Active Bi-Amping/Tri-Amping FAQ

[The Dude]

Another difficulty is the enormous complexity of selecting just the right cross-over points when active tri-amping.

There are endless permutations available and I am not aware of low-cost tools to automate this arduous task.

For my tri-amped Belle center, I use approximately the same crossover points as the original passive networks, but with added crossover filter between the midrange driver and tweeter that is actually missing in the stock Belle crossover. It just takes seconds to change the settings to move the crossover points, relative driver gains, and parametric EQ filters, and most importantly, the relative delay of the drivers in order to time align them. This is a really big deal that you get only with digital active crossovers - delay correction due to differing horn path lengths.

Once I got my Belle dialed in, and not the least including the proper time delay setting between midrange and tweeter, the Belle blended in seamlessly between the two big Jub K-402/TAD TD-4002s.

Chris

Chris good to see you back, its been a while.

This is good info, something I have been working with for the last couple of months. Have you used any auto equing programs such as REW to do this or are they not that intelligent.

[Deang]

The road to hellish sound is paved with good intentions. :-)

[Chris A]

Still selling?

[Deang]

Nice cheap shot. So, how does my little dig constitute "selling"? I have a better question -- how does three pages of recommendations for various vendors constitute not selling? So, if I pimp for Ashley, EV, DBX, etc., I'm not selling and it's all good. I love this place.

At any rate, just because I build and sell passives doesn't mean I can't appreciate the solid advantages of going active. My objections lie primarily in the area of cost and complexity. To surpass the sound of a good passive and a great preamp/amp, you are going to have to make a serious commitment on the financial side. Anyone who tries to do this on the cheap is going to be very disappointed. Then there is the learning curve. Most end users stand a better chance of mucking it up then they do getting it right, and this I believe was PWK's primary objection as well.

And for you guys that are using drivers that cost as much as my car, what are you using to protect them? I don't know of any responsible active set up that doesn't recommend the use of a capacitor for protection.

There are a couple of very good Dope from Hope articles on this topic, and after reading through Elliott's pages and this thread, I just don't see where much has really changed.

Just because I run a crossover business doesn't mean I'm not allowed to have an opinion or demonstrate that I have a bias. In that way I'm just like everyone else around here. If there is a problem, I'm sure Amy will let me know.

[NOSValves]

[Marvel]

I reached a point where I don't mess with my main system. I just sit and listen to music and don't obsess over whether or not I could make it better. I'm sure it could be, but at what cost? Going active could get me there, but it also gives me way more possible failure points. The change may not really be for the better, either, even though we often fool ourselves into thinking that sounding different is better.

I'm not against the measuring and using analysis to make better decisions, but the cost starts going up pretty quickly when you go active.

[Chris A]

I reached a point where I don't mess with my main system. I just sit and listen to music and don't obsess over whether or not I could make it better. I'm sure it could be, but at what cost? Going active could get me there, but it also gives me way more possible failure points. The change may not really be for the better, either, even though we often fool ourselves into thinking that sounding different is better.

I'm not against the measuring and using analysis to make better decisions, but the cost starts going up pretty quickly when you go active.

Bruce,

I'm of the opinion that it's really personal dissatisfaction that drives us to do "better things".

In my case, I had a couple of issues--mostly with room acoustics then in how string orchestras and pipe organs should sound at home, with some HT needs thrown in for good measure. These areas of dissatisfaction drove me to continue my system development until what I was hearing met my needs. This is also that reason I don't do other things, such as "joining the crowd", i.e., audiophiles and Klipschophiles here, since these needs have been very low for me. (My family and job(s) provides for those areas.) My self-assigned role in this forum and elsewhere has always been as "maven" from the definition coined by Malcolm Gladwell.

Clearly I understand your point of view, as I also have settled on the current setup and now I'm into primarily building a music library (perhaps a thread on that subject later...I'd like to hear your and others' thoughts on that subject.)

In the past I've questioned the purchases of others on things like high-priced electronics and turntables, since I feel that these diversions actually dilute the path toward better sound, especially in the area of loudspeakers, since it seems that most audiophiles really don't "get it" IMHO: when it comes to getting the right speakers first, I'm still amazed at the vast majority of buyers that don't invest in horn-loaded speakers since these sound much more realistic and dynamic (if set up well) than anything else that I've heard.

I still remember a trip to Sheffield Audio in Houston in 1979 to this day when I heard two Khorns and a Belle set up properly in a three-speaker array along a long-walled listening room. No tubes here--only really good SS amps (Marantz?) driving in an A-B comparison with level-loudness AR-9s and other speakers of that day. My ears told me the clear winners, but my brain talked me out of it.

My long audio journey continued from there until about 2 years ago, when I realized that I've achieved all the things that I set out to do. Now it's time to use it to listen to new music and movies: I believe that I'm basically "there".

Chris

[Cut-Throat]

I started a Bi-Amping Project about a month ago. After trying out a Marchand XM66, I settled on a pair of Hypex PSC2.400 Amplifers with imbedded active crossover that you can modify on the fly, with a PC. Using a type 'A' on the Altec Horns and tweeter, and running the Hypex Amps on the Bass Bin.

I think you need a PHD in Physics to understand the software for designing filters, but I got it working (I don't understand it yet) with my system and I have got to say it was the biggest improvement I have made to my system since I added the Altec midrange Horns 10 years ago. This is not a tweak, but the difference between a Heresey and a Khorn. I have unlimited headroom with 800 watts per channel Class D on the Bass Bins, with the smooth sound of SET amps 45 or 2a3 Moondogs on the Mids/Highs. It has completely transformed my system.

The great news is that the Hypex Amps were less than $800 for the pair at Madisonsound. This includes the Amps and Active Crossovers built into them. This project is for the DIY only! You have to make Boxes for them as they are plate amps and you can't just lay them on their side, Make Neutrik power Cables and XLR cables before you can even start. Then download software and be very comfortable with PCs and such. The Manuals are completely terrible and useless. Also, Madisonsound that sells the amps admit they know nothing about how to adjust the crossover settings. They are set up for 220 volts (they come from Holland) and they don't mention changing to 120 volts....Did I say the manual was useless?

Here is a picture of one in the Solid Oak Cabinet I made for it. They do sound Fricken Awesome though. 800 watts and SET amp silkiness.

Edited November 12, 2013 by Cut-Throat

[Chris A]

DP (see below)

Edited November 12, 2013 by Cask05

[Chris A]

I think you need a PHD in Physics to understand the software for designing filters, but I got it working...This is not a tweak, but the difference between a Heresy and a Khorn. I have unlimited headroom with 800 watts per channel Class D, with the smooth sound of SET amps 45 or 2a3 Moondogs on the Mids/Highs. It has completely transformed my system.

Very cool...

If you are perhaps having to program FIR filters, then a PhD in signal processing would definitely be useful--heavy stuff, but the payoff is potentially big.

Chris

Edited November 12, 2013 by Cask05

[Greg Oshiro]

I think you need a PHD in Physics to understand the software for designing filters

I remember being *taught* almost everything one needs to know to design crossover filters in my last 2 years of college (Electrical Engineering). I got out of school in 1977 and still haven't *learned* it all. With the modern measurement tools now available, most of the math isn't neccessary. All that's required is the qualitative knowledge of what the desired transfer function magnitude and phase should be and what various filter types do so we can select the right filter and adjust its parameters to get the desired result.

Reading anything by Sigfried Linkwitz also helps...

[djk]

And then start all over again when the design proves unlistenable.

[minermark]

My LaScalla splits would be perfect for this experiment. any ideas ?

[ClaudeJ1]

Tubes actually have a larger linear region than the best solid state transistors. Pass has some very elegant transistor solutions, but you do get more linearity in the active stage from a tube. I'm pretty sure Pass would agree with that too.

Mike,

I believe that Mr. Pass's notes on modified cascode design is apropos here (i.e., "modulated cascode" on highly loaded power FETs) - that is the real contribution that enables Pass's power FET designs. His designs are also pretty elegant, i.e., simple, and avoid the following issues that tubes have:

1) high output impedance (requiring feedback to lower) that usually results in having to add more amplifier stages.

2) exceedingly low tube reliability for my tastes (in fact, it's just silly).

3) resulting even harmonic distortion of low-gain single-ended tube designs with low dynamic headroom, or the not-so-good effects of cascaded push-pull gain stages in order to achieve sufficient feedback to lower the output impedance to something tolerable.

4) cost to achieve a really good amplifier design.

These are important considerations.

I urge listening to one. I've got one in the D/FW area... [ ]

Chris

Nice stuff, Chris. I have always been a fan of Nelson Pass since the mid 70's. That guy really knows about non-linear behaviors of man-made devices from mother nature's materials and how to tame them. If the infamous "Bazoom 1" power amp had really existed, it probably would have been a collaboration between he and Bob Carver. LOL.

[ClaudeJ1]

I started a Bi-Amping Project about a month ago. After trying out a Marchand XM66, I settled on a pair of Hypex PSC2.400 Amplifers with imbedded active crossover that you can modify on the fly, with a PC. Using a type 'A' on the Altec Horns and tweeter, and running the Hypex Amps on the Bass Bin.

I think you need a PHD in Physics to understand the software for designing filters, but I got it working (I don't understand it yet) with my system and I have got to say it was the biggest improvement I have made to my system since I added the Altec midrange Horns 10 years ago. This is not a tweak, but the difference between a Heresey and a Khorn. I have unlimited headroom with 800 watts per channel Class D on the Bass Bins, with the smooth sound of SET amps 45 or 2a3 Moondogs on the Mids/Highs. It has completely transformed my system.

The great news is that the Hypex Amps were less than $800 for the pair at Madisonsound. This includes the Amps and Active Crossovers built into them. This project is for the DIY only! You have to make Boxes for them as they are plate amps and you can't just lay them on their side, Make Neutrik power Cables and XLR cables before you can even start. Then download software and be very comfortable with PCs and such. The Manuals are completely terrible and useless. Also, Madisonsound that sells the amps admit they know nothing about how to adjust the crossover settings. They are set up for 220 volts (they come from Holland) and they don't mention changing to 120 volts....Did I say the manual was useless?

Here is a picture of one in the Solid Oak Cabinet I made for it. They do sound Fricken Awesome though. 800 watts and SET amp silkiness.

I read up that that amp's design. That guy really knows what he's doing technically and represents "new school" of thought. Not that there's anything wrong with the old school. Looks like you have the best of both worlds. Your amps highly efficient and the output transfer function with loudspeaker compensation where it counts, and the less efficient part used where greater efficiency and low frequencies are not needed.

[minermark]

By summer I should be educated on the bi-amping and so far this really looks to be the next cool Mod.

I thank the forum members for their wisdom, we have all paid a price now and again for our experiments.

The info on these forums have saved me not only hard cash but headaches as well.

[bliss53]

I was thinking of using a TC Electric Impact Twin (24/192, interface/DAC/ADC), Pure Music software's crossover and filter features, and three inexpensive amps to tri-amp khorns. Any one have any experience with this method? I would also like to get some advice on some amps. I saw that parts express had low pricing T-amps. Any recommendations or advice would be helpful. Thanks.

[mdross1]

Our system is bi-amped through an active crossover. For years we were in the Mobile DJ business before we understood amplifier clipping could cause speaker damage. So after wiring in an oscilloscope a couple of times realized you could be clipping an amp and not really hear it. From then on we started using two amps with passive crossovers eventually wired in an active crossover.

Why it works for us is we never have to worry about hurting our speakers no matter the db level. With the power levels our gear has the speakers efficiency and our advancing age our ears need the most consideration.

[John Warren]

Anyone here using a bi-amp setup with just two amps and running the highs and mids together?

Jay

Yes (and I've done it).

The hi-pass amplifier section from a 2-way active filter can input to a MID+HF. A passive net between the amp and drivers is required to provide a low-pass to the MID and a hi-pass to the HF. Depending on sensitivities between the MID and HF, an L-pad will be required on one of the units. Amp selection is not casual and different amp combinations can alter the sound significantly.

Edited April 13, 2014 by John Warren

[Cornman]

"The pace, rhythm and timing of an amplifier (PRAT) need to match.

PP and SET do not match up well.

Amps with no global feedback do not match up well with amps with global feedback. "

I am glad this old thread was brought back up. I think most of have always believed SS was best at bass reproduction & tubes had the best mid range, or at least that was my experience. Since I started down the bi amp road I have never tried a different amp for my bass, thinking at the very least my Crown K2 was a good choice for the bottom end. . I have tried several different amps on the top end with very noticeable differences. If the quote above by djk is correct I have been missing out on another opportunity for improvement. My set amps on the top are zero feedback & the Crown has a dampening factor of 300.

Would love to hear from other bi amper's of there experience that they have tried matching both amp's with no feedback or not matching.

Need to get motivated & dig out some of my other zero feed back amps & try them on the bass. May bee the Bat vk60 or the Moondogs (uppps just sold the Dogies) Dang sold the First watt F3 as well - live an learn.

Edited April 13, 2014 by Cornman