Axiom Home Page Forums General Discussion Technical Questions For biamping M60s, crossover need to be removed?

I read on this article that in order to truly biamp, passive crossovers in the speaker must first be removed. Is this true? Im not really using 2 amps, just the surround back outlets from my SR8002 to split the frequencies and send a little more juice as can be done according to manual. I figured since I had the wire and the posts on the M60, I'd give it a try. My tyro thinking was that when you used both posts, you skipped the crossover (the sub/mid-high one), but upon thinking and reading that article, its seems to me that the split signals still will go through that crossover. Any help on this would be appreciated, I'm sorry for my ignorance on this issue.

The article you read is correct. Not only do you have to remove the passive crossovers, you have to use amps with separate power supplies, and place active crossovers before those amps.

No matter how the receiver maker has it labeled, you're not bi-amping.

Unless you want to go with an external active crossover, I do not think you want to bypass the internal crossover. The crossover does two things for you: sends the right signal to the right driver, smoothes the response of the speaker in the crossover region.

just plug it in normally and enjoy, stop worrying about Buyamping.

Perhaps Chris, JohnK or another smarter-than-me guy can answer this....aside from an active crossover, is it possible to design a three-way passive crossover, but in two completely separate units?....say one part to the tweets and mids and the other part isolated for the woofer so that two amps could be used in bi-amp fashion. I guess this would be like having a two way speaker with a single crossover, and a woofer (in the same cabinet)with it's own low freq pass or something similar, and each having it's own amp supply.

Sure. Some of the powered studio monitors have separate amps for the woofers and tweets. You would still need components to manage the signal in the crossover region.

A passive crossover is just a pair of high-pass, and low-pass filters with similar slopes. It's not one device which sends the bass in one direction and the treble in the other. It's the full circuit network which gets the name, "crossover."

I think (never have looked inside) that with the way Axiom has the removable straps between the "bi-amp" posts that they have designed their network like you're asking, Adrian.

So it goes:

One input into the low-pass to the woofers.
The other input into a high-pass for the tweeters.
The other input also split into a band-pass for the mids, but the band-pass itself is a pair of high-pass and low-pass filters paired together.

If that is the case, should you not be able to properly bi-amp since you are not bypassing any of the crossover components in doing so?

No, because the amp is still driving the full frequency range. The amp which is connected to the tweeters is still producing bass, then the crossover turns it to heat. So you end up using twice as much power to get to the same volume level.

OK, that makes sense. An active crossover would go before the amps.

Yes. Also, they're called active, because they require power of their own.

There are also digital crossovers which are done along with the signal processing. That's what I'm studying right now.

Erik, yes, true bi-amping(which has some modest benefits)is complex and is almost never done for home setups. Basically, it requires separate amplifiers(receivers have only one amplifier with several output channels)and an external crossover(usually electronic)before the amplifiers so that each amplifier gets only the desired frequency range to amplify. So yes, the internal speaker crossover has to be removed or at least by-passed to get rid of its inefficiencies.

The pseudo-bi-amping that some receiver manufacturers promote as a feature is meaningless, and no more "juice" is sent to the speaker by simply connecting the same single power supply section in the receiver to the speaker through two sets of output transistors(which have no power of their own and simply act as valves)rather than one.

Thats unbelievable John, I feel like almost the whole audio market is full of gimmicks and scams. Why do they even offer these options, in all honesty, is it for products to look more enticing? And why do our speakers and most others have 2 pairs of binding posts then if the majority never truly biamp? I enjoy my sound now, but I figured I would try it as not to waste a potentially helpful feature. I also like asking these questions on here because you guys are full of knowledge, and even if I never do any of these tweeks it helps satisfy my idle curiosity (electronics is very intersting stuff). In the end it all comes down to the quote in JohnK's signiture, how true!

Dealers. Dealers require a lot of these things so they can sell the speakers and more gizmos.

Also, people will buy it.

There are a lot of folks who buy into stuff like this. I have a brother in law that has an inexpensive set of Polk towers that is powered by an Onkyo and he uses the bi-amp feature and swears he hears a difference. Try and tell him there's no difference in sound; he'll argue that fact there is a difference.

I wonder if Axiom would build an M80/VP180 with three pairs of binding posts, and easily bypassed crossovers (well at least able to be bypassed by removing a speaker and moving spades from the crossover output directly to the inside binding posts).

Then they could be advertised as tri-ampable, and actually be used that way by someone who knows that they are doing.

The power of the placebo effect. Thats a cool and seemingly simple idea Neon

Hi Club Neon and all,

I think that is extremely unlikely, seeing as how both Ian, the founder and owner of Axiom, and myself believe that there is no advantage to bi-/tri-amping in domestic setups.

Moreover, it then puts the spectral balance (tonal balance) of the speaker into the hands of the consumer, and we do not want that to occur. We spend a lot of time and research doing double-blind tests to get the tonal balance excactly right--you all love the new VP180, right? It's taken years for us to get a big center that I'm satisfied with, in fact, thrilled with.

Likewise, the new M60 v3 is a big improvement over the v2, especially if you're a really critical listener to male and female vocals and dislike slightly edgy brasses, etc.

Why would Ian and I want to put the subtle nuances of tonal balance and crossover adjustment into the hands of consumers?

No way.

Regards,
Alan

Very good point. Thanks for your response.

+1

I was wondering if there'd be an Axiom guy commenting on this. Pretty much exactly what we've heard from Ian in our conference calls...

You're discussing bi-amping in those calls?

Ya, he tried to prove a point by talking over two phones at once but nobody bought into it.

Or he tried to talk into both ends of one single phone!

Or both his ends talked into a single phone....

Sorry, I'm done now.

You don't want to be the guy to use THAT phone last.

You mean next, right?

Yes!

What exactly is happening when you do use the 2 sets of wires and switch the "Speaker C" button on the back of the Marantz to "biamp"? Is it just like using a really big gauge wire to send the same signal to the speaker? And why must that bridge be removed between the posts? (If you guys dont shoot me for all these amateur questions now you never will!)

Not exactly. If you were biwiring but leaving the bridge on, you're using a big wire. That's what I do, just for the hell of it.

However, on the Marantz, you're actually using two electrically separate signal generators. So if you leave the strap on, you're routing signal from one amp into the other and vice versa. Then you get magic smoke.

Here's what happens when a receiver with one power supply is set to bi-amp:

It's single pool of power is now flowing from two sets of outputs. This alone isn't bad. Some amp designs use multiple output devices on a single channel for better power handling.

BUT, those amps are designed to run bridged together, which requires some planning in the circuit design. When two separate outputs are activated with the same signal, but are not designed to be bridged they cannot be connected together (or Bad Things™ will happen).

So the bus bars have to be removed from the speaker. Now you're dividing the available power between two outputs. Again, not so bad N / 2 * 2 still equals N. Though that only applies if you can use the full power from each output.

When powering a full range speaker, that has no ultra- or infra- sonic filters (like most speakers), most of the current no matter it's alternating frequency can find a way through the system. The crossover will route some through the tweeter, mid, or woofer, but it follows its path of least resistance and winds it way through.

But when you cut a speaker in half, and have two separate systems, one which can only pass highs, and one which can only pass lows, much of the electrical energy will be turned to heat in the crossover network because there's no path for it.

So instead of having (N / 2) * 2 usable power, you end up with (N / 2) / 2 * 2. Or N / 2, meaning you've lost half of the usable power to heat. Those number are really rough examples, but the principle is true. Dividing the power across multiple outputs, and then not being able to use that full output because crossover network blocks it causes the receiver to have less available for output than running one output into a full-range speaker system.

Great explanation Chris.

He's such a showoff!