Klipsch Forte III Upgrade with Pictures!

jmpsmash · « **Reply #200 on:** 26 Jan 2020, 03:09 am »

Quote from: poseidonsvoice on 26 Jan 2020, 12:12 am

Thank YOU and Rusty Jefferson for communicating this truth. I am shocked by how many tube owners don’t know this!

What the output impedance is at a respective tap has to do with the dynamic plate impedance (which is related to the BIAS) of the tube used, the turns ratio of the output transformer and whether it is a SE design or PP design. Not to mention the fact that the output impedance isn’t a static number. It varies by frequency. Most “estimations” are at 1khz, but most dynamic driver based loudspeakers have their impedance nadir at 100-300Hz!

So how does one know the actual output impedance of an amplifier? Measure it from 20-20khz.

Best,
Anand.

I am not surprised that not everyone knows it. The explanation is quite technical. I have been a tube amp owner for many years and only learned it recently after I started designing my own amps.

Just wondering, how do we measure the output impedance of a output transformer tube amp over the frequency range?

poseidonsvoice · « **Reply #201 on:** 26 Jan 2020, 03:44 am »

Quote from: jmpsmash on 26 Jan 2020, 03:09 am

I am not surprised that not everyone knows it. The explanation is quite technical. I have been a tube amp owner for many years and only learned it recently after I started designing my own amps.

Just wondering, how do we measure the output impedance of a output transformer tube amp over the frequency range?

Here is the simplest method I have seen:

http://homediyelectronics.com/tutorials/howtomeasureoutputimpedance/

The more sure method is to use an Audio Precision device or similar. Expensive, yes. Of course there are less expensive analyzers (with less resolution, but resolution isn’t an important criteria to measure output impedance, it is important for measuring distortion, noise and dynamic range). I am looking for the least expensive method, which hopefully involves using Room EQ Wizard, a free piece of software, which now has an oscilloscope in it too. That being said, I will probably be purchasing an oscilloscope to add to my measurement gear. I already have a signal generator.

Here is a quick calculator if you have the measurements:

http://www.sengpielaudio.com/calculator-InputOutputImpedance.htm

Best,
Anand.

Bmarshall · « **Reply #202 on:** 1 Mar 2020, 04:49 am »

Hi All.

New here, but I received the upgrade kit last week and started work on it.

Will post picture and comments as I go!

Here are the initial pics.

*removed schematic pics

Bmarshall · « **Reply #203 on:** 1 Mar 2020, 07:58 pm »

Today's progress. Crossovers mostly done and braces in.

Jules1 · « **Reply #204 on:** 2 Mar 2020, 03:03 am »

Quote from: Shakeydeal on 27 Dec 2019, 08:20 pm

As good as the forte III is, and it is very good. It’s still not in the league of the mighty klipschorn. Not really much of a debate actually.

Shakey

Having heard Tyson's Forte speakers, and still owning a pair of aged Klipschorns. My thoughts are that my 'stock' Klipchorns are behind these Forte's in every compartment. I was taken aback on how good these Forte's sound.

Tyson · « **Reply #205 on:** 2 Mar 2020, 05:23 am »

Looking good man!!

FullRangeMan · « **Reply #206 on:** 2 Mar 2020, 05:56 am »

Twelve inductors !

maty · « **Reply #207 on:** 2 Mar 2020, 07:18 am »

In the future you can try add 2+1 Miflex KPCU-01 0.01uF 600Vdc as a bypass the Sonicaps after you have memorized the new sound.

Tweeter (2) and midwoofer (1).

http://www.humblehomemadehifi.com/Cap.html

Bmarshall · « **Reply #208 on:** 2 Mar 2020, 08:19 am »

What does a bypass capacitor do?

maty · « **Reply #209 on:** 2 Mar 2020, 08:46 am »

To this day I still can't find an academic explanation that justifies as much difference in sound as I have seen with these Miflex. According to Danny Richie, it seems to make it easier for the capacitors to charge and discharge the electric charge much faster.

In my case, in my modified KEF Q100 the difference was amazing, undeniable.

The difference between the baffle with the Miflex and the other without it was overwhelming. With the best version I have and / or that I have never heard of Hotel California (Eagles), 24/192 vinyl rip.

* https://www.diyaudio.com/forums/music/6958-playing-listening-post5652477.html

-> https://www.diyaudio.com/forums/music/6958-playing-listening-853.html

maty · « **Reply #210 on:** 2 Mar 2020, 09:32 am »

If you dare to do it, first only with one box and thus compare with the other. You play a recording that you have of reference, of great sound quality and high dynamic range and verify how much improvement there is.

I suspect that the M.D.L. capacitor and the resistance of the Q100 should be very damaging to the sound, so the yellow condenser will probably change as well. The oil ones (3.9 uF) are too big for those boxes!

KEF Q100 crossover: [IMG, link] https://www.audiocircle.com/image.php?id=204399&size=huge

PS: It is assumed that one day I will rebuild the crossover, with point-to-point welding, new wiring (probably first with star-quad geometry, cheaper) and other binding posts (with low mass and... without magnetic washers, just welding).

Tyson · « **Reply #211 on:** 2 Mar 2020, 05:31 pm »

Quote from: Jules1 on 2 Mar 2020, 03:03 am

Having heard Tyson's Forte speakers, and still owning a pair of aged Klipschorns. My thoughts are that my 'stock' Klipchorns are behind these Forte's in every compartment. I was taken aback on how good these Forte's sound.

Thanks Jules - glad you enjoyed them. Saturday's CAS meeting was a blast!

Jules1 · « **Reply #212 on:** 3 Mar 2020, 01:52 am »

Absolutely Tyson, no better way to spend a Saturday afternoon, a great host, wonderful sounds from both sets of loudspeakers. Not forgetting the wonderful eats.
I hope somebody sends Danny a pair of Klipschorns to fix the issues that they have. Mine are in the two corners of our dining room not connected. They need work to get them to where i would like them to be musically.

corndog71 · « **Reply #213 on:** 3 Mar 2020, 03:29 am »

Quote from: Jules1 on 3 Mar 2020, 01:52 am

Absolutely Tyson, no better way to spend a Saturday afternoon, a great host, wonderful sounds from both sets of loudspeakers. Not forgetting the wonderful eats.
I hope somebody sends Danny a pair of Klipschorns to fix the issues that they have. Mine are in the two corners of our dining room not connected. They need work to get them to where i would like them to be musically.

The first thing you could do is add No Rez to the cabinets.

Bmarshall · « **Reply #214 on:** 3 Mar 2020, 04:47 am »

More progress... Can't wait to leave the office for evening extra ciricular...

maty · « **Reply #215 on:** 3 Mar 2020, 07:51 am »

Maybe also No-Rez on the back of the front is a good idea. Danny and Tyson what do you think?

Bmarshall · « **Reply #216 on:** 3 Mar 2020, 09:57 am »

Quote from: maty on 3 Mar 2020, 07:51 am

Maybe also No-Rez on the back of the front is a good idea. Danny and Tyson what do you think?

Yeah, it's coming!

maty · « **Reply #217 on:** 3 Mar 2020, 11:07 am »

Girated, clarified and optimized

Click on image -> Huge

Front, back and sides, how much ~~thick~~ thin MDF?

maty · « **Reply #218 on:** 3 Mar 2020, 11:12 am »

To compare. NX-Studio, inside with No-Rez by Sonicjoy
https://www.audiocircle.com/index.php?topic=168181.msg1786544#msg1786544

Resized and optimized

https://www.audiocircle.com/index.php?topic=160647.msg1764167#msg1764167

Quote

1. MDF is fine. It is dense and less resonant than other materials. It is also cheap and easy to purchase and cut.

2. The front baffle is 1.375" thick [MDF] already. So there is no resonance issue. Also the woofer frame is made from a polymer material that is non-resonance and will not transmit a resonant to the front baffle like most woofers. And it surface mounts so baffle material is not removed for mounting like many drivers that have to be recessed...

Bmarshall · « **Reply #219 on:** 3 Mar 2020, 03:25 pm »

Last shot, all reassembled.