Bonky
Rank: Trio
Posts: 156 
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Post by Bonky on Feb 23, 2018 16:44:43 GMT
Spica (of this parish) spiked (apologies) my interest in DIY builds - especially of omni-cubes - and in doing so have spent many 'happy' hours trawling the www.
However, I came across something unconventional; something to almost match the debates re mains cables, fuses etc that appear to fly in the face of common sense/science...that of crossover placement.
My LV speakers have the option of external x-overs (mine are inside), but if I were to build some DIY speakers I would certainly place them externally (if only so I could experiment with them). Now, I would have thought that the obvious place to put them was near to the rear of the speakers (well away from magnets and vacuum cleaners etc), but there seems to be a lot of opinion (sorry, lost the links), that the best placement is near to the amp (about 30cm). Potential reasons seemed to include: 1) further away from the magnets,2) better separation of bass and treble.
Has anyone done the experiment? Can anyone here give any explanation?
Yours, somewhat perplexed...
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Post by MikeMusic on Feb 23, 2018 17:10:02 GMT
I had outside crossovers in my Isobariks
Almost got around to isolating them somehow.
My guess is it will work well
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Deleted
Deleted Member
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Post by Deleted on Feb 23, 2018 17:51:06 GMT
My main speakers are a revised version of the Spica TC 50 (TC 50i SE X) and they have external crossovers. These are mounted to the rear of the cabinet, but I have toyed with the idea of lengthening the leads, siting them in nicer boxes and sitting then at the base of the speaker. I read on other forums that it doesn't impair the sound.  And if you are looking for inspiration, here is how it could look:  |
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Post by ant on Feb 23, 2018 18:16:21 GMT
I have external crossovers too for the speakers I built. the cabs have a 4 pole speakon socket on them as there are 2 drivers to supply, the crossover boxes are just some plastic maplins things with a captive lead about a foot long with the corresponding speakon plug on, and a set of speaker terminals to connect to the speaker cables.
Only reason for this is that I was tweaking the crossover component values and couldn't be arsed to keep going in back of the cabs. And it was easier to drill a hole in the cab for the socket than cut one out for a terminal tray.
Wether crossover components are microphonic, and wether it is better from an Sq point of view to have the crossover separate from the cab is debateable. not debateable by me, I couldn't care less, i did it simply because I am a bit idle by nature and it is easier to get at them if they are not inside a bloody great heavy object that needs shifting if you want to...
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Post by MartinT on Feb 23, 2018 18:41:03 GMT
One possible benefit (which I used many years ago when I externalised my R40 crossovers) is that you can use a short length of very high quality high current cable and longer lengths of lesser cable for the separate runs.
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Bonky
Rank: Trio
Posts: 156
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Post by Bonky on Feb 23, 2018 19:49:37 GMT
With respect to all the posters so far, (and I must apologise as it's obviously my fault in that I haven't made by question abundantly clear), my question is: why should so many people in the thread I read (and lost) believe that SQ is improved if external x-overs are positioned close to the amp rather than the speakers?
Has anyone switched their X-overs being nearer to the amp rather than the speakers? Also, (supplementary)... Do different cables before and after the X-over box make difference?
Thanks.R
PS. Spica- thanks for the above pics; very, very interesting!
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Post by MartinT on Feb 23, 2018 20:05:18 GMT
Ok, I understand your question, which I partly answered. It gives you the opportunity to run optimised cables for the bass and mid/treble runs, with a short high quality feed into them. It also keeps the crossover far away from the magnetics in the speakers.
It's a more idealised form of bi-wiring.
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Post by ant on Feb 23, 2018 20:13:39 GMT
A speaker cable has capacitance, inductance and resistance so will have an effect on the crossover points dictated by the crossover component values, the effect would be negligible as we are talking pf not uf, uH rather than h and tenths of ohms. It will however, have the same effect I would have thought wether the crossover box it at one end of it or the other, I.e close to the amp or close to the speakers. The same amount of cable is needed to get from one to the other.
I had the crossover close to the amp when i first did them as they werent boxed and needed to be out of the way, I had them about a foot away from the amp in the cupboard underneath it so they woupdbt get stood on or damaged. moving them from end to end when i boxed them up, I could hear absolutely no difference at all.
And as I was actually listening rather hard due to tweaking the crossover at the time, Im sure if there was a difference I would have picked up on it.
As always ymmv, but if you are going to box them, why not just try it at either end and see what you think.
Why do some folks think it makes a difference? Dunno, must make a difference to them. Didn't make a blind bit of difference to me
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Post by speedysteve on Feb 23, 2018 20:30:07 GMT
I have my crossovers before my amps  |
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Post by MartinT on Feb 23, 2018 20:45:44 GMT
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Bonky
Rank: Trio
Posts: 156
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Post by Bonky on Feb 23, 2018 20:54:42 GMT
...lifting and separating...? Playtex?
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Bonky
Rank: Trio
Posts: 156
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Post by Bonky on Feb 24, 2018 7:29:42 GMT
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Post by karatestu on Feb 24, 2018 8:09:09 GMT
I dont have a crossover at all these days, not even at line level  Just a cap on the tweeter of my 3 ways. When i did have a crossover i moved it to within 6 inches of the amplifier boards. The gains in clarity were big. Only gotcha is don't get the crossover inductors too close to a transformer or you will be greeted with hummmmmmmmmmmmmm Have a look at this thread on pFM HERE. Stu |
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Post by vantheman on Apr 2, 2018 10:49:50 GMT
I have external crossovers for my WD25TEx and acting on a side comment from Les Wolstenholme in a forum regarding another subject he happened to mention that years ago he had reached the conclusion that the sooner frequencies were separated, the better because everything was clearer and that crossovers were better nearer amps than speakers. I tried it which allowed me to use a single 4-core Van damme cable into a Neutrik speak-on on the back of each of my speakers which allowed me to forget nasty bananas. I definitely thought the sound improved at the time
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Post by MartinT on Apr 2, 2018 11:00:27 GMT
Hey van, welcome to TAS and glad you have posted. Better late than never!
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Post by ChrisB on Apr 3, 2018 22:29:30 GMT
That's interesting thanks. I remember being amazed at the pressure forces that can be generated inside a speaker and assumed this might have something to do with it. I was once trying to explain to a friend how a reflex port works and, to demonstrate, I held a small piece of paper in front of one while a speaker was playing at a reasonably high volume so that it flapped back and forth with the output of the port. After a few flips and flops, it was sucked out from between my fingers and into the bowels of the cabinet. That was quite funny and illustrative at the time, but a couple of weeks later, I happened to be looking at the speaker and 'phut', something flew out of the port. Of course it was the paper, but it had completely lost its structure, becoming just a very loose matted arrangement of fibres. |
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Post by Mr Whippy on Apr 4, 2018 0:46:33 GMT
Closer to the amp would mean a more efficient connection to the crossover.
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Post by karatestu on Apr 4, 2018 5:47:37 GMT
Did anyone read the link to pfm i gave earlier ?  Contains the comment from Les W. Many of us tried it (including me) and found a big improvement in clarity. The objectivists still argued that nothing had changed electrically and we were hearing things |
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Post by MartinT on Apr 4, 2018 6:08:00 GMT
Did anyone read the link to pfm i gave earlier ? Yes I did. Says it all about those who will try and listen to the results versus those who 'know' it cannot work. |
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Contains the comment from Les W. Many of us tried it (including me) and found a big improvement in clarity. The objectivists still argued that nothing had changed electrically and we were hearing things