Bi-Amping

[RadTech]

I said "I called and spoke to a tech " and that was his advice. I did not say Polk as a whole but what one of their techs said . However , the man does work for the company. Feel free to call them , I have often, and they are quite helpful.

[xlr8]

ok. so now i have a question. faq me.

i have lpa-1, and my fronts are bi-ampable. would i need a y-cable to split the L R channels coming from the LMC into 2 amp sections each? or do i just need to hook up another set of speaker cables from the second pair of amps into the speakers and be done with it?

[RadTech]

I would think that you would have to Y the L & R because all four channels need the same audio . 2 Lefts ,one for highs/mids and one for lows and, 2 rights in the same fashion Doesn't that amp run 50 watts on 2 of the channels? So you would want to run the highs/mids off the 2 ( 50 watt) channels and the lows off of 2 of the 125 watt channels.

[xlr8]

thats what i was thinking. though, i was just going to run the surrounds on the 65w channels and bi-amp the fronts using 2x125w channels.

[RadTech]

I looked at the specs for the LPA 1 and channels 6 and 7 are on a different gain structure than the other 5 channels. 1-5 's gain is 29 and 6 -7 is 26 so you will need to use two full ranges per side. I've tried 2 amps with different gain structures and it doesn't sound right. Please, let us know how it sounds.

[electroman]

I am biamping my center off an LPA-1, I tried a couple different routes:
1) Bridging channels 6 + 7 (creating a 6-channel amp) and running:
a) the bridged channel to the woofers on my center, and a regular channel to the tweeter.
b) the bridged channel to the tweeter, and a regular one to the woofers.
2) Unbridging channels 6 + 7 and running the surround speakers from them, while using two regular channels for the center.
1a created a noticeable hum from the woofers.
1b created some hiss from the tweeter, but less noticeable - I ran the system this way for about a month.
2 was by far the best option, I was hesitant to switch the surrounds to lower power, but noticed no problems doing so, and the center sounds much better.

[Animo]

Jun 20, 2008 15:28:05 GMT -5 Mr. Ben said:

Here's a quick intro with some terminology for beginners.

Bi-amp: Using more than one amplifier to drive a single speaker. Normally there is one amplifier, with one cable, going to one speaker, but many speakers can be driven by two. Some can even be driven by three. The back of these speakers will have more than one pair of terminals for speaker wire, which have some sort of removable link. Leave the link in place with one amp, or remove it to bi-amp.

Passive Bi-amp: This approach takes one input signal, and sends it to two power amplifiers. The output of one amplifier goes to the tweeter(s), and the output of the other goes to the woofer(s). You need to have two sets of speaker cables (one per amp), and two sets of connections on the back of your speaker. The crossovers inside the speakers are still operating so that you don't get high notes out of your woofers for example. Input signal->amplifier->crossover->driver. When someone says Bi-amp, this is usually what they mean.

Active Bi-amp: This approach moves the crossover function from inside the speaker, to before the power amp. So each amplifier is amplifying only the frequencies that will be output from the driver(s) it's connected to. Input signal->crossover->amplifier->driver. This approach can have benefits over the passive bi-amp, but only if done properly. Some speaker manufacturers sell complete systems like this. Phase, voicing, frequency rolloff rate and more needs to be taken into account.

I don't understand why everyone is getting their panties in a bunch. This topic is actually quite simple to understand. Bi-amping and passive bi-amping are in essence the same exact thing. In reality, it is not bi-amping, but bi-wiring. Your term active bi-amping is the only true method. You are bypassing some or all of the speakers passive crossover, and crossing the frequencies before the amps. Any speaker with multiple binding posts, can only be bi-wired unless specifically designed without a passive crossover or come with a dedicated active crossover. Unless specifically stated by a manufacturer, there is no way to truely bi-amp a speaker without disabling the passive crossover and in fact voiding the warranty.

Other topics worth discussion from the experts:
- Should you always use the same amplifier for highs and lows [Maybe]?

I would. This way you have the same sonic signature going to all parts of the speaker.

- Are you sending twice as much power to the speaker [probably not]?

If you are using two 200 watt amps, you are still only sending 200 watts of power to each terminal. The advantage would be in dynamics and headroom as multiple amps will have less stress and strain as compared to one amp powering the whole system.

- It it worth the cost [probably not]?

That is totally up to the individual. While not everyone has deep pockets, those that do, may find it advantageous. I have read that the only real advantages will be heard on a truely bi-amped system, however, some people have claimed sonic improvements with bi-wired systems....as always YMMV.

- Are Y cables better/worse than the little solid RCA splitters [likely the same]?

Probably worse, but anytime you split a signal, the information carried by that connection is going to degrade the signal. Personally, I would never split a cable that carries audio information.

[jlafrenz]

animo... just curious as to your reasoning behind never splitting an audio signal. From what I understand it is just a low voltage signal and splitting it should not really be a problem. Though there would technically be a loss it should not be noticeable. Also, the Emotiva gear typically sends out a stronger signal than other gear. Just looking for some insight from your well versed history in the audio world.

[nicholas322]

I had explained this previously.
there are 2 problems.
1 you may overdrive the preamp as it is an amp!
check with the manufacturer to see if you can do it.
2 there will be no sonic benifit!
proper bi-amping requires an active crossover before the amps so the amps do not carry the entire frequency range. They will be cleaner.
Unless you have wilson grand slams or larger power hungry speakers there will be no sonic benifit of using the y jack.
if youre the guy with the polks your asumption on biamping based on 2 pairs of jacks is wrong. The jacksare there for bi-wiring.
you can mix and match 2 sets of cable or run 2 identicle pairs.
This will be my last pot on the BI-amp situation.

[jlafrenz]

I would have to disagree with you that there is no sonic benefit. I do think that each situation is different. I did notice a difference in my setup when I passively bi-amped. I know the argument that will be made is that it can't be proven and it won't show on paper or test equipment. Some may also say that it is only tricking the mind. Either way, I hear something different so I feel that it is worth it.

[Animo]

Everything here is basically subjective. If you hear a difference and it is to your liking, then all well and good. I am just of the belief, that anytime you split anything, the quality will be affected. As you yourself pointed out, it might not be measurable sonically or on paper, but I still believe it occurs.

[RadTech]

What happened to the fun of experimenting and enjoying your equipment. To each his own and if anyone wants to try different configurations by all means do so. It is truly a subjective experience and what might seem like the smallest difference to one is a vast improvement to another. You may be technical right but, it doesn't mean that is the final word on the subject. Many people on this forum are using or considering passive bi amp configurations and should feel free to discuss it regardless, if there is evidence of a benefit or not.

[jlafrenz]

I think everyone here is discussing it openly and trying not to discount others ideas. We are all speaking from our own experiences. Animo summed it up spot on. Radtech you are also right about saying something is technically right or better, but that is not the whole story.

[tjf120]

Interesting....I was thinking of adding an XPA-2 or a couple XPA-1's....that would allow me to bi-wire or bi-amp with my XPA-5.......

One thing I find interesting....Emotiva put binding posts on the XPA-1 for bi-wiring...but I guess you have to have a product for all types of consumers.......

[samco]

what is it called when u use the a and b terminals from one amp 2 power the mids n woofer ?

ergo 1 amp pr speaker but 2 seperate speaker wires 2 the mids n woofer from a n b terminals?

[CiXel]

Bi-Wire

[samco]

oki thanks 8) on a 8ohms speaker would this become a 4ohm load for the amp or 8ohm?

[handree]

There seems to be a lot of confusion.

Normally a speaker has a passive cross-over that contains
coils, resistors and capacitors. You can run 1 set of wires
to the speakers. If you run 2 wires then you usually have a lower
resistance and thus can have a small improvement in the sound.
In essence not much different then running a thicker
gauge wire.

When you go a step further and add an amplifier per wire you have the advantage that the amplifiers limit the effects of the various
cones on each others. A woofer because of inertia can generate an
electrical signal that may affect other drivers.
This effect is small because it's reduced by the passive filter in the speaker. However if you add separate amplifiers this effect becomes really non existent.

However some speakers may rely on the one driver drawing current from the other drivers for the cross over slopes. Thus
the cross-over tuning may be altered by bi-amping.

The third option is active cross-over. This can be achieved
with opamps or digitally. This allows the designer to remove the
cross over and reduce the effects of large coils and caps in the
speaker. This can only done by returning the speaker and
requires measurements and expertise. I doubt you will get
a good result if you leave the passive cross-over in place.

Personally I'm tri-amping my home build speakers with a pair
of XPA-3s. This gives a wonderful sound. I had an issue
when I hooked it up as the XPA has an input protection that
recognizes shorting of the inputs with other inputs. This
was solved by putting 1k resistors in the signal path between the various inputs.

It's true that theoretically you can overload a pre-amp by bridging
the output. Since most solid state pre-amps have an output
impedance of 50 ohms or less and most inputs are in the 10k or
higher this is seldom the case. Be aware of some tube amplifiers.

If you think this is going to be a problem a buffer stage may be
added to match the impedance.

My next steps are going to switch to active cross-overs.
This is another significant expense. I would like to use digital
cross-overs but if the AD-DA stages in the digital cross-overs
are poor the sound will be degraded.

I would love for Emotiva to develop a product that uses a digital in.
I would like to hook up the digital output of the processor.
Preferable you could select any of the multi channels of a home theater. Then depending of the output I would like to split the
signal in the various frequency bands. I would want:
24 db/Slope Linkwitz Riley filters. Time delay correction. Bass equalization (Although the processor already give that). Selectable 2-3 or 4 ways (I think 6 channels out per chassis is reasonable so
for 4 ways I could buy multiple chassis). High-end DA converter.
Have balanced output so my XPA-3s can get minimal noise
input.

[Animo]

Handtree,

that was a very lucid and well thought out first post.
Welcome to the land of Emotiva.

When I built my speakers 11 years ago, I had designed them with a passive crossover in a separate cabinet. There are binding posts on the speakers to enable bi or tri-amping them, by simply disconnecting the jumpers. Then I could add an outboard electronic crossover to do all of it's magic. Do I do this? Nope.

I like the K.I.S.S. method, and use one speaker connection (cable) per channel from my amps.

[jedinite24]

Check this out. The replies from Scottl and Themanthatisi are my favs.

emotivalounge.proboards.com/index.cgi?board=stupid&action=display&thread=8274&page=1