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TOPIC: miniDSP 2x4 equalizes old passive Speakers

miniDSP 2x4 equalizes old passive Speakers 5 years 5 months ago #18628

  • Hoffmann
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Hi Folks,

reading a bit through what people are using minioDSP for, I thought my quite recent (yet initial ) application for a friend may be of interest...

Well one of my friend moved houses and a pair of Atlanta 2000 speakers (from Denmark, built early 80s I guess) were "left over". Seeing them I thought: These boxes may suit my other friend well, who has no money to spend on good speakers. So I took the boxes home and listended. Well they sounded like my friend said: Nothing special, they were unused for many years...

Anyway, I let them play for several days and they improved somewhat, but were not getting great, especially the tonality was none of my taste. First I thought about modifying the passive x-over, but came to the conclusion that finding the right characteristics and according electronic parts wuld cost a bunch of money and would be very time consuming.

Finally I decided to do something seemingly unconventional:
Leave the speakers as they are, but:
1. Close the (very short) bass-reflex channel
2. Mount better Connectors
3. and most importantly use miniDSP 2x4 in a non-x-over configuration to
a. equalize the bass roll off with a bi-quad Linkwitz Filter
b. use the available parametric Filters and Equalizers of the miniDSP 2x4 to
. linearize overall frequency resonse
. minimise the differences between the R & L speakers
. tune tonality to my friend's taste

The way this was done, I'd like to share here.

Because I'm so well familiar with it, I did measurements with my DEQX PDC-2.6p System. Originally the R/L Speakers looked like:

By windowing the measurements (before first reflection arrival!) with help of the DEQX app. functionality, I derived a curve which the PEQs in miniDSP 2x4 would have to closely match (example):

Because of the needed number of PEQs and the "wanted" Linkwitz BiQuad Bass Filter, the 2.1 Adv. Plug In was programmed with PEQs from both the Input and Output PEQ sections (a few PEQs are actually left ;) )

The resulting listening position frequency response before and after equalization turned out as:

The achieved right/left speaker matching achieved is:

Listening Tests did (unexpectedly!) not yield a need for further change, so this "little project" was delivered causing great satifaction to the listeners, persiting until today.

Further to implementation: My friend uses an integrated Denon Amp which has a pre-out, but no main in . So we decided to place miniDSP 2x4 in one of the Tape out/in channels. The small inconvenience resulting from this is, that input channels now have to be selected by the Tape Input switch. My friend was happy to get used to that inconvenience, because of the reward of sound quality improvement!

Well, so much for my first, maybe unconventional miniDSP Implementation project. This experience has encouraged me to consider miniDSP for future projects.

One last thing is a finding of potential general value: When programming is done, make sure to provide VERY clean DC Power to MiniDSP! USB Power from the PC is DIRTY and this is audible as noise during low level listening!

I'd be glad to receive feedback and questions!

Kind greetings,
Last Edit: 5 years 5 months ago by Hoffmann.
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miniDSP 2x4 equalizes old passive Speakers 5 years 5 months ago #18630

  • john.reekie
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Nice work and nice report :)
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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Re:miniDSP 2x4 equalizes old passive Speakers 5 years 5 months ago #18660

  • devteam
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Great Feedback indeed Winfried and thanks a ton for sharing with the community. A nice use of the 2x4!
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