Bridge or Bi-Amp A23's

[boettinger]

I have read conflicting opinions on this. Would I be better off bridging 3- A23's for my front, left and center channels or Bi-Amping them. I do not have the capability of going with active crossovers at this time, although I understand this may ultimately be the best way to go. Bi-Amping using the passive crossovers in the speakers did not seem to make much difference, but since I have the 3 amps, I would like to put then to their best use.

My main listening is home theater and the rears are powered by an A52.

Thanks

[kfr01]

Bridge until you have the capability to try active crossovers out?

I think it depends on your speakers. Do you have 2-ways or 3-ways? Where are they currently crossed over?

[Peter Nielsen]

Well, if you need to do either one or the other, then I'd recommend passive biamping in favor of bridging, unless you really need the extra power that bridging gives you.

Passive biamping has the advantage that the low and highs are separated. Also, with passive biamping you're not putting any additional strain on the amps. The downside is that this two amp setup will not give you much more power than one single amp would give you and you'll need an additional pair of speaker cables.

Bridging has the advantage that you can actually use the doubled power that the second amp gives you. However, the downside is that this sometimes puts more strain on the amplifiers. Also note that bridging REQUIRES 8 ohm speakers. If you have 4 ohm speakers bridging may not be an option.

FYI: If you can remove the passive crossovers from the speakers, then you could do active biamping with a cheap crossover for as little as $90. (Get a cheap PA crossover to start with, and then later upgrade to something better like a $500 Marchand).

Peter

[boettinger]

Thanks, I really don't think I need the extra power (but you can never have enough). The speakers are 3-way Kef's.

I have extra cables so I guess I could try it both ways.

I guess the question I have is, based on the amps and speakers I have now without spending a bunch more money, which way would you guys go?

Thanks again

[boettinger]

Oh and by the way the speakers are 8 ohm so no problem there.

[kfr01]

boett:

I would actively bi-amp since they are 3-ways. This will delegate only the bass duties to one amp, and the mids -and- highs to another amp. This type of split is ideal for actively bi-amping. With most music the "halfway" power point is 350hz. i.e., half of the used power is due to frequencies below 350hz and half above. Actively bi-amping has many benefits over passively bi-amping.

Primarily, in passive bi-amping the highs and lows are -not- split up at the amplifier stage. If you're clipping your signal to the amplifiers, you'll still be sending the clipped signal to the highs and lows. Active bi-amping separates the highs and lows prior to the amplifier stage. So, you may clip the bass amps (probable at very high volume levels) while the amps playing the mids and highs can continue to play unclipped. This is advantageous both for your ears and your high frequency drivers.

Learn more here:

http://sound.westhost.com/bi-amp.htm

I wouldn't bother bridging unless you're running out of headroom / power.

It isn't universally accepted that passive bi-amping is audibly helpful. Do it for now until you can afford active crossovers. Or sell two of your A23s, buy an A21, and bridge the extra A23 to your center.

[boettinger]

Thanks for all the info. There is one thing that I can't understand and maybe you experts can help.

If bridging doubles the output power of an A23 to say for arguement purposes 250W, why is this not as good as say an A21 at 250W?

And what about bridging the center channel? I see a lot of recommendations for doing this. So if it's good for the center why not the two front channels?

I'm sure there are good reasons, but my inquiring mind wants to know.

Can anyone explain this for me?

[Peter Nielsen]

If bridging doubles the output power of an A23 to say for arguement purposes 250W, why is this not as good as say an A21 at 250W?

When you're connecting an 8 ohm load to your bridged A23, the two channels will effectively run as 4 ohms each. (This is why you cannot connect a 4 ohm load when bridging - each channel would run with 2 ohms only and the Parasound amps are not designed for this).

The 4 ohm impedance means that the amplifier is more heavily loaded than it would be with an 8 ohm speaker. If your 8 ohm speaker is a "difficult" speaker with an impedance that at times dips very low, this may pose big problems for the A23 that is already running at minimum impedance. However, for a non-bridged A21 this would be no problem since even if the impedance dips down by half, the A21 will handle it without any problems...

The A21 has a lot more power reserves than the A23. Just look at the size difference of the transformers and the difference in power supply capacitance (100mF vs 48mF). A bridged A23 will run out of juice much more easily than the A21. You might argue that since you're using two A23s, the capacity will be the same. While this is true in a laboratory experiment where equal power is applied to both channels, it is far from true in reality where the music signal varies greatly and one channel often needs more power than the other in a specific point of times (talking milliseconds here).

Oh, BTW, bridging of course doubles the 4 ohm power, not the 8 ohm power. The A23 is 2x200W @ 4 ohm stereo or 400W @ 8 ohm in bridged mode.

Peter

[Petergman]

Regarding your ps audio link III

HI Karl,

I noticed you were using the new link III and wondered how you would describe it in comparison with other dacs or players. I am interested in this product and might audtion. There is surprisingly little info about it.

Peter

[Chris D]

Hey, Petergman, I see it's your first post, so welcome to the Guide and Club Parasound! :banana:

If you have a general audio question, it may fit best in other parts of our subforums here, instead of our Parasound specific club here.

[locomk]

i have two a23's and a a21. i called richard the ceo of parasound and he advised me to use my a21 for my fronts, because even though it has less total wattage per channel than a a23 will have if it's bridged, the a21 has a lot more currant and as peter has mentioned above, has more reserves. also by bridging, the a23 will have twice the thd.

i decided to bridge my a23 for my center channel and use my other a23 for my rears. which i then eqaulized the levels in my pre/pro menu's settings.