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June 18, 2018, 10:14:39 AM *
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Author Topic: """Crossover and Recap Changes in Snell Speakers"""  (Read 97 times)
grannilsson
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« on: May 23, 2018, 10:45:00 AM »

Hello ,

As i see many have questions about to change the crossover in Snell speakers, especially for them who will change bipolar/electrolytic capacitors that seem to belive that they are changing to some better, polypropylen for an example, with the same value and Think Everything is OK, that is totaly wrong in many aspects, dont stop Reading now, i will explain why soon.
 
But first my recomendation  if its not broken, dont do anything with your Snell speaker, or Contact "Atomic Hifi and TV" for the right replacement Components and drivers for your Snell speaker model.

Can i upgrade my Snell speaker ?

Well i don´t Think so, if you are thinking of doing it yourself, only the AIII could be ugraded to AIIIi, Contact "Atomic Hifi and TV" and see if its still avaible, Snell has Always endeavour to use the best and most appropriate components in there products, commensurate with current knowledge, so i believe they offer excellent value, which is destroyed when interfering with the speaker in my conviction.

Electrolytic Capacitor Changes

I usually find that people who alter crossover components are not fully satisfied with the results. They find that some aspects are improved, but others made worse. A classic case of this is when a polypropylene or other very low-loss type substitutes an electrolytic capacitor.
 
We all know that polypropylene capacitors can sound inherently better, but the change in internal losses changes the response of the filter, which is designed assuming the losses of the electrolytic component. What usually happens when the low loss component is fitted is that the corners of the roll-off are sharpened, giving a peak in the combined response that can make the sound unpleasant in various ways depending on the crossover frequency.
 
One way of getting round this is to wire a small resistor in series with the capacitor to approximate the original losses.

I say approximate because the loss factor is a frequency dependent resistance. The actual value you need depends on the original capacitor loss factor and its capacitance value.


The larger the value, the lower the resistance for a given loss factor. The formula for the equivalent resistance is:

R = d / 2ðfC

Where R = resistance in ohms, d = loss factor, f = frequency in Hz and C = capacitance in farads.

Series-equivalent circuit model of an electrolytic capacitor



Loss factor is usually expressed as a percentage at 1kHz. For a "low-loss" electrolytic such as the values between 1µF and 20µF found in tweeter circuits, d is of the order of 0.025 (loss factor of 2.5%). For values in the hundreds of microfarads it may be of the order of 0.07 or 7%. Typically therefore a good electrolytic capacitor of 5µF would have an equivalent series resistance of 0.8 Ohm. If the capacitor has a much larger resistor in series with it anyway, it's probably not worth altering.

The same argument applies if you substitute a cored inductor with an air core type. Always try to duplicate the DC resistance as well as the inductance. Sometimes inductors are deliberately wound with relatively fine wire to give a certain resistance to add damping to the circuit. Iron dust cores (sometimes called P-cores) have higher losses at higher frequencies than at lower, due to eddy current effects. Substitution of an air core, even of the same DC resistance, may give a steeper ultimate slope in the stop band that can alter the phase relationship between the two drivers. That can also mess up the overall response and skew the optimum listening angle a little.



As you can see, it's a potential minefield and difficult to get the optimum result without proper measuring facilities. Adjustment just by ear tends to give good results on limited programme material and you can usually come across some other piece that sounds less than acceptable.


The big advantage about Snell speakers was the crossover, even to funktion many years, Snell acoustics had established itself on the leading edge of technical accomplishment in the design of crossover networks essential to
the "optimum" distribution of the electric energy to the appropriate drivers so as to yield the desired sonic result.

The dividing networks used in all snell speakers is the most sophisticated and complex in the industry i ever have see(even compared with modern speakers made today).

All Snell speakers was individually adjusted by a snell Technician, while under dynamic operating conditions to the particular sonic characteristics of each of the associated drivers.
This process assures a totaly seamless transition from driver to driver and provides the correct frequency balance among the particular drivers, this was unique for Snell Acoustics to assure precise uniformity of sonic performance
in frequency response, accuracy, and imaging.
Play and enjoy   Smiley

Regards Göran


« Last Edit: June 05, 2018, 01:01:44 PM by grannilsson » Logged
trinhsman
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Posts: 142


« Reply #1 on: May 26, 2018, 02:03:52 AM »

I had very good results with a recap of my E II’s.  The tech that did it really didn’t want to re do the crossovers at first because they were Snells.  I bugged him for a while and he finally agreed.  He redid everything exactly to the originals, only with a more modern cap.  This included “bundling”the caps, like in the original.  He said it was done for a reason, and he would not change it.  They came out great.  Sound cleaned up and even my wife mentioned how much better they sounded.
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grannilsson
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Posts: 17


« Reply #2 on: May 29, 2018, 10:10:39 AM »

Hi trinhsman,
I have a completely different experience, maybe because I'm more skeptical of anyone who makes
changes to fully functional crossover filters, what was the problem with the filter/speaker?.
 
Replacing individual components requires more of those who do it than just relying on someone
who believes in knowing what's best, the chain is not stronger than its weakest link, and unfortunately
in these cases, a component like a single component that might have better value in one way alone,
being the one who recalls the entire sound balance of the speaker, which I tried to explain in the above article.

This can be seen quickly when measuring the speaker when replacing capacitors with a little lower internal
resistance than bipolar electrolytes, if you do that you have to compensate for this.
(read above again if you have missed what I wrote)

Keep in mind it is the final result that is the most important than any single component you belive on the paper is better,
it's all about to get as good  fusion as possible, and then you have to measure first and to make sure that there are no change in
the frequency curve as it usually happens with polypropylene capacitors that have lower internal resistance, (read about what I wrote earlier),
changes that are usually first experienced as clarity have nothing to do with believing that the speaker is improved with some magic ,
but it's exclusively to do with frequency curve changes that make the speaker play higher in a certain tone field, and you do not want that?,
I do not like it anyway.


Maybe you should have listened to the technician who advised you not to change components in your Snell EII, I agree with him.

What do you mean by a more "modern" capacitor, what exactly do you think it makes a difference?
there are no electrolytes in Snell EII in the signal path, only parallel down to ground, I have 2 pairs of Snell EII,
and  One pair JII, and all components measure perfectly, in fact all of my old Snell speakers, AIIIi , both my Snell EII, and my pair JII works perfectly
and i should never ever change anything in the crossover, and all sounds lovely. Wink

There is so much self suggestion when we want to believe there should be a difference when we change things
the subtle differences are all a product of our imagination, and OUR NEED TO JUSTIFY the effort and cost to import and
install premium caps over the standard ones.




Remenber capacitors that were made in the 80's and not exposed to heat works easily in 50-70 years, maybe much longer before
they are degraded considerably, components manufactured then were fully developed, so no idea of concern...


Best Regards Göran
« Last Edit: May 29, 2018, 02:04:28 PM by grannilsson » Logged
trinhsman
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Posts: 142


« Reply #3 on: May 31, 2018, 01:07:59 PM »

Göran
All I can tell you is my results.  The tech that did the work duplicated the crossovers exactly as the originals.  If you took a before picture and after picture there was no difference, with the exception of the color of the new caps.  The sound is spectacular.  I am lucky enough to live near a very high end audio store, and I can tell you that my recapped E II’s hang with speakers priced over 6,000 US dollars.  I understand your thoughts, but to me, the final result was a better sounding speaker that my wife and daughter, as well as myself said sounded better.
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grannilsson
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Posts: 17


« Reply #4 on: June 05, 2018, 10:28:40 AM »

trinhsman

To be 100% sure there is an improvement, one has to use scientific methods, otherwise it's only words.
And that means blind tests. Smiley

You say “If you took a before picture and after picture there was no difference” how do you know
In this particular case that there where no difference when you don´t have checked that ?, that´s why you have to do it blind.

It usually seems to be those who stubbornly claim big improvements with their Tweaks who are surprised when suddenly exposed to
not seeing what components they play on in there speaker crossover, It's a real eye opener  Wink



All new Snell speaker models  which was being implemented in the line, was tested under scientific methods (blind ones) to know if it was placebo or not,

and they listened to the speakers that stood behind the permeable fabric so nobody saw what model was being played,
That's what I call engineering, and that is Snell Acoustics landmark, and of course  because we both read and write here.

I will not have opinions on your experiences, it is yours.

If you can agree with me that that change can be a pitch change that is perceived as an improvement, but could be a measure of degradation?

But I think you can agree with me that if Peter Snell not had been  built his speakers with scientific methods, with very well  engineered skills,
they would not have been so talked about, and sought after as they have been for decades...


 




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