Bi-amping

[racinoffrd]

I have a few questions about bi-amping that I would like to ask but don't know where to go. Can anyone help?

[hjames]

I have a few questions about bi-amping that I would like to ask but don't know where to go. Can anyone help?

Ask away - a number of folks here have gone down the biamp path over the years ...
Give gear and specifics for the most helpful answer!

[racinoffrd]

My questions are pretty generic but anyway I have two Soundcraftsmen Pro Power Fours for amps and Cerwin-vega PD-9s which can't be bi-amped without mods I think. I have looked everywhere and all that I can find. I still must be looking in the wrong spots or I'm not reading it correctly. But anyway I can't find the info.. I'm looking for. I would like to get some speakers that I can bi-amp. Maybe JBL L890s. But my questions are what happens with the wattage that is supplied, how does bi-amping effect the impedance, and the sensitivity of the speaker?

[Fort Knox]

My questions are pretty generic but anyway I have two Soundcraftsmen Pro Power Fours for amps and Cerwin-vega PD-9s which can't be bi-amped without mods I think. I have looked everywhere and all that I can find. I still must be looking in the wrong spots or I'm not reading it correctly. But anyway I can't find the info.. I'm looking for. I would like to get some speakers that I can bi-amp. Maybe JBL L890s. But my questions are what happens with the wattage that is supplied, how does bi-amping effect the impedance, and the sensitivity of the speaker?

You need to deside whether to locate your amps at the speaker and run preamp lines back to your elect/xover (rack)
or....run speaker lines ..instend ..from a rack mounted amp...out to the sp....this makes a diff. in pwr vs. noise
Meanwhile .... type in "Bi-amp connection diagram" on your browser ......and a whole world of info will pop-up

[fpitas]

One thing I point out to bi-amp newbies is that those passive networks you're bypassing may have EQ functions. That's very common in JBLs, and many other speakers where the designer cares about frequency flatness. As long as the electronic crossover you're using has EQ available for each driver, that's no problem.

[BMWCCA]

The basic question you should as is "why". If you have yet to select speakers you want to do this with then you may be on a track to accomplish nothing but spending money, introducing new cable runs, and possibly increasing your noise floor.

If you decide to proceed anyway, you not only need to determine your speaker needs but also what you'll be using as your active crossover.

I'm using a 4345 pair with the Ashly XR1001 and Crown PS400 and PS200 amos. The 44xx series JBLs designed for bi-amping are obvious choices and much has been written here about how they improve through bi-amping if for no other reason than the bi-passing of the bi-amp selector switch. My next step toward Nirvana, according to the designer, would be to tri-amp to get the UHF on their own amp and off the passive network.

A never-ending process but as long as I can stop along the way to just listen to the music, I'm a happy guy.

[Fort Knox]

My next step toward Nirvana, according to the designer, would be to tri-amp to get the UHF on their own amp and off the passive network.

A never-ending process but as long as I can stop along the way to just listen to the music, I'm a happy guy.

I unsucsessfully tryed the Tri-amp thing w/075/2445/2380...and a Samson 4 way w/time align. stuff
Seems the (two) mid/highs would always fight for supremacy...w./no middle ground.....

[Robh3606]

I would like to get some speakers that I can bi-amp. Maybe JBL L890s. But my questions are what happens with the wattage that is supplied, how does bi-amping effect the impedance, and the sensitivity of the speaker?

Hello racinoffrd

There are 2 ways to biamp speakers. The first and easiest is leaving the original networks in place and run 2 amps for each speaker without an active crossover. This is called passive biamp and there are many speakers out there that have the networks separated and have 4 binding posts already there to do this. All come with straps that short the 2 pairs of inputs.

Don't assume any speaker with two set's of binding posts falls into this category. You need to check the owners manual or the schematic to see if the crossover sections are actually isolated. Many speakers are sold with 2 set's of posts so they can be bi-wired which is not the same thing. Bi wiring is 2 sets of wires from the same amp so electrically the crossovers are connected.

The other way to biamp is using an active crossover. This is the only way to biamp if you are a purist and want to get the most benefit to the system. Very few speakers are available that are ready to biamp this way. You would need an active crossover ready to go from the manufacturer. Without that you would need to do modifications to the speakers crossovers. Not for the faint hearted.

As far as your question it depends and there are no easy answers. It can vary from system to system depending on how things are hooked up and how much of the original crossover is left in circuit.

Rob

[racinoffrd]

I don't know... I was just thinking of bi-amping because I have read some much good about it but it sounds like I would be opening a whole new can of worms. I don't know if I will never do it. It sounded much earlier when I was reading about it. If I never did I would run cables to the speakers since I already have the amps mounted in the rack. I was wondering how it would work with the xovers if the speakers came with the dual binding posts. It sound like you would still need xovers from the LFD to the Mid/HFD or am I wrong? When you bi-amp does it automatically bypass the Xover from the LFD to mid/HFD? There seem to be too many questions to do this. I am still enterested on what this does to wattage and impedance?

[Fort Knox]

I don't know... I am still enterested on what this does to wattage and impedance?

I'll tell you what it does...your no longer dealing with wimpy little passive filters eating up and dividing amp power..
a whole amp channel grips one voice coil...and... damping is "off the charts' ,,,..mult. amps can produce violent razor
sharp sound...production ...with no top end..

[grumpy]

It sound like you would still need xovers from the LFD to the Mid/HFD or am I wrong?

You still need crossovers somewhere... this can be external (pre-amp level), or passive (built into the speaker
cabinet), -OR- a combination of both ... the latter being fairly normal.

When you bi-amp does it automatically bypass the Xover from the LFD to mid/HFD?

There's nothing automatic about it. The speakers are designed to be used in biamp mode (external LF/MF
crossover), or designed to allow (switch or straps) for biamping in active or passive mode (as others
have described), or they are not. It should be -quite- explicit in the user manual if any type of biamping
is available without modifying the speaker system.

There seem to be too many questions to do this.

Go multi-channel and use the other amp channels

I am still interested on what this does to wattage and impedance?

First, note that nearly all audio amplifiers produce voltage... the wattage used is determined
by that voltage (and amplifier current limitations... if reached) -AND- the speaker impedance ...
which often (usually) varies significantly over frequency.

When you disconnect the LF portion from the rest of the speaker system, and leave the passive
crossover elements in place (passive bi-amping), the LF amplifier will see essentially the same
impedance over the speaker's LF nominal range (perhaps 0-300Hz) and the LF driver will absorb
the same wattage as before in that frequency range. The LF crossover "blocks" higher frequencies
usually by using components (capacitor, in a simple case) that generally increase in impedance
with rising frequency. A crossover can also "divert" energy in a particular frequency range from a
driver by shunting it to ground, but feel free to ignore this detail for now

If you assume that most musical energy is in the LF range, the amp providing
voltage to the LF section will not see much difference in watts that are absorbed
by that part of the speaker. And much less of the HF voltage will be "converted" to watts
as the LF crossover impedance will be much higher in that range (less current).

The same thing happens with the high pass section... it "blocks" low frequency
energy by using components that increase in impedance as frequency gets lower.
So the "HF" amplifier (which really sees exactly the same input spectrum, and puts
out the identical output voltage over frequency in a passive biamp arrangement)
also sees a higher impedance at lower frequencies, and therefore (on average)
doesn't need to supply nearly as much current. Short-term voltage range may still
need to be the same, but the amplifier's current capability may not need to be
as ... robust. Using identical amplifiers is the most straightforward and a good
place to start. A caveat is some more esoteric amplifiers may not be happy driving
a very high impedance (likely to be seen in passive bi-amp arrangements, but
this is less of a problem than amplifier requirements for some systems that have
very low-impedance/high phase angle points in their operating range). Most
normal/modern/solid-state consumer amps should be fine. I should stop here...

[Fort Knox]

You still need crossovers somewhere... this can be external (pre-amp level), or passive (built into the speaker
cabinet), -OR- a combination of both ... the latter being fairly normal.


There's nothing automatic about it. The speakers are designed to be used in biamp mode (external LF/MF
crossover), or designed to allow (switch or straps) for biamping in active or passive mode (as others
have described), or they are not. It should be -quite- explicit in the user manual if any type of biamping
is available without modifying the speaker system.


Go multi-channel and use the other amp channels


First, note that nearly all audio amplifiers produce voltage... the wattage used is determined
by that voltage (and amplifier current limitations... if reached) -AND- the speaker impedance ...
which often (usually) varies significantly over frequency.

When you disconnect the LF portion from the rest of the speaker system, and leave the passive
crossover elements in place (passive bi-amping), the LF amplifier will see essentially the same
impedance over the speaker's LF nominal range (perhaps 0-300Hz) and the LF driver will absorb
the same wattage as before in that frequency range. The LF crossover "blocks" higher frequencies
usually by using components (capacitor, in a simple case) that generally increase in impedance
with rising frequency. A crossover can also "divert" energy in a particular frequency range from a
driver by shunting it to ground, but feel free to ignore this detail for now

If you assume that most musical energy is in the LF range, the amp providing
voltage to the LF section will not see much difference in watts that are absorbed
by that part of the speaker. And much less of the HF voltage will be "converted" to watts
as the LF crossover impedance will be much higher in that range (less current).

The same thing happens with the high pass section... it "blocks" low frequency
energy by using components that increase in impedance as frequency gets lower.
So the "HF" amplifier (which really sees exactly the same input spectrum, and puts
out the identical output voltage over frequency in a passive biamp arrangement)
also sees a higher impedance at lower frequencies, and therefore (on average)
doesn't need to supply nearly as much current. Short-term voltage range may still
need to be the same, but the amplifier's current capability may not need to be
as ... robust. Using identical amplifiers is the most straightforward and a good
place to start. A caveat is some more esoteric amplifiers may not be happy driving
a very high impedance (likely to be seen in passive bi-amp arrangements, but
this is less of a problem than amplifier requirements for some systems that have
very low-impedance/high phase angle points in their operating range). Most
normal/modern/solid-state consumer amps should be fine. I should stop here...

This explaination vividly explains why pwr robbing filters should be located up-stream
so the bi-amps' free..... (w/pwr saving Band pass freqs)....to run a VC direct coupled..

[Fort Knox]

My next step toward Nirvana, according to the designer, would be to tri-amp to get the UHF on their own amp and off the passive network.

A never-ending process but as long as I can stop along the way to just listen to the music, I'm a happy guy.

I turned on to Nirvana...Live..Paramount 91..Thanks
Sounds like Live!!

[racinoffrd]

Thanks guys for the explanations. There was a lot I was wondering about bi-amping. Right now I have two of the same amps bridged. I think I might try bi-amping to see how it sounds since I have two of the same amps. But I need to get Y-interconnects first. Them there will be questions about Xovers.

[hjames]

Y-connects? Where would they go in the system?
I biamped my JBL 4 ways with the Ashly active crossover (much like BMWCCA) and never used Y connects ...

Thanks guys for the explanations. There was a lot I was wondering about bi-amping. Right now I have two of the same amps bridged. I think I might try bi-amping to see how it sounds since I have two of the same amps. But I need to get Y-interconnects first. Them there will be questions about Xovers.