Question on bi-amping TSW-910 speakers....

[tysontom]

I think Steve is exactly right: your setup is not really doing anything, mainly because you are sending an amplifier signal with a 400 Hz low-pass filtering into the woofer section, but that filter is voided by the 200 Hz passive crossover already in the signal path between the amplifier and the speaker drivers themselves. The second amp is presumably hooked to the top terminals with a 100 Hz high-pass filter, thus falling below the actual crossover to the woofers, again at 200 Hz, effectively doing nothing.

Differences you hear are probably due to slight level differences in the two amplifiers, unfortunately creating a sort of coloration to the sound; i.e., the upper group is probably playing at a higher relative output level than the woofer section, thus giving a sense of "clarity" that your wife noted.

--Tom Tyson

[rrcrain]

Tom,

Anything's possible. The two amps are as identical as humanly possible but I admit there's always minor differences in electronic components. What I've not mentioned, or mentioned poorly is the apparent improvement in the bass as well. For whatever reason, it sounds as if the speakers are reproducing a lower frequency than they do when not biamped. I absolutely do not think this is the case. Rather, my suspicion is the bass is perhaps less distorted.

Here's the bottom line. For my ears and those that have listened to my system, adding the active crossover was an improvement. We can debate the merits and or ramifications of this till the cows come home, but that's the reality. I've had some very critical ears listen with me and they've walked away with the same opinion.

[tysontom]

Richard,

Yes, definitely, it's whatever sounds best to you that counts, and we don't want to disparage that in any way. If it sounds better, stay with what works for you. I think that what Steve and I were trying to figure out was how this thing was working, that's all.

Best regards and good listening,

--Tom

[rrcrain]

Tom,

To be fair, I've wondered why we ( me, my wife, family and friends) hear the effect we do as well and have been forced to guess and hypothesize. Either one of these amplifiers are more than capable of driving both speakers on its own to levels that will rattle the floor joists without distorting so I don't believe its due to lower distortion. I doubt I'm asking more than 50 watts at peak from an an amp on a normal day. They are conservatively rated at 315 watt into 4 ohms. Double that for the peak.

Maybe it's due to the IM being lowered, but I doubt it. By the book, these amps have an impressively low IM and THD as is. Heck, my tube preamp has a rated THD 40 times higher than the amps rated THD and I can't hear it distort.

I thought perhaps I'd connected the two amps to the speakers out of phase and reveresed one set of speaker wires as a test. It made it worse.

The one thing that's an absolute. To anyone listening to this set of speakers driven by these two amplifiers, a passive biamping setup sounds worse. Disjointed, out of phase, just not quite right. With the active crossover, it's clearer, a better sound stage (more 3 dimensional) and the bass is crisper, cleaner, better defined.

And perhaps it's the crossover "coloring" the sound in such a way that everyone thinks it sounds better.

To close. I can't explain why. All I can honestly say is it does.

[Steve F]

Richard,

As Tom said, there is certainly no intent to criticize or disparage your setup. We're just trying to figure out the mechanisms at work that might contribute to an apparently unmistakable improvement in sound.

While I still maintain that your setup is not "bi-amping" in the absolute technical, semantic sense, I think you've identified what's responsible for your audible improvement:

"As an experiment, I did only connect the bass section with a full signal and was rather surprised to hear Shaina Twain coming out of the bass drivers. Not clearly and not all that loud, but the vocals were intelligable if only barely. With the active crossover, there's less "garbage" for the bass crossover to block/reject or filter out."

That's likely it. Your external x-o with its 400 Hz LP is reducing the low-level, upper bass/lower MR frequency artifacts that would otherwise "cloud up" the sound--if even just a little--and the elimination of that UB/LMR "haze" is what gives you the sense of greater clarity.

Now that we've all talked it through and you've told us that, I have little doubt that that's what is in play here.

Good going! Nice set-up, tangible results.

Steve F.

[tmomirov]

Hi eveyone, my buddy vintagechris finally talk me into becoming a member here since i have numerous pair of AR speakers as of right now i'm putting bi-amping on the side burner .i recently just purchased a phillips ah578 amp i'm going to try as a stand alone my question is where can i aquire a manual for these AR tsw 910 . Information on these are far and few between .i currently own 2 pair of the AR9 and i'm powering them with 2- mcintosh mc2500 amps .Are these tsw910 similar to the same specs as my 9's?Thanks Greg.

[ARdude]

I own a pair of TSW 910's. Purchased back in mid 1980's.

I do have the owner's manual.

What imformation are you looking for?

[Gerry S]

OK, guys (I'll probably take a lot of flak for posting this). About "bi-amplification" in general. I’m not an expert on this topic but have some experience with it. Many decades ago (before I turned "pro"), I got my friend (Poh Ser Hsu (before HE turned "pro") of Hsu Research) to design an electronic crossover for me. I wanted that "disco punch" in the bass I craved, which my regular home speakers couldn’t provide without audibly distorting or physically destructing.

This x-o fed LF signals below 100 Hz to a hefty amp. The amp then drove a cutom built ported enclosure approximartly 3.5 cubic feet in volume. This cabinet housed a 15" driver and the system was tuned to 35 hz. The x-o is a 4^th order L/R network with a substantial boost @ 35 HZ, which is the lowest bass I would ever need for my musical taste (rock, pop, and audiophile "classical" stuff).

Frequencies above100Hz be "high-passed" electronically to my "main" electronics and speakers (can’t remember the details about the high pass filter). Essentially, this was an "electronic" version of what’s known today as a passive "sub-sat" system (which I did commercially for BA in the 90's). The results was literally "earth -shaking". The only way I could obtain these results was "bi-ampying". A "passive" crossover with such steep slopes designed for a 100 Hz crossover point would be HUGE. It would also probably be more expensive and less effective in the long run.

"Pro audio" has been doing bi-amping well before "hi-fi" manufactures employed it! They did it because it’s a more efficient approach to deliver high SPL "cleanly" without resorting to massive crossovers and behemoth amplifiers if done "passively". For the pro market, this is a cost - effective approach, despite added electronics and the complexity of blending it all to get it "right". But, the people doing this are "pros" with technical knowledge with sophisticated test equipment and the knowledge to analyze what they measure. There is usually a specific goal in mind when "tweaking" all the electronics: increased performance and reliability when delivering high SPL to large audiences for a given venue.

For demanding "audiophile playback applications", It’s well known that "bass frequencies" is where most power is generally needed. With "audiophile recordings" containing high level transients in the upper frequencies, high power is required here as well, but briefly (for those +13 to +17 db "transients"). I've never personally owned an AR product like the AR9 where "bi-amping" would be an option. But I designed the crossovers for the Boston Acoustics T1030, which is "bi-amp" capable.

But "bi-amping" can mean several things from a technical standpoint and applicable to the same speaker system. "Bi-Amp" translates (for me) TWO amplifiers for a single speaker system ("Tri-Amp" means three amplifiers). The use or non-use of a crossover whether internal, external, passive, acive or any combination there-off is really moot here. The relevant issue here is what one wants to achieve using more than a single amplifier to drive one speaker system !

In the case of the Boston T1030 (and probably the AR's), it is both capable of being "bi-wired" (which I've never truly understood the purported benefits of) and "bi-amplified". In " bi-amplifier" mode, removing the jumpers on the speaker plate disconnects the two passive crossover circuits located inside the speaker enlosure from each other that are normally "tied together" when the external jumpers are in place. These two circuits consist of the low frequency crossover circuit (low-pass) that prevents higher frequencies being fed to the woofers, and the mid-range/tweeter circuitry (high-pass filter) which prevents bass frequencies from reaching those drivers. I'm guessing most owners of "bi-amp capable" speakers never use this mode.

For the BA's (and probably the AR's), when the external jumpers are removed, two SMALLER "full range" IDENTICAL amplifiers to drive each section (woofer section and mid-range/tweeter section) should theoretically sound "better" than a single humongous amplifier driving the system with the jumpers tied together. But why ? Primarily higher and cleaner SPL's when the entire amplifier/ crossover/ loudspeaker interface is driven to it's limits.

At low to moderate playback levels, there should be virtually NO sonic difference when comparing the speaker that's "bi-amped" to the same model speaker that's driven conventionally (a single full range amp). Only when "pushed hard" will the bi-amped unit sound cleaner. When "power hungry" bass frequencies "clip" the amplifier driving the woofers, the distortion generated by the bass amplifier doesn't reach the mid-range and tweeter drivers (which is driven by it's own amplifier). For the example I just cited, the internal crossovers are STILL used; no additional crossover circuitry is needed or desired IF the ORIGINAL sonic signature is to be replicated.

I mentioned "full range" and "identical" amplifiers when "bi-amping" because it's imperative that the amplifiers have the same phase with respect to each other. It's also critical that the frequency response of both amplifiers be "flat", without prematurely rolling off the frequency extremes, and the gain of each amplifier be closely matched as possible. If ANY of these conditions mentioned are not adhered to, then you will have changed the intended tonal balance (probably for the worse) the designer intended. Using different brands, types, size or even different model #'s of the same amplifier brand greatly increases the probability this will occur.

Passive crossover design is a compromise between what's "do-able", what's desirable, what's practical, and what's "cost effective". A "cost-no-object" passive crossover circuit would be VERY expensive with possibly (probably) a minumum performance gain despite the added cost and complexity compaired to a less complex passive network. The lower the crossover fequency and or the greater the "slope" of the passive crossover filters, the larger and (more expensive) the component values will be. Like anything else, one reaches a point of diminishing returns.

On the other hand, using a versatile external elecronic crossover can "solve" driver "issues" (all drivers have "issues") in a way not easily attainable, pratical or even possible using passive components. But, the additional amplifiers and active crossovers would be pretty expensive and complicated to incorporate even at the manufacturing level. Done at the "hobbiest level" (where the built-in passive circuitry is totally removed/ by-passed), "true" bi-amping (or multi-amping) can be prohibitively costly. And that's not figuring in the REQUIRED test equipment and knowlege to match all these components "properly".

Done "properly", it's quite possible to have a vastly superior sounding system when compaired to the built-in "original passive crossover". But again, the cost and complexity would be several magnitudes higher compaired to a simple passive crossover driven by one amplifier (the appoach used by the vast majority of consumer speakers users, including the readers of this forum).

Consumer speakers (like the AR's and BA's mentioned) which can be bi-amped are intended to be used with the crossovers that are "built-in". Bi-amping is provided as an option for those who wish to push these speakers to their performance limits using two smaller amplifiers instead of one humongus one. Even if one had infinite amplifier power available from these amplifiers, the drivers themselves would eventually reach their performance limits. Which is why I built my humougous bass enclosure in the first place.

Today, "Bi-amping" is no big deal because many companies offer them in the form of "powered speakers" that has all crossover points and slopes integrated into the amplifiers driving their respective drivers. NO test equipment or special expertise to "get it right". Also, adding a dedicated "powered sub" is in reality another form of "bi-amping", because a second amplifier (usually with an electronic crossover built-in) is employed.

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I'd welcome other peoples experiences with bi-amplification in general . I'd especially like to hear if people found "improvements" when bi-amping vs a single amplifier, and to what degree.