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Please explain bi-amp crossover to me

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Posted on February 21, 2017 at 14:57:12
Raymond Leggs
Audiophile

Posts: 748
Joined: November 25, 2007
 Please explain the biamp crossover to me some speakers have dual binding post, but wound that be connected to the same crossover? I know some cheap off brand speakers will tie together the four terminals internally with a wire bridge (eekers!).

 

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RE: Please explain bi-amp crossover to me, posted on February 21, 2017 at 15:06:40
MannyE
Audiophile

Posts: 2088
Location: Miami Beach
Joined: March 4, 2001
 Not sure what you're worked up about. (really)

Some speakers have two (or three) binding posts so they can be passively bi-amplified. After you remove the jumpers, you amplify each stage but depend on the internal crossover to route the signal. I have done this and it resulted (to me...and no one else because audiophilia is a lonely existence generally) in an improvement in the sound.

Active bi-amping would mean that the internal crossover is by passed by getting into the insides, cutting out the internal crossover and wiring each component directly to the available posts, or even more annoyingly, modifying the speaker so that each driver has it's own posts, then adding an external crossover and amplifying each component with an amp that's installed BEHIND the external crossover.

I have read and been told that it's one of the components of reaching audio Nirvana.

Maybe one day I will find out but at the moment I have to go listen to some music.

 

bi-amp crossover to me, posted on February 21, 2017 at 15:35:10
bare
Audiophile

Posts: 1879
Joined: April 14, 2009
 Biamp capable speakers were (are?) a sop to marketing.
It's Cheap and easy to add during manufacturing and this makes Speakers look more upscale than they actually are.
Remove the bits of metal connecting the bind terminals and you can run individual wires and /or Amps to the HF and LF crossovers and thereby the drivers. Helpfull IF yer amps are substandard to the power needs of the speakers
Some claim this all makes audible difference, but then Some buy penis pills too :_)
Your $$, your choice.
Active is where crossovers (either.. self powered $$ OR passive $) are placed Before amplifiers to select out frequencies so the Amps need only deliver specific frequency ranges.
Yesss this works/improves... period. Allowing full 'unmolested' Amp power delivery directly to the drivers.
However it's Dependant on the quality of the Speakers and their inbuilt crossovers, that are being bypassed.
Silk purses and sows' ears comes to mind.
Tricky to setup ..Well.. and best done when Amps are identical otherwise tonal /balance matching is a 'problem'

 

RE: Please explain bi-amp crossover to me, posted on February 22, 2017 at 07:09:37
SpotcheckBilly12345
 This method of "bi-amping" is often called "fools bi-amping" in many audio circles. Google is your friend ;-)

Cheers,
SB

 

RE: Please explain bi-amp crossover to me, posted on February 22, 2017 at 13:07:30
neolith
Audiophile

Posts: 4842
Location: Virginia
Joined: February 21, 2002
Contributor
  Since: December 2, 2004
 Speaker level biamping is, to me at least, a bit of a gimmick. The advantages are probably the same as biwiring, which I also find somewhat dubious. Obviously, there are many others who disagree. So be it.
Here is a diagram of a normal simple crossover and the equivalent biamp arrangement. If you follow the signal from the "positive" input it splits - one part goes through a capacitor (high pass filter) to the tweeter and returns to the negative post. The other part goes through the inductor (low pass filter) to the woofer and again returns to the negative post.
With the biamp setup, one amp supplies the woofer and the other the tweeter so the two speakers are electrically separate. However they both are receiving identical signals and just rejecting the "unused" portion. In fact there is no "crossover".






"Our head is round in order to allow our thoughts to change direction." Francis Picabia

 

RE: Please explain bi-amp crossover to me, posted on February 23, 2017 at 10:25:05
Presto
Audiophile

Posts: 5957
Location: Canada
Joined: November 10, 2004
 In the name of being a career contrarian... ;)

There is potential merit to passive bi-amping because although each amp is applying a full-range signal to each network, the networks "complex impedance" is what will determine the current that flows in each amplifiers output stage.

Common wisedom says the voltage *AND* current will be the same in each branch, but this is not the case.

So, what you have is one amp "seeing" only woofer current and one amp "seeing" only tweeter current. Since bass is more current-intensive, it can drag down the DC rail voltage of the amp, especially if the damping factor is relatively low. So, this could potentially improve the situation for the "tweeter circuit amp". Also, too, you can mess with different speaker wires for each circuit. You can use a higher-power high-strand-count low impedance cable for bass, and then get away with a nice "fine wire" ribbon or silver-wire "guitar string" design for the tweeter (if your particular denomination of audio beliefs include room for 'time smear' in speaker cables!)

But, in agreement, you're not gaining anything power wise. Amp1 sees 'Current A' and Amp2 sees 'Current B' where a single amp simply sees "Current A+B".

The point of my post is to point out that although the voltage output of the amps will be full range, the currents will be different, and this can have a bearing on over-all amp performance. Amps store energy (large capacitors) so they provide some isolation from one another depending on the damping factor of the amp and the "stiffness" of the power source.

People have claimed they have had success by improving the branch circuit conductors from the panel to the audio room. Others have gone further and had the incoming cables to their home upgraded. With electrical sources, stiffer is better - especially when you start talking about current surges associated with higher-power bass applications. My friend's 2000W RMS sub amp likely dims house lights in a 1-block radius! ;)

Cheers,
Presto

 

RE: Please explain bi-amp crossover to me, posted on February 23, 2017 at 13:41:21
BigguyinATL
Manufacturer

Posts: 3475
Joined: April 10, 2002
 The article discribes the benefits of biamping and compares with bi wiring.

Quick Summary
Bi-wire one amplifier channel driving a loudspeaker with High Pass and Low Pass passive crossover separated at the loudspeaker terminal.
Little or no benefit based on the wire gauge used - unless you are susceptible to perceptual bias (we all are).

Biamplified with Passive crossovers in loudspeaker. Two identical amplifiers (or two different amplifiers adjusted to similar gain) driving separate HP and LP sections. The measured output of the loudspeakers may differ a little based on the charateristics of the amplifier (mostly output impedance as a function of frequency) No real benefit of Dynamics or distortion as a Electronic Crossover biamp - Next and best Choice.

Line Level crossover biamplified system Separated the low pass and High pass signals before they enter the amplifier. This crossoverr replaces the passive crossover functionality in the loudspeaker - though protective passive components (capacitors and varistors) might (and should) be employed in the loudspeaker. Sometimes the amplifiers and crossovers are built into the loudspeaker (low cost PA speakers and low to high cost Monitor speakers), other configuration use crossover as part of the input circuitry of the amplifier (Common in PA systems), or a completely separate crossover (Analog, DSP or Passive) separating the HP and LP signals before they enter the amplifiers driving its perspective system. The amplifiers for this type do not have to be matched - and infact be optimized for its roll in driving the load (woofer, midrange or tweeter.
An active subwoofer is the most common of "biamp" system where the low frequencies are directed to the sub's amplifier.

See the article below for all the advantages of Biamping.

The main reason for not biamping is marketing, complexity and perhaps overall price.

A small monitor like a JBL LSR305 is a $300/pair biamplified system with Two 56 Watt Class D amplifiers driving a Waveguide tweeter and an 8" woofer. Because the internal passive crossover splits and EQ's the system and also protects the drivers, the output and response is remarkable for the price. (though obviously cost limits the overall cabinet as driver quality) With the Crossover at a high 1800 Hz the LP amp is still carrying most 70% the voltage swing on typical music signals, but that still makes that 43 watt amp perform like one with twice that much power. And the active crossover can allow the drivers to be phase aligned and you don't have inductors adding their voltage drop and distortion.
http://noaudiophile.com/JBL_LSR305/





"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius

 

RE: Please explain bi-amp crossover to me, posted on February 23, 2017 at 13:51:06
neolith
Audiophile

Posts: 4842
Location: Virginia
Joined: February 21, 2002
Contributor
  Since: December 2, 2004
 I tried to follow your argument about current but Kirchoff keeps getting in the way. Assume the same complex signal is fed to both amps and the amps generate an augmented signal with current i and voltage v. The current returning to the amp will be -i (the sum of the currents at a node is zero) . This is true for both amps - the current flowing through the speakers will be the same (assuming the amps are identical).In the case of the low pass the voltage Vamp= Vind + Vwoof and for the high pass Vamp=Vcap + Vtweet. So while the voltage drop across the speakers is different the total voltage drop is the same for both circuits. And as you said, there is no power gain beyond the sum of the two amps.
With home electrical circuits, the advantage from isolated lines comes from 1) less interference from other elements in the home 2) less resistance in the circuit due to heating of the wires and less Johnson noise. However for the most part (ignoring the wire resistance issue), the current and voltage delivered is the same.



"Our head is round in order to allow our thoughts to change direction." Francis Picabia

 

I'll be happy to., posted on February 23, 2017 at 15:58:26
Inmate51
 Right after you get your act together and get a job.

http://www.audioasylum.com/cgi/vt.mpl?f=general&m=723930

:)

 

Exactly. (nt), posted on February 24, 2017 at 09:06:07
bouncy ball
Audiophile

Posts: 1221
Location: British Columbia
Joined: July 26, 2003
 .

 

Vandersteen, posted on February 24, 2017 at 10:45:44
Bill Way
Audiophile

Posts: 1884
Location: Toms River NJ
Joined: May 28, 2012
Contributor
  Since: December 14, 2012
 I think Richard Vandersteen got it right: bi-amping makes a pretty dramatic improvement in low-level detail, as does bi-wiring. But he found that bi-wiring only worked when the wire pairs were kept separated by an inch or two for most of their run. I found a somewhat abbreviated version of his original paper on this - see link.

In the original paper, he wrote of hearing improvements in low-level detail with bi-amping. Then he made up two amplifiers with a single pair of outputs - two power supplies, two input sections, two output sections linked to a single pair of terminals. No improvement. He tried bi-wiring with the wire pairs in a common sheath, and heard no improvement. When he separated the wire pairs, he heard an improvement. Using a Hall effect meter to measure the magnetic field generated by the current in the wire pairs, the level of the field was much greater for the woofer pair than the tweeter pair. As the inverse of the Hall effect also applies, i.e. that the magnetic field around the wire pair can affect the current, he concluded that was what was going on.

To the OP's original post, the crossover of a two-way speaker consists of a circuit with two branches: one with a high-pass filter going to the tweeter, and the other with a low-pass filter going to the woofer. Connecting the branches via the jumper wires at the terminals gives you the option of using the speakers mono-wired. BTW, it's not something on "cheap speakers," and that couple inches of wire is not something to go "eekers" about. There's lots more wire inside the box, and lots more connecting the speakers to the amplifiers, so I don't think the couple inches of jumper wire is something to get overly concerned about.

Many people don't buy Vandersteen's explanation, but some who do are often worth listening to. When I sent pics of my modified-for-biwiring Spica TC-50 crossover boards to John Bau, he agreed it should make a big improvement, though he thought it was due to ground plane interactions more than Hall effect.

BTW, there is an easy way for many of you to test this. If you are set up for bi-wiring with the wire pairs in a common sheath, cut the sheath off, separate the wires by an inch or two, and let us know if you hear any difference.

Some day we actually might get this figured out.

WW
"Put on your high heeled sneakers. Baby, we''re goin'' out tonight.

 

RE: Vandersteen, posted on February 24, 2017 at 12:25:35
Inmate51
Vandersteen. Lots of words but no data.

:)


 

Many better ways to get to audio nirvana..., posted on February 24, 2017 at 18:37:49
kSpace
Audiophile

Posts: 191
Joined: July 12, 2002
 If the speaker designer really thought bi-amping was better, then they wouldn't waste money on the crossovers and filters in the speaker and just run wires from the terminals to the drivers. If you look around, you won't see a huge market for external crossovers. It's a niche product for enthusiasts to try to out perform speaker designers.

I have never heard a difference with bi-wiring and my limited experience with passive bi--amping was a relative sonic disaster. The best sound I have achieved is with high quality speaker cables connected to the Low Frequency terminals with the stock jumper plates b/w LF and HF posts. I found a used pair of Nordost Heimdall 2's that did the trick for me!

Cleaning up your power supply and getting the best source material and components will get you there a lot faster.

My 2c

 

RE: Vandersteen, posted on February 26, 2017 at 08:08:43
goheelz
Audiophile

Posts: 167
Location: Southeast USA
Joined: December 17, 2002
 So where exactly do you disagree with Vandersteen's ideas about bi-amping?

 

Conditional replying?, posted on February 27, 2017 at 17:35:01
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 linky no worky no more either but why do you give a shit if he is working or not? You act like the employment police now. He just asked a question he didn't say he was going to buy anything since you are his lifecoach now evidently.




ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: Vandersteen, posted on February 27, 2017 at 19:00:53
bare
Audiophile

Posts: 1879
Joined: April 14, 2009
 Once thought Vandys were Outstanding. Then.. Lived with some.
They Aren't.. Period.
Emperor's clothes IMO, is an honest descriptor.
No One should care what Vandersteen claims.. these days.
His 15 mins of fame is OVER.. adapt to the 21st century reality.

 

Were you looking for an intelligent exchange?, posted on February 28, 2017 at 12:11:39
Craiger56
Audiophile

Posts: 5574
Location: San Jose CA
Joined: April 3, 2002
Contributor
  Since: December 29, 2003
 Me too

 

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