Alesis M1 Active Speaker Measurements

[LevityProject]

I've had this pair of Alesis M1 Actives for a while, but stopped using them because I just didn't like how they sounded and even using Sonarworks Sound ID couldn't save them. I wanted to see what exactly was happening with them, so I used REW to finally see what's happening under their hood. I thought I'd post some measurements and corrective EQ for discussion. Does anyone else have a pair of these?

For reference, this is what I'm attempting to recreate (the blue/green graph). Essentially, I want a nice HF roll off and a tight response above 1khz.

Here is the frequency response measurement of my Alesis M1 Actives, with the target curve overlayed.

Yuck! No wonder I stopped using these. They are ... bad in all the right places. Hyped low mids, and guess where the cross over is? the trough between 2-3k is a dead giveaway.

This is the frequency response graph from the user manual.

They look flat here to within 2-3db ... what's going on? Are my measurements bad? Maybe, but what I hear in the speakers correlates with what the measurements are telling me. The measurements from the manual show a more or less flat response, but that's not the reality in practise. Perhaps it is the room causing havoc or perhaps these speakers aren't all that flat.

Regardless, the measurement graph from the manual is seems to not be helpful for any practical purposes.

Here are some distortion measurements. I have no idea what REW does to come up with these numbers, but I'm curious as they don't look great. I can't hear the distortion in practical use, but this does raise more questions about the engineering of these (as the review I had originally read from SOS said, "neutrally smooth") monitors ... :/

It seems there is a pretty significant distortion issue below 100hz. With 56hz distortion topping at nearly 70db SPL on 100db of signal, that doesn't seem acceptable. This is especially considering I wasn't even driving the speakers to their full volume during the frequency sweep in order to minimize room resonance and reflections. However, since I can't hear the distortion in practical use, for now I'm not concerned as my listening volume is usually pretty low (gotta save my ears for the future!)

Next, I did some work with REW's EQ module. Anything I did below 250hz or so is going to be a correction of my room more than it is of the speaker itself. There's also a room mode at 45hz in my room, so I had to tame that down in the Eq settings to below "flat" as I could hear that resonance. The result is a bit of a compromise between. wanting to hear that satisfyingly low bass and not wanting too much resonant woof.

This is the resulting corrected Curve.

This is where the rubber hits the road ...

Listening Tests
I exported the EQ adjustments as a text file (attached) and loaded that into SoundSource.

WOW! These speakers are significantly transformed. They still are pretty far from perfect for my liking, but what a difference it made to spend the time to measure them and adjust some EQ! They now have nicely powerful bass all the way down to 40hz and clarity and sparkle is significantly improved.

After all of this, and as wowed as I was with the transformation, I'm now totally convinced that I need to get much better monitors. Before now, I just had some vague idea that these monitors sounded off, and correcting them with Sonarworks made them sound too narrow and lifeless. I haven't used them in almost a full year. Seeing and playing with this data has shown me clearly that what I was hearing was at least accurate. These monitors by themselves sound unacceptably bad and need careful correction in order to sound even half decent. Having said that, with unlimited DSP bands, it could be possible to further transform these. Their reach down to 40hz is impressive given that they are pretty small monitors.

Questions, comments, corrections are welcome

 

[staticV3]

This is the frequency response graph from the user manual.

They look flat here ... what's going on? Are my measurements bad? Hardly ... What they seem to have done is zoomed out the graph to elongate it, and applied 1/6th octave smoothing. I can do that too with my measurements to make them look pretty and flat. For anyone who doesn't believe this is what's happening, I did it and it was easy. I just zoomed the graph out and voila.

Now look at the actual dB ranges of each graph and realize that that's not what's going on here.

1/6 Oct smoothing is also unlikely given the low frequency resolution present in Alesis' graph.

More likely, it's just the difference between nearfield, on-axis, anechoic measurements and your in-room response measurements at the MLP.

 

[LevityProject]

Good point on the db range. I've updated the post to show similar dB range in the measured response (110 to 70db). The speaker's response from the manual is still not what it sounds like, and that part was what got my attention. It could be the room, but even at low listening levels, the profile is the same. Oddly boomy, muddy and kind of harsh. It's anything but neutral from what I can hear and now see ...

 

[Jim Taylor]

It could be the room ...

I would guess that you already have this information, but if not, these may be of value to you:

Reverberation Time in Room Acoustics

Need to measure reverberation time with your sound level meter? Common room acoustics measurements of RT60, T30, T20 explained.

www.larsondavis.com

amroc - THE Room Mode Calculator

HTML5 room mode calculator. Read and hear the tune of axial, tangential and oblique modes. Scientific sources included.

amcoustics.com

RT60 calculator Wallace C. Sabine calculation reverb time reverberation time Sabin Sanine's formula online sound pressure sound level - sengpielaudio Sengpiel Berlin

RT60 calculation Wallace C. Sabine reverb time reverberation Sabin Sanine's formula online sound pressure sound level - Eberhard Sengpiel sengpielaudio

sengpielaudio.com

Jim

 

[LevityProject]

I would guess that you already have this information, but if not, these may be of value to you:

Reverberation Time in Room Acoustics

Need to measure reverberation time with your sound level meter? Common room acoustics measurements of RT60, T30, T20 explained.

www.larsondavis.com

amroc - THE Room Mode Calculator

HTML5 room mode calculator. Read and hear the tune of axial, tangential and oblique modes. Scientific sources included.

amcoustics.com

RT60 calculator Wallace C. Sabine calculation reverb time reverberation time Sabin Sanine's formula online sound pressure sound level - sengpielaudio Sengpiel Berlin

RT60 calculation Wallace C. Sabine reverb time reverberation Sabin Sanine's formula online sound pressure sound level - Eberhard Sengpiel sengpielaudio

sengpielaudio.com

Jim

Thank you Jim! I've seen several room mode calculators, but the amacoustics one is AWESOME! I have a lot to learn about room acoustics, and I appreciate the resources as I dig around.

 

[sigbergaudio]

Here are some distortion measurements. I have no idea what REW does to come up with these numbers, but I'm curious as they don't look great. I can't hear the distortion in practical use, but this does raise more questions about the engineering of these (as the review I had originally read from SOS said, "neutrally smooth") monitors ... :/

View attachment 395903

It seems there is a pretty significant distortion issue below 100hz. With 56hz distortion topping at nearly 70db SPL on 100db of signal, that doesn't seem acceptable. This is especially considering I wasn't even driving the speakers to their full volume during the frequency sweep in order to minimize room resonance and reflections. However, since I can't hear the distortion in practical use, for now I'm not concerned as my listening volume is usually pretty low (gotta save my ears for the future!)

As your own graph says, the THD is only 1.26% at 56hz, that's more than reasonably, almost unrealistically so. You are probably getting some room gain. 100-70dB = -30dB = ~3% THD. There's nothing wrong with this.

Beyond that, you won't get reliable THD measurements in the listening position, as peaks and dips from the room will affect the measurement and subsequently the calculated THD.

 

[sigbergaudio]

I would also generally advice against using Sonarworks or anything else to force the response of the speaker to a specific target, but that's a whole different subject I guess.

 

[AnalogSteph]

This thread needs a good dose of MMM. Also, measuring distance is kind of important, and accuracy towards the higher frequencies can be improved by windowing appropriately. I've done tweeter measurements with sub-ms window sizes at times. Oh, and it goes without saying that left and right speakers need to be measured separately.

The dip between 2 and 3 kHz is curious indeed, but first you'll have to verify that it is actually the speaker itself doing this and it's not interference from nearby obstacles that's messing you up. Going by distortion, actual crossover seems to be around 3 kHz.

I would also generally advice against using Sonarworks or anything else to force the response of the speaker to a specific target, but that's a whole different subject I guess.

Good point. Indeed, I have noticed that you broadly want to follow what the room is doing (minus peaks and dips) or else the result can sound thin.

 

[sigbergaudio]

Good point. Indeed, I have noticed that you broadly want to follow what the room is doing (minus peaks and dips) or else the result can sound thin.

You don't necessarily want to fix all the peaks and dips either. The higher the frequency, the less likely that is to be succesful.

 

[AnalogSteph]

Indeed, you can really screw up above roughly 1 kHz or so. Omni microphones just don't hear like ears, which is why I like to get them closer than MLP. Appropriate gating + averaging of multiple positions / MMM is definitely advised. EQs may have to be put together for different frequency ranges from multiple measurements.

 

[LevityProject]

Indeed, you can really screw up above roughly 1 kHz or so. Omni microphones just don't hear like ears, which is why I like to get them closer than MLP. Appropriate gating + averaging of multiple positions / MMM is definitely advised. EQs may have to be put together for different frequency ranges from multiple measurements.

I'll have to try the MMM approach when/if I can get my hands on another measurement mic. My behringer EMC bit the dust, so for now I'd be waving a MacBook pro around in a circle lol.

So yeah this test I did here is full of holes and shouldnt be taken as any sort of authoritative result ... But the conversation has been very enriching so I'm thankful for that.

One of my goals was to see if I could get a notably better tone than Sonarworks without buying more gear, and I think I did just that using one measurement from the listening position. This was VERY surprising to me. I thought I would for sure need to take measurements from all over the room to achieve the final tonal balance I got.

What I am theorizing is that this measurement tells me something helpful about the room along with the speakers. The resolution of that information is probably not high, but it might be just enough to make some good decisions. I wouldn't rely on it as a tell all about the speakers or the room individually, that's for sure, but as a listening vehicle I've been liking my M1s again as a result of this little experiment.

 

[holdingpants01]

Keep in mind that if people say "you shouldn't do it", "you'll screw up something", "advice against using something" in the context of room correction, it's not that serious. You wouldn't break anything or hurt yourself and there's still a big enough chance of improving the experience to just try it, you can always turn it off. Also with speakers with wonky frequency response it's hard to make thing worse, I wouldn't correct some higher end stuff above certain range, but I had impressive results with full range correction of just plain bad speakers

 

[czt]

Use REW trace arithmetic 1/|A|, 1/|B| (exclude notches) impulse response min phase version (or |A|/|B| if you want that Bob Katz room target, which will be rather high deficient) with whichever resolution/smoothing and measurement method you want. Optional second impulse: crossover linearization with rePhase.

 

[TheZebraKilledDarwin]

I had worked with these years ago and it's a characteristic of the Alesis M1s (active and passive), that they have low 700 and rise torwards 1200 Hz . This gives a nice overtone rich midrange impression, but it's not that well suited for louder scenes or movies in not extremely dry rooms in general, because you don't want screaming women or crowds, or sirens - you get it - suddenly become 10 dB louder in relationship to normally spoken dialogue, only because of the raised voices.

The theatrical like sound, most suited for movies, you want 1-1.2k to be slightly lower in level than the 500-700 range and not peaking in that range 5-10 dB above the lower midrange. IMO the M1s literally turn this relationship upside down.

What is not widely known, is the fact that room EQ systems in automatic mode do not take relative spectral (im)balances into account and therefore cannot reverse them. They just work torwards the mean, but they cannot turn, for example, the 1200 region into a slight dip in relationship to the 600 range. Therefore they do not really change the tonal characteristics of a setup and its speakers.

So if you want the relationship to be reversed (like a 1.2-1.3 peak turned lower than the 600-700) this has to be done manually. I know about Audyssey that this indeed can be achieved, because it allows to apply hundreds of filters with steep corrections per speaker.

Also make sure, when EQing, that you measure and correct the direct speaker response sufficiently and not mostly the room's impact (measure close enough to the speaker).
And as general rule IME it sounds better, if you do not correct identical speakers L/R differently, but apply the same EQ to all identical speakers (if you have measured enough of their direct sound).

 

[TJT]

I've been sort of a lurker on this forum over the past few years on various topics. Came across this post because I was curious to see if these ever got a review here.

I can attest to the fact that these monitors do not have a very flat frequency response. I used to mix with these for many years and always had to listen to my mixes in different spaces and come back and adjust them afterwards. I'm guessing I bought them originally because they sounded great in the store, but were not very neutral.

I eventually switched to the A7x's, and I set them up right next to the Alesis when I first bought them and A/B'd them side by side. The Alesis are just really mid-forward and lacking in high frequency detail. So, my mixes would often come out opposite: dipped in the mids and boosted a bit in the treble. Mixing bass was also a bit of a problem with these.

With the Adams, I no longer need to listen in different spaces. Much happier with my mixes.

I still have the Alesis set up with some turntables in another room though.

Fwiw.