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Multi-Way Conventional loudspeakers with crossovers

ACR RP400 Isostatic tweeter (Fostex FT7RP) Exchange to a Visaton MHT12 ribbon tweeter
ACR RP400 Isostatic tweeter (Fostex FT7RP) Exchange to a Visaton MHT12 ribbon tweeter
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Old 25th October 2015, 06:59 PM   #1
BMW850 is offline BMW850  Netherlands
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Default ACR RP400 Isostatic tweeter (Fostex FT7RP) Exchange to a Visaton MHT12 ribbon tweeter

Hi all,

I've read on the Internet that Klaus Matschy has done a ACR RP400 tweeter (Fostex FT7RP) Exchange to a Visaton MHT12 ribbon tweeter.
But the end result (filter schedule) is unfortunately not talked about
My filter is the MK2 version.

But before I go to swapping out the tweeter, first I do is looking for the filter schedule.
Dit someone have the filter schedule for me?
Here is more info about the loudspeakers: rp 400

Kind regards,
Rudy
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Old 25th October 2015, 07:19 PM   #2
planet10 is offline planet10  Canada
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ACR RP400 Isostatic tweeter (Fostex FT7RP) Exchange to a Visaton MHT12 ribbon tweeter
If you ar elooking to replace broken tweeters Brian Cherry at diyHiFi supply might have some of the Fostex tweeters tucked away (i have a pair but i'm keeping them)

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These electrodynamic tweeters have fairly flat impedance curves making it easier to tweek the XO, but drop0in with no changes is unlikely to be optimum.

dave
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Old 25th October 2015, 09:50 PM   #3
BMW850 is offline BMW850  Netherlands
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No Dave, the Fostex FT7RP are not broken.
Have read on different German forums that this MHT12 loudspeakers are a good replacement for the Fostex FT7RP.
Hence my question if there might be people are here on the forum that can help me for the filter schedule.


Regards,
Rudy
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Old 26th October 2015, 02:28 AM   #4
Dissi is offline Dissi  Switzerland
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Hi Rudy,

I had a look at your request. Since it's a ACR speaker (and ACR is from Switzerland ) I'm glad to share my assessment.

Klaus Matschy wasn't happy with the Fostex tweeter because measurements and sound were disappointing to him and consequently he replaced it with the Visaton ribbon.

Fortunately the tweeter exchange is no big deal except for the different mechanical dimensions. The filter itself is not critical. Both tweeters have a flat impedance response and do handle a crossover at 5 kHz easily.

Hence the first attempt will be to exchange the tweeter and keep the crossover as it is. Based on the datasheets the Visaton tweeter probably is a bit quieter and you possibly want to remove the two resistors in the tweeter filter to make it louder.

Attached is a modified crossover that looks best in my simulation. The component values of the tweeter filter are different and the coil in the midrange section has changed from 0.33 to 0.47 mH. However, these are only minor adjustments which may or may not work. It's up to you whether you want to try that.
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File Type: jpg CrossoverBMW850.jpg (76.3 KB, 223 views)
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Old 26th October 2015, 05:27 PM   #5
BMW850 is offline BMW850  Netherlands
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Hi Dissi,

Must the Visaton MHT12, also be reverse connected?
But is this the schematic which also used by Klaus Matschy, you write it is from your simulation.
Don't know if you personal know Klaus Matschy, I would like contact with him via email
Thank you very much for the information.

Regards,
Rudy
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Old 27th October 2015, 01:43 AM   #6
Dissi is offline Dissi  Switzerland
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Click the image to open in full size.


I don't know Klaus Matschy personally but his homepage is here: index

I don't think he can help you with your project. He writes he was very satisfied with the Visaton ribbon, but he had serious problems with the crossover of the mid, the Fostex FS21RP. And then one day he came to the conclusion that the Visaton magnetostat simply is too precious for the Fostex speaker and deserves something better. So the MHT12 went into his new VisaTOM design and the Technics TH400 took its place in the Fosty.

My crossover proposal is based on a partial simulation of your speaker. Partial means only mid and tweeter are simulated, all woofers are missing. Attachment 1 is the result of the MHT12 with the current crossover, attachment 2 is the result of the modified crossover.
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File Type: jpg SimulationBMW850Original.jpg (98.8 KB, 193 views)
File Type: jpg SimulationBMW850Modified.jpg (98.8 KB, 186 views)
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Old 27th October 2015, 07:03 PM   #7
BMW850 is offline BMW850  Netherlands
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Hi Dissi,

Maybe I let anyone else do this project.
Time will tell, upcoming weeks I have it myself too busy to working on this project
Again thank you very much for the information.

Regards,
Rudy
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Old 27th March 2016, 07:02 PM   #8
BMW850 is offline BMW850  Netherlands
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I replaced the tweeter sounds good here you can see the video: https://m.youtube.com/watch?v=PTt6mTdEGss
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Old 27th March 2016, 07:39 PM   #9
BMW850 is offline BMW850  Netherlands
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Forgot to mention I also modified the crossover, thanks Dissi

Regards,
Rudy
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Old 27th March 2016, 10:59 PM   #10
Dissi is offline Dissi  Switzerland
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Thanks for the feedback. I'm very glad everything went well and I hope the new tweeter is an improvement now.

And your homemade CD player (https://www.youtube.com/watch?v=X0pkmtH0058), awesome!
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