Forte I Crossover Upgrade

[SET12]

New people should learn to use the search function, it would save us old people from having to repeat ourselves.

Metallized film types take 10-20 hours to settle down. You can read why at Bob Stout's page at the LDSG site.

"Bob's Autoformers" are made my Universal Transformer -- these are the same people who made them for Klipsch. The only major difference is that the new units are bifilar wound. An autoformer is just a tapped inductor -- a long piece of magnet wire wrapped around a core. The units from Germany are basically the same thing. I don't see how there could be much of any difference in sound since they appear to be built just like the units from UT. There might be a subtle difference, but I sure don't see how it could be of the magnitude described. What might make a real difference is removing the core -- an air core autoformer would be cool, but most probably wouldn't make the investment if they were available.

SET12, I think you've posted those pictures over a hundred times and I've never made comment, mostly because I can't think of a way to offer criticism without sounding mean-spirited. I'm not much impressed with the build: the coil for the tweeter circuit is the wrong value, and you're placement of the coil is about in the worst place possible. Also, none of your connections are gasless (neither properly crimped or soldered).

I think if ALK can get away with this

Without coupling I can't see an issue with what I have its nearly 90 degrees.

As to the Autotransformers, they are worlds apart in sound presentation and hardly a subtle difference from one another and not just in my opinion. I do have listeners here with vast music listening experience as well as experience with gear.

As far as my connections I consider the terminal blocks as good as any crimp IMO. And there is far more to be concerned with in a crossover IMO anyway.

With the inductors I simply used the stock values as provided by Klipsch the tweeter inductor was stamped .16mh, the DCRs are the only difference. I basically liked the stock speaker and worked with the stock network. I am fully aware of ALK's work and understand the stock networks electrical short comings with phase and impeadance all over the place. But even still subjectively the speaker was involving and today it is vastly another experience that competes with Kilpsch's costing thousands more IMO. They work for me and I have owned some pretty high end stuff through the yrs, yet nothing has given me the level of satisfaction of my modified Fortes.

IMO caps very greatly in their time to settle which in my experience can vary from tens of hrs to several hundred hrs and I agree with these people http://www.laventure.net/tourist/caps.htm

I have had many people here that were impressed with what they heard
some even very shocked so much so they did not even want to listen to
the stock Forte's at all after an AB.

Lastly it doesn't matter whether your impressed or not the proof is in the listening

SET12

[Al Klappenberger]

For the life of me, I can't understand why people waste money putting good parts on a rudimentary design!

http://forums.klipsch.com/forums/t/120300.aspx

AL K.

[4tay]

For the life of me, I can't understand why people waste money putting good parts on a rudimentary design!

http://forums.klipsch.com/forums/t/120300.aspx

AL K.

The better parts work, but indeed---I dig your external crossover option, and eliminating all the binding posts/clips/extra attachment hardware. I am considering your plan for my upcoming HII upgrade. Space, and sheilding between parts!

Exotic all-metal caps that take mega-hours to burn in are not likely to be installed in most speakers. They run $200-$300 or more, each. Even with that, there is no guaruntee said caps will improve the sound. Seems that the laventure site does not care for solen or some auricaps very much. There is a blend of objective and subjective there as well.

[Fjd]

DeanG:

“What might make a real difference is removing the core -- an air core autoformer would be cool, but most probably wouldn't make the investment if they were available.”

Dean has a fascinating idea with an air core transformer (since a transformer is just a couple of inductors that share a common magnetic path) even though the market probably doesn’t exist to make it profitable. Just like an inductor, the transformer core is subject to the phenomenon called hysteresis and, although the hysteresis loss is typically small, an air core transformer could eliminate this.

Without more description from the builder, the build quality is difficult to assess in comparison to the model made by Universal Transformer. For example, a larger gauge of copper wire may help heat dissipation due to winding resistance, but from pictures it is difficult to determine just how much more copper may be packed into that space as opposed to the Universal model. Also, if the builder uses bifilar winding technique as the Universal uses per Dean, which bifilar winding will produce much more energy over a single wound coil.

What core material is used and are there any advantages/disadvantages to this core material if different than Universal Transformer?

What does Universal Transformer do in comparison to this builder as the individual wire turns must be electrically insulated from each other to ensure that the current travels throughout every turn? Situations with low current and differences between adjacent turns is small, enameled or varnished wire seems fine; however, some companies will attempt to replace air spaces in the windings by saturating the windings with epoxy or some other substance.

I noticed that the builder does offer custom incremental changes in dB for the taps and the 1.5dB differences over 14 taps can offer a wide range of DIY potential.

Just like the ferrites vs. neo vs. alnico vs. field-coil arrangements for speaker/transducer motor assemblies, there is a debate on “best” for tube amps on c-core design vs. EI-core design output transformers. I have an acquaintance that swears by c-core design over the traditional EI-core design for tube output transformers, but I don’t believe that should be the sole measure of a purchase decision. With other factors being equal, I suppose there may be merits & limitations of both designs when a transformer is inserted in a signal path as an attenuator.

[SET12]

Isn't it something? AL

I have talked with others that have similarly done what I have done and they to have had as much satisfaction.

When I tried to suggest to some using your Universal, they felt the simple parts count with very high subjective quality parts did more for them.

Upon hearing the Universals in LaScala's it inspired me to improve the parts quality in my Fortes. Which did indeed vastly improve the sound.

Even more amazing is the level of satisfaction with rudimentary electronics though mine are a little less rudimentary.

I had a friend visit here from out of town that owns a pair of LaScala's equipped with the extreme slope networks that was very amazed at how such high quality parts could sound in the Forte's basic design. I was able to visit him as well to hear his LaScala's which I enjoyed the privilege of hearing. But in contrast to what my Fortes can do, I still would prefer the Fortes. In all likelihood setup and electronics can certainly be a factor.

But one thing I'd like to say is thanks for all your work, as without it I don't think I would of been as inspired to go as far as I have.

SET12

[zingo]

Did you do both speaker at the same time or did you do an A/B comparison with the stock/modified crossover?

Yes, I did one, than listened to them at the same time with the two difference XOs. I was surprised by the difference, most notably in the bass, but also in the clarity. However, I don't like A/B tests without a stereo pair as thats not how I listen and stereo mixes can throw things off.

Did
you glue the components to the wafer board? it's hard to tell from the
photos.

Yes I did.

Did you use stand-offs when mounting your new crossover
board so the foam doesn't get compressed?

I did not use stand-offs, but simply felt the foam as I screwed the boards down until they were tight and the foam was not compressed. I'll recheck them in a week or so to see if they have moved at all.

What type of audio gear
are you using?

I'm currently running a Shuguang Treasure 300B integrated, a more or less custom EL34 integrated, and a KingRex T20U+PSU Tripath amp. I've listed them in order of sound quality, but the KingRex getting props for its SS bass reproduction. For sources it's either my Sony SACD, or lossless PC files via separate DAC.

[Al Klappenberger]

set12,

Look carefully at the inductor placement that I "get away with". You will see that the smaller inductor is PRECISELY centered over the larger one and at a right angle. The magnetic fields from each induce equal and opposite energy into opposite sides of the other. I did a series of experiments where I actually measured the mutual inductance and found this mounting scheme works very well. There is virtually NO mutual inductance. You have mounted your smaller inductor to one side and off center. This position yields NO cancellation of fields. The only worse position would be one flat on top the other! What Dean has told you is quite correct.

Al k.

[SET12]

Thanks Al,

I'll make an adjustment

[zingo]

Thanks for all the work AL. I have read up on your work and it looks great. However, I wanted to start off with upgrading the stock XO and see where that got me. I assume I'll build your design down the road, but thought I'd start on that route.