Those who believe that there is no difference in crossover components have one of two problems.  They have bad ears or bad source equipment.  Either case is detrimental to discerning improvements in sound quality.  But how good is good enough?  Certainly it doesn't make much sense to put a $32 capacitor behind a $25 tweeter.  Or does it?

A crossover component is easy to tweak, and users will yield more significant results from better crossover components than $80/ft speaker cable.  BTW, life is a game filled with marketing. I walked through SEARS today after dropping off my truck tires for the spring rotation.  There isn't much outside of the tool department that interests me in SEARS, but something caught my eye in the electronics department.  

There were a couple of young guys in their late teens/early twenties.  They were listening to the auto subwoofers.  Everyone has seen automotive woofers.  They have really cool looking painted plastic cones.  They look like "quality", but the sonic qualities lack somewhat (okay, maybe a little more than "somewhat").  Nonetheless, these guys were pushing the buttons and discussing which driver/amp sounded the best.  Certainly they all sounded terrible to me, but these guys were really into it.  They were doing some comparative listening.

The same thing is possible with crossover components.  I consider several clear levels of capacitors.  Among these levels is further stratification.

Capacitors

Level    Label                                                                                   Commercially used in:

1          Electrolytic/Mylar                                                                 Commercial speakers $600+

2          Bennic (made in China)                                                     B&W Nautilus $2k-$8k

3          Solen/Axon...                                                                       Tannoy Churchill $14k

4.        Jensen                                                                                  Aftermarket only

5         North Creek*/ SonicCap/Hovland/Auricap                       ??? North Creek/Homebrew upgrades/Norh

6         AudioCap Theta                                                                  Aftermarket only

*I am guessing at the NorthCreek stuff.  Their price tag, and description would seem to place them in this category.  I will do a listening test, but I'm not sure when it will happen.

I have personally experienced the AudioCap stuff, and found a very noticeable improvement with the PPMF (highly recommended for the $), and another (slightly smaller improvement) with the Theta.  The Solen/Axon/Bennec stuff have some individual nuances, but sound very similar.  I have never tried Jensen capacitors, but have heard they have a very smooth sound while losing some detail.  Following are further remarks about capacitors in no specific order.

One well respected gentlemen made the following comments, " But as for the caps...I will say this. The Bennic poly isn't worth the electricity it would take to grind them up in the garbage disposal. They really stink. I noticed more sound difference between the Bennics and Solens/Axons than I did between the axon/Solens and the Hovland/Thetas. Just my subjective opinion."  This gentlemen uses primarily upper end Adcom components.

I recently corresponded with two gentlemen who compared the Hovland to the Audio Cap PPMF.   One of them performed the comparison in a Norh 9.0.  The other performed the comparison in the output stage of his Tojeb CD player.  Both gentlemen preferred the Audio Cap PPMF over the Hovland.  I cannot explain this.  I don't know what "guts" are inside a capacitor, but the Metallized Propylene PPMF beat the film and foil Hovland.  Hence, their type of construction method isn't the only thing that makes a capacitor better or worse.

There is also something to be said for the Jensen capacitors.  Jensen has a very good reputation for making the very best paper in oil capacitors!  People are eager to embrace the warm sound these capacitors present.  Everyone seems to eagerly remark that the Jensen has a very tubey sound.  A few folks have reluctantly remarked that their substantial $ investment also resulted in loss of detail.  This would seem to follow with the warm sound everyone experiences.  I will not likely try these capacitors myself.  They are too expensive for their reputation.

When you purchase any kit, ask what kind of components are used.  "No Compromise" crossover components can mean many things.  It might mean good design.  It might mean good/better/outstanding component quality.  Most likely the components will be of the Bennec/Solen/Axon variety.  These are fine, but there is better stuff.  If you equipment is decent, and your ears are decent, you will notice an improvement directly proportional to the void in your wallet.  I highly recommend the AudioCap products from Jeff Glowacki at Sonic Craft.

There are only a few people who can speak intelligibly about the guts of a capacitor and explain them.  Jeff Glowacki is one of these people.  I have tested Jeff's voodoo magic and found that it really does hold water.  His components are very good.  His site, like mine, is void of hoopla about this or that.  His stuff is good, his words are true.  Jeff told me that he listened/tested everything and decided on Audio Cap because it is the best in its class.  I highly encourage anyone interested in getting a better capacitor to call Jeff Glowacki.  He can address any form of question concerning this issue.

I recently performed an a/b comparison with an AuriCap and Sonicap behind my OW1 tweeters. I learned why the AuriCap indeed has a very solid following.  It's a good capacitor.  It has a nice lush midrange, but lacks some detail compared to the Sonicap.  Overall, I found these two capacitors very good, and equal in quality.  If they were the same price, the implementation decision would be a toss-up.  However, the Sonicap is less expensive and the same quality - IMO.  I'll keep using the Sonicap.

There seems to be less hoopla about inductors.  Nonetheless, Dave Elledge has tested various "better" crossover components, including North Creek, Solen and Goertz  inductors and found the Goertz Foil Inductors superior, when tested against the others in comparable sizes.  I believe this sentiment will become more pervasively agreed upon by those experiencing these components in high-end systems. I use the Goertz inductors and found a slight increase in clarity along with some tightening of the bass.  The difference among the Solen and Goertz inducors is, however, very slight.  Either could be implemented with very positive results in the very best hifi systems.  I have a slight preference for Goertz, and they are slightly more expensive.

The components used are equal to the weakest link in your system.  If are listening to a $100 CD player through a $100 receiver don't expect the Audio Cap Theta to make a huge impact on your Cerwin Vega speakers.  Improvements might be heard, but they will be slight.

Over the past few years I have learned a few tangible snippets about capacitors.  These snippets encompass the makeup of a typical metallized poly film capacitor.  The makeup of a typical foil capacitor was quite surprising.

I will confine my comments to metallized poly film capacitors.  These capacitors exist in levels 3 and 5 of the chart above.  Such capacitors employ a layer of metal attached to a layer of foil.  These layers are wound in offset circles maintaining insulation between the layers of metal.  The offset layers are then sprayed on the end and a lead is attached to this spray.  The result is that each lead is attached to its own layer of film&foil, but will not touch the other layer of film&foil.  This other layer is attached to the other lead via end-spray.  While this all seems very simple, it isn't.  The methods vary widely.  The type of foil, consistency of the foil, type of metal, method of metal application, end spray, and lead attachment are serious factors determining the quality of a capacitor..

The method of applying the metal to the foil varies significantly among manufacturers.  The metal is sprayed, gassed or deposited onto the film.  Each method produced slightly different results with the same ultimate goal - even distribution of the material.  This can be quite difficult.

Getting down to the nitty-gritty requires a a very good microscope to evaluate the grain and crystallization pattern of the metallized material deposited on the film.  Significant trial and error in the manufacturing process will determine the very best method of application in the capacitor factory.

The metallized foil is typically wound in an offset dual layer concentric pattern.  The end spray is applied, and the lead is inserted into the end spray.  The entire system is sealed, often heat treated, and a capacitor is born.

My assertion is that all metallized poly capacitors are slightly different.  The difference are thus.

1.  Type of film.

2.  Thickness of film.

3.  Quality/consistency of the film.

4.  Type of metallized material.

5.  Application method of metallized material.

6.  Thickness of metallized material.

7.  Consistency of metallized material.

8.  Winding tension & consistency of winding tension.

9.  End spray chosen & termination method.

A keen eye will notice that I totally omitted the comments concerning capacitor lead material.  Given the @120'+ of film in the typical 4.7uf tweeter filter capacitor, the 4" capacitor lead will be very insignificant.  Sure, some kind of non-ferrous material is needed, but a fancy capacitor lead is primarily for the marketing department.  The quality of internal film and the metallized process is monumentally more important.