Bi-amping with ST-70 and Mark III

Good Day! (and a VERY prosperous New Year to all)

I did a search on the forum to see if this topic has come up before, but I can't find anything related. I want to try bi-amping my Mark IIIs and ST-70 in a horizontal configuration. I'm not sure if I will hear any improvement by doing this but I am curious - not to mention that proponents of Bi-amping swear by it and claim that it does make a lot of difference.... Comments/opinions seem to go from "improved clarity" to "ensuring World Peace" (in other words, the usual outrageous claims one see in the audiophile world).

So, in short, the configuration I am planning to use is as follows:

* Preamplifier has dual outputs
* First preamp output set driving my Mark IIIs (which are connected directly to my Mission MX3 woofer terminals)
* Second output set driving my ST-70 ( corresponding channels connected to the HF terminals on my MX3s).

Do you gentlemen see any problem doing this at all? Is there a better way of doing it? The so-called "Vertical" configuration does not make sense to me considering the monoblock / stereo nature of combining monoblock Mark IIIs and a single ST-70.

Thank you for your opinions!
-- Jan in BC

How is the dividing filter arranged ? Is it built into the preamp ?

peterh wrote:How is the dividing filter arranged ? Is it built into the preamp ?

Hi PeterH

I have a large Professional music equipment store down the road from me, and they do carry several active crossover systems, more than one model on the shelf has a Linkwitz-Riley type filter incorporated (which I have been told is one of the best around for "real" bi-amping, as opposed to "passive" bi-amping). This will go between the pre-amp and the power amplifiers.... And depending on the model of activer crossover I end up buying, I may or may not actually use that second output on the pre-amp.

(Edit)
I was going to add, active crossovers seems to run in price range out here where I live (Western Canada) from really CHEAP ($60 or so) to VERY expensive. I am considering a middle-of-the-road active crossover such as the BBE Max-X3 or Rane AC 22S.... I'm sure there are audiophile-specific active crossovers but before I start laying down large amounts of cash for one, I want to experiment first.

-- Jan

Hi Jan,

Good to see you on the forum again! Happy New Year to you!

An advantage in multi-amping comes from division of labour, as I understand it, with each amp sounding better when not having to cope with unnecessary frequencies (because the other amp(s) are handling those frequencies.

One disadvantage is that the cross-over frequency that is chosen is often smack dab in the range where our hearing is most sensitive, so artifacts are audible.

A second disadvantage, piggybacking on the first, is that if the cross-over network isn't exceptionally good, it can make a mess of things.

I've been doing something similar, but with powered subwoofers. I haven't got it dialed in yet perfectly, but in the initial configuration, I used the built in high pass filter in these apparently good quality sub woofers (Rythmiks), and I can tell you it destroyed the stereo image and vastly muted the detail in the music going to the main speakers. You need a good cross-over solution.

I think with a good cross over with selectable roll-off slopes, you'll be able to dial in your speakers, and it could sound magnificent.

Let us know how it goes. I'll plan to invite myself over for a listen, next time I'm in Vancouver.

;-)

Here's an article on bi-amping that might inspire you:

http://sound.westhost.com/bi-amp.htm

Good day sir!

I was seriously worrying that you disappeared forever - thinking if perhaps some Cumulus Granitus somewhere in the Rockies "owned" you! (well it really is my fault - I sort of dropped out of the forum, work pressure and all that).

Thank you VERY much for the information. I have started wondering if bi-amping is worth the trouble myself now - the active crossovers I have been looking at were all highly selectable as far as crossover frequencies etc but when you look at the average Linkwitz-Riley filter circuit, it abounds with ICs and other "esoteric" components... IOW, I will be adding a whole pile of extra componentry into the signal path.

BTW you're very welcome to invite yourself over, I'll make sure to cool the beer down (I drink it at room temperature, the "proper English way"!) :-)

Sincerely
-- Jan N.

Hi Jan,

Not to worry, on my account! One must work to fund this hobby, even on the diy side of the fence!

I think you are looking at just one component now, the cross over. I dont remember your speakers, but as i envision what youre doing, the woofer would be handled by the st70, or probably better, the mk iii pair. Then the middrange tweeters by the other amp.

Mid range / tweeter crossover may be left to the speakers passive x over, but mid to woofer x over handled by the active x over.

A good quality x over between pre amd power amps will hopefully not damage your sound, whilst giving you the blissful advantages of bi amping.

At the moment, my subwoofers are "augmenting" the main speakers, so they are still trying to cope with the full range. I'll be constructing a passive high pass filter to place between pre amp and st 70, so it doesnt see anything below, say, 100hz. My expectation is that the st 70 will sound noticably better to be relieved of low frequency grunt work!

I'll report back soon.

I never see mention of baffle step compensation circuits with electronic crossovers. Is that issue just ignored with bi or tri-amped speakers?

I assumed that good crossovers had gain controls for this. Maybe not. My subs have volume control, and i've been using frequency generator to try and get the volumes "right".

I thought the crossovers were built into the speakers?

When bi amping, you want to disable the speakers internal cross over for the drivers that get their own amp. Then you replace it with a cross over between the pre amp and th power amps.

This way, each power amp is set to only amplify the frequency range appropriate for the speaker driver it's driving.

I recommend the article i linked to, above, for a good discussion of bi amping.