There are two ways to ‘Bi-amp’: An ‘Active’ system, or a ‘Passive’ system. Here we will concentrate on ‘Passive Bi-Amping’, which avoids introducing active components (such as an electronic crossover with filters) into the signal path upstream of the amplifiers, using instead the speakers own crossover.
Royd speakers employ 1st order crossovers, the simplest and least musically intrusive type of crossover. Anecdotally it is speakers with this type of crossover that respond best to Passive Bi-Amping. To Bi-Amp you need speakers with 2 pairs of binding posts on each speaker. On older models with just one pair of binding posts, a simple modification can be performed to separate the bass from the treble in the crossover & add a second set of posts. An alternative to this permanent modification is to run flying leads from the separated crossover out of the rear of the speaker (perhaps through a port) to connect to the second set of speaker cables from the second amplifier. Many skilled DIYers can be found on HiFi forums that can advise, or perhaps even perform such a modification.
Most recent speakers have 2 sets of binding posts, including the Royd Revelation range & the Merlin. It is vitally important to check & ensure any internal wire links that join the top set of binding posts to the bottom ones are removed. These links enable the speakers to be used as standard, in a single wired configuration, which is incompatible with Bi-Amping. (When I bought my second hand RR3s one had these links removed & the other did not!).
You can Bi-Amp vertically or horizontally: Assuming 2-way speakers are used, vertical is a matching mono amplifier on each speaker, often called ‘monoblock’ amplifiers. Horizontal Bi-Amping results in greater gains, and refers to a stereo amplifier driving the treble on both speakers independently, while another amplifier (with matching output gain but possibly a higher RMS Wattage) drives the bass on both speakers. (Tri Amping utilizes a third amplifier with 3-way speakers).
By horizontal Bi-Amping you are driving the treble of both speakers with one stereo amplifier and the bass with another. If you now incorporate monoblocks into the setup – that equates to one driver per amplifier! Now that is a lot of amplifiers, but Bi-Amping achieves results that are greater than the sum of its parts. You can expect a greater dynamic range and more clearly discernible detail in the music, contributing to a startling stereo image and a real sense of being there with the musicians. Be aware though – you’d better like your source as Bi-Amping results in an extremely revealing system.
Why is Bi-Amping effective? It has been suggested that ‘reaction’ from speaker drivers as they reverse their direction of travel is sent back to the amplifier as load, interfering with the amplifier’s ability to communicate the next part of the musical signal to the speaker. Therefore in a Bi-Amp setup each amp is free to transmit its signal to its own driver without having to deal with the ‘reaction’ of other drivers at different times. Consequently a cleaner, more detailed signal is sent to each individual driver, which can result in a wonderfully communicative setup.
Please try to remember that Passive Bi-Amping results seem to vary, but when successful it is greater than the sum of its parts. The paragraph above is just a theory; you must try it for yourself to really know what is being discussed here. Much useful advice can be found on forums like Pink Fish Media.
– Alan Brown
(edited by Arthur Yarwood)
SoundStage! – Synergizing with Greg Weaver, March 1998