Bridging or Bi-amping? That is the question.

[zumbo]

Seing that many people are bridging a pair of 2-channel amps on their mains got me to thinking. Wouldn't it make better use of those to bi-amp.

 

[mulester7]

Seing that many people are bridging a pair 2-channel amps on their mains got me to thinking. Wouldn't it make better use of those to bi-amp.

....Zumbo, in the realm of voices with two amps strapped, the mains are getting hit with strapped-amp bullets for an authoritative voice and better low end....try all possibilities though, whoever paid for the stuff......

 

[PENG]

By bridging the 2 channels, you get more power on demand for the bass drivers. If you bi-amp, only the power of one amp is available for the same bass drivers.
Further, to get full benefits of bi-amping, you need to do more with your crossover system (some call it active crossover).

Zumbo brought up an interesting point though, depending on the rest of your system, e.g. efficiency of speakers etc., bi-amping may give you better clarify if your bass drivers are highly efficient and don't benefit much from having more power.

Another option I see is to bridge the 2 channels and bi-wire your speakers. Many, including Audioholics I assume, (there is an article on their site) claimed that bi-wiring is meaningless as the wires are still connected together at the same amp's terminals. Others (me included) would argue otherwise, to me bi-wiring still makes a difference electrically because the speakers crossovers are split once you remove the strap, therefore each part of the crossover will present a different frequency/impedance characteristics to each pair of the wires. IMHO unless you have an active crossover system, bi-amp or bi-wire makes very little difference, if the equivalent power output is the same. Sorry I am digressing from you point.

One last point, apparently the jury is still out for the benefit of even true amping (with active XO), as people are still arguing about the pros and cons.

 

[zumbo]

What about the fact that each amp will have all of it's power concentrated on a smaller frequency range in a bi-amp set-up using the amps internal crossover for a cleaner more dynamic sound? If you need more power, just buy the larger amp.

Ashly FTX-1501/2001

Two-Way Crossover
The crossover input option provides fixed-frequency 24 dB/
octave high-pass and low pass filters allowing the two amplifier channels
to operate bi-amped, full range with low out, both channels low
out, or bridged low out. Auxiliary low and high outputs are available
for connecting additional amplifiers. Included with the crossover input
option are single in-line package (SIP) resistor networks which allow
preselection between standard crossover frequencies of 160Hz,
500Hz, 750Hz, 1.2KHz, and 1.6KHz. 360° of phase control is provided
for proper acoustical alignment of high and low frequency drivers.
Selectable constant directivity horn EQ is provided for both small
and large horn designs.

 

[PENG]

What about the fact that each amp will have all of it's power concentrated on a smaller frequency range in a bi-amp set-up using the amps internal crossover for a cleaner more dynamic sound? If you need more power, just buy the larger amp..

Absolutely, if you buy the larger amp, then power is not the issue. Otherwise, my point is, bass drivers typically could draw (obviously depend on the source material) much more power than the mid and high frequency drivers combined. As to "using the amps internal crossover. Amps don't have internal XO's, not that I am aware of. Just checked out the Ashly you cited, its a 2-channel amp, no internal crossover, right?

Receivers have internal crossovers but while they can set different XO points for front, centre, rears etc., they do not have the capability of setting different XO points for each individual channels.

 

[zumbo]

Page 11-8.3
http://www.ashly.com/manual/fx7man.pdf

This is also an available option with these amps.
http://www.ashly.com/product/powercard.htm

 

[PENG]

Page 11-8.3
http://www.ashly.com/manual/fx7man.pdf

This is also an available option with these amps.
http://www.ashly.com/product/powercard.htm

Read it, thanks, I should have known better you were onto something interesting!

 

[mtrycrafts]

.
Further, to get full benefits of bi-amping, you need to do more with your crossover system (some call it active crossover).

One also needs to bypass the passive crossovers and opening the cabinet is needed for this.

Others (me included) would argue otherwise, to me bi-wiring still makes a difference electrically because the speakers crossovers are split once you remove the strap,

In a buy-wireable speaker, the crossover is already split behind those terminals inside the speaker. The strap will not cause it to split or not. Look at it as if you are just extending that strap to the amp. Or, if you replace that strap with a longer wires, same length as the speaker wire, then just moving it to the speaker, nothing has changed as far as the crossovers are concerned.


therefore each part of the crossover will present a different frequency/impedance characteristics to each pair of the wires.

All you are doing here is reducing the wire resistance by 1/2. Not an issue.


One last point, apparently the jury is still out for the benefit of even true amping (with active XO), as people are still arguing about the pros and cons.

The experts are not arguing.

With an active crossover, you are not at the mercy of a passive crossover and those issues; you can design circuits that have much better, sharper crossover characteristics, eliminating two different drivers from reproducing the same sounds, etc.

 

[mtrycrafts]

What about the fact that each amp will have all of it's power concentrated on a smaller frequency range in a bi-amp set-up using the amps internal crossover for a cleaner more dynamic sound? If you need more power, just buy the larger amp.

I think you are forgetting that the tweeters get very little power to begin with. Much of the tweeters in speakers have low power handling capability. Your ears are much more sensitive to those frequencies as well, hence less need for power. Most amps are rated at full spectrum, RMS, so that is not an issue.

 

[zumbo]

I think you are forgetting that the tweeters get very little power to begin with. Much of the tweeters in speakers have low power handling capability. Your ears are much more sensitive to those frequencies as well, hence less need for power. Most amps are rated at full spectrum, RMS, so that is not an issue.

But, for me it's more along this line.

With an active crossover, you are not at the mercy of a passive crossover and those issues; you can design circuits that have much better, sharper crossover characteristics, eliminating two different drivers from reproducing the same sounds, etc.

I would seperate a mid & tweeter on one amp, and a dedicated mid-bass with the other in my 2 & 1/2 way speaker.

 

[PENG]

One also needs to bypass the passive crossovers and opening the cabinet is needed for this.

You're right, I should not have omitted this point.

In a buy-wireable speaker, the crossover is already split behind those terminals inside the speaker. The strap will not cause it to split or not. Look at it as if you are just extending that strap to the amp. Or, if you replace that strap with a longer wires, same length as the speaker wire, then just moving it to the speaker, nothing has changed as far as the crossovers are concerned.

Not exactly true, although the crossover is already split behind those terminals, the straps are causing the "split" crossover to be seen by the circuit that starts from the amp's speaker output terminals to the binding posts as one network, that is, not split. So the amp terminals will send the signals down this path, no matter how many pair of wires, according to the combined/equivalent impedance of both of the LF and HF XO circuits.

Once you remove the straps, each pair of the wires (bi-wire) will be able to see the individual LF & HF crossover circuits separately. You are right about "nothing has changed as far as the crossovers are concerned", but to the wires, it is different when the straps are removed. Think about it, if the straps are not removed, electrically the situation would be just as you described, i.e. like extending the straps to the amp's terminals, and I may add, it would also be like extending the straps to the HF & LF XO's terminals (i.e. effectively still joining the two XO's. With the straps removed, and using two pair of wires, the amp's output terminals now clearly see two separate paths, one goes from the amp to the LF driver's XO (impedance A), and the other goes from the amp's same terminals, but to the HF's XO (impedance B). With no linkes in between! Now, impedance A (LF drivers) has the characteristics of a low pass filter, so it would tend to block HF signals. Likewise, impedance B (HF drivers) would block LF signals. So in bi-wiring, each pair of wires will carry its own intended band of frequencies, as opposed to the full spectrum of frequencies flowing down the same pair (or pairs regardless of how many) of wires. Whether that would improve the sound we are able to hear is a separate argument. I am only trying to back up the claim that there is a difference electrically.

I have read about many claims that there is no electrical difference but none offer any valid argument that is based on electrical theory. I wish people would sit down, draw out a simple electrical circuit diagram, and then apply the theory. All it takes is Ohm's law, Kirchoff's law, basic series/parallel circuit theory and maths. Some understanding of the impedance characteristics of XO/filters will help. That said, I did read about one article (linked by an article named "the ten audio myth....or something like that) where someone attempted to prove bi-wiring makes no difference, and yes he included a diagram and some forumla, but it's presentation was so confusing that I have no idea what he was doing. Unfortunately articles like that ended up misleading people.

therefore each part of the crossover will present a different frequency/impedance characteristics to each pair of the wires.

All you are doing here is reducing the wire resistance by 1/2. Not an issue.

This is not correct. See explanation above.

One last point, apparently the jury is still out for the benefit of even true amping (with active XO), as people are still arguing about the pros and cons.

The experts are not arguing.

You may be right about this one, it depends on who we consider as "experts", I can post a link or two of those arguments if you wish.

With an active crossover, you are not at the mercy of a passive crossover and those issues; you can design circuits that have much better, sharper crossover characteristics, eliminating two different drivers from reproducing the same sounds, etc.

Again, you may be right, I, for one believe in the alleged benefits of both bi-wire and bi-amp. I have enough amps to bi-amp, but I only bi-wire for now. To me, there are too much to do to bi-amp properly. And as far as I am concerned, a 200WPC bi-wired system is pretty much as same as a 100WPC bi-amped system, unless you are prepared to go the active XO (yes, in that case, disable the passive XO's in the speakers) route.

Zumbo, sorry I know this is not your question. If Mtry wants to debate further, we should start a separate thread.

 

[zumbo]

Again, you may be right, I, for one believe in the alleged benefits of both bi-wire and bi-amp. I have enough amps to bi-amp, but I only bi-wire for now. To me, there are too much to do to bi-amp properly. And as far as I am concerned, a 200WPC bi-wired system is pretty much as same as a 100WPC bi-amped system, unless you are prepared to go the active XO (yes, in that case, disable the passive XO's in the speakers) route.

Zumbo, sorry I know this is not your question. If Mtry wants to debate further, we should start a separate thread.

Not a problem. I appreciate the knowledge that both of you bring to the forum.

 

[mtrycrafts]

Not a problem. I appreciate the knowledge that both of you bring to the forum.

Everyone learns, including myself That's why we are here, no?