MMM vs Sweep (REW) of my JBL e80 towers

[Deleted member 17820]

Hi friends, so thanks to the people here I found out about the MMM measurment method. For me this makes the most sense for what i am doing.
I just recently replaced both tweeters in some old (mid?) school JBl towers I picked up a while ago.
After taking many measurements it turns out the MMM did a very good job of showing what all the other sweeps showed.
I heard the MMM method was called a spacial average and that is what I found it to be.
Here is an on axis sweep, 1m, compared to the MMM at same distance.

The highlight red is on axis MMM and......blueish is a sweep. Both measurements are smoothed to 1/12th, no gating.

I have spent the last 3 months trying to find an acoustic material that I could stand the smell of (settled on melamine foam of polyseter) and I wonder which method would be best to measure the benifits of panels and diffusion.

 

[ernestcarl]

Hi friends, so thanks to the people here I found out about the MMM measurment method. For me this makes the most sense for what i am doing.
I just recently replaced both tweeters in some old (mid?) school JBl towers I picked up a while ago.
After taking many measurements it turns out the MMM did a very good job of showing what all the other sweeps showed.
I heard the MMM method was called a spacial average and that is what I found it to be.
Here is an on axis sweep, 1m, compared to the MMM at same distance.

View attachment 89122

The highlight red is on axis MMM and......blueish is a sweep. Both measurements are smoothed to 1/12th, no gating.

I have spent the last 3 months trying to find an acoustic material that I could stand the smell of (settled on melamine foam of polyseter) and I wonder which method would be best to measure the benifits of panels and diffusion.

I’d just like to point out that MMM is just one kind of spatial averaging. It has some disadvantages like not preserving the phase and being able to show the impulse... so ideally you should still take some single-point measurements as well.

Can’t really comment on which acoustic material is best though.

 

[Deleted member 17820]

I feel that what miniDSP, REW, and of course ASR are doing is democratizing and making things like DSP more accessable and understandable to the general public.

There is a catch 22 in this whole deal.
Should I REALLY be making measurments and using DSP?
I should go to school, learn physics, electronics, etc, get experience then do measurements and DSP adjustment.

THE problem is I can't spend anymore time or money on college ($$$$$$$) and I can't pay a a PRO to come do it, nore do I want to.

I enjoy taking things apart and learning about them, I enjoy trying to learn something new. It only makes sense that many people will make invalid measurements while stepping into this field without enough education to get things right the first time.
That's why ASR is so great. It's obvious with AMIR's gear and measurments he cares about validity but I also see that people here are willing to give grace to people like me who are on an journey of trying to figue out just enough to enjoy the results.

This is where I see MMM as great value, especially for larger theaters or rooms like small churches. I know there are other forms of spacial averaging. My buddy who is an AES member has a multi-mic array set up for larger rooms. He has a mic-box with thousands of dollars of measument mics for his array that uses a program that is also very exensive to do real time spatial averaging, etc.

I have also done sweeps in small churches and it took HOURS to get a spatial average without an array. For simple room correction/dsp in rooms with large listening area I will be using the MMM method from now on. For my desktop set up I just bought miniDSP ddrc-24 so I'l let their computer and program do the work for me .

Here is the comparrison of
MMM
vs Sweeps Averaged
On axis...10 degree horizontal...20 degree Horizontal... 30 degree horizontal... 10 Degree above vertical

 

[Jdunk54nl]

I use a single point sweep for impulse response, phase, decay, waterall, etc. from the "ideal" position.

But for EQ'ing and seeing what the room is actually responding like, I attach my microphone to a boom pole and stand as far away as possible (A paint roller extension or broom handle work well too, you just can't get as far away) and move it throughout the listening positions and then EQ based on all of that data.

It helps to use Pink Periodic noise (I generate it via REW or output a file if I can't plug my laptop in to send the signal) and make sure to set the RTA window to the same FFT length and rectangular if you do this.

I found my EQ'ing when doing the MMM method I like more than doing EQ with spatial average of sweeps. I am assuming because I take into a lot more of the "space" that I am constantly moving between and not just the "ideal" positions for however many sweeps I would do for spatial averaging with sweeps. It also takes less time to do the MMM as you've stated.


On that note, minidsp and REW just updated to support multiple microphones and the multi mic setup from minidsp is $550 for 8 or $750 for 16 and includes the pro license in REW.

https://www.minidsp.com/products/acoustic-measurement/umik-x-multichannel-mic

 

[Jdunk54nl]

As far as measuring panels, I would probably do sweeps that way it highlights any frequency issues (panel resonances) the best since each tone is played "individually". You will also be able to get the other information that is needed like waterfalls and rt stuff.

 

[Deleted member 17820]

I use a single point sweep for impulse response, phase, decay, waterall, etc. from the "ideal" position.

But for EQ'ing and seeing what the room is actually responding like, I attach my microphone to a boom pole and stand as far away as possible (A paint roller extension or broom handle work well too, you just can't get as far away) and move it throughout the listening positions and then EQ based on all of that data.

It helps to use Pink Periodic noise (I generate it via REW or output a file if I can't plug my laptop in to send the signal) and make sure to set the RTA window to the same FFT length and rectangular if you do this.

I found my EQ'ing when doing the MMM method I like more than doing EQ with spatial average of sweeps. I am assuming because I take into a lot more of the "space" that I am constantly moving between and not just the "ideal" positions for however many sweeps I would do for spatial averaging with sweeps. It also takes less time to do the MMM as you've stated.


On that note, minidsp and REW just updated to support multiple microphones and the multi mic setup from minidsp is $550 for 8 or $750 for 16 and includes the pro license in REW.

https://www.minidsp.com/products/acoustic-measurement/umik-x-multichannel-mic

Cool. when I build out my living room/theater/2 channel room I will use single sweeps to measure RT60 and decay, etc.
But to check the EQ settings for my reciever/etc I will defintiyl use the MMM to double check that whatever room correction software is doing things right.

I plan on building some of those arquen step diffusors.