Bi-amping

What is your opinion on Bi-amping using Electronic Crossovers?
Do you think it's worth to give it a try?
I do see that there some advantages... But there are also more parts along with the signal.
Rod Elliott seems to be a fan of bi-amping, and he has a quite nice "24 dB/Octave Linkwitz-Riley Electronic Crossover" on his webpage, perhaps it is worth giving it try.
http://sound.westhost.com/project09.htm

/Freddie
 
...perhaps it ought to be this link:

http://sound.westhost.com/bi-amp.htm

A digest version might be nice. Perhaps there should be FAQs for all sorts of different topics. Perhaps a glossary, too...newbie guide...wishful thinking...

-Won

PS oh, to answer the question: it can make your system better by bypassing the evils of a passive crossover, but it's obviously more complex because you need an active crossover and additional amplifiers...
 
Tri-amping

I'm actually thinking of going tri-amping by totally getting rid of the passive crossover and building an electronic crossover into the pre-amp. I think there should be an improvement in sound without the losses of inductors and capacitors in the passive xovers. Anybody tried that? Does getting rid of the passive crossover change the original character of the speaker sound?

ckt
 
What configuration should the electronic crossover use?
I did a little searching, and there are tons of different configurations..
Linkwitz-Riley, Bessel, Butterworth, Sallen-Key...

I guess Rod's 24dB/Octave Linkwitz-Riley filter is good. If I just replace the OP-amps with a simple FET follower.

Suggestions?

/Freddie
 
Multi amping is technically the best solution, but often real life makes me believe that, in the budget range I can afford, passive x-over is still the best compromise.

IMHO it takes a lot of engineering to make a well designed multi-amp system, and a lot of money to invest in it

A - You need to carefully select the 'marriage' of freq response of your speakers
- With a passive x-over you can play with the filters Q and slopes to equalize your drivers (although paying it in efficiency), in multi amp all that you have is gain control, cut point and slope (unless you custom design the transfer function of the x-over or you add some very good parametric eq)

B - You also need to marry the sound of the 2+ amps, ideally they should be (or sound) identical. And what about the sound of the x-over?

C - True that in a passive x-over you have some coils and cap between your signal and the speakers, but in multi amp you have a whole bunch of electronics. Electronics that sound well is expensive, so the question is : do I have a better sound with 2 $1000 amps + $ 1000 x-over or with one $ 2700 amp + $ 300 in good passive x-over components?

I have no answer for that, can only say that in my limited experience I almost always had better results maximizing the quality of the components rather than multiplying their number and the complexity of the system.
But this is absolutely personal, another person could prefer the sound of the multi-amp-at-same-price, one nice thing of our hobby is that the concept of 'sound quality' (above a certain level) is extremely subjective.
And anyway, how can you tell in absolute way if Rolls Royce is a better car than Ferrari or Porsche? We could discuss for centuries!

So my final advice is : go ahead and try it if this is not a big sacrifice for you; if you are a bit struggling with budget, try first to listen to some multi amp system (maybe somebody in list lives near you) before investing your money.
bye
sandro
 
Multi amping

Sandro,

Thank you very much for your opinion. As I build my own amps, cost is not really a big issue. Previously, I've tried bi-amping and did experience a noticeable improvement in sound. However, the passive crossovers were retained and balancing of sound level between the lows and the highs was solely by potentiometers. Maybe I could try the discrete Naim crossover mentioned by Goeff to see whether there's any improvement of the discrete circuit over that of the OP based ones. In the meantime, I'll also upgrade the passive components in the xovers.

ckt
 
Hi diyman,

You aren't really going to get all of the advantages of bi-amping until you get rid of the passive crossovers. People spend incredible amounts of money on speaker cables to reduce impedance and then put up with passive crossovers that have 10 times the impedance of the cables.

Where bi-amping really shines is when you want to go loud. Often when you really crank up the volume deep bass notes can clip on you. If this happens with passive crossovers then the high frequency distortion caused by the clipped bass note get passed through to the tweeter and sound bads (burn up the tweeters too if you do this too much).

With active bi-amping the bass signal can still clip, but the high frequency distortion doesn't get reproduced by the woofer, so the sound is much improved. Plus since there isn't a tweeter connected to the amp that clipped, nothing burns up.

P.S. This is the reason why PRO sound systems use absolutely insane power amps on their subwoofers. They will routinely use a 3400 W amp on a sub that is only rated for 1200 W just to make sure they don't clip when the drummer lays into the kick drum. Rule of thumb is to size the amp 2 to 3 times greater than the speaker power rating.

If you really want to hear how good bi-amping can be go to a good pro audio shop and audition some of the better near field monitors (like anything by Genelec or the bigger Mackie monitor). These give an amazingly good sound for such small boxes, probably because everything in them was optimised for their specific application.

Phil
 
Phil:
Pro sound systems also utilize full bandwidth limiting so they don't blow their drivers out. Whats going to happen if someone upsizes their sub amp and sees how loud it will go. Do you think they will realize what that clicking sound is in time. Best to give a warning. Some people on this forumn are relatively knew to some of this.;)
 
Hi PassFan,

Thats true, although I would expect that the SPL would drive you out of the room before you would be actually able to smoke a subwoofer. My point about this was that tweeters can be blown with just a few seconds of clipping at what might be considered normally loud playing. If you want to run stupid loud then I guess buying new drivers is the price of your education.

P.S. Off topic question, your user name isn't referring to an attempt to deal with the immense amount of heat that certain class A amps designed by the Famous Nelson Pass put out is it? ;^)

Phil:D
 
Here's a thought.

What if the amplifiers we used for biamping were designed to the appropriate crossover characteristics already? As a simple example, the tweeter amp that I plan on building is op-amp based. What if i wrapped some capacitors and resistors around it to also build a high-pass filter?

Has anyone tried this or have any guesses as to how well/poorly it would work?

-Won
 
I prefer bi-amping because when I reallly get into listening, I find that I like to use maybe 100 times more power for the lowest notes. But I also believe in sealed sub enclosures that provide no added resonant reinforcement, which produces a boomy effect. Also, if the impedance between the amps and the speakers is kept lower, the speaker cones should track the signal better.
 
Won,
It works and works well. It is particularly graceful when you've got stages that already need to be capacitor-coupled and you want a simple 6 dB/oct slope. I do something similar for my tweeters; I just use a follower as a buffer, then a cap that works against the front end of the amp. You have to change the cap value if you change to an amp with a different input impedance, but it's very clean.
The Zen amp, with the caps on the front and back end, offers numerous possibilities. The cap at the back will be somewhat more difficult to calculate, given that it's working against the speaker, rather than a nice, predictable resistance in the front of an amp. Note that the feedback loop in the newer Zen will try to correct the crossover slope; you might want to go with the original Zen which (I believe--don't have the schematic at hand) took the feedback from before the caps.

Grey
 

Neopsp

Member
2002-04-22 9:13 pm
Tweeter Protection

How would you protect the tweeter in an active x-over configuration? I need to do this because of the amps caps that drain giving the thump at turn off. Adding a cap in series with the tweeter will act as a 1st order high pass. This will mess around with the phase. I am bi amping especially to keep coherent phase.
Thanx
Neopsp