John Sayers' Recording Studio Design Forum Archive

Just a quick progress update.

Been slowly progressing over the last week. Spent 6-7hrs varnishing and staining the pine slats on saturday. Had spent a fair bit of time during the week rounding off all the edges with a handplane and sandpaper. Framing the back soffit: sealing up the box for the combo QRD hermholtz style bass trap: Then some insulation: Then finally got the whole wall stuffed and managed to get one slat fitted: Slats should go up quickly now.

Hi Big Fry,

They are some good looking slats!

I also considered the MyRoom concept, but switched in favour of RFZ with some strategically placed diffusing elements. I was put off mainly by a lack of lab data regarding the diffusing capabilities of the design. A similar concept was mentioned in an acoustics book (I can't remeber which one) and it seemed to peak with a diffusion coefficient of about 0.2, which is not great. The DIY stepped array of 5 LeanFuser panels for example, has a theoretical diffusion coefficient of about 0.4 from 600Hz up.

I would love some lab measured data for the MyRoom design concept though.

Hopefully you won't have many issues, but you may find some strong specular reflections cause comb-filtering at the mix position. It's generally recommended to stick to absorption/ redirection on your rear wall if you don't have much distance between your head and the rear wall.

Have you taken any REW measurements yet in your build? It would be great to track your progress.

Dan

Got a little bit more done on the back wall over the last couple of days I have been doing a few acoustic tests by ear in there over the last few days just to see how things are starting to come together. Was panicking over a really nasty 1.6k resonance for 3 minutes until I realized that it was the aluminium ladder that was in the corner, not the room hahaha.

Waka wrote:Hi Big Fry,

They are some good looking slats!

I also considered the MyRoom concept, but switched in favour of RFZ with some strategically placed diffusing elements. I was put off mainly by a lack of lab data regarding the diffusing capabilities of the design. A similar concept was mentioned in an acoustics book (I can't remeber which one) and it seemed to peak with a diffusion coefficient of about 0.2, which is not great. The DIY stepped array of 5 LeanFuser panels for example, has a theoretical diffusion coefficient of about 0.4 from 600Hz up.

I would love some lab measured data for the MyRoom design concept though.

Hopefully you won't have many issues, but you may find some strong specular reflections cause comb-filtering at the mix position. It's generally recommended to stick to absorption/ redirection on your rear wall if you don't have much distance between your head and the rear wall.

Have you taken any REW measurements yet in your build? It would be great to track your progress.

Dan

Thanks for stopping by Dan!

I haven't taken any measurements yet as my studio computer needs a bit of work so I need to track down a usb audio interface and just setup REW on another laptop. That's not a bad idea though, see if I can make it happen this weekend.

I know I took a gamble with the QRD on the back wall as there's not a ton of distance between my ears and the QRD. There are a few reasons why I'm risking it which I'll outline here so good or bad we can post-mortem it and hopefully encourage or discourage someone from doing the same.

1. I've spent quite a bit of time sitting in front of, recording and mixing in front of QRD's in smallish rooms and I've never noticed the comb filtering unless I stuck my head right up to the diffusor. I know theoretically it can be a problem, but in practice I haven't encountered it.

2. I really like what diffusion does for the sound of a room and I really dislike the sound of over absorbed mid-highs in a room. The room is small so any non-damaging reflections I can keep to extend the decay and make the room sound larger, I'm happy for.

3. There is a side-effect of QRD's that seem to add smoothing to the freq response of a room.

4. This room is multipurpose and a compromise. I would like to be able to mix and trust what I hear, but the number one priority is a comfortable place for my wife to be able to quickly edit radio breaks. Secondary, but still important priorities are recording my wife's voice-overs and radio shows. After that I'd be able to write music, record acoustic guitars, vocals, violins, percussion and of course mix in here. If necessary my wife can use a reflection filter behind the mic if it's too bright/reflective.

Now I'm having a bat each way here, because that diffusor is not a pure QRD. The slats are 30mm wide and the slots 8mm. This works out to 26.66% absorption to reflection and on top of this I have rounded off the corners on the front of the slats to minimize refraction.

This room is not a MyRoom design, I just stole from that concept for this particular diffusor and also the desire to keep the room bright and alive using slat/slot walls/ceilings.

Nice looking work. I don't know if I am misreading but I don't think diffusors can deliver a specular reflection, thus creating comb filtering.
I am pretty sure the White Papers on MyRoom and MR V2 have measurements, although not from Labs obviously.

DanDan wrote:I don't know if I am misreading but I don't think diffusors can deliver a specular reflection, thus creating comb filtering.

Doesn't it depend on the effectiveness of the diffuser? A shallow diffuser, for example, that is only effective at high frequencies will act similarly to a flat surface for the frequencies beneath it's effective range. Therefore, logically, the lower frequencies will not be diffuse and liable to comb filtering effects, would you agree?

I have copies of the white papers, and they do have have measurements in, that I have no doubt are reliable. But without lab tests, how do we know the actual diffusive capabilities of a device with open wells?

I also find it unusual that there were few studios I could find in almost a decade that had implemented the concept. Aside from Boggy's own ofcourse.

I think Boggy was a great guy, very open with his work, and seemed very humble.

I just wish the diffusers themselves had lab data to show their effectiveness, or at least if they could be modeled in diffusion software to get theoretical values. I had the trial of AFMG Reflex, but couldn't find a way to model the diffuser with open wells and absorption behind, if you know of a program that does this, please let me know!

I would love for these devices to be able to be modeled for specific frequencies and know they will work as intended.

Dan

Waka wrote: Doesn't it depend on the effectiveness of the diffuser? A shallow diffuser, for example, that is only effective at high frequencies will act similarly to a flat surface for the frequencies beneath it's effective range. Therefore, logically, the lower frequencies will not be diffuse and liable to comb filtering effects, would you agree?
Dan

In some sense I think of the QRD with gaps instead of fins as a kind of acoustical crossover. When you make the gaps wider, many things are occurring:
- increasing the ratio of of absorption to reflection
- increasing the frequency upwards at of the hermholz functionality
- making the hermholz effect more wide-band

My diffuser is 8mm gaps, 30mm slats (27% absorption) - much wider slats than what Boggy had used. It's an experiment for sure, so I'm looking forward to testing it out.

Little more progress...
Always nice to hear the acoustics of a room clean up as you build.

New monitors turned up this week These are passive BM6's that I'm planning to soffit mount. They are heavy suckers. Haven't had the chance to test them properly yet as I'm waiting on an amp to get shipped. Looking forward to rigging them up. They are rear ported so I'm trying to work out whether I should buy a plug for the port or just allow it to radiate into the soffit. I'm leaning towards plugging at the moment so that the box reacts more like a sealed enclosure.

More progress last week.

Feature downlights in for the back wall: Then starting on layout and framing for the front soffits: Using hardwood studs to keep the soffit wall as stiff as I can make it.

Bout time I did a bit of a progress photo dump as I'm in now in the final stages of finishing this build.

Sizing up the soffits: Stuffing: monitor mounts test fit of soffit face:

soffit stuffing: Fitting up soffit faces: Ceiling: Finished soffits with racks: Some initial testing: The back wall soffit was acoustically acting more like a solid wall so I had to remount all the slats with bigger gaps to fix a bass trapping issue: Building the desk/worksurface: Desk in place:

Starting to wire up the patchbay: desk supports: floor going down: Wife already working away in the space: Test fit of the guitars: This is the rubber profile that the door will be airsealed against:
Still plenty of work to do, but it's now functional for my wife and cleaned up. Will post some more pics when I get more finished.