Need help from smart people - biamping

Hi Nil,

In a passive biamp arrangement employing identical amplifiers, whether vertically or horizontally, any given frequency component of the input signal to the amplifiers will be subject to essentially the same gain as if only one of those amplifiers was being used full-range. Therefore there will be essentially no difference in the volume control settings that are used in the biamp and single-amp configurations. (I say "essentially" because there are some subtle effects that might result in extremely small differences, such as the very slight volume loss that can result from splitting the preamp's output signals, depending on the impedances that are involved).

MAXIMUM volume capability, before clipping occurs, may increase SLIGHTLY in the passive biamp configuration, to the extent that the output voltage swing capability of the amplifiers increases as a result of the fact that each amp would no longer have to supply current and power across the full frequency range. Or (less commonly) if the maximum volume capability of the particular combination of amp and speaker is limited by the current capability of the amp, rather than by voltage swing.

The main benefit, if any, would be with respect to sound quality.

Best regards,
-- Al

Hi Al,

Thanks that is exactly my thinking was. My preamp does have 'designed in' two sets of outputs (a balanced set and single ended set- I currently use only set of balanced at present). Not sure what that means to volume loss since both will pre-amplify the full signal still. Hopefully not much volume loss.

I was thinking that max volume capability increase, before clipping occurs, now would be close to 3db. Aren't we 'doubling' (than what it was) the power essentially to both m/t and l freq drivers? No? That is my primary goal. I am happy with the sound quality and overall tonal balance right now with one mono block pair.

In any case I would audition before buying an extra pair of amps but still there is shipping, extra pairs of same quality cabling, same tubes etc involved.

You do give enough technical info and reasoning for me to think about. Thanks!

I was thinking that max volume capability increase, before clipping occurs, now would be close to 3db. Aren't we 'doubling' (than what it was) the power essentially to both m/t and l freq drivers? No? That is my primary goal. I am happy with the sound quality and overall tonal balance right now with one mono block pair.

Not necessarily. Since in a passive biamp configuration the amplifier channels driving the low frequency and the mid/hi frequency sections of the speaker will BOTH have to output a voltage range corresponding to the full frequency range of the signal, there may be very little increase in the total power capability. As I indicated earlier, in the single-amp situation if power capability is limited by the voltage range that can be output, passive biamping will only result in a power increase to the extent that the voltage range capability increases as a result of the reduction in the amount of current that each amp channel has to supply (the low frequency amp will not be supplying current at high frequencies, and vice versa). How much that voltage range increase will be depends on the particular amplifier, and may be correlated to some degree with the dynamic headroom of the particular design.

My preamp does have 'designed in' two sets of outputs (a balanced set and single ended set- I currently use only set of balanced at present). Not sure what that means to volume loss since both will pre-amplify the full signal still. Hopefully not much volume loss.

It would probably be best to use a balanced y-adapter to split the signals. Using the balanced output for one amp channel and the single-ended output for the other would probably introduce a gain mismatch. Also, some designs may not intend for both outputs to be used simultaneously, and the single-ended output might be the same signal as one of the two signals in the balanced pair (probably the non-inverted signal on XLR pin 2). In that situation using both sets of outputs would, to at least a small degree, unbalance the balanced signal pair, and nullify some of the advantages of a balanced interface.

Some inexpensive XLR y-adapters can be found here.

The volume loss resulting from splitting the signal will be negligible (less than 1 db) as long as the parallel combination of the two amplifier input impedances remains at least a factor of 10 higher than the output impedance of the preamp, at the frequency for which preamp output impedance is highest. Which is a necessity anyway, to avoid compromising sound quality.

Best regards,
-- Al

Thanks Al.

I do now understand the vol increase potential, which is to say slightly not to extent (3db) I was thinking. Dynamic headroom will most likely increase (==>better sound quality)

I meant to say that my preamp has 'designed in' TWO pairs of balanced and TWO pairs of single ended outputs for specifically this reason (biamping) So I suspect the output signal is already Y-split internally for each pair 'sets'. BTW, I just got A response back from my amplifier designer/rep (Zanden) and they also sort of said expected results in line with what you said.
Overall sound quality= better, SPL increase potential = slight.

I really appreciate your insight.