-wall designs.

As for "doubling acceleration, quadrupling power output all without requiring more power input."
Er, no. It's not really as said in your later post. I don't think the acceleration doubles. Maybe. But two coils does NOT mean twice the coil...the coil becomes longer but the windings must be thinner (or something like that, I haven't looked at this design in some years). Two magnet gaps does NOT mean twice the magnetic strength; the gap effectively becomes wider reducing the strength kind sorta.

I know I'm putting it all vaguely, but basically this design is complicated and expensive. That is only justified apparently in pro sound applications, and I think a very few autsound designs including Alpine (depth-no-object custom install speakers, not factory drop-in).
And power output is limited by excursion, not the coil. Rockford was testing some coils that didn't melt until like 4000 watts of input-no, I'm not kidding-but their problem was to have the mechanicals keep up. This split coil actually limits the excursion when one coil starts to go into the other gap-it becomes an electromagnetic brake.

"Additionally it does not seem to require major chassis modifications over single VC designs." Well, maybe not chassis mods, but magnet mods and tooling and assembly for sure.

 

apples and oranges, posted on January 21, 2012 at 14:37:56
nicolas


 
JBLs differential drive is not Push pull double VC. The image above is correct for PP double VC

 

My Tenna Mind Blowers had only standard 8 Ohm non-center tapped single voice coil speakers, posted on March 15, 2015 at 15:56:41
HTA-Woofers
Audiophile

Posts: 1
Joined: March 15, 2015
 I owned a pair of Tenna Mind Blowers. I dissected one of my Tenna Mind Blower amplifiers to find out why I was measuring 25 Volts RMS across the speaker terminals with a Fluke 8060A True RMS DMM from a 12 Volt DC source. That calculated out to about 78 Watts RMS at 8 ohms with them cranked way up. They had a standard 8 ohm single voice coil speaker. The speaker leads were connected at points 45c and 46c in the posted schematic drawing. The center tapped winding that you see in the output section of the drawing is the output transformer and not the speaker VC as some have concluded here. They do not show the speaker being connected to it in the schematic.

The way this transformer was wound is that they wound two wires (14a & 14b) parallel (side by side next to each other)72 turns. They connected the inner winding end of one wire to the outer winding end of the other wire for the center tap (CL3) The two remaining free ends were each connected to an emitter of the two output transistors as you see in the schematic drawing at connection points 45c and 46c at which connection points each of the speaker leads were also connected to.

Instead of the Darlington transistors shown in the schematic posted here, mine had two small signal transistors that fed each of the 220 case output transistors.

If you would like to experiment with this type of amplifier design, instead of winding it at 72 turns with 18 AWG magnet wire, you could double or triple the number of turns for higher voltage output and wind it with 14 AWG magnet wire or larger for higher current output. You will need to increase the current capabilities and numbers of the output transistors used for the lower impedance loads of today's car audio speakers.

 

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