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I am having my L112 networks rebuilt by a local tech who is also doing my woofer surrounds and replacing the twist terminals with 5-ways. He says he will use Solens caps in the network, and that these caps are so high quality he won't need bypass caps at all. He intends to remove them from the design. I don't know enough to decide if this is a good or bad idea... Does anyone here have an opinion?
thanks
Chris L
Austin, Texas
I just built a set of crossovers and I used all Solen caps but still used the Theta 0.01 mfds for by-pass. As good as the quality of the Solens, I would HOPE that the Theta's would be that much better for the additional $$$. I figured, couldn't hurt (except the wallet;) ).
In my experience, using high-quality capacitors of the appropriate values obviates the necessity for bypass capacitors. I would conclude that your technician is correct.
I guess I have to add that you can bypass high-quality capacitors with super high-quality capacitors if you really want to do so for that last little bit of whatever it is you get for doing so and can afford it.
Bypassing and biasing
You will find some of the knowledgeable crossover people still bypass Solens.
You will really have to listen to the two before you can say " Now That is the One"
I've done some research here on the site and thought this thread was the most illuminating:
http://www.audioheritage.org/vbullet...read.php?t=248
But in the end there seem to be a lot of contradictory opinions. I am leaning toward getting the guy to use the bypass whether or not it's his first choice, since I like having my high frequencies nice and all there... just not too much, if you know what I mean... And I don't like the idea of deviating from the original design. Too bad there is no definitive answer. I'd love to hear more of y'all experts chime in though.
Chris
It never ceases to amaze me that some of you guys who have spent many years around some of the loudest-playing and most powerful speakers the world has ever seen can still hear the difference made by a .01 mfd bypass cap. Several years of sound work in the '70's and '80's may have reduced my hearing capability in the higher ranges but not my appreciation for good sound. You're right, of course--if you can hear the difference, then it's worth it, because that's what it's all about.
It was standard practice for JBL to use Bypassing as they built the later crossovers.Quote:
Originally Posted by cplyons
There is enough crossover threads in this forum to choke Godzillia and his buddys.
Another thing you can do is get the book "Loudspeaker Cookbook" by Vance Dickerson.
It has a good section on crossovers
Crossover design is definitely an art. and some of the things people do with them is amazing;)
Just to clear this up from a technical restoration prespective:Quote:
Originally Posted by whizzer
JBL did bypass their crossover networks for a reason. They used mylar capacitors on a number of networks as the main (prime) capacitors. By definition if your refer Giskards comments in the above link mylar capacitors benefit from bypassing of one or more varieties in this context.
In this instance its does make and audible difference.
On the other hand (as also discussed by Giskard) if you can afford to spend $1000's on hi end Golden Ear capacitors on a whole passive network you might try also bypassing. The point being why would you do this when A/ It may not be practical, B/ The money would be better spent doing it a better way..active and use super hi quality parts there.
It could also be argued as Audience claim with the Auricap, bypassing is not desirable with very hi quality capacitors. Pity I never tested their claim before building and shipping a network for Porcheman but in theory it makes some sense.
Capacitors are storage devices of an electrical charge that charges and discharges in a circuit.
How effciently and effectively they do this in an a/c audio application as an element in a crossover network depends on the materials of the dieletric and manner of construction. Problems arise for capacitors in that they can have a memory of the previous charge and that they can smear the charge and discharge (D/A ). They also have that is termed an ESR or basically internal resistance to passing the current which can vary with frequency and lead to a loss of fine detail.
If we reflect back to Giskards comments in the link to the other thread this all makes some sense and the effects of bypassing with dissimilar types of capacitors are complementry when performed in the manner prescribed.
"But", if you already have what might be an ideal capacitor, then bypassing it with another value or type may in fact upset its characteristics. Because the characterstics of the bypass capacitors are very similar but not same, the effect of the bypass capacitor may be to blurr the already ideal transfer function of the prime capacitor and be less than complementary. No two capacitors are exactly alike in this context so if one accepts the prime capacitor is doing everthing correctly then adding a second or even a third capacitor as a bypass element may result in the effect of a 2nd or 3rd signal super impossed on the main signal. This would not be desirable.
Whereas in bypassing what are clearly dissimilar types and values of capacitors with the prime capacitor of lower order of quality we are replacing something that is known to be missing and the result is an improvement.
The above is by no means a full or complete discussion on the topic but highlights in laymans terms what and why capacitors and can play funny buggers with the audio signal. Getting it right in practise in another matter.
But be assured JBL did what they did the way they did for good reason.
What I net out of all this is the following. Please bear with this newbie a little longer and let me know if I have missed the point:
1. Theoretical opinion supports bypassing the use of bypass capacitors if the main capacitor is of "high enough" quality. There is no way to be sure of which crossover design actually sounds better without listening to an A/B of with/without bypass. You just have to listen and decide what you like in your speaker, your room, with your crossover components.
2. Also, there is no way of knowing without trying it out what the interaction between a given capacitor and its bypass will be. Although, if the capacitor is not of very very high quality the odds improve that there will be sonic benefit to adding a bypass capacitor to the main capacitor.
3. JBL apparently thinks enough of bypass-enhanced design to continue doing it in their Pro line. In other words, even after the general quality of audio-purposed capacitors increased dramatically they continued to see the value of adding bypass capacitors to their networks.
Given the above, I'm gonna ask my guy to add the bypass caps back into the mix for my rebuilt L112's. I'll let you know how it turns out.
Chris
Solens are great caps, I don't think you need to worry about bypassing them. Spend the money on better inductors although you should keep the DC resistance of the coils close to JBL specs unless you can add a small resistor to compensate.
Air Coil chokes are better for high power operation as they don't saturate easily if at all. But they have higher resistances because they use more wire. So to get the same result air coils up the gauge of the wire ( and the price) so the DC rsistance is in line with comparable iron cores.
Sorry if it is a bit off topic but buying good capacitors is fairly easy and not terribly more expensive than cheap electrolytics but coils are more difficult.
If there was a point I forgotten what it was.
When you have a vintage JBL speaker review the techincial aspects of the crossover and determine if it is bypassed. Then proceed from there.
If you are determined to use the most expensive/best capacitors on the planet..follow the suppliers instructions.
Quote:
Originally Posted by cplyons
Biased Solens.Quote:
Originally Posted by cplyons
The L112 is "good enough" that I would put the money into biased networks. The Solen perfect lay coils are decent enough too.
Like other recent TOTL JBL's, the absolute latest JBL system, which hasn't been formally released yet, uses a biased Solen network. ;)