Wanted: Proof of multiple subs and sub EQ

[Ethan Winer]

I even have a scary waterfall for Ethan; fear the waterfall overlay!

LOL, I'm still waiting for an explanation for why my render of your previous data was so different from yours. If you'd like to email me the data file from this latest measuring, I'll be glad to load it into REW and have a look. But please send it to me, not to Jim who runs my business. My email address is here: Ethan Winer Home Page

 

[dallasjustice]

I have no idea Ethan. But they are clearly not the same as mine. Your settings may be normalizing the absolute SPL which would throw the result since the SPL isn't calibrated.

The most recent waterfall and SPL has fully convinced me that the source sink method is superior to any other subwoofer setup I've tried and that I can significantly reduce length mode decay times using this method. The results are stunning and should speak for themselves to any rational person. I'm not a forum debater.

I'm no longer interested in trying to convince you of anything. I'm only interested in learning. If you don't believe me or think I've faked something, feel free to buy a pair of subs and delay and do it yourself.

 

[andyc56]

Andy (andyc56) has posted such a program on AVS but I am not sure how complicated a room it will handle.

Multi-Sub Optimizer (MSO) doesn't actually do room simulation at all. It figures out individual EQ, delay and gain for each subwoofer in order to get the flattest possible low-frequency responses of mains and subs together at multiple seating positions. Its input is a set of text files of frequency-domain low-frequency responses of main speakers and each sub at each listening position. The user performs these measurements using e.g. REW prior to running MSO. For example, if you energize the left and right main speakers together and have four subs, and want to do four seating positions, this would require 20 measurements. These would be mains together, Sub 1, Sub 2, Sub 3 and Sub 4 at each of four listening positions.

If, for example, you did these 20 measurements and let MSO do 1 million iterations to find the best configuration, it would be as if you had done 4 million measurements of mains and subs together (1 million EQ configurations, 4 listening positions) to find the best configuration.

Because it uses individual EQ for each sub, it is able to reduce seat-to-seat response variation, something that can't be done when you EQ all subs together.

 

[DonH56]

Thanks Andy, very good to see you here! Sorry for the brain fart on MSO, working too much and thinking too little lately.

 

[amirm]

Multi-Sub Optimizer (MSO) doesn't actually do room simulation at all. It figures out individual EQ, delay and gain for each subwoofer in order to get the flattest possible low-frequency responses of mains and subs together at multiple seating positions. Its input is a set of text files of frequency-domain low-frequency responses of main speakers and each sub at each listening position. The user performs these measurements using e.g. REW prior to running MSO. For example, if you energize the left and right main speakers together and have four subs, and want to do four seating positions, this would require 20 measurements. These would be mains together, Sub 1, Sub 2, Sub 3 and Sub 4 at each of four listening positions.

If, for example, you did these 20 measurements and let MSO do 1 million iterations to find the best configuration, it would be as if you had done 4 million measurements of mains and subs together (1 million EQ configurations, 4 listening positions) to find the best configuration.

Because it uses individual EQ for each sub, it is able to reduce seat-to-seat response variation, something that can't be done when you EQ all subs together.

Welcome to the forum Andy. I am really interested in your work and have not seen it before. Do you mind creating a new thread and expanding on this?

 

[andyc56]

Welcome to the forum Andy. I am really interested in your work and have not seen it before. Do you mind creating a new thread and expanding on this?

Thank you Amir. I could start another thread, but I'd end up repeating a lot of what I've already written on the MSO web pages. I wrote a tutorial that is about 45 pages long for example.

The main MSO page is here.
The tutorial is here.
The help contents are here.

Reading the first page of the tutorial is a good place to start.

It might make sense to have a Q & A thread or something like that, but I'm not sure what the questions would be.

 

[Ethan Winer]

I have no idea Ethan. But they are clearly not the same as mine. Your settings may be normalizing the absolute SPL which would throw the result since the SPL isn't calibrated.

All I did was load your file and set the display parameters because your waterfalls weren't well presented. I mentioned I'm using REW 5.13 but you never said what version you have. Just to be sure I'm not missing anything I installed the latest 5.15 and got the same results.

The most recent waterfall and SPL has fully convinced me that the source sink method is superior to any other subwoofer setup I've tried and that I can significantly reduce length mode decay times using this method. The results are stunning and should speak for themselves to any rational person. I'm not a forum debater.

I'm no longer interested in trying to convince you of anything. I'm only interested in learning. If you don't believe me or think I've faked something, feel free to buy a pair of subs and delay and do it yourself.

Did I accuse you of faking anything? Aren't you even a little curious why loading the same data file would give such different results? It should be clear from this thread that I started that my only interest is to learn too. You claimed "Okay Ethan I got your proof," and yet when I loaded that same file what I saw was not proof of reduced ringing. This isn't about debating. It's about learning whether multiple subwoofers can actually reduce ringing as some people claim. For a thread that asks questions about audio science, I find your tone and hostile attitude surprising and unfortunate.

--Ethan

 

[amirm]

Michael and Ethan, you are both good people. Please shake hands and let's move on.

 

[dallasjustice]

All I did was load your file and set the display parameters because your waterfalls weren't well presented. I mentioned I'm using REW 5.13 but you never said what version you have. Just to be sure I'm not missing anything I installed the latest 5.15 and got the same results.



Did I accuse you of faking anything? Aren't you even a little curious why loading the same data file would give such different results? It should be clear from this thread that I started that my only interest is to learn too. You claimed "Okay Ethan I got your proof," and yet when I loaded that same file what I saw was not proof of reduced ringing. This isn't about debating. It's about learning whether multiple subwoofers can actually reduce ringing as some people claim. For a thread that asks questions about audio science, I find your tone and hostile attitude surprising and unfortunate.

--Ethan

Ethan,
I have learned a little more about how to setup the source sink setup and I have even better measurements to back that up. If post #300 isn't clear enough for you to see there's reduced ringing, then what can I say? All I did was take two measurements which were level matched and did a waterfall overlay using REW. If you want to teach me why my results are all wrong using REW or that somehow a newer version of REW 5 is different or something, I'm still waiting to hear it. Maybe you don't like how I've scaled things. I've changed nothing in the scales or settings between the two measurement results. I haven't even changed the mic position. I don't want to show multiple mic position measurements, because I don't want to be accused of changing anything between the two measurements. They are exactly the same and all the display settings are the same.

I did send you a nice email several days ago which included a free .pdf of the Fazenda paper which describes in great detail the "source sink" method I've used. (I probably broke some law doing that.) In that paper, Fazenda takes decay measurements as well and subjective testing to determine which subwoofer setups are preferred. If you took the time to read that paper, you'd notice that Fazenda's conclusion supports what you've been saying. In particular, he says that it's really decay times which matter to what listeners prefer more so than just the SPL response. In that email, I also sent you the mdat files from a previous sub setup. If you had a problem with how I scale something or came up with wildly different results, you could have simply emailed me back to sort through it. Instead, you seem determined to ignore clear evidence that your thesis is erroneous. That's fine with me. I'm no "expert" in this field. I'm just a dumb lawyer who wants to have better bass in my listening room. However, I am very confident that you are incorrect about your thesis.
Michael.

 

[Ethan Winer]

Michael, I'm trying hard to follow what you said. You sent me a paper to make a point, but now you say it agrees with me. Actually, I believe that frequency response matters most, then ringing. But ringing is still very important. Obviously it depends on how much there is. And how badly skewed the response is too, for that aspect of degradation.

I also don't follow about your measurements graphs and files. Are you now saying that the file you sent me is not what you posted graphs from? I wasn't aware that you'd prefer to correspond by email, and I didn't think I was being rude by continuing the discussion here. From my perspective, your email was simply to send me the file so I could look at it and format it in a way that makes sense to me.

I really don't understand why this has to be so confrontational. Aren't we both on the same side, wanting to know what are the problems, how best to fix them, and whether or not our theories are correct? That's certainly been my goal.

--Ethan

 

[dallasjustice]

Michael, I'm trying hard to follow what you said. You sent me a paper to make a point, but now you say it agrees with me. Actually, I believe that frequency response matters most, then ringing. But ringing is still very important. Obviously it depends on how much there is. And how badly skewed the response is too, for that aspect of degradation.

I also don't follow about your measurements graphs and files. Are you now saying that the file you sent me is not what you posted graphs from? I wasn't aware that you'd prefer to correspond by email, and I didn't think I was being rude by continuing the discussion here. From my perspective, your email was simply to send me the file so I could look at it and format it in a way that makes sense to me.

I really don't understand why this has to be so confrontational. Aren't we both on the same side, wanting to know what are the problems, how best to fix them, and whether or not our theories are correct? That's certainly been my goal.

--Ethan

Ethan,
There's no doubt we are on the same side. You have been helpful to countless folks who are trying to do the same.

Amir asked me a while ago to write up a forum post on how I use Acourate to setup a multi subwoofer array for stereo playback, like the one I've attempted to describe in your thread. I will do that write up soon. I use REW for limited functions like the RTA, but I've grown much more accustomed to using Acourate measurement toolbox for interpreting acoustic measurements, as it's more geared to using appropriate digital filters to improve small room acoustics with multi-channel setups.

I am not someone who believes DSP can fix everything and I agree with you that decay times matter very much. In my next thread I start, I won't be using waterfalls. Instead I prefer to use unsmoothed Step Response and Stockwell Transform to describe improvements in decay. I know many folks feel comfortable with the wonderful REW software, but it is inconvenient, or impossible, to use when one is taking measurements in a complex multi-channel array and there's unusual latency from FIR filters. Acourate is more well suited to help describe such systems, IME.

Michael.

 

[Ethan Winer]

Well okay then. I wish this forum had a thumbs-up smiley.

I'm not about to spend $300 for Acourate so I'll have no way to assess whatever proof you might post that multiple subs can reduce modal decay times. Too bad you're so far away from me, I'm sure we'd have fun together playing around with your audio toys.

 

[dallasjustice]

Well okay then. I wish this forum had a thumbs-up smiley.

I'm not about to spend $300 for Acourate so I'll have no way to assess whatever proof you might post that multiple subs can reduce modal decay times. Too bad you're so far away from me, I'm sure we'd have fun together playing around with your audio toys.

I agree. It's hard to find like mind geeks in the area. Whenever I have friends over, I try not to talk about the room and the setup. I just want folks to listen. That's what it's all about. I find that it can be overwhelming for most people to describe everything all at one time. I can't tell you how many times someone has come into my room and asked me whether my room treatments were the speakers.

Since we are now agreeing with each other a little bit, I'll mention that I personally agree with you about treating lateral first reflections. I prefer accuracy over all else and I've found that appropriate lateral absorption to be very helpful in that regard.

 

[Fitzcaraldo215]

I thought the two of you and others might be interested in this. It is not directly on topic, but I just got my June Stereophile. In it is an article by Bob Katz on messing with his room acoustics using new PSI Audio AVAA C20 active bass traps, his existing Real Traps Mondos, and Acourate. He decided that peaceful coexistence between the three, plus a few more passive treatments, was optimal. It does not deal with modal ringing or multi subs much, but it is interesting nonetheless.

It might take a few months before it appears for free on the web.

 

[Purité Audio]

That is interesting, we are going to represent PSI I am keen to try those active traps.
Keith.

 

[Thomas savage]

That is interesting, we are going to represent PSI I am keen to try those active traps.
Keith.

They look promising but at £2000 each I might just stick to opening a window.

 

[AJ Soundfield]

In it is an article by Bob Katz on messing with his room acoustics using new PSI Audio AVAA C20 active bass traps, his existing Real Traps Mondos, and Acourate. He decided that peaceful coexistence between the three, plus a few more passive treatments, was optimal.

The mastering engineer? Is this at home or his studio?

 

[AJ Soundfield]

They look promising but at £2000 each I might just stick to opening a window.

Or get 2 active subs, maybe gradients and keep the room looking un-institutionalized. YMMV.

 

[Thomas savage]

Or get 2 active subs, maybe gradients and keep the room looking un-institutionalized. YMMV.

Good idea but my mental health out patient liaison officer might object.

 

[AJ Soundfield]

Subs or treatment little Thomas?