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I have a question about biamping actively and whether its worth it to go that route. Currently, I have a pair of Dynaco MKIII mono amps powering the mids and highs on a pair of Kef Reference Series Model 1's. The lows are being powered by an Integra DTR 10.5 receiver. I am using the built in crossovers in the Kefs.

I read from a few different places that if you want to biamp, you really have to use active crossovers, which is odd, considering a large amount of high end speakers have biamping posts. You'd think if they made them with the intention of biamping, you would not have to void your warranty to do it properly. Anyways, it seems to me that gutting the passive crossover in favor of an active crossover is basically setting fire to all the manufacturers hard work. The manufacturer, I would imagine, makes these measurements in an anechoic chamber, with extremely expensive measuring tools, a fat budget and a guy with a PhD in something pushing buttons. So who am i to presume that I can buy a couple pieces of measuring equipment, come in, and expect to do anywhere near as good of a job as they do? Am I correct that the real benefit of doing active crossovers is reduced stress on my amps? If that's the case, I think I have plenty of power to spare, and besides, those filtered out frequencies are attenuated away by my passive x-over, and cause very little strain on my amp, right?

What do you guys who biamp do? Passive or active?
 

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Active crossovers have several advantages over passive networks.

whether you can design and implement it to actually be a sonic improvement is a different story.
 

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Active crossovers have several advantages over passive networks.

whether you can design and implement it to actually be a sonic improvement is a different story.
has it been your experience that diy-ers switching to active crossovers results in sonic improvements, or are you seeing people mess things up? What benefits does one gain by switching to an active crossover? Increased flexibility?
 

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What do you guys who biamp do? Passive or active?
Bi-amping by definition is active. It's used to overcome the innate deficiencies of passive crossovers and full range amplification. So-called 'passive bi-amping' accomplishes absolutely nothing. Speaker and AVR manufacturers set their gear up to allow for it for one reason and one reason only: To make a sale to someone who doesn't know that it accomplishes absolutely nothing.
 

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An active XO still requires measurements and design just like a passive XO. Theres absolutely no difference in the design process. I would not void your warranty for the very small gains active provides unless youre very comfortable doing XO design.

Even then, proponents of active always over inflate the benefits.

Impulse Audio Canada
 

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I bi-amped actively for decades but am not now. Just do not feel the benefits for home use outweigh the effort.

I had not heard about "passive" bi-amping until fairly recently and was rather shocked when I learned what it meant. To me, "passive" bi-amping meant a passive line-level crossover instead of an active line-level crossover, not "passive" in the sense that the amplifiers were fed the same signal and all that happened was you separated the high and low passive speaker crossover inputs. The latter seemed like purely a marketing ploy and nothing I have read since has provided a sound technical basis for it. But, in addition to being an audiophile and musician, I am mostly a hairy-knuckled engineer who doesn't understand when something goes against both technical sense and every listening test I have performed.

I have thousands of dollars in measurement mics and SW but frankly REW and a good CSL-calibrated mic does about as well. (Yes, I have compared them, and it is true for me, not sure whether to be happy or cry that it can be done so cheaply now.) I also have a couple of grad classes in acoustics and years of experience but audio is not my day job. After going back and forth I decided a single big power amp provided a much better trade for my insensitive planars than spending another round of hours (days, weeks) optimizing an actively bi-amped system to provide what would likely be marginal improvements upon what the speaker designers did to begin with.

Most professional systems are bi- or tri-amped but more for greater efficiency and lower (amp) cost and better energy/thermal management than because it sounds so much better.

I'd send the money on music and movies, the kid's college fund, or the retirement fund instead. And spend the time doing something fun.

IME, IMO, FWIWFM, YMMV, my 0.000001 cent (microcent), etc. - Don
 
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Here is a quote from my owners manual
"When you use bi-wiring-enabled speakers for the front speakers, you can make the bi-amp connection. In this connection, the front and surround back speaker terminals will be used for tweeter and woofer, respectively."

Doesn't the fact that the manual differentiates how each speaker terminal should mate to the high or low terminal on the speaker indicate that there is at least some form of crossing over present in the signal path to the amp? If both the front l/r terminals and surround l/r terminals are being fed an identical signal, I don't know why the manual would advise to hook the speaker up in a particular manner.
 

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Don - I feel the same way as you do in general, regarding biamping. I did it for a while, then felt there was little benefit and stopped. I just got these Dynaco tube amps a few days ago, and they sound amazing. The drawback is that they are light on power, and they are especially light in the bottom end. My receiver on the other hand, has gobs of power and will fill in perfectly for the woofers.
 

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Doesn't the fact that the manual differentiates how each speaker terminal should mate to the high or low terminal on the speaker indicate that there is at least some form of crossing over present in the signal path to the amp?
No, and that's one of the reasons why it does nothing. If it did there would be a provision in your manual for setting the crossover frequency.
 

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An active XO still requires measurements and design just like a passive XO. Theres absolutely no difference in the design process. I would not void your warranty for the very small gains active provides unless youre very comfortable doing XO design.

Even then, proponents of active always over inflate the benefits.

Impulse Audio Canada
Agreed. I think in the professional space it is a definite advantage if a speaker will be subjected to 18+ hours a day of reference level playback. In that instance the heating of crossover components can impact the FR. Assuming drivers that are not thermally compressing, an active crossover will give the same consistent results over time.

In the consumer space, speakers are not typically abused in that way.
 

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No, and that's one of the reasons why it does nothing. If it did there would be a provision in your manual for setting the crossover frequency.
OK. Sounds like biamping is pretty much something I should stay away from unless i want to dive in head first with some active xo's. Thanks for all the info.

If i can ask 1 more question: If I am running preouts to an amp for my mains, does that take 'pressure' off my receiver. Or is my receiver producing wattage for those speakers regardless of whether they are actually hoooked up? I ask because It seems like the receiver gets pretty warm whether I have all my speakers ran through it, or even if i'm just basically using it as a pre/pro.
 

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There is a LOT going on in modern AVRs and the power amps are just part of it. I have an AVR that gets hottest over the DSP board in normal operation (not over the power amps). Your amps are more than likely still on drawing minimal bias current, but using an external amp does indeed take some of the "pressure" off your AVR. Whether that matter or not is hard to say...
 
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While Active Crossovers can be nice, the Technical Threshold is pretty high.

At what frequencies will you crossover?

What Roll-Off Slopes will you use in the crossovers?

Specifically what Active Crossovers will you use?

Do you understand how you will have to modify your existing speaker, so they can use Active Crossovers?

To answer these questions, you need a pretty deep and intimate knowledge of your speakers, far more than you can typically get by reading the spec sheet.

https://www.kefdirect.com/kef-reference-1-bookshelf-speaker.html

Are these your speakers?

To add External Crossovers, you will have to take the speakers apart and disconnect the internal crossover, and connect the various section of the speaker directly to the speaker terminals. The speakers are 3-way, but do they have THREE PAIR of speaker terminals on the back? Do they even have 2 pair of speaker terminals on the back?

If they only have 2 pair of terminals then you are going to have to continue using the Mid/High Passive crossover.

The Specs might tell you where the crossover frequencies are, but they don't tell you the slope of the crossovers for each driver. For example, the woofer could roll off at 6db/octave, the Mid on both they high and low could roll off at 12db/octave, and the tweeters could have a sharp 18db/octave slope. What do you need? What are you going to use?

KEF put considerable design effort into designing these speakers. So, the result of you fiddling around, could be better, or it could be worse.

Then there is the matter of the active Crossover itself. I can think of only one company that makes a Hi-Fi Crossover, and the truth is I can't even remember the companies name. But I do remember that the crossover was several thousand dollars.

You can us PA system crossovers, but they tend to use very steep FIXED 18db and 24db slopes. If you want to control the slopes, you need to move to a Speaker Management System, which near universally digitize the music, process it in the digital domain, then convert it back to analog at the output. And, tend to be on the expensive side. Though given the system you have, perhaps not prohibitively expensive.

WIth the Crossovers remove, you speaker become vulnerable. If anyone connect the speaker directly to an amp without the Active Crossovers, the speaker are in danger. Though with a Half-Active and Half-Passive system, as you would likely have to do, the danger would not be high as the Mid and High crossovers would still be in the system.

Then there is the final question of whether your drunken ham-fisted friends can keep their hand off the controls. It gets to the point, where you and only you are qualified to operate the system,

So... yada-yada-yada... the technical know-how and skill level are pretty high to attempt to modify and use a system like this.

Your speakers run in the neighborhood of $8000/pr, are you sure you are willing to risk them?

Steve/bluewizard
 

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If you want to control the slopes, you need to move to a Speaker Management System,
Which is a marketing term more than a technical difference. Almost all SMS implement IIR filters which are no different to their analog equivalents.

And, tend to be on the expensive side.
$275, $500 if you want it in a box. Hardly expensive.

WIth the Crossovers remove, you speaker become vulnerable. If anyone connect the speaker directly to an amp without the Active Crossovers, the speaker are in danger.
Rubbish. In 30 years of direct connected multi-amping, I've never had a damaged driver.
 

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Im not selling anything but i want to add a third optio - the digital crossover.
A digital crossover is an electronic crossover, as is an analog electronic crossover. I don't know what your link is to, as it's not functional, but where room correction is concerned that would be accomplished with digital EQ, not a digital crossover, although some products incorporate both.
 
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Separating the crossover reduces interaction and out-band-frequencies are not amplified because there is no load.


Here is an interest post about active networks:


https://www.sweetwater.com/forums/showthread.php?44674-Bi-wire-vs-Bi-amp&p=232865#post232865


I have don't SBT's with the Salons and I find the benefit at any volume level. Which says to me, this is not a power issue.
Here is post where Revels (Voecks) responds to a bi-aming question:


http://www.avsforum.com/forum/89-speakers/710918-revel-owners-thread-267.html#post40821322
I too, have heard such effects from passive bi-amping. If the speaker is competently designed, you would never want to insert active crossovers, except for a rare case in which the transfer function required to properly “cross-over” the speaker is published and properly implemented. Otherwise, passive bi-amping can offer sonic improvements. One reason is likely that the impedance outside the pass-band rises dramatically—thus resulting in the amp not being significantly utilized outside the intended frequency range. So for example, an amp dedicated to the high-frequency section of a speaker (whether that is a tweeter alone, or perhaps a tweeter and midrange), will not have significant current draw at low frequencies, resulting in lower distortion.
You can try passive bi-amping at home with a single speaker. This is how Revel compares speakers.
Try it with one speaker and decide. Active crossovers are not required.


- Rich
 
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