Using Room EQ Wizard to create FIR filters for the A8’s DSP

This is an attempt to show how I created FIR filters using Room EQ Wizard and how it affects the output of my speakers to hopefully remove some of the ‘shortcomings’ of my speakers / room / listening position.

A list of what you need:

1: A labtop (PC or MAC)
2: A USB mic (like the miniDSP Umik-1 or Umik-2 - https://www.minidsp.com/products/acoustic-measurement (a callibration file can be downloaded from their site - basically a FIR filter for the mic to make sure it measures flat so it doesn’t add anything to your measurements)
3. Cables to connect everything (you can connect labtop with A8 via USB. This will also allow you to measure the result of your added FIR filters).
4. The free software from Room EQ Wizard - http://www.roomeqwizard.com

Documentation on how to use / setup Room EQ Wizard can be found on their site including links to Youtube videos that explain things. Start with the basics. No need to worry too much. Ask if you have questions.

Eversolo made ‘User guides’ for this as well.
DSP introduction: https://drive.google.com/file/d/11L7s07UBKyV9YjezP5b5eRwgUzA4a-jK/view
How to use REW for FIR filters: https://drive.google.com/file/d/1DZOYd1hO-6NtUy7VWn3waLtcIgbUIUEf/view

You might also want to install the USB driver from Eversolo and choose that as ‘Output device’ inside Room EQ Wizard (‘Input device’ will then be your USB mic):
https://www.eversolo.com/Support/support_guide/guide_target/vLEI82euofLeq7k9e[ld]3ulg==.html

I did not callibrate the ‘soundcard’ of my labtop which can be done in Room EQ Wizard. But this should not interfere with the measurements too much (but do it if you want).

The mic should be setup where your ears are located when at your listening position (I use a cheap mic stand from Amazon). One measurement per channel should be fine. It is possible to take more measurements around your listening position and averaging them out in Room EQ Wizard (if you tend to not always sit at the same spot or you are more people listening at the same time). But start with one in order to not make it too difficult…

My measurement for the left and right channel looks like this: (when done with USB cable to the A8 as in the Eversolo DSP user guide).
I had the volume of the A8 set for me to output a 75db sweep from Room EQ Wizard to my speakers for both the left and right channel. It’s important to note your output db. You will need to use the same level later when measuring again (with the added FIR filters to see the result of your ‘hard work’).

You can see that my speakers are ‘full range’ and can output a signal from 20hz to 20khz. I use 1/6 smoothing. This can be set in the top menu under ‘Graph’ for each channel. The result of your measurement will be a combination of how your speakers would measure in an anechoic room and what the room does to the sound coming out of the speakers. I know from the ‘amroc’ tool www.amcoustics.com/tools/amroc that I should expect room modes at around 48hz and 96hz (by typing your room size into their calculator). You see the peaks at those frequencies in my measurement. The dips or ‘nulls’ can be from speakers or the room.

After the two measurements you click the EQ button in the top menu. Follow the Eversolo PDF for this.

My settings for the correction curve can be seen here: (you can experiment with different settings).


The top red (left channel) and green (right channel) lines are my measurements. The bottom ones just below are the ‘Match response to target’ lines showing what you will get with your choice of settings. I chose a ‘Target level’ of 68db (the blue horizontal line) to not have any frequencies that are boosted. I chose 68db because it was about the spot where the biggest dip of my left/right measurement was (blue line just touches the dip at around 70hz of the left (red) measurement. I chose (like the A8 user guide) to not have a ‘Add room curve’. Adding a room curve / making the blue line have a slope downwards from left side to right side would give you more bass and less treble. See this video for an explanation:


This guy exports the FIR filters as a stereo file. You have to export each channel as mono / two seperate files as stated in the A8 user guide.

If you want to see the result of pressing ‘Match response to target’, first press it and let it calculate as in the A8 user guide. When done, click the ‘EQ Filters’ button at the top. You will then see which frequencies it decided to change and by how much. In my case it looks like this: (for the right channel). You see every frequency that it changed and in my case (because of my ‘target level’ it has pulled everything down / a minus in front of every db).


Now close the pop-up ‘EQ’ windows and go back to your original measurements window.

Go to ‘File’ / ‘Export’ / ‘Export filters impulse response as wav’ and save the left and right channels to your labtop. The files should be put on a USB stick and inserted in your A8.


On iPad it looks like this inside the DSP. You have to click the plus icon to add a configuration, then click the FIR filters and import the left and right channel files from your USB stick.


To start with set up the ‘USB-B in’ with your config and make sure to turn on the left and right FIR filters and the USB-B in port.

You can also add the config to any of your other inputs like ‘internal player’ but first we want to measure the result of these FIR filters.

Close Room EQ Wizard (do a ‘Save all’ first) and open again (or just click ‘Remove all’ and then the ‘Measure’ button to get started on a new measurement.

We want to measure the result of the added FIR filters, so make sure that they are ON for the USB-B input. Before you start a new measurement, do a ‘Check levels’ again. If you like me chose a target level (of 68db) below the 75db (I used for output), you might have to turn up the volume of the A8 to get the ‘check levels’ to show 75db again. Hence, we want to do all measurements at the same level and using a FIR filter might lower your output level.

My measurements now look very different / flat (because I chose no ‘Add room curve’).


Whether it sounds good is a whole other discussion. But we can always open up the original Room EQ Wizard saved measurement, enter the ‘EQ’ button, change some settings and do a new ‘Match response to target’ and then finally export the new FIR filters and import them to the DSP. If you create a new config each time and give them a matching name, you can switch between them and see what settings you prefer.

I will add more links to Youtube videos / documentation elsewhere depending on your feedback.

Hopefully this will make you want to give FIR filters a try. I’ll do my best to answer questions and hopefully others will too.

 

These are MY choices / settings / way to do it. There are many choices to make and playing around with settings / trying out different settings should be seen as part of the fun. Let’s inspire each other with how we did it and more importantly why we did it. Many factors play a role when it comes to what you do and which results you get.

Some speakers might emphasize certain frequencies because of… well, many reasons for this (brand preference or just technical issues that they could/would not fix). If your speakers cannot play frequencies below 100hz, you will not be able to change this with FIR filters but you would also have less problems with room modes / standing waves that mostly are problematic below 100hz.

If you want a ‘less intrusive’ FIR filter, you could choose to only measure certain frequencies and you would therefore also only be adding changes to your speakers in that frequency range (say from 20hz to 200hz).

Then there is the issue of your listening room including speaker placement and listening position.

Topics to look into in order to better understand the reasoning behind FIR filters could be.

1. How your speakers measure in an anechoic room with no influence from the room (output of speakers when fed a frequency sweep from 20hz - 20khz where all frequencies are the same volume / SPL. The speakers will not measure flat / play back every frequency at the same volume). I like the image of a person playing each key of a piano with the same force but some keys sound louder due to the piano not being ‘perfect’ (in an anechoic room).

2. Room acoustics - what the room does to the sound coming out of your speakers. This is a huge topic with many sub topics such as:

*room size (room modes / standing waves / room shape ie. not a perfect square or rectangle)
*construction materials (hard / soft walls / reflections / non-symetric room)
*speaker placement (‘don’t put baby in the corner’ or else… / speaker boundary inteference response)
*listening position (choosing a spot not in a dip or peak of a room mode)
*room treatment (absorbers / diffusers). You could call this a FIR filter for your room (that the room interferes less with the sound from your speakers.

All of this will have an influence on what you hear (and I personally think this is a much more important thing to work on than having the ‘right equipment’). The right equipment will sound fantastic with everything else being optimized but poor / cheap speakers set up correctly might sound just as good as the ‘right equipment’ setup in a non optimal way.

The easiest thing to ‘fix’ before creating FIR filters would be speaker placement and your choice of listening position (including less furniture between you and your speakers / having symmetry. Measurements can help figuring out what the optimal speaker placement and listening position is (going for having less dips and peaks in your measurements). The rest might be a bigger job that would require much time/money and a divorce…

All of this might be obvious to many but in the spirit of not ‘leaving anybody behind’ and hopefully trying to be as helpful and empatic as possible. Let’s do this the only way I know, my way And the obvious disclamer: I’m just a silly novice who is determined to ‘keeping on learning’ and not being ‘affraid to make mistakes’.

 

Youtube videos to learn about topics related to room acoustics / general acoustics.

Geoff Martin playlist. He works/worked as ‘Tonmeister’ for Bang & Olufsen.

https://youtube.com/playlist?list=PLiZaccpD4XoLywgMwl55N2h3cB3hKxZmj&si=mZVjiRk4qkB91hvP

And Jesco Lohan of Acoustics Insider about what your room does to the sound of your speakers including room treatment and listening position.



One of the better videos on room modes / standing waves and loudspealer placement.



And Acoustic Geometry’s video on room modes and why the listening position is important. (And room treatment)…



GIK Acoustics about speaker placement / speaker boundary inteference response / room treatment:

 

Reserved…

 

And because there are many opinions on how to do this, here is a ‘second opinion’.

This video talks about a ‘house curve’ (tailored target curve) and has an opinion on why you shouldn’t use a ‘too low’ target curve as I did in my example.

He also talks of EQ APO which is not relevant for the Eversolo A8.

 

What a great posts.....congrats and thanks for all your articles Bergholdt ....!!!!!!!!!!!!!!!!!!!!!!

 

This is from the Audio Science Review forum - a good read (but maybe only for the most nerdy of you)…

‘Some comments from Floyd Toole about room curve targets, room EQ and more’

https://www.audiosciencereview.com/...ut-room-curve-targets-room-eq-and-more.10950/.

Floyd E. Toole is one of the main people behind the study of ‘sound reproduction’ and the ‘Harman curve’…

 

I added a few more FIR filters to my DSP. This time two with different downward slopes (giving me more bass and less treble).

This is done with the ‘Add room curve’ feature as shown.

First the result of a -2 curve (0,2). See the yellow marking.
(the blue line inside the ‘EQ’ is no longer horizontal but slopes down - left to right).


And here a -5 curve…


You can especially see that the treble drops below the 75db output line.

For me the -5 curve (0,5) is way too much bass, but you can experiment. Not all speakers / rooms are the same and we will hear different results.

Here my ‘Flat’ curve with no added ‘Add room curve’ just for reference…



And here is how it looks on the iPad when I have more FIR filters to choose between…

 

Very interesting, thanks for the effort to share this information with us. I am very sure that many will find it useful.

 

John Darko (on Youtube) has made a few videos about room treatment and why you’d want to do it.

This one has side-by-side comparisons (literally his room and the next door neighbours room) and is a good watch if you want to learn more.



And for a quick, very visual workshop on Room Acoustics and Speaker Placement (from a studio point of view), you can check out this short playlist:

https://youtube.com/playlist?list=PLoS5BFrHtKd3arlVl4QMN_8eM_gYKFEzx&si=HyMLeM1JPdG_ieAF

 

Thank you very much for your help. I tried to try it on my computer, but I could not open a page, so I could not filter it. I would like to ask you, if possible, could you show me your equalizer settings as a picture, for example, what are the 31.5 settings, what are the 63 settings? If you could upload your other settings as a picture, I would be grateful. You know the subject very well. I realized that I could not achieve this task

 

Your speakers will measure different in your room, so my settings will not work for you.

You really need a measurement in your own room for EQ / DSP FIR filters to make sense.

And the frequencies inside the PEQ don’t have to be as shown. You can choose to change any frequency.



See this short video about PEQ.


And this longer video:


I use FIR filters to remove the boosts in some frequencies due to room modes. My speakers then play less of those frequencies to make all frequencies play at the same volume…

 

@Bergholdt thanks for this, this has been needed for some time.

 

If you have two and a half hours to dig into FIR filters / DSP and some of the science behind it, you might like this video.



Mitch Barnett (of Accurate Sound - https://accuratesound.ca/ ) has some nice slides that explain things in a visual way (I don’t get all of it, so you’re not alone if you don’t either)

And if you didn’t already watch it, let me point you towards the Floyd Toole video above.

 

And if you want to learn a bit about how different measurements can tell us about how a speaker will sound in your room, here is a playlist from ‘Erin’s Audio Corner’: https://youtube.com/playlist?list=PLoS5BFrHtKd1WgA7PKu0GtRa4n2XtLUKV&si=yZygHEnfMkSPBUqD

1: Frequency response
2: Off-axis vs. On-axis response
3: What the heck is Spinorama
4: In-room prediction
5: Loudspeaker compression

Erin uses a measuring device from the German company Klippel (for anechoic measurements in a non-anechoic room) - https://www.klippel.de

 

HDMovieSource has a lot of videos on the subject and instructions for how to develop PEQ filters and target curves. I really like his channel and he does a good job of explaining things.

 

I

 

Köknar filtresi ayarlarını umık1 ile yaptım, ekolayzır ayarları otomatik olarak geldi, cihaza kurdum, köknar filtresi şu an aktif ama sesini hiç beğenmedim ve bir de dışarıdan patlamaya benzer garip sesler duyuyorum. konuşmacı.

 

If you don't like its sound depends on what you are used to, and how you made the measurements.
Then, for the crackles / pops... usually, when you make EQ adjustments, there are some frequencies that get boosted; for this reason you MUST set the initial gain to something like -3dB (note the minus sign!), in order not to have the loudest peak in the music exceed the 0dB treshold and clip / distort.