Mixed Bi-Amping RTi-A9s w/ Adcom 555 + Onkyo TX-NR5007

Squishy Tia

OK, I just got an Onkyo TX-NR5007 as a tax refund gift to myself (I used tax money and Christmas money), and currently have my A9s bi-amped using the Front A and Surround Back channels. I only even bothered with this because this particular AVR has two power supplies available for the amplifier section; one for surrounds/center and one huge toroidal transformer + 22,000µF capacitor combo for the mains, resulting in a pretty much guaranteed 145w/channel to each of the A9's two arrays (caveat: mechanical and heat energy dissipation from unused frequencies in each array reduce the power throughput, which obviously is why most will tell you/me to bi-amp using an external active crossover).

Anywho, this amp has pre-outs for all channels, and I'm wondering two things:

1) Can I bi-amp using the Onkyo to power the upper arrays (mid/high) on the A9s while using the Adcom 555 MkII to power the lower arrays via the pre-outs...

and

2) If #1 can be done safely, will the Audyssey MultiEQ setup still be able to adjust the low level output frequencies properly?

The massive power supply inside the Onkyo is such a nice thing to have to waste, especially since it has some decent capacitor backup as well. Not as much as the Adcom I have can muster (the Adcom can play my A9s at full volume for a full 10 seconds after being turned off!), but still a significant amount for a home audio amplifier.

I'd love to be able to use the Onkyo to power my A9s' upper array while letting the Adcom deliver a nice 200w/channel into the bass arrays. Oh man would that ever be sweet (and a money saver for me, considering I just bought such a wonderfully featured beast).

mjcmt

Bi-amping using a surround receiver is only possible if you can designate what surround info goes to what channel outputs, otherwise you are sending front and rear surround info to 1 pair of speakers. Part of the info is going to the highs and part of the info to the lows, instead of each speaker handling its correct sound info.

As far as bi-amping using different amps it is only possible if both pair of outputs from your pre outs are sending the exact same to one set of speakers (front R&L info at both pre outs) for the same reasons.

Secondly, bi-amping is best achieved vertically w/ one same amp per channel instead of one amp for highs and one amp for lows. The reason for the benefit is that each amps power supply handle highs and lows of one speaker only. Highs don't tax a power supply like bass does, therefore making an easier load on the amp's PS yielding more dynamic and clearer sound. (The only exception is an amp that is a true dual mono amp w/ a seperate PS for each channel, which yours doesn't have.)

You are talking about doing horizontal bi-amping w/ one amp for the lows and one for the highs. The amp that handles the lows gains little from the benefit because the lows tax the PS heavily while the highs don't, so the amp on the lows doesn't benefit for it. The exception is to use a robust SS amp for lows and a tube amp for the highs to sweeten the sound. If you choose to try horizontal bi-amping use the more powerful amp for the lows.

I hope you understand my reply. Good luck!

Squishy Tia

I understand your reply, and do appreciate it (always good to get input!). So what your'e saying is that in my case, using two identical Adcom GFA-555 MKIIs, I should just use a Y-Splitter on each Pre-Out (L and R) to each respective amp, and have only one amp per speaker, using say the left input for lows and right input for highs on each amp, yes?

I'm not sure how much going vertical will make a difference from going horizontal, since I'm using two stereo (two channel) amps that are going to give the same amount of power per channel, regardless of how I set it up. But it's easy as pie to check it out both ways, thanks to banana plugs being amazingly simple to move.

Squishy Tia

Scratch that last post. I did a bit more research and found that a) the MKIIs aren't exactly great for bridging, and b) unless the speakers must have common ground, it's better for me to do as you suggested to both separate the channels completely and eliminate potential crosstalk.

So when my other 555 MKII arrives on Wed, I'm gonna go vertical. I won't get as dramatic an increase in clarity as I would going EXO -> Preamp -> Bi-Amp, but it'll still have more headroom and a wider soundstage than one amp running both speakers.

I just need two Y-Splitters and a single pair of RCA cables. Thankfully both are fairly cheap.

Squishy Tia

Whoa! You were definitely right about going vertical. I didn't bother with horizontal, and went straight into vertical alignment and holy sweet mother of all...wow. I expected a slight improvement in channel separation (I got a major one, which means the Adcoms had definite crosstalk going on), but what I didn't expect was to hear things in my upper array that I typically only hear in really good studio monitor headphones. My tweeters seem like they've come alive like never before, and all I was hoping for was more punch on the bass.

I guess having only one speaker on an amp makes a pretty big difference in how well the amp's circuitry can control speaker response. NOW I almost don't need a sub. I'll have to try out the configuration at reference levels tomorrow when my grandparents are gone (so as not to make their teeth rattle out of their mouths).

This setup beats the living crap out of any $2000 Onkyo anyday. Now I can use the money I saved to get myself the Battlestar Galactica BD set. Or maybe a new audio system for my soccer mom minivan. :P