Best way to distribute amplification?

[Sparky]

Hello All,
I made some recent changes to my system by going from a 5.1 system to 7.1 with the addition of 2 Polk TC80i surrounds and the purchase of another amp, Sherbourn 7/1250A. See my signature for a list of the major components.

My old configuration had the RTi150s bi-amped (200 x 2) from the 7/2100A along with the CSi40 and RTi38s each getting one channel from the 7/2100A.

The two subs (SVS 20-39 CS+) were driven by the Denon POA-2800 (200 x 2, 8 ohms, 350 x 2, 4 ohms) which may be taken out of service with the addition of the 7/1250A.

Here is what I am thinking of doing.
RTi150: bi-amp using one channel from 7/2100 and one channel from 7/1250
CSi40: one channel from 7/2100
SVS 20-39 CS+: bridge two channels for each sub (2) from the 7/2100
RTi38 and TC80i: one channel each from the 7/1250.

That leaves one channel from the 7/1250 left over.

Do you see any problems using one channel from the 7/2100 for the lows and one channel from the 7/1250 for the highs to bi-amp the RTi150s as opposed to using two channels from the 7/2100? Since the highs in the RTi150 are basically a RTi38 and it is rated for 20-150 wpc, I would think that 125 wpc from the 7/1250 would be plenty. Any possible gain, or other issues, from this configuration?

Can you think of a better way to distribute the power? I am open to all suggestions including keeping the Denon POA 2800 if needed.

Thanks for you time and expertise,
Sparky

[Tour2ma]

Sparky,

First, I see no reason to retire the Denon, but you can try setting up with and without it and draw your own conclusions.

I doubt there are significant differences in the response characteristics of the two Sherwood's so I see no issues with mixing them. As for how to best utilize them, I think that depends on how you are setting up your 7-ch's, i.e., large or small.

If for example you are running your 150's set to small crossed at 60 Hz to the sub, then the woofers are doing very little as they cross to the mid/high drivers at 85 Hz. In this case I'd be very tempted to run the 1250A to the woofers and the 2100A to the mid/ highs. If they're set to large, but LFE is sub only, I still might try the above set up. Again you can play and see what sounds best and how your amps like their assignments.

And that spare 1250A channel you thought you had... bi-amp your center.

[Sparky]

Hi Tour,
Thanks for the response.

One reason for replacing the Denon was to give the SVS subwoofers a little more oomph. I'm not sure they really need it but it's nice to know it's there if I do. With 2 channels bridged on the 2100A that would give each sub 400+ wpc (8 ohms) as opposed to 200 (8 ohms)/ 350 (4 ohms) with the Denon. How would you propose to use the Denon if I kept it in this system? As it is now, driving the subs? That would then leave me with 4 unused channels on the 2100A.

The mains (Rti150s) are set to large and LFE goes to both the SVS subs and the Rti150s. With the B&K Ref50 they call it their “Ultra” setting for the subwoofer. All other speakers set to small. This system is also used for 2 channel stereo so I’d like to keep the 2100A connected to the lows on the 150s. If the 150s were only used for HT and set to small I would definitely consider your suggestion to reverse the two amps but considering my setup I like the extra power going to the 150 lows instead of the highs for 2 channel.

My 1250A hasn’t arrived yet, should be here in a week or so. In the meantime I think I’ll give Sherbourn a call regarding the response characteristics to see what they have to say about it.

I thought about setting the center to "Large" and bi-amping it with the 2100A on the lows and the 1250A on the highs but was concerned about running too much power to it. Polk rates it at 250 wpc, this setup would be sending 325 wpc. Any concerns with that?

Thanks again for the help,
Sparky

[Tour2ma]

Glad to lend what assist I can...

I'd have no concerns bi-amping the center, even with it set to large. And you probably should set it to large, if that's how your mains are set. I certainly suggest that you try it both ways, just keep the LFE away from it.

On the Denon.. yes, I was thinking it should stay in its sub duty. The reason I'd keep the sub's off of the 2100A is it would be handed all of the bass duty, and while it's a stern amp, it might struggle. Again, you can try it both ways.

I know the above could leave a couple ch's unused, but it's hard to utilize 14 ch's fully. Obviously you could assign the 2100 the LF duty and the 1250 the HF in all 7 ch's, but I think most would agree that bi-amping the 4 surround ch's, at least to this degree, is overkill. One solution is to put left overs into 2 ch duty, if your space allows it.

As a general note...
Multiple sources of deep bass create added bass management issues. By issues I mean areas of the room where certain LF reinforces itself and nulls (reduces) itself. This always occurs due to room reflections, even with a single sub, but multiple radiators greatly increase the liklihood of this occurring.

If it sounds good to you... great. But if you were looking to tighten up/ even out the bass performance of your HT with the purchase of the 2100, then your set up may need some tinkering.