800D: bi-amp or monos?

[worldys]

I ordered a pair of 800D and they will be delivered some time in January. My current amplifier is a Classe 301 so I imagine I should upgade. My pre-amp (BAT 51-SE) has two pairs of balanced outs, so it would be very easy for me to bi-amp. Cost for two good stereos and two good monos seems to be about the same (thinking of the Classe Delta amps). B&W puts effort into seperating the highs/mids from the lows so shouldn't we be taking advantage of that? What do you guys think would be best?

[Kal Rubinson]

Either way.

Kal

[Glenee]

Going with Kal on this one Either way. I prefer Mono's less stuff to think about in setting up.
Glenee

[Race Car Driver]

Everyone knows if you have monos your system sounds better...

right....


right..

right!

[sikoniko]

mono's. CA-M400's!

[RebelMan]

Not going with Kal. Given the same choices I think he would take the monos.

Passively bi-amping buy's you nothing. In this case, get the mono's and bi-wire if you want to "bi" something.

[Kal Rubinson]

Not going with Kal. Given the same choices I think he would take the monos.

Passively bi-amping buy's you nothing. In this case, get the mono's and bi-wire if you want to "bi" something.

I would. OTOH, if one has the stereos, use them.

Kal

[WI Rotel]

It doesnt matter, for amps in this class stereo simply means that 2 mono amps reside within one box rather than 2. The only theoretical advantage is that with mono's you can keep your speaker connections very short. However, I do like biamping thus 2 stereo amps are a lot less hassle than 4 separate boxes!

[worldys]

Thanks for the input guys. I appreciate the opinions but could some one help me sketch out the logic.

Based on reading and discussions, my understanding is that the advantage of the higher power monos is that you have lots of headroom for a fast attack. With stereo amps bi-amped, it seems you have no sharing of watts going to individual drivers but the total watts is usually less so even though the bass drivers get the watts all to themselves, they don't have the headroom to push air very quickly on demand. So within the same amp class, 400w monos should be better than 200w stereo bi-amps, but four 400w monos woud be best (not that it is going to happen).

And merry christmas, happy hannukah, happy eid, etc. Best wishes to all for the new year arty:

[WI Rotel]

High end stereo amps such as classe are truly 2 mono amps in one box since they have separate power supplies, thus its like having 2 mono amps. To biamp your 802's you can use stereo amps very easily. Connect the left channel of the first amp to the woofer binding posts of your left speaker, connect the left channel of the second amp to the midrange-tweeter binding posts of the left speaker, then do the same thing for the right channel. Connect the amps to Amp1 and Amp2 on the pre and your done! Bi amping, contrary to biwiring, is not vodoo science, the results are clearly apparent. Its not only a matter of power (though that is a big part of it) The woofer is by far the most resistive force of the speaker, thus its the one that sends the highest signal "back" to the amp. All that current handling is best handled by its own amp to reduce the coloring of the other drivers. In a theoretically perfect speaker every driver on the speaker has its own particular enclosure and power supply thus isolating all the transducers from each other acoustically and electrically. Of course, that would be quite ridiculous in practice! Biamping simply makes the woofers in your speakers the equivalent of powered "subs".
Contrary to other BW's the XT's cannot be biamped, the downside in that particular instance is that to drive them well an amp with very high current capacity is required. BW advertises them as rated for amps in the 100-150 watt range, the truth is that very few amps with that power rating have enough current to drive them satisfactorily at anything more than moderate levels. Merry Christmas!

[Karma]

It doesnt matter, for amps in this class stereo simply means that 2 mono amps reside within one box rather than 2. The only theoretical advantage is that with mono's you can keep your speaker connections very short. However, I do like biamping thus 2 stereo amps are a lot less hassle than 4 separate boxes!

HI,
To the OP: I'm with Kal. Either way will work fine.

To RI Rotel: Only true sometimes. If it is true then a stereo amp will indeed perform just like two monos. Some amps take the idea to the extreme and even have separate power cords and switches for each channel. I would call this type of amp "Dual Mono".

True stereo amps share their power supply between the two channels on the same chassis. My tubed Audio Research D-250, used in my stereo only system, is this type. Consequently the power supply must be huge. It must be able to supply enough power to both channels for both channels to meet their rated power output when both are driven to their full output simultaneously. At the very high end, like my D-250, the amp will actually do this with room to spare. Many stereo amps can't pull this off. Power must be derated with both channels driven. This is really just a measure of power supply capacity.

For really high power amps it is more physically practical to separate the two amps into mono blocks on their own chassis. My D-250 is huge and almost impossible for one person to handle. The D-250 (250 W/channel) was the last Audio Research high power amp to be produced in a stereo package. It is just too cumbersome.

Some claim that crosstalk (separation) is less in a true mono block design. Theoretically this is true since each amp has its own power supply. In actual practice crosstalk is mostly a function of the power supply design. Shielding to prevent signal bleed to the opposite channel is also a factor but can be negated with proper mechanical design. In my experience with my D-250 crosstalk is essentially non-existent. But this power supply is truly impressive. For most, less well specified amps, crosstalk may indeed be more of an issue. As to the practical results of the reduced crosstalk one may argue all night. With really good amps I believe the issue is essentially only theoretical.

True mono block designs have changed the way many stereo systems are set up. Most folks position their mono amp very close to the speaker it drives. This can result in short speaker leads and often very long interconnects. Long interconnects can pick up 60 Hz hum. To solve this problem preamps and power amps have adopted balanced cable capability to accommodate the long cable runs.

The newest preamps now have remote controls so they can be placed close to the power amps and still convenient to operate from the listening position. In this case one can use normal interconnects to the power amps since the cable runs are short. This is a much better solution than balanced signals which can have a whole collection of their own problems. In the interest of objectivity, I must note that not everyone agrees with my opinion about balanced signal technology and circuit design. Check it out for yourself.

My system uses short single ended interconnects and long speaker cables. It is a compromise. Short cables, both interconnects and speaker cables, are always the best solution (and cheaper too).

Sparky

[Race Car Driver]

I am bi amping my HTM1, just because I have a two channel amp figured I would use the extra channel, never bothered wiring it the other way. (yes the crossovers are still in the speakers so some say its not doing me any good, I say its not any worse off.)

My N802s are run of monos.

Just my input.

[WI Rotel]

HI,
To the OP: I'm with Kal. Either way will work fine.

To RI Rotel: Only true sometimes. If it is true then a stereo amp will indeed perform just like two monos. Some amps take the idea to the extreme and even have separate power cords and switches for each channel. I would call this type of amp "Dual Mono".

True stereo amps share their power supply between the two channels on the same chassis. My tubed Audio Research D-250, used in my stereo only system, is this type. Consequently the power supply must be huge. It must be able to supply enough power to both channels for both channels to meet their rated power output when both are driven to their full output simultaneously. At the very high end, like my D-250, the amp will actually do this with room to spare. Many stereo amps can't pull this off. Power must be derated with both channels driven. This is really just a measure of power supply capacity.

For really high power amps it is more physically practical to separate the two amps into mono blocks on their own chassis. My D-250 is huge and almost impossible for one person to handle. The D-250 (250 W/channel) was the last Audio Research high power amp to be produced in a stereo package. It is just too cumbersome.

Some claim that crosstalk (separation) is less in a true mono block design. Theoretically this is true since each amp has its own power supply. In actual practice crosstalk is mostly a function of the power supply design. Shielding to prevent signal bleed to the opposite channel is also a factor but can be negated with proper mechanical design. In my experience with my D-250 crosstalk is essentially non-existent. But this power supply is truly impressive. For most, less well specified amps, crosstalk may indeed be more of an issue. As to the practical results of the reduced crosstalk one may argue all night. With really good amps I believe the issue is essentially only theoretical.

True mono block designs have changed the way many stereo systems are set up. Most folks position their mono amp very close to the speaker it drives. This can result in short speaker leads and often very long interconnects. Long interconnects can pick up 60 Hz hum. To solve this problem preamps and power amps have adopted balanced cable capability to accommodate the long cable runs.

The newest preamps now have remote controls so they can be placed close to the power amps and still convenient to operate from the listening position. In this case one can use normal interconnects to the power amps since the cable runs are short. This is a much better solution than balanced signals which can have a whole collection of their own problems. In the interest of objectivity, I must note that not everyone agrees with my opinion about balanced signal technology and circuit design. Check it out for yourself.

My system uses short single ended interconnects and long speaker cables. It is a compromise. Short cables, both interconnects and speaker cables, are always the best solution (and cheaper too).

Sparky

All true sparky, I didn't want to go into such detail! :E
In all truth few speaker (the 802's included) are revealing enough to do justice to all this electronic finagling

[lvhung]

some speakers company dont have biwiring

[eljr]

Mono blocks for total seperation at this level is what I prefer.

[Karma]

Mono blocks for total seperation at this level is what I prefer.

HI,
OK, but Why??????? Fill us in. We are here to learn.

Sparky

[Tim92gts]

To biamp your 802's you can use stereo amps very easily. Connect the left channel of the first amp to the woofer binding posts of your left speaker, connect the left channel of the second amp to the midrange-tweeter binding posts of the left speaker, then do the same thing for the right channel. Connect the amps to Amp1 and Amp2 on the pre and your done

Hi, i've always done it the other way round.
Use one amp per channel with the channels feeding bass and treble.
That way one power supply isn't trying to feed two bass speakers sets and the amps can be on the way between the speakers and pre to minimise cable lengths.
Am i missing something?
Cheers
Tim

[Glenee]

To biamp your 802's you can use stereo amps very easily. Connect the left channel of the first amp to the woofer binding posts of your left speaker, connect the left channel of the second amp to the midrange-tweeter binding posts of the left speaker, then do the same thing for the right channel. Connect the amps to Amp1 and Amp2 on the pre and your done

Hi, i've always done it the other way round.
Use one amp per channel with the channels feeding bass and treble.
That way one power supply isn't trying to feed two bass speakers sets and the amps can be on the way between the speakers and pre to minimise cable lengths.
Am i missing something?
Cheers
Tim

That's the way I would do it also if they were the exact same amps.If I was to do it.

[WI Rotel]

To biamp your 802's you can use stereo amps very easily. Connect the left channel of the first amp to the woofer binding posts of your left speaker, connect the left channel of the second amp to the midrange-tweeter binding posts of the left speaker, then do the same thing for the right channel. Connect the amps to Amp1 and Amp2 on the pre and your done

Hi, i've always done it the other way round.
Use one amp per channel with the channels feeding bass and treble.
That way one power supply isn't trying to feed two bass speakers sets and the amps can be on the way between the speakers and pre to minimise cable lengths.
Am i missing something?
Cheers
Tim

Both ways are fine. The way I do it simply helps me keep things straight since you "conserve" the labelled LT and RT criteria. Furthermore, you end up using one amp per frequency rather than per speaker. Again, it doesn't matter if you are using a "stereo" amp that has 2 independent amps ergo, its like using 4 amps

[worldys]

I want to make sure I understand this, so would someone please affirm or dispute this summary:

The advantage of the higher power monos is that you have lots of headroom for a fast attack. With stereo amps bi-amped, it seems you have no sharing of watts going to individual drivers but the total watts is usually less so even though the bass drivers get the watts all to themselves, they don't have the headroom to push air very quickly on demand. So within the same amp class, 400w monos should be better than 200w stereo bi-amps, but four 400w monos woud be even better.

[Karma]

To biamp your 802's you can use stereo amps very easily. Connect the left channel of the first amp to the woofer binding posts of your left speaker, connect the left channel of the second amp to the midrange-tweeter binding posts of the left speaker, then do the same thing for the right channel. Connect the amps to Amp1 and Amp2 on the pre and your done

Hi, i've always done it the other way round.
Use one amp per channel with the channels feeding bass and treble.
That way one power supply isn't trying to feed two bass speakers sets and the amps can be on the way between the speakers and pre to minimise cable lengths.
Am i missing something?
Cheers
Tim

HI Tim,
You need to be careful here. What you suggested in the first paragraph is valid only if the two stereo amps are the same model and brand. I assume that is what you meant but you did not say it. Your second paragraph is the way to go.

The issue is gain matching. If a single stereo amp is used for one speaker there is good assurance of the gain being the same between the channels. The other speaker ideally would use an identical stereo amp but it is not absolutely necessary. Gain differences can, in this case, be compensated by the preamp balance control. Of course, if the amps have individual channel level controls, the point is moot.

The biamp methods being discussed in this thread is called passive biamping. In my view it is a waste of time and money. Biamping comes into its own when active crossovers are used in front of the power amps. In this case the speakers internal crossovers are bypassed or eliminated. This technique is by far the best but is truly a bitch to properly set up. If not done this way I would not biamp at all.

Sparky

[Tim92gts]

Hi Sparky,
i did post a message mentioning gain matching but it's gone somewhere!
Gales here at the mo so my lines are swinging about a bit.
I'm on a pair of identical stereo amps but when there is time will try them in bridged mode to give one 300W amp per channel into each 200W speaker.
I was talked into using very different cabling on the bass and treble channels so initial set up next will be triwired.
The second amp gave me punchier base but also sharper treble response; sometimes almost too bright.
I'm trying to audition a pair of 801Ds running off a pair of Bryston 7Bs next so don't want to get that decision wrong
Cheers
Tim

[RebelMan]

The biamp methods being discussed in this thread is called passive biamping. In my view it is a waste of time and money. Biamping comes into its own when active crossovers are used in front of the power amps. In this case the speakers internal crossovers are bypassed or eliminated. This technique is by far the best but is truly a bitch to properly set up. If not done this way I would not biamp at all.

Precisely!

[Tim92gts]

Hi All,
further to my previous post i've now gone from biamping to one bridged amp triwired per side.
This has definitely sorted an occasional problem with overbright treble and kept the bass nice and tight so very positive so far.
More listening tests on the way but initial reaction is thanks to all for motivating me to do this substantial upgrade.
And it was free!!
Cheers
Tim