My Take on Stereo Tuning using REW

This is in no way a definitive guide on how to tune your stereo, but its what i've learned over the last couple months of tune and re-tuning my stereo.

See post #2 below for how to set the gains correctly, this should be done before you tune.

I am using the Helix DSP Pro Mk2 and a MiniDSP Umik-1 measurement microphone along with RoomEQ Wizard. You should be able to follow similar procedure for any real dsp. The Helix does have a built in RTA, but there isn't much information on it so i opted for using the more well-documente REW

Equipment List:
Kenwood DMX1037s
Helix DSP Pro Mk2
2 JL Audio HD900/5
Audiofrog G60S components (passive crossovers removed) with GS25's in the front 3-way
JL Audio C5-650 in the rear (passive)
2 JL Audio 10tw3d4's in a ported box

Some really good information to read is Audiofrog Andy's Tuning Guide:
https://testgear.audiofrog.com/wp-c...Process-and-Some-Notes-About-Why-it-Works.pdf

One of the first things that i needed to do before even touching the tune, was to establish the crossover for each speaker. This is important to setup in the Helix because if you send an 80hz signal to your tweeter, you are going to have a very bad day. After doing some research and looking at the spec sheets for my speakers, here's the baseline i started with (ended up being changed as i tested the stereo):

Sub Subsonic: 0
Sub Lowpass: 80
Midbass Highpass: 80
Midbass Lowpass: 350
Midrange Highpass: 350
Midrange Lowpass: 3500
Tweeter Highpass: 3500

These will all be using a 24db/octive Linkwitz-Reiley

Once this is done, then the stereo should be safe to play music through. The next thing would be to set your time alignment. This is straightforward just using a tape measure to go from the center of each speaker to the point where your ears are. Helix does have a cool feature where it will automatically set your time alignment, but i had a hard time getting it to work, so i did it with a tape measure.


Next step is to establish a house curve/target curve to be able to tune to. I used Justin Jazzi's Companion to establish a target curve:
https://www.caraudiojunkies.com/sho...s-tuning-companion-for-room-eq-wizard&p=60209
This was a really cool tool, you plug in all your parameters and it gives you multiple target curves (the yellow line). I ended up choosing the JBL Andy Option as i thought it would fit my listening style.

When you click "Export Text Files", it sends a text file for each of 5 curves.

Next we need to fire up REW. First thing would be to download your calibration file for your microphone. For the UMIK-1, you go to the Minidsp website and plug in the serial number of your mic and it downloads 2 files: a standard and a 90deg calibration. We will be using the 90deg since the mic will be pointing up.
If you have the mic plugged into your laptop before you fire up REW you will be asked for the calibration file, if not go to Preferences ->Mic/Meter and load the calibration file.
To load in your target curves, go to File->Import->Import Frequency Response
Do this for each of the 5 text files (if you are running 2-way active, it would be 4 files)


Figure out a way to place your microphone in the position where your head will be



Now its time to start the tuning process. I used bluetooth to go from my laptop to my head unit. In REW at the top there is a sound generator. Click on Generator and select Pink PN (periodic).


Start off by isolating one speaker at a time. I started with the Rt Tweeter. On the Helix you can mute individual output channels on the right side of the main page:


Before you open the RTA screen, you must select your curve on the left of the REW (Tweet in this case) and then click the gear icon on the top right and select Tweet from the drop down list. We will use this to vertically shift the target curve up or down to line up with the measurement (using the "Offset (db)" field).


Open the RTA window and you should see your Tweet curve. You want to set your axis so that there is a 5db change in the vertical and so you can see the extent of your curve on the horizontal. You can zoom in/out to adjust and the sliders to move the view.
Hit the gear icon on the top right and use these settings:


Start playing your Pink PN noise and adjust the volume so that it eliminates the noise floor (maybe around 70db). Your target curve will be default with a 0db offset, so go back to the main REW window and add or substract some values in your Offset (db) till the curve lines up with your measurement.
Now the actually tuning starts. Go through and adjust the bars at the bottom of the Helix Main page to move your measurement curve on top of the target:



Now you may have a hard time getting it to fit just right, on a 1/6 octive, you wont be able to get it just perfect without spending a lot of time adjusting (i ended up smoothing out the peak 18khz)
Note: after each change on the helix, you need to click the "Reset Averaging" at the top of the RTA window to see the change you made on the graph.
Click Save if you want a copy of the graph and close the rta window when you feel good about the curve.
Now its basically rinse and repeat with all the other speakers.


Here's what i ended up with for all the speakers playing at once. This was one of my first go's so dont judge, it got much better as i changed things and re-tuned. There was a nasty dip from the 60-90hz range and the tweeters were a little too high.

Note: if you dont want to see the bar graph style line, you can apply smoothing in the Gear Icon window (this is 1/6 Smoothing).


I ended up talking with @Vector W8 through this entire process and showing him graphs we (i mean he) came up with some good ideas to adjust the crossovers to fill in the gaps and push higher notes to the 2.5" and 1" speakers

I changed the crossovers to:
Sub Subsonic: 0
Sub Lowpass: 95
Midbass Highpass: 80
Midbass Lowpass: 550
Midrange Highpass: 550
Midrange Lowpass: 5500
Tweeter Highpass: 5500

I went ahead and redid all the tune and got a respectable graph. Its sitll has a big dip at 60-110 that i'm working on, this can be attributed to the "Nearside Null"
Here's an explanation:
https://www.youtube.com/watch?v=aIAV-jDafq0&ab_channel=Erin'sAudioCorner
I'll be able to remove the dip with some more tweaking
After you have a good tune, then you can adjust the levels for each pair of speakers to hit your curve better.


Thats where it sits right now. It sounds really really good. Its by far the best sounding stereo i've ever had. Big thanks to @Vector W8 for helping me out through the process.

I'll be updating this as things progress...

 

I've created a post about setting your gains with an oscilliscope. In reality, this should be done before you tune everything.

https://www.tundras.com/threads/using-an-oscilloscope-to-set-your-gains-for-around-50.96649/

 

Reserved also

 

Solid work,

 

Awesome write up. You are making me want to do another stereo upgrade. New headunit will be next to get rid of the last of the tundra JBL. I had contemplated added a 2nd JL rd400x4 to go active on the fronts and to power the dash tweeters.

 

Thanks!

Do it! You'll be amazed with how much better is sounds!

 

Wow good stuff. I think this is where I need to go next to get everything just right.

 

Nice write up to take your system to the next level.

 

Did you try Helix's auto tune?

 

Not really, i tried it once briefly, but it was doing some strange stuff so i stopped....didn't want to cook a speaker.
I couldn't really find much documentation on it.

I may give it a try at some point and load it on the other preset.

 

how are the audiofrog GS speakers?

 

So these are the g60s component speakers, not the gs line of singles.
They sound great. Very warm sound to them.

 

Apicella Auto Sound on youtube had a nice how to video but I don't see it any longer.

 

Yep, he pulled it down. Apparently he didn't like the image it was giving his business so he pulled a lot of his videos, i think he said he's going to re-do a lot of them but who knows when.

 

hmm. you're making me want to re-tune mine... nice job.

 

DO IT!
You are running a fix and twk right?

 

yep. i've been learning a lot of audio stuff lately with some of the production work i've been doing. almost all of it translates from my studio space to the truck. a calibrated mic has been on my list anyway as i need one to properly set up my studio monitors.

i just need to carve out a few hours to do this. i'll be coming back to this thread shortly.

 

Keep us posted!

 

umik-2 will be here on monday

 

Awesome! i almost bought that one instead of the 1, but i went cheap.

 

Nice job. Will be coming back to this thread when the time comes. I m betting that is a windows laptop.

 

REW runs on OS X too

 

My laptop came with linux, and my windows cd doesn t like something about it. I ll just buy a cheap laptop when I m ready to tune.

 

I use smaart v8 from rational acoustic. Nice damn write up btw

 

from the rew manual...



looks like you're good to go

 

The permissions line is interesting. chmod 775 seems safer.

 

Updated Post #2 with a guide to setting your gains with an oscilloscope.