erfahrungen mit regien mit FTB-akustik?

[Northward]

thanks for providing very interesting views!
your explanation describes how FTB rooms (or the used mechanisms) work, but i still don't see the difference (in the low frequency area) compared to a rectangular room.

let me ask my question from a different viewing angle:
what is the motivation of all the mechanisms you described in the low frequency area?
- very low reverberation time
- defined distribution of the room modes

lets say i design a very simple rectangular room with a defined distribution of the room modes & by having very thick walls full of rockwool having a performance down to 20hz. wouldn't that give me a compareable performance in the low frequency area?

i hope you don't find my questions offending, but we have a quite acoustic-interested community here, so its nice to have you as an expert here & we are allowed to ask you some questions in order to better understand the FTB-approach (and the differences to other designs). of course, we understand, if you can not provide too much details of the design.

No, not offending at all! I find this forum very nice.

The point is how to optimize the room in size, performance and cost.

Of course we could build a rectangular room and likely make it work to FTB standard. But if I do so, then expect backwall trap AND side walls traps AND ceiling traps to be no less than 120-150cm deep. Loaded with membranes and various other pretty expensive systems. And still, way down in LF, I will likely get some trouble. Even the larger anechoic chambers are no good under 60Hz. Some no good from under 100Hz, surprisingly.

Basically I'd have to really "over build" a rectangular room if I am to meet the same response I get by controling LF dispersion with the help of geometry, focusing it and treating it efficicently where optimum (the massive back wall trap). Thus likely getting in fact a better response (better control of modal response) using less materials, less floor area, .... less money.
With a geometry involved, the side wall treatment is reduced on average to 40-50cm thickness. And I get better results + vastly optimized the efficiency per area of treatment.

If you look carefully, most of the FTB are in fact half a rectangle (roughly the rear half of the room), half a shaped room (roughly the front half of the room). This should give you a hint as to how all this functions.

Our approach here is to optmize our model on basically all counts. With the current state of the recording industry, there is no room for unjustified costs. So, technically and commercially, this is an edge if you want to get work as a studio designer. A down side is that the model leaves very little room to play with.

Design by function.

Hope this is clearer.

 

[karumba]

The point is how to optimize the room in size, performance and cost.

Of course we could build a rectangular room and likely make it work to FTB standard. But if I do so, then expect backwall trap AND side walls traps AND ceiling traps to be no less than 120-150cm deep. Loaded with membranes and various other pretty expensive systems. And still, way down in LF, I will likely get some trouble. Even the larger anechoic chambers are no good under 60Hz. Some no good from under 100Hz, surprisingly.

ok, i see the point. but if performance vs. cost needs to be optimized, what is the reason you don't simply use helmholtz resonators in your designs?

ok, anechoic chambers are a differen topic, but for an FTB room you would like to have a reverberation time of lets say 150ms. i don't have experience with rooms having 150ms or less in the low frequency area, but aiming for 250-300ms the effort isn't very big in my experience.

 

[Northward]

The point is how to optimize the room in size, performance and cost.

Of course we could build a rectangular room and likely make it work to FTB standard. But if I do so, then expect backwall trap AND side walls traps AND ceiling traps to be no less than 120-150cm deep. Loaded with membranes and various other pretty expensive systems. And still, way down in LF, I will likely get some trouble. Even the larger anechoic chambers are no good under 60Hz. Some no good from under 100Hz, surprisingly.

ok, i see the point. but if performance vs. cost needs to be optimized, what is the reason you don't simply use helmholtz resonators in your designs?

ok, anechoic chambers are a differen topic, but for an FTB room you would like to have a reverberation time of lets say 150ms. i don't have experience with rooms having 150ms or less in the low frequency area, but aiming for 250-300ms the effort isn't very big in my experience.

If you want my honest opinion, Helmholtz are completely useless in a control room. They are either somehow effective and too narrow band and thus only take care of a narrow bandwidth while we need a full broadband treatment (and always need re-tuning on site, as the equation is somewhat not quite right in real life due to other factors that it doesn't take in account) or they are wider Q and hence, basically not even near effective enough for the use.

The point is that you need full bandwidth treatment. 20Hz to 20kHZ. Not a single frequency can stand out, even if just "longer in time" than another with no other side effect. Helmholtz, even combined with other treatment simply won't get you there. there will be gaps in treatment efficiency, areas where they feeback etc.

For example, if you treat a problematic 80-90Hz, then all the other frequencies will remain "long". Not good. You'd also need to vary the treatment very locally and very often. Which would turn out to be very difficult, expensive and very time consuming as there is no way you will get it right the first time (or second or third), for a likely mediocre result.

For that we use wideband membranes that cover a large area with other type of treatment in front of it that basically are arranged like a speaker filter, overlapping "just right". And that is way more effective, at least in our opinion. Works every time on the first trial.

Control rooms don't have a reverb time as there is no statistically diffused field. So that notion is out the window. Hence the number you get with most software probably isn't reliable enough to be taken seriously in these circumstances.

Maybe a filtered ETC dropping 60dB in 300ms in the LF is effortless (but it also is a sign of a likely too long bass and thus often means problems remain unless the room is very big, or at least in my experience, bass that could have a better definition/articulation.), but 80ms to 100ms in a small to medium sized room in the whole spectrum 20Hz-20kHz is no easy task. These are by all means very short rooms. Our show room / Control Room has an inner- shell of 57m² for a net surface of 42m², and a drop in the LF of 60dB in under 150ms. So for a quite big room, it is very short.

FTB are aiming at a Non-Environment type of response for speaker to room and speaker to engineer. 300ms won't cut it, it's way too long. This is the type of length you'd get in a LEDE or RFZ. Which are fine, but too long for what we're aiming at here, NE.

So as short a decay as you can possibly get speaker to room, full bandwidth 20Hz-20kHz.

For that, we forget Helmholtz. In a live room they can be used to tame a frequency. but as far as I'm concerned, it stops there.

Today you have the DEAMP system for example that is on all counts way more efficient, reliable, cheaper and flexible than a Helmholtz, so I'd likely go for that if I need such type of treatment. In fact we are currently using them on a project in a live room, they work great.

I am fully aware that others may have different opinions, and I don't have a problem with that. But I hope this helps at least a bit to uncover some of the issues met while designing a Control Room.

 

[karumba]

i think it is good to remain the discussion in english, so thomas could participate, which i really appreciate!

as you know, we visited steffen müller end of june who was a great host & is a nice person to have interesting conversations with (we were much longer there than we expected). so, i would like to thank him for being kind to let us see & hear his room - thanks steffen!

i needed some time to sort out my thoughts a bit, but now some impressions from my side which are of course my very own personal (!) view:
at first, this room is & feels very dry. i've heard some also very good sounding mastering rooms, but none of them are as dry as this room. it feels like it couldn't be much more dry. the frequency response of the room is very even over the whole frequency spectrum, which is of course not very surprising given the effort put into that room resulting in a evenly distributed low reverberation time. the room is also very quiet. i also experienced the effect which i called "acoustical vacuum" before. of course, this is less pronounced than if the room would have been fully absorbtive, but it is there. i have to admit, that it doesn't suit my taste and i just like rooms which are a bit more live, esp. for mastering due to that reason. this also confirms why i made my room more live over the years, since my first rooms where also very dry, but due to lack of acoustical knowledge & of course by far not having the quality of steffens room!

maybe my comments are a bit "suprising critical", but please don't get me wrong. this room is of very very high acoustical quality, it is more the concept which doesn't convince me. some months ago i had a totally different opinion of FTB rooms. i initially thought this is *the* perfect room design & i wanted to have it my own. i don't know, but maybe this impression came from the well known room build threads we all know & appreciate - they just look like the perfect room. now i know, that this would have been the wrong direction for me. i've realized, that there isn't *the* perfect room design, there is just a room design that fits to *you* or not. considered with distance this is not very surprising, since this is not very different from what we have with speakers.

i hope my post is not too direct, it is absolutely not meant to offend thomas or steffen, but since there is anyway not much criticism on FTB rooms & thomas is heavily booked, i think its fine to put this at least a bit into a different perspective especially since others enjoy these type of rooms. i just would like to encourage everyone playing with the idea of getting such a room to book a day in such a room and work in it in order to find out if it is the right thing for you - this also isn't something new, isn't it? i'm sure steffen did that, since he his very very happy with his room and i'm sure he is doing a very good mastering job - thanks again!

 

[Northward]

Everyone is entitled to an opinion

Not everyone has to like our rooms (that would be weird) and certainly the approach of "try before you buy" you mention is one we require from every client before anything happens. That's why we have a large studio they can come and visit/try and we arrange that they visit at least a couple more rooms after that - those they chose to (we sent quite a few people to Steffen's room). Then we debrief which they preferred and why, so we know where to go looks and feel wise.

I think you very much need need to visit more than one to form an opinion though

The deadness comment is not one I get often at all, but the quietness one is one that I do get often - especially in floating rooms. I don't remember anyone I brought to Steffen's room commenting on the fact that it was dead though. I guess it's a sliding scale... Or taste, like you rightly mention.

Some people are very sensitive to low noise floors, and feel this "vacuum" you mention, in fact primarily due to the very low noise floor. It is experienced only by a % of the population as a form of weird pressure in the ears.

Steffen's room is on the deader side for a FTB, but not a dead room. A very quiet room, yes.

The Noisia rooms are very quiet too for example. But no comment on any deadness.

You're most welcomed to visit more! I can arrange that

Thanks for taking the time to visit Steffen. He IS a fantastic guy.