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Big is Good

x-over question

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A question I've pondered over for some time, we go to all this trouble of system isolation, when the cross over containing electrolytic capacitors is in the cabinet with a driver continually ponding it.

Is this a bad thing?

Should the purist use an external x-over to over come invasion of these vibrations?

or am I just being totally pedantic :confused:

 

What are your thoughts?

Has anyone done this?

 

To move them or not ... they could look very nice in a clear case :D

 

Cheers

BIG

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Some high end speakers do indeed have external crossovers, like the Living Voice OBX-RW and the Wilson Duette, so there is merit in taking them out of the cabinet i would suspect. I just couldn't be arsed having more boxes lying around the place though...

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A lot of High End are built into the plinths as well.

That saves a set of binding posts and wiring and has to be a better location than inside.

 

Rip them out, wire them up and tell us if it makes a difference. :)

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BIG,

Very good point...

 

2 issues:

- Physical vibration

- (Electro) Magnetic fields

 

And possibly even a 3rd factor:

- the 'back-EMF' of the driver/s' electrical proximity to xover & other drivers.

 

If you've ever experienced the effect of pulling a Xover out of a spkr cabinet, you'll appreciate the improvements to be had here.

 

I'd keep the xover away from the woofer magnet esp & at least in a separate compartment form the woofer/mid cabinet air-space.

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there was a link posted some years ago in this forum to the sonus faber factory tour.It showed their method of complely encasing the xovers in a resin "tomb" within the speaker ,so if a classy outfit like them think there may vibrations etc acting on the compoents then there could be something in it.Im with Neil on this one tho ,cant be arsed with the extra box.

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steven bilbee;70785 wrote:
there was a link posted some years ago in this forum to the sonus faber factory tour.It showed their method of complely encasing the xovers in a resin "tomb" within the speaker ,so if a classy outfit like them think there may vibrations etc acting on the compoents then there could be something in it.Im with Neil on this one tho ,cant be arsed with the extra box.

 

Here's the sonus faber link

 

http://www.hifi-notes.com/sonusfaberamatifabrikage-nl.htm

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Hi Owen,

1) stray magnetic fields from driver magnet assemblies can affect the 'value' of inductors close by. If not taken into account by the speaker designer, and usually isn't, the result can be a change in the all-important crossover frequencies and also result in possible 'slope' irregularities.

 

2) 'back EMF' is quite different. It is a voltage (electro-motive force) applied back to an amplifier from a speaker driver through the speaker cables. It happens consistently with all moving coil speakers and is caused by the coil moving in and out of the fixed magnet assembly. I believe that is why an amplifier with a high damping factor can assist in contolling driver movement.

Hope this helps abit.

 

Chris

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Thanks, Chris.

 

I've only dabbled in this area. I've wondered whether the sometimes perceived benefits of Biwiring can be attributed at least partly to back-EMF issues...ie. better isolating the woofer coil motor from the tweeter with the longer wiring & split network... ie. nothing magic to do with the amplifier output.

 

Also, as you mention, amplifiers with higher 'damping factor' (lower output imped) maintain their output better when faced with varying load of the driver motor arising from uncontrolled driver movements/resonances?

 

How far do you think that inductor coils need to be away from driver magnets, in an ideal world?

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Re biwire configuration. I've always considered that back EMF can affect the transfer of the audio signal from the amplifier to a speaker. Infact it must, to a questionable extent. I'm not an electronics expert so won't comment further on that aspect. But, given that the amplifier is sending a signal to the (bass) driver, this same driver is always going to physically lag behind the demands of the amp to move that driver forward or back from its passive state. So, the amp is always fighting negative or positive reactions from the coil/magnet 'motor'. This causes some complex interactions and determined by 'motor' forces and other factors more related to the driver parameters and associated amplifier in use.

BUT, having said that, my personal belief is (taking a simple 2-way system as an example) that having separate cables to the bass and treble crossover sections cannot have a negative affect. Simply, leaving the bass driver and its cable to "argue" the EMF issue, and having a separate cable feeding the treble without this EMF issue and no doubt a cleaner track is the way to go. Two ways to the Bombay Hills, one for trucks and one for bicycles.

 

This issue will always be open to debate as forum history shows, but either configuration can't avoid the need for good quality speaker cable. I have my own thoughts about that too.

Distance of coils to drivers is another debate and relates more to the amount of stray field from bass drivers and the inductor values used in the crossover. Really there are no hard and fast rules but further away from the magnet is always better. Personally I don't believe that external mounting in a reasonably large cabinet where it's possible to keep inductors away from bass drivers anyway is a benefit to the final sound. There are more connections and more wire. Often, you'll also see external crossovers mounted close to mono block amps.This is an even worse position for the crossovers, where the large amp transformers stray field can have a major affect on inductor values.Anyway, enough waffle from me!

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chris;71239 wrote:
Two ways to the Bombay Hills, one for trucks and one for bicycles.

 

Ha ha, as a bicycle rider, I will remember that particular analogy :D

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