External Crossovers...

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Hi

Re external crossovers:

a) the crossover should not be in a metal/shielded box? Would this cause interference with inductors/caps?

b) other than gaining the advantages of bi-wiring, are there any other advantages (like tweakability) to having external XOs?

c) for crossovers in general, does the orientation/spacing of components have any effect on the network?

Thanks in advance.

Mos
 
Mos Fetish said:
Hi

Re external crossovers:

a) the crossover should not be in a metal/shielded box? Would this cause interference with inductors/caps?

b) other than gaining the advantages of bi-wiring, are there any other advantages (like tweakability) to having external XOs?

c) for crossovers in general, does the orientation/spacing of components have any effect on the network?

Thanks in advance.

Mos

Hello Mos,

I cut & paste this from Lynn Olson's website regarding Ariel XO:


The best way to mount the crossover is to give it a box of its own. This isolates the capacitors from vibration (which they don't like) and lets you tweak in comfort while you listen. Just keep the crossover at least 12 inches away from any large iron or steel objects, which means don't put it next to your power amp or TV set.

Keep the tweeter and midbass filters electrically isolated with independent star grounds ... also, separate the inductors by at least 6 to 8 inches and place them at 90 degree angles to each other.
.....
Some folks are allergic to external crossovers; this is unfortunate, since capacitors are quite microphonic, acting both as electrostatic speakers and low-quality condensor microphones. You can't do much about the emission of sound (except consider oil-filled caps in metal cans), but you can isolate them from the heavy vibration of the enclosure by using an external (non-metallic) enclosure.


The reason why we should place 2 XO at 90 degree angles to each other because electric current & electromagnetic field influence each other with a factor of cosinus(angle). The influence of 2 XO will be minimum if you place them 90 deg to each other (cos 90 = 0). (question c).

Metal will affect inductor (question a).

As for the vibration affecting the caps, I'm not sure about it.

Cheers,
 
diyAudio Senior Member
Joined 2002
Re:Re: External Crossovers...

Hi,

As for the vibration affecting the caps, I'm not sure about it.

Some more than others but all are to some extent prone to vibration.
This being one of the reasons you want the box with the xover away from the LS cabinet in the first place.
So you better make the external box well isolated from air- and floorborne vibrations.

Cheers,;)
 
Hi,

Frank is quite right here, as I discovered myself accidentally, many years ago.

During the development of some X'overs which I had built on heavy pieces of plywood attached by an umbilical cord to the boxes (this was only done to enable easy modifications to be carried out, and not for any 'sonic' purposes) I found it best to make instantaneous comparisons, to ensure that any progress was going the desired way.
Accordingly, I would sit both speakers together side by side in the middle of the room, to reduce any unwanted room reflections, and merely make changes to one unit whilst constantly monitoring progress by making comparisons with the 'original' unmodified unit.

To ensure that the tweeters of these speakers were at ear level, the boxes were supported on some heavy tubular steel stands (sand filled) which were only about 9" high, and were of an 'open' construction, and to the touch, they felt relatively inert whilst music was playing.

After one weekend's 'tinkering', at the end of which time I was rather pleased with the several changes I had carried out, and had made the mods finally to both speakers, I moved the boxes back to their rightful positions.

Sitting down with the expectation of hearing some glorious sounds (also now in properly 'wide' stereo!) I was very disappointed with what I heard! :bawling:

I then spent several hours retracing my steps and reverting the changes one by one, but I still knew that I had heard better sounds from these speakers earlier on, no matter what I subsequently tried to do. The difference was not one of some minor change in the relative output levels from low to high frequencies, which I had been experimenting with, but it was throughout the audio spectrum and really spoiled what I was listening to.

By this time it was late in the day (and dark outside) so in order to have a closer look at the X'overs (in this reduced lighting) to ensure that I hadn't perhaps overlooked making a note of some earlier change I had made and therefore this might be the 'culprit', I moved the two X'overs from underneath the boxes, where for tidiness, they usually resided.

Immediately, there was a noticeable change in the overall sound, even though I had voided all of the interim 'improvements', and this was a real puzzle to me.

As the only change giving rise to this difference was moving the X'overs around (and they were now sitting on a deep pile carpet rather than on the metal tubes of the stand's bases), I switched one speaker off, and picked up the remaning 'working' X'over to move it around some more.

Well, to say that this was a revelation to me was almost an understatement, and although I had been experimenting with sonic changes due to component substitutions etc. for several years by that time, I was still very surprised at how much the sound could be influenced.

The cleanest and nicest sounds were produced when I was holding the X'over up off the floor, altogether, probably because of the least vibrational influence on it, and the worst, harsh and grainy sound, was with the X'overs back underneath the boxes, quite close to the bass driver's large magnet, and resting on the steel frames.

With further investigation, it became clear that (these) X'overs simply did not like any vibration (airborne or chassis borne), placing them anywhere near magnets was bad for the sound quality, as was the proximity of any steel/ferrous metals, and these unpleasant effects were not at all subtle! :goodbad:

Needless to say, since then I will never install a X'over within a speaker box, and I have learned a great deal more about the subject of adverse influences affecting components like capacitors and chokes etc. in audio gear.

So, please be warned (if you wish to realise the full potential of your speakers) and keep all X'over components etc. well away from the boxes, themselves, and any vibrational influences.:cool:

Regards,
 
Bob and Frank

Very interesting postings - I've learnt something.

I don't generally use passive crossovers in my designs but I'm sure that what the two of you have been saying about the effects of air-borne and mechanical vibrations apply throughout the hi-fi chain.

Many thanks, and thanks to sianturi too. I think that Mos has got more than he bargained for - good value at half the price.

Incidentally, I couldn't help but notice from this and other postings that Bob and Frank are both conscientious experimenters and listeners (so crucial !!!). Have either of you tried superballs as equipment supports yet? If not, try them. I think you'll be pleasantly surprised. They're cheap too.

Steve
 
7V said:
Bob and Frank

Very interesting postings - I've learnt something.

I don't generally use passive crossovers in my designs but I'm sure that what the two of you have been saying about the effects of air-borne and mechanical vibrations apply throughout the hi-fi chain.

Many thanks, and thanks to sianturi too. I think that Mos has got more than he bargained for - good value at half the price.

Incidentally, I couldn't help but notice from this and other postings that Bob and Frank are both conscientious experimenters and listeners (so crucial !!!). Have either of you tried superballs as equipment supports yet? If not, try them. I think you'll be pleasantly surprised. They're cheap too.

Steve

Hi Steve,

No I haven't (yet!) tried these things but I think they are these 'soft' supports which have gained some notoriety, aren't they?

I have had good experiences with some of Max Townshend's pneumatic supports, so if they work in a similar fashion I would *guess* they will be good.

Also, mrfeedback has done some work with spring supports which he 'raves' about, but whilst I always value his experiences (mostly they seem to coincide with my own, although we are on opposite sides of the world!) I do wonder about the 'undamped' situation with just springs which could be a bit uncontrolled.

Maybe he stuffs them with some foam or something similar, but I haven't asked him about this.

As you suggest, vibration in *all* electronic gear is a problem and will detract from the overall sound, so I go to great pains to damp everything possible. Also, any 'physical' feedback whether airborne or ground borne through the chassis is a bad thing, whatever the regular 'detractors' might have you believe.

Mostly, some very 'quick and dirty' tests will show this up in a half decent system, and this goes for digital as well as analogue, although I fully accept that this is not intuitive.

Having been experimenting for some 30 years with the sound of components and tweaks, and when I first started there were no proprietary tweaks to be had, anyway, I generally prefer to find my own ways and means of sonic improvements, rather than spending relatively large sums of money on someone else's (as yet unproven to me) devices.

However, I will always keep an open mind about any untried tweaks and many of them do have quite marked effects on the sound of equipment. Of course, whether any or all of them justify the high prices involved in purchasing ready made tweaks, is a matter for the individual to decide upon, but, as I believe it was you who said in another thread, one must always bear in mind that there are commercial needs such as development costs to be covered for in their selling price.

I realised a long while ago, that the mere costs of the component parts involved is not the way to assess any device or whatever, and although most of what I do, I do for enjoyment, it would be a different matter, altogether, if I had ever needed to make a good living out of audio development.

What has always been important to me is that most of the more significant findings I have come across over the years (just as with remote X'overs), is that the initial 'discovery' was entirely accidental, so there is absolutely no reason for me convince myself of the benefits (or otherwise) of any of these effects.

However, also nearly always, having found by chance something so important that it simply cannot be ignored, in most cases I have later managed to measure some differences, because I had then understood what was involved or have got my hands on some more sensitive measuring gear, and rarely do the measurements contradict what my ears have already told me! :nod:

An example I have related on the forum before was when (over 30 years ago) I accidentally discovered that all nominally similar capacitors simply do *not* sound the same, in spite of what I already then 'knew' and what conventional wisdom would have everyone believe.

As it was whilst attempting to cure some RF breakthrough in a moving coil head amp which JLH was developing and had sent to me for some 'listening' appraisals, naturally, I immediately advised John what I had discovered, and equally understandably, he told me I was barmy!

However, he never forgot that I also sent him a note of my sonic preferences which in descending order of 'goodness' was : polystyrene, polypropylene, polycarbonate, and lastly polyester. (these were about the only readily available film caps then).

JLH worked for British Cellophane (who made a large proportion of the plastic film used in the manufacture of caps), and consequently he had access to some relevant and very sophisticated test gear, and on measuring these caps, my choices coincided precisely with increasing levels of dielectric absorption (a term which I had not, at that stage, even heard of, but which much later became a kind of yardstick for judging a cap's sonic performance!)

So, if you see me, and others who have enjoyed similar experiences, getting aggravated by the continual attempts at putting these perceived effects down on the basis of some ridiculous psychological or imaginary (wishfull-thinking) errors on my (our) part, you might well understand why I (we) don't feel inclined to simply take it lying down!

Since joining the Forum at Xmas, I have been continually amazed and pleased to see that various different posters from all over the world *who have actually tried out some of these things, properly, for themselves* have by and large *all* come to very similar conclusions, which simply cannot be satisfactorily explained by coincidence or normal statistics.

Mistakes will sometimes be made by us, since that is the way of life, but if there is a concensus of opinion which arises, as it frequently does, then it is silly bigotry to ignore this, and continually challenge it to provide 'proof' or whatever, that we are not simply talking through the back of our necks.

Regards, :)
 
diyAudio Senior Member
Joined 2002
SUPERBALLS.

Hi,

Have either of you tried superballs as equipment supports yet?

No...I can imagine the effect to be somewhat similar to a Mission Isoplat.

I hear squash balls can be quite effective too.
Admittedly they are like to cost much more than the Superballs.

How do you keep them from rolling away with the gear?:bigeyes:

Cheers,;)
 
Re: SUPERBALLS.

fdegrove said:
I hear squash balls can be quite effective too.
Admittedly they are likely to cost much more than the Superballs.

How do you keep them from rolling away with the gear?:bigeyes:

'O' Rings is one method, suitably sized holes in wooden supports is another. Some folks like to cut their superballs in half :bawling:

Steve

PS: I'm experimenting with using 'Flubber' as an isolation material.:wiz:
 
Bobken said:

...An example I have related on the forum before was when (over 30 years ago) I accidentally discovered that all nominally similar capacitors simply do *not* sound the same, in spite of what I already then 'knew' and what conventional wisdom would have everyone believe.

As it was whilst attempting to cure some RF breakthrough in a moving coil head amp which JLH was developing and had sent to me for some 'listening' appraisals, naturally, I immediately advised John what I had discovered, and equally understandably, he told me I was barmy!

However, he never forgot that I also sent him a note of my sonic preferences which in descending order of 'goodness' was : polystyrene, polypropylene, polycarbonate, and lastly polyester. (these were about the only readily available film caps then).

JLH worked for British Cellophane (who made a large proportion of the plastic film used in the manufacture of caps), and consequently he had access to some relevant and very sophisticated test gear, and on measuring these caps, my choices coincided precisely with increasing levels of dielectric absorption (a term which I had not, at that stage, even heard of, but which much later became a kind of yardstick for judging a cap's sonic performance!)...

I recently bought a few polypropylene capacitors to block DC between the power amp and tweeters, and intend to complement this with an active crossover. But I haven't yet finished designing the active crossover, so I decided to put the caps to good use by substituting them in the place of cheap stacked polyester caps (in the existing passive XO network). I knew that polypropylene has far better dielectric absorption characteristics than polyester, but I wanted to see if there really were any significant sonic differences, and more importantly: whether I could hear any difference.

I had to change the high-pass section from a 3rd order design to a 2nd order design, because I had to work around the cap values that I had. I hoped that changing the HP from 3rd to 2nd order wouldn't be detrimental to sound quality and obscure any improvements. Furthermore, so far I've only implemented the change on one of my speakers - the one that is slightly worse sounding due to having a smaller amount of stuffing than the other speaker....

Nevertheless, the improvement was huge! I now think there must have been quite a bit of distortion before. These changes were definitely not due to a slightly different XO cutoff or slope characteristics, because I've made much bigger design changes before, and they haven't produced differences of this type.

I did a little bit of research and thinking on dielectric absorption, and it all makes sense. The energy storage ability of dielectrics like polyester is non-linear, and they can saturate and produce hysteresis effects. This produces harmonic and IM distortion, especially at the crossover point when the voltage across the capacitor is supposed to change polarity.

This stuffs up my plans slightly, because (as a diehard sceptic) I was fully intending to use moderately priced stacked polyester caps in my active XO, but now I've spoilt myself and have to use polypropylene ones instead. :bawling: I'm even entertaining the idea of using compensation circuits like the ones used by sample-hold circuits.

CM :bigeyes:
 
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