# Bi-amping



## organm (Dec 5, 2009)

Hi,

I am in the process of understanding bi-amping and need some help.

I have bi-amplable Polk RTIa9's.

I was considering buying an Emotiva XPA-5 amp and using it to bi-amp the Polks.

Is it possible to run two channels to the Polk front right and another two channels to the Polk front left and the remaining channel to the Polk centre?

If this can be done will the bi-amping make any real difference? The Polks are rated 50-500w so they should be able to handle it.

Thanks.


Mark


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## Jungle Jack (Jul 28, 2009)

Hello,
That is exactly what you could do with the XPA-5. There have been differing opinions of the merits of biamping, but I think it can be useful in certain applications. I would again rather get the XPA-2 over the XPA-5, which has the same power supply and capacitance as the XPA-5. 

If 2 Channel is your priority, the XPA-2 is the way to go and let your AVR drive the other channels.
Cheers,
JJ


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## Jon Liu (May 21, 2007)

I actually like the idea behind Bi-amping personally. Bi-wiring is a different story. Bi-wiring is essentially wiring two cables to the same common amplifier whereas bi-amping is actually wiring two amplifiers to a single speaker, often times for high frequencies and low frequencies.

As far as bi-amping, I think it would make a difference, but depending on so many factors, that level may be very little to quite a bit of difference.

The nice thing about the XPAs are they are very cheaply priced as far as dedicated amplifiers go!


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## recruit (May 9, 2009)

Bi-amping can yield great results and as the others have mentioned the Emotiva amps are great VFM, I have bi-amped in the past and it can really improve 2 channel music for you, the more power the speakers receive the better the performance.


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## organm (Dec 5, 2009)

Jon,

Please explain why you would go for the XPA-2 over the XPA-5. 

I see that the power per channel is higher but it is only two channels which does not allow me to power the centre.

Also, another thing for me to consider is space, very limited in my cabinet. So I thought grabbing five channels would be a bit more future proof.

Interested in your thoughts! 

Mark


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## Jungle Jack (Jul 28, 2009)

Hello,
The XPA-2 has the same power supply(1.2 kVA) and almost the same capacitance as does the 5 channel XPA-5 (45000uf vs 60000uf). That is the 2 channel amplifier is massively more powerful than the 5 channel version. That is why the XPA 2/5 sell for the same amount of money.

If you are going to be going the receiver route anyway, if you use a 2 channel amplifier to drive your fronts the other channels driven by the receiver will have more power. The fronts are usually the biggest current draw of your HT speakers.

Using the XPA-2 will give you the best possible 2 channel performance. Again the 2 channel and 5 channel use the same power supply and capacitance. This makes the XPA-2 a much more powerful amplifier.
Cheers,
JJ


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## glaufman (Nov 25, 2007)

I think most of the controversy surrouding the benefits of bi-amping is the belief that you achieve more performance increase when you ditch the passive, speaker level crossovers in most speakers and go to a line level crossover before the amp.
That being said, the paper I read that supposedly proved this IMO exaggerated this need.

I'm not saying there's no benefit to biamping while still using the passive xovers...


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## Kal Rubinson (Aug 3, 2006)

glaufman said:


> I think most of the controversy surrouding the benefits of bi-amping is the belief that you achieve more performance increase when you ditch the passive, speaker level crossovers in most speakers and go to a line level crossover before the amp.


The fly in this ointment is that the line level crossovers have to be as properly customized to the particular speaker(s) as the built-in ones and, thus, off-the-shelf networks will not suffice. This problem is somewhat relieved these days with the appearance of DSP-based devises like the DEQX.



> I'm not saying there's no benefit to biamping while still using the passive xovers...


I would........................unless the current(!) single amp is significantly inadequate.


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## recruit (May 9, 2009)

In stereo set-ups I have found good improvements that were made when Bi-amping, and further improvements when adding mono blocks....


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## Jungle Jack (Jul 28, 2009)

Hello,
With the OP application, I have been advocating using a single XPA-2 as opposed to using an XPA-5 to biamp the fronts and power the Center Channel.

Primarily, I advocate the XPA-2 because it offers so much more power and current per channel than the XPA-5 does and the OP is going to be using a receiver which means there will be amplification present.
I really think the XPA-2 will outperform the XPA-5 configured to biamping the fronts. Mostly because the 2 amplifiers share the same toroidal transformer and within 15,000uf of filter capacitance.
Cheers,
JJ


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## tonyvdb (Sep 5, 2007)

Jack, I've been considering doing something similar with my Samson Servo 4 channel amp. Right now I have it bridged running 240watts into 2 channels. Im just not sure if going back to 4 channels at 120watts each and running my speakers biamped will yield any difference. as this would give me individual control of the highs and lows.
What is your opinion? The Samson has a toroidal transformer but is not actually rated to drive my Mission 765's @ 4ohms in bridged mode but so far has not had any issues.


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## Jungle Jack (Jul 28, 2009)

Hello,
Interesting. I am surprised you have run into no thermal issues driving your 4 ohm Missions with a bridged amplifier as this is where many multichannel amplifiers run into trouble. Bridging puts much strain on amplifiers. I blew up a Parasound HCA-1000a by running it bridged to drive a Martin Logan Theater i. It was sheer stupidity on my part I as I knew full well that the speaker was nowhere near 8 ohms and was much closer to 2 ohms. I must say before it blew, it sounded great.

Given that it is a 4 channel amplifier and you are having zero issues running bridged, I would probably keep it how you got it. You usually get more output when configured bridged as opposed to biamped. Biamping/Biwiring is a divisive issue with many Speaker Manufacturers actually being against it. Thiel Audio provides only a single set of binding posts as do many others. The thought being the designer spent much time making optimizing the crossover. The current ESL Series of Martin Logan with active woofers (Vantage, Spire, Summit X) offer 4 posts a side only to accommodate those who already have biwired speaker cables even though they are not biampable or biwirable.

All the same, it might be worth a try just to see if there is any difference. In the name of science if you would. However, I would guess it will sound best bridged.
Cheers,
JJ


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## tonyvdb (Sep 5, 2007)

Jungle Jack said:


> Hello,
> Interesting. I am surprised you have run into no thermal issues driving your 4 ohm Missions with a bridged amplifier as this is where many multichannel amplifiers run into trouble. Bridging puts much strain on amplifiers. I blew up a Parasound HCA-1000a by running it bridged to drive a Martin Logan Theater i. It was sheer stupidity on my part I as I knew full well that the speaker was nowhere near 8 ohms and was much closer to 2 ohms. I must say before it blew, it sounded great.


 The Missions efficiency is 93db so not a hard speaker to drive I would think. But it dose say something for the quality of the Samson amps, alot of people dont classify them as being all the good. It gets warm but never hot (only convection cooled) even when running it hard. I get about 3 (the 3rd just flickers) of the 5 LED meters to light when Im at reference.



> All the same, it might be worth a try just to see if there is any difference. In the name of science if you would. However, I would guess it will sound best bridged.
> Cheers,
> JJ


I may do this over the weekend if I have some free time:dumbcrazy:


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## nova (Apr 30, 2006)

Kal Rubinson said:


> I would........................unless the current(!) single amp is significantly inadequate.


One thing I noticed when experimenting with passive bi-amping,... there is the ability to boost the high end or low end of the speaker. Whether that is an advantage or not :huh:, maybe but I am sure there are easier and better ways to do this if your system requires it.


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## Kal Rubinson (Aug 3, 2006)

nova said:


> One thing I noticed when experimenting with passive bi-amping,... there is the ability to boost the high end or low end of the speaker. Whether that is an advantage or not :huh:, maybe but I am sure there are easier and better ways to do this if your system requires it.


I think that is not as useful as a real EQ or tone control as you are so limited in what you can do. In fact, it is probably all too commonly the basis of hearing an "improvement" with biamping. :whistling:


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## nova (Apr 30, 2006)

Kal Rubinson said:


> In fact, it is probably all too commonly the basis of hearing an "improvement" with biamping. :whistling:


I'd certainly agree with that.


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## glaufman (Nov 25, 2007)

Kal Rubinson said:


> The fly in this ointment is that the line level crossovers have to be as properly customized to the particular speaker(s) as the built-in ones and, thus, off-the-shelf networks will not suffice. This problem is somewhat relieved these days with the appearance of DSP-based devises like the DEQX.
> 
> I would........................unless the current(!) single amp is significantly inadequate.


Agreed.


Kal Rubinson said:


> I think that is not as useful as a real EQ or tone control as you are so limited in what you can do. In fact, it is probably all too commonly the basis of hearing an "improvement" with biamping. :whistling:


Hmmm.........:innocent:


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## Kal Rubinson (Aug 3, 2006)

Kal Rubinson said:


> I think that is not as useful as a real EQ or tone control as you are so limited in what you can do. In fact, it is probably all too commonly the basis of hearing an "improvement" with biamping. :whistling:





glaufman said:


> Hmmm.........:innocent:


Well, all it takes is a very small gain mismatch between the amps for the balance to shift to "warmer" or "more detailed" or "more open."


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## Jungle Jack (Jul 28, 2009)

Hello,
That is true. It is why I always ask when people are auditioning different lines of speakers to make sure they are level matched as closely as possible. That is if auditioning speakers of different efficiency to make sure this is compensated for because otherwise, people will always prefer the louder speaker if switched back and forth. Increase in loudness always correlates with all the adjectives that Kal used.
Cheers,
JJ


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## Lordoftherings (Feb 8, 2009)

Mark, just don't bother at all with Biamping your Polk Rti A9 speakers or any other speakers in your system for that matter. It is more for active x-overs, and then... onder:

Here's the right thing to do for your Polk Rti A9 main speakers; get the Emotiva XPA-2 to simply power them. You'll have all you need to drive them up to their full potential, believe me. :bigsmile:

For the rest of your speakers, you can use the Emotiva XPA-5 in combination with a Pre/Pro like Onkyo PR-SC886P. Or just go with a receiver like the Onkyo TX-SR876, or TX-NR906, or TX-NR1007, or TX-NR3007. Any of these combinations will do plenty. I mean if you go the route of the receiver, no need to add an external amp. You just use the XPA-2 for your two front mains, and running them almost full range. All you other speakers will be cross at 80hz anyway, so any of the receivers mentioned here will do just perfectly fine, I can assure you of that. And because your room is quite large (9 meters by 6 meters), two subwoofers are a good idea.
And is your big room opens to adjacent room(s)? If yes, definitively two subwoofers. And preferably two exactly the same (same brand and model #). I don't know which one(s) you actually have (my guess is that you maybe have one Polk sub), but get the same one, or two of them if you don't have any.

Check how much money is available in your bank account, without interrupting your comfort level, or your wife's equilibrium, then just shoot your arrows on your targets. :bigsmile:

Again, just forget about Bi-Amping, it's really not worth it in your particular situation.

Bob


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## glaufman (Nov 25, 2007)

Kal Rubinson said:


> Well, all it takes is a very small gain mismatch between the amps for the balance to shift to "warmer" or "more detailed" or "more open."


Ok. I'm convinced. :T


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## Lordoftherings (Feb 8, 2009)

I already was. :bigsmile:

* Bi-Amping or Tri-Amping is great, on active powered loudspeakers, or with specially designed loudspeakers with properly designed and concealed (separate) active crossovers.

But for the vast majority of regular loudspeakers on the market (even with two or three sets of speaker's binding posts), it is futile...


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## organm (Dec 5, 2009)

Thanks Bob,

I have found out that I can source an Onkyo 906 local (10 minutes from Home) with the latest firmware for $2750. Very good price for Australia.

Probably will go that way if I can convince the wife. Maybe add the Emotiva down the track (not too far).

Just a couple of questions on adding the Amp using the preamps.

1) The 906 has RCA preouts rather than balanced lines. Is that an issue/problem with quality?

2) I use my HT to watch normal TV. If I was using an amp via the preouts for the fronts would I need to power it up to just watch TV or would I ignore it and just power up the receiver and use the centre, which would be powered by the receiver. Seems a little over the top to power up the amp just for TV.

Thanks.


Mark


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## tonyvdb (Sep 5, 2007)

The 906's pre outs are a line level output and some pro amps do have the ability to accept it by using 1/4" mono TS adaptors if it only has XLR inputs you will require a line level booster of some sort (many kinds available).
You can use the receiver only and use the displays speakers without turning on the amp or simply run an optical audio cable and component cable from the satt receiver directly to the display and then you would not need the receiver on at all but you would then have to select a different input on the display.


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## Jungle Jack (Jul 28, 2009)

organm said:


> Thanks Bob,
> 
> I have found out that I can source an Onkyo 906 local (10 minutes from Home) with the latest firmware for $2750. Very good price for Australia.
> 
> ...


Hello,
Mark, the 906 is one of the more powerful AVR's out there so you well might not need an outboard amplifier. Balanced Cables are not often used with HT. Some prefer them, but it only really is a need in cases of very long cable lengths or massive RFI interference. One of the big reasons Balanced Cables are used in Studios is there are often long cable runs and interference. Furthermore, the XPA-2 does not even have Balanced Outputs.

If you end up using an outboard amplifier, the only way you will be able to get sound out of the speakers they are connected to is to power on the amplifier. As you pointed out, you could leave the amp off and only use the Centre Channel and Surrounds, but it kind of defeats the purpose.
Cheers,
JJ


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## Lordoftherings (Feb 8, 2009)

Hi Mark,

First, you might found that you won't even need an external amp with your 906. By the way, this is a very smart choice, the 906. Just say to your wife that Bob did give you the go ahead. :bigsmile:

1. If you do add an external amp like an Emotiva one (XPA-2 or XPA-3) down the road, you just use the RCA unbalanced connections. The Balanced ones are useless anyway for your particular usage.
* Balanced connections are for professional recording studios, where they need very long runs of cables to isolate and cancel any feedback. They use it for microphones for example.
For home, the only advantage they have is just a more solid connection, that's all.
And you know what Mark, RCA Unbalanced connections are better than XLR Balanced connections, in the vast majority of cases for distortion (THD+N), Crosstalk and even signal-to-noise ratio (S/N "A" weighting). And even in Frequency Response sometimes.
And another fact; for an electronic product to be Truly Fully Balanced from Input to Output, it will be VERY expensive. Emotiva amps are NOT Truly Fully Balanced Differential mode from their design, so the point here is completely moot in first place.
RCA jacks unbalanced connectors are perfectly fine in 99.99% of cases.

2. Mark, if you are only watching some TV programming (news...) , why just not use your TV's speakers? And if the TV programs you are listening have some interesting audio, your receiver will automatically engage the external amp (Emotiva), through its 12V trigger.
So, you see, everytime you fire (turn ON) your receiver (906), it automatically trigger (turn ON) the external power amplifier (Emotiva); and all from the remote control and sitting with your wife in the comfort of your couch. 

Anything else? 

Cheers,
Bob


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