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3 Pi subs paralleled from plate amp [message #70998] Sat, 14 January 2012 13:22 Go to next message
skywave-rider is currently offline  skywave-rider
Messages: 104
Registered: May 2009
Viscount
Wayne,
I am considering building a pair of 3 Pi subs to flank mains. I would like to put a plate amp in one, and parallel the amp out to the other sub.


These are the amps I would consider:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-750
or:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-752&FTR=bash%20500

Some might say it's not a lot of power, but this would be for portable hi fi use and not a high SPL application.

What do you think about the impedance load?

Re: 3 Pi subs paralleled from plate amp [message #71001 is a reply to message #70998] Sat, 14 January 2012 14:59 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18787
Registered: January 2001
Illuminati (33rd Degree)

I think it's probably a bit too much load to parallel them. That would put the impedance down at around 2Ω. I would run one plate amp on each speaker, bolt one on the back of each. Run the right signal to the right flanking sub, the left signal to the left.

If you run a more distant sub or two, summing the signal is fine but flanking subs are better when driven with a low-passed version of the signal sent to the mains they're flanking. They are run a little bit high, after all, just barely reaching into the lower midrange. That's why I like to use a second-order filter too, so the blending is gradually reduced, starting around 100Hz. With a gentle slope, there is still a fair amount of energy in the 100Hz to 200Hz octave, enough to smooth the modes in that region. That's really the point of the flanking sub approach.

Here's another plate amp that might be worth considering:
Re: 3 Pi subs paralleled from plate amp [message #71002 is a reply to message #70998] Sat, 14 January 2012 15:41 Go to previous message
skywave-rider is currently offline  skywave-rider
Messages: 104
Registered: May 2009
Viscount
Thanks, Wayne. In this case I might look into a used stereo power amp as I have an active rackmount low pass if needed. But the plate amps are more convenient.
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