Impedance - biwiring/biamping/series/parallel

[splasher]

So I've come to a conclusion on what I believe to be the case on bi-wiring vs single wiring in terms of sound (I'm an atheist). But what about the effect that biwiring has on impedance and the response of the amp?

Presumably if you separate the high and low frequency sides of the crossover, you get a higher impedance on each so that in parallel they achieve 8 ohms (say). Does an amp with A and B speaker outputs just parallel them up so you're back to square one regarding driven load, or is the amp circuitry more clever so you can attach a pair of 4 ohm speakers without that becoming a 2 ohm load?

Ive just ordered some biwiring speaker cable because the outside diameter of 4x2.5mm sq is less than 2x4mm sq so easier to hide under the carpet but it got me thinking about whether using the A and B outputs of the amp would make it a higher driven load and hence potentially less likely to clip at high volumes.

As I say, I've bought the 4 core without expectations of it being better, but it just for me thinking about whether to use one set of terminals at each end or two.

 

[Thompsonuxb]

Just try all options.

Not sure what options you think you have I'd say use both A & B outs if you have them.

Give each driver a channel.

You'll always have the option to try single wiring with the links in.

 

[Vladimir]

I don't think there is an amp with speaker option for connecting in series. And why would you want such a thing, it would sound terrible. The only thing an amplifier speaker switch does is to give you a convenience not to mess with the wires on the back each time you need to add or remove a second pair of speakers. It does nothing but parallel them like you would by joining positive to positive and negative to negative.

Some amps will have switch or a separate terminals for low impedance speakers. This results in less power output from the amp and cooler operation.

There is no cheating your way out of underbuilt PSU for the application. Not with bi-wiring or special cables or anything.

 

[splasher]

I didn't expect a series option, what I wondered, in fact, given that most amps with A+B speakers will run both together, was whether there was separate final stages for each, but presumably not from the response.

Like I said, I'm not bi-wiring for any other reason than 4 smaller wires gets me 2 x 5mm.sq in a smaller outside diameter cable than a 2 x 4mm.sq

 

[andyjm]

Yep, unless the amp specifically mentions separately controllable zones, you can assume that your amp's A/B functionality is simply a switch and a couple of extra speaker terminals.

Just make sure you leave the links in place on your speakers if you are going to biwire as you suggest.

 

[Vladimir]

I didn't expect a series option, what I wondered, in fact, given that most amps with A+B speakers will run both together, was whether there was separate final stages for each, but presumably not from the response.

If you had a true dual-mono design, each channel has a dedicated PSU. If the amp has 8 output transistors or more (2 pairs per channel), lets say you can make an amp that splits them with an A+B switch so in bi-wiring configuration you get quasi bi-amping. I say quasi because the PSU still remains shared between lines. If you had 4 PSU's that also integrate through switchable A+B selector, that is litteraly 2 stereo amplifiers in 1 box. No one makes this that I know of. But you can get the quasi bi-amping option with some multichannel receivers. The resources from other unused channels are there therefore why not use them in stereo configuration, so this might have some benefit for the AVRs.

Benefits from passive biamping are questionable even if the power doubles with two separate amps. So why would there be benefits in splitting the power in a single unit? Crosstalk is already solved with the dual-mono design to begin with. By asigning resources (PSU and output transistors) to the low energy tweeter same as the high energy consuming bass driver you are getting a worse allocation of resources than by joining them. AVRs have that issue of limited amount of output devices available per channel to deliver current without exiting their SOA.

But then again people liked 30W stereo amps with just one pair of output transistors per channel and shared PSU more than large Krells with everything x10.

If you want quasi bi-amping, you can get an AVR. If you want true bi-amping, you can get two monoaural power amps. I don't think you can get 2 stereo dual mono amps in 1 box version + optimized with more resources for the low frequency drivers vs the highs.

 

[SteveR750]

I didn't expect a series option, what I wondered, in fact, given that most amps with A+B speakers will run both together, was whether there was separate final stages for each, but presumably not from the response.

If you had a true dual-mono design, each channel has a dedicated PSU. If the amp has 8 output transistors or more (2 pairs per channel), lets say you can make an amp that splits them with an A+B switch so in bi-wiring configuration you get quasi bi-amping. I say quasi because the PSU still remains shared between lines. If you had 4 PSU's that also integrate through switchable A+B selector, that is litteraly 2 stereo amplifiers in 1 box. No one makes this that I know of. But you can get the quasi bi-amping option with some multichannel receivers. The resources from other unused channels are there therefore why not use them in stereo configuration, so this might have some benefit for the AVRs.

Benefits from passive biamping are questionable even if the power doubles with two separate amps. So why would there be benefits in splitting the power in a single unit? Crosstalk is already solved with the dual-mono design to begin with. By asigning resources (PSU and output transistors) to the low energy tweeter same as the high energy consuming bass driver you are getting a worse allocation of resources than by joining them. AVRs have that issue of limited amount of output devices available per channel to deliver current without exiting their SOA.

But then again people liked 30W stereo amps with just one pair of output transistors per channel and shared PSU more than large Krells with everything x10.

If you want quasi bi-amping, you can get an AVR. If you want true bi-amping, you can get two monoaural power amps. I don't think you can get 2 stereo dual mono amps in 1 box version + optimized with more resources for the low frequency drivers vs the highs.

Surely the hierarchy is stereo or quasi, bi-amping with separate power amps, fully active. Pointless using a power amp in for each drive unit in a passive system, whether in one box or separate (though cyrus might try to convince you otherwise

 

[Thompsonuxb]

Lol......way to over complicate.

A modern amp is designed to drive 2 sets of full range speakers if they have the terminals.

A tweeter represents a very small load to an amp and it's psu.

To the OP just experiment - you won't damage your amp.

 

[Vladimir]

Lol......way to over complicate.

A modern amp is designed to drive 2 sets of full range speakers if they have the terminals.

Way to oversimplify.

Will your modern Rotel drive 4 Apogee Scintillas? Or will it shut down / explode due to the small impedance equivalent of a short circuit?

A tweeter represents a very small load to an amp and it's psu.

However, it can represent also a very small impedance and phase shifts, which can result with clipping and damages to the amp and/or the speakers. Martin Logans have their impedance dip down to 2 ohms in the HF range.

 

[splasher]

So, having gone for 4 core cables for size reasons, I can muck about with biwiring with the link in and out but either way the impedance of the load presented to the amp will stay the same. My speakers are 8 ohm according to the spec sheet but hifi news reckon they should be specced as 4 ohm which means my amp clips before full volume. Not a big issue as its plenty loud enough at that point but I did wonders if separating the low an the high would mean an increase in load but clearly not as the load is just paralleled at the amp rather than the speakers.

A supplementary question, if I may: if my speakers are three way (tweeter, mid and two woofers) why not three sets of terminals? I can feel eyes rolling as I write......

 

[Vladimir]

Some speakers do have three sets of terminals but it's rare. Not many would invest in three stereo power amps or six monoblocks for a passive hookup considering the benefits are questionable.

 

[SteveR750]

So, having gone for 4 core cables for size reasons, I can muck about with biwiring with the link in and out but either way the impedance of the load presented to the amp will stay the same. My speakers are 8 ohm according to the spec sheet but hifi news reckon they should be specced as 4 ohm which means my amp clips before full volume. Not a big issue as its plenty loud enough at that point but I did wonders if separating the low an the high would mean an increase in load but clearly not as the load is just paralleled at the amp rather than the speakers.

A supplementary question, if I may: if my speakers are three way (tweeter, mid and two woofers) why not three sets of terminals? I can feel eyes rolling as I write......

So, you've got two speaker amp terminals (A+B) connected to your bi-amped speaker terminals? As Vlad has explained they are connected to the same output stage so it's not bi-amping.

Some speakers do have three sets of connectors, my ATCs do, but if you call and ask why, you'll get a mumbled reply about marketing bllx. Triamping would be an even more expensive waste of money, which would be much better spent on the active version of the same speakers, or any speakers. One set of wires is all you need for a passive system.

 

[splasher]

I've read people recommend when adding a power amp to an integrated amp to use both sets of outputs to biamp. If I bought at 851w which is 200w into 8 ohms to go with the 851a (120w into 8 ohms) and fastened the 851a to the highs and the 851w to the lows presumably that would present a higher load to the amps because I have taken the two circuits in the speakers out of parallel into two discrete circuits.

But sneaky supplementary question: would having mismatched power between the two inputs change the tone of the speakers (favouring the low frequencies in this example)?

Thanks for your patience.

 

[Andrewjvt]

I've read people recommend when adding a power amp to an integrated amp to use both sets of outputs to biamp. If I bought at 851w which is 200w into 8 ohms to go with the 851a (120w into 8 ohms) and fastened the 851a to the highs and the 851w to the lows presumably that would present a higher load to the amps because I have taken the two circuits in the speakers out of parallel into two discrete circuits.

But sneaky supplementary question: would having mismatched power between the two inputs change the tone of the speakers (favouring the low frequencies in this example)?

Thanks for your patience.

As long as the 2 amps are gain matched that will ideal.
You may or may not hear any difference though. Some do, some dont.
Careful you dont waste your money. See if you can demo first.

 

[andyjm]

I've read people recommend when adding a power amp to an integrated amp to use both sets of outputs to biamp. If I bought at 851w which is 200w into 8 ohms to go with the 851a (120w into 8 ohms) and fastened the 851a to the highs and the 851w to the lows presumably that would present a higher load to the amps because I have taken the two circuits in the speakers out of parallel into two discrete circuits.

But sneaky supplementary question: would having mismatched power between the two inputs change the tone of the speakers (favouring the low frequencies in this example)?

Thanks for your patience.

Always a good idea to stand back and decide what you are trying to achieve. Louder listening levels before clipping, more linear frequency response, better bass handling... and so on. It is generally a bad idea to bolt bits together in the hope that somehow the results will be a success.

If you really want to spend some money to make an audible difference, put the money toward a better pair of speakers.

 

[Vladimir]

The high frequency drivers use typically less than 10% of all the power delivered by the amp. Give them 120W and they will be spoiled brats. As Andrew mentioned, if you have both amps volumes leveled to 0.1dB there won't be audible coloration.

Interesting choice might be to intentionally color the sound to make it richer, smoother and more musical by using a 10W-40W valve amp for the HF and solid state 200W amp for the LF.

 

[splasher]

Thanks.

Trying to address each point:

What I'm trying to achieve is higher volumes before clipping for those moments when the house is empty and I want to listen to War Pigs using my chest as well as my ears.

I can't see a way to balance the outputs of the two amps in the example I've quoted because the 851a will be acting as preamp for both the internal and external power amps. I suppose the worst that can happen is that the combo does colour the sound unfavourably and I just use the 200w of the 851w - it would still give a healthy gain over the 120w of the internal power stage. Incidentally, I'm not rushing to do this just thinking about what might be next in my quest to cause structural damage to the house through music.

In terms of better speakers, of course there are better speakers out there but while I think the low impedance of the Gold 300s is letting the current run away before the amp reaches max output voltage, I don't think they are a weakness in terms of sound quality or dBs to be honest.

 

[Vladimir]

With 2 x 6.5" bass drivers in 70L cabinets they wont be destroying any houses, regardless of amplification or bi-wiring. Maximum loudness measured by manufacturer is 116.8dB, at unspecified levels of THD, most likely 10% or more.

Also they very likely dont need more than 120Wpc in 8ohms since they are 90dB efficient and have 200Wpc max power handling specified. If you want to upgrade amplification, just get a 200Wpc amp and use your integrated as a preamp only.

 

[splasher]

If you want to upgrade amplification, just get a 200Wpc amp and use your integrated as a preamp only.

That was my original thinking, but having bought 4 core speaker cable and read elsewhere someone recommend attaching the integrated amp to the highs and the power amp to the lows, what can I say, I'm constantly curious.

The structural damage was a joke, by the way. I have Marshall products for when I want to do that.

 

[Thompsonuxb]

Lol......way to over complicate.

A modern amp is designed to drive 2 sets of full range speakers if they have the terminals.

Way to oversimplify.

Will your modern Rotel drive 4 Apogee Scintillas? Or will it shut down / explode due to the small impedance equivalent of a short circuit?

A tweeter represents a very small load to an amp and it's psu.

However, it can represent also a very small impedance and phase shifts, which can result with clipping and damages to the amp and/or the speakers. Martin Logans have their impedance dip down to 2 ohms in the HF range.

 

Now you're just arguing for arguments sake Vlad.

The Rotel is a 60wpc amp why would anyone put 4 apajy sintijahs or whatever on it or any non comparible exotic load you're pulling out your pants?

I know it'll drive a pair of 200w @6ohm speakers comfortable enough using all terminals in a bi-wire configuration.

Clipping, impedance shifts 2ohm blah blah blah.....prrrrft!

Honestly sometimes you guys take this wiki stuff too far.

 

[Thompsonuxb]

I'll say this to Splasher
Bi-wiring or bi-amping will not increase the Volume you get from a speaker - better separation a less congested sound is what it's trying to achieve.

Less distortion will actually remove the perception of loudness which is something you'll need to be aware of.

So in this context be aware.

If an amp has 2sets of speaker outs each terminal should output the same wattage - so if you have a 60wpc amp that's what you'll get that's how there designed an amp with only two terminals will behaive differently if a pair of wires are placed on the speaker terminals though.

But just experiment.

On a 3way design couple the mids and tops with the links. Or the mids and bass, see how you get on.

Played at reasonable volumes bi- wiring will not cause your amp to blow up.

But the whole point of bi-ing is improved resolution not volume.

For more 'power' get a more powerful amp.

 

[andyjm]

Hifi is a technical discipline. To understand it properly, you need to have an understanding of the underlying equipment and theory. Given this, would you trust advice from a man who said:

However, it can represent also a very small impedance and phase shifts, which can result with clipping and damages to the amp and/or the speakers. Martin Logans have their impedance dip down to 2 ohms in the HF range.

...or would you take advice from -

Clipping, impedance shifts 2ohm blah blah blah.....prrrrft!

I know where I would go.

 

[SteveR750]

Hifi is a technical discipline. To understand it properly, you need to have an understanding of the underlying equipment and theory. Given this, would you trust advice from a man who said:

However, it can represent also a very small impedance and phase shifts, which can result with clipping and damages to the amp and/or the speakers. Martin Logans have their impedance dip down to 2 ohms in the HF range.

...or would you take advice from -

Clipping, impedance shifts 2ohm blah blah blah.....prrrrft!

I know where I would go.

I think a tin of alphabet spaghetti randomly spread across a plate might be a more useful second alternative to above....

 

[Thompsonuxb]

And that's were you guys make your mistake.

I know all the science the technical wizardry is completed on the bench.

All the specs and measurement are left in the lab.

As an end user of a product alot of the gunf you guys waffle on about is pointless.

A user only need know the quality of his/her kit based on the sheets and pair it with price/spec comparible components and enjoy.

If you have the resources experiment with cables and the like.....its fun.

They do not need PhD's.......

 

[splasher]

Firstly, I plan to enjoy my current setup for a while but when I'm asked what's I want for Xmas, a power amp may be the answer.

Santa having delivered, I can try biamping with the integrated on highs and the power amp on lows. If it makes an unpleasant sound, I can simply biwire (to take advantage of the higher x-section of the wire) using the power amp only.

Either one will allow more current to the speakers before clipping and hence higher SPLs before amplifier distortion but obviously the SPLs will never exceed the inherent capability of the speakers.

Finally, I must say, being an engineer, I like technical answers. Anyway, thanks to all.

Must go, Cliff's just come on the radio so I have to intervene.