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TOPIC: Frickelfest 2015

Frickelfest 2015 1 year 6 months ago #19774

  • curryman
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Dear all,

this weekend the Frickelfest will be held again in an old monestry in Hedersleben, Germany. The Frickelfest is a DIY audio meeting of roundabout 70 enthusiasts.

This year I will bring an Open Baffle with the good old Emminence Alpha 15a and an 8" Fullrange speaker (Gradient Axis AX-08). Woofer or both will be powered from the miniDSP ICEpower125, alternatively we will use the ICEpower only for the woofer and e.g. a tubeamp for the fullrange.

Since we will not have that much room in our car this year, I made the OB speakers fully dismountable.

Please find attached some pictures B)

I'll try to post some updates about other miniDSP related setups the next days, however internet is quite difficult there :ohmy:

stay, tuned, Daniel
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Frickelfest 2015 1 year 6 months ago #19778

  • john.reekie
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Cool, nice construction method :)
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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Frickelfest 2015 1 year 6 months ago #19818

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Great update Daniel! We keep forgetting of your yearly "pilgrimage" to the Frickelfest... :-)
We certainly look forward to seeing more pics and update. We'd post it in our blog to update the community.

DevTeam
MiniDSP, building a DIY DSP community one board at a time.
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Frickelfest 2015 1 year 6 months ago #19865

  • curryman
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Hi all,

thanks for your feedback.

A small update: we are just back from the Frickelfest and primarily need some sleep ;) Sorry for not posting the last days but Internet was terribly slow :(

I was a great event again with lots of amazing DIY builds. Please find attachd a picture of one of our setups (actually it was a constant evolution :) ). I will post some more details within the next days.

BTW: Frickelfest is also available on Facebook: www.facebook.com/frickelfest

kind regards, Daniel
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Frickelfest 2015 1 year 5 months ago #20113

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Hi all,
Almost three weeks after the Frickelfest I would like to recap a bit.
While traditionally many in the DIY community are more into purely analog audio, often with tubes, more and more digital systems can be found. Be it as a development system (I have seen at least four miniDSP 2x4 boxed), a fully digital setup (e.g. big Horn System using miniDSP 4x10HD plus Dirac) or mixed signal setups like our system.
This year there were quite many open baffle speakers as they proved to work very well given the quite difficult acoustic behavior of the rooms (many rooms are almost square shaped).
You can find a lot of very nice pictures on Flickr.
Some more Info on our System:
Signal Sources: two DIY turntables, one Rega based beltdrive with Well Tempered inspired arm and Nagaoka MP500 pickup. The other is a Dual direct drive, Arduino controlled (own development), again a Well tempered like arm and a AT440MLx pickup.
Phono Preamp: tube preamp using 6GK5 plus EC91 tube, both grounded cathode with variable passive RIAA inbetween.
Preamp: Calvin Buffer all SMD or 6J9P tube preamp
Poweramp: SymAsym, small PP tubeamp with ECLL800 and of course PWR-ICE 125
The Speakers:
As mentioned in previous posts we had open baffle speakers using Emminence alpha 15a as woofers and two different fullrange speakers. One was the Gradient Axis AX-08 and the other was a Ciare ch 250.

How I did come up with this design:

Well, actually I had this speakers lying around ;-)
I wanted to have a compact (well, compact and open baffle are not exactly the same ;-) ) speaker that is easily dismountable for transport (hence those furniture connectors). To keep the width of the speakers within a certain limit I used an U-shaped baffle for the woofer. Height should be 900mm and so I have chosen 556mm x 556mm baffle for the woofer according to the golden ratio.
The fullrange speaker has its own separate baffle (556mm x 344mm, again golden ratio). The position of the fullrange speaker on the baffle was simulated using the Edge baffle designer. Since the optimal position was very close to the golden ratio, I used this again. According to edge the first dipole peak is around 650Hz with only about +1.5dB compared to higher frequencies. Ripple above the first dipole peak is quite low and overall the baffle influence supports the initial frequency response of the Gradient Axis AX-08 very well. I used a 6dB highpass at 180Hz for the fullrange speaker and together with the effect of the open baffle this results in an acoustic 12dB/octave slope for the fullrange speaker. Consequently I used a 12dB/octave lowpass for the woofer.
Excellent information about dipole or cardioid woofer EQ can be found on John K’s technical studies pages (Music and Design is also offering the nice dipole systems NaO powered by miniDSP). According to John’s discussion about woofer EQ the Emminence Alpha 15a with its quite high Qts of 1.26 does not need that much EQ, surely one reason why it is so popular for open baffle applications. For a fourth order highpass response with Q=0.7 and Fc=40Hz in my baffle (556mm wide with 400mm “wings” -> Fp = c/2D ≈ 180Hz) everything that is needed is a simple peak filter with
Gain = Fp/Fc x Qd/Qts = 2,475 ≈ +8dB and Q = Qd/Qts = 0.55 at Fc = 40Hz
Easily done with the PWR-ICE 125 ;-)
Besides using the PWR-ICE 125 in 2ch mode amplifying the woofer and the fullrange each with one channel we also wanted to be able to try different power amplifiers on the Frickelfest for the fullrange speaker. Therefore we used a simple y-cable to split after the preamp. One output goes directly to the PWR-ICE 125 module, the other via a small series capacitor to the poweramp. With 100kOhm input impedance for example of my SymAsym an 8.8nF will give exactly the desired 180Hz 1st order highpass. We finally used a 8.2nF which corresponds to 194Hz, close enough. We could have switched to bridge mode for the woofer but didn’t manage to do so since we preferred enjoying good music ;)
Actually we received good comments about the system and some mentioned they were quite impressed by the sound quality of the PWR-ICE 125. Those “active speakers” were able to point out even small changes in the preamp and sources.

We also brought another small system, all battery powered using a Laptop, a miniDSP2x4, small class D amps, and 3” speakers (Tang Band W3-871) plus Wavecor W118WA01 woofer. This compact system delivered an astonishing performance and will be part of a portable vinyl player system that we will likely bring to the Frickelfest 2016.

Hope you enjoy my little report :)

Kind regards, Daniel
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