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Al Klappenberger

Developing a network for the Forte

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Set,

No.. The stock networks don't follow any theory at all!

2 nd order filters shift phase 45 deg / element. The lowpass shifts 90 deg one way and the "mirror-image" highpass shift 90 deg the other way. The result is 180 deg shift in phase at the crossover. The propogation time difference between the drivers shifts the sound some more. It becomes unpredictable and only at the exact crossover.

Al K.

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Thanks Al,

So electrically its a mess!

I have heard your work on LaScala's, it really transformed them for me to real performers.

The mids were just way to elevated with the stock networks IMO.

Thanks for all your Klipsch work!

SET12


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Al,

Many thank for sharing your work, theories, and measurements.

Nelson Pass does much the same and I put Al in the same very high category. Gifted people who educate us all.

Wm McD

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Al:

Suppose someone were to build a set of speakers using the Forte squawk and tweet horns, and Bob Crites' K33 woofers. I have done this, installing them onto a custom motorboard and cornwall enclosure, creating a "CornForte" of sorts.

Given that, how would one modify your schematic above to accomodate a K33 woofer? I imagine the impedance curve of this unit would vary reasonably from the Forte woofer. Can you advise? Many thanks.

Chris

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Chris,

You would need to combine a different low frequency section with the high section. The Zo of the K33 is about 6 to 7 Ohms. the Forte woofer is around 5.6 Ohms. The second version of my Cornwall network would be close. The 18 ohm swamping resistor would need to be changed to about 33 Ohms. After all this the levels of the high section may not match the woofer. If that happens the fix may not be simple. More instrument testing might be needed.

AL k.

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Al:

Where do I send the speakers for you to test/tweak? [:P]. I appreciate the input, I suppose there would be a great deal more work needed on something like that. I can't imagine adding some parallel resistance to the K33 would be a good idea (to make it "look" more like the Forte woofer), since you are talking about total Zo, and not just a resistive load (as is always the case).

I may try to do some experimentation and see what I can come up with, or, I may even dismantle these speakers and go back to the standard Forte with your networks. This is a very interesting topic, thanks!

Chris

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Any one else tried this mod? Any listening impressions?

Maybe I will gave it a try. My concern is that I have replacement titanium tweeters from Bob Crites. If old ones are too bright with this mod, titanium will be even more bright.



Regards

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The forte owner who got Al's networks had a post about them and was very pleased with the results.

I can not remember if the post was on 2 channel or updates.

Al might have the review.

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From my point of view, there has been no interest in this network. I have had only one person ask about it. Several have asked about networks for the newer version, the Forte II, but that's all.The design is downloadable from my web site for anyone who wants to make it a DIY project however.

Al K.

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Yes, i got the prototypes that Al created. In Al's home he set up a cool way to switch instantaneous between the stock speaker and the new design. Their was a definite clarity difference when listening to them side by side but not an overwhelming difference like his Universals made to my LaScalas. I use the Forte's for front speakers of a home theatre so i don't have any real seat time just listening to music on these so a long term review is unavailable. I think the DIY option is a smart move since Al's labor involved to build would of course bring the cost up for just a modest improvement. PLEASE NOTE that this is my opinion only. Al makes a fantastic product and would purchase another product from him anytime whenever i venture into more speakers.

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Thx for info. And how you define this clarity, is it full ranege orat some scpects of the sound. My goal/wish would be to improve high midrange and highs. They are much better at old Cornwall. When I've heard Hi-hats on them, I have fall in love in Cornwalls. They where much more naturall from dose form Forte.

Al K.

Fortes are rather cheap speakers (but worth of every dolar spend on them) and maybe that is the reason not many people are intrested in changing networks.

For the feature I am planing Conrscala's but now I may gave a try to yours networks. I have some ofe the components on stock.

If it is not a secret how did you made switch between old and new crossover? There is at least 5 wires to switch. Some rotary switch?

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The speakers mid and tweeter had more life to them. A touch louder with a little better definition especially on the midrange. i didn't hear any noticeable change at all to the woofer but i don't have a trained audiophile ear either.Hope this helps!

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The gasket thing reminds me of an observation I made about this particular speaker. Our friend Max says the woofer box should be air tight. By that you should be able to push in the passive radiator and see the woofer pop out and STAY OUT! It doesn't. It only takes a fraction of a second to pop back to the center position. The box is NOT air tight. Has anybody ever done that with a new speaker using a passive radiator to see how long it takes for the pressure inside to leak out?

Sorry for digging up a thread from last year, but old speaker gaskets can be replaced with Mortite rope caulking or a similar product. It is not only a better seal than the original and does not dry out, but also couples the driver to the cabinet. I have redone many speakers with it including my Fortes, and it definitely makes a difference.The only word of caution is that you have to check the tention of the mounting screws after about a week as the Mortite is a clay like material and can compress a little initially.

As far as passive radiators go, a sealed cabinet will never be 100% sealed as they usually have some losses with the cabinet construction, or even through the dustcaps of woofers as they are not 100% air tight. A good seal is considered when you can push on the passive radiator, and the woofer takes at least 3 seconds to return to normal; obviously the longer the better. I started by replacing just the seal on the passive radiators on my Fortes, and that alone put me over the 3 second mark.

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This thread looks familiar somehow!

The "sockets" mounted through the front motor board that holds the grill look to me to be a source of pressure leaks too. The speaker used in this thread had one that would actually fall out if it got the chance!

Al K.

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Would you mind posting the schedmatic for the stock Forte network? I have collected quite a few Klipsch crossover schemtics, but this is one I have not be able to ascertain. Also, is the stock autoformer a T2A, T5A or some other model? Thanks...

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With a little more digging, I found one (see attached). That said, anyone know the dB drop the midrange is getting with that autoformer. The schematic does say "T10A was T2A" so I would think it would be 9dB -- but I wanted some confirmation.

Forte[1].pdf

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On ‎6‎/‎13‎/‎2009 at 3:54 AM, Al Klappenberger said:

...... 

I did some investigation into what parts Klipsch used in similar speakers (Forte II, Chorus and Chorus II). It turns out that they are all different enough that this design will ONLY work properly with the original Forte.

Stay tuned. I will be starting the testing soon.

Al K.

 

post-2934-13819475763616_thumb.jpg

Was there ever a Forte II version?

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Yes, Al has a crossover which works with both the Forte & Forte II. The cost is $340/pair, and if you send in the stock networks, Al will issue a $48 credit.

 

Go to alk engineering and select Overview to see a pic, and Price List for cost.

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23 hours ago, Blvdre said:

Yes, Al has a crossover which works with both the Forte & Forte II. The cost is $340/pair, and if you send in the stock networks, Al will issue a $48 credit.

 

Go to alk engineering and select Overview to see a pic, and Price List for cost.

Thanks but was hoping for a DIY version like the Forte I to cut costs

Edited by Alexander

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