Bi-Amp success story

Hi Joel; Thanks for sharing your experience(s) with bi-amping. The subject is quite interesting to me as I am planning a "passive" bi-amp set-up myself in the next month or so. I have Vandersteen 3As, and Vand. Audio highly recommends passive vertical bi-amping. Based on your experience, it sounds like you weren't too impressed with passive though. I guess I'll find out.

I'm no expert but I think your "active" bi-amp may have worked well mainly because you were able to set your active X-over at the same HZ that your speakers crossed over, ie 80 HZ. As to power rating, do your Yamaha amps actually produce 330 wpc into 4 Ohms? If so it should say so in your owners manual (ie, you can't just double 115 wpc and assume they are putting out 330 wpc into 4 Ohms unless they are designed to do so). And too, I don't think you can add 330 + 330 and claim 660 watts, because amp power is conventionally expressed in watts per channel. Also, if your amps are stereo amps (as opposed to dual mono), the bass side would likely be drawing much more power than the mid/treble side.

One of the main reasons to have powerful amps is that they can better handle the "transient spikes" in music that require much more power and occur especially in dynamic music with strong bass. Speaker impedence and sensitivity are important too. And of course the other reason is just simply to play louder. A speaker with nominal 4 Ohm impedence would likely have a range of something like 3 Ohms to 16 Ohms over their whole frequency range.

About "loudness"; it takes double the power to get a 3 dB increase in actual loudness. So if your amps were actually drawing 200 wpc (and at this point I think they would be very hot), it would take 400 wpc to get a 3 dB increase in SPL. But OTOH if they were drawing 10 watts at a given SPL level, then 20 watts would produce a 3 dB increase in SPL-- this would be a much more likely scenario unless you're running your system at absolute max.

I suppose the above sounds sort of negative, but I don't mean to be. I'm just trying to understand what you did so it might help in what I do in a month or so in my attemps at bi-amping. Again, thanks for sharing and Happy Listening. Craig

Garfish-

WOW, where do I start? At the beginning I guess. You may have good success with your passive bi-amping, but I would not expect too much. Probably not enough to justify an additional amp purchase. You will get better soundstage as a result of better stereo seperation by running your left and right on different amps. Probably not an audible increase in volume however. But let me know what you do find. I am very interested.

Whoops, I hit return by accident and published my comments. Oh well it will look like this is a popular thread then I guess. To continue, yes I have no doubt matching my active crossover to the speakers had everything to do with my results. That is critical because you are not messing with the passive internal crossover in the speakers, just easing the load on the amps by only having them work on the frequencies that they are responsible for. That has do do something to keep things clean sounding too.

As far as my amp specs go, yes I went by the manual. This is what it said----

8 ohms 260 wpc RMS, 0.003% thd, 450 wpc dynamic
6 ohms 295 wpc RMS, 0.007% thd, 560 wpc dynamic
4 ohms 330 wpc RMS, 0.02% thd, 740 wpc dynamic
2 ohm 960 wpc dynamic
1 ohm 1000 wpc dynamic

So I tried not to assume anything. I see your point regarding the bass taking more power. However that all depends on the crossover freq. I found some interesting numbers showing this break down of power (expressed as Freqency and % of average power needed for the running the speakers above and below that number)----

250 40%/low 60%/high
350 50%/low 50%/high
500 60%/low 40%/high
1,200 65%/low 35%/high
3,000 85%/low 15%/high
5,000 90%/low 10%/high

It is much more complicated than that and depends on efficiency of the drivers, differences in impedance etc. SO many variables. The best way to tell for your system is to run both sides of the amp at max levels (set the pre-amp for normal listen levels of course) and then reduce the volume for whatever seems out of balance. (ie too much bass, reduce the volume low side of the amp) If you have seperate controls for Left and Right levels on your amp this is a VERY simple way to get things adjusted just right.
But I figure I have (on average) 330 watts going to the highs and 330 watts going to the lows (I suppose I should say 'available for') on each side because it sounds just right with both *sides* of the amp set to the same level. But that is ALWAYS an estimate even for a single amp set-up anyway. (And I agree that the loads will vary depending on the fequency being reproduced. I have a response curve for my speakers and it is very obvious that 4 ohms is just an average as it varies between 9 and .9 ohms (yes, those numbers are right))

As for *loudness* I think that, yes I *have* doubled the power going to my speakers resulting in a 3 db increase in sound levels. I have not measured it yet, but I can tell. It plays louder at lower levels on the volume control for one thing. And my wife gets madder if that counts for anything.

I look forward to your continued dialoge.

Regards,

Joel

Hi (again) Joel; Thanks for the detailed info. on your bi-amp setup. Your Yamaha amps are more powerful than I expected, especially dynamically. I don't know what order cross overs your Kappa 9 speakers use, but Vand. 3As use 1st order-- this is the steepest x-over.

An active electronic x-over cannot be used w/ Vandersteen speakers, because the signal cannot bypass the internal x-over. Because of your thread, I dug out my Vand. owners manual, and looked up specs., x-overs etc. R. Vandrsteen also says only slight to moderate improvements in sonics can be expected by passive bi-amping, and he goes on to say that a single higher quality amp will out-perform a pair of lesser quality amps-- I guess I'm about to find out about some of this, so we'll see!

Just one more Vand. "thing"-- their speakers also should not be horizontal bi-amped as mids will be "confused" (like me). I already have two high quality McCormack DNA-2DX amps(300 wpc 8 Ohms, 600 wpc 4 Ohms etc), and they are now in for upgrading at SMc Audio to Rev. A, when done, my amps should approach world class-- but still, I've got my fingers crossed that I'm going to like the "new" amps, and in a bi-amped configuration. I've enjoyed the exchange of info. Thanks. Craig

Craig, just for your info i had run a set of 4 way / 5 driver towers in a passive arrangement. I had two different amps from the same manufacturer horizontally configured. This gave me 400+ wpc on the top side ( 200 Hz and above ) and 600+ wpc on the bottom ( below 200 Hz ). Since these speakers are "thirsty", i could still drive the amps into compression if really cranking hard.

I then went into a set-up where i had identical amps on top and bottom ( both 600+ wpc ). I could still drive them into compression.

I later switched this configuration to running a single amplifier that is rated for 1200 wpc at the same impedance. Even though i had 900 to 1200 watts per channel driving the speakers before, going to one larger and more efficient amp made a MASSIVE difference. I could now play measurably louder and measurably cleaner with far less listening fatigue. The only drawback to this is that i did have greater bass impact with the specific amp that i was previously running on the bottom end.

In case your thinking that the first amps were just "wimps", take my word for it that these are STURDY. They can run bridged into VERY low impedance loads without any fuss at all. I have seen people running these models bridged into speakers that normally give unbridged amps a fit.

In plain English, i would not bother doing passive bi-amping ever again. To me, it was a waste of time, money and power. I wish you better luck in your efforts and ask that you keep us posted after you've played with your set-up for a while.