[bdp24]

Danny, what will the increase in output be when a third GR12-16 is added to the usual two in a pair of H-Frame OB subs? Have you built a pair of three-driver H-Frame subs, or heard a pair built by someone else? Do you consider the increase in output justifies the $400 it takes to add the third pair of drivers? They would be mated to a very output-challenged pair of ESL's set-up in a 10' X 13' X 19' room, playing mostly acoustic music at room filling volume.

[HT cOz]

I'm not sure if adding a third will increase the output but will decrease the distortion. The reason I say that is that it seems like the servo ensures linear output to the lowest level. So adding another driver let's the other drivers achieve the same output but with less movement.

[emailtim]

It also lowers the combined parallel impedance from 8 Ohms to 5.3 Ohms that the plate amp will see.

[bdp24]

It also lowers the combined parallel impedance from 8 Ohms to 5.3 Ohms that the plate amp will see.

I'm not sure if adding a third will increase the output but will decrease the distortion. The reason I say that is that it seems like the servo ensures linear output to the lowest level. So adding another driver let's the other drivers achieve the same output but with less movement.

Right, both good reasons for adding a third driver. Better reasons, infact, than to increase output. Both the amp and the other two drivers working less hard, decreasing the chance of clipping the amp or reaching those driver's maximum output. Thanks for reminding me, youse guys.

[Danny Richie]

Actually the DCR will drop from 7 to 4.6. So the amp will produce more power to that load. Combined with a third woofer it will kick out 1/3rd more output.

And yes, for the same output each woofer will be working less compared to running them in pairs. And the less the move the faster they stop.

[Hank]

Hmmm...food for thought.  Draw us a cab configuration, please.

[emailtim]

Actually the DCR will drop from 7 to 4.6. ...

Danny,

Does this mean the drivers are actually 14 Ohm, (not 16) ???

Using the following calculator, 14 Ohms yield the numbers you stated.

Thanks,
Tim

http://www.bcae1.com/spkrmlti.htm

[Danny Richie]

Danny,

Does this mean the drivers are actually 14 Ohm, (not 16) ???

Using the following calculator, 14 Ohms yield the numbers you stated.

Thanks,
Tim

http://www.bcae1.com/spkrmlti.htm

14 ohms is the DCR. So it is the minimum impedance dip.

[emailtim]

Danny, what will the increase in output be when a third GR12-16 is added to the usual two in a pair of H-Frame OB subs? Have you built a pair of three-driver H-Frame subs, or heard a pair built by someone else? Do you consider the increase in output justifies the $400 it takes to add the third pair of drivers? They would be mated to a very output-challenged pair of ESL's set-up in a 10' X 13' X 19' room, playing mostly acoustic music at room filling volume.

Here is one thread (which appears to be a good tutorial on what not to do and what you should do):

http://www.audiocircle.com/index.php?topic=56491.0

There is another thread where a guy made nice CAD drawings for the 3-Driver W-Frame, but I didn't see that he actually made the physical cabinet.  If I find the thread, I will post it.

[bdp24]

Hmmm...food for thought.  Draw us a cab configuration, please.

I would put three in an extended H, aligned vertically, the top and bottom drivers facing the LP, the middle one the opposite direction.

[bdp24]

Here is one thread (which appears to be a good tutorial on what not to do and what you should do):

http://www.audiocircle.com/index.php?topic=56491.0

There is another thread where a guy made nice CAD drawings for the 3-Driver W-Frame, but I didn't see that he actually made the physical cabinet.  If I find the thread, I will post it.

Yeah, I saw that 3-driver W-Frame. That's one reason I would do it in an H An H-Frame makes for a much stronger structure, plus it appeals to me aesthetically. You have to give up the 90 degree opposing-force cancellation benefit of the W, though.