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Genelec GLM Review (Room EQ & Setup)

amirm

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This is a review and detailed measurements of the Genelec GLM "SAM Loudspeaker Management System." Its main use is automatic and manual room equalization for select Genelec speakers with such support. It is on kind loan from a member and costs US $299.

I was pleased to see it come with a nice looking microphone and an audio interface:

Genelec GLM Review Speaker Management System Room EQ Parametric.jpg


At first I thought the communication was through Ethernet so plugged in the speaker into my home network but nothing happened. Then I read the manual. :) I realized that the RJ-45 is a custom connection and protocol for the above adapter to talk to speakers in a daisy chain manner. Once I plugged the speaker into it, the GLM software recognized it and I was able to configure it. FYI the version I tested is the 4.1.

The interface is a bit tricky in that you have to drag and drop the speaker onto this unusual grid to then group speakers and manage them:

Genelec GLM Equalization UI SPL Meter Measurements.png


Post calibration to see how the filters are setup, you need to click on the Genelec speaker icon in that grid which was not easily discoverable. I found it by accident.

For testing, I used the Genelec 8330A which I had recently reviewed. The process could not be simpler. You tell it to start calibrating and next thing you know, this super loud chirp signal plays and that is that. No multiple measurements. No averaging. I would have wanted some control over volume on this but I did not realize the role of the vertical slider until later. The good news is that the whole affair was done in just a few seconds. Compare this to automated Room EQ on AV products that can be very time consuming with multiple measurements and such.

Before I show you the measurements, I really appreciated a couple of other cool features. First, you can calibrate the SPL level where you sit with the microphone. Once there, you can then leave the microphone there and watch the real time SPL values shown at the bottom level ("77" in this snapshot). I was able to go into low 90s before the speaker clipped with the speaker icon turning red above that. With all other systems, once you are done calibrating, the mic and software collect dust. Nice to see that is not the case here especially if the displayed SPL values are correct.

You can also preprogram a couple of SPL values as you see on the left. Once again, I could not discover how to change them. There are presets for the system/speaker but I could not figure out how to edit them.

The whole interface is very responsive which makes the included volume control slider useful.

Gelenec GLM Room EQ
The main event here is how well the automated GLM calibration performs. Per above, post correction you can examine what it did and thereby also understand its underlying technology:
Genelec GLM Equalization Measurements.png


I truncated the above display as it goes to 16 filters. The system is not different than automated filter creation in Room EQ. The system is simply using a combination of shelving and parametric EQ to build an inverse of the response with some care. For example, the sharp dip around 80 Hz which is caused by cancellation, is left alone sans a constant boost provided by the shelving filter. On the other hand, the peak at 200 Hz is attacked strongly with a complex curve created out of a nearly a dozen filters to invert it. The filter response is in blue and the measurement is in red. Filter applied to measurements is the green.

From what I can tell, it didn't attempt to make any correction above 300 Hz which is fine but then there is a lonely filter at 818 Hz with just a -0.3 dB gain. Such a filter will not have an audible effect. I wonder if it is using the knowledge of the speaker to make a tiny correction there?

Sadly as with all of its competitors sans JBL ARCOS, the corrected response is a simulation. No post calibration measurement is performed to see if that is the results that is generated. That is left to us to mess around with another microphone and measurements software to use. Problem with this type of verification is that the microphones will be different as will the absolute positions so we can't do a precise determination. But we can get close.

I used my Earthworks measurement mic with my RME Babyface Pro FS in combination with REW software to make a before and after measurement. I used 1/12 octave smoothing to keep detail there but soften the results some so we can make sense out of it:

Genelec GLM REW Equalization Measurements.png


Please ignore the levels. They are not calibrated.

The graph in red is the measurement prior to calibration. We see the standard impact of the room causing similar dual peaks around 55 and 180 Hz as GLM software showed. There is also the same dip at 100 Hz or so. We have a peak between 400 and 500 Hz that was not in the GLM measurement but this may be due to me not matching the mic location.

It is interesting that the correction for the first peak around 55 Hz is almost not there and much less so than predicted by GLM software. I can't explain this other than the filter implementation not having the resolution it thinks it has. Maybe the Q should have been lower.

On the other hand, the second peak around 180 Hz is corrected well with a response that actually matches the peak for the 55 Hz one.

Genelec GLM Room EQ Listening Tests
Turning the calibration button on and off is very fast allowing for quick AB comparison and boy is this a stark comparison (as it usually is with Room EQ). Turning on the EQ instantly removed some amount of low frequency boominess but importantly, it brought the vocals forward which I really, really liked. Once you listened to the calibrated sound, you just did not want to go back to not having it.

One of the key benefits of the GML is that you have full visibility into all the filters and you can add your own and turn them on and off and see which version you like better. So I added a filter at 449 Hz to fix the third peak with a Q of 5 and gain of -3 dB. This was a subtle change but it brought even more clarity to vocals. What I was hearing then was stunning! The vocals in one of my reference and favorite tracks, Biscuits from the live album by Fink had a realism and fidelity that was just a joy to listen to:


There, I did the obligatory thing of putting in some music in a review! :) But really, it was just wonderful and showed how good these Genelec speakers are when you take out the impact of the room.

Note that the overall signature was somewhat bright as is typically the case when you take out the excess bass. Genelec provides dual shelving filter overrides to boost the lows and reduces the highs. This is limited 3 dB max correction however. I found the effect subtle even at maximum correction and wanted to have more room for adjustment.

Conclusions
The Genelec GML Room EQ is a straightforward automatic generation and execution of filters. This makes the system easy to understand and modify but perhaps takes out the mystique of something magical going on. I personally may take a shot at just programming the filters manually or measuring and then modifying. While I have accepted the fact that consumer EQ products don't want to provide transparency on what they have done, I wish a Pro product like GLM would make a post EQ measurement and show that rather than simulated, feel good but made up response. It would take just a few seconds. Heck, that measurement could be used iteratively to optimize the filters more.

As is though, the system provides 90% of what an expert could do on his own in almost an instant. The improvement is dramatic and you would be silly for not using it if you have a Genelec SAM speaker. Indeed any system used without an EQ is producing incorrect and far less than satisfying sound in your room. You must have an EQ strategy and if you can't provide it upstream, having it this easily programmed into each speaker is a great help for very little money.

Overall, I am going to recommend the Genelec GLM. It should be mandatory for anyone buying a SAM speaker that works with it.

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As always, questions, comments, recommendations, etc. are welcome.

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HiFidFan

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I've been waiting anxiously for your take on GLM. Thanks @amirm
 

q3cpma

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Did you place the measurement mic at the exact same place as the GLM one? I mean, I suppose you did, but that could explain the 55 Hz thing.
Nice to see that this positive gain filter did narrow that big dip a bit.
 
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amirm

amirm

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Audioholics recently did a live stream with Audyssey, and the representative stated that simulated responses are very close to actual as they know the limitations of the hardware.
I tested Audyssey years ago and that was not remotely the case.
 

mitchco

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No offence to you @amirm, fine review. But I don't get it. How is this room eq? I would expect something more like this:

Wilson Audio Alexia Series 2 before and after DSP room correction.jpg


This is what one should expect from "state of the art room" eq. As I have shown in multiple posts on ASR, it is not just at one listening point either...

There is a big difference between PEQ and room eq that is based on high resolution FIR filtering. I would be happy to prepare some FIR filters for you if you send me some REW measurements.

Kind regards,
Mitch
 
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amirm

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Of course it is room eq. It measures speaker in the room and corrects for bass response. What else you call it?
 

HiFidFan

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Well, it seems that not giving the golfing panther is justified. But doesn't miss the mark by much IMO.

As a software simpleton, if GLM can get me 90% there with a relatively quick and easy process, I'm in. Now all I need are those 8330's.
 
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amirm

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This is what one should expect from "state of the art room" eq. As I have shown in multiple posts on ASR, it is not just at one listening point either...
For 2 channel listening we don't need wide coverage. I also don't see how you get that flat response without throwing out 20 db of headroom and making questionable corrections above transition frequencies.
 

Sancus

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GLM is also restricted by the fact it can't add more than a couple ms of latency, or the monitors become unusable for eg overdubbing or live playback of digital instruments etc. In fact even with GLM on, Genelecs typically have no more than 3-4ms. Which is why the new phase linearization to 100hz on the Ones is optional as it adds 4ms.

As far as I know even Dirac adds considerably more than this.
 

Somafunk

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Good review and setup of the GLM software by Warren Huart below using his 8351B monitors

 

mitchco

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For 2 channel listening we don't need wide coverage. I also don't see how you get that flat response without throwing out 20 db of headroom and making questionable corrections above transition frequencies.

This is a misunderstanding of what DRC/DSP FIR filtering products actually does... There is indeed filter insertion loss as there is no boosting, but it is typically 5 to 7 dB of loss. But can easily be recovered by adding some digital gain. It is a completely different paradigm than PEQ.

I also think there is a misunderstanding about eq'ing just to the transition frequency. Sounds waves don't just turn into rays above the transition frequency. It is a gradual transition as illustrated in this chart:

controllers of steady state acosutic room response.png


The art in applying DRC is to use a frequency dependent window so that normal modes are getting the full correction, but above the transition frequency, the correction becomes less and less so by the time you get through the diffusion zone (4fc) no more correction is being applied (or if any, it is to the direct sound only and not including any room reflections). Typically that is around 600 Hz in most rooms. I offer my clients partial and full range correction and they can decide which they like better. The results of which on what most people prefer are overwhelmingly in one direction.

Sorry, I did no mean to barge into your review. Just wanted to make you and your readers aware that there are DRC/DSP products that can offer a much higher resolution room eq than just PEQ. My offer still stands on producing some high resolution (partial correction) FIR filters for you to listen, measure and compare.
 

Xulonn

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Good review and setup of the GLM software by Warren Huart below using his 8351B monitors

Warren seems to agree with Amir - he says "there's a huge difference in the vocals".
 

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amirm

amirm

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The art in applying DRC is to use a frequency dependent window so that normal modes are getting the full correction, but above the transition frequency, the correction becomes less and less so by the time you get through the diffusion zone (4fc) no more correction is being applied (or if any, it is to the direct sound only and not including any room reflections). Typically that is around 600 Hz in most rooms.
I am well aware of this as I said "transition frequencies." Plural. That does not change the nature of the task. Tiny corrections through FIR filter or PEQ makes little to no audible difference and even when audible, a listener needs to apply judgement to them. With PEQ like solutions like GLM, it is dead simple to turn the correction filter on and off and judge the results blind or otherwise. Convolution type filters tend to be all or nothing as far as UI, and also very slow to change depending on system making such comparisons very difficult if not impossible.

As a general rule, superbly built speakers are of no need of correction in higher frequencies other than overlaying a target curve which should to be taste.
 
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