[tensai]

I am demoing some speakers in the house right now. Specifically, JBL Ti10ks, 6 ohm, 91 dB sensitivity.


I was thinking about testing these speakers on a old Denon receiver I have sitting around, DRA-825R, that's rated at 90 wpc into 8 ohm. Since the speakers have the ability to bi-amp, I was thinking about using the Speaker A terminals for one set of binding post and Speaker B terminals for the other set. Hoping this would give the speakers a little bit more juice . . .


That is until I started reading the manual for the old receiver (can't believe I still have the literature), and it stated that "when connecting to 2 sets of speakers, please use speaker with resistance of more than 12 ohm for optimal performance. Speakers with less than 12 ohm is not recommended under such circumstance."


Would using 2 different sets of binding post on the same speaker be essentially the same as connecting to 2 separate speakers? Since I am demoing a friend's speakers, I'd rather not repay his kindness by damaging his speakers.


thanks,

 

[David Guill]

You probably wouldn't hurt the speakers but you would damage your amplifier. The A/B speaker selectors allows speakers to be set up in parallel which has the affect of decreasing the overall impedance seen by the amplifier. In essence, your amplifier must work harder and this could cause damage to it. I wouldn't do it.

 

[Swampfox]

You are trying to "bi-amp" your speakers by using the two outputs from your receiver to the two binding posts on the speaker. This is equivalent to using 1 wire to the speakers and using the metal bridge across the binding posts. So all you are doing is doubling the wire, and hooking your speakers up in a needlessly complicated manner.

 

[Larry Fine]

Swamp is right (Sorry, David). Paralleling a single speaker's sections via bi-wire on separate terminals is no different than bi-wiring them on a single set of terminals, provided the receiver's A and B terminals are paralleled, which your are, as evidenced by the 12-ohm warning, which tells us that your receiver is stable with loads as low as 6 ohms.


It may be confusing, but when speakers with separate terminals for the high- and low-sections are paralleled, and each section is, for example, 8 ohms, the total load is (suprise!) 8 ohms. That's because outside the frequency range of each section, the impedance rises due to the crossover, so they're not 8 ohms at the same frequencies.


For example, when feeding a full-range signal into a two-way, bi-wireable speaker, the tweeter's impedance (or, more accurately, the tweeter's crossover's input impedance) below crossover frequency is high enough to be negligible, and the same for the woofer's impedance above the crossover frequency. (Of course, there is some overlap.)


So, other than the overall lower wire resistance, as cited by the Swampster, there is no benefit, and no increase of power output. Only if your speaker wire were too small to begin with would there be a difference worth the cost of the wire itself. Now, if you want the woofer and tweeter sections to be separately switched, then go ahead and try it.