Have a few questions about bi-amping..


I have a question. But, it takes some explaining...
Ok, I will be upgrading my speakers early next year. A friend is selling me his pristine Devore Fidelity Orangutan O/96 loudspeakers when he gets their new version of these as soon as they are released.
I currently use a Supratek Chenin line stage tube preamp with a solid state Cary Audio SA-200.2 power amp. These drive two KEF R700 loudspeakers. Now, I know the Devore Orangutans are far more sensitive than the KEF's (97 dB vs 89 dB). So, knowing this monster power amp will be even more unnecessary than it currently is (I didn't get this because of the power, I got it because I have always loved it's performance/musicality), I have recently purchased a pair of Cary 300 SE tube monoblock power amplifiers. I'm very excited about pairing these low wattage SET type amps with the Orangutans. The 10 watts per channel will be plenty to drive those sensitive speakers.
However, I would love to be able to start using them as soon as they arrive (this Thursday). But, obviously worry that they won't be able to drive the less sensitive KEF's for the next six months.
So, I know I will have to wait and see how they sound, but, has anyone had any experience with bi-amping these speakers? I am thinking of bi-amping with the Cary SA 200.2 for the lows and the tube monoblocks for the mids/highs. Will I need an external crossover to balance the difference in gain between the two amps? Or will the passive crossover within the speakers work fine? Anyone?
Thanks.
128x128Ag insider logo xs@2xjvancamp78
Hey Al,

Thank you so much for all of this extremely valuable info! It clears up a lot of the specifics I was unsure about. Huge help!

jared
For reasons explained below I would rule out a passive biamp arrangement in this situation, and it seems to me that there would be significant downsides even if you were to biamp using an external electronic crossover.


First, per John Atkinson’s measurements the sensitivity of the speakers is 87 db/2.83 volts/1 meter. And its impedance is close to 4 ohms throughout those parts of the spectrum which typically require the most energy, as well as in the upper treble region. Since 2.83 volts into 4 ohms corresponds to 2 watts, for a 4 ohm speaker 87 db/2.83 volts/1 meter corresponds to only 84 db/1 watt/1 meter. The 300SE is rated at 10.5 watts into 4 ohms, which for most listeners is of course far too little power for an 84 db speaker. IMO that would still be true even if the amp only needs to handle frequencies above a few hundred Hz. (I note that the speaker’s crossover point is specified as 500 Hz, but JA’s measurements show that the midrange driver is still making significant contributions to the speaker’s output at frequencies well below 250 Hz).

Second, while a passive biamp arrangement relieves the mid/high frequency amp from having to supply current and power at low frequencies, in that arrangement both amps still have to output a voltage corresponding to the full frequency range of the signal. Therefore, assuming the two amps are properly gain matched in some manner, in a passive biamp arrangement you would only be able to use a very small fraction of the 350 watt/4 ohm power capability of the SA200.2 without driving the 10.5 watt 300SE into clipping. Very possibly not much more than 10.5 watts of the SA200.2’s power capability could be utilized, depending on the voltage swing capability of the 300SE.

Third, the gain of the SA200.2 is 28 db, and I calculate the apparently unspecified gain of the 300SE as being 15.4 db for a 4 ohm load. So if you were to not use an electronic crossover ahead of the amps you would have to provide some other means of attenuating the SA200.2’s input by about 13 db.


And given the low sensitivity of the speakers and the limited power capability of the 300SE it seems to me that even if you were to use an electronic crossover ahead of the amps (which would presumably eliminate the latter two of the three issues mentioned above) you would probably have to set its crossover point considerably higher than the speaker’s crossover point, perhaps to 1 or even 2 kHz. Which would seem likely to result in a significant degree of sonic compromise, as well as an inability to hear a lot of the sonic quality the 300SE has to offer. And of course there would be significant expense for a good electronic crossover, that would only be used for six months.

Finally, if you do biamp be sure to note the following statement in the Stereophile review of the speaker:

Dual terminals are also included for biwiring or biamping, if desired. Instead of the usual straps that connect such terminals for single-wiring, there’s a knob on the terminal plate that either straps the terminals together or disconnects them, depending on whether it’s turned fully clockwise or counterclockwise. If you biamp the speakers, however, be careful to check how this knob is set; without visible connecting straps, you can’t tell by looking if the terminals are unlinked. Tying the outputs of two amps in parallel can ruin your day.
Perhaps the simplest and best thing to do during the six months is to use the 300SE by itself, just some of the time, while listening at modest volume levels to recordings that don’t have a great deal of dynamic range. In any event, good luck however you decide to proceed. Regards,


-- Al