Understanding the state of the DSP market

[DWPress]

How do you feel about in-room MMM FR measurements? For in-room FR I get results that are consistent and repeatable and they seem to correlate well with what I hear.

For me the in-room measurements that I really struggle to get any kind of confidence in are "timing" measurements taken anywhere but near field.

I always verify with MMM first, instant repeatable results and reliable up to about 700Hz. It's the timing stuff for me that fluctuates and I'd forgotten the Umik1 messed that up but I'll go back to my XLR mic and focusrite next time I'm working on anything in the time domain.

Actually more powerful tools I have at my disposal re DRC/DSP more I am preferring to do as little corrections as possible. Better to under correct than over correct.

I agree completely, when I see tutorials that suggest you force 20-20Kh into a target I cringe feeling empathy for the poor fools trying to follow along a technically frustrating false path. If your room and speakers are ok to begin with just up to Schroeder and only peaks though going a step further with bass alignment is very beneficial.

The topic has strayed into measurements because all of these programs and methods we've been talking about in this thread have measurements in common. Basing any correction on bad data is only going to make things worse and waste time. As has been mentioned - garbage in, garbage out....

I'll start then, necessary bits:

• Measurement microphone - XLR with audio interface better than USB for clocking issues (Umik2 ok)
• Mic stand with boom
• Calibrate your sessions - loopback, always the same SPL in app and on gear
• Turn off ceiling fan, HVAC, fridge - If I leave my ceiling fan on I always have a huge anomaly at 110Hz, at least it's repeatable!

This is what I have done for the last decade the best I can for serious measurements. It's nice to be able to compare graphs from REW to a version from 3 years ago before I updated a driver, repositioned some gear or added some room treatment.

I'm probably missing stuff, what else do any of you do to set up for measurements? Off to digest that FSAF link now.

 

[mcdn]

There are other ways to align speakers/subs or individual drivers, Pat Brown has a set of videos illustrating an alternative approach here.

Oh my god, those videos are just. incredibly good. So well done, clear and concise, I feel like I have learned a huge amount from a single watch-through, and I've been messing with DSP for years.

 

[dualazmak]

There are other ways to align speakers/subs or individual drivers, Pat Brown has a set of videos illustrating an alternative approach here.

Oh my god, those videos are just. incredibly good. So well done, clear and concise, I feel like I have learned a huge amount from a single watch-through, and I've been messing with DSP for years.

I found that the video-illustrated procedures are essentially almost (or exactly?) identical to my primitive procedures which have been done in my PC-DSP-Based multichannel multi-SP-driver multi-amplifier fully active audio rig; I have done it all-over between subwoofers, woofers, midranges, tweeters and super-tweeters.

Spoiler

- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-1_ Precision pulse wave matching method: #493
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-2_ Energy peak matching method: #494
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-3_ Precision single sine wave matching method in 0.1 msec accuracy: #504, #507

- Measurement of transient characteristics of Yamaha 30 cm woofer JA-3058 in sealed cabinet and Yamaha active sub-woofer YST-SW1000: #495, #497, #503, #507

The details of my latest system setup can be found here #931 on my project thread.

 

[LionIT]

How do you feel about in-room MMM FR measurements? For in-room FR I get results that are consistent and repeatable and they seem to correlate well with what I hear.

For me the in-room measurements that I really struggle to get any kind of confidence in are "timing" measurements taken anywhere but near field.

I'm not a fan of mmm honestly.
I prefer to collect N measurements to see the spread, and obviously, get time domain informations.
However, it should correlate quite well with our average perception in space.
From my experience, the pattern and speed of movement are somewhat influential in the result. And the presence of our body can be useful, but also harmful. Also, cable noise can be introduced.
I had seen here on ASR a very informative thread and with various evidence to these effects, but can't find it now...
To capture the response of the system, however, I think it is more than enough.
As I said ... at the end you define the target curve by ear.

 

[Sokel]

I had seen here on ASR a very informative thread and with various evidence to these effects, but can't find it now...

This one?

MMM approach and a new calibration app (magic beans)

I wonder what you guys think of this calibration approach? The app is not yet available for purchase but I was told that it should become available in about a week...

www.audiosciencereview.com

I'm no fun of mmm either, too little info for my taste, nothing technical about my little dislike.
I do use it for sanity but that's it.

 

[LionIT]

This one?

MMM approach and a new calibration app (magic beans)

I wonder what you guys think of this calibration approach? The app is not yet available for purchase but I was told that it should become available in about a week...

www.audiosciencereview.com

I'm no fun of mmm either, too little info for my taste, nothing technical about my little dislike.
I do use it for sanity but that's it.

Seeing it quickly I don't think so...
Anyway, I found again this very informative document on the mmm

 

[gnarly]

Seeing it quickly I don't think so...
Anyway, I found again this very informative document on the mmm

Good paper, thx.

I like how it contrasts the difference in measurements needed for speaker building and room tuning. As both of those tasks surfaced in this thread.

I also like how it went into what's needed to get the variability out of in-room measurements, to be able make spatially valid corrections.

It's very amusing to me, how much debate their is about DACs and amps etc...when their audible effect is so vastly swamped by either room correction,
or lack thereof which i see as its own choice of room correction in the big picture.
The variability in sound, either from no-corrections or from whatever corrections that aren't spatially valid, utterly blows aways the common minutia, ime/imo.
Lack thereof has been my choice so far, using acoustic treatments for room correction......but papers like that get me interested in getting serious with it again.

 

[SimonY]

Just to be extremely clear for anybody who is still not quite sure on this:

If you are working with drive units (your speakers) in a ROOM, the LAST thing to worry about is DSP based room correction.

If you love the sound of your speakers enough to want to correct your room, one could almost guarantee that you’ll love the understanding of what they’re actually doing even more.

Edit: where I have used the term DSP based room correction, what I meant to say is software based auto correction. Apologies

 

[Chr1]

What you are saying seems anything but clear to me unfortunately.

If you are saying that anything but a deep dive into manual room correction is pointless, I suspect that there are a lot of knowledgeable people who would disagree with you.

Granted, automated DRC has to be used carefully. It is not a panacea. But with a bit room treatment and after a bit of experimentation, the improvements I got with MathAudio RoomEQ are night and day.
Plus, as it's free, the only cost was a second hand UMIK-1.
My 2c.

 

[SimonY]

Fair call, got a bit carried away there. Thanks.

 

[Chr1]

No worries. I am kinda watching this thread with a view to doing more of a deep dive myself actually.
However, I am not really prepared to invest huge amounts of time (and possible expense) until I am sure it is actually justified. Diminishing returns and all that.
Holding out til the best route/methodology is a lot more clear cut.

I am currently on the fence re this.
Again, my 2c. YMMV..

 

[LionIT]

Does anyone know if AES-X218 is still in development or has led to some standards?

2013-03-04

AES-X218, Measurement and calibration of sound systems in rooms

To document relevant parameters affecting the audience experience of a sound system in a generalized room, and identify appropriate objective methods of measurements to quantify them. The intent is to identify tools and procedures for a technician to measure the performance of a loudspeaker system in a room, and then support accurate and reliable calibration of this system to a specified performance.

Information Document

Measurement of sound systems in rooms, including but not limited to cinema B-chains, currently relies on empirical measurement techniques developed in the 1970s. Modern methods and equipment should offer simpler and more accurate ways to calibrate rooms with greater precision. This project will review the parameters that affect the audience experience in these rooms, and the objective methods of measurement necessary to quantify them. This will provide a basis for more detailed standardization for measurements and calibration protocols for controllable parameters.

 

[Purité Audio]

Removing what the room is adding ( standing wave/bass boom) is the very first thing you should do and will not harm the SQ, the very opposite.
Keith

 

[Mort]

Just to be extremely clear for anybody who is still not quite sure on this:

If you are working with drive units (your speakers) in a ROOM, the LAST thing to worry about is DSP based room correction.

If you love the sound of your speakers enough to want to correct your room, one could almost guarantee that you’ll love the understanding of what they’re actually doing even more.

This makes no sense. Interested in clarifying?

 

[SimonY]

I guess the point I was trying to make is these days you can know your room dimensions, listening positions, wavelengths, measured driver behaviour, simulated driver behaviour, gain stages, music preferences etc, by doing nothing more than clicking a mouse and using your brain.

Understanding the dispersion characteristics of drive units and acoustic wavelengths in general can only logically result in becoming enthusiastic about acoustic treatment and drive unit placement/arrangment. Swiftly followed by which compromises one is willing to make based on their requirements. All this can be optimised before measuring a single thing.

Measurements begin, filters are applied, results assessed, experiments conducted, training, more mistakes, more learning etc etc. Never ends…

None of the above requires you to hand your room response over to a program for correction.

 

[SimonY]

This makes no sense. Interested in clarifying?

You’re right, sorry.

Where I have used the phrase ‘DSP room correction’ - What I meant was ‘software auto correction’

Apologies.

 

[Robbo99999]

It is easy to take measurements in-room but extremely difficult (bordering on impossible) to get useful and repeatable ones. The problem is all the reflections that the MIC picks up from anything in the room including walls, floor, ceiling, furniture, MIC boom, Mic it's self, as well as the room modes. This make it almost impossible to separate what is the room from what is the speaker. There are "tricks" you can use but they only help a little bit and it depends on the frequency.

Back when I did measurements in room I found it easy but fairly time consuming. I just marked off something like a 2ft or 3ft square spot at my listening position and did something like 9 measurement positions within that square (FL, FC, FR, CL, CC, CR, BL, BC, BR), and then averaged them and that was the measurement that I EQ'd the bass to the Harman Curve as that was my desired curve. When I remeasured after EQ at the same 9 different spots and then averaged them then it was pretty darn spot on to the predicted (with EQ) measurement - so it was certainly repeatable and fairly easy if you know how to use REW. And of course it's best to just use an Anechoic EQ for the rest of the frequency range rather than using in room measurements, so that's why a person has hopefully bought a speaker that Amir has measured. (And again you can use REW to work out the Anechoic EQ required to make it Anechoic Flat). Then you wack in both your room EQ and Anechoic EQ together into your minDSP or whatever you're using, job done. A bit time consuming, but mostly only difficult if you're not familiar with REW or your miniDSP.

EDIT: I remember doing some listening tests with EQ's done from different levels of smoothing of the measurements, and Var Smoothing in REW worked best for me, which essentially doesn't really apply any smoothing to the bass area. The graphs look prettier using say something like 1/12 smoothing, but in listening tests I preferred the fine grained bass EQ of the Var Smoothing option. So the only smoothing done to the bass area was the spatial averaging of the 9 different measurements.

EDIT#2: Oh yeah, and I didn't use any sharp boosting peak filters in the Room EQ (bass) - if I wanted to try to gently boost some dips then I'd apply say +5dB low shelf to the speaker to bring up the dips and then I'd use peak filters to cut down the peaks. This means you end up with "gentle mounds" trying to fill the dips and "sharp cuts" that are removing the peaks. So that's good EQ practice in terms of filters. (You also end up with a bit more low end extension by using that +5dB Low Shelf, which is fine if your speakers don't have big distortion issues and/or you don't listen to your music loud enough to push your speakers to the limit - it worked well with my JBL 308p Mkii speakers when I was using them without a sub - I liked the subtle extra bit of rumble that they produced in movies.)

 

[levimax]

Back when I did measurements in room I found it easy but fairly time consuming. I just marked off something like a 2ft or 3ft square spot at my listening position and did something like 9 measurement positions within that square (FL, FC, FR, CL, CC, CR, BL, BC, BR), and then averaged them and that was the measurement that I EQ'd the bass to the Harman Curve as that was my desired curve. When I remeasured after EQ at the same 9 different spots and then averaged them then it was pretty darn spot on to the predicted (with EQ) measurement - so it was certainly repeatable and fairly easy if you know how to use REW. And of course it's best to just use an Anechoic EQ for the rest of the frequency range rather than using in room measurements, so that's why a person has hopefully bought a speaker that Amir has measured. (And again you can use REW to work out the Anechoic EQ required to make it Anechoic Flat). Then you wack in both your room EQ and Anechoic EQ together into your minDSP or whatever you're using, job done. A bit time consuming, but mostly only difficult if you're not familiar with REW or your miniDSP.

EDIT: I remember doing some listening tests with EQ's done from different levels of smoothing of the measurements, and Var Smoothing in REW worked best for me, which essentially doesn't really apply any smoothing to the bass area. The graphs look prettier using say something like 1/12 smoothing, but in listening tests I preferred the fine grained bass EQ of the Var Smoothing option. So the only smoothing done to the bass area was the spatial averaging of the 9 different measurements.

EDIT#2: Oh yeah, and I didn't use any sharp boosting peak filters in the Room EQ (bass) - if I wanted to try to gently boost some dips then I'd apply say +5dB low shelf to the speaker to bring up the dips and then I'd use peak filters to cut down the peaks. This means you end up with "gentle mounds" trying to fill the dips and "sharp cuts" that are removing the peaks. So that's good EQ practice in terms of filters. (You also end up with a bit more low end extension by using that +5dB Low Shelf, which is fine if your speakers don't have big distortion issues and/or you don't listen to your music loud enough to push your speakers to the limit - it worked well with my JBL 308p Mkii speakers when I was using them without a sub - I liked the subtle extra bit of rumble that they produced in movies.)

If you average multiple measurements or use MMM you can get useful FR information fairly easily and reliably. IMO it is not reliable above Schroeder but it is OK for below Schroeder where the room really messes things up and allows you to make useful adjustments. What I find unreliable is trying to get useful "timing / phase" measurements in-room. Even vector averaging multiple gated measurements yields limited reliable information when it come to "timing / phase". There is just too much going on with sound bouncing around the room in most cases.

 

[dualazmak]

.... multiple measurements or use MMM ....
What I find unreliable is trying to get useful "timing / phase" measurements in-room.

I essentially agree with you, and this is one of the reasons I have applied my own primitive but well validated methods/procedures of in-room "timing/phase" measurements and tunings, as well as assessment of "transient characteristics" of woofers and subwoofers, in my DSP-based multichannel multi-amplifier setup.

Spoiler

- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-1_ Precision pulse wave matching method: #493
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-2_ Energy peak matching method: #494
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-3_ Precision single sine wave matching method in 0.1 msec accuracy: #504, #507

- Measurement of transient characteristics of Yamaha 30 cm woofer JA-3058 in sealed cabinet and Yamaha active sub-woofer YST-SW1000: #495, #497, #503, #507

The details of my latest system setup can be found here #931 on my project thread.

 

[3ll3d00d]

What I find unreliable is trying to get useful "timing / phase" measurements in-room.

Those will (or should) be repeatable in your room (if not, seems like a measurement error) but it depends what unreliable means and also what you were trying to do with that info, eg with subs you just don't need to be super precise so the fact room is messy is not a big issue.