[geof]

Greetings everyone. I am looking to build a power amplifier to drive my B&W Nautilus 802s. One possibility I am considering is using two AKSA 100's to biamp. Any thoughts/predictions on how well these would work together? The previous posts here seem to suggest "yes" but I am curious if there is actual experience.

These particular speakers are known to be difficult to drive. Often they are driven with the likes of Krell, Mark Levinson, and Classe. The impedance is rather complex and can dip down to 3 ohms or so. The 802s will take up to 500 watts, but I think 100-200 watts is sufficient for the volumes I use.

On another forum I did hear from an individual who tried to drive B&W Signature 805s with a single AKSA-55. He claimed that the mid and hi range sound was quite nice but the bass was lean. (The 805 is a two-way stand-mount speaker, as opposed to the 802 which is a floor-standing three-way.) However the AKSA-55 has a higher output impedance, and in my case the bass module would be driven by it's own channel. This person thought that the '100s would be sufficient, especially if biamped.

By the way, if I do go this route and biamp, would it be better to set it up so that one amp drives each speaker, or so that one amp drives the bass for both speakers and the other amp drives the mid/hi? Silly question, but I don't know what would be best for this particular amp.

Thanks in advance!

Geof

[AKSA]

Hi Geof,

Thank you for your post.  You raise interesting questions!

I see no reason why the 100W AKSA could not drive these speakers.  We rarely see them in Australia, they are VERY expensive, and if we see them we Aussies tend to point and giggle in wonderment....

I see your #1 bushranger is right here in Australia at present!

The AKSA 100W will go down to 2.5R with ease, so 3R is a snap.

would it be better to set it up so that one amp drives each speaker, or so that one amp drives the bass for both speakers and the other amp drives the mid/hi? Silly question, but I don't know what would be best for this particular amp.

My own somewhat controversial opinion is that since so much R&D went into the crossover design of these premium speakers we should preserve its integrity and run each speaker with its own amplifier.  The amp will pull it fine, and since the crossover is pivotal to sound staging, driver integration and impulse response it seems a crime to bypass it, even to the extent of simply driving one driver with its own amp.  The problem is this:  you have precise impedance correction networks in well designed crossovers which control the limits of impedance, particularly at the high end, and this means phase shift is also controlled.  Bypass this and it can create issues for the amplifier, and will in most cases degrade the sonics.  Biwiring is another matter;  this is not my beef.

Given the cost comparison between Krells, Levinsons, Classe, and the AKSA, you could certainly build the AKSA, try it out, and if you are not completely happy, drive a lesser speaker in the house, which doubtless you would own because this audiophile virus is progressive, and ownership of a Nautilus would indicate the disease progression is now quite severe......

Certainly a 100W should be more than enough for a private listening situation.

Cheers,

Hugh

[mb]

On another forum I did hear from an individual who tried to drive B&W Signature 805s with a single AKSA-55. He claimed that the mid and hi range sound was quite nice but the bass was lean.

Just to be very precise, the AKSA was driving a pair of absolute top of the line Signature 800s. In this test, the AKSA did not have the absolute control on the the bass that I would have liked (not so much lean, but perhaps not enough drive). Not surprising, as the S800 are particularly difficult. You will do very well with the AKSA 100s! My AKSAs have also driven a pair of Krell LAT-1s... did very well indeed.

[andyr]

Hi Geof,

Just to throw in my 2c worth (as a very satisfied 4xAKSA owner) just so you know Hugh isn't just giving you a 'sell', my 100w AKSA copes very well with my Maggie IIIa base panels which are 3 ohms.

Because of the design of the AKSA - particularly if you build a stereo amp as a pair of monoblocks, with completely separate power supplies (and power cords) - it makes no difference whether you horizontally bi-amp or vertically bi-amp.  If you have one AKSA on both base drivers, the left channel does not 'sag' when the right channel gets a large bass transient and vv, as the power supplies are separate.

The old 'saw' about having one amp for each speaker, so the one amp doesn't have to cope with bass transients in both channels is only relevant when the two amp channels share either the complete power supply or the power transformer.

Regards,

Andy

[Seano]

I was going to be seriously flippant but Hugh got in ahead of me.

Damn and bugger. Today was the day I really wanted to be stupid.

Good god, man! 802's?

If they sound crap with the AKSA 100N then it'll be the fault of the 802's I'm sure. So if you are unsatisfied I promise I will take the 802's off your hands. You can have my Krix Lyrix (which are proven performers with the AKSA 100N) and I'll take the 802's (nasty nasty things).  Heck I'll even pay for the freight.

What a deal!!!

Sorry. Couldn't help myself.

[geof]

Greetings everyone,

Thanks for your replies. I got the information I needed. They will probably do fine.

From  AKSA:

I see no reason why the 100W AKSA could not drive these speakers. We rarely see them in Australia, they are VERY expensive, and if we see them we Aussies tend to point and giggle in wonderment....

Speaking of giggling in wonderment, what is it with you Aussies and amplifiers? Halcro makes me giggle in wonderment. Not cheap! But if someone offered me one as a gift I would be very grateful! (me getting the N802's was an act of madness, though.   You should have seen my fiance's face!)

A little off-topic, but this makes me think of a colleague I visited in Canberra once. He was one that liked to go camping a lot. He said that "roughing it" was when they decided not to bring water. I don't know if he's joking or not, but I wonder if that spirit explains Aussie Amps...

I see your #1 bushranger is right here in Australia at present!

It took me a whole day to figure out what that word meant.   I am a fifteen minute walk from the White House, BTW.

From MB:

Just to be very precise, the AKSA was driving a pair of absolute top of the line Signature 800s.

In another forum MB told me that he tested AKSA-55 on B&W Signature 800's with less than optimal results, and I thought he meant he drove the Signature 805's. The 805's are a two-way standmount, while the 800's are giant @250lb floor-standing behemoths that are probably B&W's most difficult speaker to drive, with impedances that drop well below 3 ohms. Big difference. It would be interesting to hear the AKSA-100 drive the 800's.

Regarding the bi-amp question- Thanks for everyone's input. I would probably use one stereo amp for each speaker, then, with one channel driving bass and the other mid/treble. If I get ambitious I would make each a dual-mono w/ own power supply or even put each of the four channels in it's own box... I agree it is best to let the speaker handle crossover.

OK... As soon as I take care of a few personal and business things, I will reward myself with a call to Hugh...

Cheers,

Geof