Axiom Home Page Forums General Discussion Home Theater Integra receiver advice: bi amp or "bridge" mains?

I am considering the new DTR 9.9 receiver. As with past high-end Integra and Onkyo receivers, one can use the 6th and 7th channels to bi-amp the LF and RF speakers (that I understand; common feature these days). Alternatively on these Integra/Onkyo units, one can opt to bridge ("BTL") the mains, sending 230 watts to the speakers. According to the manual:
The FRONT L/R and SURR BACK L/R terminal posts
can be used with front speakers and surround back
speakers respectively, or bridged together to provide
almost double the output power for the front speakers.
• When bridging is used, the AV receiver is able to drive
up to 5.1 speakers in the main room.
• For bridging, the positive (+) FRONT L/R and SURR
BACK L/R terminal posts are used, but the negative
(–) FRONT L/R and SURR BACK L/R terminals are
not.
• Once you’ve completed the bridging connections
shown below and turned on the AV receiver, you must
set the Speaker Type setting to BTL to enable bridging
(see page 57).
Does anyone know anything about this connection scheme? Thank you.

Bridging at least sounds like it might have more tangible benefits than bi-amping.

Blu, the so-called "bi-amping" feature that some receivers advertise has been discussed here several times in the past year. It isn't bi-amping and should be disregarded since it can't double the power available to a speaker, as some imagine, or increase it in any amount. The unused back channels have no power of their own to lend; they're simply acting as valves in metering out the same amount of power from the receiver's one main power supply section.

Bridging is entirely different and is a valid procedure, although it might be unnecessary if the regular connections already supply more maximum power capacity than needed, as is typically the case. This works by inverting the voltage that one channel outputs and then sending both it and the normal voltage from another channel(both channels being fed the same audio signals)into the positive and negative speaker terminals. In effect the positive voltage "pushes" while the inverted negative voltage "pulls" in the same direction, co-operating in driving the speaker cone rather than cancelling each other in the driver, which would happen if both were of the same polarity.

The double voltage input theoretically would increase power four times(not double)since in one form of Ohm's Law power is proportionate to the square of the voltage(P=E[squared]/R). In practice the process doesn't work with theoretical efficiency and the typical power increase is no more than about three times.

One possible difficulty that might arise is that with the receiver having to put double the voltage into a speaker, the current would also have to nominally double(Ohm's Law again, I=E/R)with the speaker impedance of course remaining constant(the receiver doesn't "see" half the impedance, as is sometimes written). This would increase the possibility of overheating and protective shut-down.

I have always wondered, What do you do for a living JohnK?

Thanks for taking the time to provide that explanation.

David, it's been on the board a couple times after previous requests, but here again is my brief bio: Attorney(criminal prosecution, estate planning, investments, taxation); J.D. University of Michigan, undergraduate degree B.S. in Chemistry.

Cool, You are very well spoken and full of knowledge! It's good to have someone like you on the boards!

Amen

Yet still... no one calls him Mr. Fancy Pants.

I really think that shoulda caught on.....

JohnK, just on the off chance you are really super famous, I have to ask...

About 2 weeks ago (give or take), there was an oft discussed editorial in the Financial Times by someone dubbed simply "John K." Any remote chance you use the same moniker when writing in the world's leading financial publications?

Jason