Axiom Home Page Forums General Discussion Technical Questions Bridge or Bi-amping experience ?

Hey there, just looking for some advice, I am stepping up from a Integra dtr 5.3 @ 80 wts per ch to an onkyo tx-nr5007 @ 145 per ch This receiver allows me to bridge or bi-amp my two mains instead of surround rears, which I do not curently use anyway. Should I BI-amp the speakers or bridge the channel for double power? The main reason for the upgrade I really wanted more power for 2 channel stereo music as well as hdmi switching. O and BTW..I am using 2x m60v2 1x vp150 2x qs8 1x ep350 and plan to add a second ep350 very soon.. any help or advice would be great

You will not hear any audible difference in doing the passive bi-amping.

Thanks Rick ..So I take it I'll bridge 2 channels for for what I want, and if so, will the fronts be way too loud when I switch to 5.2 surround for movies. Or do you know if the auto surround setup will adjust for that? I'll be setting this up tomorrow and would like to have a game plan so I only have to do this behind the rack wiring this 50 pound thing once..lol Thanks again!

If I were you I would stick with standard wiring. Even if you do the bi-amping, it wouldn't be bridging, you will be fine once the unit is calibrated.

ok...I'll try it like that ..but do you think that 145 per ch will be lots for "really wicked" 2 channel stereo as appossed to the 290 I counld get by bridgeing the 2 back channels..thanks again I apreciate your imput..Paul

OK, ya see, even if you did do the bi-ampimg you would still only be getting 145 watts (max) per channel. Removing the straps from the rear of the speaker only changes the route in which the power is received from amps. The top would get 145 and the bottom would get 145. With the straps in place and running one speaker wire the top and bottom still get 145. It does not change the total watts received.

Ok but Im actually talking about bridging feature of the reciever, according to the manual it will actually push double the wattage to the front main speakers by bridgeing the front right and rear right channel and same to the left channel and leave the straps on the speakers. Thanks again!

Even though that is what the receiver manual says, it is misleading. Your not getting double the power.

Reading through the manual it does indicate bridging will almost double the power. I haven't seen the impedance chart on the M60s and if they dip low enough it could present problems in BTL mode.

I sure enough know one thing, my Onkyo runs pretty hot even running 8 ohm speakers. Running in BTL mode is going generate a lot of heat in the amp if it truly does real bridging..

I bridge my 2 side M80's with my Denon amp with no heat issues. My 2 front M*'s are run along with my VP150 with the A1400-8. When running Audyssey the speakers are calibrated very close in their adjustments. Take that info however you like

Paul, welcome. As other replies have indicated, the so-called "bi-amping" feature that some receivers advertise isn't real bi-amping and is essentially meaningless. It simply sends the same amount of power from the the one main power supply section of the receiver to the speaker through two sets of output transistors(one set previously unused for the back surrounds)rather than one. This can't double the maximum power available(as some imagine)or increase it by any amount.

Bridging is an entirely different process. It sends two voltage inputs into the one set of speaker terminals. The reason that the two don't collide in the speaker driver and neutralize each other is that one voltage is reversed in polarity so that it "pulls" while the other "pushes" and the two co-operate to power the driver. Theoretically the double voltage could result in a maximum quadrupling of the power since when the voltage is doubled into the same resistance the current is also doubled(Ohm's Law). This doesn't happen in reality and the best that can be achieved is about a tripling of the maximum power. Incidentally, it can be pointed out that the amplifier doesn't "see" a lower impedance when it's bridged, as is sometimes said. The impedance of a speaker is set by its wiring and the amplifier can't change this. The higher current in bridging is due to the higher voltage into the same impedance.

So, if you actually need more maximum power, bridging could be tried; however it seems highly unlikely that your 5007 wouldn't supply more than enough power already, unless you care to operate at sound levels that permanently damage your hearing.

and doubling the watts will only gain you 3dB's.

Last year I emailed Alan to ask about M80's, bi-amping, and impedance, as part of the whole Emotiva vs. Axiom impedance debacle. My question was actually featured in the April 2009 issue of Axiom's Audiofile newsletter.

Ian answered in that newsletter,

"The x-over in a speaker keeps the impedance of a multi-driver system from being averaged down over the various driver impedances. Bi-amping simply separates some of the frequencies from others but does not necessarily change the impedance load. It will have some effect and depending on the speaker can change it from a 4-ohm load to an 8-ohm load but that would be rare. In an M80, it does raise the impedance of each separate channel but not enough to take it out of the 4-ohm category."

So to Bi-amp, one must remove the bridge plates. And removing the bridge plates alters the 'system'. That, according to Ian if I'm reading his response correctly, raises the impedance 'seen' by the amp. In an M80, at least. Therefore, bi-amping can and does change an M80's impedance. Not the act itself, but the setup *for* bi-amping.

Of course, the OP is talking about an M60, so I have no idea whether that applies. I'd be surprised if it didn't, however. The best source would be to email Alan directly, as he'll know.

My M80's are 'pseudo' bi-amped with my Emotiva LPA-1. I've tried it both ways, but prefer it bi-amped. Just sounds better to me. I will not debate that it is possibly, likely, or definitely just a psycho-acoustic effect, all in my head. That's all the enjoyment of music is anyway.

My advice is to try it both ways. If it's a 'free' feature of your AVR, and you've got the channels open anyway, your only expense in trying is the extra speaker wire and the time it takes to hook it up. It'll either sound better, exactly the same, or worse. Listen to your system in your room on your gear
and decide for yourself.

Good luck.

I called and talked to Brent about this very issue and he told me it did not change the impedance of the M80s.

I have mine passively bi-amped and can't say I hear a huge difference. Then again I didn't do proper blind testing either

I'll bring a blind fold over this weekend, lol...

What exactly were you looking to do with that blind fold Randy

not me, the dancer I'm going to pick up on the way over, hope your wifey will be gone, lol.

Peter, note that the quoted language relates to bridging, not bi-amping.

I bi-amped by M80v2 speakers using a Denon AVR-3805 a few years ago and noticed no significant improvement in sound quality. I ended up buying some new but discontinued QSC SRA 3622 two channel amps that provide 1100 watts/ch at 4ohms. I am HAPPY with the sound quality and volume of these amps! The M80s really opened up with these powerful amps. I do have a very large family/living room area, so the additional power did help with playing music at very high levels.

Rock on Richie.

Thanks sirquack!