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Russ Andrews crossover design
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audiolabtower
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PostPosted: Fri Mar 08, 2013 12:21 am    Post subject: Russ Andrews crossover design Reply with quote

An extract verbatim from the Russ Andrews Loudspeaker Upgrade Handbook, after saying 2 way speakers should have their crossovers ripped out and replaced with a single capacitor:

Quote:
You can proceed with 3-way designs in the same way as with 2-way.Wire the bass driver (or drivers) direct to the input terminals to drive it full range.Select a test capacitor (say 5µF) to roll on the midrange and adjust the value up or down so that a good balance with the bass is achieved.Then select a lowish value (say 0.47µF) to roll on the treble and listen to the resulting balance.Adjust it up or down until a good balance is achieved.On a 3-way speaker the midrange phase should be the opposite of the bass and treble,so if the bass and treble positives are connected to the positive input terminal,then the midrange positive should come from the input negative (black) terminal.A typical 1970’s speaker,the Cambridge R40 using KEF B139, B110 and T27 tweeter needed 3.9µF for the mid and 1µF for the tweeter.Although,when measured,the treble was several dB’s down,the speaker sounded well balanced! I chose to stick with the best sound rather than the best measurement!
Unquote.


Kef must have wasted such a lot of engineering time over the years!
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AndyS
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PostPosted: Wed May 01, 2013 8:09 pm    Post subject: Reply with quote

Well would you credit it, That is what appears to have been done at speaker manufacturers like LNB, very basic Xovers with minimal components. Think I read that somewhere too!
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proffski
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PostPosted: Thu May 02, 2013 1:17 pm    Post subject: Reply with quote

That theory is heavily dependent on the design of the actual drive units, far too many important parameters for me to go into here... A case of a little knowledge being more dangerous than none. Experiment with due care!
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iso
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PostPosted: Wed May 15, 2013 11:56 am    Post subject: Crossover Reply with quote

Actually quite many classic speakers used quite simple crossovers. JBL L100 was 3 way design and used 1 cap in series to LE5 mid and 1 cap in series to LE25 tweeter.

AR used more sophisticated crossovers. I am doing AR-2ax refurbishment now. There are series caps for both tweeter and midrange. Series coil was also used for the woofer. There is also interesting feature in the AR midrange. Front cavity of the midrange is stuffed full of glassfibre... I suppose this was used to aid naturall roll of caracteristics of midrange driver.

Someone may ask how this will relate to Kef Speakers from 1970´s... but there is more than one way to make speakers. And not necessarily the right and wrong way.

Best Regards

Kimmo
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proffski
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PostPosted: Wed May 15, 2013 5:18 pm    Post subject: Re: Crossover Reply with quote

I still maintain that in order to use 1st order crossovers either suitable units bust be found off the shelf or designed and be fit for the purpose.

I have designed loudspeakers using 6dB octave with what was available, but was never entirely happy with the end results even though theory points otherwise. There are too many aspects for me to cover or quote so I shall point you in another direction in due course of my missive.

I have never been a fan of any early American loudspeakers except perhaps the brilliant AR3a. My only regard for JBL is that most go LOUD!
A good move if achieved via efficiency, otherwise far too coloured for my taste.

Anyway, I have meandered on for far too long; have a peek at the site via the link provided below. Start to take not of words of wisdom from the 2nd paragraph onwards.


Link:
http://www.stereophile.com/content/thiel-cs2-2-loudspeaker-first-order-filters
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audiolabtower
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PostPosted: Wed May 15, 2013 8:17 pm    Post subject: Reply with quote

Actually I posted the paragraph as a joke of a typical Russ Andrews approach for the ill informed. Keftopics Vol 4 No 2 had an interesting section on 1st order filters showing how a typical tweeter can never have a flat response through a 1st order due to its natural rolloff, let alone colouration issues of driver resonances and breakup ending up audible and unequalised.
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proffski
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PostPosted: Wed May 15, 2013 8:25 pm    Post subject: Reply with quote

That is the trouble with so many home tweakers.
They make a change and it sounds different, and human nature being what it is the assumption usually is that therefore it must be better!

Do you remember the craze a few years ago when all the self-appointed 'experts' went round advocating the removal of internal damping materials?
Sure the end result sounded different, but was it correct and were all those loudspeaker designers and engineers so utterly wrong?

I think not… Evil or Very Mad
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clubsport911
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PostPosted: Wed May 15, 2013 9:22 pm    Post subject: Reply with quote

Well, I'm doomed then... my 105/3's have about 50+ components ! I like the idea of "less is more" but I cannot argue with my ears. My speakers sound epic.. and I've heard a few.

Tempted... but not enough
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proffski
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PostPosted: Wed May 15, 2013 9:24 pm    Post subject: Reply with quote

Welcome back!

Many a wiser word said, "A little knowledge is better than none".

Enjoy! Smile
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RGBE
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PostPosted: Thu May 16, 2013 1:35 pm    Post subject: Reply with quote

There are many drive units that would be unacceptable without a sophisticated crossover correction, for instance, and forgive me, the KEF B110A SP1003. I find the sound of this speaker unbearable without its required crossover, the more drastic the better: like that on the LS3/5a.
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proffski
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PostPosted: Thu May 16, 2013 2:56 pm    Post subject: Reply with quote

I'm sure we all agree.
The B110s used in the LS35a design were rather special.
They were very carfuly chosen and the reject rate was high.
See Colins' posting on the matter if you can find it, an eye opener and he should have known!
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iso
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PostPosted: Fri May 17, 2013 8:38 pm    Post subject: Joke Reply with quote

I did understand that Audiolabtower made joke about Russ Andrews tweeks. I fully agree that if something sounds differently, it does not necessarily mean that it sounds better (or worse) and it is a bit silly to waste efforts that have been used to original crossover design. I was only pointing out that simple solutions are not necessarily bad solutions. This all depends how well all other issues have been configured.

JBL produced something like 250 000 pc L100 and AR more than 300 000 pc 2ax models. 2ax was introduced in 1964 and had it roots in 2a of 1959. L100 was direct descendent of 4310 from 60´s. These figures are quite impressive for models which can not be considered exactly budget ones. 50 million fans do not make somethig good or bad, but maybe it is fair to compare these to other 60´s to early 70´s speakers.

Best Regards

Kimmo
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proffski
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PostPosted: Fri May 17, 2013 9:48 pm    Post subject: Re: Joke Reply with quote

Ok, they sold a hell of a lot of coloured loudspeakers, they were there to make money as were all the rest. Still not my cup of tea and I did own many AR, Boston and ashamedly briefly some Bose boxes but the less said about those the better. Each to their own, or as I prognosticate.

Everybody is more than welcome to their opinion no matter how misguided or misinformed it may be! Wink
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audiolabtower
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PostPosted: Sat May 18, 2013 10:48 am    Post subject: Reply with quote

They were also before BBC type speakers became famous and available. They were game changers in showing moving coil boxes could approach electrostatic realism, and could arguably be said to have influenced much that came after.
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iso
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PostPosted: Sat May 18, 2013 5:34 pm    Post subject: before BBC type speakers became famous and available... Reply with quote

Audiolabtower´s remark, how things do go on, is valid.

Colouration is also interesting topic. One might find Spendors SP100 as the latest development of BBC influenced design, even SP100 does not use traditional Finnish birch plywood construction. As wonderfull and how uncoloured I do find them... they do sound shomehow shy... lack of dynamic contrast one might say. ATC 100 style speakers do have considerbly more grunt, snare drum seems to have considerebly less dynamic compression. I do find this dynamic compression also one form of colouration.

My experice is so limited that I do not know if this shynes or lack of drama is due to the BBC style design? But I do not think that it is only because they are so uncloured speakers.

Best Regards

Kimmo
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