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Active Bi-Amping/Tri-Amping FAQ


Chris A
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With active crossovers do we take out the entire notion of amplifier designer “voicing”?  I mean boosted bass, rolled off highs, recessed mid, etc, does any of that matter anymore?  What amp characteristics are still valid with active xo?  
Is amplifier smoothness measurable?
dynamics? 

Not being sarcastic, I’m really wondering what to look for if I want to change amps someday? 

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8 hours ago, VDS said:

With active crossovers do we take out the entire notion of amplifier designer “voicing”?  I mean boosted bass, rolled off highs, recessed mid, etc, does any of that matter anymore?

This is typically called a "room curve" (as opposed to a "house curve" that's only used in large commercial venues--and that's not appropriate for home-sized listening rooms).  Room curves are discussed in Toole's book (to some extent).  The topic of room curves is probably beyond the original scope of this now 10-year-old thread, but can be discussed here.  It's something that is easily incorporated into DSP crossover setups.  I'd recommend moving that discussion to the following thread, and asking your question there:

 

 

I find that the subject of room curves and the subject of "The Missing Octave" are indistinguishable subjects, and that the reason why room curves are used is largely due to others trying to avoid having to do something about their badly mastered stereo recordings (and sometimes multichannel recordings, too), instead resorting to using a "one size fits all" room curve in the hope that it might solve their problems.  Additionally, I find that most room curves fail to identify their root cause of having to using them.

________________________________________________________________________________________________

 

8 hours ago, VDS said:

What amp characteristics are still valid with active xo?  Is amplifier smoothness measurable? dynamics? 

Generally, the recent experience that you've had with balanced-to-unbalanced connections is appropriate, but that discussion is probably better discussed in the thread that you started:

 

Other than that, the discussion of amplifier characteristics (outside of the discussion of balanced--unbalanced connections) is a long and contentious one among audio enthusiasts.  Usually, the readers of this thread arrive here with their own heuristics and biases with regard to amplifiers for multi-amping applications (which is the subject of this tutorial).  I tend to leave these discussions to those that seem to have strong feelings about whatever amplifier topologies and brands/models that they think is best. 

 

There is a long history of those trying to use particular amplifier type nonlinearities to solve all kinds of EQ and other issues in their setups, and I find these discussions are not unlike the old snake oil salesmen arriving in their wagons to sell to unsuspecting customers, then to exit the scene about as quickly as they appeared...

 

 

Chris

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2 hours ago, Chris A said:

There is a long history of those trying to use particular amplifier type nonlinearities to solve all kinds of EQ and other issues in their setups,

I’m starting to feel like “synergy” is basically trying to find the amp with the right non adjustable EQ to pair with non adjustable,  passive crossover settings.


If we factor in the adjustability of active crossovers to control the speaker/amp “synergy”, then is the idea of “upgrading” an amplifier still valid? 
 

I should try my “bottom of their line” Emotiva amp against my Pass,  both properly EQ’ed with Xilica, and answer my own question.

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53 minutes ago, VDS said:

I’m starting to feel like “synergy” is basically trying to find the amp with the right non adjustable EQ to pair with non adjustable,  passive crossover settings.

JOrT.gif

 

53 minutes ago, VDS said:

If we factor in the adjustability of active crossovers to control the speaker/amp “synergy”, then is the idea of “upgrading” an amplifier still valid? I should try my “bottom of their line” Emotiva amp against my Pass,  both properly EQ’ed with Xilica, and answer my own question.

The answer here is more of an emotional one than a rational one, I've found.  I have said on many occasions on this forum that once you get to Jubilee (or K-402-MEH) performance levels, the amplifiers make a lot less difference.

 

Since I listen for the decays and the very sparkling highs of orchestral and other natural acoustic music that others here may not value as much, I like my First Watt F3 for that last 1% or less of "presence", but the truth is that--if you swapped out my F3 with one of my D-75As, I might not notice the difference.  That's how little difference that I've found there really is--once you dial-in the SPL and phase response--using a good compression driver (like an Axi2050, for instance). 

 

EDIT: One of the things that I have found is that there are amplifiers that have inherently higher modulation distortion--that sound opaque and dull--uninteresting.  These amplifiers are usually on the bottom of the price lists (but not always).  I'd recommend class AB or class A amplifiers--not class D, but you can certainly try anything that you desire.

 

Chris

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29 minutes ago, Chris A said:

I have said on many occasions on this forum that once you get to Jubilee (or K-402-MEH) performance levels, the amplifiers make a lot less difference.

After using the 402 as the mid horn, with BSM 4592 mid, and now as a 2way, with Axi2050, that the horn creates more “separation”, dynamism and clarity than then Greg’s  Fastlane Horn that is in my Cornwalls. (The fastlane horn being a remarkable improvement over the Cornwall 1’s original horn, (k700 or k600?) so kudos to Greg!)
There is a slight edginess that remains, but that could certainly be my room and may not be solved  by a different amp.  
maybe I should have put these comments in a 402, I’m getting off topic.

 

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36 minutes ago, VDS said:

There is a slight edginess that remains, but that could certainly be my room and may not be solved  by a different amp.

This is in the category of "room curve", and the condition of the source music that you're playing.  I've found that some third-party horns/drivers typically are not providing a flat on-axis response out to 15-20 kHz--the Crites CT125, which rolls off the high end quite a bit from the K-77, and a lot of folks apparently equate that with "better" when the real problem is the boosted highs by the mastering guys in the music that they're playing. 

 

For instance, here is an SPL response plot of a 1979 Cornwall with a CT-125 tweeter:

 

Cornwall (1979) - No EQ.jpg

 

Notice the downward tilt of the SPL above 6 kHz?  That's because the CT-125 tweeter doesn't have the same sensitivity on-axis as the K-77--it's a couple of dB lower in sensitivity.

 

It's a common story to assign blame to the loudspeaker for issues that the loudspeaker isn't responsible for.  By using a little 0.4 dB/octave downward tilt of the SPL response within REW's EQ facility, i.e., the PEQ optimizer, you can almost effortlessly recreate this "softening" effect with your K-402-MEH(s).

 

Chris

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On 7/15/2021 at 9:48 AM, Chris A said:

Notice the downward tilt of the SPL above 6 kHz?  That's because the CT-125 tweeter doesn't have the same sensitivity on-axis as the K-77--it's a couple of dB lower in sensitivity.

 

It's a common story to assign blame to the loudspeaker for issues that the loudspeaker isn't responsible for.  By using a little 0.4 dB/octave downward tilt of the SPL response within REW's EQ facility, i.e., the PEQ optimizer, you can almost effortlessly recreate this "softening" effect with your K-402-MEH(s).

 

You are reminding me that I need to get a umik and run sweeps. I would like to know how my APT50 measures, since it is on the Eminence 100x150 horn.

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On 5/18/2010 at 4:41 AM, Chris A said:

Do I need to disconnect my speakers’ passive crossovers from my drivers?"

 

Yes. At least the woofer (or low frequency driver) must be disconnected from the passive crossover to permit bi-amping.


in my current situation, I haven’t disconnected the crossover in the bass bin of my klipschorns, but I am using an activeDSP to break out the low frequencies before they reach the amp for the bass bin. Of course this frequency limited speaker level signal is still passing through the bass bin crossover. From your statement here, I read it as it’s a must to disconnect the bass bin crossover and wire directly to the driver. Is this correct? And if “yes” why? 

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2 minutes ago, DVDMike said:

From your statement here, I read it as it’s a must to disconnect the bass bin crossover and wire directly to the driver. Is this correct? And if “yes” why? 

Yes--to get the electrical resistance and reactance of the passive crossover networks out of the circuit (which causes your amplifiers to work that much harder, and introduce additional phase shifts).  The best situation is direct-coupling the amplifier output to drivers.

 

Chris

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10 minutes ago, Chris A said:

The best situation is direct-coupling the amplifier output to drivers.

Ok, thanks. That “should” be easy enough. But I’ll need to research how to access the bass bin crossover. 
 

this is all getting me into the mindset of moving to tri-amping and eliminating the crossovers completely. 

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Before I go to the trouble to move my speakers out from the corner to bypass the bass bin crossover, can I get enough access to the crossover to disconnect the driver connection from the crossover just by removing this cover? Or do need to remove something else as well? 

DA4C37E0-4E72-4CEB-BC0F-A49507A53D30.jpeg

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Someone that knows the AK3 wiring should chime in here. 

 

The old PWK-era style of wiring had the two leads from the woofer coming directly out of the bass bin cabinet--and those are what you're looking to attach to.  Those older crossovers allow the bypassing of the bass bin choke (coil) directly at the connector strip in the top hat. 

 

Chris

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1 hour ago, Chris A said:

Someone that knows the AK3 wiring should chime in here. 


I created my own thread for this question so as not to clog this one up with my offshoot 

 

 

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For anybody that is using active crossovers with digital source.  Has anybody heard a difference by upgrading Dacs? (Skipping the “dacs don’t make a difference” argument). I mean since the analog signal from the Dac is transformed to digital and back to analog in Xilica (or other Dsp)?  
thanks, Ted

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Been playing with active crossovers for a few weeks, This morning I tested my right speaker, I always test left, quite a difference in frequency response! 
For kicks I decided to try to get the same REW response from each speaker.

So now I have different Xilica settings left and right, but very similar REW frequency curves coming from both.

Seems like the best sound I’ve ever heard from these speakers.
Ahh maybe just expectation/ confirmation bias!

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Has anyone used this (analog?) Signal processor to tri-amp? 

 

https://www.parts-express.com/Peavey-PV-35XO-Stereo-2-3-Way-Mono-4-5-Way-Crossover-248-8116?gclid=Cj0KCQjw9O6HBhCrARIsADx5qCSaYhzXqYFwaYEV8hFRAgEt-IUWMwuVHQRRzGKDT6PLlEta08TlivMaAo7OEALw_wcB

 

Im currently using an active dsp but it only supports splitting 2 channels, not 3. Plus it offers no delay options. My understanding is this unit, while not computer enabled, can split the signal into 3 frequencies, has volume matching for each, and allows for delay by each (though I cannot see how yet). And it’s price is cheap. Does that mean this is not good enough quality to use as a 3 way crossover for a klipschorns? 

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23 hours ago, VDS said:

Has anybody heard a difference by upgrading Dacs?

I've used a couple of different AVPs--which of course are mainly multichannel DACs with many available codecs and I/O options on the audio portion of the device. 

 

The difference that I heard was at the highest frequencies--the "air" and very high frequency clarity of the two.  However, if you didn't tell me which AVP I was listening to, I'd be hard pressed to hear any differences between the two.  (I don't have use of two-channel-only DACs.)  Of course, I pipe everything through downstream DSP crossovers on the output of the AVP, so in theory, I shouldn't hear much difference (if any) at all. But I did.. a very small amount, however.

 

4 hours ago, VDS said:

So now I have different Xilica settings left and right, but very similar REW frequency curves coming from both.  Seems like the best sound I’ve ever heard from these speakers.

I'd say that it's a bigger difference than one would initially guess.

 

1 hour ago, DVDMike said:

Im currently using an active dsp but it only supports splitting 2 channels, not 3. Plus it offers no delay options.

What are you using now (brand, model)? All DSP crossovers I've seen offer adjustable delay--that, and plenty of bi-quads (PEQ filters) per channel.

 

1 hour ago, DVDMike said:

My understanding is this unit, while not computer enabled, can split the signal into 3 frequencies, has volume matching for each, and allows for delay by each (though I cannot see how yet).

That appears to be an analog active--and it can't offer delay--only all-pass phase delay (less than 360 degrees of phase--which is a tiny amount of delay).  I don't recommend using analog active crossovers for horn-loaded loudspeakers (hybrid horn/direct radiator or fully horn loaded), since basically all multi-way/multi-horn loudspeakers need EQ and delay. 

 

This is really a DSP crossover FAQ.

 

1 hour ago, DVDMike said:

And it’s price is cheap. Does that mean this is not good enough quality to use as a 3 way crossover for a klipschorns? 

So you want the cheapest DSP crossover that you can find to drive Khorns?  Good luck...

 

I've identified useful DSP crossovers for high efficiency loudspeakers in this thread.  I recommend looking at that list and saving your pennies until you can afford one that's useful for your application.  I don't recommend cheap DSP crossovers: they will be nothing but headaches.

 

Chris

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1 hour ago, Chris A said:

That appears to be an analog active--and it can't offer delay--only all-pass phase delay (less than 360 degrees of phase--which is a tiny amount of delay).  I don't recommend using analog active crossovers for horn-loaded loudspeakers (hybrid horn/direct radiator or fully horn loaded), since basically all multi-way/multi-horn loudspeakers need EQ and delay. 


I can apply digital EQ at the preamp stage regardless of what type of signal processor is used or not used at all. This can only be done before the digital or analog signal processor splits by frequency.

 

Do the AK3 passive crossovers have a delay in them? If horns need them, I’d assume this must be part of the klipsch active crossover design.

 

1 hour ago, Chris A said:

What are you using now (brand, model)? All DSP crossovers I've seen offer adjustable delay--that, and plenty of bi-quads (PEQ filters) per channel.


I am using a miniDSP 2x4 HD. It offers 2 frequency separations per channel, parametric EQ per driver, a compressor per driver, and FIR filters per driver. I don’t understand FIR filters nor how to use them.
 

This unit is pretty inexpensive. For more money you can upgrade the firmware and get more software for room correction EQ and maybe more features. I can do room correction by speaker at the preamp, but not down to the driver level. 

 

I have about another 10 days to return this miniDSP unit if I don’t want to keep it. They also make a larger model that would work for tri-amping. 
 

sometimes inexpensive means low quality. Sometimes it does not.

1 hour ago, Chris A said:

 

I've identified useful DSP crossovers for high efficiency loudspeakers in this thread.  I recommend looking at that list and saving your pennies until you can afford one that's useful for your application.

just to be clear, previously in this thread have you identified the dsp crossover frequencies that should be used for a given speaker? Or have you listed actual processor units you recommend for consideration? I’d like to see both pieces of actually but it’ll be easier to find if I know what I’m looking for.

 

I don’t believe my current sound is worse than before I was using the inexpensive DSP. But I’m not convinced it’s better either. It could be that if my crossovers are out of spec, I’m limited to their degraded quality and I’m not going to see any improvement or be able to judge anything until the crossovers are fixed or eliminated from the chain entirely. I should be able to test my crossovers by Wednesday or Thursday. So I’ll know soon enough. 

 

my feeling about upgrading electronics is that sometimes it’s best to go in stages and not wait until you can afford the best. In many cases, I’ll never be able to afford the best but I don’t think that has to limit me from getting something “better”. If you are saying an analog signal processor is not ever going to hear any improvement (or it would be worse) by using an analog signal processor even if I can do speaker EQ in the preamp stage, that’s one thing. But if you are saying don’t bother doing this because you should wait until you can afford the best or near best, that’s something entirely different and is simply a personal opinion.

 

I appreciate your knowledge and insight even if i might disagree on items which are more subjective. So thank you for sharing. 

 

 

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12 hours ago, DVDMike said:

Do the AK3 passive crossovers have a delay in them? If horns need them, I’d assume this must be part of the klipsch active crossover design.

The passive crossovers have the equivalent of 180 degrees of delay in them (higher frequency leads lower frequency), which is not desirable delay: ~1.25 milliseconds at the woofer/midrange crossover (180 degrees at 400 Hz), and ~100 microseconds at the midrange/tweeter crossover (180 degrees at 4.9 kHz).  But that's what you get with passive crossovers:

 

AK-3 schematic 1.jpg

 

The real time alignment issues are mismatches that I quoted earlier/in another thread: 4.8 ms for the bass bin to midrange, and 6.5 ms from the bass bin to the tweeter--mostly due the different lengths of horns/drivers (i.e., an additional 0.7 ms from the midrange to tweeter--about 3.5 wavelengths).  That's where you need the DSP crossover to delay the higher frequency channels to time align them to the lower frequency channels (i.e., tri-amping using DSP).

 

12 hours ago, DVDMike said:

I am using a miniDSP 2x4 HD.

This unit has delays available.  I use one of these 2x4 HDs for my surround AMT-1/Belle bass bins.

 

12 hours ago, DVDMike said:

I can do room correction by speaker at the preamp, but not down to the driver level. 

If you use REW and a calibrated microphone, you can use the 2x4 HD to EQ out all SPL irregularities.  I don't use "room correction software" anymore--even Dirac has issues.  I use REW and the DSP crossovers, instead.

 

12 hours ago, DVDMike said:

...Just to be clear, previously in this thread have you identified the dsp crossover frequencies that should be used for a given speaker?

I linked two other threads at the first post of the thread that help you decide where to put the crossover frequencies from running raw (uncorrected) measurements and overlaying them on each other to see where they naturally cross.  This is the best method of setting crossover frequencies, I've found.  For a Khorn, those frequencies generally are 400 Hz and 4.9 kHz, but they can vary if you've got in-room acoustic measurements and a DSP crossover.  Generally, I recommend first or second order crossover filters. First order filters produce half the (undesirable) phase shifts as second order.

 

12 hours ago, DVDMike said:

...But I’m not convinced it’s better either...

Time aligning and EQing the loudspeaker flat using REW measurements really do sound better--even with Khorns.  The use of a DSP crossover and multi-amping also opens up the possibility of changing out horns and drivers--something that you really can't do using passive crossovers...unless you redesign the passives completely, which is a difficult task even for experienced loudspeaker engineers.

 

12 hours ago, DVDMike said:

They also make a larger model that would work for tri-amping. 

That's the miniDSP 4x10 HD that I referenced in the leading post of this thread.

 

12 hours ago, DVDMike said:

sometimes inexpensive means low quality. Sometimes it does not.

Yes.  In the case of certain miniDSP crossovers (the two mentioned here), the quality is good.  Xilicas are a little better, but that's also reflected in the price differential.

 

12 hours ago, DVDMike said:

But if you are saying don’t bother doing this because you should wait until you can afford the best or near best, better that’s something entirely different and is simply a personal opinion.

Personal opinion--with experience attached... 😉  But it's your money and time.

 

Chris

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  • 1 month later...

Ok, so I’ve read thru as much as I can digest…ok maybe not digest, just consume. So Chris I know that you do not mess with tubes, but I suspect you can say whether or not having a tube preamp feeding into a mini dsp is going to present issues. I’m using tube pre/monoblocks so there is quite a bit of gain, but I do have a nice class a ss amp I could use on the bass bin but that might not match well with the tube pre either. Just ordered the mini dsp, should be here this week. First experiment will be with bi-amping a pair of Belles. Anyone else using tubes on the front end? 
 

Thank,

Mark

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