Passive bi-amping works ?

ryllau, there are many pre's that have more than one set of main output connectors. but, i woodn't necesarily use this as the criteria for choosing a preamp. there are quality adaptors that allow ewe to connect a pair of i/c's to one output. even tho my pre has *three* outputs, i still have to use adaptors, because i use an active x-over which has only one set of hi-pass outputs. i run a pair of amps from my hi-pass outs to wertically bi-amp my monitors.

but, when bi-amping, ewe *do* have to be even more aware of impedance mismatches - adding a second amp to yer pre effectively lowers the input impedence the pre is seeing. for example, if ewe are using two amps rated at 20k-ohms input impedence, the preamp will *see* a 10 k-ohm impedence. and, longer i/c's, which can be attractive in a wertically bi-amped set-up, to reduce the length of the speaker cable, can further exacerbate any impedance mismatches. basic rule of thumb is that yer amps' input impedance needs to be *at least* ten times greater than the output impedance of the preamp, & in some instances, even this amount may not be enuff.

hope this helps, doug s.

It only makes a difference, if you use different amps. If the amps are not underpowered, then two should sound essentially the same. If power was the issue, then significant gains can be had. I passively bi-amp, but with tubes on top, solid state on bottom.

fletch, my experience differs from yours - one of my electrocompaniet amps is enuff power to drive my monitors, but it sounds better w/a second matching amp, using one amp per monitor, vertically bi-amped.

ymmv, doug s.

I have a pair of Legacy Classics I am driving with a Sunfire Cinema. I have tried driving them with single channels then biwiring and then passive bi-amping and there was a steady improvement in the sound. More highs and lows with each change and better clarity and definition. A rather interesting thing, which I can't explain is that the speakers response got much flatter when I went to vertical biamping (as confirmed by my SPL meter). I had a +3 to +5 dB boost over much of the bass range and after the vertical biamp, it's now +-1.5 dB down to 40 Hz. Now I'm just waiting for the funds to go with Active crossovers...

Gpalmer-
(Someone with an EE can say this better than I, but bear with me.) When you passively biamp you are removing the crossover elements of the high and low pass sections of the speaker from each other. Because there is no series or parallel interaction between these elements, the impedance variations with frequency the amp sees are gentler (and the lower amp is not forced to put high current into the high frequencies.) The frequency response improvement is probably due to the smaller impedance slope,phase angle, and possible higher overall impedance from the bass to the mid range and from mid range to highs when you biamp compared to it run as a single speaker. This slope/phase angle causes frequency response/tonal interaction with the amps. As the slope approaches zero (ala a classic 8 ohm resistor)there is less frequency reponse interaction, all other things being equal, (eg see the Stereophile tests of many tube amps to see such a plot.) Bravo on your disciplined investigation and sharing of information that truly benefits this discussion.