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IMO the best way to bi-amp and through experience is to have the integrated powering the HF's of your speakers and the power amp to power the LF's of the speakers.
I have tried the reverse but felt that as the tweeters are generally easier to drive; the power amps are best doing the hard end of the job and powering the mid/bass drivers.
Ive had a number of integrated and then integrated plus power amp systems and have always loved the added power amp more.
It doesnt make the music louder per say but what it does is opens up the soundstage a lot more; increases bass control and adds some depth; helps the midrange to be more open and smoother and gives the treble the additional crispness that is always a good thing
The reason I ask is because I have 685's too and was looking for the 130WPC RB-1070 but the whole 10 series has been dicontinued and replaced with the new 15 series. And the only 15 series amps available at the moments are the class D type which I'm sure are brilliant from what I've read so far on Rotels previous class D efforts, but I want to wait until the "regular" class A/B types are released so I can compare them directly.
The more traditional class A/B type 15 series power amps will be released sometime in the next few weeks (so an email I received from Rotel a couple of weeks ago says anyway) along with their new CD player, Pre amps, tuner and an integrated amp.
I know that when bridged into mono mode, the RB-1070 had something like 360WPC! Which to be honest is way excessive for a pair of 685's! Just one of them in stereo mode would be easily enough. I wouldn't think the cost could be justified either.
The new amps also have 2 sets of really hefty looking speaker terminal outputs on the back so you don't have to run bi-wire speaker cables in a 2 into 4 banana plug configuration. 4 plugs at each end with the new amps.
I'm really looking forward to getting my hands on one of the new amps and WHF also said they'll be reviewing them as soon as..
The tweeters are not as power hungry as the mid-woofers so by doing this you would just be giving them the quality power they need to get the best out of them. There wouldn't be any miss-match between the low and high frequency volumes at all.
Back to the original post and the hf/lf (vertical)or left/right (horizontal) question. I posed the same question in one of my first posts.
My thinking was to get a 2 channel left amp biamping the left speaker and the same for the right. That way I could get the amp closer to the speaker and use shorter speaker cable runs. It would also free up 2 slots on a crowded rack.
I thought I might get a secondary benefit in not overloading the bass amp in a more usual vertical biamp, as each amp is only running one heavy duty bass channel. I thought the current delivery would be better.
My reply from Andrew Everard was that using one amp for bass/mid and the other for treble is preferable. However the other route is perfectly valid too. He didn't go on to explain the reasoning.
So are there up to three options here assuming you have 2 x 2 channel amps:
- bi amp; one amp on tweeters, the other on mid/bass
- bi amp; one amp on left speaker (left channel on tweeter, right channel on mid/bass) and the other amp on right speaker. This may only be possible with a pre-amp and 4 mono blocks depending on the inputs/outputs available.
- bridge the amps so you have a more powerful amp on each channel; left and right. Obviously only an option if you can bridge the amps.
Dealing with the last one first, I once heard a setup which sounded very "loud". It was very "in yer face" compared to the non-bridged setup and would be very tiring for me. Each setup will be different of course.
The first option is the more favoured, since the delicacy of the higher frequencies won't get drowned or drained by the power hungry lower frequencies
However the second option may work very well depending on the design of the amp and connections available, if the power supply (which is now dealing only with half the mid/bass demand) can provide that extra big of power that's on tap without sacrificing the detail of the higher frequencies on the other channel. In practice I'm not sure what the connectivity would like if there's an integrated amp in the equation.
My advice would be to audition a bridged setup since I suspect you'll other love of hate the result. And then go with the hig/low frequency split but try both if at all possible and go with what you like the best.