biamping with tubes and SS

[steelie]

Hi all. I'm currently driving my RF7s with a McIntosh MC202 and I'm pretty happy with the sound that I'm getting but I'd still like to try to round it out a little more on the top end.

I've recently been thinking about biamping the 7s and powering the horns with an MC275, with its 75 watts of tube power. I'd still want the MC 202 and its 200 watts of SS power to drive the woofers to give me the kciking bass I love.

Is anyone doing anything similar and if so, what kind of results are you getting? Also, will the disparity in wattage create any issues I need to be aware of and if so, how can I address them? Finally, would it be worth doing this if I only passively biamped the 7s or do I need to go full bore and get an external crossover to make this work?

Thanks for all the help.

[TBrennan]

I've bi-amped with SS on basshorns and various tube amps on the compression drivers, it worked well. Used both active and passive networks.

I'm talking real bi-amping; splitting the signal BEFORE the amps. Not "fool's bi-amping".

By the way, passive bi-amping describes the practice of using passive networks, rather than active ones, between the preamp and amps. Not the same thing as fools bi-amping at all.

I think your RFs use a passive EQ network in the compression driver crossover. If you bi-amp you must remove the passive crossover and then must compensate somehow for this EQ you've removed.

Bi-amping is best left to DIY enthusiasts and pro-sound people.

[steelie]

Thanks TBrennan. I don't have any listening experience with this sort of rig and I'm trying to understand the impact that the difference in output power will have. Is there any sort of balancing that you have to do or is that what you mean by compensating for the crossover that get removed?

[TBrennan]

Steelie---IMO bi-amping, real bi-amping (I hate to be a pest on the definition but the definition of biamping has been corrupted lately leading to confusion) by removing reactive components at the speaker level, leads to an increase in clarity and dynamics.

When using an active crossover one balances the woofer and tweeter by using the balance controls such devices have.

When one bi-amps using passive networks at the line (electronics) level one needs to use amps with output level controls or at least such an amp on the least efficient speaker section which is usually the woofer when using horns.

It's the nature of compression drivers, such as the horn on the RFs uses, to have an output power rolloff starting at 3-5khz. This rolloff must be compensated for to have flat frequency response on axis. I presume the RFs use a passive filter that flattens the mids to do this, I base this supposition on the fact that the earlier 2-way Epic line used such filters.

So when connecting the high-frequency amp directly to the driver, as one does when bi-amping, this filter is no longer there and the high frequncy driver will no longer have the response intended by the designer.

Thus to have the intended response one must retain the existing EQ circuit if possible, make a new circuit or use an outboard equalizer on the tweeter.

There's quite a bit to account for when bi-amping, at least when doing it right.