Active Bi-Amping/Tri-Amping FAQ

[JohnTaylor]

New to HT, jumped in with a pair of RP-160M driven by Denon AVR-X2400H. This is what fits the budget for now. R-115SW, RP-280F and RP-450C will follow when I can afford it. Anyways. I've been googling around in the last few days, but I couldn't find a definite answer to my question.

During pre-purchase research, I've read that both my new speakers and amp are capable of bi-amping. I figured some speaker wire and banana plugs won't break the bank, so there's no reason not to do it if it would improve the sound even a little. My only concern is that the speakers rated for 100 Watt, the amp pumps out 95 Watt. Which is perfectly fine without bi-amping. But what happens when I bi-amp the speakers, I'll effective double the power input, both the tweeters and the midrange speakers gonna receive the full 95 Watt. Will the excess power damage my speakers? Can I and should I limit the power input on the amp side or is it done automatically when I set it up in the GUI?

Thanks,

John

[Chris A]

2 hours ago, JohnTaylor said:

My only concern is that the speakers rated for 100 Watt, the amp pumps out 95 Watt. Which is perfectly fine without bi-amping. But what happens when I bi-amp the speakers, I'll effective double the power input, both the tweeters and the midrange speakers gonna receive the full 95 Watt. Will the excess power damage my speakers? Can I and should I limit the power input on the amp side or is it done automatically when I set it up in the GUI?

 

I think its a common misconception that you cannot use amplifiers that are rated for more power/current output than the loudspeaker are rated for (i.e., so called "music power" input).  You can use more amplifier power, and I doubt that you'll try to use everything that the amplifiers can pump out.  Remember that the K-77 tweeter in all Klipsch Heritage loudspeakers is rated for only 4 watts input--music power.  It's the person in the room controlling the volume control down to reasonable non-hearing-damaging levels which is the moderating factor--always.

 

Instead, by bi-amping or tri-amping you're using the added headroom of the higher power amplifiers to increase the effective slew rate of the amplifier output, which will sound crisper with more clarity and less muddy sounding. Like anything else, if you drive your car around town with your foot on the floor all the time, more than one bad thing will occur, and soon (not the least of which is your health and the health of others that might be in your path). 

 

Not having to place the tweeter and midrange drivers on the same electrical circuit as the high-mass woofer will increase the fidelity of the loudspeaker's output, and also protect against any clipping overloads that the woofer circuit might encounter. 

 

If you look at the first posting in this thread, you will find the list of reasons why bi-amping and tri-amping is superior to mono-amping.  Fear of "blowing out" acoustic drivers I've found isn't typically one of the issues--although the fast-limiting circuitry of most commercially available DSP crossovers will absolutely protect your tweeters, midrange drivers and woofers if you consistently listen at extremely high listening levels (i.e., much greater than 100 dBC average at the listening positions). 

 

Chris

[Wim M]

3 hours ago, JohnTaylor said:

My only concern is that the speakers rated for 100 Watt, the amp pumps out 95 Watt. Which is perfectly fine without bi-amping. But what happens when I bi-amp the speakers, I'll effective double the power input, both the tweeters and the midrange speakers gonna receive the full 95 Watt. Will the excess power damage my speakers? Can I and should I limit the power input on the amp side or is it done automatically when I set it up in the GUI?

Thanks,

John

 

It is most likely you blow a speaker when it is underpowered.  When this is the case and you crank it up to loud levels, the amp will start to distort (clip), and distortion is actually something speakers don't like at all.  I don't see any problem bi-amping with the AVR you mentioned, as long as you don't go up to really stupid loud levels.  

 

Note that the Denon you mentioned, puts out 95 Watts/ch with only 2 channels in use.  If you use all of its channels, this number will decrease significantly.  When you connect the rest of the speakers you mentioned, you 'll see the Denon break into a sweat rather soon.  This is where it gets tricky as for damaging speakers.   I'd recommend adding a separate 2 ch power amp to power your 2 biggest speakers, this will relief your AVR a lot, and make the rest sound cleaner.

[jcmusic]

A couple guys asked about my results with using the Xilica XP 4080, so here are the latest measurements from my room. It sounds awesome with these settings here, I haven't changed anything but some tubes since last year when I finished this and the results are pretty much dead on. I did pick up a little bit on the HF end but, not enough to adjust anything as you can see....

[beezbo]

Can a Heresy be effectively bi-amped (without internal modification) with an AVR that has low/high outputs for L/R with an adjustable digital crossover?

What would be the best way to tri-amp with an AVR?

[jcmusic]

You need two amps to bi amp, and three amps to tri amp...

[Droogne]

I have some problems in my active setup, and I was hoping some people could help me out. As I'm new to this I didnt knew what to look for to maximise quality. I knew not to go over 0db in the crossover it self, but I didnt focus on clipping. I see and notice now how much influence this has on the sound quality. I have a few problems in trying to fix this. 

 

I have a beep, which is most noticeable in my tweeter horn. This only depends on the amp level, and is not influenced by the AVR level (or settings) or processor levels. I'm using a Marantz SR7000 amp which needs to be turned down to -35db to remove the beep. That is insanely low.. the amp itself has decent power, but like this it can not give enough. It makes it so that I need to  make the difference very high in my processor to get it to the bass level. Same problem, but less severe, in my 2x 500W power amp which I use to drive the low end. All in all I need to pushe the speakers to their very limits in the AVR. They are set waaaay higher than the other channels (which is kinda crazy if you know that they have more than 12db sensitivity extra, ánd several times the power potential to drive them).   My very very very cheap (10 USD) china amp doesn't have this problem.. I tested it, and it comes out pretty *BEEP*less. I can easily set the level of 1 speaker with this amp driving both high and low end (it does not have balance control) , without having to use crazy proces. In the end this problem with my main amps is most visible in the clipping of the processor. Even at moderate levels it clips. And it is soooo noticeable.. 

 

How do I fix this? The amps I have now are temporary in every sense, so changing the amps is the solution I have in mind. How do I know if an amp is gonna give a beep or not? It would be a waste to spend good money on something when I gives the same BEEP / clipping problem I have now. 

 

Also, what other rules of thumb and principles should I follow? Not adjust the processing above 0db is one. What are some others? If I want to raise the level of a speaker, what is the best way? Adjust it in the AVR, amps or processor? Same for adjusting high vs low: amp or processor? 

 

Thanks in advance! 

[Wim M]

Which speakers exactly give a problem?  The ones that are connected directly to an amp or the ones that go through a processor?

 

Otherwise you'll have to expand this a bit, as I can't figure out how everything is connected.

[Droogne]

1 minute ago, Wim M said:

Which speakers exactly give a problem?  The ones that are connected directly to an amp or the ones that go through a processor?

 

Otherwise you'll have to expand this a bit, as I can't figure out how everything is connected.

Only the one going through the processor. The processor settings do not change the beep, only the amps levels. 

[Wim M]

OK, I see that your amp doesn't have balanced outputs, so I think you use RCA to XLR adapters.  My best guess is that this is the source of your problem.

[Droogne]

24 minutes ago, Wim M said:

OK, I see that your amp doesn't have balanced outputs, so I think you use RCA to XLR adapters.  My best guess is that this is the source of your problem.

Except getting amps with balanced inputs, any way to fix (or try) this? 

[NBPK402]

Some pics of my new PC case.  I'm using this rack for tri-amping my C, FL and FR, and also crossing to 5 subs that are individually time aligned and level matched.  

The PC case didn't do anything for sound, but sure looks nice.  I highly recommend everything else in the rack though because the amps and processors did improve my sound and measurements over the consumer gear I had before.

 

 

 

 

So what is in the PC case, and what does it do? Are the other ones for amps? 

Sent from my SM-T550 using Tapatalk

 

 

 

 

 

[Droogne]

Is the (pure) direct mode in an AVR a good way to ensure best quality when using active crossovers / DSPs ? 

[Schu]

@Chris A , is there such a thing as adjustable passive bi-amping?

[Chris A]

Yes...just disconnect the jumpers on the binding posts, then connect two amplifiers having gain controls.  You'll improve it by finding a passive crossover between the inputs of the two amplifiers to split the frequency response to the amplifiers, but this is not strictly required.

 

 

Chris

[Chris A]

If you want to have adjustable crossover frequencies, then you'll have to go analog passive to the inputs of your two amplifiers--like the following, and disconnect the internal passive in the loudspeaker:

 

https://www.ebay.com/itm/Vidsonix-VCB-100-Speaker-Passive-Crossover-Design-Box-Variable-Analog-DIY-NEW-/350429633168

 

Here's a review by Nelson Pass, et al.: https://www.audioxpress.com/files/attachment/2625

 

Chris

[Chris A]

Just a note:

 

This crossover is apparently limited to first and second order filters--or you could buy four of them and get fourth order using two in series for each channel. 

 

However, if you wish to avoid phase shifts between the two channels, I'd recommend using first order filters only (i.e., inductor in series for low pass, capacitor in series for high pass), then the phase shifts will be zero (but the steepness of the filters are only 6 dB/octave).  Having flat phase is, IMO, audibly important to get the highest sound quality possible. 

 

Chris

[Cmstpprr]

I just joined this community a few minutes ago. Have read through this topic but I have a question that I can't find an answer for. I have all the necessary components to bi-amp a pair of KLF 10's. When examining the factory xover it appears to be connecting the two 8 ohm midbass drivers in parallel. Does that change the resistance to 4 ohms? The speakers themselves are rated at 8 ohms. What would be the correct wiring for a bi-amp setup? There are many things I don't have the background to fully understand. Any help would be greatly appreciated.  

[Chris A]

Here is a link to a KLF-10 crossover network schematic: KLF-10.  You can see that the woofers have no added resistors in series, and that they are already in parallel, so your amplifier is already driving them at lower impedance values at the woofers' frequencies that it would see using bi-amping and direct connection to the amplifier output terminals.  Bi-amping actually makes the job easier for your amplifiers because they are directly connected to your drivers, so they don't see the sometimes difficult impedance changes introduced by passive crossover networks and the high frequency driver(s).

 

Chris

[Cmstpprr]

Great.....Thank you. I'm just curious and don't understand after reviewing the schematic is how this wiring equates to 8ohms at the external binding posts. Again please excuse my ignorance of how these things work.

Michael