Biamping, bass and amplifier type.

Excellent.
I really want to thank you all for your excellent, well written, well thought out responses.
Because of you I am really enjoying my renewed interest in audio.

Best results and most flexibility comes from single driver set-up. In other words, a separate amplifier channel connected directly to each driver. This means you cannot use a passive crossover. Your signal proceeds from preamp to active crossover and on to each amplifier. I believe this is the real definition of bi-amping and the only way to truly benefit from doing so.

Quality standmount speakers plus quality tube preamp/amp and quality sub float my boat.

I used to have a pair of Wilson Cubs (60Hz to 25kHz)on sand filled Sound Anchor stands driven by a 110 wpc Sonic Frontiers tube amp and matching tube hybrid pre. Frequencies below 60Hz handled by the original model Sunfire True Sub. The sound was to die for @ a relatively modest price of $18,000.

One night the amp caught fire (probably my fault for not dusting the tubes frequently enough). While the amp was being repaired, I replaced it with a SS B&K 200wpc amp. The sound degraded by about 30% (like everywhere: clarity, soundstage, speed, you name it).

IMHO, bi-amping should only be done w/ monos designed for that purpose. So that's like 4 amps! One would have to be immune from the Recession to do that.

I'd rather go with a true full range towers (like down below 30Hz)and either SS or tube 2 channel amp or something like my Cub/Sonic Frontiers system.

How can any of us argue with Mr. Von Schweikert?

It might be nice to see a discussion of all the success and failure stories of biamping but Audiogon's one-dimensional posting is impractical for that purpose because it would split in so many directions. Horizontal/vertical, active/passive, ... etc.

Here's something from Albert Von Schweikert posted
on the Von Schweikert board at Audio Circle. It may answer some questions, or raise new ones. In any case, the full discussion can be found here:
http://www.audiocircle.com/circles/index.php?topic=59529.0

From Albert Von Schweikert:
Hello Fellow Audiophiles,
Over the past 32 years, I've used bi-amping as a method to achieve more realistic sound quality. A decent, high powered solid state amplifier will give you explosive and tight bass power, while a smaller tube amp will give you the "air" and image float you are seeking from your sound system. Here are a few tips:
1. The bass amp does not have to necessarily be expensive, but make sure it has a large transformer and power supply to ensure "tight" bass. All of our speaker designs employ 4-ohm woofer systems, with a dip down to 3.5 ohms, so make sure the amp is stable into a 4 ohm load. Power requirements depend on your room size and how loud you want to go. I suggest 200-300 watts per channel if you have a large room and want an explosive dynamic range.
2. The tube amplifier can have as little as 20 watts per channel in a small room, but in a large room, you may want to have 50-100 watts per channel to avoid clipping at high volume levels. Due to the distribution of power over the frequency range of 20Hz to 20kHz, you can use a much smaller amplifier on the midrange and tweeter module. Use the 8-ohm taps on the tube amp, but feel free to experiment - it won't hurt anything to try other taps.
3. The "secret" to achieve "killer" sound quality is to ensure that the amplifiers have exactly the same input sensitivity. The amplifier with the lowest numerical rating, i.e. 100mV is much more sensitive than an amplifier with a rating of 500mV - the higher the number, the lower the sensitivity. You'll need to reduce the higher sensitivity by using a series input resistor. This can be installed inside your amplifier, directly at the RCA female jack leading to the input stage. If this sounds a little scary, then build an adaptor to house the resistor outside the amp. If you contact Michael Percy at www.percyaudio.com, he will advise you on what you'll need to get from him. Usually, a female RCA jack, a male RCA plug, a high quality metal film resistor, some plastic sleeving, and a short piece of high quality hookup wire is all that is required. Basically, you're inserting the resistor between the "hot" connection from the female RCA jack to the male RCA plug, and then using hookup wire to connect the ground leads. The entire assembly can be only a few inches long and installed into a plastic or Teflon sleeve to prevent short circuits. This adaptor is inserted into the signal path between your preamp and the most sensitive amplifier. As you can infer from this description, the adaptor is used in between your interconnect and the input jack of the amplifier.
Michael Percy sells these parts for less than $100 for everything you'll need, and he'll also help you select the proper value of resistor to match the sensitivities. Although this simple technique may sound like a "Micky Mouse" setup to "sophisticated" engineers that design chip OP AMPS and sell electronic crossovers to the PA industry, it is a very "pure" form of passive matching that will stomp the crap out of any electronic crossover I have ever tried.
4. Brands and Models: basically, put your money into the tube amp, since even inexpensive solid state amplifiers have stiff power supplies and enough quality to drive woofers with high speed transient response, high volume levels without clipping, and tight bass. Twenty years ago, Adcom built a 200-watt amplifier for around a thousand bucks new, and half that price used. Today, there are many expensive amplifiers that sound great, but you're paying for an expensive chassis, face plate, branding (advertising), and so forth. Instead, look for an amp with a large transformer and high quality power supply.
Tube amplifier choices abound, at all price ranges. Some of the best values are from China if you are on a budget, but large American tube amps from long established companies will be a good investment, with good resale value and the ease of repairs. Don't worry about the availability of tubes, they're going to be around for another 50 years or more due to the ever-expanding market for tube amplifiers.
Happy Listening from Albert Von Schweikert

My speakers are bi-amped. I run out of my preamp into a dbx Drive Rack PA. From there I go to a JRDG 102 amp which drives compression drivers through horns. The other amplifier is a Perreaux PMF 1850 driving 15 inch JBL woofers. Since the drivers are so different, what would be gained by using identical amps?
I gather that most of you are talking about using the inboard passive crossover for bi-amping. Is that correct?

You might want to consider a Drive Rack instead. Just bypass the native crossover and hard wire your drivers to the respective amps. Every parameter can then be modified by programming the dbx including time delay between drivers. There is a learning curve but if you like to fiddle around with your equipment, this device will open the door to infinite possibilities.
I got mine from Amazon and the price was very good. The pros advised me to go this way rather than Behringer.

There are 2 main types of potentiometer. Linear and Log.
They both may start (50kohm, say) and End, (zero, hopefully) but get there in 2 different ways.....'slopes'. They will only match resistance at those 2 points based on rotation.

As for bi amping, I have never heard a discussion of amp latency....that amount of time a signal takes to go THRU the amp. If it took JUST 1 millisecond longer for the signal to go thru the hi frequency amp, that would be like pushing the mid/hi drivers over 1 foot back. (away from listener)
This would start no end to problems.....smear of image, phase problems and more. The holocaust at/near the x-over frequency would be awful.

Before you toss this one in the round file, think about people who are good enough / discriminating / well eared enough to hear which way a fuse is installed.

I disagree with Stewie. He's gotten lucky with gain. Many amps will increase at different rates. Some amps will double output with a quarter turn while other only go up 10%. There is no way to compensate for different rates of gain.

I've biamped in just the way you're considering: a ss amp to the bass cabinets of my vr4 iii's, and dynaco mk iii monoblocs powering the mids and trebles. Though my ss amp puts out 170wpc, and the Dynaco's are rated a 60w, gain difference is not an issue b/c of two convenient configurations in my amp and preamp: 1) my ss amp has volume pot (per channel, but a single pot controlling both work just as well); and 2) my preamp has two sets of outputs. Those aren't requirements by any means, but it makes bi-amping a cinch. I keep the volume pots on ss amp at about 4, and then leave them alone; everything is controlled via the preamp, and I don't notice any imbalances across the volume range. And with the VRiiis, which get down to about 20hz, no subwoofer need apply.

I agree with Bob, save yourself the cost of an additonal amp and get a quality subwoofer. A subwoofer will produce way more bass than a biamped speaker.

I really want to thank everyone who has responded to my post for their well reasoned, thoughtful and well written replies.
Class (A) all the way.

Valid points are made here, I do not disagree with them. However I am coming from a place of personal experience in a real world system that I owned.

The difference in the gain was not audible to me. Never thought to pay any attention to it though, that being said, it never called attention to itself enough so that I felt I needed to. I simply found it worked for me and enjoyed this setup for many years.

As far as bass quality, the BAT S.S. product was deeper tighter and had more slam than the VTL even when it was run in Tetrode. The other benefit that may be worthy to note is the BAT VK-500 could handle the demands of my speakers on bass heavy material much better. Both are high current designs that can drive almost any speaker but the when the peaks hit... the VTLs would blow fuses. When I set the BAT up to run the bottom end the fast blow on the MB450's stopped popping for no apparent reason.

For the what it is worth department. I am of the camp that does not particularly see any real advantage of tube vs solid state offerings. So my input does need to be taken with a grain of salt if your are a tube guy.

I have had both, absolutely loved both for their strengths and weaknesses. My experience has been, a well voiced and engineered product in either camp is enjoyable. For me it is more of the interpretation of the music that the component does vs one technology being superior to the other. Much like different conductors will not interpret the same symphonic work the same way, each bringing various nuances out of it that the other does not see. I would be hard pressed to say that Karajan's conducting is more musical than Dorati's.

My system consists of Aerial 10T speakers bi-amped with Rogue audio M150's on the mids and highs and Rogue audio Zeus for bass.I usually listen at the volume control turned at 10:00 or 11:00 position.I get more decibels now but I think the souns was more pleasant when I only used the M150's full range prior to inserting the Zeus in the system.I could be wrong and I need more time to evaluate it properly.I should also mention that my brother visited me from overseas just recently and I had him listen to the system,after 2 songs he asked me to raise the volume ,which I did and then after further listening he pronounced that my system is bass shy and questioned if my cable connections were done right or not,I got offended to his negative comments,and decided to rotate the Zeus being a tube monster power amp with my other amp the Mark Levinson 27.5 solid state to see if that makes an upgrade .Also I thought of investing in an external crossover like the Bryston 10b.
Best regards
George

Would bi-amping with identical tube amps provide more substantial bass?
Seriously, how significant is the difference between tube amp vs SS bass?
I am not a bassaholic. I want it to be there in accurate proportion to the original source.

I disagree. The gain in the different amps will cause issues/imbalances. I would ONLY bi-amp with identical amps. Period.

Yes it would, the drawback is cost. If you go with an tube amp ss combo you have to divide the amount of money you have between them. Most folks I think choose one or the other and so they can put more money into one higher quality amplifier.

As far as Biamping goes....
I used to use VTL MB-450s for the top and BAT VK500 for the bottom. The result was most satisfying. However overtime the constant maintenance of the MB-450 became a bother. I also moved to a speaker that is not designed to be biamped. Made a very hard decision, and sold the VTLs off and now just run my system with the VK-500. I wish I could have put the VTLs on these speakers too, but as far amplification goes I have 90% of the sound quality I had before without the headaches.

However if you can afford it and are willing to care and feed your tube amps regularly it is the way to go.