12 Jul

Speaker manufacturers are always talking about how "flat" their studio monitors are as if it’s the one key specification that is going to swing the votes in their direction. By "Flat" they are saying there is a minimal shift in DB along the frequency spectrum from very low to high frequencies.

Why is this important?

The theory goes that if you mix on a set of speakers that have a "flat" frequency response your mix will translate well on other speakers because you are not compensating for bumps and dips in the frequency spectrum of the particular speaker you are working on. E.g. If you imagine a speaker has a 6db bump at 100 Hz you will most likely be pulling that frequency back in the mix to make the mix tonally balanced. You can see the problem. So fair enough – everyone is looking for the flattest speaker they can find.

Now here is the dilemma - if all these speaker manufactures claim to have a flat frequency response, then why do they all sound so different?

As much as speaker manufacturers strive for that elusive "flat" response, it's an ideal that is never really quite fulfilled. Some do a better job than others but no speaker is completely flat. Further to this, and more importantly, no speaker will sound flat in an acoustically imperfect room. All speakers will reactive differently to the room they are in because the room is reflecting frequencies back in random ways. Not only do all speakers sound different in a particular room, that same speaker will sound different in different rooms. So the room has a lot to say about how you hear music.

So knowing that even the flattest speakers won’t really be completely flat, studio owners, engineers and bedroom producers will spend thousands of dollars trying to correct their room with acoustic treatment. They may even employ the best acousticians and buy the best materials to correct the problem only to leave it all behind when they have to move. Further to this, the acoustic room correction often takes place without the selected speakers in the space. So if all speakers react differently, making acoustic treatment decisions in this scenario can only be an educated guess. Don’t get me wrong, I think room treatment is important but unfortunately, it only treats the room as best it can based on that space.

Room Calibration

Another way to eliminate the room from your mix is to use room correction software.

There are a couple of companies that make room calibration software which has been quite popular, especially for small project and bedroom producers. The two that spring to mind are IK Multimedia with their ARC system and more recently Sonarworks with Speaker Calibration. Both these systems use a reference microphone to listen to an audio sweep from your speakers in your room and make calculated adjustments to correct any room anomalies with a plugin that sits on your master bus. Both these systems work – they really do pull any adverse reflections into line giving your speakers a “flat” response.

As much as these systems work, they fall short in a couple of key areas. Firstly having to install a plugin on the master bus for every session you're working on could get tedious. You also have to remember to deactivate the plugin when you bounce to disk otherwise your bounce will include the eq correction - not great! Lastly, if you are just listening to music, testing your mix or other mixed tunes, your room will still be affecting the frequency response because you are not listening back through the plugin in your DAW. Essentially the room is still affecting the sound coming from the speakers.

Enter GLM


Genelec Sam Compact


GENELEC GLM SETUP .Finnish studio monitor manufacturer Genelec has a unique approach to this problem and they are the only company currently using this method. They have built DSP directly into their SAM (Smart Active Monitors) speaker range and use their proprietary GLM room correction software to alter that DSP. The adjustments you make are automatically sent to and stored on the physical speakers. This means that the speakers are always acoustically tuned to your room – they will always be “flat”. Better still if you move or take your speakers to another space you can just do another calibration and send that to your speakers. You can have many different calibrations in software and you just choose which room you are working in. GLM goes even further and will manage up to 30 speakers in one room – setting up and calibrating a 7.1 surround system is a breeze. It will time align all speakers depending on the distance from your listening position and adjust all speakers frequencies independent of each other. The GLM software will pump out all the frequency data and if you think you want a little more level at 100 Hz then you can manually override just that band.

For me, this just seems to be the most intuitive, effective way to achieve a flat frequency response. Sure Genelec continue to manufacture their non-DSP speakers for people who want them, they are cheaper and still very popular but for Genelec, I believe the future is in their SAM range – it just makes sense.

Genelec GLM KIT

The GLM Kit comprises of GLM 2 Software, a reference microphone, and a network hub. USB talks to your computer and Ethernet talks to the speakers. You can keep the HUB connected and push different calibrations to the speakers at any time, or even bypass the correction if you choose. Or if you are happy with the sound just unplug all the cables and put everything away as the speakers will remember the last setting you sent to them.

The GLM Kit is sold separately to all SAM speakers, as you will only need one kit no matter how many speakers you own. You may have 3 studios all fitted with SAM speakers but you only need one GLM Kit to calibrate them.

You can only use GLM on the Genelec SAM range. Studio Connections have a selected GLM dealer network. CLICK HERE to see our dealers and hit them up for a demonstration.

I’ve only touched on what SAM AutoCal can do – if you would like to get the full story CLICK HERE

Here's a Video describing GLM SAM


  1. That sounds like it’s just adjusting some eq settings in the speakers. I think everybody who haves some experience with room acoustics knows that is the last thing you want to do. Eqing the problems of the frequency response will work visually but it will leave phasing issues. Using acoustic treatment is mainly used for fixing a to long decay/room reverb. Which is just as or maybe even more important then a good frequency response. Thinking you don’t need acoustic treatment with this speakers couldn’t be farther from the truth.

    matthijs October 5, 2017
    1. Also, this integrated in the speakers is not ideal at all. having this on the masterbus might work just because you can turn it off. Not having this option leaves you with the question if something is phasing in the mix or if its a artifact of the room vs master eq.

      matthijs October 5, 2017
      1. Genelec GLM room correction can always be turned off – it’s just convenient to store the settings into the speakers because once you have it calibration done you typically don’t want to alter this. However I have a customer who likes to A/B between calibrated and non calibrated. He does this by hitting the bypass button on the GLM software. Not only can he switch between bypassed and not, he can also have many different calibrations for different positions in the room. One for the engineer seating in the ideal location and one for the client sitting in a couch at the back of the room.

        Paul Newcomb October 9, 2017
    2. Hi Matthijs.

      Thanks for taking the time to read our article. We believe that a combination of acoustic treatment and speaker calibration is the ideal solution. You are correct in saying that EQ can introduce phase however the filters used by Genelec in this instance are phase coherent between both speakers and never cause an issue. We suggest that room treatment be used for high frequency absorption leaving GLM to take care of the harder to treat mid to low frequencies. A combination will render the ideal result.

      Paul Newcomb October 9, 2017
  2. I love the frequency chart display after a measurement. My last room retune involved moving things around my room about 50 times and doing a measurement each time and settling on the room configuration with the most level frequency result and then GLM obviously does the smallest amount of correction.

    scott stevenson February 21, 2018

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