CR Treatment and Tuning---The home stretch!!

[mysticmonk]

Hey Frank,

Looks great man !

QUESTION: Where did you get the molding material to make the rounded (semicircle) edges to your desk ?

[Stadank0]

Actually,

I just ripped a standard coat hangar pole in half..In my case it was a 1 5/8" dia...hanging around the lumber yard, no pun intended!

[Stadank0]

Keyboard tray!!

20181208_152827.jpg

[Stadank0]

Got a hold up on the CR tuning...gonna try to switch to LR treatment for a bit. Just gotta get some plans.....

[Soundman2020]

Got a hold up on the CR tuning...

Yup. We ran into a very strange issue with the sub, where the input gain control on the sub itself appears to affect only part of the spectrum: it does not reduce all frequencies the same way. Frank has contacted the manufacturer to see if there is a work-around, and we are working on a "plan B" using another device to control the sub level externally, but it won't arrive for several days.... So in the meantime, we are "on hold" with the CR tuning...

But do stay tuned if you are following this thread! We should be back on track with that by next week.

In the meantime, here's some tantalizing hints of where we are in the final precision tuning process right now, as reported by REW.

First, frequency response, from 11 Hz to 500 Hz, smoothed to 1/6 octave:

FRANK--REW--FR--11-500--1..6--DTv059.png

Yes, that graph really does start at 11 Hz, and yes, the response really is flat down to 16 Hz. ... And yes, the frequency response of the entire low end really is within +/- 1.5 dB at 1/6 octave smoothing! (and if you really must know, it is still within +/-3 dB UNSMOOTHED , but we aren't quite ready to show that graph yet...., until the process is complete... )

I'm fairly pleased with the results so far, in terms of frequency response. I think Frank is, too.

Now for the waterfall, smoothed to 1/3 octave:

FRANK--REW--WF--10-1k--1..3--DTv059.png

This time it goes all the way from 10 Hz up to 1 kHz. In other words, half of the entire audio spectrum. I think you could say that this is pretty smooth....

Frank reports that the low end is very tight, very clean, and very smooth... but we ain't done yet! There's still a few minor details that we are working on, before we show the final results at higher resolution.

Now, do bear in mind that some studio designers only ever show their results at 1/3 octave, claiming that "this is what the specifications require", and they flat refuse to show their results at higher resolution... I wonder why? Compared to what they show, I think this is pretty decent... And some other designers refuse to show their results AT ALL! Claiming that the client won't let them, or whatever. But in my experience, when you get results this good, the client is damn EAGER to show the results in public, in order to attract business for his amazing studio! But whatever... I'm not the kind of guy to hide the results of the rooms I design, so you will be seeing higher resolution of these graphs, once the process is completed. And I'm pretty sure that Frank is proud to show off such amazing results from his very hard work, and very careful construction, with great attention to detail. It's only thanks to that, that we can get such flat response: it isn't possible to get this type of graph from haphazard building. See my signature block at the end of every post, to understand why...

And do bear in mind that this is a very small room: Total floor area is a tad over 144 square feet (14.4 m2), and total room volume is 1380 cubic feet (39.1 m3). That's just 67% of the smallest recommended size for a critical listening room. It goes to show what can be accomplished with careful design and careful construction.

I'm not saying that to "blow my own horn", as the saying goes, but rather to encourage others with small spaces that it is possible to achieve decent results. That said, I would NOT encourage you to shrink a room that COULD be larger: it's always best to make the room as large as possible. It's not simple at all to get these results, so unless you have a good understanding of acoustics, don't try to make your room this small, if it can be larger. keep it above 180 ft2, at least, and over 220 wherever possible.

I should also point out that these graphs do not show the final "house curve" that I will be applying right at the end. Right now our aim is to get the response as close to flat as we can, then we'll apply the house curve that I have developed, which is based on the famous B&K curve from several decades back, with some modifications suggested by Floyd Toole in some of his papers and books, based on decades of research into the way people perceive sound, speakers, and room acoustics. So for now you are seeing only flat, but that will be livened up a bit with the final tweaks.

There will be more graphs, and in greater resolution, once we are done, along with more detailed descriptions, and Frank will add his own comments on the final outcome, as an experienced mix engineer, but for now at least I did want to post this update. Just in time for Christmas!


- Stuart -

[Gregwor]

We ran into a very strange issue with the sub, where the input gain control on the sub itself appears to affect only part of the spectrum: it does not reduce all frequencies the same way.

Is this due to a faulty unit or how the sub was designed? The specs and reviews of this sub are amazing, so I'd hope this is a faulty unit or that there is indeed a fix. I hope one day to own one!

Greg

[Stadank0]

Hey Greg,

As of yet, I don't know....My sweetwater guy is going to put in a message to Neumann, but I don't expect a reply until after the holidays...I haven't run this by Stuart yet, but the idea got floated that it might be the prm-1 mic...

What do you think Stuart?

I can say that this sub is AMAZING!!! I can live with this issue by adding a filter to cut just above 20hz if need be...You won't be disappointed.

[Soundman2020]

.I haven't run this by Stuart yet, but the idea got floated that it might be the prm-1 mic...

I don't see how that could be the case at all. If the mic was faulty and did not have flat response, then we would have seen that already, in the other tests, both with and without the Tannoy subs, and the Dynaudio sub.

Also, we can reduce that level very easily with the "magic wand"... ( ), along with all the other levels, and the mic shows those changes... it's really hard to see how the PRM1 would be able to do that selectively! Besides, you pulled the input gain level down by about 10 dB, I think, and the 20 Hz area didn't budge at all: if it was a mic problem, then the 20 Hz region would have dropped as well, just staying above the rest. Mics are not selective like that: the response curve is more or less fixed, and doesn't vary much by SPL, except at very high levels. 90 dBC is not a very high level for that mic: it can take 132 dB, according to the specs!

I find it very hard to believe that it is the mic! But if you want to check that theory, then just plug in any old mic in its place, and repeat the same tests we already did. The curves will be different, of course, but the overall behavior will reveal if the PRM1 has a problem or not. Even a good old SM-58 would do just fine as a sanity check for this.

The other issue I was thinking is that it could be some type of strange resonance in "something", but that seems very unlikely too: it isn't a mode (your room doesn't have any modes that low), but it might be something vibrating or resonating on / around / in / under the desk... however, it doesn't behave like that either: the level decays normally, and the decay isn't that long anyway. I think you would have noticed if something in the desk was vibrating wildly at 20 Hz.

The other possibility is that it is ringing that I have induced somehow... but it doesn't behave like that either! We could check that theory by using the Tannoys one last time: Just sit them down close to where the KH805 is, and plug them in instead of the 805, then run a test like that. They don't really go down that low, but they do still put out enough energy down there that the effect should be evident. Turn them up until things are almost clipping, and see what you get. Then turn them down, and see if 20 Hz goes down like the rest of the low end.

- Stuart -

[Soundman2020]

... continued...

Frank, I just sent you a test you can try, to see if it might be related to the mic. Let me know how that goes.


- Stuart -

[Jakob De Wittig]

Wow Guys !!

Amazing results. The newest graphs are insane Really impressed! and man that desk is gorgeous

//Jakob

[Stadank0]

Thanks for the praise! The acknowledgement means a lot to me....

The sound quality that we've achieved here, by far exceeded my expectations. When I started treating this room, I was not optimistic. It sounded horrible and the odds seemed to be against us with the room dimensions being what they are. Of course I'll have to see how my mixes translate in the real world, but I'm very confidant that I'll be able to measure up to a very high bar.

In this case, digital tuning was critical. The room definitely can't stand on its own in the +/-5 db domain, due to the its size and dimensions. Its all about making conditions suitable for digital tuning by addressing time alignment(phase and decay) as well as reflection issues(impulse response). I'm paraphrasing Stuart here a bit, but I certainly share his views now.

The clarity and the balance are quite remarkable.

[Soundman2020]

Thanks for the comment, Jakob! As soon as Frank's place is completed, yours is next on the schedule! Your place has it's own unique challenges, but I'm confident the final outcome can be very similar to Frank's place.

And I'm really glad that Frank agreed to try the digital tuning process! As everyone can see, it is fundamental to getting the overall response tightly under control. However, as Frank mentioned, this can ONLY be done in a room that has been treated as completely as possible acoustically: It CANNOT be done in an empty untreated room, or even a badly treated room, despite the feverish hype spewed excitedly by the manufacturers of so-called "room tuning" hardware and software.

I think Frank was a bit skeptical when I first told him about that ("room correction doesn't work: only digital tuning does"), before we started on the digital tuning path, but I'm pretty sure he is now totally convinced, since he has seen how the process actually works in reality. No algorithm can tune the response like this, because algorithms do not have a pair of ears and a brain! Algorithms do not actually understand what "sound" means: they only understand amplitude and frequency, but they have no concept of "musicality", or "tightness" or "clarity" or "harshness" or "timbre" or "warmth". Those are subjective terms that only actual human beings can appreciate, and cannot be programmed into a software algorithm or piece of hardware. This is why I am not in the least a fan of "room correction" gear, and why I don't even use the term myself: firstly, you cannot "correct" the room with hardware or software, and secondly, even if you could, it would still fail. I prefer the term "digital tuning", because that's what we are actually doing here: applying digital tuning to compensate for some issues in the signal chain. That's all. We are not attempting to "correct the room"! If we did, we would fail. The ONLY way to actually "correct" a room, is with extensive acoustic treatment. You cannot correct it with "room correction" software or hardware. And when it has been corrected as well as possible with acoustic treatment, only then can digital tuning be applied, as the "cherry on top of the cake".

You can't put the cherry on top of the cake when you didn't even bake the cake yet, and all you have is raw ingredients sitting in a bowl!

OK, [RANT-MODE = OFF]!

And for those who are following the thread: Yesterday Frank and I managed to prove, conclusively, that the issue we are seeing with the sub is NOT related to the PRM1 mic (which is a great acoustic test mic), nor is it related to anything else in the signal chain. We can control the low-end levels from other places in the signal chain, and the results are as expected. It's only the "input gain" control on the sub itself that does not work as expected. So we'll wait for word from the distributor and manufacturer on that. It's a great sub! Not in question. And if the manufacturer can't fix it, I'd still suggest to Frank that we keep it anyway, simply because it is awesome: I can work around that defect in other ways.

OK, now I better shut up and get back to working on the final treatment devices for Frank's Live Room, or he'll start thinking that I'm wasting time!

- Stuart -

[Stadank0]

Always up to no good, that Stuart!! Chatting it up on the internet!!!


Oh, and I will definitely be keeping that sub!

[mysticmonk]

Looks good !!

[mysticmonk]

Yikes !!! Sorry man, I thought that I sent a PM to Stuart and didn't realize I was posting this on your thread !!!

BTW, I wasn't bitching at all. Stuart is AWESOME and I definitely have no complaints ! I was just trying to copy some quotes from your thread and send them in a PM to him, but somehow what I intended as a PM got posted as a reply here.

My mistake.

And 4+ years for building an entire studio from the ground up (including BOTH a CR and a live room) is not too bad IMO.