The sonic benefits of an external crossover. A discussion.

treitz3

Super Moderator
#1
Hello, ladies and gentlemen of the forum and thank you in advance for your interest and input in the following discussion. This thread will be part of an ongoing series that will concentrate on the "Dissecting a speaker Series". This discussion will be concentrating solely on the sonic benefits of an external crossover and the end result as to what hits your ears.

Some companies offer an external crossover for their speakers and usually the price tag associated with these type of speakers are pretty hefty. Some of you may have heard throughout your audio journey that going external with the crossover is the "way to go" but have never really learned of the sonic reason as to why. Only theory behind why one would do such a thing. Things that could be considered an attribute are as follows;

* Ease of swapping individual components within said speaker/customizing/tailoring to suit one's preferences.
* With loss of vibrations, the values of the individual components retain a better consistency of proper operating performance.
* The ability to isolate said components just as one would with the rest of the gear.

What say you?

Tom
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 23, 2010
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#2
In no specific order:

  • Direct coupling of amps to drivers, providing better control and lower distortion (higher damping factor)
  • No loss through passive crossover components
  • Much more flexibility in designing and optimizing line-level crossovers to reduce interaction among drivers
  • With DSP-based crossovers, no component drift, nearly ideal filters, easy to independently adjust different slopes, gains, phases for each driver; could include room correction as well
  • Allows choice (optimization) of amplifiers to suit drivers and frequency range
etc.
 
Feb 11, 2012
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Hangzhou, China
#3
I prefer to have the passive XO right next to the amp so then the cable carrying the full bandwidth audio signal is as short as possible. This allows cables optimized for their respective bands to be used between the XO and the drive units. I use Cat5/Cat6 twisted pairs, paralleled for bass/mid according to current demands. A single pair I use for the tweeter and I reduced the tweeter pad resistor in my XO to compensate for the series resistance.
 
Jul 1, 2010
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#4
This is still a passive crossover in the signal chain after the amplifier, it is just housed outside of the speaker box? It's advantage, then, is that it gives the speaker manufacturer something dubious to differentiate his product from the competition.

Tim
 
#5
In no specific order:

  • Direct coupling of amps to drivers, providing better control and lower distortion (higher damping factor)
  • No loss through passive crossover components
  • Much more flexibility in designing and optimizing line-level crossovers to reduce interaction among drivers
  • With DSP-based crossovers, no component drift, nearly ideal filters, easy to independently adjust different slopes, gains, phases for each driver; could include room correction as well
  • Allows choice (optimization) of amplifiers to suit drivers and frequency range
etc.
I agree with everything Don says. However, I think that Ron is referring to an external, passive, speaker level crossover (PHLXO). In this case, I think the only benefit is the ease in which it can be swapped for an active crossover :)
 

A.wayne

New Member
Jan 15, 2011
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#6
In a nutshell ......... MICRO-PHONICS .....!!!

Then there are another dubious effects :) audible to golden ears ones , in short you want caps as close to the driver as possible , inductors away from vibration and stray magnetic field, Shielded drivers are your best friend for the latter , distance from the driver for the former .

Next is size :

Big inductors need room to not have any proximity effect , i have measured this in the past to be a min of 3 inches when at right angles , double that when parallel to each other, with big inductors this means room , easiest to remote mount the xover than it is to make room, especially if the enclosure volume is tight and does not permit.

Best then to remote....

So you want Mid/tweeter caps and components as close as possible , bass drivers and their inductors away from vibration , best compromise would be to remote, bass driver components.

Install the rest as close to the drivers as possible .....
 

A.wayne

New Member
Jan 15, 2011
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#7
I prefer to have the passive XO right next to the amp so then the cable carrying the full bandwidth audio signal is as short as possible. This allows cables optimized for their respective bands to be used between the XO and the drive units. I use Cat5/Cat6 twisted pairs, paralleled for bass/mid according to current demands. A single pair I use for the tweeter and I reduced the tweeter pad resistor in my XO to compensate for the series resistance.
My preference is the opposite , and have wires to drivers as short as possible , the added inductance between xover and driver will smear the mid/top end ..

Let the voltage source do the work ....:)
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 23, 2010
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#8
I agree with everything Don says. However, I think that Ron is referring to an external, passive, speaker level crossover (PHLXO). In this case, I think the only benefit is the ease in which it can be swapped for an active crossover :)
Ooops, my bad, yes I was thinking of an active line-level crossover, not an external passive speaker-level crossover (like my Magnepans have, as a matter of fact). In that case, A. Wayne summed it up pretty well.

Sorry for the OT diversion, getting senile - Don
 

treitz3

Super Moderator
#9
That's alright, Don. We are all, after all, human. Your answer will be good for the next in the series of dissecting a speaker. ;)

Tom
 

Face

New Member
Dec 13, 2011
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#10
Use high end components such as Claritycap ESA, MR, or Duelund CAST components and microphonics from the speaker cabinet are no longer an issue.

Otherwise, I also prefer external.
 

treitz3

Super Moderator
#11
Hello, Face and thanks for chiming in. Good to see you here! I do have a question with regards to those components that you have listed. Are any of them susceptible to the following?

When components are placed into equipment, which is consequently stressed by vibrations. Capacitors, which are sensitive to the stress, transform vibrations into an electrical signal. The signal could appear on the component as an additional spurious noise and thus it can interfere together with original signal and degrade it. The degradation of the signal usually leads to undesirable deformation of electrical features of the component and consequently bad functionality of the complete equipotent.
If I'm correct in interpreting this, the aforementioned is called piezoelectric noise from capacitor vibration.

Of all of the speakers I have personally heard, some of the fondest sonic memories I have experienced have been from speakers that had external crossovers. I have heard from both sides of the fence. Some say it's a waste of time/effort and yields no betterment of the end result. Then there are folks from the other side of the fence that swear by the crossovers being external. While listening to a speaker set that has an external crossover....I can't quite put my finger on the sonic difference and the difference [sonically] is very small but to these ears, audible. The best way I could describe what I hear is simply a very clean and precise end result that seemed to have allowed for squeezing that last 1% out of the system's performance.

Face, you mentioned that if someone goes with high end components such as Claritycap ESA, MR, or Duelund CAST components that microphonics from the speaker cabinet are no longer an issue. Yet, it seems you still prefer to have your crossovers external. Could you be so kind as to try and describe the sonic difference between what you hear between an internal verses an external crossover? I know my attempt at describing the differences wasn't the most detailed but as I mentioned. It's hard to put my finger on it. If nothing else, could I ask you why you still prefer an external crossover when the microphonics would no longer be an issue when utilizing your previously listed high end components?

Tom
 

flez007

Member Sponsor
Aug 31, 2010
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#12
In my case the Ascents have an external xover but it is a passive implementation, besides the microphonics/vibrations issues listed earlier I can't tell of any other benefit.
 

treitz3

Super Moderator
#13
While doing some research today, I ran across this statement. Don't know about the validity of this but it did make some sense to me, given the right conditions.

Voice-coils and some of the resistors used in the x-overs can generate some heat when played at high volumes. Since temperature increase of the voice-coil affects the driver's response, it could be useful to have the x-over not sealed in the enclosure... If you play it loud for extended periods.
Tom
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 23, 2010
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#14
Inductors are also sensitive to vibration, more so than caps if either air-coil and/or not well-made (sealed to minimize vibration-induced inductance changes as the coils move ins reponse to the sound).

I was going to mention heat generated both in the box by the drivers (esp. in a sealed speaker) and by the crossover components themselves (losses in the components) but wasn't sure it mattered, or would be different in an external box. A small crossover box would get the components away from the drivers but self-heating could arguably be worse. Not that I've ever heard of that being a problem, but now I am thinking I could market an external crossover with heat sink fins on top and make a fortune... :)
 
#16
Since I've been all over this one with my Monoliths (which had a factory choice or external passive or external active XO):

When I first bought my Monolith III's they came with an external crossover box. Fairly sizable and heavy. Here's a pic:

ML Monolith Xover 004_sml.jpg

An advantage for the external Passive not yet mentioned is the ease of converting it from Single amp to bi-Amp setup. The Monolith passive had a heavy duty switch in it that completely separated the hi-pass and low-pass sections for bi-amping duties.

While bi-amping helps, it paled in contrast to bi-amping and going Active XO. But that's for another thread.
 
#18
^^^ Actually that benefit (ease of conversion to bi-amping) was mentioned in an earlier post...
Hi Don, Yes, you did, but in the context of an active, which BTW- I'm totally in favor of as well.

For passives, being able to easily split the XO in two and do bi-amping was a potential benefit of being external. Not that it's hard to do in a built-in either.

To me, the biggest benefit of external passive x-over is it makes it easy to upgrade to an active XO without having to hack into the speaker itself.
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 23, 2010
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Monument, CO
#19
No, my first post was totally out of line, I had a brain fart and missed this thread was about external passive speaker crossovers, not line-level. Keith_W gets credit, in post #5, for not only bringing me to the light but also noting the ease of switching to an active crossover when the speaker's passive crossover is external.

With your last statement I think we all agree.

Aside: My Maggies have an external crossover, but still have an internal crossover as well for the midrange panel to tweeter ribbon. So, an external box is not always a complete panacea. I did bi-amp my Magnepans, with a line-level crossover (active or passive at various times), for most of their life. Never tri-amped them.
 

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
#20
If it's for DIY, an external crossover makes a lot of sense - easy to modify, easy to split and bi-amp, etc.

Most of the other benefits have been mentioned - save one. Some crossover components can be very large, and in a small cabinet be a significant proportion of the internal volume and hence make a difference in the design of the crossover. If the speaker designer did not take this into account (he'd probably have done the design and tweaking of the speaker with the crossover external), then moving the XOV outside the cabinet might improve the bass response.
 

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