• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

MiniDSP 2x4 advanced plugin tutorial: integrating anechoic EQ filters

ethernode

Member
Joined
Dec 27, 2022
Messages
55
Likes
14
Hello everyone; i'm relatively new to this, and struggled a bit to setup, so i thought i would share what i learnt.

To put things into context, i had the opportunity to buy Kef LS50 (1st gen) for a very low price (380€) and i own a used MiniDSP 2x4 (non-HD, the 48 Khz one, which i bought used for ~70€) and an SVS-SB1000 sub. I wanted to implement the optimized anechoic EQ settings that @Maiky76 kindly provided here, but it wasn't that easy as a beginner.

The goal for this tutorial is to help newbies like myself deploy optimized EQ filters sometimes found on this forum (like the one below) on this MiniDSP platform.

Code:
Preamp: -0.9 dB

Filter 1: ON HighPass Fc 75.31,    0.00,    1.48
Filter 2: ON HighPass Fc 90.38,    0.00,    0.74
Filter 3: ON PK Fc 152.65,    -3.17,    0.78
Filter 4: ON PK Fc 550.00,    1.40,    3.72
Filter 5: ON PK Fc 830.00,    -2.40,    1.83
Filter 6: ON PK Fc 1224.00,    -1.34,    9.45
Filter 7: ON PK Fc 1609.00,    2.11,    2.65
Filter 8: ON PK Fc 2764.00,    -2.80,    1.35
Filter 9: ON PK Fc 4747.00,    -3.40,    3.00

As reminder (this is common knowledge, but that wasn't clear to me so i'll repeat it for beginners like me), we want to apply these mostly for correcting frequency response above the schroeder frequency where the perceived sound is mostly dictated by the speaker behaviour (below this frequency, the room is mostly affecting sound so there's little one can do without measuring your own room). The filters above have been computed based on frequency response measurements achieved in an anechoic chamber or alternative, room-independant measurements (like the Klippel system), with an algorithm that targets to maximize the Harman speaker preference score [reference needed].

It was not that straightforward to apply the filters above, notably because
- MiniDSP seems to have released their 2x4 advanced "plugin" relatively late, so most information regarding the use of the MiniDSP 2x4 is kind of outdated (e.g. the REW UI assumes 6 BQ and not 5, tutorials are for other plugins, etc ...)
- the MiniDSP 2x4 has 5 band PEQs, not 9, so a splitting strategy must be defined
- the crossover parameters (HighPass filters 1 and 2) described above need to be input as biquads (advanced mode)
- although i already did auto-EQ with REW, i did not know how to convert manual/custom PEQ parameters in REW into biquads usable into the MiniDSP

The MiniDSP 2x4 plugin specsheet states that there is one 5-band PEQs available per input and output channel (5 biquads each), as well as 4 LPF/HPF block that consists of 8 PEQs (confirmed by MiniDSP support).

1677600824041.png


Based on the above
- i applied the preamp gain in the first blocks
- i routed Left into output 1, routed RIght into output 3, output 2 gets L+R summed signal for the sub
- i placed filters 5-9 into the the downstream 5-band PEQ blocks, and filters 1-4 into the LPF+HPF block

This should leave 4 biquads after the matrix and 5 before (full band) for room correction. Below is the setup:

1677600630501.png

To generate the biquads using REW, i followed the following steps:

1. Click "EQ"
1.png

2. Select miniDSP eq type, click "EQ Filters"
2.png

3. Insert the high frequency components (only 5)
3.png

4. Export coefficients to file
4.png

5. Do the same for the crossover block, but the exported file should be completed with 2 disabled biquads (the MiniDSP expects exactly 8 biquads), which i did by copy-pasting (the files are available as attachments)
5.png

6. Spin up the MiniDSP plugin UI, configure the routing
6.png

7. Select the crossover block, click "Advanced", copy-paste the xo_8bq.txt file contents, hit "Process" -- the UI does not offer an "Import REW file" button here -- which is also why i had to fiddle with it to reach 8 biquads; do this also on the crossover of Output 3

7.png

8. Move on to the PEQ - output 1 block, click "Import REW File", import "after_xo_bq.txt"

8.png

9. Click "Copy to output 3"

9.png

10. Apply a 24 dB/octobe Low Pass LR filter on Output 2 (sub)
10.png

11. Apply the -0,9 dB gain on the Input Gain block
11.png


I included the full XML settings file for convenience.

Things i did not understand:
- could i have used any other 48 Khz Equalizer in the REW window (to avoid having to split the biquads in two steps) ? Or will REW possibly apply format tweaks on the export ? Why is REW limiting MiniDSP EQ to 6 band only ?
- not sure how to configure the low pass for the sub to match the modified high pass

Feel free to feedback if you know better ways to achieve the above ! I hope this helps someone.
 

Attachments

  • xo_8bq.txt
    652 bytes · Views: 50
  • after_xo_5bq.txt
    676 bytes · Views: 38
Last edited:

Purité Audio

Master Contributor
Industry Insider
Barrowmaster
Forum Donor
Joined
Feb 29, 2016
Messages
9,051
Likes
12,150
Location
London
It is the frequencies below Schroeder that can cause the really severe problems if you have a ’traditionally’ furnished room I would leave the higher stuff alone.
Keith
 
OP
ethernode

ethernode

Member
Joined
Dec 27, 2022
Messages
55
Likes
14
I understand, but can you elaborate why ? Note that i do not intend to correct high frequencies with in-room measurements.
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
7,423
Likes
7,940
Location
Brussels, Belgium
I understand, but can you elaborate why ? Note that i do not intend to correct high frequencies with in-room measurements.
Feel free to correct frequencies above 200Hz with anechoic measurements. it's actually recommended. I'm a little occupied right now, I will reply thoroughly in a bit to answer your questions.
 

Triliza

Senior Member
Forum Donor
Joined
Jun 23, 2021
Messages
477
Likes
558
Location
Europe
Good of you to post the steps, I am also fiddling with filters (using Moode/CamillaDSP) and it is challenging to get it done starting from the ground up, many things to learn.

Regarding applying filters on anechoic measurement, I'd like also to know why it matters at what frequencies you apply the filters, I was under the impression you apply them whenever they are needed to flat the curve (as much that is possible for each speaker, without messing other metrics), regardless of the frequency.
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
7,423
Likes
7,940
Location
Brussels, Belgium
I simulated a crossover and it seems Butterworth 12db/oct highpass at 80Hz for the LS50 and Linkwitz-Riley 24db/oct lowpass at 80Hz for the sub seem to sum pretty nicely. If you use the MiniDSP to apply the lowpass, then make sure to disable the built-in lowpass of the subwoofer (read the manual).

1677615700352.png
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
7,423
Likes
7,940
Location
Brussels, Belgium
Also, these Maiky’s filters are weird. I would drop everything below the 550Hz one.

With the crossover i supplied the response should sum to anechoicly flat without them anyway below 500Hz.
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
7,423
Likes
7,940
Location
Brussels, Belgium
Other than these two pieces of advice, I would say you’re on the right track!

Tinker further to your liking and enjoy the journey!
 
OP
ethernode

ethernode

Member
Joined
Dec 27, 2022
Messages
55
Likes
14
I simulated a crossover and it seems Butterworth 12db/oct highpass at 80Hz for the LS50 and Linkwitz-Riley 24db/oct lowpass at 80Hz for the sub seem to sum pretty nicely. If you use the MiniDSP to apply the lowpass, then make sure to disable the built-in lowpass of the subwoofer (read the manual).

View attachment 268308
Nice, thanks ! What about a 100 Hz crossover ?

Yes sub is in LFE already ;)
 
OP
ethernode

ethernode

Member
Joined
Dec 27, 2022
Messages
55
Likes
14
Also, these Maiky’s filters are weird. I would drop everything below the 550Hz one.

With the crossover i supplied the response should sum to anechoicly flat without them anyway below 500Hz.
I don't know how @Maiky76 did generate the crossover, he did not say how, but apparently he took the filters without the high pass, then determined a custom high pass that allows to keep the lowest frequency filters (vs the the 24 dB LR high pass I was about to use).
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
7,423
Likes
7,940
Location
Brussels, Belgium
Yeah I think these filters are back in the old days before Maiky optimized the algorithm, i would just take the filter at 550Hz and above.
 
OP
ethernode

ethernode

Member
Joined
Dec 27, 2022
Messages
55
Likes
14
Btw my sub is sealed, shouldn't it matter for the low pass slope ?
 
OP
ethernode

ethernode

Member
Joined
Dec 27, 2022
Messages
55
Likes
14
To satisfy your curiousity about the 100Hz crossover.

View attachment 268524
Thanks for spending the time !

I see a larger bump on the 100 Hz one, and horizontal directivity seems smoother with 80 Hz xover, but i'm not sure because the scale is not the same (i opened both images in 2 tabs to compare) -- not to be picky !

What's your analysis ?

I'm guessing the phase should just be ignored (in real life i should time-correct it, right ?)
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
7,423
Likes
7,940
Location
Brussels, Belgium
Thanks for spending the time !

I see a larger bump on the 100 Hz one, and horizontal directivity seems smoother with 80 Hz xover, but i'm not sure because the scale is not the same (i opened both images in 2 tabs to compare) -- not to be picky !

What's your analysis ?

I'm guessing the phase should just be ignored (in real life i should time-correct it, right ?)

stick with the 80Hz unless you're listening at further than 1-2 meters.
 
OP
ethernode

ethernode

Member
Joined
Dec 27, 2022
Messages
55
Likes
14
Are you saying that because at high power the LS50 will suffer producing 80 Hz ?
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
7,423
Likes
7,940
Location
Brussels, Belgium
Are you saying that because at high power the LS50 will suffer producing 80 Hz ?
pretty much. I have a 5.25 inch woofer in my living room crossed at 80Hz and i think it's fine at short distances. I definitely don't see it moving.
 
OP
ethernode

ethernode

Member
Joined
Dec 27, 2022
Messages
55
Likes
14
@abdo123 just found your post where you said you recommend 95hz cover, do you still think that ?


Would you mind sharing some project file for VituixCAD so that I can try to play with the different HP/LP filters and xover freq ? Or maybe I should just try all available on the minidsp and measure + listen...
 
Top Bottom